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551.
552.
随着军事技术的不断发展,编队在海上遂行任务时面临的空中威胁日益严峻,对空防御作战是海上编队面临的最为重要的作战样式之一,这对编队对空作战能力提出了新的挑战。在研究美军CEC的基础上,文章介绍了编队对空防御作战的军事需求,阐述了编队对空防御作战体系,并研究了编队舰载雷达组网和舰载预警机参与下编队的对空防御作战能力。 相似文献
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促进更多货流从公路转移到铁路是实现“双碳”目标的重要路径之一,也是推动铁路高质量发展的关键举措。鉴于此,本文以公铁货流转移量、铁路车流径路选择及编组去向等为主要决策变量,以公铁两网物流总成本极小化为目标,构建公铁货流转移量与铁路车流径路及列车编组计划联合优化模型,实现“公转铁”货流全过程、多阶段运输费用的数学表达,得到系统优化的OD间公铁货流转移量、车流走行径路和改编站点。针对模型的非线性特征,引入辅助0-1变量进行线性化,将其转化为混合整数线性规划模型,为验证模型有效性设计算例,借助数学规划优化器GUROBI进行求解。结果表明,模型可为公铁货流转移方案配置合理的接驳路径和列车编组方案;相较于既有研究,本文构建模型考虑了公铁两端的接驳转运费用和铁路车流集结与改编费用,使得“公转铁”物流总成本增加了约23.06%,转移货流量降低了约4.91%,更准确地描述了公铁货流转移过程,为制定“公转铁”运输方案和组织措施提供一定的理论依据。 相似文献
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In this study, we examine how the spatial distribution of housing supply impacts people’s residential choices and developers’ profitability. By optimally providing housing supply in a region, developers attempt to maximize their profits; on the other hand, if residents were given a chance to decide on housing supply, what patterns of housing supply they would prefer in order to maximize their consumer surpluses. This paper studies the interplay between these two perspectives. A nested multinomial-logit choice structure that encapsulates the bid-rent process is used to capture residents’ location and travel choices simultaneously, and the resultant rents at different locations. To investigate the optimal housing supply for these two stakeholders, we conduct sensitivity analyzes to explore the impact of different housing supply patterns on total rental profit and total consumer surplus. Specifically, analytical results are derived for a simple linear network with two residential locations and one destination under homogeneous and heterogeneous value(s) of time. The results of the sensitivity analyzes indicate that segregation of housing supplies at different locations for different income classes is, surprisingly, a “preferred” outcome by residents under consumer surplus maximization, whereas creating housing supply shortages at convenient locations is a natural outcome under housing profit maximization. These results provide insights on revealing the differences and tradeoffs in performance between these two different perspectives, and on where land use regulations may be needed to balance these two objectives. 相似文献
559.
Understanding people flow at a citywide level is critical for urban planning and commercial development. Thanks to the ubiquity of human location tracking devices, many studies on people mass movement with mobility logs have been conducted. However, high cost and severe privacy policy constraints still complicate utilization of these data in practice. There is no dataset that anyone can freely access, use, modify, and share for any purpose. To tackle this problem, we propose a novel dataset creation approach (called Open PFLOW) that continuously reports the spatiotemporal positions of all individual’s in urban areas based on open data. With fully consideration of the privacy protection, each entity in our dataset does not match the actual movement of any real person, so that the dataset can be totally open to public as part of data infrastructure. Because the result is shown at a disaggregate level, users can freely modify, process, and visualize the dataset for any purpose. We evaluate the accuracy of the dataset by comparing it with commercial datasets and traffic census indicates that it has a high correlation with mesh population and link-based traffic volume. 相似文献
560.
Since the 1970s and 80s, landlord port has been the dominant port financing model in western large and medium-sized container ports. In China, many prospective port projects have also explored a landlord port financing model. However, some evidence suggests that landlord port financing in China is a variant of the international mainstream landlord port financing model. Based on an explanation of their unique features and practices, this paper analyzes the Chinese quasi-landlord port financing model from a contract theory perspective, in which it can be viewed as a double-level principal–agent relationship and two-layer profit distribution contract with three participants: the state-owned assets administration department, the port investment company and the operators. Furthermore, the results show that in the Chinese quasi-landlord port financing model, whether in the case of both joint venture and port land lease (fixed rent), or in the case of both joint venture and port land transfer, the optimal incentive scheme is the same as in the international landlord port financing model with profit sharing rent or mixed rent. 相似文献