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    A Fuzzy Inference System for Modelling Streamflow: Case of Letaba River, South Africa.
    (Elsevier, 2008-07-10) Katambara, Zacharia; Ndiritu, John
    Stream flow modeling of Letaba River in South Africa is complicated by several factors including the existence of dams and other storage structures whose releases are intermittent and based on rules of thumb depending on the irrigation demands and the need to maintain the flow required in the Kruger National park (KNP). The KNP is located about a hundred kilometers downstream of the main storage and water flows through an alluvial aquifer where complex surface–groundwater interactions occur. Farmers abstract water intermittently along the route directly from the river or indirectly from the alluvial aquifer complicating the flow patterns even more. Consequently, the stream flow series in the river shows very little similarity to what would be considered as natural. The actual abstractions are not measured and only monthly estimates of the abstractions currently exist. Like in many other basins in South Africa, stream flow, groundwater level, rainfall and evaporation data in Letaba is sparse and not very reliable. The Takagi–Sugeno fuzzy inference system using subtractive clustering, an approach which is capable of dealing with vague and inadequate information and data has therefore been used to develop a daily stream flow model for Letaba River. In order to take into account the spatial variability and to maximize the use of the available data, the model is applied in a semi-distributed manner consisting of three river reaches. The shuffled complex evolution (SCE-UA) optimizer has been used to calibrate the model. Six years of data from March 2002 to April 2008 has been used for model calibration and verification. To maximize the Nash-Sutcliffe efficiency, the minimum number of clusters required was found to be 10 for 1000 data points in calibration. An analysis of the location of the cluster centers, the coefficients relating the inputs with the simulated stream flow, and the degrees of membership indicates that no single cluster can be associated to the simulation of a specific hydrologic process or component of the stream flow hydrograph (e.g. high flows or low flows). The fuzzy model does not therefore provide any evidence that it is not a pure black box. The Nash–Sutcliffe efficiency results obtained in calibration and verification showed average values of 0.658 and 0.535 with poor values on the first river reach. Very low percent bias values averaging to _0.4% and _2.7% in calibration and verification are obtained highlighting the model’s potential for applications where mass balance considerations are most important.
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    A TIME-DEPENDENT GREEN ELEMENT FORMULATION FOR SOLUTION OF POTENTIAL FLOW PROBLEMS IN 3 DIMENSIONAL DOMAINS
    (University of the Witwatersrand, Johannesburg, 2010) Nyirenda, Edwin
    In this work we develop a generalised methodology for the solution of the time dependent second order parabolic differential equation of potential flow in heterogeneous media using the Green element method. Parabolic differential equations are one class of differential equations, the others being elliptic partial differential equations and hyperbolic differential equations. Since elliptic differential equations generally arise from a diffusion process that has reached equilibrium, they can also be solved using the methodology developed, and represent a simplification because of the steady state situation. Potential flow problems are of great interest in many engineering applications such as flow in aquifers, heat transfer processes, electro-magnetic field problems, etc. Traditionally, the finite difference method and the finite element method have proved to be powerful techniques to solve such potential flow problems, but each has limitations and challenges which have led to continued research in numerical methods. The finite difference method is more applicable to domains with regular boundary, and the finite element method, though extremely versatile, exhibits unacceptable inaccuracies with coarse meshes, thus requiring fine meshes with the associated high computation costs. In view of some of the limitations with these earlier methods, several numerical schemes are now being developed as viable alternatives to these conventional methods. Among such methods are the boundary element method, the finite volume method, and the analytic element method. The boundary element method has been particularly promising because of its domain-reduction feature and the second order accuracy that can generally be achieved. The domain-reduction feature of the boundary element method, though achieved for restricted class of problems, lends it to efficient grid generation algorithm, while its second-order accuracy ensures reliability and consistency of the numerical solutions.-iv _________________________________________________________________ The boundary element method in its original formulation is unable to deal with heterogeneities in the domain. For physical problems, especially in groundwater flow, heterogeneities and anisotropy are a natural and frequent occurrence, and this has fuelled research into boundary element techniques that are capable of accommodating these features. The Green element method is one technique which is based on the boundary element theory and which has been proven to be very effective in handling heterogeneities and anisotropy in 1D and 2D domains. However, development of techniques to implement the Green element method in 3D domains has remained largely unexplored. This work represents an effort in this direction. We have investigated the adoption of the general tetrahedral and hexahedra elements for use with the Green element method, and found that the large number of degrees of freedom generated precludes retention of the internal normal direction as in 1D and 2D formulations. Furthermore, some of the complicated surface and domain integrations with these elements can only be addressed with quadrature methods. The compatibility issues that arise between element faces, which present considerable challenges to multi-domain boundary element techniques, are innovatively addressed in the computer code that has been developed in this work. The Green element method is implemented for steady and time-dependent problems using regular hexahedra elements, and the results show that the performance is slightly better than the results obtained using FEMWATER. FEMWATER is an established finite element method software. No attempt is made to compare the computation efficiencies of the 3D GEM code and FEMWATER because the two codes were not developed on a common platform.
