Worldwide Marine Transport Network:from Perspective Of Community Structure And Multi-layer Network

The marine transport is the primary means of international cargo transport. We study the underlying characteristics of the world marine transport networks (WMTN) with the help of complex network theory. This thesis first introduced the basic concepts and state of the art of complex network research. Next the topological quantities of the WMTN were calculated and the degree distribution of the WMTN was found of the nature of power-law which is closely associated with the forming of the WMTN. In addition, due to the loop nature of the WMTN we proposed a new concept which is line saturation to study the WMTN.The community structure is important for networks. Based on the latest algorithm of community detection the WMTN can be divided into seven communities. As the majority of ports of the same community belongs to the same geographical area, the community structure of the WMTN has a strong locality. The Multi-Dimensional Scaling (MDS) is widely used in visualization. We plotted the MDS graph of the WMTN by combining the diffusion distance, and it turns out the ports of the same community tend to gather together in the MDS graph, with which our point of view has been verified.The multi-layer network is an emerging method to study networks. We studied the relation of different marine companies by the method of multi-layer networks being aggregated. The topological quantities of the WMTN change smoothly versus the number of companies aggregated, and don’t saturate. This indicates that different companies have very few overlapping lines and each have its unique operating areas and lines, except for some busy lines which may consist of shared ports. We determined the sequence of marine companies being aggregated by the J-S distance, and aggregated the marine companies orderly. Simultaneously, we calculated the relative entropy which decreases with the number of merged companies. This finding implies that the redundancy rate of marine lines is low, which is consistent with the result by using the multi-layer network.This thesis studied the community structure and multi-layer networks structure of WMTN. These results has great guidance for the shipping plan and course scheduling, moreover it has theoretical significance to know and understand the WMTN structure and the dynamic evolution process.