Browsing by Author "Belay, Solomon"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Accretion Discs around magnetised Stars, in Particular Neutron Stars
    (Addis Ababa University, 2010-02) Belay, Solomon
    We develop a self-consistent theoretical model for the steady-state of an axisymmetric thin ac- cretion disc with an internal dynamo around a magnetised stars. Starting from the vertically integrated equations of magnetohydrodynamics we derive a single ordinary di®erential equation for a thin accretion disc around a massive magnetic dipole and based on the analytical formu- lation we integrate this equation numerically from the outside inwards. Our numerical solution shows that the torque between the star and the accretion disc is dominated by the contribution from the dynamo in the disc. We extend this model for weak magnetic ¯elds and we present millisecond x-ray pulsars have weak magnetic dipole moments of » 1016 Tm3 compared to ordi- nary X-ray pulsars with dipole moments of 1020 Tm3. For this reason a surrounding accretion disc can extend closer to the neutron star, and thus reach a higher temperature, at which the opacity is dominated by electron scattering and radiation pressure is strong. We compute the self-similar structure of such a geometrically thin axisymmetric accretion disc with an internal dynamo for the three regions of the disc. For the outer disc region which corresponds to the gas pressure and Kramer's opacity dominated, in the middle region the gas pressure and electron scattering dominated , in the inner region the radiation pressure and electron scattering dom- inated accretion disc. Our numerical solution shows that the torque between the star and the accretion disc is dominated by the coupling between the stellar magnetic ¯eld and the dynamo in the disc. Finally, we have developed that the time-dependent equations for an accretion disc and linear stability analysis of steady-state disc solutions in the presence of a strong external magnetic ¯eld. The analytical and numerical analysis of the solutions to the stability properties and time evolution will tell us the observed behaviours of the torque between the disc and the star. Key words: accretion, accretion discs - magnetohydrodynamics (MHD) - magnetic ¯elds - stars: neutron X-rays: binaries- pulsars: general
  • No Thumbnail Available
    Item
    The Implementation of Problem Solving Approach in the Context of Rural Primary Schools in Oromia Region: the Case of Adami Thlu Judo Komboicha Woreda
    (Addis Ababa University, 2004-06) Belay, Solomon; Nekatibeb, Teshome (PhD)
    It has been about ten years since the government of Ethiopia made a new educational and training policy. The making of the policy has been followed by the development and implementation of different programs ill order to carry forward the innovations enshrined in it. One of the highly emphasized aspects of this policy is the need to implement a problem solving education both in content and approach with the objective of producing a problem solving citizen. Related with this, the more elaborate aspiration of the policy is the trend towards shifting classroom instructions from teacher-centered approach to a student-centered approach. Though a variety of understanding exist on what 'a student-centered approach' means, the problem solving approach with its qualifications as a student-centered approach and its unquestioned relevance in the development of problem solving citizen, it is expected that this approach is given precedence in the implementation of the policy. This particular study had, as its starting point, a supposition that in fact problem solving approach/process are teachable and the capacity to solve problems can be developed in school children. It is also assumed that efforts are being made to implement this approach at all levels of the educational system of the country. Owing to the realization that the country's largest population lives in the rural areas and the priority given to agriculture led economic development, the research focused its attention to finding out how the problem solving approach is being implemented in rural primary school s. The bulk of primary school leavers constitute the young work force in the rural areas: therefore the study narrowed its focus on eighth grade students. This case study conducted to examme the implementation of problem solving approach, took 48 classroom observations in eight rural primary schools as central to the data collection process. However, in order to increase the validity of the research and with the intention of describing more what has been taking place in the classroom interactions, the main elements of the interactions have been identified and used as source of data. These main elements included; 152 teachers, 160 students, 8 principals, eighth grade text books and school facilities. The sampling procedure and instruments of data collect ion were such that each category of elements is repre sented in a way they balance representation and depth and detail. Though our daily life is full of problem solving, the scientifically accepted ste ps/process of problem so lving approach were identified and th e ir implementation was assessed in a way applicable to eac h so urc e of data. According ly the data obtained from each source with the particular instrument of data co ll ect ion were organized and analyzed er certain themes pertinent to the process of problem solving The study revealed that problem so lving approach is not being implem ented in cla ssroom in structions. Teachers either have no any training or are poorly trained to implement problem so lving approac h. Text books and school facilities are not in favor of the implementation of problem solving approach. Rural primary school s are und er the gnawing influence of the vicious circle of poverty and low quality education. Therefore , stated in a very general sense, one can conclude that the implementation of problem solving approach in rural primary schools is in its embryo nicstage. It is not born, being cared and deve loped . By extension of the implication of the process to the end , one also can say that primary school leavers didnt have the capacity of problem solving. Students rather are found to develop dependency syndrome and highly influenced by the information they acquire from sources other than their forma l education.
  • No Thumbnail Available
    Item
    The Implementation of Problem Solving Approach in the Context of Rural Primary Schools in Oromia Region: the Case of Adami Tulu Judo Kombolcha Woreda
    (Addis Ababa University, 2004-06) Belay, Solomon; Nekatibeb, Teshome (PhD)
    It has been about ten years since the government of Ethiopia made a new educational and training policy. The making of the policy has been followed by the development and implementation of different programs in order to carry forward the innovations enshrined in it. One of the highly emphasized aspects of this policy is the need to implement a problem solving education both in content and approach with the objective of producing a problem solving citizen. Related with this, the more elaborate aspiration of the policy is the trend towards shifting classroom instructions from teacher-centered approach to a student-centered approach. Though a variety of understanding exist on what 'a student-centered approach' means, the problem so lving approach with its qualifications as a student-centered approach and its unquestioned relevance in the development of problem solving citizen, it is expected that this approach is given precedence in the implementation of the policy. This particular study had, as its starting point, a supposition that in fact problem solving approach/process are teachable and the capacity to solve problems can be developed in school children. It is also assumed that efforts are being made to implement this approach at all levels of the educational system of the country. Owing to the realization that the country's largest population lives in the rural areas and the priority given to agriculture led economic development, the research focused its attention to fmding out how the problem so lving approach is being implemented in rural primary schools. The bulk of primary school leavers constitute the young work force in the rural areas: therefore the study narrowed its focus on eighth grade students. This case study conducted to examme the implementation of problem so lving approach, took 48 classroom observations in eight rural primary schools as central to the data collection process. However, in order to increase the validity of the research and with the intention of describing more what has been taking place in the classroom interactions, the main elements of the interactions have been identified and used as source of data. These main elements included; 152 teachers, 160 students, 8 principals, eighth grade text books and school facilities. The sampling procedure andinstruments of data collection were such that each category of elements is represented in a way they balance representation and depth and detail. Though our daily life is full of problem so lving, the scientifically accepted steps/process of problem solving approach were identified and their implementation was assessed in a way applicable to each source of data. Accordingly the data obtained from each source with the particular instrument of data collection were organized and analyzed under certain themes pertinent to the process of problem solving The study revealed that problem solving approach is not being implemented in classroom instructions. Teachers either have no any training or are poorly trained to implement problem solving approach. Text books and school facilities are not in favor of the implementation of problem solving approach. Rural primary schools are under the gnawing influence of the vicious circle of poverty and low quality education. Therefore, stated in a very general sense, one can conclude that the implementation of problem solving approach in rural primary schools is in its embryonic stage. It is not born, being cared and developed. By extension of the implication of the process to the end, one also can say that primary school leavers didn 't have the capacity of problem solving. Students rather are found to develop dependency syndrome and highly influenced by the information they acquire from sources other than their formal education. II