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    Adaptive Iir Filters For Single Interference Suppression In A BPSK DS CDMA System In Rayleigh Fading Channel
    (University of Dar es Salaam, 2007-07-01) Mvuma, Aloys N.
    In this paper, effect of a single narrow-band interference (NBI) on bit error rate (BER) performance for a binary phase shift keying (BPSK) synchronous direct-sequence code-division multiple access (DS CDMA) communication system operating in a frequency nonselective Rayleigh fading channel is analyzed. Second-order adaptive infinite impulse response (IIR) notch filters with plain gradient algorithm (GA) for suppression of NBI in the DS CDMA system are proposed. A general closed-form BER expression for the DS CDMA system with NBI suppression second order adaptive IIR notch filters is derived based on the standard Gaussian approximation (SGA) method. BER expressions are then derived for the allpass filter-based adaptive IIR notch filter and adaptive IIR notch filter with constrained poles and zeros, the two structures that are commonly found in literature. It is observed that both adaptive IIR notch filter structures exhibit comparable BER performance. Extensive computer simulation results are presented to verify the accuracy and limitations of the analysis.
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    Adopting the System of Rice Intensification (SRI) In Tanzania: A Review
    (SciRes., 2013-06-02) Katambara,Zacharia; Kahimba, Frederick C.; Mahoo, Henry F.; Mbungu, Winfred B.; Mhenga, Fikiri; Reuben,Paul; Maugo, Muyenjwa; Nyarubamba, Anthony
    The demand of water for irrigation purposes in Tanzania outstrips the amount of water available for irrigation and other demands. On the other hand, the demand for more food to feed the growing population is increasing, calling for the need to have technologies and farming practices that ensure more food production while minimizing water uses. Rice is among cereal crops grown in Tanzania, and it can assist in meeting the food demand for the nation. Majority of rice producers in Tanzania and Sub-Saharan Africa (SSA) are subsistence farmers and they practice continuous flooding, a technique that requires much water. In addition to using large amounts of water, the conventional practices of growing paddy using local varieties transplanting process are implemented when seedlings are more than 21 days old, and 3 - 4 seedlings are transplanted in one hole. This practice results in low yields, and low water productivity and water use efficiency. The system of rice intensification (SRI) on the other hand, is a promising new practice of growing paddy rice that has proven to be very effective in saving water and increasing rice yields in many parts of the world. SRI practice is spreading fast and it has been adopted in many countries. The SRI practice has been introduced in Tanzania during the last 3 years as such it is not widely practiced. This paper reviews SRI practice at global, regional and country (Tanzania) level, and evaluates the challenges, opportunities and implications for its adoption in Tanzania. Knowledge gaps at each level have been identified and discussed as well as suggestions for researchable areas.
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    Afractional-Order Trypanosomabrucei Rhodesiense Model With Vector Saturation and Temperature Dependent Parameters
    (SPRINGER, 2020) Helikumi, Mlyashimbi; Kgosimore, Moatlhodi; Kuznetsov, Dmitry; Mushayabasa, Steady
    and density of tsetse fly population. Precisely, ectotherm performance measures, such as development rate, survival probability and reproductive rate, increase from low values (even Temperature is one of the integral environmental drivers that strongly affect the distribution zero) at critical minimum temperature, peak at an optimum temperature and then decline to low levels (even zero) at a critical maximumtemperature. In this study, a fractional-order Trypanosomabrucei rhodesiense model incorporating vector saturation and temperature dependent parameters is considered. The proposed model incorporates the interplay between vectors and two hosts, humans and animals. We computed the basic reproduction number andestablished results on the threshold dynamics. Meanwhile, we explored the effects of vector control and screening of infected host on long-term disease dynamics. We determine threshold levels essential to reducing the basic reproduction number to level below unity at various temperature levels. Our findings indicate that vector control and host screening could significantly control spread of the disease at different temperature levels.
