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Item Measurement of Lateral Distribution of Cosmic Rays Muons Using Two-Fold Coincidence Technique(Kenyatta University, 2024-09) Kihagi, Veronicah NyamburaCharged primary cosmic ray particles constitute 85% protons, 12% helium, 3% iron, and heavier elements. These primary particles interact with the Earth's atmosphere, producing secondary particles known as Extensive Air Showers (EAS). Among the particles produced in EAS are pions and kaons, which subsequently decay into muons. Cosmic ray muons dominate the population of cosmic ray particles on the Earth's surface. Understanding the properties of EAS in the Earth's atmosphere is the aim of this investigation. The lateral distribution of cosmic ray muons was investigated using two-fold coincidences. Four detectors were positioned at two-fold coincidence separated from 0 to 35.5 meters at regular intervals. It was determined what the coincidence rate was between these detector stations. The data that was collected was fitted using the Nishimura-Kamata-Greisen (NKG) function in order to examine the lateral distribution The results showed that the muon flux decreased with increasing distance. Additionally, the study aimed to explore the hourly variation of cosmic ray muon flux. To achieve this, two detectors were used in coincidence to measure the variation over time. The highest muon flux was observed sometime after midmorning and lowest sometime after sunset. To support the understanding of EAS, Monte Carlo (MC) simulations of EAS were performed using the EPOS and GHEISHA models, which account for high and low-energy particle interactions, respectively. The simulations using EPOS LHC from this work with the measurements of the two-fold coincidence gave a primary composition cosmic ray as (protons (81±0.01) %, helium (10±0.04) %, and (9±5.88) % iron, and heavier elements). The EPOS LHC simulations were then compared to the experimental data and the muon count rate was found to align with the expected one. The knowledge gained from the lateral distribution of cosmic ray muons is essential for comprehending the development of extensive air showers. Furthermore, this information enhances our understanding of the chemical composition of primary cosmic ray particles. In addition, we also understand the interactions of cosmic ray particles in the atmosphere, particle production and formation of EASItem Positron Impact Elastic Scattering of Magnesium Using the Distorted Wave Method(Kenyatta University, 2024-08) Onyancha, Elvick Motanya MarsA profound grasp of cross sections, encompassing both differential and integral aspects, regarding positron interactions with atoms and molecules, proves highly valuable in eluci dating the dynamics of microscopic particles and shedding light on atomic structures and intermolecular forces. This understanding plays a crucial role in various fields, including astrophysics, plasma physics, and laser advancements. Over the last thirty years, exper imental and theoretical findings have been documented concerning positron-magnesium elastic scattering. This thesis presents an extensive computational study of positron-impact elastic scattering of atomic magnesium in the framework of Distorted Wave Born Approx imation (DWBA). Differential cross sections as well as integral elastic cross sections have been calculated at incident energies between 10 eV and 200 eV where . In order to per form the aforementioned calculation, a computer program called DWBA1, designed for e −-H scattering, was adapted to accommodate the specific process being investigated. The obtained results are then compared with the available theoretical and experimental results for analysis. The current findings regarding integral cross sections demonstrate a favorable qualitative alignment with experimental and the majority of theoretical results. At interme diate incident energies (30-100 eV), the DCS derived from the present study demonstrate satisfactory concurrence with both calculated and experimental results. However, at lower incident energies (10-20 eV), the obtained differential cross sections (DCS) do not exhibit satisfactory agreement with the available measured and calculated outcomes. Thus, it is evident that the current method is applicable for the elastic scattering of positrons and magnesium atoms at intermediate energiesItem Lateral Distribution of Cosmic Ray Muons(Kenyatta University, 2025-10) Mburu, Samuel ChegeCosmic rays are high-energy particles that travel through space at nearly the speed of light. Primary cosmic rays originate from sources such as the sun, supernovae, black holes, and active galactic nuclei. When these primary cosmic rays interact with the Earth's atmosphere, they produce secondary cosmic rays, including cosmic ray muons, which are a significant component that reaches the Earth's surface. The lateral distribution of cosmic ray muons is a key factor in understanding the elemental composition of primary cosmic rays and the development of extensive air showers in the atmosphere. The aim of this work was to estimate the elemental composition and interaction of primary cosmic rays in the atmosphere. Two NaI(Tl) detectors and associated electronics were used to carry out the measurements. The detectors were separated at regular intervals ranging from 0 to 30 meters. Cosmic ray muons were detected by the NaI(Tl) detectors. For each detector separation, the number of coincident muons and the total number of detected muons were recorded at