https://repository.biust.ac.bw/handle/123456789/411 This collection is made up of papers, posters and presentation slides presented by both FET students and staff at national, regional and international conferences, workshops and seminars. 2026-04-21T05:41:34Z https://repository.biust.ac.bw/handle/123456789/507 Software controlled stepping valve system for a modern car engine Zibani, I; Marumo, R; Chuma, Joseph; Ngebani, I To address the problem of a piston-valve collision associated with poppet valve engines, we replaced the conventional poppet valve with a solenoid operated stepping valve whose motion is perpendicular to that of the piston. The valve events are software controlled, giving rise to precise intake/exhaust cycles and improved engine efficiency. Other rotary engine models like the Coates engine suffer from sealing problems and possible valve seizure resulting from excessive frictional forces between valve and seat. The proposed valve on the other hand, is located within the combustion chamber so that the cylinder pressure help seal the valve. To minimize friction, the valve clears its seat before stepping into its next position. The proposed system was successfully simulated using ALTERA's QUARTUS II Development System. A successful prototype was built using a single piston engine. This is an ongoing project to eventually produce a 4-cylinder engine. 2017-10-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/506 Chemical absorption of carbon dioxide in Biogas Purification Maile, O.M.; Muzenda, E.; Tesfagiorgis, H. Biogas is produced from anaerobic digestion of organic biodegradable materials. However, its application is limited as it contains impurities such as carbon dioxide (CO2), hydrogen sulphide (H2S), and other trace gases. Chemical absorption is capable of producing gas of high methane content above 95% and has no methane losses hence it's widely used on large scale applications. Sodium hydroxide was used for cleaning the biogas in this study at a concentration of 1 M, 2 M, and 3 M. The effect of concentration on absorption and CO2 removal efficiency was studied. It was observed that an increase in concentration lead to an increase in the absorption rate and the removal efficiency respectively. The highest removal efficiency was recorded to be 66%. 2017-01-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/505 Diffusion in Saturated Clayey Barrier Medium Agbenyeku, E.E.; Muzenda, E.; Msibi, M.I. The design of clay/clayey barriers for the containment of buried wastes conventionally has been based on the assumption that the hydraulic conductivity controls the rate of leachate percolation. However, recent studies show that diffusion is a controlling mechanism of solute transport in many fine-grained soils. Although the measurement of the hydraulic conductivity of fine-grained soils is comparatively a common practice in soil engineering, the measurement of diffusion coefficients is not. As such, it is becoming increasingly essential to assess the movement of chemicals through soil barriers due to diffusion. Studies indicate that diffusion may be an important, if not dominant mechanism of contaminant transport through waste containment barriers. This paper is therefore in line with the efforts made in the measurement of diffusion coefficients of inorganic chemicals passing through saturated soils. Herein, both steady-state and transient equations relating to the diffusive transport of inorganic chemicals are presented. A number of factors affecting diffusion coefficients are identified and a simple method for measuring diffusion coefficients for a compacted barrier is defined. The definition for the diffusion coefficient of soil called the effective diffusion coefficient, D* is seen to vary widely. Generally, the variations are due to the different factors affecting diffusion of solutes in soil and the various ways of including the volumetric water content in the governing equations. Hence, errors in interpretation and comparison of D* values can occur if the appropriate definition is not used. In a nutshell, the concept of diffusion may be unfamiliar to many soil specialists, worsened by the myriad terminologies linked to the study of diffusion in soils. Thus the study attempts to acquaint soil engineers with vital information for the measurement of diffusion coefficients for barrier designs. 2017-01-01T00:00:00Z https://repository.biust.ac.bw/handle/123456789/410 Liner-leachate interaction curve models for clayey soils from landfills around the city of Johannesburg Agbenyeku, Emem-Obong Emmanuel; Muzenda, Edison; Msibi, Mandla Innocent The study presented herein links to a regression analysis that ties into three mathematical models from the Brutsaert, Mualem and Burdine equations respectively. The paper describes a series of experimental investigations on the characteristic permeation and interaction of three clayey soil types as barrier liners with landfill leachate from around the City of Johannesburg (CoJ), South Africa. From the outcomes therefrom, sequence of logarithmic relationships were projected towards proposing rational approximations of the best curve-fitting bounds using the Grain Size Distribution (GSD) and Atterberg Limits (AL) of the respective soils as selected classification properties. The outcomes which generally revealed reasonable indicative values were expressed using the weighted Plasticity Indices (PI) of the respective soils in conformance to Sitarenios et al. The two curve-fitting parameters x and z incorporated to simulate the Liner-Leachate Interaction Curve (LLIC) of the three clayey soils sampled from respective landfills around the CoJ, South Africa yielded 118, 0.6; 1211, 0.6; 1058, 0.6 in the Brutsaert model, 0.1, 1.2; 0.0, 1.5; 0.0, 1.5 in the Mualem model and 0.1, 2.4; 0.0, 2.6; 0.0, 2.7 in the Burdine model for samples A, B and C respectively, with a general R2 value of 0.904. 2017-01-01T00:00:00Z