考虑集结时间的中欧班列直达与中转运输优化模型

Optimization Model for Direct and Transit Transportation of China-Europe Railway Express Considering Assembly Time

为缩短中欧班列全程运行时间,促进其高质量发展,构造考虑集结时间的中欧班列直达与中转运输优化模型。根据实际中的直达、中转2种中欧班列运输组织方式,提出用虚拟弧表示集结过程的广义服务网络构建方法;基于广义服务网络,考虑不同中转方案对各中转节点集结时间的影响,得到以各货源点发出中欧班列集装箱总耗时最短为目标,以网络流量守恒和集结弧、运输弧能力为约束条件的优化模型;针对模型因决策变量出现在分母的复杂非线性项而难以求解的问题,提出先插入切线近似逼近曲线、再构造等效代换不等式组的“两步走”线性化处理方法;通过小型模拟算例验证模型的有效性。结果表明:对于4个运量相对较小的货源点,与全部直接开行直达中欧班列的全直达方案相比,优化方案中各点始发的中欧班列集装箱总耗时减少42.8 TEU·d,因而该优化模型是可行且有效的。

In order to shorten the whole operation time of China-Europe Railway Express and promote its high-quality development, the optimization model for direct and transit transportation of China-Europe Railway Express considering the assembly time is constructed. A construction method for the generalized service network using virtual arcs to represent the gathering process is proposed according to the two actual modes of China-Europe Railway Express transportation organization. Based on the generalized service network and considering the influences of different transit schemes on the assembly time of each node, an optimization model is proposed to minimize the total time of China-Europe Railway Express containers from each source point with the constraints of network flow conservation, the capacity of aggregation arcs and the transportation arcs. In order to address the problem that the model is difficult to solve due to the complex non-linear terms in the denominator of the decision variables, a“two-step”linearization method is proposed, in which a tangent line is first inserted to approximate the curve, and then a set of equivalent substitution inequalities is constructed. The validity of the model is verified through a small-scale simulation example. The results show that the optimization model is feasible and effective as the total time for China-Europe Railway Express containers originating from each point is reduced by 42. 8 TEU · d compared with the all-direct scheme for the four relatively small volume points.