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    An Artificial Neural Network Model of the Crocodile River System for Low Flow Periods.
    (Wits, 2009-01-21) Sebusang, Nako M.
    With increasing demands on limited water resources and unavailability of suitable dam sites, it is essential that available storage works be carefully planned and efficiently operated to meet the present and future water needs.This research report presents an attempt to: i) use Artificial Neural Networks (ANN) for the simulation of the Crocodile water resource system located in the Mpumalanga province of South Africa and ii) use the model to assess to what extent Kwena dam, the only major dam in the system could meet the required 0.9m3/s cross border flow to Mozambique. The modelling was confined to the low flow periods when the Kwena dam releases are significant. The form of ANN model developed in this study is the standard error backpropagation run on a daily time scale. It is comprised of 32 inputs being four irrigation abstractions at Montrose, Tenbosch, Riverside and Karino; current and average daily rainfall totals for the previous 4 days at the respective rainfall stations; average daily temperature at Karino and Nelspruit; daily releases from Kwena dam; daily streamflow from the tributaries of Kaap, Elands and Sand rivers and the previous day’s flow at Tenbosch. The single output was the current day’s flow at Tenbosch. To investigate the extent to which the 0.9m3/s flow requirement into Mozambique could be met, data from a representative dry year and four release scenarios were used. The scenarios assumed that Kwena dam was 100%, 75%, 50% and 25% full at the beginning of the year. It was found as expected that increasing Kwena releases improved the cross border flows but the improvement in providing the 0.9m3/s cross border flow was minimal. For the scenario when the dam is initially full, the requirement was met with an improvement of 11% over the observed flows.
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    An Investigation for Energy Sustainability in Cement Industries in Tanzania: The Case of Mbeya Cement
    (Technische Universität Berlin Institut für Energietechnik, 2017) John, John Pius
    Cement production processes are facing crucial sustainability issues such as inefficient en‐ ergy and raw material use, product supply, production cost and environmental pollution. High energy and material use dominated by inefficient characteristics of cement production processes, in turn, lead into depletion of non‐renewable resources, increased production costs as well as environmental degradation due to emissions. The main objective of the study was to investigate performance of cement industry in Tanza‐ nia relative to sustainable energy utilization. Most of past researches have evaluated the per‐ formance of cement production processes using first law of thermodynamics alone (mass and energy balances) with the objective of improving energy efficiency. Although this ap‐ proach sheds light on the question of improvement of energy use in the processes, it has some limitations. The limitations are imposed by the internal irreversibility due to combustion and other physico‐chemical nature of reactions dominating the whole processes. The current emerging approach, which overcomes limitations imposed to the first law approach is ex‐ ergy‐based method, relatively new in evaluation of performance of cement production pro‐ cesses. However, owing to complexity of cement production processes, applying an exergy‐ based method manually is very difficult and complex. The current study proposes combined approach of exergy based method and modeling as well as simulation. The model was successfully developed, validated using real plant data and was used to predict the performance of the cement dry rotary kiln system of Mbeya Cement production processes. Data obtained from modeling and simulation were further used to evaluate the performance of processes, individual components, sub‐systems and overall kiln system at large using exergy based method. The approach not only simplifies the analyses but also gives detailed insight of real processes, source and type of real imperfections, its magnitudes and how imperfections can be minimized. Major findings indicated that the rotary kiln sub‐systems and the overall kiln system have poor exergetic performance, suggesting that potential for improvement exists. The overall exergy efficiency of the kiln system is around 33 %. Also results indicated that the rotary kilns have the lowest exergetic efficiency of about 14 % followed by the clinker cooler with exergetic efficiency of about 41.11 %. The highest source of irreversibility encompassed chemical reactions, especially calcination and clinker burning processes with exergy destruc‐ tion of 2,813.75 kJ⋅kgcl−1 and 1,148.17 kJ⋅kgcl−1. Results from parametric analysis suggested that if measures for improvements of processes, components and sub‐systems are taken, a significant amount of fuel and specific energy could be saved. Furthermore, it was confirmed that if the avoidable exergy destruction is minimized, processes, system components and sub‐systems performance could be improved from exergetic point of view.
