Reference Point Based Multi-Objective Optimization of Reservoir Operation: a Comparison of Three Algorithms

Traditional multi-objective evolutionary algorithms treat each objective equally and search randomly in all solution spaces without using preference information. This might reduce the search efficiency and quality of solutions preferred by decision makers, especially when solving problems with complicated properties or many objectives. Three reference point based algorithms which adopt preference information in optimization progress, e.g., R-NSGA-II, r-NSGA-II and g-NSGA-II, have been shown to be effective in finding more preferred solutions in theoretical test problems. However, more efforts are needed to test their effectiveness in real-world problems. This study conducts a comparison of the above three algorithms with a standard algorithm NSGA-II on a reservoir operation problem to demonstrate their performance in improving the search efficiency and quality of preferred solutions. Under the same calculation times of the objective functions, Pareto optimal solutions of the four algorithms are used in the empirical comparison in terms of the approximation to the preferred solutions. Three performance indicators are then adopted for further comparison. Results show that R-NSGA-II and r-NSGA-II can improve the search efficiency and quality of preferred solutions. The convergence and diversity of their solutions in the concerned region are better than NSGA-II, and the closeness degree to the reference point can be increased by 42.8%, and moreover the number of preferred solutions can be increased by more than 3 times when part of objectives are preferred. By contrast, g-NSGA-II shows worse performance. This study exhibits the performance of three reference point based algorithms and provides insights in algorithm selection for multi-objective reservoir optimization problems.

     

中关村软件园巨型光盘预应力空间钢索结构张拉施工技术

中关村软件园软件广场光盘结构属车辐式双层索系，其中含径向索、斜拉索和缆风索共288根。空间索系张拉施工难点是各类索的受力相互影响，一根索内力的改变将带来其他索力的连锁变化。针对此难点对钢索张拉顺序及张拉施工模拟分析、钢索张拉的具体步骤及采用的工装设备、钢索张拉监测，进行了科学的策划，最后取得了成功。     

Surface acoustic wave properties in 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3 multidomain single crystal poled along [001]c

Surface acoustic wave propagation in a 0.955Pb (Zn_1/3Nb_2/3)O₃-0.045PbTiO₃ multidomain single crystal poled along [001]_c has been analyzed theoretically using Christoffel wave equations. From the measured experimental data, the orientational dependence of surface acoustic wave phase velocities, electromechanical coupling coefficients and power flow angles was calculated. The results showed that surface acoustic wave propagations of 0.955Pb (Zn_1/3Nb_2/3)O₃-0.045PbTiO₃ are poor than 0.93Pb(Zn_1/3Nb_2/3)O₃-0.07PbTiO₃ crystal slightly. However, the 0.955Pb (Zn_1/3Nb_2/3)O₃-0.045PbTiO₃ single crystals have higher rhombohedral-tetragonal phase transition temperature and much stabler electromechanical properties. This may expand applications range of SAW devices.     

广域环境下基于Q型因子学习方法的电网节点聚合规律?

大规模可再生能源的并网以及电力市场解除管制的改革,使传统集中式的节点电压在线安全分析、调度与控制方法面临困境。对此,在电网运行状况全景过程化可观测条件下,提出了渐进学习的电网节点聚合的新调控理论,通过电网"局部自治与集中调控互融"的调控方式解决电网的调控问题。提出了基于Q型因子学习的电网节点聚合规律的挖掘方法,根据传统节点电压方程及发电机、负荷的等值模型得到广域环境下节点电压向量与电势之间的解析关系,推导出连续2个量测时刻下节点电压幅值变化的影响因子,并对其进行过程化的Q型因子学习,进而得到电压幅值具有一致变化的节点聚合规律。通过对德州电网的仿真分析,验证了所提方法的准确性及有效性。     

海南电网分布式光伏消纳能力评估

利用DIgSILENT/PowerFactory仿真软件,从电能质量、经济运行、继电保护等方面研究了分布式光伏接入对海南电网的影响。基于系统的安全经济运行约束,对海南电网常见典型接线形式的多种运行方式进行了消纳能力评估。结果表明,各类典型配电网的消纳能力为相应配电网峰荷的20%~40%;制约配电网消纳光伏发电的主要因素为中压配电网功率因数下降和低压配电网三相不平衡。     

Thermal,morphology, and mechanical properties of polyphenylene sulfide/polyether sulfone binary blends

Blends of polyether sulfone (PES) and polyphenylene sulfide (PPS) with different weight ratios (10/0, 8/2, 6/4, 4/6, 2/8, 0/10) were prepared by melt extrusion using a twin‐screw extruder. In this work, the thermal stabilities of blends were evaluated by thermogravimetric analysis and the dynamic mechanical properties were investigated by means of dynamic mechanical analysis. The fracture surfaces were observed with a scanning electron microscopy. In addition, the mechanical property tests were also carried out and the impact strength of blends was improved by 110% compared to that of pure PPS. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41703.     

基于波长敏感的耦合器动态增益平坦L波段EDFA理论与实验

掺铒光纤放大器(EDFA)的增益平坦化是波分复用(WDM)系统的重要问题,文章通过理论和实验提出一种新型的增益平坦滤波器,即一种耦合比随波长变化的耦合器与偏振控制器(PC)构成光纤环形镜,调节光纤环形镜内的PC的状态,从而改变光纤环形镜的反射谱线的位置和深度,使其匹配EDFA的增益谱,实现对L波段EDFA增益平坦,实验结论得出,平坦后的光谱在1562nm~1605nm带宽内增益平坦度为±0.7d B。     

SDN/NFV技术在宽带IP城域网中的应用

针对传统宽带IP城域网面临的挑战和问题,基于软件定义和虚拟化等技术,文章提出宽带IP城域网络需要从简单的连接型网络向智能的功能型网络演进的思路和架构,并给出新形势下的应用场景,从而满足其智能化运营的发展需求。     

水平井光纤视像检测技术研究

简要介绍了井下视像检测系统结构及配套工艺,通过室内试验及现场应用,证实其在井筒套管损坏分析的准确性,突出其在提升修井效率上的重要性,分析了影响检测效果的不利因素并提出应对措施。     

基于DIC网格试验法的探究与应用

网格试验在汽车厂冲压生产领域具有重要的指导作用,目前网格试验方法除了传统的手工测量方法以外,随着数字化影像技术的发展,数字化的网格试验方法(DIC)也得到了广泛的应用,通过材料成形极限曲线并结合材料的性能,分析与探讨了冲压缺陷产生原因及改进措施。事实证明DIC网格分析方法可直接反映测量区域变形行为,是进行大型覆盖件冲压成形分析和改进成形缺陷的有效方法。