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SSRN 2022年

作者： Desta, Takele Taye Teklemariam, Haimanot Mulugeta, Tewodros Department of Biology College of Natural and Computational Science Kotebe University of Education Addis Ababa Ethiopia Department of Forest Protection Ethiopian Environment and Forest Research Institute Addis Ababa Ethiopia

Eucalyptus is a fast-growing evergreen perennial tree. Attributable to its diverse economic values and a wide range of adaptations, the eucalyptus is commonly grown in tropical and subtropical environments. Eucalyptus is an economically important tree. However, the economic importance of eucalyptus ensued at the expense of undesirable ecological consequences. This qualitative study reports the advantages and disadvantages of eucalyptus woodlot establishment on the productivity of arable lands. In this study, 9 knowledgeable farmers were involved in an in-depth individual interview and 4 focus group discussions were made. Farmers have frequently reported the negative impact of eucalyptus plantations on the performance of the agricultural system. Eucalyptus imposes several problems in the agricultural system. It serves as a refuge for crop pests and pathogens such as aphids and rust. Besides, shade suppresses the development of understory and adjacent crops, pastures, fodder, and other species of native trees and shrubs if planted mixed. In addition to its impact on deteriorating soil fertility, structure, and moisture, it drains wetlands, springs, and streams and reduces the flow of rivers. Eucalyptus has increasingly replaced or suppressed the growth of eco-friendly native trees and shrubs traditionally used as hedges, windbreaks, fodders, shelters for wild animals, and enhancers of soil fertility. Nevertheless, farmers acknowledged the importance of eucalyptus as construction material, source of fuelwood and charcoal, and income. To make the best use of eucalyptus woodlots without imposing adverse effects on agroecology, farmers have suggested that plantation sites should be marginally suitable for crop and livestock production. The expanded plantation needs contracting by removing a significant proportion of the established eucalyptus woodlots. Plantation of eucalyptus around watering points should be discouraged. Fast-growing, resilient, and eco-friendly tree spe

关键词： Crops

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Vegetation Structure and Regeneration Status of the Western Escarpment of the Rift Valley of the Gamo Zone, Southern Ethiopia

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Open Journal of Ecology 2022年第1期12卷 94-111页

作者： Temesgen Dingamo Serekebirhan Takele Zerihun Woldu Sebsebe Demissew Biodiversity Conservation and Research Center College of Natural Science Arba Minch University Arba Minch Ethiopia Department of Biology College of Natural Science Arba Minch University Arba Minch Ethiopia Department of Plant Biology & Biodiversity Management College of Natural & Computational Sciences Addis Ababa University Addis Ababa Ethiopia

Understanding the structure and regeneration of forest resources contributes to identifying the elements of diversity, endemism, threatened and endangered species. This study was conducted in the western escarpment of the Rift valley of the Gamo Zone, Southern Ethiopia. The main objective was to investigate structure and regeneration status of the study area. A systematic sampling method was used to collect vegetation data from a total 102 quadrats, each 20 × 20 m (400 m²) and five 1 × 1 m (1 m²) sub-quadrats were established at the four corners and at the centre for sapling and seedling estimation. Tree and shrub species were listed;Height (H ≥ 1.5 m) and DBH ≥ 2 cm were measured and recorded. R-statically software and Microsoft Excel were used to record and analyse the data. A total of 126 plant species belonging to 43 families and 90 genera were identified. The most dominant families were Fabaceae, followed by Anacardiaceae and Euphorbiaceae. Most frequent species were Euclea divinorum (84.3%), followed by Rhus natalensis (83.3%), Terminalia brownii (74.5%). DBH class ≤ 5cm had highest density (63.6%) and DBH ≥ 25.1 cm had the lowest density (0.87%). Three population patterns have been observed;inverted J, J-shaped and irregular shaped. 93% of species had IVI values b/n 1 - 4, 65% of species IVI values < 1% and 7% of species had IVI values ≥ 5.28. Pappea capensis, Combretum molle, Terminalia brownii, Euclea divinorum had highest IVI values. In the vertical stratification, lower story was 91.3% of the individuals. Only a few species contributed to the high density of saplings (440.2/ha) and seedlings (825.49/ha) while most had very little or no saplings and seedlings at all. Thus, in order to revert the current forest structure and regeneration to the previous natural state, it is considered important to minimize the influence of the human interference, grazing and raising awarene

关键词： Importance Value Index Regeneration Seedling/Sapling Vegetation Structure

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Detection of land use/land cover and land surface temperature change in the Suha Watershed, North-Western highlands of Ethiopia

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Environmental Challenges 2022年 7卷

