Institute of Technology

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The Institute of Technology focuses on education, research, and innovation in engineering, technology, and applied sciences to support sustainable development.

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Start date: 2020End date: 2025

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    VOLTAGE CONTROL OF A DC-DC BUCK CONVERTER FOR ELECTROLYSIS USING FRACTIONAL ORDER SLIDING MODE CONTROL
    (Hawassa University, 2020-10-22) DEMOZ LISANEWORK WELDETSADIK
    Switching DC-DC converters are non-linear and the most widely used circuits in power electronics. Generally, they are used in all conditions where there is need of stabilizing a given DC voltage to a desired value. DC-DC buck converters are used in voltage step down applications. A DC solar energy is converted to the desired voltage level using the a buck converter, for hydrogen generation with electrolysis process have been investigated. The electrolysis load for hydrogen production especially needs low voltage and high currents. To have these conditions the converter must be designed and controlled sensitively. For this aim, the fractional order sliding mode (FOSM) controller is used as a solution in this paper. Simulation results showed that, FOSM controller improved the rise time and settling time by 2% and 15.3% respectively compared the values using PID controller. Similarly, FOSM controller shows comparatively best performance improvement over SOSM in terms of high reduction of unwanted oscillation in addition to the rise time, settling time improvements. The overshoot is reduced from 46.3% to 5.208% using PID controller while it is totally removed when SOSM and FOSM controllers are applied. Both SOSM and FOSM controllers overcome the effect of electrolysis load variations. The actual output voltage is not deviated from desired value even for large input voltage variation using FOSM controller. Furthermore, the performance of controller was tested by increasing and decreasing 58.52% electrolysis load from operating point while desired output voltage is decreased by 50% and increased up to 20% from operating point. Generally, from the above analysis results it is evident enough that FOSM is better and preferable controller than the SOSM and PID controller
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    IMPROVING COMPETITIVENESS OF SMALL AND MEDIUM MANUFACTURING ENTERPRISES THROUGH SUPPLY CHAIN MANAGEMENT: A CASE OF LEATHER PRODUCTS MANUFACTURING ENTERPRISE IN HAWASSA CITY
    (Hawassa University, 2021-10-22) TAMIRAT YOHANNES GONDALO
    Small and medium leather products manufacturing enterprises are one of the enterprises provides expectation for the government to achieve target as one of the competitive sector in current market for economic growth, employment generation and building an industrial economy. In the different the enterprises has recorded very stagnant level of competitiveness with dynamic current market cause of gap on practicing supply chain managements. In order to conduct this research, questionnaire was developed and distributed for 132 respondents in eleven leather products manufacturing enterprises those work on different department and level. All the questionnaires were collected by using schedule data collection method; beside the questioner interview and detail observation also conducted with experts to supports the findings from the questionnaire. Then the collected data was analyzed using IBM SPSS 26; in both descriptive and inferential statics. Regarding the descriptive statistic and inferential statistics results the finding shows; the current supply chain management practice level of the leather products manufacturing enterprise is medium, this indicate its influence on their competitiveness. Regarding the correlation, all the independent variables are positively and significantly correlated with dependent variable with a significant level of less than 1%. As per the regression analysis output result the coefficients of four predictor variables are statistically significant at less than one percent (P<.001). Therefore, the purpose of this study is to propose ways to improve the competitiveness of small and medium leather products manufacturing enterprises through Supply Chain management and applying competitive priority on operation. Finally the study proposed adoptable SCM framework and recommended the manufacturing enterprises are using supply chain management practices and applying competitive priority to customer value and need with the proper support and guidance of governments in order to improve their competitiveness
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    APPLICATION OF HYBRID APPROACH FOR WOLAITA LANGUAGE PART OF SPEECH TAGGING
    (Hawassa University, 2020-03-24) BIRHANESH FIKRE SHIRKO
