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181.
Competition and disruption in a dynamic urban supply chain 总被引:1,自引:0,他引:1
Terry L. Friesz Ilsoo Lee Cheng-Chang Lin 《Transportation Research Part B: Methodological》2011,45(8):1212-1231
Rapid changes and complexities in business environments have stressed the importance of interactions between partners and competitors, leading supply chains to become the most important element of contemporary business environments. There is a concomitant need for foresight in describing supply chain performance in all operating environments, including those involving punctuated disruptions. Furthermore, the urban metropolis is now widely recognized to be an environment which is especially vulnerable to supply chain disruptions and for which integrated supply chain decisions can produce very substantial net benefits. Accordingly, this paper presents a dynamic supply chain network model formulated as a differential variational inequality; the model is fashioned to allow consideration of supply chain disruption threats to producers, freight carriers, and retail enterprises. The DVI is solved using a fixed-point algorithm, and a simple numerical example, introduced to illustrate how the impacts of supply chain disruptions may be quantified, is presented. 相似文献
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Terry L. Friesz Taeil Kim Changhyun Kwon Matthew A. Rigdon 《Transportation Research Part B: Methodological》2011,45(1):176-207
In this paper we present a dual-time-scale formulation of dynamic user equilibrium (DUE) with demand evolution. Our formulation belongs to the problem class that Pang and Stewart (2008) refer to as differential variational inequalities. It combines the within-day time scale for which route and departure time choices fluctuate in continuous time with the day-to-day time scale for which demand evolves in discrete time steps. Our formulation is consistent with the often told story that drivers adjust their travel demands at the end of every day based on their congestion experience during one or more previous days. We show that analysis of the within-day assignment model is tremendously simplified by expressing dynamic user equilibrium as a differential variational inequality. We also show there is a class of day-to-day demand growth models that allow the dual-time-scale formulation to be decomposed by time-stepping to yield a sequence of continuous time, single-day, dynamic user equilibrium problems. To solve the single-day DUE problems arising during time-stepping, it is necessary to repeatedly solve a dynamic network loading problem. We observe that the network loading phase of DUE computation generally constitutes a differential algebraic equation (DAE) system, and we show that the DAE system for network loading based on the link delay model (LDM) of Friesz et al. (1993) may be approximated by a system of ordinary differential equations (ODEs). That system of ODEs, as we demonstrate, may be efficiently solved using traditional numerical methods for such problems. To compute an actual dynamic user equilibrium, we introduce a continuous time fixed-point algorithm and prove its convergence for effective path delay operators that allow a limited type of nonmonotone path delay. We show that our DUE algorithm is compatible with network loading based on the LDM and the cell transmission model (CTM) due to Daganzo (1995). We provide a numerical example based on the much studied Sioux Falls network. 相似文献
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结合实际工程,针对低等级公路改扩建时涉及到的既有天桥或基于交通救援、战备应急等相关的桥梁进行顶升及改造的措施,依据其工程成果,为类似桥梁加固改造起到一定的指导作用。 相似文献
186.
为实现供水管网经济、可靠、科学的规划改扩建,给出一种基于记录时间较短、历史数据较少的用水量序列的GM(1,1)预测方法。该预测方法把原始用水量序列累加处理生成新序列后,用指数关系式拟合,通过构造参数矩阵,确定辩识参数,建立灰色模型的微分方程。通过对灰色预测方法建模机理的研究建立城市用水量预测GM(1,1)模型,并以东北某大型城市用水量为原始数据进行实际预测,模型精度检验的结果表明该模型的预测等级为高精度预测。该预测方法应用于S市的中长期用水量预测,为S市供水规划改扩建提供有效依据。 相似文献
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以上瑞高速公路怀新段第8合同段青山冲隧道为工程实例,针对左线出口端洞口浅埋偏压情况,为了节约工程投资,实施了反压回填的处治方案,采用数值模拟分析及现场监控量测数据分析了偏压隧道支护结构的受力状态和稳定性,可供类似工程参考. 相似文献
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陈清 《山东交通学院学报》2011,19(1):40-44
通过对四川省统筹城乡道路客运协调发展的研究,分析了四川省统筹城乡道路客运协调发展的现状与存在的主要问题,提出解决问题的对策与建议,对加快四川省统筹城乡道路客运协调发展方面有重要意义。 相似文献
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