http://ir.bdu.edu.et/handle/123456789/1844 2026-08-27T19:24:41Z http://ir.bdu.edu.et/handle/123456789/17078 Optical Properties of Copper Nanoparticles: A Systematic Review Muhabaw, Assefa Scientific interest in nano particles of various shapes and morphology is growing proportionally. Besides the distinct size characteristic, properties of nano particles vary widely with alteration of structural and morphological features. Metallic nano particles’ characteristics are mostly determined by their shapes and sizes. These shape-dependent nano particles hold an impressive potential for to be used in numerous scientific technologies with promising applications. Due to their small size, metallic nano particles have special optical, magnetic, and electrical, strength, surface area, sensitivity, and stability features. Surprisingly, the phase change occurs when bulk materials are converted into nano particles, which means that materials that were previously non-magnetic become magnetic at the nanoscale. Because of their unique features, nanoscale matter is a separate form of matter from the solid, liquid, gaseous, and plasma states.Copper nano particles have drawn tremendous attention over other metals due to their unique and fascinating property known as Localized Surface Plasmon Resonance (LSPR). Mie theory can describe the optical properties of copper nano particles when the size of the nano particle is not too small.In this study, a critical overview the optical properties of copper nano particles from a theoretical approach (Mie scattering theory) and experimental investigations were intensively reviewed.Additionally, classifications, synthesis techniques, characterization methods of nano particles, and applications of copper nano particles in various fields are offered. 2024-10-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/17063 Climatic Extremes under Climate Change Scenario Over Ethiopian River Catchments Mulugeta, Aregay This doctoral research presents a comprehensive analysis of hydroclimatic extremes across Ethiopia’s eight major river basins, addressing critical gaps in understanding compound climate risks in tropical highland regions. The study employs an innovative tripartite framework integrating ground-based observations from 17 WMO-certified meteorological stations and 28 hydrological gauging stations, high-resolution satellite data from TerraClimate (4 km resolution), and ECMWF ERA5 reanalysis data (0.25° resolution) spanning the period 1986-2023. Through the application of advanced statistical methodologies including standardized drought indices (SPI, SPEI, SSI), Mann-Kendall trend analysis, Sen’s slope estimator, and adapted crossing theory for heatwave characterization, the research reveals profound transformations in Ethiopia’s climate system. The investigation demonstrates a statistically significant intensification of meteorological, agricultural, and hydrological droughts across all basins, with frequency increases of 40-60% since the 1980s. The Abay, Awash, andWabi Shebelle basins emerge as particular hotspots, showing the most pronounced drying trends. Large-scale climate teleconnections, particularly ENSO and Indian Ocean Dipole phases, explain 68-85% of interannual drought variability, with basin-specific sensitivity patterns reflecting Ethiopia’s complex physio-graphic diversity. Flood analysis reveals increasing frequency and magnitude of extreme precipitation events, with flood magnitude increasing by 25-40% since the 1980s. The research documents accelerating drought-to-flood transitions, with soil moisture memory effects reducing transition times by 2.3 days per decade, fundamentally challenging conventional water management approaches that treat these phenomena discretely. Thermal extremes analysis identifies unprecedented warming trends, with heatwave frequency increasing by 150% since the 1990s. The research reveals an ”elevation paradox” whereby Ethiopian highlands are warming faster than lowlands, contradicting global patterns and climate model projections. This anomalous warming is driven by reduced cloud cover (Δalbedo = -0.11), expanding foehn winds, and decreasing atmospheric humidity at higher elevations. Climate projections using statistical downscaling of CMIP6 models under SSP scenarios indicate substantial intensification of all climate extremes through 2050, with meteorological and hydrological droughts projected to increase by 50-200%, flood magnitudes by 30-60%, and heatwave duration by 3-5 days per decade. The research particularly highlights growing risks of compound events, including concurrent drought-heatwave conditions and rapid transitions between hydrological extremes. Theoretical contributions include the development of an integrated framework for analyzing compound climate extremes, the identification of elevation-dependent climate responses that challenge conventional climate theory, and documentation of non-stationarity in teleconnection relationships. Methodological advances feature the novel adaptation of crossing theory for tropical highland heatwave analysis and implementation of a hybrid statistical downscaling approach optimized for compound extreme projection. Practical applications include specific recommendations for updating reservoir operation rules, adjusting agricultural calendars, implementing heat health warning systems, and revising infrastructure design standards. The basin-specific characterization of climate risks provides a scientific foundation for targeted adaptation strategies, with the research already informing improved early warning systems in the Awash Basin pilot project achieving 92% accuracy in drought onset detection. This research provides the most comprehensive assessment to date of hydroclimatic extremes in Ethiopia’s river basins, offering both scientific insights for climate resilience planning and methodological frameworks for similar assessments in other tropical highland regions. The findings underscore the urgent need for transformative adaptation approaches that address the interconnected nature of climate risks in one of the world’s most vulnerable regions. 2026-01-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/17062 Kinetic Monte Carlo-Guided Green Synthesis and Theoretical Investigation of Zno Nanoparticles for Solar Cell Efficiency Enhancement Natinael, Tezana This study evaluates the influence of Ocimum lamiifolium leaf extract (OLE) concentration on the green synthesis of zinc oxide nano particles (ZnO NPs) and their performance as an Electron Transport Layer (ETL) in perquisite solar cells (PSCs). Synthesized across five extract-to precursor ratios (1:2 to 3:2), the ZnO NPs followed a parabolic size trend dictated by competitive Ostwald ripening and steric crowding kinetics, which were modeled using atomistic Kinetic Monte Carlo (kMC) simulations. The 2:2 ratio achieved optimal stoichiometric equilibrium, yielding highly stable, pure nano particles with a 3.19 eV optical bandgap. This sample demonstrated an experimental crystalline core size of 10.80 nm (XRD) and an optical confinement size of 12.10 nm (Effective Mass Model), aligning exceptionally well with the kMC prediction of 10.24 nm (18.16% difference). EDX confirmed high purity with a minor 2.04 wt.% carbon signature from biomolecular capping. SCAPS-1D photovoltaic simulations proved that using this optimized ZnO (2:2) sample as an ultra-thin 20 nm ETL minimizes interfacial recombination and resistance, achieving a peak power conversion efficiency (PCE) of 16.03% (Jsc = 23.93 mA/cm2, Voc = 1.11V). Increasing the ETL thickness to 90 nm systematically degraded performance due to bulk carrier trapping. This work highlights kMC validated, biogenic ZnO as a sustainable, efficient architecture for next-generation PSCs. 2026-06-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/17053 Mechanisms to Increase the Slew Rate and Open Loop Gain of a Two Stage Cmos Op Amp Mahliet, Tesfa The demand for low power, low voltage devices is increasing at a faster rate as a result of wider implementation of smaller-sized, portable, and hand held devices in the telecommunication and entertainment industries. This research study focuses on the mechanism to increase the slew rate and DC open loop gain of the two stage CMOS op-amp. We have designed the two stage CMOS op-amp, which operates at 2.0V power supply using 0.5 m CMOS technologies. The simulations were done using OrCAD PSPICE software and we have found that the design has high slew rate: -68.11V s, 72.06V s and high DC open loop gain of 95.29dB, widest UGB and PM of 11.24MHz and 84.62o, respectively. Thus, this design will be of highly capable candidate for portable and hand-held CMOS op amp devices. 2026-06-29T00:00:00Z