Browsing by Author "Shimelis, Assefa"

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    A Case Study of The Teaching Learning Process of Mathel\1atics In Yeka Tit 25/67 Secondary School of Hadiya Zone
    (Addis Ababauniversity, 2005-06) Shimelis, Assefa; Areaya, Solomon
    The main focl(' of this study was to examine how the teaching-learning proce . 0/ mathematics was going on at Yekatit 25/67 Secondary School in Hadiya Zone and factors affecting the teaching-learning process. Having done this, a few speculative suggestions were given to improve teachers' teaching methodology. To achieve what was aimed at, a qualitative case study was employed. For this purpo e, four teachers and twenty- four students were participated as a source of information in the study. Taking these subjects, the data lVas collected through interview, FGD, observation and document analysis. At the end, the study revealed negative feelings of teachers 10IVard their profession and their traditional methods of leaching in class. As teachers confirmed and observed, this was attributed 10 large number of students in a class and teachers load allotment. Moreover, the study indicated that there was less students '-teachers ' Inleraction, shortage of appropriate teaching materialS and improper utilization of the teaching materialSby the teachers. Further, the study showed that teachers did not get adequate training and all'arenes so as to improve their teaching methodology. Finally, on the basIs q/the findings, it was recommended that teachers should be trained and qualified in order to imprOl e the teaching-learning process. ResIdes, concerning the PTV program, it \lias recommended that the concerned bodies should allempt to olve the problem o/Iight and leachll7g classes by looking for some mean, lor Instance, by bUying generators so as not to break the TV transmission and consll'1lc/lI7g (~laddi/ional bUildings and opening other SecondGlY School in The town
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    Modeling and Analyzing the Deformation of Ballast Structure Due to Repetition of Loads
    (Addis Ababa University, 2015-12) Shimelis, Assefa; Abdulsetar, Siraj (Mr.)
    The issue of permanent deformation of ballast structure due to repetition of loads is the most important element in railway maintenance planning and policy making. It affects the general operation and management of railway transportation plus the overall costs of track structure and its life spans. To allow a safe, reliable and efficient rail network and to provide a good ride quality, the vertical profile of a railway track has to be maintained at a satisfactory level. And timely maintenance of ballast structure is essential to provide continuous service at reasonable costs since the track permanent deformation is a function of traffic load, environmental condition and track structure response behavior to the applied loads at different times of service life. Although most of the time deterioration process is very slow, but it might lead to massive failures with an enormous financial lose. This research determines the permanent deformation of railway ballast, particularly the vertical settlement under repeated traffic loading. Experimental data reviewed in the literature were assumed to represent the ballast materials used in LRT projects. After initial elastic modeling, the extended Drucker-Prager model with hardening, which simulates the initial plastic deformation of granular materials under cyclic loads, were used in the FEM analysis in order to account for the inelastic behavior of railway ballast. Besides, FEM analysis provides the information to predict railway ballast deformation in terms of number of loading under wheel loading. And it can be observed that the vertical stresses were concentrated underneath the sleeper and ballast permanent deformation is increasing exponentially with increasing number of loading cycles and deform non- linearly with increasing depths of ballast.