Papers by Gebremeskel Tekle
Journal of Applied Mechanical Engineering, 2020
Small wind turbine has great role in rural and remote areas in which the electric accesses from t... more Small wind turbine has great role in rural and remote areas in which the electric accesses from the grid is difficult. In this paper, horizontal axis wind turbine blade which has capacity of 5 kW was designed and verified with the help of the blade element momentum theory. Using this theory, the twist angle and chord length for each section the mid radius and the local tip speed ratio blade were calculated. Lift force is the main force for operating the wind turbine to produce useful power. Thus, Maximum lift-to-drag ratio is criterion for choosing the air foil family. Here SG air foil family were selected because they specifically designed for small wind turbine.
Latin-American Journal of Physics Education, 2014
The relationship between the spin density wave (SDW) and superconductivity is a central topic in ... more The relationship between the spin density wave (SDW) and superconductivity is a central topic in the research on the FeAs-based high TC superconductors. In this research work, the theoretical investigation of the coexistence of spin density wave and superconductivity in BaFe 2-x Co x As 2 has been made. By developing a model Hamiltonian for the system and using quantum field theory Green function formalism, we have found mathematical expressions for superconducting transition temperature (Tc), spin density wave transition temperature (Tsdw), superconductiviting order parameter (Δsc) and spin density wave order parameter (Δsdw). The phase diagrams of superconducting transition temperature versus superconductiviting order parameter and spin density wave transition temperature versus spin density wave order parameter have been plotted. By combining the two phase diagrams, we have obtained a phase diagram which shows the possible coexistence of spin density wave and superconductivity in BaFe 2-x Co x As 2 .
Latin-American Journal of Physics Education, 2015
espanolLa relacion entre la onda de densidad de espin (SDW) y la superconductividad es un tema ce... more espanolLa relacion entre la onda de densidad de espin (SDW) y la superconductividad es un tema central en la investigacion sobre los superconductores de alta TC basados en FeAs. En este trabajo se ha realizado la investigacion teorica de la coexistencia de onda de densidad de espin y la superconductividad en BaFe2-xCoxAs2. Mediante el desarrollo de un modelo de Hamilton para el sistema y el uso de la teoria del campo cuantico en funcion formalismo de Green, hemos encontrado expresiones matematicas para la temperatura de transicion superconductora (Tc), para la temperatura de transicion de la densidad de onda del espin (Tsdw), para el parametro de orden de la superconductividad (Δsc) y el parametro de densidad de onda del espin (Δsdw). Se elaboraron los diagramas de fase de la temperatura de transicion superconductora contra el parametro de orden de la superconductividad y la temperatura de transicion de la densidad de espin contra el parametro de orden de la densidad de onda del esp...
Advances in Materials Science and Engineering, 2020
Cobalt sulfide thin films were synthesized from acidic chemical baths by varying the deposition t... more Cobalt sulfide thin films were synthesized from acidic chemical baths by varying the deposition time. The powder X-ray diffraction studies indicated that there are hexagonal CoS, face-centered cubic Co3S4, and cubic Co9S8 phases of cobalt sulfide. The crystallite size of the hexagonal CoS phase decreased from 52.8 nm to 22.5 nm and that of the cubic Co9S8 phase increased from 11 nm to 60 nm as the deposition time increased from 2 hrs to 3.5 hrs. The scanning electron microscopic images revealed crack and pinhole free thin films with uniform and smooth background and few large polygonal grains on the surface. The band gap of the cobalt sulfide thin films decreased from 1.75 eV to 1.3 eV as the deposition time increased from 2 hrs to 3.5 hrs. The photoluminescence (PL) spectra of the films confirmed the emission of ultraviolet, violet, and blue lights. The intense PL emission of violet light at 384 nm had red shifted with increasing deposition time that could be resulted from the incr...
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Papers by Gebremeskel Tekle