ASTU ETD

Adama Science and Technology University Library Electronic Theses & Dissertations (ASTU- ETD) is a new digital institutional repository system that collects, preserve and distribute the scholarly output of the university, mainly postgraduate Electronic Thesis and Dissertation (ETD), articles, proceedings. The system is dedicated to help users to find all the information they might require in order to format and successfully submit their graduate thesis, dissertation and publications electronically. The user friendly web interface enables to maximize & optimize the resource sharing among ASTU different Colleges.

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Recent Submissions

Harnessing Chromogenic Bacteria for Eco-Friendly Textile Dyeing: Pigment Production and Process OptimizationThesis
(ASTU, 2026-01) Birhanu Zeleke
Microbial pigments are emerging as sustainable alternatives to synthetic dyes due to their environmental compatibility and potential for circular bio-economy applications. This study focused on the identification of potent pigment-producing bacterial isolates, the use of agro waste substrates as low-cost substrates, and the optimization of culture parameters to enhance pigment yield. The study systematically explored pigment-producing bacterial isolates from environmental samples, employing morphological, biochemical, and MALDI-TOF analyses for identification. Eco-physiological tolerance was assessed using the one-variable-at-a-time approach, while culture optimization was conducted through Plackett–Burman Design followed by response surface methodology. Agro-waste extracts as low-cost substrates were evaluated via optical density measurements, and pigments were extracted using organic solvents. Pigments were characterized using UV-Vis spectroscopy, LC-MS, and ATR-FTIR. The pigments' stability under varying stressor conditions was assessed by monitoring absorbance at their characteristic wavelengths. Fabrics dyeing were conducted using immersion technique. Dye exhaustion and fixation to fabrics were evaluated via absorbance method after washing and exposure to sunlight. From purified colonies on streak plates, six isolates; namely: Acinetobacter sp., Exiguobacterium aurantiacum, two Kocuria spp. (from different samples), Micrococcus luteus, and one unidentified strain, exhibited chromogenic potential. Among the chromogenic isolates screened, Micrococcus luteus exhibited the highest pigment yield (1.47 g/L) under orange-waste extract cultivation, likely due to the isolate's inherent carotenoid biosynthetic capacity, stress tolerance, and efficient substrate utilization. Optimization of pigment production by Exiguobacterium aurantiacum using tomato-waste extract revealed that agitation rate, pH, and yeast extract concentrations were the most significant factors influencing culture growth (p<0.001), leading to 1.6-fold yield increment compared to un-optimized conditions. The characteristic UV-Visible absorbance peaks (400 550 nm) indicated the pigments are likely carotenoid compounds with functional group signatures (O–H, C–H, C=C, C=O) from infrared spectra analyses. The LC-MS analyses further resolved pigment mixtures, provided molecular weights and fragmentation patterns, indicating pigment heterogeneity. Stability assays of Micrococcus luteus pigment indicated susceptibility to oxidative and thermal stress, while dyeing trials demonstrated vibrant and uniform coloration with moderate fixation on fabrics. While microbial pigment production has been widely reported, existing studies predominantly rely on synthetic media. The present study is fundamentally novel, integrating systematic screening, agro-waste valorization, and multivariate statistical optimization, marking the first such effort in Ethiopia. The findings highlight Micrococcus luteus as a robust candidate for scalable, eco-friendly pigment production under low-cost sustainable culture conditions. The findings highlight the feasibility of low-cost, eco-friendly microbial pigments for industrial applications as promising alternatives to synthetic dyes.
Experimental Study And Optimization Of Welding Parameters Of V Groove Joints On Aisi4130 Material Using Shielded Arc WeldingThesis
(ASTU, 2026-01) Korme Yadeto
Shielded metal arc welding (SMAW) is widely employed in heavy industries to join materials; however, it frequently ignores delicate connections that impair weld quality. AISI 4130 chromium-molybdenum alloy steel has unique weldability challenges, demanding a rigorous approach to welding parameter optimization with modern technologies. The objective of this study optimizes shielded arc welding parameters for V-groove joints in AISI 4130 alloy steel to maximize ultimate tensile strength (UTS), hardness, bending strength, and compressive strength. It also experimentally validates the predictive capability of Response Surface Methodology (RSM). The study result discovered that welding current is the most critical component in producing robust mechanical characteristics at RSM optimized parameter values of 200 A, 2.5 mm, and 70°. The study also discovered complicated non-linear interactions, indicating that synergistic parameter combinations are the source of optimum features. Experimental validation showed the mechanical properties boosted capacity, with a 2% average improvement. RSM-optimized settings (200 A, 2.5 mm, 70°) resulted in strong mechanical characteristics (UTS: 1110 MPa, hardness: 112 HRB, compressive strength: 860 MPa, and bending strength: 840 MPa). The models' dependability is demonstrated by their low prediction errors (4.18% for RSM). In this work, the selection of SMAW parameters is moved from empirical approaches to a data-driven science. RSM integration creates a reliable and repeatable foundation for precision manufacturing. With this method, high-integrity AISI 4130 welds with customized, exceptional mechanical qualities that are appropriate for crucial structural applications can be produced. For AISI 4130 steel, welded V-groove joint integrity and durability in critical applications hinge on key mechanical properties—ultimate tensile strength, hardness, bending/compressive strength, and impact toughness—that guide RSM-optimized shielded metal arc welding parameters for ASTM-compliant, base metal-exceeding performance.