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    Analysis of Flooding Effects on the Msingi Masonry Arch Bridge in Mkalama, Singida, Tanzania
    (MUST Journal of Research and Development (MJRD), 2025-06-30) Katambara, Z; Kifanyi ,G; Barthazar, D
    Human induced hydraulic factors have emerged as the leading cause of bridge failures since the 1990s, accounting for approximately 50% of incidents recorded in the authors' database. These failures often occur without warning and result in substantial structural damage. With the intensifying impacts of climate change globally and particularly in Tanzania, such events are projected to become more frequent. Among hydraulic causes, flooding poses the most significant risk, primarily through mechanisms like erosion, high hydraulic forces, and sedimentation. This study assesses the vulnerability of the Msingi Masonry Arch Bridge to flooding, examining both immediate and long-term impacts on its structural integrity. It evaluates the bridge's exposure to flood-related hazards and compares the original design discharge capacity of 1497.57 m³/s with the updated estimate of 1777.90 m³/s, revealing a critical under-capacity during peak flows. Based on these findings, the study proposes adaptive strategies to enhance the bridge’s flood resilience. Key recommendations include reinforcing embankments with stone retaining walls, raising the bridge elevation to accommodate future flood levels, and redesigning piers with upstream V-shaped walls to reduce debris accumulation. Additionally, the study advocates for community engagement through awareness programs and the preservation of natural riverbank vegetation to mitigate erosion. These measures aim to inform stakeholders and serve as a reference for flood-resilient infrastructure planning in similarly vulnerable regions.
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    Application of Conceptual Model in Developing the Jangwani Mini-Hydropower Plant in Ruvuma Region, Tanzania
    (Mbeya University of Science and Technology Journal of Research and Development (MJRD), 2021-10-28) Katambara, Z
    The Seventh Sustainable Development Goal is on ensuring access to affordable, reliable, sustainable and modern energy. The promotion and the use of renewable energy sources is inevitable. Within the spectrum of renewable energy sources, there are the mini-hydropower plants which have been reported to have the potential to provide for rural electrification. The existence of reliable flowing water necessitates the investment in mini hydropower for off grid systems. To prove the viability of such schemes, a hydrological analysis of the Mtandazi River was conducted. The Australian Water Balance Model, a conceptual model, was used to model the stream flows using the California Method. The results suggest that for 95% exceedance, the flow is 1.62 m3/s. The flows will enable the installation of the Jangwani mini hydropower plant to generate 226.7 kW of electricity in Ruvuma Region, Tanzania. The study recommends for the conservation of the catchment for the sustainability of the flows.
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    Application of the RUSLE model to estimate sedimentation in the Lwanyo Reservoir in Mbarali District Mbeya – Tanzania
    (IWA, 2025-02-17) Moshi, Baraka Moses; Katambara, Zacharia; Lingwanda, Mwajuma
    The constant increase in the global population is proportional to the increase in basic human needs associated with environ mental degradation. Sedimentation in water bodies poses socio-economic challenges as it lessens the storage capacities. The RUSLE model expresses the effect of sedimentation in the Lwanyo reservoir sub-catchment. Key factors influencing sedimentation include: maximum erosivity factor (R) is 421.39 (MJ mm ha 1 h 1 yr), the soil erodibility factor (K) is 0.071, the topographic factor (LS) due to catchment topography is 9.086, the vegetation cover and management factor (C) is 0.1045, and the conservation practice factor (P) is 0.14. The RUSLE model estimates soil sediment loss to be 3.977 tonnes/ha/year, as the average annual soil loss for the Lwanyo sub-catchment area is 39.6 km2 . This value indicates that for every hectare, the average annual soil loss is 1.004 10 3 tonnes/year, with silt as the dominant soil sediment being eroded. If no intervention measures are implemented, the sediment load could reach 119.31 tonnes over 30 years, reducing the reservoir’s storage capacity by 68.177 m3 . Reducing human activity in the catchment and promoting afforestation to mitigate sedimentation can help increase soil stability and reduce erosion.
