Browsing by Author "Negash, Solomon"

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    Diffusion in Random Media
    (Addis Ababa University, 2010-06) Negash, Solomon; Yergou, Tatek (PhD)
    In this work we present Monte Carlo simulations of particle and polymer diffusion in two dimensional (2D) media with obstacles distributed randomly. For diffusion of a particle, the mean-square displacement of the diffusing species is proportional to time for normal diffusion. But in disordered systems anomalous diffusion may occur, in which the meansquare displacement is proportional to some other power of time. In the presence of moderate concentration of obstacles, diffusion is anomalous for short times and normal for long times. Monte Carlo calculations are used to characterize anomalous diffusion for obstacle concentrations between zero and the percolation threshold. As the obstacle concentration approaches the percolation threshold, diffusion becomes more anomalous for long times; the anomalous diffusion exponent increases. In polymer diffusion, we present a new effective algorithm to simulate dynamic properties of polymeric systems confined to lattice. The algorithm displays Rouse behavior for all spatial dimensions. The systems are simulated by bond fluctuation method to study both the static and dynamic properties of the polymer chains. For static properties we calculated the average meansquare end-to-end distance hR2(N)i and the mean-square radius of gyration hR2 g(N)i. Both the end-to-end distance and the radius of gyration are proportional to some power of the number of monomers (N), hR2(N)i _ N3/2 and hR2 g(N)i _ N3/2. For dynamical properties we look at the mean-square displacement of the total chain. For short times the mean-square displacement of the monomers g1(t) and the mean-square displacement of the monomers relative to the chains center of mass g2(t) show the same behavior and for long times the mean-square displacement of the center of mass g3(t) takes over
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    The practice and challenges of implementing continuous assessment in government First Cycle primary schools of Yeka Sub-City
    (Addis Ababa Univerisity, 2014-05) Negash, Solomon; Chalchisa, Desalegn(PhD)
    The purpose of this study was to examined and scope of activities and problems of practice of continuous assessment at the first cycle primary school level in Yeka Sub-City. To answer the basic research questions, descriptive survey research method was employed. The major findings of this study include very weak document handling, and poor record keeping of learners’ CA achievements, less learners’ involvement in their own assessment. Many assessment techniques were used in properly. The study also found that large class sizes, inadequacy of text books and school infrastructures, lack of manuals, weak follow up, support and feedback system on the implementation of learners’ CA, lack of training opportunity for teachers were the major challenges of CA. For further improvement, school based trainings, adequate and updated manuals, advanced follow up, support and immediate feedback on the learners’ CA implementation, and fulfillment of school infrastructures are suggested as potential solutions to the proper implementation of CA.
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    The practice and challenges of implementing continuous assessment in government First Cycle primary schools of Yeka Sub-City
    (Addis Ababa University, 2014-05) Negash, Solomon; Desalegn Chalchisa, Desalegn (PhD)
    The purpose of this study was to examined and scope of activities and problems of practice of continuous assessment at the first cycle primary school level in Yeka Sub-City. To answer the basic research questions, descriptive survey research method was employed. The major findings of this study include very weak document handling, and poor record keeping of learners’ CA achievements, less learners’ involvement in their own assessment. Many assessment techniques were used in properly. The study also found that large class sizes, inadequacy of text books and school infrastructures, lack of manuals, weak follow up, support and feedback system on the implementation of learners’ CA, lack of training opportunity for teachers were the major challenges of CA. For further improvement, school based trainings, adequate and updated manuals, advanced follow up, support and immediate feedback on the learners’ CA implementation, and fulfillment of school infrastructures are suggested as potential solutions to the proper implementation of CA