    The aim of this research is to develop part-of-speech tagger for Wolaita Language using hybrid approach. Part of speech tagger is one of the subtasks in natural language processing (NLP) applications which is vital for other NLP tasks, like parser, machine translator, speech recognizer and search engines. It is a process of labeling a corresponding part of speech (PoS) tag for a word that defines how the word is used in a sentence. The PoS tagging for Wolaita language is not sufficient yet to be used as one important component in other natural language processing (NLP) applications. In this thesis, the development of part of speech tagger using hybrid approach that combines HMM and transformation based learning approaches is conducted for Wolaita language. In general, HMM model needs large data to increase the performance and the transformation based learning model learn rule based on the language features. The HMM model tags the words based on the optimal path for a given sequence of words and transformation based learning is a rule based model that tag the words based on rules; it learns rule directly from the training corpus without expert knowledge. The developed hybrid approach of Wolaita language PoS tagger uses HMM tagger as initial annotators and the rule based tagger as a corrector based on fixed threshold values. For implementation and experiment, the author used python programming and NLTK. For training and testing the model, 14,358 untagged Wolaita language words are collected from three different categories (Bible, Social media in Wolaita language (Wogetta FM 96.6) and Wolaita language department). The annotation of corpus performed manually by two language experts. For tagging purpose 26 PoS tag are identified based on the work of Berhanu H., work of wakasa (2008) and with help of language experts. From the entire corpus, 90% is used for training and the remaining 10% is used for testing purpose. The performance of the three taggers is tested by using different experiments. After experiment the researcher found that the performance of HMM, rule based and hybrid taggers shows 88.14%, 92.96% and 94.82% respectively. Generally, hybrid approach showed the better performance to assigning part of speech tag for Wolaita language sentences
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    EVALUATING THE PERFORMANCE OF HEC-HMS AND SWAT HYDROLOGICAL MODELS IN SIMULATING THE RAINFALL RUNOFF PROCESS FOR DATA SCARCE REGION OF ETHIOPIAN RIFT VALLEY LAKE BASIN
    (Hawassa University, 2020-10-23) MOHAMMEDRESHID ABDALA ALIYE
    Several physically-based and distributed watershed models have been developed to model the hydrology of the watershed. For a specific watershed, selecting the most suitable hydrological model is necessary to obtain good simulated results. In this study, two hydrologic models, Soil and Water Assessment Tool (SWAT) and Hydrological Engineering Centre–Hydrologic Modeling System (HEC-HMS), were applied to simulate streamflow in the Katar river basin, Ethiopia. The performances of these two models were compared to select the right model for the study basin. Both models were calibrated and validated with streamflow data of 11 years (1990- 2000) and 7years (2001-2007) respectively. Nash-Sutcliffe Error (NSE) and Coefficient of Determination (R2 ) were used to evaluate the efficiency of the models. The results of calibration and validation indicated that, for river basin Katar, both models could simulate fairly well the streamflow. SWAT gave the model performance with the R2 > 0.78 and NSE > 0.67; and the HEC-HMS model provided the model performance with the R2 > 0.87 and NSE > 0.73. Hence, the simulated streamflow given by the HEC-HMS model is more satisfactory than that provided by the SWAT model
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    PERFORMANCE OF HOLLOW CONCRETE BLOCKS WITH CRUSHED WASTE GLASS AS PARTIAL REPLACEMENT OF FINE AGGREGATE
    (Hawassa University, 2020-10-23) YOSEF KUMA AYANA
    Construction is booming in developing countries like Ethiopia. As construction is increasing, demand and price of the construction materials are increasing. Among building construction components hollow concrete block is being widely used. From concrete block making materials fine aggregate is higher constituent. The uses of river sand as fine aggregate leads to exploitation of natural resources and also environmental concerns related to the disposal of various waste materials have escalated to a worrying level, among those: crushed wastes glass is one of them. Therefore, to make the construction industry sustainable, the use of waste materials in place of natural resources is one of the recommended. The main objectives of this study was to investigate the performance of class C hollow concrete blocks with crushed waste glass as partial replacement of fine aggregate and to determine the replacement percentages at which crushed waste glass can be effectively put into service and also compare the cost of crushed waste glass partially replaced in hollow concrete block with the conventional ones. The method used was experimental study. The crushed waste glass partial replaced fine aggregate with 10%, 20% and 30% by volume and the control mix was prepared. The compressive strength test was carried out at the 7th, 14th and 28th days, whereas the density and water absorption tests were carried out on the 28th day. As per the finding, the control mix compared with the replacement specimen, the density is decreased as the proportion of crushed waste glass increases and decreases by 5.6% at a 30% replacement, the water absorption decreases as crushed waste glass content increases and it decreased by 2.5% at a 30% replacement, the compressive strength with up to 20% replacement increases by 59.72%, but after that, it starts decreasing for 30% replacement by 10.64%, results showed that replacement of 20% fine aggregate by crushed waste glass was found to have optimal compressive strength, and also the production of block using 20% crushed waste glass saves cost compared to the conventional once by 2.06% in 1m2 area.