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    Assessing Key Performance Factors in Final-Year Civil Engineering Students at Mbeya University of Science and Technology, Tanzania by Using Principal Component Analysis
    (Mbeya University of Science and Technology, 2025-03-10) Katambara, Z; Matungwa William
    This study applies Principal Component Analysis (PCA) to evaluate and under stand academic performance among final-year Civil Engineering students at Mbeya University of Science and Technology (MUST) in the academic year 2023/2024. Responding to Tanzania’s growing demand for skilled engineers, this research provides data-driven insights into student achievement patterns, revealing the core factors impacting performance. PCA was utilized to reduce dimensionality, transforming course grades into uncorrelated components that capture underlying performance structures. The results identify three primary components: Core Academic Knowledge, explaining 41.38% of the variance; Specialized Applied Skills, contributing 10.07%; and Advanced Independent Skills, accounting for 6.71%. Together, these components explain 58.16% of total performance variance, indicating a robust framework for understanding student success drivers. Additional analysis, including correlation matrices and descriptive statistics, highlights patterns across courses, revealing strong relationships within core competencies and independent distinctions in advanced courses. Findings suggest curriculum enhancements and targeted interventions that could better pre pare students for industry needs, focusing on core academic support, practical skills enhancement, and resources for advanced technical areas.
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    Assessment of Scouring Effect of Msingi Masonry Arch Bridge in Mkalama, Singida, Tanzania
    (ABUAD Journal of Engineering Research and Development (AJERD), 2025) BARTHAZAR, Dickson; KATAMBARA, Zakaria; KIFANYI, Gislar.
    This study presents an integrated geotechnical and hydraulic assessment of the Msingi Masonry Arch Bridge in Mkalama District, Singida, Tanzania, to evaluate scour vulnerability, subsurface strength, and structural load capacity. Field investigations included Dynamic Probing Light (DPL) testing, core sampling, and particle size analysis at six test pits (DS1–DS6), alongside laboratory tests adhering to BS 1377:1990 standards. Results revealed significant spatial variability in soil gradation and compaction, with deeper layers demonstrating high bearing capacities (up to 1555.8 kN/m²), while surface strata exhibited loose conditions and higher susceptibility to erosion—particularly in zones with elevated fines content. Hydraulic modelling, using site-specific parameters such as hydraulic radius (1.88 m), channel slope (0.0082), and Manning’s coefficient (0.017), predicted a scour depth of 2.6 m, compared to the observed 2.0 m. Structural analysis using the MEXE method yielded an allowable axle load of 28.05 tonnes, translating to a foundation pressure of 98.6 kN/m², which is within safe soil capacity limits. Despite current structural stability, the narrow scour margin and near-threshold loading conditions indicate elevated long-term vulnerability. The study recommends immediate installation of scour countermeasures, selective foundation deepening in weak zones, and routine monitoring to enhance the resilience and longevity.
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    Assessment of Siltation Impact and Mitigation Strategies for Sustaining Storage Capacity in Lwanyo Dam, Tanzania
    (MJRD, 2024-09-03) Baraka M. Moshi; Zacharia Katambara,; Mwajuma Lingwanda
    The ongoing generation, transportation, and deposition of silt in the Lwanyo Dam has significantly reduced the storage capacity of the Lwanyo Reservoir, originally constructed to support irrigation and the surrounding ecosystem. The objective of this paper was to assess the extent of siltation in Lwanyo Dam, evaluate its impact on the dam's storage capacity, and propose measures to mitigate silt accumulation. The upstream catchment area, approximately 39.6 km², includes around 128,991 m² allocated for rain-fed crop cultivation and 5.89 km² for pastoral activities. Frequent overtopping of the reservoir has been observed, largely due to siltation reducing its live storage capacity. In the reservoir trial pits were excavated and assessed, and they indicate that average silt layers range in thickness from 0.54 m to 0.98 m per rainy season. The deposited material consists of a silt layer from 0 to 540 mm, followed by an intermediate clay layer from 540 mm to 3100 mm. The impounded silt depth was measured at 1270 mm, with an estimated siltation volume of 58,349.4644 m³. The reservoir's original storage capacity of 210,153 m³ has been reduced by 27.765% due to siltation. The reservoir’s structural design inadequately addresses silt management, lacking both silt flushing tunnels and upstream silt check dams. The analysis indicates that storage capacity decreases by 3.085% annually, and if this linear trend continues without any intervention measures, the dam will lose all storage capacity within 24 years. The study recommends urgent measures to mitigate silt accumulation.
