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Most solution methods for the vehicle routing problem with time windows (VRPTW) develop routes from the earliest feasible departure time. In practice, however, temporary traffic congestion make such solutions non-optimal with respect to minimizing the total duty time. Furthermore, the VRPTW does not account for driving hours regulations, which restrict the available travel time for truck drivers. To deal with these problems, we consider the vehicle departure time optimization (VDO) problem as a post-processing of a VRPTW. We propose an ILP formulation that minimizes the total duty time. The results of a case study indicate that duty time reductions of 15% can be achieved. Furthermore, computational experiments on VRPTW benchmarks indicate that ignoring traffic congestion or driving hours regulations leads to practically infeasible solutions. Therefore, new vehicle routing methods should be developed that account for these common restrictions. We propose an integrated approach based on classical insertion heuristics. 相似文献
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本文首次研究服务员具有多重休假规则的成批到达Mx/G/1排队系统的输出过程.应用更新过程理论、拉普拉斯-司梯阶变换和本文提出的直接概率分解分析法,讨论了从任意初始状态出发,系统在(0,t]时间内输出顾客的平均数,以及其渐近展开,得到一些重要结果. 相似文献
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Wojciech M. Kempa 《随机分析与应用》2013,31(1):26-43
A batch arrival queueing system with a single vacation between two successive busy periods and with exhaustive service is considered. The departure process h(t) is studied first on a single vacation cycle. The approach based on renewal theory is applied to obtain results in the general case. In particular, the explicit representation for the generating function of Laplace transform of the probability function of h(t) is derived. All formulae are written in terms of input parameters of the system and factors of a certain canonical factorization of Wiener–Hopf type. A numerical approach to results is discussed as well. 相似文献
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组合预测方法在大气环境评价中的应用 总被引:9,自引:0,他引:9
李振亮.组合预测方法在大气环境评价中的应用.数理统计与管理,1997,16(4),12~15.本文利用组合预测理论和方法,建立了一种大气环境质量评价的组合模型。实例分析表明,该组合评价模型具有利用各单一评价模型提供的信息和集中各单一模型的优点,是一种稳健和优化的环境质量评价模型。 相似文献
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本文给出了G/G/1排队系统的离去过程的有限维分布弱收敛到泊松过程的有限维分布的条件,特别给出了生灭排队系统及G/M/1排队系统的离去过程的有限维分布弱收敛到泊松过程的有限维分布的简单条件. 相似文献
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We consider the M/M
ij
/1 queue as a model of queues with changeover times, i.e., the service is exponential with parameter
ij
depending on the previous job type (i) and the current job type (j). It is shown that the departure process is renewal and Poisson iff
ij
= (constant). In this case, types of departures are dependent renewal processes. Crosscovariance and crosscorrelations are given. 相似文献
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本文首次研究服务员具有多重休假规则的成批到达M^x/G/l排队系统的输出过程.应用更新过程理论、拉普拉斯-司梯阶变换和本文提出的直接概率分解分析法,讨论了从任意初始状态出发,系统在(O,t)时间内输出顾客的平均数,以及其渐近展开,得到一些重要结果. 相似文献