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    DESIGN AND SIMULATION OF DC MICROGRID FOR ELECTRIC VEHICLE CHARGING STATION (A CASE STUDY HAWASSA CITY)
    (Hawassa University, 2020-08-17) MATHEWOS HADERO GUTENA
    Development of electric vehicle has been established as an effective way to ensure energy security and realize emission reduction. However, the public electric vehicles charging station which is important element of using electric vehicles is not installed in Ethiopia. Therefore design of DC microgrid for charging station is proposed in this paper. In Ethiopia the electric energy infrastructure is not modernized enough and it is really difficult to fully depend on the energy obtained from grids. Thus, it is important to integrate the renewable energy (solar), grids and energy storage. However, the reliability of integration of renewable energy is dependent on the ability of the system to accommodate expected and unexpected changes (in production and consumption) and disturbances, while maintaining quality and continuity of service to the customers. Thus to improve real-time control performance and reduce possible seasonal variation forecasting is proposed for the solar energy used in the system. Thus in this study the author used the metrological data from Hawassa station and used machine learning algorithm for train the model with collected data and python used as programming language to develop forecasting model score system. Python is one of a well known high level programming language in data science.In this thesis, Jupiter notebook is used to write Python codes to develop a solar energy forecasting system.The designed forecasting system can predict the next day irradiance with accuracy of 97.56%. Next MATLAB simulation tool is used to integrate system. The proposed maximum operating voltage of this DC microgrid charging station is 500 Vdc. Power flow management using fuzzy logic controller keeps voltage within expected range with standard voltage deviation 2.2 and improved the response time 1.645 ms. More over the author also investigated the operating costs per year for this design. The operating costs for energy is $43,651per year if you use grid only for charging of EVs. On the other hand if 400 kW of PV and 680 kWh of battery capacity is integrated to the grid it reduce the operating costs to$6,344 /yearwith annualized saving of $37,306.This implies as the hybrid system has investment payback of 3.06 years and an IRR of 32.7%.Thus, clearly the result obtain in this thesis have great potential in future charging station design
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    EVALUTION OF THE CONTRIBUTION OF GEOMETRIC DESIGN OF THE ROAD INTERSECTION IN ALLEVIATING TRAFFIC ACCIDENT IN SHASHEMENE TOWN
    (Hawassa University, 2020-08-18) YASIN ASSEFA MOSSA
    Efficiency of intersections contributes significantly towards the efficiency of urban road networks. Whereas intersections constitute a very small part of the entire transportation network, more than 50% of all motor vehicle accidents occur at intersections. Because of the overrepresentation of intersection-accidents, intersections require special attention in the planning and designing of road networks. Thus, the main aim of this research study is the evaluation of the contribution of geometric design of the road intersections in alleviating traffic accident in the Shashemene town. Abosto and Kudus Mikael signalized intersections while Tekliye, Semaniyaand (81), arada Sefer, Gibrna, Zero Amst (05) and Mobile non signalized intersections were chosen for this thesis. These intersections were selected for the study from different locations within the town. They have more traffic accident than any other similar junctions do in Shashemene town. The geometric, traffic and accident data were collected during the morning and afternoon peak time periods using site observation, field measurement and video camera in each of the selected junctions. The study use four distinct scientific principles namely: accident frequency, accident rate, empirical Bayesian and critical accident method to identify black spot locations at selected intersections. Out of the methods, empirical Bayesian proved superiority so that much of the conclusion was based on this