208 research outputs found
Liner ship fleet planning with uncertain container shipment demand
Ph.DDOCTOR OF PHILOSOPH
Simultaneous Planning of Liner Ship Speed Optimization, Fleet Deployment, Scheduling and Cargo Allocation with Container Transshipment
Due to a substantial growth in the world waterborne trade volumes and drastic
changes in the global climate accounted for CO2 emissions, the shipping
companies need to escalate their operational and energy efficiency. Therefore,
a multi-objective mixed-integer non-linear programming (MINLP) model is
proposed in this study to simultaneously determine the optimal service
schedule, number of vessels in a fleet serving each route, vessel speed between
two ports of call, and flow of cargo considering transshipment operations for
each pair of origin-destination. This MINLP model presents a trade-off between
economic and environmental aspects considering total shipping time and overall
shipping cost as the two conflicting objectives. The shipping cost comprises of
CO2 emission, fuel consumption and several operational costs where fuel
consumption is determined using speed and load. Two efficient evolutionary
algorithms: Nondominated Sorting Genetic Algorithm II (NSGA-II) and Online
Clustering-based Evolutionary Algorithm (OCEA) are applied to attain the
near-optimal solution of the proposed problem. Furthermore, six problem
instances of different sizes are solved using these algorithms to validate the
proposed model.Comment: 28 pages, 10 figure
Efficiency and equity of speed limits in transportation networks
This paper examines the impact of speed limits on network efficiency, in terms of total travel time of all road users, and equity among road users from different origin-destination (OD) pairs, in terms of the change of travel time after imposing a speed limit scheme. We find that after imposing a speed limit scheme, the total travel time of all road users may decrease or increase; road users of some OD pairs may experience longer travel time, while other OD pairs may have shorter travel time. In view of the importance of speed limits on network efficiency and equity, we subsequently develop a bi-level programming model for designing the optimal speed limit scheme that maximizes the network efficiency while considering the equity issue. A global optimization approach that is suitable for bilevel programming models with finite discrete upper-level decision variables is proposed. Moreover, a conic quadratic mixed-integer linear programming approach is developed to solve relaxed models of the bi-level formulation of speed limit design. Two numerical examples are carried out
Risk management in liner ship fleet deployment: a joint chance constrained programming model
This paper provides a tangible methodology to deal with the liner ship fleet deployment problem aiming at minimizing the total cost while maintaining a service level under uncertain container demand. The problem is first formulated as a joint chance constrained programming model, and the sample average approximation method and mixed-integer programming are used to deal with it. Finally, a numerical example of a liner shipping network is carried out to verify the applicability of the proposed model and solution algorithm. It is found that the service level has significant effect on the total cost
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