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    Assessment of Spatial Water Quality Variations in Shallow Wells Using Principal Component Analysis in Half London Ward, Tanzania
    (Scientific Research Publishing, 2025-02-21) Matungwa, William; Katambara, Zacharia
    Groundwater is a crucial water source for urban areas in Africa, particularly where surface water is insufficient to meet demand. This study analyses the water quality of five shallow wells (WW1-WW5) in Half-London Ward, Tun duma Town, Tanzania, using Principal Component Analysis (PCA) to iden tify the primary factors influencing groundwater contamination. Monthly samples were collected over 12 months and analysed for physical, chemical, and biological parameters. The PCA revealed between four and six principal components (PCs) for each well, explaining between 84.61% and 92.55% of the total variance in water quality data. In WW1, five PCs captured 87.53% of the variability, with PC1 (33.05%) dominated by pH, EC, TDS, and microbial contamination, suggesting significant influences from surface runoff and pit latrines. In WW2, six PCs explained 92.55% of the variance, with PC1 (36.17%) highlighting the effects of salinity, TDS, and agricultural runoff. WW3 had four PCs explaining 84.61% of the variance, with PC1 (39.63%) showing high contributions from pH, hardness, and salinity, indicating geological influences and contamination from human activities. Similarly, in WW4, six PCs ex plained 90.83% of the variance, where PC1 (43.53%) revealed contamination from pit latrines and fertilizers. WW5 also had six PCs, accounting for 92.51% of the variance, with PC1 (42.73%) indicating significant contamination from agricultural runoff and pit latrines. The study concludes that groundwater quality in Half-London Ward is primarily affected by a combination of surface runoff, pit latrine contamination, agricultural inputs, and geological factors. The presence of microbial contaminants and elevated nitrate and phosphate
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    Assessment of Temporal Variations in Shallow Well Water Quality Using Graphical Analysis and Water Quality Index in Half-London Ward, Tunduma, Tanzania
    (Mbeya University of Sience and Technology, 2025-03-01) William, Matungwa; Katambara, Zacharia
    Shallow wells are vital for water supply in regions lacking centralised systems, but they are highly susceptible to contamination from anthropogenic activities and natural processes. This study investigated seasonal variations in water quality from five shallow wells in Half London Ward, Tunduma, Tanzania, over a 12-month period to assess biological, chemical, and physical parameters, to identify contamination drivers, and to propose sustainable management solutions. Using WHO and EPA guidelines, monthly water sampling was conducted for 12 months from June 2022 to May 2023. Parameters analysed included Faecal and Total Coliforms, Nitrate, Phosphate, Total Iron, Biological Oxygen Demand (BOD), pH, Electrical Conductivity (EC), Turbidity, Total Dissolved Solids (TDS), and Total Suspended Solids (TSS). The National Sanitation Foundation Water Quality Index (NSFWQI) was employed to classify seasonal variations in water quality. Results revealed significant seasonal trends. Microbial contamination peaked during the rainy season, with shallow well WW3 and WW5 recording faecal coliform levels of 5 CFU/100 ml and total coliforms of 18 CFU/100 ml, exceeding WHO and East African Standards. Phosphate levels in shallow well WW4 and WW5 exceeded the threshold of 2.2 mg/l, attributed to agricultural runoff. Elevated iron concentrations (1.85 mg/l) in WW4 reflected natural geological leaching. BOD and turbidity increased during wet periods due to organic pollutants and sediment influx, while physical parameters such as pH and TDS remained within permissible limits. The NSFWQI ranged from "Excellent" (18.6) in shallow well WW5 during winter to "Medium" (65.4) in shallow well WW3 during summer, highlighting contamination risks from surface runoff and poor land management. The study concludes that rainfall and proximity to pollution sources significantly impact shallow well water quality. It recommends implementing community-driven sanitation measures, protecting shallow wells, and conducting routine monitoring. These findings provide a framework for improving groundwater quality for domestic use in urbanising regions globally.