method. Log linear Poisson regression and Negative binomial regression model was used to investigate the effect of road geometric design elements on the road crash occurrence in the selected junctions.The results of paper proved that road junction Semaniyand, Tekliye, Kudus Mikael and Abosto were highly prone to accidents than other road junctions in Shashemene town with adjusted accident frequency values of 27.85, 26.54, 25.25 and 22.65 respectively. And also the result of this study shows, there is a strong correlation between road geometric design elements and road crash occurrence. The modeling result indicated that the explanatory variables such as lane width, super elevation, gradient, and intersection sight distance, shoulder width, median type, and median width, angle of intersection, side walk width and curves radius had significant effects on the occurrence of road traffic crashes
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    PERFORMANCE EVALUATION OF OFF-STREET PARKING IN ADDIS ABABA CITY (A CASE STUDY IN SELECTED CENTRAL BUSINESS DISTRICTS)
    (Hawassa University, 2020-10-21) ALEMSEGED ESHETE TEKLEWOLD
    Car-parking sector has always been of great importance in terms of urban mobility, since it is a fundamental element in achieving a high level of accessibility in the city centers. Central Business Districts (CBD) are areas of dense traffic which result in parking problems. Addis Ababa, the administrative and financial capital of Ethiopia, is experiencing continued growth and change. But due to the fact that more than 60% of the vehicles in the country are operated in this city, parking problem is crucial. Parking plays an important role in mobility, access and the economic development of Addis Ababa. The space that parking requires can be problematic in any city, but it poses particular problem in Central Business Districts (CBD). Due to the absence of clearly designated areas of parking in Ethiopia, shortage of parking facilities has been a long standing problem in the country. Especially cities with greater economic activities, greatly faced to traffic congestion and delay problems. The general objective of this research is to evaluate the efficiency of off-street car parking in the Central Business District area of Addis Ababa City. Depending upon their greater demand requirement for a parking facilities, three central business districts of the capital (i.e. ‘Megenagna’, ‘Bole’ and ‘Merkato’) were chosen for detailed analysis. From the stated locations; 11, 13 and 11 off-street parking sites were selected for further analysis respectively. For data collection in and out data collection technique were used. Data was collected from May to September 2019 during the interval of time 8 am-6 pm. From the accumulation graph, peak hour for the demand was selected. The performance analysis result shows that off-street parking’s in the central business district of the city is over their capacity. Demand study was also made to ‘Megenagna’ site by using land use analysis method. From the demand analysis 2,454 additional parking spaces were required to afford the existing demand. In addition to this, structured interview was made to the users of the parking facilities to strengthen the analysis. The research conclude that the main problem of parking in the areas is lack of enough off-street parking space supplies, lack of parking policy and management system, absence of parking signs and marks which results in confusion for finding available parking spaces and lack of knowledge of users for parking usage and shared parking strategies
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    DISTRIBUTION SYSTEM RELIABLITY IMPROVEMENT USING DISTRIBUTED GENERATION AND NETWORK RECONFIGURATION Case study: Arbaminch Distribution system
    (Hawassa University, 2021-10-22) MEKLIT GIRMA