two-hour intervals. The experiment was conducted at Kenyatta University during the months of March, April, and May 2019.The data collected were analyzed, and a decoherence curve was plotted, showing the number of counts per minute as a function of the separation distance between the detectors. The coincidence rate was fitted using the Nishimura-Kamata-Greisen (NKG) function and compared with Monte Carlo (MC) simulations of extensive air showers. The simulation were based on the DPMJET-III model, and the simulated results agree well with experimental data. The analysis of the experimental data revealed a primary cosmic ray composition of (86 ± 3)% protons, (10 ± 31)% helium, and (4 ± 3)% iron. These results for protons and iron are consistent with other reported values, while the helium component shows some deviation. This work contributes to our understanding of the mass composition of primary cosmic rays and their interaction with the Earth's atmosphere.Item Roof-Top Solar PV Performance Under Different Roofing Materials and Air Gaps in Tropical Climates.(Kenyatta University, 2024-05) Aigbedion, Nosakhare JeremiahHigh temperatures negatively impacts the performance of Photovoltaic (PV) modules. This is more pronounced on Roof-top installations where due to limited air spaces and the choice of materials influence the natural cooling of PV modules. Regions experiencing high temperature conditions such as the tropical African countries present a unique opportunity to study the interactions between the PV module and the base roofing materials. This study presents both simulation and experimental results of the thermal effects of roofing materials and air gaps on the performance of rooftop-installed PV modules. Clay and concrete tile roofs as well as various metal roofs commonly used in sub-Saharan Africa were studied. The base material properties of the roofs were studied and the effects of roof pigmentations were examined as well. Pigmentations of Iron (III) oxide (Fe2O3), Titanium dioxide (TiO2) and Basalt which are three commonly used roof pigmentations were studied and compared with PV heat interactions of unpigmented roofs. For the simulation study, the PV module and the various roofs under investigation are designed on Solid Works software and model designs are then exported to ANSYS workbench where modeling and simulations are implemented on ANSYS steady-state thermal. The roof pigmentation study was implemented in COMSOL Multiphysics software for transient thermal analysis. Surface radiosity is investigated to further differentiate the heat transfer influence of the various pigments and to underline the environmental impact of each of the models. The results obtained are validated with field-based experiments carried out at Kenyatta University in Nairobi, Kenya. Six different commonly used roofs namely; Decra roofs, Box Iron roofs, Clay tile roofs, Concrete tile roofs, Orientile roofs, and Galvanized Iron roofing sheets were specifically investigated. PV installation optimization was investigated for the various roof materials and optimal air gaps for specific roof materials were determined, to guide future installations. Results from the study provide relative PV performance on the six different roof materials. Results from the study also show the role of roof pigmentations in PV heat transfer. The clay tile roofing sheet revealed minimal deleterious effects on PV installations, closely followed by the concrete roof tiles. Among all the metal roofs investigated, the Orientile roofing sheet requires larger clearance for better performance, followed by the Galvanized Iron roofing sheet and Decra. The PV module on the Box Iron roof recorded lower temperatures when compared to those on the other metal roofs at specific air gaps, consequently leading to higher performance. PV maximum temperature across the different modules on the various roofs ranged from 64 °C – 50 °C, at instantaneous times at the 20 mm airgap. This range difference decreased as air gaps were raised to 100 mm. Open circuit voltage values ranged from 20.8 V – 21.1 V as airgap increased on the best-performing module on the Clay roof. The modules on the other roofs also revealed voltage gains at higher air gaps. Results also reveal the optimum airgap for PV installations of Concrete, Clay and Box-Iron roofing sheet at 100 mm. while Orientile, Decra, and Galvanized Ion roof materials have optimum airgaps at 150 mm, 140 mm, and 140 mm, respectively. Further, out of the three roof pigments investigated, the Fe2O3 pigmented roof gives the highest solar cell temperature. The unpigmented roof reveals solar cell temperatures that are notably higher than the cell temperatures of all pigmented models. From the three pigmentations, the Fe2O3 pigment gives the highest surface radiosity. The unpigmented model displays a surface radiosity that is significantly higher than that of the pigmented models. This study establishes that the type of roofing material will influence the minimum air clearance necessary for the natural convective cooling of PV cells.Item Fabrication and Characterization of Zinc Oxide Nanostructured Natural Dye Sensitized Solar Cell(Kenyatta University, 2023-05) Nthiga, Njiru James Lincon; Migwi Charles; Wawire IsaacAbstractItem Electron Impact Elastic Scattering by Calcium Atom Using First Order Distorted Wave Method with a Complex Potential(Kenyatta University, 2023-06) Egesa, Waswa Vincent; P. K. Kariuki; E. O. JobungaAbstractItem Design of a Microcontroller Based Home Access System