AAU Institutional Repository (AAU-ETD)
Addis Ababa University Institutional repository is an open access repository that collects,preserves, and disseminates scholarly outputs of the university. AAU-ETD archives' collection of master's theses, doctoral dissertations and preprints showcase the wide range of academic research undertaken by AAU students over the course of the University's long history.
How to Submit Your Work
The repository contains scholarly work, both unpublished and published, by current or former AAU faculty, staff, and students, including Works by AAU students as part of their masters, doctoral, or post-doctoral research
- All AAU faculty, staff, and students are invited to submit their work to the repository. Please contact the library at your college.
You may contact digirep@aau.edu.et.with any questions about the repository
Colleges,Institutes in AAU-ETD
Select a college,institute to browse its collections.
Recent Submissions
The Effect of Grinding Media Shapes on Ballmill Performance in Limestone Grinding
(Addis Ababa University, 2025-08) Wubsera Gebrekidan; Mulugeta Sisay (PhD)
This study examines the effect of grinding media shape on ball mill efficiency by comparing spherical balls to worn, non-spherical balls in the grinding of limestone ore, an essential but energy-intensive process in which media consumption accounts for approximately 37% of operational expenses. To fill a significant research gap in media shape degradation, the methodology used controlled laboratory-scale batch grinding tests under identical conditions, with the resulting products analyzed through sieve analysis to determine particle size distribution (P80), and specific energy consumption and power draw were calculated using established comminution theory. The results demonstrated a clear and significant effect, showing that spherical balls produced a finer product (P80 of 80.72 μm) compared to worn balls (P80 of 86.46 μm), while also achieving this superior result with lower energy consumption (16.31 kWh/ton vs. 17.84 kWh/ton) and a reduced power draw (2.61 kW vs. 2.85 kW), indicating that worn balls lead to less efficient grinding and higher operational expenses due to their irregular shape and reduced effective surface area. Consequently, the study confirms that maintaining spherical grinding media is crucial for optimizing mill efficiency and profitability, recommending that industrial operations implement regular media monitoring and replacement schedules, while suggesting future research explore mixed media charges and interactions with other variables like mill speed and liner profile for a more comprehensive understanding.
Beneficiation and Characterization Techniques of Coal in the Western region of Tarcha Zuria Wereda, Southern Ethiopia
(Addis Ababa University, 2015-05) Daniel Kassaye; Zekarias Gebreyes (PhD)
Coal stands as the most plentiful and extensively found fossil fuel. Thanks to advanced methods, it can be extracted, moved, and stored efficiently and economically. The global trade of coal is experiencing consistent growth, accompanied by intense competition regarding supply and pricing. Nevertheless, the future commercial viability of coal hinges on its environmental sustainability, particularly on the ability of the power generation sector to minimize sulfur and other harmful emissions. This research examines the extraction methods employed at the Tarcha coal deposit located in Tercha Zuria Wereda, Southern Ethiopia. It utilizes a wet extraction technique to evaluate flotation responses and optimize key factors such as yield percentage and ash content. The primary goal of the study is to enhance the quality of coal by refining flotation processes and minimizing impurities. Laboratory experiments are conducted with varying particle sizes and different ratios of collector to frother in the froth flotation process. The results indicate that the highest coal recovery yields are achieved at a collector-to-frother ratio of 8:4, while also assessing how these variables affect ash content. The data reveal a clear trend of increasing ash content as particle size decreases, highlighting the importance of maintaining specific parameter ranges to optimize yield. Ultimately, this project offers valuable insights that could support local mining operations, particularly the ET-Mining Development Company, which is actively involved in job creation and community development initiatives. The outcomes of this study may also aid Ethiopia in meeting its domestic coal needs, potentially decreasing its dependence on imported coal as the nation advances its coal resource development
Practice and challenges of plastic waste collection: The case of Addis Ababa
(Addis Ababa University, 2024-07) Habtamu Demissie; Shimeles Damene (PhD)
