Finding minimum-cost flows by double scaling

Several researchers have recently developed new techniques that give fast algorithms for the minimum-cost flow problem. In this paper we combine several of these techniques to yield an algorithm running in O(nm(log logU) log(nC)) time on networks withn vertices,m edges, maximum arc capacityU, and maximum arc cost magnitudeC. The major techniques used are the capacity-scaling approach of Edmonds and Karp, the excess-scaling approach of Ahuja and Orlin, the cost-scaling approach of Goldberg and Tarjan, and the dynamic tree data structure of Sleator and Tarjan. For nonsparse graphs with large maximum arc capacity, we obtain a similar but slightly better bound. We also obtain a slightly better bound for the (noncapacitated) transportation problem. In addition, we discuss a capacity-bounding approach to the minimum-cost flow problem.Research partially supported by an NSF Presidential Young Investigator Fellowship, Contract 8451517ECS, and grants from Analog Devices, Apple Computer Inc., and Prime Computer.On leave from Indian Institute of Technology, Kanpur, India.Research partially supported by an NSF Presidential Young Investigator Award.Research at Princeton University partially supported by National Science Foundation Grant DCR-8605962 and Office of Naval Research Contract N00014-87-K-0467.     

地下矿山运输系统建模与仿真

系统仿真是系统工程领域的研究热点之一.针对大型地下矿山的运输这一庞大而复杂的系统,以云南锡业集团松树脚矿1360水平运输系统为研究对象,应用离散事件仿真原理,建立了运输系统模型.通过对某些运输参数的调整,确定了其最优的车辆分配,分析了运输系统效率,对该运输系统的运输能力做出了科学的评估.     

叶脉脉序与资源输运模式

本文讨论了单源的资源输运 ,提出了一种利用模仿叶脉脉系优化输运模式的方法 .     

A fuzzy clustering approach to real-time demand-responsive bus dispatching control

Quick response (QR) to passenger needs is a key objective for advanced public transportation systems (APTS), and it has become increasingly important for contemporary metropolitan bus operations to gain a competitive advantage over private transportation. This paper presents a real-time control methodology for demand-responsive bus operations that respond quickly to passenger needs. The proposed method primarily involves two levels of functionality: (1) short-term forecasting of passenger demands using time-series prediction models, and (2) identification of service strategies coupled with the associated bus service segments using fuzzy clustering technologies in response to variances in passenger demand attributes and traffic conditions. The proposed bus operations method identifies the demand-responsive vehicle service strategies primarily according to the predicted up-to-date attributes of passengers’ demands, rather than deterministic passenger arrival rates, which were generally used in previous literature. In addition, the variation of traffic conditions along bus lines is considered in the proposed method. Results from numerical studies using real data of passengers’ demands, including passenger volume at each bus stop and the passenger origin-destination (O-D) patterns, are presented to demonstrate the effectiveness of the proposed method for real-world applications.     

缺省指派问题及其求解算法

在研究周良泽于1998年首先提出的最短时限最少耗费缺省指派问题基础上，从对称的角度给出了缺省指派问题的两种不同提法：拟从m个人中派出β个人去干n件事中的卢件事(β≤min{m，n}，每件事由一个人完成)。已知第i人做第j事的时间为tij。第i人做第j事的耗费为pu,i=1，2，…，m；j=1，2，…，n。问派出哪β个人去完成哪卢件事，才能使得：(1)在最短时限内完成n件事中的β件事，并且在满足最短时限前提条件下总耗费最少?(2)以最少总耗费完成n件事中的β件事，并且在满足总耗费最少前提条件下完成时限最短?给出了求解该问题的数值算法，证明了算法的理论依据，并举例说明算法的应用。     

Network Design for Express Shipment Delivery

Service network design problems arise at airlines (passenger and cargo), trucking companies, railroads, etc., wherever there is a need to determine cost minimizing routes and schedules, given constraints on resource availability and level of service. We focus on a particular service network design application, namely, the express shipment delivery problem, and we develop models and a solution technique designed specifically for large-scale express delivery problems with time windows. Using data from an express delivery company, we demonstrate that our approach can produce savings in total operating costs and provide a valuable tool for making decisions at strategic and tactical levels.     

受时间约束的运输问题求解的一种算法

本针对受时间约束的运输问题，提出了一种基于表上作业法的优化求解算法，并用算例说明了该算法的求解过程。     

城市公路交通塞车预警数学模型

本文针对城市公路交通"塞车"现象,以数学理论方法为基础,提出了有效的城市公路塞车预警数学模型,以该数学模型为核心建立系统、科学的公路交通信息处理方法.实时、准确、科学地监测、预报城市公路交通状况.目的在于减少城市公路塞车,改善城市交通管理质量,提高城市交通服务功能.这对城市交通建设与发展具有重要的意义.     

Utilization of Low-grade Iron Ore in Ammonia Decomposition

Due to its cleanliness, fast energy cycle, and convenience of energy conversion, hydrogen has been regarded as the new energy source. Conventional process to produce hydrogen yield large amount of CO as byproduct. Moreover, the hydrogen storage and transportation have become the drawbacks in hydrogen economy. Thus, there has been increased interest in the hydrogen transportation medium as alternatives from the conventional process to produce and transport hydrogen. Ammonia has drawn worldwide attention as the most reliable hydrogen transportation medium. Through the decomposition of ammonia, hydrogen and nitrogen gas were produces as the byproduct without any CO or CO₂ emission. In this experiment, the ore were introduced as the medium for ammonia decomposition. The ore were put into quartz tube reactor and were dehydrated at 400 °C for 1 hour, then hydrogen reduced for 2 hours before and undergone ammonia decomposition at 500-700 °C for 3 hours. The effects of temperature to the % conversion of ammonia decomposition were also studied. Ammonia decomposition at higher temperature gives higher conversion. As seen in the results, the NH₃ conversion decreased with increasing time and the value after 3 hours of reaction increased in the sequence of 500 °C<600 °C< 700 °C. During ammonia decomposition, nitriding of iron occurred. The relation between temperature and the nitriding potential, K_N is also investigated. The purpose of this study is to investigate the utilization of low-grade ore as medium for ammonia decomposition to produce hydrogen.     

Co/C微波吸收性能及Co/C-聚氨酯相变复合材料的微波-热转换性能

通过热解金属有机骨架ZIF-67的方法成功制备了具有优异微波吸收性能的Co/C碳基复合材料。 在600 ℃热解温度下获得的吸收剂质量分数为35% 的样品,最小反射损耗可达到-54.30 dB,其厚度仅为1.75 mm。 通过分析样品的损耗能力和阻抗匹配等微波吸收特性,发现复合材料中的骨架结构等对其阻抗匹配性能有非常大的影响。 并通过原位复合的方法制备了分散均匀的Co/C-PU相变复合材料,初步研究了其微波-热转换性能。 实验表明,微波吸收剂的添加量对其微波-热转换性能影响显著,发热效率随添加量成倍升高。 本文研究的Co/C-PU相变复合材料在电磁屏蔽、雷达红外兼容隐身等方面具有很大的应用潜力。 此外,固固相变材料结合微波热效应的快速高效等特点,用于储能或者其他热应用也有独特的优势。