Using the Global System for Mobile Communication(Kenyatta University, 2023-04) Nyaga, Janeleah Wanja; M.K. Munji; R.L NyengeAbstractItem Natural Radionuclide concentration in Phosphate fertilisers found in Kenyan market(Kenyatta University, 2023-11) Mutwiri, Mbaka E; Nadir hashim and Naftally KimaniABSTRACT Human exposure to radiations from natural radionuclides is an inevitable aspect of life on earth. Cosmic sand radioactive materials are the two main sources of ionizing radiation on the earth's surface. Phosphate bearing rock, a material used to manufacture phosphate fertilizers, is known to contain relatively high content of uranium, thorium and potassium radionuclides. Continuous application of these phosphate fertilizers in our agricultural soils lead to contamination of our farming land with these radionuclides. Radiations from these radionuclides pose health risks such as cancer to the exposed individuals. Apart from the radionuclides, phosphate rock also contains traces of heavy metals such as cadmium (Cd) which is considered a big threat to human health. This research has analyzed the activity concentration of 238U, 232Th and 40K in various fertilizer types from three different brands sourced from Kenyan market. NaI(TI) detector and AAS were used for spectrometric analysis. The different types of fertilizers analyzed were; DAP, SSP, TSP, CAN and NPK (17:17:17). The radiological parameters; Radium equivalent, absorbed dose rate, external radiation hazard index, annual effective dose and excess lifetime cancer risk have been evaluated. The mean radium equivalent (Bq/kg) were 133±9 for DAP, 74±8 for CAN, 118±12 for SSP, 128±9 for TSP and 104±9 for NPK. The mean dose rate (nGy/h) were 69±5 for DAP, 37±4 for CAN 58±6 for SSP, 62±5 for TSP and 52±4 for NPK. The mean external radiation hazard index were in the range 0.20±0.03 to 0.36±0.04. The mean outdoor annual effective dose (mSvy1) were in the range 0.045±0.007 to 0.081±0.009. The mean excess life time cancer risk ranged from 0.157±0.010 to 0.283±0.020. DAP had the highest mean values while CAN had the lowest mean values for all the radiological parameters evaluated. The mean concentration of Cd ranged from 1.42±0.20 mg/kg to 11.13±0.48 mg/kg. The obtained results show that fertilizer samples are safe for use as cadmium levels and the radiological parameters assessed are below the maximum permissible limits of 60mg/kg for Cd concentration, 370 Bq/kg for radium equivalent, 60 nGy/h for dose rate,1 mSvy1 for annual effective dose and 0.29 x 10-3 for outdoor ELCRItem Design and Implementation of High Frequency Signal Generator Based on Phase Locked Loop(Kenyatta University, 2023) Mutinda, Boniface Musyoka; Mathew Munji; Raphael NyengeA signal generator is an electronic test instrument that has a wide range of applications.Some of these applications include testing systems in cellular communications, radar,microstrip antennas and testing components in electronics labs. For a signal generator to be used in these applications, it should generate high frequencies, have a low level of phase noise, and also have a fast locking time. The purpose of this research was to design and build a signal generator that operates on the principle of a phase-locked loop, has the capacity to generate frequencies ranging from 35 MHz to 3 GHz, and has a low degree of phase noise. The simulation of the phase-locked loop synthesizer was done using the ADIsimPLL design tool. The phase locked loop chip used in simulation was the ADF4351 from Analog Devices. In the design, we implemented a loop filter of the third order and chose a reference frequency of 10 MHz. The layout of the phase locked loop was simulated, and the results showed that the optimal values for loop bandwidth and phase margin were 10 kHz and 45°, respectively. Following the simulation, the optimal values for each of the loop filter’s components were analyzed and calculated. The signal generator was built by integrating the phase locked loop synthesizer and a keypad shield with an Arduino UNO microcontroller. The ADF4351 was programmed via Serial Peripheral Interface (SPI) to enable the changing of frequencies using the keypad shield. The nature of the generator’s signal was investigated using a cathode ray oscilloscope in the 35-100 MHz frequency range. The testing was also done for 101-3000 MHz using a spectrum analyser. The level of phase noise was calculated at 35 megahertz, 387 megahertz, 1 gigahertz, 2 gigahertz, and 2.9 gigahertz at 1, 10, 100, and 1000 kilohertz. The amount of phase noise that was acquired after experimental work was higher than the level obtained after simulation. For example, at the output frequency of 387 MHz, the experimental phase noise was -104.2 dBc/Hz while the simulated was -126 dBc/Hz at 100 kHz offset frequency. The reason for this is that the phase noise contribution in the simulation was only from the phase locked loop components while in the experimental, in addition to the phase noise from the PLL components, there were other sources of phase noise while carrying out the experiment. The rise in output frequency was also accompanied by an increase in phase noise. The reason for this is that the signal generator was built with the concept of a phase locked loop which implements the idea of frequency multiplication by dividing along the feedback loop with the use of a counter. This concept raised the phase noise by 20 multiplied by the logarithm of the number of counter. The maximum spur appeared at the third harmonic and was