In this paper, the basic formulae for the semi-analytical graded FEM on FGM members are derived. Since FGM parameters vary along three space coordinates, the parameters can be integrated in mechanical equations. There...In this paper, the basic formulae for the semi-analytical graded FEM on FGM members are derived. Since FGM parameters vary along three space coordinates, the parameters can be integrated in mechanical equations. Therefore with the parameters of a given FGM plate, problems of FGM plate under various conditions can be solved. The approach uses 1D discretization to obtain 3D solutions, which is proven to be an effective numerical method for the mechanical analyses of FGM structures. Examples of FGM plates with complex shapes and various holes are presented.展开更多
The absorber is known to be vertical axisymmetric for a single-point wave energy converter （WEC）. The shape of the wetted surface usually has a great influence on the absorber＇s hydrodynamic characteristics which a...The absorber is known to be vertical axisymmetric for a single-point wave energy converter （WEC）. The shape of the wetted surface usually has a great influence on the absorber＇s hydrodynamic characteristics which are closely linked with the wave power conversion ability. For complex wetted surface, the hydrodynamic coefficients have been predicted traditionally by hydrodynamic software based on the BEM. However, for a systematic study of various parameters and geometries, they are too multifarious to generate so many models and data grids. This paper examines a semi-analytical method of decomposing the complex axisyrnmetric boundary into several ring-shaped and stepped surfaces based on the boundary discretization method （BDM） which overcomes the previous difficulties. In such case, by using the linear wave theory based on eigenfunction expansion matching method, the expressions of velocity potential in each domain, the added mass, radiation damping and wave excitation forces of the oscillating absorbers are obtained. The good astringency of the hydrodynamic coefficients and wave forces are obtained for various geometries when the discrete number reaches a certain value. The captured wave power for a same given draught and displacement for various geometries are calculated and compared. Numerical results show that the geometrical shape has great effect on the wave conversion performance of the absorber. For absorbers with the same outer radius and draught or displacement, the cylindrical type shows fantastic wave energy conversion ability at some given frequencies, while in the random sea wave, the parabolic and conical ones have better stabilization and applicability in wave power conversion.展开更多
在多种群并行遗传算法(Multi-population Parallel Genetic A lgorithm)的基础上,将复合形法引入遗传算法来反映决策者对各目标函数的偏好信息,提出了一种新的结合复合形法的混合多目标遗传算法。算法将群体划分为相等规模的子群体,每...在多种群并行遗传算法(Multi-population Parallel Genetic A lgorithm)的基础上,将复合形法引入遗传算法来反映决策者对各目标函数的偏好信息,提出了一种新的结合复合形法的混合多目标遗传算法。算法将群体划分为相等规模的子群体,每个子群体对应于相应的子目标函数,各子群体具有独自的适应度评价函数,杂交和变异跨子群体边界执行。将复合形法引入遗传算法,通过次重要目标函数对应的子群体向重要目标函数对应的子群体进行压缩和缩转操作,使得综合后的基因在杂交和变异操作中向着更利于重要目标函数的群体方向进化,从而使获得的Pareto最优解集偏好于重要目标函数。通过数值仿真计算,结合复合形法的混合多目标遗传算法得到了某种程度上较好的协调最优解,具有良好的性能,对于求解多目标优化问题是可行有效的。展开更多
基金Project supported by the National Natural Science Foundation of China (No. 10432030)
文摘In this paper, the basic formulae for the semi-analytical graded FEM on FGM members are derived. Since FGM parameters vary along three space coordinates, the parameters can be integrated in mechanical equations. Therefore with the parameters of a given FGM plate, problems of FGM plate under various conditions can be solved. The approach uses 1D discretization to obtain 3D solutions, which is proven to be an effective numerical method for the mechanical analyses of FGM structures. Examples of FGM plates with complex shapes and various holes are presented.
基金supported by the National Natural Science Foundation of China(Grant Nos.11572094,51579055 and 51509048)
文摘The absorber is known to be vertical axisymmetric for a single-point wave energy converter （WEC）. The shape of the wetted surface usually has a great influence on the absorber＇s hydrodynamic characteristics which are closely linked with the wave power conversion ability. For complex wetted surface, the hydrodynamic coefficients have been predicted traditionally by hydrodynamic software based on the BEM. However, for a systematic study of various parameters and geometries, they are too multifarious to generate so many models and data grids. This paper examines a semi-analytical method of decomposing the complex axisyrnmetric boundary into several ring-shaped and stepped surfaces based on the boundary discretization method （BDM） which overcomes the previous difficulties. In such case, by using the linear wave theory based on eigenfunction expansion matching method, the expressions of velocity potential in each domain, the added mass, radiation damping and wave excitation forces of the oscillating absorbers are obtained. The good astringency of the hydrodynamic coefficients and wave forces are obtained for various geometries when the discrete number reaches a certain value. The captured wave power for a same given draught and displacement for various geometries are calculated and compared. Numerical results show that the geometrical shape has great effect on the wave conversion performance of the absorber. For absorbers with the same outer radius and draught or displacement, the cylindrical type shows fantastic wave energy conversion ability at some given frequencies, while in the random sea wave, the parabolic and conical ones have better stabilization and applicability in wave power conversion.
文摘在多种群并行遗传算法(Multi-population Parallel Genetic A lgorithm)的基础上,将复合形法引入遗传算法来反映决策者对各目标函数的偏好信息,提出了一种新的结合复合形法的混合多目标遗传算法。算法将群体划分为相等规模的子群体,每个子群体对应于相应的子目标函数,各子群体具有独自的适应度评价函数,杂交和变异跨子群体边界执行。将复合形法引入遗传算法,通过次重要目标函数对应的子群体向重要目标函数对应的子群体进行压缩和缩转操作,使得综合后的基因在杂交和变异操作中向着更利于重要目标函数的群体方向进化,从而使获得的Pareto最优解集偏好于重要目标函数。通过数值仿真计算,结合复合形法的混合多目标遗传算法得到了某种程度上较好的协调最优解,具有良好的性能,对于求解多目标优化问题是可行有效的。
