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171.
172.
In this paper, we develop a novel stochastic multi-objective multi-mode transportation model for hub covering location problem under uncertainty. The transportation time between each pair of nodes is an uncertain parameter and also is influenced by a risk factor in the network. We extend the traditional comprehensive hub location problem by considering two new objective functions. So, our multi-objective model includes (i) minimization of total current investment costs and (ii) minimization of maximum transportation time between each origin–destination pair in the network. Besides, a novel multi-objective imperialist competitive algorithm (MOICA) is proposed to obtain the Pareto-optimal solutions of the problem. The performance of the proposed solution algorithm is compared with two well-known meta-heuristics, namely, non-dominated sorting genetic algorithm (NSGA-II) and Pareto archive evolution strategy (PAES). Computational results show that MOICA outperforms the other meta-heuristics. 相似文献
173.
Farzin Taghipourian Iraj Mahdavi Nezam Mahdavi-Amiri Ahmad Makui 《Applied Mathematical Modelling》2012
Hub location problem has been used in transportation network to exploit economies of scale. For example, a controversial issue in the planning of air transportation networks is inclement weather or emergency conditions. In this situation, hub facilities would not be able to provide a good service to their spoke nodes temporarily. Thus, some other kinds of predetermined underutilized facilities in the network are used as virtual hubs to host some or all connections of original hubs to recover the incurred incapacitation and increase network flexibility and demand flow. In such an unexpected situation, it is not unreasonable to expect that some information be imprecise or vague. To deal with this issue, fuzzy concept is used to pose a more realistic problem. Here, we present a fuzzy integer liner programming approach to propose a dynamic virtual hub location problem with the aim of minimizing transportation cost in the network. We examine the effectiveness of our model using the well-known CAB data set. 相似文献
174.
Dmitri Pavlov Svetla Slavova Richard J. Kryscio 《Methodology and Computing in Applied Probability》2009,11(2):249-265
This paper considers a non-parametric method for identifying intervals on the line where the relative risk of cases to controls
exceeds a pre-specified level. The method is based on the kth nearest neighbor (kNN) approach for density estimation. An asymptotic result is presented that yields an explicit formula
for constructing a confidence interval for the relative risk at a given point. Numerical simulations are used to compare this
approach with a kernel density estimation procedure. An application is made to a case-control study in which the relative
risk of motor vehicle crashes caused by female drivers is compared to male drivers in the state of Kentucky as a function
of age and then by time of day.
相似文献
175.
This article draws a bow from the fundamentals of the flame chemistry to combustion in engines. Aspects of radical chemistry, pollutant formation and combustion are highlighted. Concepts of current and future internal combustion engines are presented. A main focus lies on pollutant formation and reduction (CO2, CO, NOx, HC and soot). Finally, a vision of the future role of the internal combustion engine with respect to fuel cell and electrical engine is outlined. 相似文献
176.
本文讨论了在己有的通用电力电子仿真平台MATLAB和PSPICE基础上,建立CUK变换器电路级和系统级的电路仿真。 相似文献
177.
鄂尔多斯地区公路两侧土壤重金属污染特征 总被引:17,自引:0,他引:17
对内蒙古鄂尔多斯地区4个公路段土壤中的重金属元素(Pb、Cd、Cr、Cu、Hg、Zn、Ni)和类金属(As、Se)污染特征进行研究。结果表明:4个公路段都存在不同程度的土壤重金属污染,相对污染程度最低的东胜段公路而言,树林召段公路土壤中铬(Cr)存在显著性污染,棋盘井段公路土壤中汞(Hg)存在显著性污染,薛家湾段公路土壤中铬(Cr)和类金属砷(As)存在显著性污染。通过分析发现,虽然机动车辆的尾气排放能够造成公路土壤中的重金属污染,但是此次调查的4个公路段土壤中的重金属污染来源主要是机动车辆运载煤时的煤尘飘落以及当地的工业排废。所以应该以加强对运煤车辆管理和工业污染源的控制为着力点,治理和降低公路绿化及公路旁耕地中重金属污染。 相似文献
178.
采用开关磁阻电动机驱动电动汽车的可行性分析 总被引:1,自引:0,他引:1
根据电动汽车对电气驱动系统的特殊要求,分析了开关磁阻电动机的原理和特点,并与传统的直流电动机,异步电动机性能作了比较,得出结论,采用开关磁阻电动机是更为合理可行的方案之一,为电动汽车研制中的关键技术提供了可行性依据. 相似文献
179.
测功机为内燃机试验的重要设备,用于测试其转矩及油耗。介绍了一种新型的交流电力测功机的构成方案,应用双馈式交流异步电机作为测功发电机,同时兼具电动起动及冷磨功用。通过测量电机的电磁功率及角速度来间接测算电机转矩。系统运用了单片微型模糊控制技术,使该新型测功机能自动运行,可大大提高劳动效率,从而有可能取代非自动的测功机并将得到广泛的应用。 相似文献
180.
基于PLC的步进电动机控制系统的设计 总被引:2,自引:0,他引:2
本文选用三菱FX2N-48MR的PLC,设计了一种基于PLC和触摸屏的步进电动机控制系统,给出了该系统硬件电路设计方案,并分析了控制系统软件设计过程。调试结果表明,该方案能实现对步进电动机速度和方向的精确控制。 相似文献