found to be -18.6 dBc, while the minimum spur appeared at the fourth harmonic and was found to be -44.5 dBc.Item Natural Radionuclide Concentrations in Phosphate Fertilizers Found in the Kenyan Market(Kenyatta University, 2023) Mbaka, Eric Mutwiri; Nadir Hashim; Naftali KimaniHuman exposure to radiations from natural radionuclides is an inevitable aspect of life on earth. Cosmic rays and radioactive materials are the two main sources of ionizing radiation on the earth’s surface. Phosphate bearing rock, a material used to manufacture phosphate fertilizers, is known to contain relatively high content of uranium, thorium and potassium radionuclides. Continuous application of these phosphate fertilizers in our agricultural soils lead to contamination of our farming land with these radionuclides. Radiations from these radionuclides pose health risks such as cancer to the exposed individuals. Apart from the radionuclides, phosphate rock also contains traces of heavy metals such as cadmium (Cd) which is considered a big threat to human health. This research has analyzed the activity concentration of 238U, 232Th and 40K in various fertilizer types from three different brands sourced from Kenyan market. NaI(Tl) detector and AAS were used for spectrometric analysis. The different types of fertilizers analyzed were; DAP, SSP, TSP, CAN and NPK (17:17:17). The radiological parameters; Radium equivalent, absorbed dose rate, external radiation hazard index, annual effective dose and excess lifetime cancer risk have been evaluated. The mean radium equivalent (Bq/kg) were 133±9 for DAP, 74±8 for CAN, 118±12 for SSP, 128±9 for TSP and 104±9 for NPK. The mean dose rate (nGy/h) were 69±5 for DAP, 37±4 for CAN 58±6 for SSP, 62±5 for TSP and 52±4 for NPK. The mean external radiation hazard index were in the range 0.20±0.03 to 0.36±0.04. The mean outdoor annual effective dose (mSvy-1) were in the range 0.045±0.007 to 0.081±0.009. The mean excess life time cancer risk ranged from 0.157±0.010 to 0.283±0.020. DAP had the highest mean values while CAN had the lowest mean values for all the radiological parameters evaluated. The mean concentration of Cd ranged from 1.42±0.20 mg/kg to 11.13±0.48 mg/kg. The obtained results show that fertilizer samples are safe for use as cadmium levels and the radiological parameters assessed are below the maximum permissible limits of 60mg/kg for Cd concentration, 370 Bq/kg for radium equivalent, 60 nGy/h for dose rate,1 mSvy-1 for annual effective dose and 0.29 x 10-3 for outdoor ELCR.Item Design and implementation of high frequency signal generator based on phase locked loop(Kenyatta university, 2023-11) Musyoka, Mutinda Boniface; Mathew MunjiA signal generator is an electronic test instrument that has a wide range of applications. Some of these applications include testing systems in cellular communications, radar, microstrip antennas and testing components in electronics labs. For a signal generator to be used in these applications, it should generate high frequencies, have a low level of phase noise, and also have a fast locking time. The purpose of this research was to designandbuildasignalgeneratorthatoperatesontheprincipleofaphase-lockedloop, has the capacity to generate frequencies ranging from 35 MHz to 3 GHz, and has a low degree of phase noise. The simulation of the phase-locked loop synthesizer was done using the ADIsimPLL design tool. The phase locked loop chip used in simulation was the ADF4351 from Analog Devices. In the design, we implemented a loop filter of the third order and chose a reference frequency of 10 MHz. The layout of the phase locked loop was simulated, and the results showed that the optimal values for loop bandwidth and phase margin were 10 kHz and 45°, respectively. Following the simulation, the optimal values for each of the loop filter’s components were analyzed and calculated. The signal generator was built by integrating the phase locked loop synthesizer and a keypad shield with an Arduino UNO microcontroller. The ADF4351 was programmed via Serial Peripheral Interface (SPI) to enable the changing of frequencies using the keypad shield. The nature of the generator’s signal was investigated using a cathode ray oscilloscope in the 35-100 MHz frequency range. The testing was also done for 101-3000MHzusingaspectrumanalyser. Thelevelofphasenoisewascalculatedat35 megahertz, 387 megahertz, 1 gigahertz, 2 gigahertz, and 2.9 gigahertz at 1, 10, 100, and 1000 kilohertz. The amount of phase noise that was acquired after experimental work washigherthanthelevelobtainedaftersimulation. Forexample,attheoutputfrequency of 387 MHz, the experimental phase noise was -104.2 dBc/Hz while the simulated was -126 dBc/Hz at 100 kHz offset frequency. The reason for this is that the phase noise contribution in the simulation was only from the phase locked loop components while in the experimental, in addition to the phase noise from the PLL components, there were other sources of phase noise while carrying out the experiment. The rise in output frequency was also accompanied by an increase in phase noise. The reason for this is that the signal generator was built with the concept of a phase locked loop which implements the idea of frequency multiplication by dividing along the feedback loop with the use of a counter. This concept raised the phase noise by 20 multiplied by the logarithm of the number of counter. The maximum spur appeared at the third harmonic and was found to be -18.6 dBc, while the minimum spur appeared at the fourth harmonic