A branch-and-price algorithm to solve the molten iron allocation problem in iron and steel industry

The molten iron allocation problem (MIAP) is to allocate molten iron from blast furnaces to steel-making furnaces. The allocation needs to observe the release times of the molten iron defined by the draining plan of the blast furnaces and the transport time between the iron-making and steel-making stages. Time window constraints for processing the molten iron must be satisfied to avoid freezing. The objective is to find a schedule with minimum total weighted completion time. This objective reflects the practical consideration of improving steel-making efficiency and reducing operation cost caused by the need for reheating. Such a problem can be viewed as a parallel machine scheduling problem with time windows which is known to be NP-hard. In this paper, we first formulate the molten iron allocation problem as an integer programming model and then reformulate it as a set partitioning model by applying the Dantzig–Wolfe decomposition. We solve the problem using a column generation-based branch-and-price algorithm. Since the subproblem of column generation is still NP-hard, we propose a state-space relaxation-based dynamic programming algorithm for the subproblem. Computational experiments demonstrate that the proposed algorithm is capable of solving problems with up to 100 jobs to optimality within a reasonable computation time.     

乌东德水电站建设岩石力学工程问题科技创新的思考

乌东德工程因所处河谷复杂严峻的自然环境条件及区域地质地震背景,面临枢纽工程布置、高陡边坡治理、大坝建基岩体选择与建基面确定、复杂地下洞室群安全施工、远程泥石流灾害预警、近坝大型滑坡体及水库岸坡安全稳定等工程地质和岩石力学关键问题的挑战。建设单位、设计单位、科研单位与技术咨询单位的众多工程师和科学家协同攻关,艰辛探索,攻克了工程建设过程中一系列的岩石力学关键技术问题,创新了遵循岩石力学规律特性的工程管理方法,促进了乌东德工程安全优质建设。本文结合工程建设进展,总结了乌东德工程岩石力学关键技术的科技创新,展望了绿色水电开发、建设、运行科技创新的方向。     

基于3D可视化GIS的前视参考图生成方法

基于匹配识别的导航系统不能缺少匹配参考图的支持,制备前视匹配参考图更是前视目标匹配识别的一个关键环节。为了利用航空航天图象信息制备出有效的前视匹配识别所需的参考图,提出了基于3D可视化GIS的前视参考图生成方法,介绍了该方法总体思路,分析了其中的三维数据制备、目标区三维场景生成和前视匹配序列参考图生成等关键环节,给出了部分制备的参考图与实时图的匹配实验结果。实验结果表明,利用这种方法制备的前视参考图可以满足前视匹配识别的需求。     

High Phase Purity of Large‐Sized 1T′‐MoS2 Monolayers with 2D Superconductivity

The development of transition metal dichalcogenides has greatly accelerated research in the 2D realm, especially for layered MoS₂. Crucially, the metallic MoS₂ monolayer is an ideal platform in which novel topological electronic states can emerge and also exhibits excellent energy conversion and storage properties. However, as its intrinsic metallic phase, little is known about the nature of 2D 1T′‐MoS₂, probably because of limited phase uniformity (<80%) and lateral size (usually <1 µm) in produced materials. Herein, solution processing to realize high phase‐purity 1T′‐MoS₂ monolayers with large lateral size is demonstrated. Direct chemical exfoliation of millimeter‐sized 1T′ crystal is introduced to successfully produce a high‐yield of 1T′‐MoS₂ monolayers with over 97% phase purity and unprecedentedly large size up to tens of micrometers. Furthermore, the large‐sized and high‐quality 1T′‐MoS₂ nanosheets exhibit clear intrinsic superconductivity among all thicknesses down to monolayer, accompanied by a slow drop of transition temperature from 6.1 to 3.0 K. Prominently, unconventional superconducting behavior with upper critical field far beyond the Pauli limit is observed in the centrosymmetric 1T′‐MoS₂ structure. The results open up an ideal approach to explore the properties of 2D metastable polymorphic materials.     

柔性直流控制保护系统方案及其工程应用

结合厦门柔性直流输电示范工程,对柔性直流控制保护系统方案及其工程应用进行了研究,包括控制保护系统的分层结构、极控制系统的基本控制策略、控制系统结构、极控制系统与阀控制系统间的接口特性,以及直流保护系统功能的配置情况。为了验证极控制系统、阀控制系统及换流阀之间工作的正确性,防止首次有源解锁出现大电流损坏换流阀,针对真双极拓扑结构系统,提出了无源逆变试验方案,现场试验结果证明了阀组触发相序的正确性,实现了对控制系统延时的完全补偿。无功和有功功率阶跃试验结果表明,控制系统在性能上和速度上满足快速性、可靠性、灵活性要求。直流保护跳闸试验结果表明,保护逻辑功能正确,换流阀正确闭锁、断路器正确跳闸。     

前视红外图像质量评价指标研究

实时图像质量严重影响景象匹配性能,但目前尚无通用可行的评价标准来衡量其质量,而且不同匹配算法对各种图像特征的敏感性有差异,需要根据算法对图像质量评价问题展开分类研究。文中首先给出了图像质量评价的工作方式,然后从成像质量和目标凸显程度两个方面进行指标分析,提出了包括信噪比、模糊度、目标局部凸显程度和全局凸显程度在内的指标体系。实验表明,各指标与匹配性能之间具有单调一致关系。     

沙棘果油中维生素E的色质谱分析

本研究应用柱色谱预分离、气相色谱与质谱联用技术,在国内首次对野生植物沙棘果油中所含的维生素E类组份进行了系统的分析鉴定.除分析出了α、β、γ、δ——生育酚外,还用质谱碎片解析法推断出了四种未有报道的新组份,为沙棘果油在化妆品及医药方面的应用提供了可靠的依据.     

An efficient optimal solution to the coil sequencing problem in electro-galvanizing line

This paper studies a coil sequencing problem that arises from electro-galvanizing line in steel industry. The problem is to find a processing sequence of steel coils such that the switching costs between consecutive coils are minimized while satisfying technical restrictions. The problem can be decomposed into several independent sub-problems, each corresponding to a turn which is a sequence of continuously processed coils with the same post-processing requirement. The coils in each turn can be further divided into several families each consisting of the coils with the same width. Based on analysis of the problem properties, a two-phase polynomial algorithm is developed to obtain an optimal turn. The sequence of coils in a family with given boundary coils (first and last coils) is determined in the first phase using a polynomial dynamic programming algorithm. In the second phase, the optimal turn is formed by another polynomial dynamic programming algorithm which takes the boundary coils for each family as state variables. The efficiency of the proposed algorithm is demonstrated through computational experiments.     

Cyclic scheduling of a single hoist in extended electroplating lines: a comprehensive integer programming solution

This paper studies the single-hoist cyclic scheduling problem in electroplating systems with two extended features. One extension is that the products must visit some processing tanks more than once (multi-function tanks). Another is that more than one identical tank is used at some stages. These extensions are common in practical electroplating lines and can increase the lines' processing capacity. However, they make the hoist scheduling problem more complicated and little research has been done to optimize the hoist moves in such extended practical systems. In this paper, we develop a comprehensive mixed integer linear programming model to find optimal solutions to the single-hoist cyclic scheduling problem for electroplating lines with these extensions. Examples are given to demonstrate the effectiveness of the model in different types of problems.