Study On The Express Shipment Product Design Problem Based On Reliability

With the rapid development of the markets and economy of China, the express shipment demands significantly increase in recent years and put forward the higher requirements for the quality of transportation services. As one of the most important factors, the reliability is becoming the core value of the shipment product and affects the survival and further development of the express company. New challenges are presented in the express shipment product design problem. Study on the reliability evaluation and reliability-based design is significance and necessary to improve the service level and make full use of shipment system resources. On this basis, this paper presents a general survey of existing literatures on the theory of service network design and reliability of transportation system. The main contents of the paper can be concluded as follows:1.A theoretical framework for the express shipment product design is constructed from the angle of the service network design theory. By analyzing the basic characteristics of this kind of design problem, this paper presents the core contents that include the construction of service network, the design of service chain and the assignment of freight flow. Moreover, the details of the theoretical framework are explained and optimization model is proposed to describe the complex relations between resources, demands and services in the time-space unifying network.2.The methodology of constructing services network based on multi-modal transportation is investigated. Through the analysis of different services connections, this paper proposes a concept of service chain to describe the goods transport process and examines the relationship between time-space characteristics of service network and effectiveness of express shipment product. Then the evaluation method of reliability index is presented by using the technology of QoS on computer network. Moreover, the reliability of express shipment product is measured from the angle of capacity reliability and travel time reliability of service network.3.For the decrease of reliability related to changes in customer demands, the capacity reliability of service network is proposed by defining the static service network capacity. Considering the spatial distribution of multi-modal transportation services, the method of capacity computing about the general service network and "hub-spoke" structure network is discussed. The paper brings forward the capacity reliability index based on the random variable which describes the changes of the customer demands and analyzes the redundancies of the network from the two layers of OD area and system as a whole.4.The time reliability evaluation problem on the service network is investigated. Considering the relationship among the multi-modal transportation services, the service chain is defined to describe the freight transportation in this time-space unified network. On this basis, the time-limit fulfill rate and adaptability of service chain are presented to evaluate the time reliability of transport process. Also these indexes are computed from two layers of OD area and system as a whole.5.Based on the service network design model, the design problem on the express shipment product with capacity reliability and time reliability constraints is evaluated. According to the classification of the decision variables and stochastic features of reliability constrains, a stochastic chance-constrained programming modal is presented. Given the confidence level, the stochastic constrains of the capacity reliability and time reliability are converted into deterministic constrains and this kind of probability model is also turned into deterministic model. Then the paper designs a hierarchy and combination algorithm to solve this kind of product design problem. The data and examples from China Railway Express Company indicate that the model is feasible and the algorithm is valid.