and was found to be -44.5 dBc.Item Levels of Natural Radionuclides in Khat (Catha Edulis) Leaves and Soils in Selected Areas in Embu County, Kenya(Kenyatta University, 2022) Ngari, Vindesio Njagi; Nadir Hashim; Abdallah MerengaEnvironmental data and information on levels of accumulation of radionuclides is crucial towards putting in place mitigation measures to ensure a safe environment. Over the past years, khat (Catha edulis) has been the major cash crop grown in some parts of the Eastern side of Kenya especially in Embu and Meru areas. The khat grown in Embu which is the study area is mainly the Muguka variety while the variety grown in Meru is the Miraa. The leaves from this plant are chewed for their stimulating effect. However, some studies have reported detrimental effects on the users of khat. In spite of its extensive use which extends to the Arabian Peninsula and the European markets, research on radionuclide concentrations in khat and in soils where it is grown has not been done. This therefore necessitated this research in order to provide public awareness on natural radiation levels. This research established the level of human exposure due to radiation by natural sources in the khat growing areas of Embu County by measuring the specific activities of 238U, 232Th and 40K, estimate the dose rate absorbed and obtain the hazard indices due to these radionuclides. Thirty samples were collected from different areas distributed throughout Embu County. The samples were then prepared and analyzed using the NaI(Tl) detector. The mean activities for khat leaves were obtained as 875.8±11, 10.1±1 and 51.1±4 Bq/kg for 40K, 238U and 232Th respectively. The activities of soil in the same region were however lower than the world average at 344±12, 22±11 and 33±5 Bq/kg for 40K, 238U and 232Th respectively. The mean absorbed dose rates obtained for soil was 44±0 nGyh-1 which is lower than the admissible dose standard of 1500 nGy/h. The AED for ingested radionuclides for khat had an average of 0.45±0.19 mSv/y. The average values of hazard indices for soil were 0.26, 0.32, 0.70 and 0.76 for external index, internal index, gamma index and ELCR respectively. All the indices in this work were within the safe. Results from this study therefore reveal that the khat grown in the Embu County poses no significant risk to the consumers and the general populace. The soils from the area are also safe for humans.Item Enhancement of Morphological and Opto-Electronic Properties of Perovskite (Ch3nh3pbi3) Thin Films for Solar Cell Applications.(Kenyatta University, 2022) Moracha, Daniel Juma; Walter Kamande Njoroge; FanuelMugwanga KehezeThe functionality of the photovoltaic devices greatly depends on the film morphology, which is determined by the deposition methods and annealing techniques. Organometal halide perovskite based solar cells represents an upcoming photovoltaic technology. Perovskites have been widely and extensively studied for some years now, but comprehending their properties has slowed down their advancement. Finding a link between their morphology and the resulting properties is important in dealing with some of the basic issues like high band gap and sheet resistivity that hinder further development of this solar cell. Herein the perovskite thin films were prepared by single and double step deposition methods. Concentrations of solutions, annealing temperatures and dipping time were used as parameters to form different morphologies during self-assembly processes. The optical band gaps for the films prepared by single step were observed to decrease from 2.10eV to 1.96eV when the annealing temperature was increased from 80oC to 160oC. An increase of annealing temperature beyond 160oC led to the formation of yellowish substance on the substrate, this indicated the presence of lead iodide. Further these results implied the decomposition of methyl ammonium which resulted to an increase of the optical band gap to 2.16eV. Films that were deposited by double step displayed similar trend where the optical band gap was observed to decrease significantly from 2.14eV to 1.95eV when the dipping time was varied from 2 hours to 8 hours. The optical band gap was observed to increase to 2.15eV when the dipping time was prolonged to 10 hours and beyond. This indicated that the nucleation and film growth of perovskite is a reversible process and 8 hours was found to be ideal for the two process to that is nucleation and film growth to perfectly take place. The transmittance data was simulated using multi-peak fitting SCOUT software from which other optical constants like refractive index was obtained as n = 2.3803, extinction coefficient k= 0.2215 and absorption coefficient α= 69855.23 for single step film samples. For the double step deposition method the refractive index of n=2.4011, extinction coefficient k= 0.2998 and absorption coefficient α= 71450.42 were revealed. The sheet resistivity of the films was evaluated using four-point probe. It was observed that an increase in annealing temperature from 80oC to 160oC led to decrease in sheet resistivity of films from 0.7982 Ω cm-1 to 0.4231Ω cm-1.The sheet resistivity of films deposited by double step decreased from 0.5675Ω cm-1 to 0.2290Ω cm-1. From the results herein it was deduced that the morphology of the perovskite thin films can be enhanced by not only the deposition methods but also annealing temperatures and dipping times.Item Design and fabrication of an energy efficient smart air conditioning system(Kenyatta University, 