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61.
The retail route design problem extends the capacitated vehicle routing problem with time windows by introducing several operational constraints, including order loading and delivery restrictions (last-in, first-out), order-dependent vehicle capacity, material handling limits at the warehouse, backhauling, and driving time bounds. In this paper, the problem is modeled on a directed network for an application associated with a major grocery chain. Because the corresponding mixed-integer program proved too difficult to solve with commercial software for real instances, we developed a greedy randomized adaptive search procedure (GRASP) augmented with tabu search to provide solutions. Testing was done using data sets provided Kroger, the largest grocery chain in the US, and benchmarked against a previously developed column generation algorithm. The results showed that cost reductions of $4887 per day or 5.58% per day on average, compared to Kroger’s corresponding solutions. 相似文献
62.
We consider two stochastic variants of the Share-a-Ride problem: one with stochastic travel times and one with stochastic delivery locations. Both variants are formulated as a two-stage stochastic programming model with recourse. The objective is to maximize the expected profit of serving a set of passengers and parcels using a set of homogeneous vehicles. Our solution methodology integrates an adaptive large neighborhood search heuristic and three sampling strategies for the scenario generation (fixed sample size sampling, sample average approximation, and sequential sampling procedure). A computational study is carried out to compare the proposed approaches. The results show that the convergence rate depends on the source of stochasticity in the problem: stochastic delivery locations converge faster than stochastic travel times according to the numerical test. The sample average approximation and the sequential sampling procedure show a similar performance. The performance of the fixed sample size sampling is better compared to the other two approaches. The results suggest that the stochastic information is valuable in real-life and can dramatically improve the performance of a taxi sharing system, compared to deterministic solutions. 相似文献
63.
A cooperative waiting strategy based on elliptical areas for the Dynamic Pickup and Delivery Problem with Time Windows
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The purpose of this paper to present a cooperative scheduling algorithm for solving the Dynamic Pickup and Delivery Problem with Time Windows (DPDPTW). The idea behind cooperative waiting strategies is to calculate simultaneously the waiting times for all nodes in the solution. Classical non‐cooperative scheduling algorithms perform the scheduling for each route independently of the scheduling of the other routes. We present the Cooperative Scheduling Problem (CSP) based on the elliptical areas generated by vehicles waiting at their nodes. The CSP is solved by means of a genetic algorithm and is evaluated by using a set of benchmarks based on real‐life data found in the literature. Initially, two waiting strategies are presented: Wait‐Early‐Time scheduling and Balanced‐Departure scheduling. Extensive empirical simulations have been carried out by analyzing the degree of dynamism and the average waiting time, a new concept defined to take into account the gap between the time windows of pickup and delivery nodes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
64.
取送车系统是车站作业系统的子系统,其效率的高低直接关系到出发列车正点率、车辆周转时间等运输生产指标。基于系统优化理论与方法、组合数学、集合论以及生产实践经验,分析取送车系统的要素、结构、环境和特征,研究取送车问题的建模方法、模型解的构造方法、寻优算法和提高问题寻优效率的启发式方法,并通过算例对研究成果的适用性进行验证。主要研究内容和结论如下。 相似文献
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66.
中国西部地区46个贫困县妇女孕产期保健现况 总被引:6,自引:0,他引:6
目的 了解西部地区妇女保健现状 ,分析其影响因素 ,从而寻找适当的改进措施。方法 对 9个项目省、自治区和直辖市的 4 6个项目县 ,进行了横断面调查设计及分层多阶段随机抽样调查。结果 产前检查率平均在 86 %以上 ;产前检查地点主要以乡卫生院为主 (占 4 7.78% ) ;分娩地点 :住院分娩的占 4 8.5 0 % ,在家里的占 4 9.2 6 %。结论 进一步提高住院分娩率 ,提高乡级卫生人员的业务素质 ,加强妇女保健的宣传工作 ,将有助于改善西部贫困地区的妇女保健状况 相似文献
67.
基于卖方管理库存的配送决策优化模型与算法 总被引:4,自引:0,他引:4
为实现供应链一体化和卖方管理库存,建立了同时考虑供给方的配送费用和客户的库存费用的整体优化模型.为降低求解该模型的难度,初步确定送货车辆与客户的对应关系后,将该模型分为库存分配模型和带时间窗的旅行商问题的模型.采用较为成熟的算法即可分别求解这2个模型,然后再将2者合成为原问题的模型. 相似文献
68.
Media Commerce is now becoming a new trend which results from faster development of network bandwidth and high availability of multimedia technologies, how to protect media content from being used in a rightviolated way is one of most important issues to take into account. In this paper, a novel and efficient authorization and authentication Digital Rights Management (DRM) schema is proposed firstly for secure multimedia delivery, then based on the schema, a real-time digital signature algorithm built on Elliptic Curve Cryptography (ECC) is adopted for fast authentication and verification of licensing management, thus secure multimedia delivery via TCP/RTP can efficiently work with real-time transaction response and high Quality of Service (QoS) . Performance evaluations manifest the proposed schema is secure, available for real-time media stream authentication and authorization without much effected of QoS. The proposed schema is not only available for Client/Server media service but can be easily extended to P2P and broadcasting network for trusted rights management. 相似文献
69.
With increasing attention being paid to greenhouse gas (GHG) emissions, the transportation industry has become an important focus of approaches to reduce GHG emissions, especially carbon dioxide equivalent (CO2e) emissions. In this competitive industry, of course, any new emissions reduction technique must be economically attractive and contribute to good operational performance. In this paper, a continuous-variable feedback control algorithm called GEET (Greening via Energy and Emissions in Transportation) is developed; customer deliveries are assigned to a fleet of vehicles with the objective function of Just-in-Time (JIT) delivery and fuel performance metrics akin to the vehicle routing problem with soft time windows (VRPSTW). GEET simultaneously determines vehicle routing and sets cruising speeds that can be either fixed for the entire trip or varied dynamically based on anticipated performance. Dynamic models for controlling vehicle cruising speed and departure times are proposed, and the impact of cruising speed on JIT performance and fuel performance are evaluated. Allowing GEET to vary cruising speed is found to produce an average of 12.0–16.0% better performance in fuel cost, and −36.0% to +16.0% discrepancy in the overall transportation cost as compared to the Adaptive Large Neighborhood Search (ALNS) heuristic for a set of benchmark problems. GEET offers the advantage of extremely fast computational times, which is a substantial strength, especially in a dynamic transportation environment. 相似文献
70.