Plastic waste collection has become a vital economic activity in Addis Ababa, supporting the livelihoods of formally registered and informally operating waste collectors. This thesis explored their practices and challenges through a mixed-methods approach. Quantitative data were gathered from a sample of 174 collectors, comprising 44 formal and 130 informal plastic waste collectors, selected using stratified and simple random sampling methods. Complementary qualitative insights were also collected through focus group discussions (FGDs) with participants from both categories of collectors, along with key informants from government agencies, small and medium-sized enterprises, and plastic waste recyclers. The quantitative findings were analyzed using descriptive statistics, while qualitative data were examined thematically. The study revealed that 90% of both group collectors focus on polyethylene terephthalate (PET) waste, mainly sourced from streets and ditches. Majority of formal waste collectors gather waste from households but face challenges with poorly sorted plastic waste. Informal collectors typically collect smaller quantities of plastic daily and work longer hours compared to formal plastic waste collectors. Significant discrepancies in resources and capabilities exists between formal and informal collectors; formal collectors have access to transportation more often than informal collectors, who usually transport plastic waste manually. Safety practices also vary widely, with 98% of formal collectors using personal protective equipment during collection and transportation of waste, compared to 19% informal collectors. Access to properly designated storage areas for plastic waste is among the significant challenges; formal waste collectors use public open spaces for storage, while informal plastic waste collectors store in relatively better private fenced areas. Many formal collectors are concerned about low unit and fluctuating plastic waste prices, which they often experience reduced income. Training opportunities and other forms of support are scarce for both groups, and relationships with buyers are largely transactional, with most collectors operating without any written or unwritten contracts. Inclusive training programs, the integration of informal collectors into the formal system, and fostering collaboration among government agencies and other stakeholders are essential recommendations to improve plastic waste collection practices and address existing challenges.
Some Applications of Elliptic Functions and Elliptic Integrals
(Addis Ababa University, 2024-09) Ayana Mossie; Bahru Tsegaye
One of the most important applications of elliptic integrals of the form ∫𝑅(𝑥.√𝑝𝑛(x)) dx where R is rational algebraic function and 𝑝𝑛(x) is polynomials of degree 3 or 4 with no repeated roots. Nowadays, incomplete and complete elliptic integrals of the first kind are estimated with high accuracy using advanced calculators. In this paper, several techniques are discussed to show how definite integrals of the form ∫𝑅(𝑥.√𝑝𝑛(x)) dx can be converted to elliptic integrals of the first kind, and hence be estimated for optimal values. Indeed examples are provided in each step to help clarifications. Finally I have used eq.6 and eq.23 which is an important equations to show my analysis of ascending and descending transformation by taking initial values of F(∅0,k0) to provide a 30 decimal place values of numerical evaluations.
Assessment of Information Security Culture in Public Hospitals in Southern Nations Nationalities and Peoples Region: The Case of Hawassa Referral Hospital
(Addis Ababa University, 2010-06-01) Temesgen Gebrasilase; Lemma Lessa
Background: - Traditionally, most of the researchers and experts in the field of information security believed a technological solution to address majority of information security issues. However, contemporary studies have shown that non-technical solutions including the human behavior and processes are as important as technical solutions in safeguarding organization information assets.
Objective: - To assess the information security culture of Hawassa Referral Hospital in order to improve the existing information security culture of the hospital.
Methods: - A cross-sectional survey was conducted in Hawassa Referral Hospital from March-April 2010. A total of 314 study subjects were participated for questionnaire and in-depth interview. The data was collected by using a non-structured pre-tested questionnaire, in-depth interview and document analysis. The quantitative data was analyzed by using SPSS version 15.0 and the qualitative data was analyzed manually.
Results: - It was found that, 66.9% of the study participants have no knowledge about information security. About 63% of the respondents reported that management does not assist to the implementation and incorporation of information security in the hospital.
The result of the study also showed the absence of well written and documented information security policy in the hospital.
Conclusion and recommendations: - The study showed that majority of the respondents in the hospital has no knowledge about information security. The study also revealed that there is a lack of commitment from top management for the incorporation and implementation of information security in the hospital. Hence, it is recommended that there is a need to provide extra-education and training on information security issues