2022) Kavita, Dennis Mwania; Raphael Nyenge; Mathew MunjiResidential and commercial space cooling demands are increasing steadily throughout the world. This has led to high growth in demand for air conditioning (AC) systems. Technology is playing a key role in digitization of these systems with sensors and microcontrollers being used extensively. Energy conservation remains the main focus of scientists and engineers. In line with working towards developing energy efficient systems, we carried out research to optimize the control of air conditioners for energy conservation purposes. This research was geared towards having an energy efficient system. In this research, temperature, proximity and a passive infrared sensor (PIR) were used as smart sensors. The system was designed such that when room occupants’ approach a room, the system is activated and rapid cool down or warm up achieved within a predetermined time depending on the size of the room. As long as there is occupant in the room, the system settles quickly into the set conditions. When there is no one in the room, the system need not to be working and therefore it switches off. This ensures that the system only works when needed hence helps in energy conservation thus reducing bills paid by home owners and companies. The designed prototype is able to detect room occupancy, responds perfectly to temperature changes as well as human presence in the field of view of the PIR with an overall performance efficiency of 55.95% which is a good start towards actual implementation of an energy efficient A.C. system. We also recommend that utilization of more sensors like radiation detectors can be explored to diversify the working of this system.Item Positron Impact Elastic Scattering by Calcium Atom Using First Order Distorted Wave Born Approximation with a Complex Potential(Kenyatta University, 2022) Wakhu, Wechuli Benard; Peter K. Kariuki; Linturi J. MugambiThe concept of elastic scattering of projectiles by atomic targets has the fundamental importance in understanding the complex projectile-target interaction and the dynamics of the collision process. Compared to electrons, positron scattering is considered as the alternative way to acquire knowledge about atomic structures and to examine phenomena such as the Fermi surface of metal and nano-precipitates in solids. Further, positron scattering cross section data is essential for the development of various technological fields; for example astrophysics, plasma sciences, material sciences and bio-medicine. Additionally, positron cross sections are used as input data in some modeling software. Accurate cross section data is required in these applications. Thus, lack of complete agreement among the available theoretical data, unavailability of experimental data and the DWBA method with a complex potential at impact energy range 10-200 eV not having been utilized in such a study; are the reasons that informed this investigation. Consequently, this research sought to establish whether the second term of the DWBA T-matrix element significantly affect the cross sections and how the cross sections obtained herein compare with other calculations when the distorting potential is varied. After formulating the complex potential with positronium formation channel proficiently incorporated, the radial Schrödinger equation was solved numerically for low values of orbital angular momentum quantum number using the Numerov’s method. The associated integral equation was solved iteratively for high values of orbital angular momentum quantum number. The extracted phase shifts were used to compute the T-matrix which was then used to determine DCS while the optical theorem was applied to calculate TCS. With only static potential, the DWBA and OP methods yield same DCSs. The polarization potential increases the DCS at small scattering angles and further introduces a local minimum whose position shifts toward forward scattering angles with increasing projectile-target impact energy. With a real potential that incorporates static-polarization potentials, the structure of the present TECS for OP and DWBA is consistent with those of the available data. With a complex potential, the agreement between the present OP and DWBA DCS results is excellent. In conclusion, with a complex potential that incorporates positronium formation effect, the exact agreement between the DWBA and OP results implies insignificant effect of the second term of the direct T-matrix element on DCS as well as TCS while the effect of positronium on the cross sections does not extend beyond 150 eV. From these findings, it is recommended that at intermediate energies, a complex potential inclusive of positronium formation channel should be applied and the procedure of accounting for inelastic cross section suggested herein this study be comprehensively tested on positron-alkaline earth atoms to clearly establish its suitability.Item Determination of the Level of Naturally Occurring Radioactive Nuclides from Soil Samples in Kikuyu, Kiambu County, Kenya(Kenyatta University, 2022) Wangari, Gitahi Agnes; Nadir O. Hashim; Margaret CHegeHuman population is exposed to ionizing radiation from radionuclides. Radionuclides that occur naturally and other forms of radiation from materials such as water and vegetation releases ionizing radiation that can be a risk to human population. Radiation from these sources, referred to as background radiation, often goes un-noticed and therefore is not always easy to control. Additionally, human undertakings such as exploration/mining, construction of roads or rails and agricultural activities may introduce significant amounts of NORM in the atmosphere which may lead to enhanced levels of natural radiation levels. Exposure to such high radiation levels can lead to health problems like cancer, and it is for this reason that international bodies such as International Commission on Radiation Protection (ICRP) have proposed guidelines and recommendation such as reference levels aimed at reducing NORM-induced risks. This study looks at concentration levels of NORM in top level soils around Kikuyu subcounty in Kiambu County. 