Abstract: For the status of regional logistics system layout optimizationand the current limitations of the method, considered its main factors and related model, this paper studied the regional logistics system layout characteristics, and comprehensive analysis and evaluation have been done on the factors which may exert impact on service range division with AHP and comprehensive fuzzy evaluation. Those factors are concluded as generalized costs and port attractive factors, representing the comprehensive attraction of logistics node to the service area, establishing logistics node dynamic service range division model based on the gravitational model, then weighted voronoi diagram and the discrete generation algorithm are introduced. At the same time, considering the regional industrial distribution and freight demand distribution, we can calculate the actual operation demand of each logistics node. Then, we adopts evolutional algorithmto realize the layout optimizationof complex logistics system.Practical examples show that the proposed method is able to meet the requirements of the logistics planning and operation, also can offer the reference to the decision making of administrative departments in the logistics system number, scale, location, layout and operation rationalization.

Keywords: regional logistics system, layoutoptimization, weighted voronoi diagram, gravitational model, evolutional algorithm

1. Introduction

Along with the world economic integration and the development of China's foreign trade, the function of modern logistics system is increasing day by day. Logistics has become the source power of development of the regional economy^[1]. Planning the construction and operating of regional logistics system scientifically and systematically, which is not only related to the development of logistics and correlative industry, but also related to the unitary advance of area economy. The reasonable service range and operating coordination optimization of regional logistics node is an important matter in regional logistics plan, the service range of logistics node reacts and decides the development direction and scale of logistics node, the size of service range of logistics node and the number of logistics demand is not only related to the plan and construction of logistics, but also the harmonious development of the unitary area. 

At present, the study about logistics system optimization is not enough, and still lack of the quantitative method to calculate in practical problem, especially in the aspect of attracting demand point in the service range of logistics system and their interaction, it is a rude division with limit, which limit the depth and veracity of dimensional service range in some extent. Recent years, although the introduction of new subject, crossed subject and geographical revolution have an important influence on the study of service range of logistics node, such as, in the coordinationstation of logistics node with different function, the expert from Japan do a deeper study, when considering the setting of logistics node, the unitary consume area should be taken as the study object to compare the economic character between direct send and sent by logistics node ^[2]. Dai He talks about the service range of the logistics node with second level ^[3]. Zhang Dezhi studies the layout optimization of multi-level logistics park system ^[4]. But these models are helpless to accurately divide the dynamic service range of the logistics system in complicated area formed by multi logistics nodes. And also, the problem of dimensional service division of logistics node is a problem about multi factor value, But the present method for dimensional service division is from one respect without general consideration, so, which is not able to respect the aspiration of logistics node to service area scientifically, and the multi-level logistics node system layout optimization based on these isn’t clear and correct enough ^[5].