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    Assessment of the Influence of Tip Speed Ratio, Solidity and Reynolds Number on the Aerodynamic Performance of Selected Locally Fabricated Wind Turbines in Tanzania
    (The University Of Dar Es Salaam, 2019) Kachira, John Peter
    The sites with good wind energy conditions in Tanzania have motivated some local craftsmen to manufacture wind turbines using local and imported materials. However, some studies have shown that these turbines have low performance. In this study, theoretical approach has been carried out to assess the influence of TSR, solidity and Re on the aerodynamic performance of nine selected locally fabricated wind turbines in Tanzania. Three manufacturing centers namely, Dar es Salaam, Singida and Makambako were selected and three different HAWT rotor blades from each center were put under testing. Their respective rotor radii and chord widths were measured and used to determine their TSR, solidity and Re. The measured TSRs were 0.63, 0.70, 0.79, 0.90, 1.57, 2.09, 2.51, 3.14, and 4.19. Unlike 4.19, the rest values were below the recommended range between 4 and 10 for which WECS are recommended to generate large scale electricity. The respective measured solidities were, 0.90, 0.10, 0.13, 0.17, 0.18, 0.28, 0.88, 1.07 and 1.22. These solidities were found to be above the proposed range between 0.01 and 0.05 for which WECS are designed to generate large scale electricity. These high solidities lead into high torques reducing rotational speed of the WECS. The measured Res were 86,030, 99,265, 100,589, 102,574, 125,736, 138,972, 145,589, 145,589 and 152,207. These Re values are below the standard Re which is at least 6 110 implying that they exhibit turbulent flow with high level of drag coefficient that influences low performance of the WECS. The 3 - bladed wind turbine from Matiya in Singida was found to have good TSR of 4.19 though its solidity was found to be above the recommended standard values range. It needs an optimization of its chord and radius to improve its efficiency. Therefore, these wind turbines can only generate small scale electricity due to their poor aerodynamic performances
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    BER of OFDM System With Multiple NBI Rejection Cascade Complex Coefficient Adaptive IIR Notch Filter
    (Scientific Research, 2012-08-16) Mvuma, Aloys N.
    In this paper, rejection of multiple narrowband interferers in a binary phase shift keying modulated orthogonal fre- quency division multiplexing (BPSK-OFDM) system is investigated. The BPSK-OFDM system in consideration oper- ates in an additive white Gaussian noise (AWGN) channel. A cascade complex coefficient adaptive infinite impulse response (IIR) notch filter with gradient-based algorithm is used to reject the interferers. Bit error ratio (BER) perform- ance of the system is studied and a general closed-form expression is derived assuming negligible steady-state leakage NBI and by estimating the decision variable as Gaussian distributed based on Central Limit Theorem (CLT). Depend- ence of the BER performance on the notch bandwidth coefficient is demonstrated by the analysis. Extensive simulation results are included to substantiate accuracy of the analysis.
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    Characterisation of Titanium Alloy Processed By Constrained Bending and Straightening Severe Plastic Deformation
    (The University Of Johannesburg, 2020) Mwita, Wambura Mwiryenyi
    Most Severe Plastic Deformation (SPD) processes lack both the capability for continuous process and the homogeneity of tailored material properties in processed samples. These challenges have limited the adaptation of SPD technology to process titanium alloys for biomedical and structural applications. This thesis presents microstructural and mechanical characterization of Ti6Al4V titanium alloy processed by a Constrained Bending and Straightening (CBS) SPD technique. The proposed CBS method was intended for a continuous process of titanium sheets with improved magnitude and homogeneity of the entailed strain, hardness and tensile properties. The CBS process tool was designed and fabricated in the University of Johannesburg workshop. The tool was used to process Titanium Alloy Grade 5 (Ti6Al4V) sheets at a combination of (2, 4, 6) passes (N) and (6 mm, 12 mm) feeds (F) designated as N2F6, N4F6, N6F6, N2F12, N4F12 and N6F12. Sub-samples were cut from the processed sheets. The samples were prepared, and their respective microstructural analysis, hardness and tensile tests were performed. A numerical model for the CBS process was built and simulated with ABAQUS Standard Finite Element Analysis (FEA) method. The model was used to predict the magnitude and the homogenity of the Effective Plastic (EP) strain, the tensile yield strength and the hardness of the material. The simulation results were validated with the experimental data. The experimental results showed that vi comparing with the As Received (AR) samples, the processed samples showed a decrease in the average grain size from 10µm to 3µm, together with the formation of new finer subgrains. The tensile strength, the yield strength and the hardness of the material increased by 29.3%, 33.5% and 24.4%, respectively. The values of these material properties at the F6 feed were higher than those at the F12 feed. The simulated results showed that the maximum mean EP strain of 2.87 induced in the material correlated with the highest strain homogeneity that corresponded to the lowest Coefficient of strain Variation (CV) of 18.9%. A comparison of the results from both methods on the yield strength and the hardness showed a direct correlation at the N2 and the N4 passes. A relative inverse correlation was observed at the N6 pass due to the saturation of the material hardening and the onset of yielding. Results from this study have quantitatively shown that the CBS method performed well the intended work. However, this method needs desirable improvement at a commercial level before it is viable as an alternative method for the continuous production of the titanium alloy sheets enhanced with the homogeneous microstructural and mechanical properties
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    Characterizing Hydrological-Sensitive Areas of The Kinyerezi River SubCatchments in Dar Es Salaam, Tanzania Using The Topographic Index Approach.