Synthesis of Vanadium Oxide (V₂O₅) Nanoparticles for Degradation of Methylene Blue DyeThesis
(ASTU, 2025-06) Demise Sorie
Vanadium pentoxide (V₂O₅) nanoparticles were successfully synthesized using ammonium metavanadate as a precursor and Laggera tomentosa leaf extract as a natural reducing agent through a sol–gel method. The obtained nanoparticles were characterized to investigate their morphology, optical properties, functional groups, and structural features using ultraviolet visible diffuse reflectance spectroscopy (UV–vis DRS), Fourier transform infrared spectroscopy (FT–IR), Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The photocatalytic performance of the V₂O₅ nanocomposite was evaluated under visible light irradiation for the degradation of methylene blue (MB), with optimization of both catalyst dosage and contact time.
Exploring Performance of Metamaterial Emitters for Applications of Energy Harvesting and Gas Sensing: Modeling and Simulation ApproachThesis
(ASTU, 2026-01) Gemechis Mathewos
This dissertation presents a theoretical investigation into the spectral performance of a multilayer and grating metamaterial composed of tungsten (W) and Aluminumnitride (AlN), hafnium dioxide (HfO₂) designed to enhance thermophotovoltaic (TPV) energy conversion efficiency. Utilizing advanced electromagnetic simulations based on Maxwell‘ s equations, the study explores the optical properties of a W/HfO₂/W metamaterial structure, focusing on its ability to produce high emissivity within the wavelength range of 1.5 to 2.0 μm optimal for interfacing with InGaAsSb TPV cells. The results demonstrate that the metamaterial achieves an average emissivity exceeding 96%, with a peak of 99.9%, primarily driven by resonant mechanisms such as surface plasmon polaritons and magnetic polaritons. The design exhibits polarization independence and maintains high performance across incident angles of 0° to 60°, indicating robustness for practical applications. Furthermore, the study assesses the impact of material selection and structural parameters on emissivity characteristics, emphasizing the potential of engineered metamaterials to significantly improve thermal radiation control. The findings suggest that the proposed W/HfO₂/W metamaterial has promising implications for advancing high-efficiency TPV systems, contributing to sustainable energy solutions through optimized thermal emission engineering. Additionally, it presents the design and simulation of a terahertz metamaterial-based gas sensor aimed at detecting toxic atmospheric gases such as ozone (O₃) and nitric oxide (NO). Utilizing a metal-dielectric metal (MDM) structure composed of tungsten and hafnium dioxide, the sensor exhibits dual resonance frequencies with absorption rates approaching 99%. Finite Element Method (FEM) simulations demonstrate high sensitivity to variations in refractive index, with sensitivities up to 4.58 THz/RIU and a figure of merit exceeding 11.82/RIU. Distinct resonance shifts corresponding to different gases affirm the sensor‘s potential for real time, selective gas detection. The findings underscore the effectiveness of metamaterials in environmental monitoring applications and lay the groundwork for developing practical, hi gh-performance gas sensors for air quality assessment.
Impacts of Land Use/Land Cover Change on Sediment Yield and Stream flow to Rift Valley Lakes Basin, A Case Study on Lake Ziway, Ethiopia.Thesis
(ASTU, 2025) Alazar Abdulkadir
This study investigates the impacts of Land use/land cover change on sediment yield and stream flow in the Lake Ziway watershed, Ethiopia. Land Use/Land cover changes in this region have been driven by rapid population growth, urbanization, and agricultural expansion, which have significantly altered the natural landscape. The research employs the Soil and Water Assessment Tool (SWAT) model to analyze hydrological responses to these land use/land cover (LULC) changes over the past few decades. The methodology involves multiple steps, including LULC classification using high-resolution Sentinel-2 imagery, hydrological model setup, and calibration using historical streamflow data from the Meki and Ketar gauging stations. The SWAT model is particularly effective for simulating hydrological processes, allowing for detailed analysis of water flow and sediment transport across the watershed. The result indicates that significant spatial variability in sediment yield within the lake Ziway catchment in respond to LULC change. The highest sediment yields were recorded in sub-basins characterized by steep slopes and intensive agricultural practices, with values exceeding sustainable thresholds. These findings suggest that certain areas are highly susceptible to erosion, which can lead to increased sedimentation in Lake Ziway, impacting water quality and aquatic ecosystems. The study also highlights the critical relationship between land cover dynamics and hydrological responses, emphasizing the necessity for integrated watershed management approaches. The insights gained from this research underline the importance of implementing targeted soil and water conservation measures, particularly in high-risk erosion zones. In conclusion, this study underscores the significance of integrating LULC dynamics with hydrological modeling for effective watershed management. Recommendations for future actions include adopting sustainable land management practices, enhancing monitoring efforts, and developing policies that address the impacts of land cover change. By prioritizing these strategies, it is possible to mitigate the adverse effects of sediment yield and improve the overall health of the Lake Ziway ecosystem.