20 samples of these soils were sampled randomly from 4 different sampling cites namely Ondiri, Kidfarmaco, Kalro and Alliance girls high school grounds. The study area was selected based on the most resent constructed Southern bypass whose erosion landed to the Ondiri Swamp.At Kidfirmaco there were caves that exist and of late the population around them has increased rapidly. At Kalro and Alliance girls, there are large scale farming areas where most residents in Kikuyu purchase their foodstuff from. The samples were dried in an oven at 1000℃ for 24 hours to completely remove the moisture. Each sample with a mass of about 300g was packed in the special polythene plastic containers which were tightly sealed. The containers were kept for 30 days for radionuclides to reach secular equilibrium. The samples were analysed using NaI(Tl) gamma-ray scintillator to determine their content of 232Th, 238U and 40K and the associated risk indices. The concentration level of 40K, 238U and 232Th in the samples were 1363.87±88.46 Bq/kg , 172.16±58.75 Bq/kg , 275.56±21.86 Bq/kg respectively while the the radium equivalent activity, external and internal hazard indices were 498±25 Bq/kg, 1.85 ±0.093,1.15±0.058 respectively. The average dose rate was estimated as 279.9 nGy/h and annual effective dose rate 0.68mSv/y. While this dose rate is less than the ICRP reference level of 1 mSv/y for the general public, the risk indices were found to be above the ICRP reference level. This may be due to the high levels of U and Th in the samples relative to the world average levels of 33 Bq/kg and 45 Bq/kg respectively. I recommend more study to be done on rocks near the railway and the road construction and also explore the use of organic fertilizer at Alliance girls and KALROItem Assessment of Radioactivity Concentration and Radiation Hazards Index for Building Materials Used in Babadogo Estate, Nairobi City County, Kenya(Kenyatta University, 2022) Oborah, Amukah Kenneth; Nadir O. Hashim; Charles M. MigwiNatural radioactive materials in certain conditions can get to hazardous radiological level. Some of these hazards are not prone to control as well as, they are usually referred to as the background radiation. The aim of my research work is to evaluate natural radioactivity concentration and radiological impacts on representative sampled building materials collected from different locations in Babadogo estate within Nairobi City County. The selected samples were crushed, sieved dried and store for four weeks after which, analysis done using gamma ray spectrometer was put into action for spectral data acquisition then analysis. The activity concentration levels of 238U, 232Th and 40K for the selected samples of building materials was measured by the use of gamma- ray spectrometry method. Radiological parameters were evaluated based on the prerequisite activity concentration obtained. The analyzed data compared with the standard acceptable values. The activity concentration in 40K varied from 55±3 to 2647±132 Bq/kg giving average value of 831 ±42 Bq/kg, 238U varied from 39±2 to 3602±180Bq/kg giving average figures of 378±19Bqkg¯1and 232Th ranged from 5.000±0.300 to 4213±211Bqkg¯1 giving mean figure of 290±15Bq/kg . Calculated mean figures for activity concentration surpassed the world mean figures of 420Bq/kg, 33Bq/kg, 45Bq/kg in 40K, 238U and 232Th respectively. Absorbed dose rate calculated ranges between 73±4 and 4777±239nGyh¯1 having average value of 540±27nGyh¯1 .The mean number for the absorbed dose rate was above the world acceptable mean value of 54nGyh¯1. The calculated annual effective dose rate varied from 0.040±0.002mSvy¯1 to 2.340±0.117mSvy¯1 having average figure of 0.260±0.013mSvy¯1 ,which was above the world average of 0.070mSvy¯1but below the maximum dose constraint of 1mSvy¯1.These results show that building materials in Babadogo estate are safe and can be used for construction of buildings and thus can be continued using as further research is done on other building materials not covered in my research work.Item Design and Fabrication of an Energy Efficient Smart Air Conditioning System(Kenyatta University, 2022) Mwania, Kavita Dennis; Raphael Nyenge; Mathew MunjiResidential and commercial space cooling demands are increasing steadily throughout the world. This has led to high growth in demand for air conditioning (AC) systems. Technology is playing a key role in digitization of these systems with sensors and microcontrollers being used extensively. Energy conservation remains the main focus of scientists and engineers. In line with working towards developing energy efficient systems, we carried out research to optimize the control of air conditioners for energy conservation purposes. This research was geared towards having an energy efficient system. In this research, temperature, proximity and a passive infrared sensor (PIR) were used