    (IWA Publishing, 2023) Swilla, Livingstone; Katambara, Zacharia; Lingwandaa, Mwajuma
    Several areas experience frequent floods due to anthropogenic activities. Among them, is the Dar es Salaam city, which experiences frequent floods along the Msimbazi River, whose flows originate from different tributaries including the Kinyerezi River. This study aims to evaluate the hydrological-sensitive areas of the Kinyerezi River sub-catchments using topographic index values (λ*) that enable the identification of areas with a higher probability of generating surface runoff. A digital elevation model was utilized to delineate the Kinyerezi River sub-catchment characteristics using ArcGIS 10.4. Soil infiltration rates (Ks) on selected open places were determined using a Guelph permeameter. Soil particle size distributions were analyzed and the λ* values were evaluated. The results showed the particle size distribution contains sand and silt-clay ranging from 46 to 84% and 16 to 53%, respectively. The Ks ranged from 0.6 to 7.8 mm/h while the sub-catchment KS3 scored the highest λ* value of about 10.7. Hence, there is a higher probability for generating surface runoff. Sub-catchment KS16 scored the smallest λ* value of 5.7, perceived to generate less surface runoff. Low-impact development practices capable of capturing runoff and enabling infiltration, evaporation, and detention should be employed in sub-catchments with higher λ* values.
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    Chemical Characterization of Pumice Material Sourced from Mbeya, Tanzania
    (MUST, 2025-02) Nyangi, Patrice
    Pumice, a lightweight volcanic material abundantly available in Mbeya, Tanzania, is underutilized and often discarded following excavation activities. In most construction projects within the region, conventional materials like clay soil, river sand, normal-weight aggregates, and cement are pre-dominantly used, leaving the potential of pumice largely unexploited. This study presents a comprehensive chemical characterization of pumice sourced from two locations, MUST main campus (Sample A) and Wimba (Sample B), to assess its suitability as a supplementary cementitious material (SCM). Energy Dispersive X-ray Fluorescence (EDXRF) analysis revealed that Sample A contained 70.3% SiO₂, 17.9% Al₂O₃, and 3.53% Fe₂O₃, while Sample B had 71.3% SiO₂, 17.3% Al₂O₃, and 3.38% Fe₂O₃. The combined SiO₂, Al₂O₃, and Fe₂O₃ content for both samples exceeded the 70% ASTM C618 threshold for pozzolanic materials, confirming strong pozzolanic properties. Additionally, K₂O was 5.21% in Sample A and 5.05% in Sample B, while CaO was 0.667% and 0.763%, respectively.SO₃ was detected at 0.448% (Sample A) and 0.482% (Sample B), and TiO₂ at 0.528% and 0.507%, respectively. Na₂O and MgO were not detected. The high levels of SiO₂ and Al₂O₃ suggest strong pozzolanic properties, while the low CaO content indicates that pumice would function primarily as a pozzolanic additive rather than a primary binder. Consequently, these findings confirm that pumice is better suited as a supplementary cementitious material (SCM) and filler rather than a complete replacement for cement. By partially replacing cement with pumice, it could be possible to reduce the carbon footprint, contributing to more sustainable construction practices.