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Detailed schedule
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Show all the abstracts
Show all the abstracts
Thursday 11:00:00 Timetabling in education and sport Room 126 - Chair: G. Vanden Berghe
Thursday 11:00:00 Transportation management Room 130 - Chair: F. Semet
Thursday 11:00:00 Networks Room 138 - Chair: B. Fortz
Thursday 11:00:00 Nonconvex optimization 1 Room 035 - Chair: F. Bach
Thursday 14:00:00 Constraint programming models 1 Room 126 - Chair: Y. Deville
Thursday 14:00:00 Vehicle routing Room 130 - Chair: S. Limbourg
Thursday 14:00:00 Combinatorial optimization and IP applications Room 138 - Chair: Q. Louveaux
Thursday 14:00:00 Nonconvex Optimization 2 Room 035 - Chair: R. Sepulchre
Thursday 16:10:00 Constraint programming models 2 Room 126 - Chair: P. Schaus
Thursday 16:10:00 Performance modeling Room 130 - Chair: G. Janssens
Thursday 16:10:00 Scheduling Room 138 - Chair: K. Sorensen
Thursday 16:10:00 Planning under uncertainty Room 035 - Chair: R. Leus
Friday 09:00:00 Metaheuristics Room 126 - Chair: J. Teghem
Friday 09:25:00 Production and distribution (9:25) Room 130 - Chair: Y. Arda
Friday 09:00:00 Multiple criteria Room 138 - Chair: R. Bisdorff
Friday 09:25:00 Stochastic models (9:25) Room 035 - Chair: L. Esch
Friday 11:00:00 Constraint programming and Supply Chain Management Room 126 - Chair: Y. Deville
- A CLP engine for product configuration
Dario Campagna (University of Perugia)
- Just-In-Time Scheduling with Constraint Programming
Jean-noël Monette (Université catholique de Louvain) Co-authors: Yves Deville, Pascal Van Hentenryck
- Tank allocation for liquid bulk vessels using a hybrid constraint programming approach
Rowan Van Schaeren (Antwerp Maritime Academy) Abstract: The chemical industry is characterized by a very strong competitive environment. This leads to an increased pressure on providing consistent quality, fast delivery and cost-cuttings. Chemicals are transported all over the world in special, dedicated vessels. These chemical tankers form an important aspect of this liquid bulk chemicals trade and the number of chemical tankers available on the market increases steadily. Chemical tankers distinguish themselves from other tankers in the large number of separate cargo tanks available to load cargo. Some chemical tankers have over 30 individual tanks. This allows for many different cargoes to be transported simultaneously, but requires that each cargo tank has its own pump and piping system to connect with the shore in order to prevent mixing or contaminating individual cargoes. This also has an important impact on the planning of cargoes on board of these chemical tankers as cargo interactions can result in dangerous situations. Almost all chemical products can be considered dangerous one way or the other (being labeled as e.g. corrosive, marine pollutant, toxic ...). These products must therefore be stored in accordance with stringent regulations.
Concerning stowage the most important criterion is segregation. Segregation is not only important between the different products themselves (certain products like e.g. caustic soda and sulfuric acid cannot be stowed in adjacent tanks) but also with respect to the tank coatings that protect the tanks from products stored in them. In addition to this, the vessel's stability constraints complicate the capacity planning even further. Because of the computational complexity of mathematically optimizing the problem, loading plans are generally generated manually by the vessel planners and checked by a stability program afterward. Because of the multitude of constraints, regulations and ``good practices'', it is very difficult to generate high quality loading plans manually. Optimization methods capable of handling these side constraints and generating high quality solutions can therefore greatly support vessel planners and free up time for handling non-standard scheduling issues.
Academic literature on the tank allocation problem (TAP) or operational planning is limited. Most of the conducted research considers both the load planning and vessel routing of chemical tankers. However, only a few deal with segregation and stability constraints simultaneously in their load planning, which are essential in real-life applications. The literature review illustrates the difficulties of simultaneously addressing both planning and routing aspects for loading chemical vessels even if no or only simplified ship stability constraints are taken into account. As this research aims at modeling the stability of chemical tankers in full detail, we start by focusing on the load planning part of the problem. Although the loading aspect of chemical vessels can be addressed successfully by mixed integer programming, constraint programming (CP) looks more promising for developing an integrated model in the future, in which both the scheduling of several ports aspect and the load planning of cargo aspect are combined.
In the proposed model, CP is used for making the allocations of cargo to the tanks and LP is dynamically used as a final constraint checker for the ship stability at the potential solution nodes of the search tree. More precisely, at a potential solution node of the CP search tree, every tank is empty or is allocated to a cargo ensuring that there is enough volume for each cargo while satisfying segregation constraints. The LP is then called as a subroutine to check and optimize the stability constraints deciding how many tons of the cargo will be allocated to each tank by considering the cargo allocation as given. If the stability requirements cannot be satisfied by the LP the node is simply discarded. This simple hybridization between CP (Master) and LP (slave) is used in a Branch and Bound scheme to maximize the unused free space of the tanks.
Computational results with Comet show that this hybrid CP-LP approach is an interesting path for solving the operational planning problem of chemical tankers (load planning and scheduling). Computational times prove to be operationally acceptable with the proposed model.
Our current research focuses on finding a good CP search algorithm, as this is critical concerning computation times. Integrating the ship routing and scheduling into the operational planning will be the topic of future research.
- Effective Estimation-based Stochastic Local Search Algorithms for Stochastic Routing Problems
Thomas Stützle (Université Libre de Bruxelles (ULB) ) Co-authors: Prasanna Balaprakash, Mauro Birattari, Marco Dorigo
Friday 11:00:00 OR in health management Room 130 - Chair: P. De Causmaecker
Friday 11:00:00 Rankings and importance indices Room 138 - Chair: JL. Marichal
Friday 11:00:00 Queueing Room 035 - Chair: S. Wittevrongel
Friday 15:10:00 Optimization software Room 126 - Chair: E. Loute
Friday 15:10:00 Integrated operations planning Room 130 - Chair: B. Raa
Friday 15:10:00 Cycles in graphs Room 138 - Chair: F. Spieksma
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