http://ir.mu.ac.ke:8080/jspui/handle/123456789/65 Mon, 14 Sep 2026 12:03:06 GMT 2026-09-14T12:03:06Z http://ir.mu.ac.ke:8080/jspui/handle/123456789/10489 Title: An intelligent model and simulation of high voltage and medium voltage transmission line protection scheme using time overcurrent relay optimization settings: a case of Rwanda power network Authors: Ntambara, Boniface; Wambua, Paul; Simiyu, Sitati; Byiringiro, Jean Bosco Abstract: This paper presents an optimized inverse-time overcurrent relay (OCR) setting and coordination methodology for interconnected high-voltage and medium-voltage (HV/MV) transmission systems, validated on a real 110 kV/15 kV utility substation network. Analytical feeder impedance equivalences and phase-to-phase fault current models were developed to evaluate relay performance under multiple fault locations ranging from 0% to 100% of feeder length. Standard inverse (SI), very inverse (VI), and extremely inverse (EI) IEC overcurrent relay characteristics were applied to both incoming and outgoing feeders. The study incorporates practical power system parameters, including short-circuit MVA, positive and negative sequence impedances, X/R ratio, transmission line length, current transformer (CT) ratios, full-load current, line capacity, grid frequency, and real power. Relay pickup currents and a fixed time multiplier setting (TMS = 0.05 s) were carefully selected to ensure safe, reliable, and rapid fault clearance. Fault current levels at each feeder location were computed based on feeder impedance variation, CT ratios, and pickup settings to determine optimal relay operating times and coordination intervals. Simulation results demonstrate that the proposed OCR coordination scheme achieves fast and selective fault isolation, with coordination interval times of 0.062–0.0927 s, 0.0720–0.0949 s, and 0.0661–0.0764 s for extremely inverse, very inverse, and standard inverse relay characteristics, respectively. The extremely inverse characteristic provided the fastest response for remote faults, while standard inverse relays ensured stable operation near the substation. MATLAB/Simulink-based validation confirms improved relay selectivity, reduced coordination delays, and effective mitigation of cascading outages. The results indicate that properly optimized inverse-time OCRs can provide a cost-effective, reliable, and practical protection solution for HV/MV transmission networks, particularly in developing and interconnected power grids where simplicity and coordination speed are critical. Sun, 01 Feb 2026 00:00:00 GMT http://ir.mu.ac.ke:8080/jspui/handle/123456789/10489 2026-02-01T00:00:00Z http://ir.mu.ac.ke:8080/jspui/handle/123456789/10475 Title: Energetic particles in space and earth science: propagation, interaction, and atmospheric effects Authors: Maritim, Joseph K. Abstract: Energetic particles, originating from galactic cosmic rays (GCRs), solar energetic particles (SEPs), and trapped radiation belt populations, play a crucial role in shaping planetary environments. These high-energy protons, electrons, and heavy ions traverse the heliosphere, interact with interplanetary magnetic fields, and produce complex cascades when colliding with Earth’s atmosphere. This paper combines theoretical modeling, Monte Carlo–inspired GEANT4-like yield tables, and simulation of Bethe–Bloch stopping power to investigate energetic particle propagation, atmospheric ionization, and implications for space weather. Our findings reveal that density-effect corrections and shell corrections significantly alter proton energy loss curves, while GEANT4-like lookup yields realistic ionization profiles vs altitude. These results advance predictive models of radiation hazards, ionospheric variability, and space weather event Sat, 01 Aug 2026 00:00:00 GMT http://ir.mu.ac.ke:8080/jspui/handle/123456789/10475 2026-08-01T00:00:00Z http://ir.mu.ac.ke:8080/jspui/handle/123456789/10470 Title: Natural fibre–reinforced starch biocomposites and their effects on the material mechanical properties: a review Authors: Kibet, Tabitha; Githinji, David N.; Nziu, Patrick Abstract: Research on biodegradable materials has gained significant attention due to increasing environmental awareness. Starch, as a biodegradable polymer readily available from agricultural resources, is a promising candidate for biocomposite production. Starch-based films, though exhibiting low mechanical strength, can be enhanced using various plasticizers at elevated temperatures with shear, resulting in a deformable thermoplastic material known as thermoplastic starches. The tensile properties of these starch-based composites can be further improved by incorporating fibres, making them more suitable for a range of applications. This review highlights the significance of biodegradable materials as sustainable alternatives to synthetic plastics, driven by environmental concerns. It focuses on natural fibre–reinforced biopolymer composites, particularly those based on starch, which exhibit improved properties. The review also covers natural fibres as reinforcement, starch as a biopolymer component and potential applications of these composites and suggests directions for future research. The results of this compilation show that natural fibres have a significant influence on the characteristic of the fabricated composites. Sun, 01 Feb 2026 00:00:00 GMT http://ir.mu.ac.ke:8080/jspui/handle/123456789/10470 2026-02-01T00:00:00Z http://ir.mu.ac.ke:8080/jspui/handle/123456789/10447 Title: Analyzing incoherence and inconsistencies in data utilization within maintenance operations for critical equipment in the weaving section of textile manufacturing processes Authors: Bett, Kipchumba; Chemweno, Peter; Nganyi, Eric; Ochola, Jerry Abstract: In the context of textile manufacturing’s weaving section, efficient maintenance operations play a pivotal role in upholding critical equipment’s peak performance and longevity. However, inconsistencies in data utilization during maintenance can lead to equipment failures, downtimes, and decreased efficiency. To address this, this study endeavors to scrutinize these data dis parities, focusing on the weaving section’s essential machinery. The objective encompasses identifying failure patterns, gauging parameter impacts on system components, and proposing personalized maintenance strategies based on failure characteris tics. The study employed the Weibull distribution plot to analyze data from 19 distinctive components, with shape (β) and scale (η) parameters elucidating failure trends, distinguishing early-life and wear-out failures. The Anderson-Darling (AD) statistic validated Weibull fitting. Visual aids and charts presented findings effectively. Analysis showcased distinct failure patterns across system components, where shape parameters exceeding 1 denoted wear-out failures, and scale parameters re vealed equipment lifespans. The study emphasized the necessity of bespoke maintenance approaches in response to equipment failure traits. Tailoring strategies for early-life and wear-out failures is essential. The Weibull analysis aids in pinpointing crucial maintenance junctures, optimizing schedules, and enhancing equipment reliability. This study’s contribution lies in ele vating equipment dependability, curbing downtimes, and augmenting operational efficiency in textile manufacturing processes. Recommendations encompass tailored maintenance strategies, prioritized preventive measures for wear-out-prone components, comprehensive craftsman training, and exploring predictive techniques leveraging sensor data and AI. Tue, 01 Aug 2023 00:00:00 GMT http://ir.mu.ac.ke:8080/jspui/handle/123456789/10447 2023-08-01T00:00:00Z