Ismail M.,Cairo University |
Adel A.,Cairo University |
Adel A.,Majmaah University
Physical Review C - Nuclear Physics | Year: 2014
The influence of nuclear deformation on α-decay half-lives is taken into account in the deformed density-dependent cluster model. The microscopic potential between the spherical α particle and the deformed daughter nucleus is evaluated numerically from the double-folding model by the multipole expansion method. A realistic density-dependent nucleon-nucleon (NN) interaction with finite-range exchange part, which produces the nuclear matter saturation curve and the energy dependence of the nucleon-nucleus optical potential model is used. The ordinary zero-range exchange NN force, which is commonly used in α decay, is also considered in the present work. We systematically investigate the influence of nuclear deformations on the α-particle preformation probability of the deformed medium and heavy nuclei from the ground state to ground-state α transitions within the framework of the Wentzel-Kramers-Brillouin method by considering the Bohr-Sommerfeld quantization condition. Taking the deformation of daughter nuclei into account changes the behavior of the preformation probability, Sα, by an amount depending on the Q value, the order, values, and signs of deformation parameters. Calculations have been conducted for the spherical nuclei in order to present clearly the effect of the deformation on the preformation probability. The combined effect of both finite-range force and deformation can reduce the value of Sα by about an order of magnitude. © 2014 American Physical Society.
Alklaibi A.M.,Majmaah University
Energy Conversion and Management | Year: 2015
The internal two-stage evaporative cooler is studied by experimentally comparing its performance with direct evaporative cooler and theoretically with direct and external two-stage evaporative coolers. The results show that the efficiency of the internal two-stage evaporative cooler is higher than that of direct evaporative cooler but it cannot be raised over 100%. It was also shown that the efficiency of the internal evaporative cooler type is less sensitive to air speed than direct type. The efficiency of the direct evaporative cooler increases by 12%, and the internal evaporative cooler increases only by 5% when fan speed switches from high to low value. The results also show that the supply air of the internal evaporative cooler has higher humidity content than direct evaporative cooler which makes it a good humidifier in cold storages where humidly close to saturation is required. © 2015 Elsevier Ltd All rights reserved.
Khabaz A.,Majmaah University
Construction and Building Materials | Year: 2016
The efficiency of hardened composite of Steel Fiber Reinforced Concrete (SFRC) is mainly related to the ability of its components to work together homogeneously. This homogeneously work of SFRC components might be obtained through sufficient bond between the fiber and the concrete matrix at its contact points on the interface surfaces. Usually, if a smooth and straight steel fiber is embedded in concrete matrix and subjected to tensile force, only weak bond may obtain at the interface between the fiber and the concrete. This weak bond decreases gradually parallel with increasing the value of the applied tensile force in the pull-out test, and the fiber can't develop its yield strength, whereas debond length increases toward the depth of the concrete along the embedded length of the fiber until failure occurs in bond strength between the fiber and the concrete, then the fiber pulls out of the concrete through frictional sliding movement. The fracture mechanism of bond strength between the fiber and the concrete might be observed through pull-out tests. To enhance the bond strength performance of the fiber without change the concrete mix properties, it is necessary to find sophisticated form for the fiber such as end hooks. Monitoring of impact of hooked ends on mechanical behavior of steel fiber in concrete is observed during this research, where various pull-out experiments of single steel fiber in two forms (straight and hooked ends) are set using different values of embedded fiber length in concrete matrix. As well as computer simulations of single steel fiber with hooked ends embedded in concrete matrix are created using finite element model to monitor the development of stresses in different directions. Nonlinear results with contour maps and curves of different types of stresses are also obtained from the computer simulations, and numerical evaluation of the impact of enhancing the steel fiber shape has been done through this research. © 2016 Elsevier Ltd. All rights reserved.
Huda Z.,Majmaah University |
Edi P.,King Fahd University of Petroleum and Minerals
Materials and Design | Year: 2013
This article reviews the advances in the materials selection for applications in structures and engines of current and future supersonic aircrafts. A brief overview of configuration design of the supersonic aircrafts is first given; which also includes techniques to improve configuration design for future supersonic aircrafts. The operating and ambient environmental conditions during supersonic flight and the resulting material requirements have been discussed; and consequently various aerospace aluminum alloys, titanium alloys, superalloys, and composites have been recommended. Finally, a new materials-selection chart is presented that would enable aerospace designers to select appropriate materials for application in high-performance current and future supersonic/hypersonic aircrafts. © 2012 Elsevier Ltd.
Tlili I.,Majmaah University
Renewable and Sustainable Energy Reviews | Year: 2012
Maximum power and efficiency at the maximum power point of an endoreversible Stirling heat engine with finite heat capacitance rate of external fluids in the heat source/sink reservoirs with regenerative losses are treated. It was found that the thermal efficiency depends on the regenerator effectiveness and the internal irreversibility resulting from the working fluid for a given value of reservoir temperature. It was also concluded that it is desirable to have larger heat capacity of the heat sink in comparison to the heat source reservoir for higher maximum power output and lower heat input. © 2012 Elsevier Ltd. All rights reserved.