A branch-first, cut-second approach for locomotive assignment
Management Science
Decomposition of a Combined Inventory and Time Constrained Ship Routing Problem
Transportation Science
Aggregation and Mixed Integer Rounding to Solve MIPs
Operations Research
Lifting two-integer knapsack inequalities
Mathematical Programming: Series A and B
A Branch-and-Price Method for a Liquefied Natural Gas Inventory Routing Problem
Transportation Science
Production Planning by Mixed Integer Programming
Production Planning by Mixed Integer Programming
Description of 2-integer continuous knapsack polyhedra
Discrete Optimization
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We consider a short sea fuel oil distribution problem occurring in the archipelago at Cape Verde. Here, an oil company is responsible for the routing and scheduling of ships between the islands such that the demand for various fuel oil products is satisfied during the planning horizon. Inventory management considerations are taken into account at the demand side but not at the supply side. The ports have restricted opening hours each day, so multiple time windows are considered. In contrast to the ships in many other studies within ship routing and scheduling, ships here spend considerable time in the ports compared to at sea. Hence, the time in port is modeled in detail by incorporating both a variable unloading time and a setup time for loading different products in the same ports. A mathematical model of the problem is presented and it includes a combined continuous and discrete time horizon because of the multiple time windows and a daily varying consumption rate of the various products in the different ports. We discuss several strategies to improve the proposed model, such as tightening bounds, using extended formulations, and including valid inequalities. The computational study shows that the real problem can be solved to optimality within reasonable time by the use of improved formulations based on a combination of such strategies.