Optimization And Simulation In Qiongzhou Straits Logistics System

Qiongzhou Straits is the golden waterway between Hainan and other inland cities in China for logistics exchange.It also plays an important role as the main pass of Hainan for importing goods.But the logistic efficiency of the straits is reduced significantly by problems such as ro-ro ship sailing without cars loaded,car congestion outside the port gate,excessive travelling time across the straits,etc.Yet the primary reason of these problems are still hidden.To change the current situation of low service level and low economic efficiency,the Qiongzhou Straits logistics system is analysed and divided into the Ro-ro transport subsystem and the inland road transport subsystem.Using computer simulation as an assisting method,the current problems are solved by optimizing the port scheduling and establishing logistics distribution center.Accroding to the guidelines of simulation analysis,the Ro-ro transport subsystem and the inland road transport subsystem are analyized by defining their borders,processes and constituents,which structs the logic of the system.Related data from the ports in these two submodels is processed using classification statistics and deviation analysis,which provides simulation analysis with accurate input.HPN(Hybrid Petri Net)models are built to describe the processes of these two submodels based on their previous analysis,and use non-stationary Poisson distribution to simulate car arrival pattern,which constructs standard abstract models to describe the system.The Ro-ro transport scheduling optimization simulation model and the distribution center location selection simulation model are build by transferring the HPN models into simulation models base on Simio software.Both simulation models are verified by testing their output and animation.In the end,a dynamic location selection model is built for finding the best locations of distribution centers to minimize the logistics cost and two simulation experiments are cast to optimize ro-ro port scheduling strategy and to locate the distribution centers.The result of the port scheduling optimization experiment shows that the imbalance of the ships' quantity and the waiting for berth to unload are the main causes of the low service level.After optimization,the max length of waiting queue outside the port gate is reduced by up to 80% and the travelling time is reduced by up to 24% comparing to the current scheduling strategy.It also proves that the income of ship companies between Guangdong and Hainan can be balanced when the proportion of ship departures is 5:6.The result of the location selection experiment shows that the best locations of distribution center to minimize variable cost,cost of unit goods and payback period of investment are Maoming,Guangzhou and Yangjiang separately.The variable cost,cost of unit goods and number of entry port cars can be reduced by 6.25%,25.27% and 42.22% after distribution center established,which proves that establishing distribution centers can decrease the stress of ro-ro transport system and reduce logistics cost effectively.