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We present a multi-start local search heuristic for a typical ship scheduling problem. A large number of initial solutions are generated by an insertion heuristic with random elements. The best initial solutions are improved by a local search heuristic that is split into a quick and an extended version. The quick local search is used to improve a given(More)
The maritime oil tanker routing and scheduling problem is known to the literature since before 1950. In the presented problem, oil tankers transport crude oil from supply points to demand locations around the globe. The objective is to find ship routes, load sizes, as well as port arrival and departure times, in a way that minimizes transportation costs. We(More)
Cloud services with a multi-tiered architecture are often difficult to evaluate in terms of performance and dependability. The tiered architecture complicates the resource capacity decisions of the service provider, and makes it more demanding to maintain a good balance between capacity and quality of service. In this work we present an approximation of the(More)
The split pickup split delivery crude oil tanker routing and scheduling problem is a difficult combinatorial optimization problem, both theoretically and practically. However, because of the large expenses in crude oil shipping it is attractive to make use of optimization that exploits as many degrees of freedom as possible to save transportation cost. We(More)
This paper studies different decomposition approaches for real-time optimization of process systems with a decentralized structure where the idea is to improve computational efficiency and transparency of a solution. The contribution lies in the application and assessment of the Dantzig-Wolfe method which allows us to efficiently decompose a real-time(More)