作者： Yeneneh, Nigussie Elias, Eyasu Feyisa, Gudina Legese College of Natural and Computational Science Addis Ababa University Addis Ababa Ethiopia College of Agriculture and Natural Resource Management Debre Markos University Debre Markos Ethiopia

Human-induced land use land cover changes resulted in adverse impacts on the environment at various spatial and temporal scales. The Highland regions of Ethiopia are typical examples of these phenomena. The objective of this study was to analyze spatiotemporal changes in land use/ land cover and their impacts on land surface temperature in the suha watershed, northwestern highlands of Ethiopia. Multi-temporal Landsat images (1985–2019) were used to analyze LU/LC changes and LST using GIS and remote sensing techniques. Image preprocessing, supervised classification, accuracy assessment, and change detection were conducted to identify LU/LC classes, area coverage, and their transitions. Thermal bands of these satellite images were also used to extract LST. Significant changes in land use/land cover (spatial and temporal) were observed in the suha watershed during the study periods. Agricultural land has got the largest proportion in all study periods. The barren land and built area also expanded greatly in 35 years period. Agricultural land has increased by 15417.6 ha (34.8%) and bare land has expanded by 5297.2 ha (373.6%). However, grazing and shrub lands were reduced by18568.4 ha (72.1%) and 3544.2 ha (47.6%), respectively. Spatial and temporal variation of LST was also observed in the same period. The highest mean values were found on impervious surfaces (built-up areas and bare land), and the lowest values were recorded on forest land. A negative correlation was found between LST and NDVI. Undesirable land use and land cover changes put greater pressure on environmental resources, resulting in an adverse effect on them. Therefore, to reverse this situation and create a balanced ecosystem, management strategies should be applied that mainly focus on soil conservation technologies in steep slope areas, improve afforestation and apply proper land-use policies. The outcomes of this research are useful in designing and implementing appropriate strategies that can addr

关键词： Landsat image LST, GIS & remote sensing LU/LC change Suha watershed

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Constraining viscous-fluid models in f(Q) gravity using cosmic measurements and large-scale structure data

arXiv

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arXiv 2024年

作者： Sahlu, Shambel Hough, Renier Abebe, Amare Centre for Space Research North-West University Potchefstroom South Africa Entoto Observatory and Research Center Space Science and Geospatial Institute Addis Ababa Ethiopia Department of Physics College of Natural and Computational Science Wolkite University Wolkite Ethiopia South Africa

This paper investigates the impact of bulk viscosity on the accelerating expansion and large-scale structure formation of a Universe in which the underlying gravitational interaction is described by f(Q) gravity. Various toy models of the f(Q) gravity theory, including power-law (f1CDM), exponential (f2CDM), and logarithmic (f3CDM) are considered. To test the cosmological viability of these models, we use 57 Hubble parameter data points (OHD), 1048 supernovae distance modulus (SNIa), their combined analysis (OHD+SNIa), 14 growth rate (f-data), and 30 redshift-space distortions (fσ8) datasets. We compute the best-fit values{Ωm, H0} and exponents {n, p, γ} including the bulk viscosity coefficient ζ0, through a detailed statistical analysis. Moreover, we study linear cosmological perturbations and compute the density contrast δ(z), growth factor D(z), growth rate f(z), and redshift-space distortion fσ8(z). Based on the Akaike Information Criterion (AIC) and Bayesian/Schwartz Information Criterion (BIC), a statistical comparison of the f(Q) gravity models with ΛCDM is made. From our statistical analysis of cosmic measurements, we found an underestimation of all models on the OHD data;therefore, statistical viability led us to weigh it in favor of SNIa data which resulted in the exponential (f2CDM) model without bulk viscosity being the most plausible alternative model, while on average the f1CDM model performed statistically the weakest. We also found that adding bulk viscosity did not improve the fit of the models to all observational data. Furthermore, from large-scale structure growth data, we found that all three models yield Γ > 6/11, which exceeds the value predicted by the ΛCDM model. © 2024, CC BY.

关键词： Gravitational effects

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Effect of chemical and biological additives on production of biogas from coffee pulp silage

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Scientific Reports 2023年第1期13卷 1-11页

作者： Getachew, Mengizam Tsegaye Hiruy, Andualem Mekonnen Mazharuddin, Majid Mohiuddin Mamo, Tadios Tesfaye Feseha, Temesgen Aragaw Mekonnen, Yedilfana Setarge Center for Environmental Science College of Natural and Computational Sciences Addis Ababa University Addis Ababa Ethiopia Institute of Atomic and Molecular Sciences Academia Sinica Taipei Taiwan Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 11529 Taiwan Institute of Physics Academia Sinica Taipei 11529 Taiwan Department of Chemistry National Taiwan University Taipei 10617 Taiwan

