基于自适应模拟退火遗传算法的多杂质用水网络设计

水资源的短缺和环境污染的日益严重，对过程工业提出了减少新鲜水用量和废水排放量的要求，且通常废水中都含有多种污染物，由此本文提出了考虑回用的多杂质用水网络设计。不但建立了多杂质用水网络超结构MINLP模型，而且针对MINLP问题求解困难的现状，开发了自适应模拟退火遗传算法。实例研究结果表明该算法可以找到全局最优解且计算时间可满足要求。另外，该算法可有效避免陷入局部最优，也不要求提供初始可行解。     

Propagation properties of foreshock cavitons: Cluster observations

Foreshock cavitons are transient phenomena observed in the terrestrial foreshock region. They are characterized by a simultaneous depression of magnetic field magnitude and plasma density, which are bounded with enhancements of these two parameters and surrounded by ultralow frequency(ULF) waves. Previous studies focused on the interplanetary magnetic field(IMF) conditions, solar wind(SW) conditions, and the growth of the foreshock waves related to the generation of foreshock cavitons. Previously, a multipoint spacecraft analysis method using Cluster data was applied to analyze only two foreshock cavitons, and this method did not consider uncertainties. In this study, multipoint spacecraft analysis methods, including the timing method, the minimum directional derivative(MDD) method, and the spatiotemporal difference(STD) method are applied to determine the velocity in both spacecraft and solar wind frames. The propagation properties show good agreement with previous results from simulations and observations that most cavitons move sunward in the solar wind frame, with the velocities larger than the Alfvén speed. The propagation properties of foreshock cavitons support the formation mechanism of cavitons in previous simulations, which suggested that cavitons are formed due to the nonlinear evolution of compressive ULF waves. We find that there is clear decreasing trend between the size of cavitons and their velocity in the solar wind frame. In addition, the timing method considering errors has been applied to study the evolution properties by comparing the velocities with errors of the leading and trailing edges, and we identify three stable cavitons and one contracting caviton, which has not been studied before.Most cavitons should remain stable when they travel toward the Earth's bow shock. The relationship between the size of foreshock cavitons and their distance from the bow shock is also discussed.