as smart sensors. The system was designed such that when room occupants’ approach a room, the system is activated and rapid cool down or warm up achieved within a predetermined time depending on the size of the room. As long as there is occupant in the room, the system settles quickly into the set conditions. When there is no one in the room, the system need not to be working and therefore it switches off. This ensures that the system only works when needed hence helps in energy conservation thus reducing bills paid by home owners and companies. The designed prototype is able to detect room occupancy, responds perfectly to temperature changes as well as human presence in the field of view of the PIR with an overall performance efficiency of 55.95% which is a good start towards actual implementation of an energy efficient A.C. system. We also recommend that utilization of more sensors like radiation detectors can be explored to diversify the working of this system.Item Analysis of Telluric Currents on Miniature Electrical and Electronic Circuits in Nairobi City and Kajiado Counties, Kenya(Kenyatta University, 2021) Odhiambo, Okoth Collins; Raphael Nyenge; Mathew MunjiThe necessity for electrically ensured and trustworthy electrical and electronic contraptions or systems is growing in various business areas around the world, for instance, mechanical and manufacturing, vehicle, clinical, imperativeness, common science, information and correspondence development and sharp grid applications. The makers and end-customers of these contraptions or systems are depending on additional state-of-the-art headways that are electrically ensured, distortion free and pass on higher accuracy that grants action in under impeccable conditions. Perhaps the best region is the electronic devices, the science that incorporates the assessment and utilization of incredibly small scale systems and can be used over the entire science field. This assessment investigated the amplitudes of telluric currents in Embakasi, Nairobi City and Ongata Rongai, Kajiado counties, considering a locale of 10000 m2 as a result of obliged space available in each zone. Measurements were done by use of EX542:12 Multimeter and analysis conducted using informative sensible software known as Statistica. The measurements gave extents of constraining level of electrical hazard exhibited by telluric currents to electrical, electronic and media transmission devices or systems that rely upon these devices. The amplitudes of telluric currents measured and analyzed were seen as significant to present perilous electrical condition to underground structures, in this way measures to alleviate the risks were prescribed, such as electromagnetic shielding and earthing. To improve on the amplitudes of the measured telluric currents, the electrodes should be of high electrical properties such as silver coated electrodes. The choice of area of study was advised by higher concentration of underground installations in Nairobi county in relation to Kajiado county, hence basis of telluric currents measurement comparison.Item Modelling of Petroleum System Structures by Use of Gravity and Seismic Data in Kerio Valley Basin, Kenya(Kenyatta University, 2021) Sila, Faith; Willies j. Ambuso; Githiri J. GitongaKerio valley basin is one of the sedimentary basins in Kenya known to have hydrocarbon formation potential. Exploration is ongoing in the area with different geophysical methods being employed. The possible existence of significant hydrocarbons has led to increase investigating the structures developed interest in geological structures and basin modelling. This research utilized 2D seismic and gravity data with the aim of determining density variation within the basin, their characteristics and model geological structures of Kerio Valley basin. Gravity data collected in the basin was processed and interpreted using Golden surfer 8 to provide information about rock density contrast for the sedimentary layers. These sedimentary layers form from deposition and compaction of rocks due to pressure as the basin evolved. Data was uploaded in Euler deconvolution software with structural index of 1.0 and 0.5 in window size. It was again loaded in Grav2dc for forward modelling and the average density contrast values used were 2.2g/cm3, 2.5g/cm3, 2.28g/cm3 and 2.6g/cm3 respectively from the top to the deepest stratigraphic layer formed due to deposition and compaction of different rocks over a period of time. Seismic data was interpreted using PetroMod software, the value used for heat flow was 68Mw/m2 and paleo water depth were and 68m,112m,700m,840m and 900m as model input. Over a long period, the basin passed through tectonic regime and transformed into a sedimentary basin. ID model showed that the source rocks are mature and have potential to produce hydrocarbon as shown by vitrinite reflectance. Temperature curves show that temperature was maximum during Miocene volcanics and has been decreasing over a period of time. Gravity data analysis showed that there are high gravity anomalies at the western and eastern sides, low gravity anomalies at the centre of the basin and the sedimentation is constrained by two major faults. The basin is underlain by a deeper basement which is overlain by interbeds of sandstones and volcanoes. Seismic reflectors showed discontinuities which may be caused by lava flows. The deepest reflector showed the deep sedimentation in the basin. Geological structures necessary for hydrocarbon formation are present