Energy is the foundation of the global economy and is essential to human survival. Nevertheless, more than 60% of it comes from fossil fuels. That is not a replenished and scarce source. However, a sizable amount of organic waste is generated every minute throughout the world and can be used as a raw material to produce renewable energy. Among them, Coffee processing generates a huge amount of solid and liquid waste that is organic and can serve as raw material for biofuel production. Since coffee beans and powder are Ethiopia’s main exports, coffee pulp is easily accessible. Therefore, the main goal of this project is to convert this waste, which largely consists of organic materials, into a valuable product called Methane. The purity and yield of methane productivity are significantly influenced by the type of additives we use. This work systematically investigates the effect of chemical and biological additives on the productivity and purity of the Biogas from the coffee pulp silage in batch systems under mesophilic temperature (38 °C) for different ensiling periods and additive proportions. The chemical additives recorded the maximum biogas production (2980 ml) at an ensiling period of 40 days with high purity of about 70% biogas. The minimum Biogas was recorded at the ensiling period of 10 days by the control (T1) treatments, which was 634 ml. This work proves that biological additives produced the highest quality and quantity of Biogas from coffee silage. © 2023, The Author(s).

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Correction: Evaluation of CORDEX Africa regional climate models performance in simulating climatology of Zarima sub-basin northwestern Ethiopia

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Environmental Systems Research 2025年第1期14卷 1-1页

作者： Kassahun, Meaza Ture, Kassahun Nedaw, Dessie Center for Environmental Science College of Natural and Computational Science Addis Ababa University Addis Ababa Ethiopia Department of Development and Environmental Management Studies College of Social Sciences and Humanities University of Gondar Gondar Ethiopia School of Earth Science College of Natural and Computational Science Addis Ababa University Addis Ababa Ethiopia

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Numerical Discrete-Domain Integral Formulations for Generalized Burger-Fisher Equation

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Applied Mathematics 2020年第3期11卷 137-145页

作者： Okey Oseloka Onyejekwe Beruk Minale Fikru Habtamu Tesfaye Amha Getenet Tamiru Bethelhem Mengistu Yohaness Demiss Nahom Alemseged computational science and Dynamics Systems Group Computational Science Program Addis Ababa University Arat-Kilo Campus Addis Ababa Ethiopia

In this study we use a boundary integral element-based numerical technique to solve the generalized Burger-Fisher equation. The essential feature of this method is the fundamental integral representation of the solution inside the problem domain by means of both the boundary and domain values. The occurrences of domain integrals within the problem arising from nonlinearity as well as the temporal derivative are not avoided or transferred to the boundary. However, unlike the classical boundary element approach, they are resolved within a finite-element-type discrete domain. The utility and correctness of this formulation are proved by comparing the results obtained herein with closed form solutions.

关键词： Burger-Fisher Equation Domain Integrals Boundary Element Finite-Element-Type Discrete Domain Boundary Integral Numerical Nonlinearity

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Correction: Spatio-temporal variability and trends of hydroclimatic variables at Zarima Sub-Basin North Western Ethiopia

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Environmental Systems Research 2025年第1期14卷 1-1页

作者： Zegeye, Meaza Kassahun Bekitie, Kassahun Ture Habtemariam, Dessie Nedaw Center for Environmental Science College of Natural and Computational Science Addis Ababa University Addis Ababa Ethiopia Department of Development and Environmental Management Studies College of Social Sciences and Humanities University of Gondar Gondar Ethiopia School of Earth Science College of Natural and Computational Science Addis Ababa University Addis Ababa Ethiopia

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computational Investigation of Corrosion Inhibition Properties of Hydrazine and Its Derived Molecules for Mild Steel

Quantum Engineering

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Quantum Engineering 2024年第1期2024卷

作者： Gebremeskel, Hiwet Meresa Welearegay, Meressa Abrha Nadew, Talbachew Tadesse Department of Chemical Engineering College of Engineering Addis Ababa Science and Technology University P.O. Box 16417 Addis Ababa Ethiopia Department of Chemistry College of Natural and Computational Science Mekelle University P.O. Box 231 Mekelle Ethiopia Department of Chemical and Food Engineering College of Engineering Kombolcha Institute of Technology Wollo University P.O. Box 208 Kombolcha Ethiopia University of South Africa Science Campus Florida Johannesburg South Africa

