Research On Model And Algorithm Of Container Retrieval Operations In Terminal Yards-Based On Relocation Paths Optimization

In the post-financial crisis era,the sluggish economic recovery in global scope has affected the development of international shipping industry seriously and the negative influence is especially evident at container ports.However,the conversion of economic development model from a domestically-oriented one to an externally-oriented one in China has created the unprecedented complex situation,which involves challenges and development opportunities as well for domestic ports.The economic new normal,featured by medium low economic growth speed,makes the competition among ports fiercer;on the other hand,the in-depth advancing of “One Belt and One Road” strategy provides precious opportunities for ports' development.Container terminals reforming traditional operating models has become the preferred strategy for companies to cope with challenges and seize opportunities,and enhancing operation efficiency and strengthening core competence of yard are vital to exist and succeed for container ports.Aiming at improving container terminals' operational efficiency,this dissertation does some research on selecting locations for containers and optimizing the relocation paths during retrieval operations.Based on the existing research results,we put emphasis upon studying the retrieval operations in conditions where containers potential locations are restricted to one bay and multiple bays respectively,considering containers' different flow directions and attributes,synchronous operation of gantry crane scenes.The main work and innovations of the dissertation are summarized as follows:After field research and reference carding,the dissertation summarizes the characteristics of container retrieval operations in the single bay model.Because of the problem's NP-hard attribute,this dissertation puts forward several retrieval rules and builds a rule base according to terminal technology,parallelly using multiple rules to select suitable locations for obstructed containers,which is different from existing studies.The problem of multi-rules used in parallel is solved successfully: the time complexity of the algorithm increases at least one order,and balance the relationship between solving precision and CPU time.The numerical results show that our proposed algorithm is superior to KH,DH,CM,and LA algorithms under the same condition where the bay size of the yard is the same.The retrieval model for containers that could be relocated in another bay is different from the model mentioned above,with the potential locations of research object extending from single bay to multiple bays.The difficulty of this improvement is that we cannot only consider container locations scheduling,and the integrated scheduling of the containers and equipment must be taken into account.Furthermore,emptying stacks one by one when extracting the containers is not allowed,otherwise the center of gravity of the yard is unsteady,which is a potential safety risk.Hence,more retrieval rules must be refined.Different from previous studies,this dissertation also considers the speed and time difference of gantry cranes' operation between different bays and different stacks,and the differences are reflected in the model and algorithm.The numerical results show that all test data of our proposed algorithm are almost beyond LL,B&J and LL heuristic algorithms.In the container retrieval operation model with considering containers' different flow directions,the research content has changed from neglected container flow to taking the flow into consideration,and the research scene further improved from being theoretical to actual.The difficulty of the research is how to put every added attributes into the theoretical model.Based on the theoretical model and in combination with the practical operation situation of container terminals,the dissertation integrates each additional element into the model by setting the priorities,changing the initial storage states and refining containers' retrieval rules.The comparison between the results of the examples including specific information and the random generated examples shows that the relocation number of the model considering container flow is lower than the first two models.In the container retrieval operation model with considering containers' different attributes,the research content further changes from considering different flow directions to different attributes,the research scope ranges from single attribute to multi-attributes.The factors taken into account are more comprehensive and closer to the container terminal operation scene,but it makes the study more difficult.Hence,it is necessary to judge the importance of different attributes,and make better combination of attributes of different flows,so as to make the theoretical research more applicable to management practice.In the container retrieval operation model of considering synchronous working of gantry cranes,the research content extends from considering one single piece of equipment to multiple equipment,and conducts an in-depth study on the operation of single equipment,the independent operation of multiple equipment and the cooperative operation of multiple equipment.Numerical experiment results show that the effect of the collaborative operation between different gantry cranes is best and the container relocation number is least.Therefore,delimiting the joint operation areas between different gantry cranes makes the operation efficiency higher and the resources more reasonably utilized.The dissertation,studying model and algorithm of container retrieval operations in terminal yards-based on relocation paths optimization,is consistent with the frontier to logistics development,and satisfies the needs of developing technology and solving management problems in Chinese coastal container ports,so this research has meritorious theoretical perceptiveness and considerable economic practicability.