Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NS...Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NSGA-Ⅱ), is applied on a spaceborne SAR antenna pattern design. The system consists of two objective functions with two constraints. Pareto fronts are generated as a result of multi-objective optimization. After being validated by a test problem ZDT4, the algorithms are used to synthesize spaceborne SAR antenna radiation pattern. The good results with low Ambi- guity-to-Signal Ratio (ASR) and high directivity are obtained in the paper.展开更多
针对货物运输结构不合理的问题,在系统分析长江经济带三大经济圈多式联运网络现状的基础上,构建以运输成本、运输时间和碳排放量最小为目标的多目标规划数学模型。运用带精英策略的非支配排序遗传算法(elitist non-dominated sorting ge...针对货物运输结构不合理的问题,在系统分析长江经济带三大经济圈多式联运网络现状的基础上,构建以运输成本、运输时间和碳排放量最小为目标的多目标规划数学模型。运用带精英策略的非支配排序遗传算法(elitist non-dominated sorting genetic algorithm,NSGA-Ⅱ)与理想点结合的算法进行求解,获得问题的Pareto最优解集,并采用逼近理想解排序法(technique for order preference by similarity to an ideal solution,TOPSIS)从Pareto最优解集中选出最优方案。选择长江经济带上的港口城市为起讫点和中转节点,构建包括公路、铁路、水路等3种运输方式的多式联运网络。以宜宾至上海的货流为例,验证模型和算法的有效性。求解结果表明:使用改进NSGA-Ⅱ与TOPSIS结合的求解方法得到的优化方案与仅使用改进的NSGA-II得到的方案相比,平均运输成本降低了16.98%,平均碳排放量减少了2.39%,平均运输时间缩短了5.79%,平均重要程度增加了7.85%。研究可以为多式联运网络规划与优化设计提供借鉴。展开更多
Based on the improved interpolating moving least-squares （ⅡMLS） method and the Galerkin weak form, an improved interpolating element-free Galerkin （ⅡEFG） method is presented for two-dimensional elasticity proble...Based on the improved interpolating moving least-squares （ⅡMLS） method and the Galerkin weak form, an improved interpolating element-free Galerkin （ⅡEFG） method is presented for two-dimensional elasticity problems in this paper. Compared with the interpolating moving least-squares （IMLS） method presented by Lancaster, the ⅡMLS method uses the nonsingular weight function. The number of unknown coefficients in the trial function of the ⅡMLS method is less than that of the MLS approximation and the shape function of the ⅡMLS method satisfies the property of Kronecker δ function. Thus in the ⅡEFG method, the essential boundary conditions can be applied directly and easily, then the numerical solutions can be obtained with higher precision than those obtained by the interpolating element-free Galerkin （IEFG） method. For the purposes of demonstration, four numerical examples are solved using the ⅡEFG method.展开更多
文摘Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NSGA-Ⅱ), is applied on a spaceborne SAR antenna pattern design. The system consists of two objective functions with two constraints. Pareto fronts are generated as a result of multi-objective optimization. After being validated by a test problem ZDT4, the algorithms are used to synthesize spaceborne SAR antenna radiation pattern. The good results with low Ambi- guity-to-Signal Ratio (ASR) and high directivity are obtained in the paper.
文摘针对货物运输结构不合理的问题,在系统分析长江经济带三大经济圈多式联运网络现状的基础上,构建以运输成本、运输时间和碳排放量最小为目标的多目标规划数学模型。运用带精英策略的非支配排序遗传算法(elitist non-dominated sorting genetic algorithm,NSGA-Ⅱ)与理想点结合的算法进行求解,获得问题的Pareto最优解集,并采用逼近理想解排序法(technique for order preference by similarity to an ideal solution,TOPSIS)从Pareto最优解集中选出最优方案。选择长江经济带上的港口城市为起讫点和中转节点,构建包括公路、铁路、水路等3种运输方式的多式联运网络。以宜宾至上海的货流为例,验证模型和算法的有效性。求解结果表明:使用改进NSGA-Ⅱ与TOPSIS结合的求解方法得到的优化方案与仅使用改进的NSGA-II得到的方案相比,平均运输成本降低了16.98%,平均碳排放量减少了2.39%,平均运输时间缩短了5.79%,平均重要程度增加了7.85%。研究可以为多式联运网络规划与优化设计提供借鉴。
基金Project supported by the National Natural Science Foundation of China(Grant No.11171208)the Shanghai Leading Academic Discipline Project,China(Grant No.S30106)
文摘Based on the improved interpolating moving least-squares （ⅡMLS） method and the Galerkin weak form, an improved interpolating element-free Galerkin （ⅡEFG） method is presented for two-dimensional elasticity problems in this paper. Compared with the interpolating moving least-squares （IMLS） method presented by Lancaster, the ⅡMLS method uses the nonsingular weight function. The number of unknown coefficients in the trial function of the ⅡMLS method is less than that of the MLS approximation and the shape function of the ⅡMLS method satisfies the property of Kronecker δ function. Thus in the ⅡEFG method, the essential boundary conditions can be applied directly and easily, then the numerical solutions can be obtained with higher precision than those obtained by the interpolating element-free Galerkin （IEFG） method. For the purposes of demonstration, four numerical examples are solved using the ⅡEFG method.