Corrosion of mild steel has gained a lot of attention by many industries and academia. This study was aimed to find the corrosion inhibition properties of hydrazine and its 11 derived molecules for mild steel using computational method, namely, the density functional theory with Beck 3-parameter Lee Yang and Parr functional along with the 6-311++G (d, p) basis set using simple quantum chemical parameters. The main quantum chemical parameters were energies of highest occupied and lowest unoccupied molecular orbitals and their energy gap, dipole moment, hardness, softness, electrophilicity index, the fractions of electrons transmitted, the change energy back-donation, electron-donating power, electron-accepting power, molecular electrostatic potential, and Fukui function as well as polarizability. The results indicated that hydrazine derivatives have good anticorrosion nature which is consistent with the experimental findings. Out of the 12 target inhibitor molecules, N′-(3-nitrobenzylidene) hydrazine carbodithioic acid (NBHCA) and N′-(4-dimethylaminobenzylidene) hydrazine carbodithioic acid (DABHCA) are the most effective inhibitors. According to the value of the quantum chemical parameters, EHOMO, ΔEgap, Χ, η, σ, ϵ, ΔN, α, and ΔEb-d DABHCA showed the top effective anticorrosion inhibitor, and by the value of the quantum chemical parameters, ELUMO, TE, ω-, and ω+ NBHCA showed an effective anticorrosion inhibitor. The quantum chemical parameter data showed that NBHCA and DABHCA are nearly equivalent in their values, which is consistent with experimental values. Furthermore, a multiple-linear regression equation was proposed as a quantitative structural activity relationship model to relate the calculated molecular descriptors of hydrazine derivatives to their experimental inhibition efficiencies obtained from literature. As a result, this model showed an excellent accuracy with an R-squared of 0.924 and this uses to predict inhibition efficiencies of another molecules

关键词： Hydrazine

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Improving the Accuracy of Honey Bee Habitat Mapping Using Ensemble Learning and Multi-Source Satellite Data in Google Earth Engine

SSRN

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SSRN 2024年

作者： Mengistu, Filagot Hailu, Binyam Tesfaw Abera, Temesgen Alemayehu Heiskanen, Janne Zeleke, Tadesse Terefe Johansson, Tino Pellikka, Petri K.E. College of Natural and Computational Sciences Center for Environmental Sciences Addis Ababa University P.O.Box 1176 Addis Ababa Ethiopia Department of Geosciences and Geography University of Helsinki P.O. Box 68 FI-00014 Finland School of Earth Sciences Addis Ababa University P.O.Box 1176 Addis Ababa Ethiopia Institute of Geophysics Space Science and Astronomy Addis Ababa University P.O.Box 1176 Addis Ababa Ethiopia Department of Environmental Informatics Faculty of Geography Philipps-Universität Marburg Deutschhausstraße 12 Marburg35032 Germany Finnish Meteorological Institute P.O. Box 503 HelsinkiFI-00101 Finland State Key Laboratory for Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan430079 China University of Nairobi Wangari Maathai Institute for Environmental and Peace Studies P.O. Box 29053 - 00625 Kangemi Kenya Helsinki Institute of Sustainability Science University of Helsinki P.O. Box 4 FI-00014 Finland

In semi-arid agro-pastoral environments of Africa, beekeeping is widely recognized as an important activity to improve and diversify livelihoods. Although the scientific identification of suitable honey bee (Apis mellifera ssps.) habitats may guide beekeepers to set up apiaries or to timely move honey bee colonies to exploit bee forage resources available in various landscapes, the characterization and mapping of bee forage plants is challenging. We evaluated how various data sources and classification algorithms in Google Earth Engine (GEE) affect the accuracy of honey bee habitat mapping in a semi-arid region of Ethiopia. Predictors derived from multi-source satellite data, such as high-resolution Planet imagery (P), Sentinel 1 RADAR (S1), Sentinel 2 multispectral (S2), and Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) were tested and best predictors were identified using Forward Feature Selection (FFS). Four machine learning algorithms (Gradient Tree Boost (GTB), Random Forest (RF), Classification and Regression Trees (CART), and Support Vector Machine (SVM)), all available in GEE, were compared and ensembled for honey bee habitat mapping. The results show that the highest accuracy is obtained by all four algorithms when combining P, S1, S2, and DEM compared to using predictors from a single data source or any other combinations. GTB had higher overall accuracy (90.4%) than RF (88.2%), CART (85.5%), or SVM (79.9%). Nonetheless, the highest overall accuracy (94.7%) was obtained when integrating the four machine learning algorithms in an Ensemble Learning Approach (ELA). Applying ELA improved the classification accuracy by 4.2%, 6.4%, 9.2%, and 14.8% compared to single learner classification algorithms (i.e., GTB, RF, CART, and SVM, respectively). This study demonstrates an improved classification accuracy for honey bee habitat mapping in tropical rangeland by applying ELA, which can provide a better approach for monitoring and managing bee

关键词： Learning systems

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