    Power supply reliability is the basic issue for economic and technology development of the country. The sufficient or adequate and secure supply of power will assure the reliability of the system. Unreliability of the system occur due to high outage frequency and duration, system overload and unsecure system or protection system. When the distribution system is reliable, it has capacity to meet the demand of customer and operate under adverse condition. Arbaminch distribution system has encountered frequent power interruption and power quality problem. The interruptions are mainly caused by system overload and short circuit fault. The reliability of the distribution system is assessed based on the data from Ethiopian Electric Power Corporation. Arbaminich substation of feeder -05 is selected as case study, which has high rate of interruption. Feeder -05 has SAIDI value of 236.8386 Hr./cust. /yr. and SAIFI of 221.6338 f/cust. /yr. The reliability indexes values of feeder -05 are not within the ranges of bench marks of reliability requirement. This thesis focused on reliability improvement of distribution system with better placement of distributed generation and network reconfiguration. Particle swarm optimization algorithm is used for placement of DG, size and network reconfiguration. The algorithm is done using MATLAB 2016 software. Based on the availability in the area, efficiency, cost and emission level, Solar and Microturbine sources are used as distributed generation. The suitable site and size of DG are found at bus 10 with suitable size 4.5 MW. For network reconfiguration sectionalizing switch is used. Before reconfiguration the switch was placed at bus 20, 21, 22,23 and 24. During network reconfiguration switch changed to bus 3, 4,12,24 and 31. The reliability indices SAFI, SAIDI and EENS value improved by 82.81%,78.89% and 78.10% respectively after DG with reconfiguration used. Expected interruption cost before applying the proposed method is 9,758,852$ /year. After the proposed method used expected interruption cost reduced to 2,995,270$ /year. This indicates that, 6,763,582 $/year is saved after using the proposed techniques
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    EFFECTS OF INTEGRATED USE OF GRASS STRIP COMBINED WITH SOIL BUNDS ON SELECTED SOIL PROPRIETIES: A CASE OF DALTA SUB WATERSHED IN ESSERA DISTRICT, SOUTHWESTERN ETHIOPIA
    (Hawassa University, 2024-10-23) TIZITAW GODARO TOLOLA
    Soil erosion by water constitutes to the most widespread and damaging process of soil degradation. The aim of this study was to determine the effects of integrated use of grass strip combined with soil bunds on selected soil proprieties, to evaluate the Effects of integrated use of soil bund and grass strip combined with soil bunds under different slope gradient and To assess farmer’s adoption on using grass strip combined with soil bunds as soil erosion conservation measures at Dalta sub-watershed. 246-households selected randomly from three kebeles by using systematic random sampling techniques. Three land management practices (Land treated with soil bund alone, soil bund with grass strip and untreated adjacent control plot) were evaluated under three slope of lower slope (3-8%), middle slope (8-15%) and upper slope (15-30%). A total of 27 soil samples were collected from the top 20 cm soil depth with three replication in ‘X’ design square from 10 m x 10 m plots. The results showed that soil Bulk density (Bd), moisture content (MC), soil pH, soil organic matter (SOM), total nitrogen (TN) available phosphorous (Av.p) and cation exchange capacity (CEC) were significantly (p≤0.05) different on land treated by soil bund and soil bund with grass strip as compared to the untreated adjacent control plots. The result also showed, the contents of sand, silt and clay were significantly different with the change in the slope gradient. There were no significant (p≤0.05) differences on soil texture between the conserved and non conserved lands but significant difference with respect to slope gradient. The contribution of soil bund and soil bund with grass strip were effective and promising for land rehabilitation and improving soil properties through minimizing erosion and farmers’ adoption towards the practices at Dalta sub watershed, southwestern Ethiopia. Generally, the difference observed in soil physical and chemical properties between slope positions is not due to grass strip malfunction at slope positions but caused by past erosion events and topographic effects on soil property. Moreover, further research need to be conducted on socio-economic aspects for a better understanding the impact of integrated soil and water conservation interventions.