| 1. |
- Karlsson, Emil, et al.
(författare)
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Explicit modelling of multiple intervals in a constraint generation procedure for multiprocessor scheduling
- 2017
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Ingår i: Operations Research Proceedings 2017. - Cham : Springer. - 9783319899190 - 9783319899206 ; , s. 567-572
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Konferensbidrag (refereegranskat)abstract
- Multiprocessor scheduling is a well studied NP-hard optimisation problem that occurs in variety of forms. The focus of this paper is explicit modelling of multiple task intervals. This work extends a constraint generation procedure previously developed for an avionics scheduling context. We here address a relaxation of the original problem and this relaxation can be considered as multiprocessor scheduling with precedence relations and multiple intervals.The explicit modelling of multiple intervals strengthens the formulation used in the constraint generation procedure and we illustrate the computational effects on an industrial relevant avionics scheduling problem.
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| 2. |
- Morén, Björn, 1987-, et al.
(författare)
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Preventing Hot Spots in High Dose-Rate Brachytherapy
- 2018
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Ingår i: Operations Research Proceedings 2017. - Cham : Springer International Publishing. - 9783319899190 - 9783319899206 ; , s. 369-375
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Konferensbidrag (refereegranskat)abstract
- High dose-rate brachytherapy is a method of radiation cancer treatment, where the radiation source is placed inside the body. The recommended way to evaluate dose plans is based on dosimetric indices which are aggregate measures of the received dose. Insufficient spatial distribution of the dose may however result in hot spots, which are contiguous volumes in the tumour that receive a dose that is much too high. We use mathematical optimization to adjust a dose plan that is acceptable with respect to dosimetric indices to also take spatial distribution of the dose into account. This results in large-scale nonlinear mixed-binary models that are solved using nonlinear approximations. We show that there are substantial degrees of freedom in the dose planning even though the levels of dosimetric indices are maintained, and that it is possible to improve a dose plan with respect to its spatial properties.
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| 3. |
- Rönnberg, Elina, 1981-
(författare)
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Co-allocation of communication messages in an integrated modular avionic system
- 2017
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Ingår i: Operations Research Proceedings 2017.. - Cham : Springer. - 9783319899206 - 9783319899190 ; , s. 459-465
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Konferensbidrag (refereegranskat)abstract
- Pre-runtime scheduling of the kind of Integrated Modular Avionic (IMA) system addressed in this paper can be considered as multiprocessor scheduling with additional constraints on precedence relations between tasks and the concurrent scheduling of a communication network with discrete time slots for sending messages. This paper extends an existing constraint generation procedure for such IMA-systems to facilitate co-allocation of messages in the time slots. To send a communication message involves the execution of a set of tasks. Co-allocation of messages means that tasks of the same type that originate from these messages are merged and their total execution requirements are shortened. The reduction of the execution requirements induces capacity savings that can have a positive impact on the feasibility of the problem.
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