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- 저자 : Hajmohammad, Mohammad Hadi (검색결과 3 건)
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Hajmohammad, Mohammad Hadi,Zarei, Mohammad Sharif,Farrokhian, Ahmad,Kolahchi, Reza Techno-Press 2018 Advances in nano research Vol.6 No.4
A layerwise shear deformation theory is applied in this paper for buckling analysis of piezoelectric truncated conical shell. The core is a multiphase nanocomposite reinforced by carbon nanotubes (CNTs) and carbon fibers. The top and bottom face sheets are piezoelectric subjected to 3D electric field and external voltage. The Halpin-Tsai model is used for obtaining the effective moisture and temperature dependent material properties of the core. The proposed layerwise theory is based on Mindlin's first-order shear deformation theory in each layer and results for a laminated truncated conical shell with three layers considering the continuity boundary condition. Applying energy method, the coupled motion equations are derived and analyzed using differential quadrature method (DQM) for different boundary conditions. The influences of some parameters such as boundary conditions, CNTs weight percent, cone semi vertex angle, geometrical parameters, moisture and temperature changes and external voltage are investigated on the buckling load of the smart structure. The results show that enhancing the CNTs weight percent, the buckling load increases. Furthermore, increasing the moisture and temperature changes decreases the buckling load.
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Esfe Mohammad Hemmat,Hajmohammad Hadi,Motallebi Seyed Majid,Toghraie Davood 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.1
In this study, optimization of ZnO/EG nanofl uids was investigated to increase effi ciency and reduce costs. To determine the effi ciency of nanofl uid, the defi nition of Mouromtseff number was used. The cost of nanofl uid in terms of the volume fraction of nanoparticles ( φ ) was determined. Then, Mouromtseff functions and costs were calculated by response surface methodology (RSM) with regression up to 96%. To determine the minimum cost and maximum effi ciency in terms of Mouromtseff number, a non-dominated sorting genetic algorithm (NSGA II) which is powerful in achieving optimal response was employed. In the end, the Pareto front, optimal values of Mouromtseff , and the minimum corresponding cost were obtained. Also, for achieving an optimal pattern of minimum cost in terms of maximum thermal effi ciency, a suitable correlation was presented. The results show that to achieve maximum thermal effi ciency, the minimum cost is $ 360 per liter and also the minimum cost to achieve the optimal effi ciency coeffi cient is in φ = 0.5%. Nanofl uid optimization can also reduce nanofl uid costs by up to 10%.
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Minimum-weight design of stiffened shell under hydrostatic pressure by genetic algorithm
A.R. Ghasemi,M.H. Hajmohammad 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.1
In this paper, optimization of cylindrical shells under external pressure to minimize its weight has been studied. Buckling equations are based on standard of ABS underwater vehicles. Dimension and type of circumferential stiffeners, and its distance from each other are assumed as variables of optimization problem. Considering the extent of these variables, genetic algorithms have been used for optimization. To study the effect of hydrostatic pressure on the shell and its fabrication according to the existing standards, geometrical and construction as well as stress and buckling constraints have been used in optimization algorithm and also penalty functions are applied to eliminate weak model. Finally, the best model which has the minimum weight considering the applied pressure has been presented.
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