Fault Simulation And Invulnerability Evaluation Of Urban Fresh Agricultural Products Distribution Network

In recent years,with the rapid development of e-commerce in china,especially online shopping,the demand of city distribution service increases rapidly,due to the dense of urban residents and in-trips vehicles,traffic network fault is more common,such as urban traffic accident,road maintenance,the peak congestion and so on,coupled with the restriction and control on the trip of freight vehicles in most cities,greatly increased the difficulty of the city logistics distribution business.Compared with other commodities,fresh agricultural products have the characteristics of easily decomposes and deterioration,its value is influenced by the freshness,and have higher requirements for the delivery time and delivery mode.In the distribution process,the freshness and distribution cost of fresh agricultural products are more vulnerable to the urban traffic faults.Therefore,it is important significance to simulate the fault which is happen in city fresh agricultural products distribution network and its propagation mechanism,and use the relevant theory to evaluate the survivability of the network and analysis the fault impact on the distribution of fresh agricultural products.Firstly,the graph theory and the relevant theory of complex network is described in this paper,establishing urban fresh agricultural product distribution network model,and analyzing the structural properties of the network.The study shows that network has small world property and good connectivity,and a few nodes and edges play an important role in maintaining network connectivity.Node degree distribution of the network is non-uniform,the distribution span of the shortest path length is relatively large,the network contains complex information,which provide the possibility to improve and optimize the topology of network.Then,according to the characteristics of urban distribution network,the network fault is divided into two states:"fault state" and "failure state".When nodes or edges in the "fault state",the network topology is not destroyed,the time of through the fault point will increase,whice result in the increase of distribution costs and affect the efficiency of distribution,based on this research the network survivability under the nodes and edges in the "fault state".When the nodes or edges in the "failure state",the network topology will be destroyed,due to the impact of cascading failure phenomena,the load which is on failure node and edge will redistribute and cause other nodes and edges cascading failure,and the failure of nodes and edges lead to rapidly increase in the delivery time and distance,the distribution costs rose sharply and seriously affect the distribution efficiency,based on this research the network survivability under the nodes and edges in the "failure state".The result shows that:under the same conditions,the targeted attacks and multiple faults will brings more serious injuries,compared with the node fault,the network show better invulnerability under edge fault,due to the effect of cascading failure,the failure of nodes and edges will bring greater damage to the network,and enhance the tolerance coefficient of the network can prevent the occurrence of cascading failures.Finally,the failure of multiple key nodes will seriously affect the distribution efficiency of fresh agricultural products by analyzing the effect of network fault on the distribution of fresh agricultural products.Therefore,when make relevant strategies to avoid the network fault,it should be pay more cost and energy on the network core node,make multiple fault emergency response measures,and put more funds to build network,enhance the capacity of the network to make sure efficient delivery of fresh agricultural products.