| 1. |
- Brännlund, Ulf, et al.
(författare)
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Railway Timetabling Using Lagrangian Relaxation
- 1998
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Ingår i: Transportation Science. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0041-1655 .- 1526-5447. ; 32:4, s. 358-369
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel optimization approach for the timetabling problem of a railway company, i.e., scheduling of a set of trains to obtain a profit maximizing timetable, while not violating track capacity constraints. The scheduling decisions are based on estimates of the value of running different types of service at specified times. We model the problem as a very large integer programming problem. The model is flexible in that if allows for general cost functions. We have used a Lagrangian relaxation solution approach, in which the track capacity constraints are relaxed and assigned prices, so that the problem separates into one dynamic program for each physical train. The number of dual variables is very large. However, it turns out that only a small fraction of these are nonzero, wh ich one may take advantage of in the dual updating schemes. The approach has been, tested on a realistic example suggested by the Swedish National Railway Administration. This example contains 18 passenger trains and 8 freight trains to be scheduled during a day on a stretch of single track, consisting of 17 stations. The computation times are rather modest and the obtained timetables are within a few percent of optimality.
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| 2. |
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| 3. |
- Hamfelt, Andreas, et al.
(författare)
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Inductive Logic Programming with Well-Modedness Constraints
- 1999
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Ingår i: Proceedings of the 8th International Workshop on Functional and Logic Programming. - : Centre National de la Recherche Scientifique, Institut National Polytechnique de Grenoble, Université Joseph Fourier, Laboratoire Leibniz. ; , s. 220-231
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Konferensbidrag (refereegranskat)
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| 4. |
- Hamfelt, Andreas, et al.
(författare)
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Inductive synthesis of logic programs by composition of combinatory program schemes
- 1999
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Ingår i: LOGIC-BASED PROGRAM SYNTHESIS AND TRANSFORMATION. - : SPRINGER-VERLAG BERLIN. ; , s. 143-158
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Konferensbidrag (refereegranskat)abstract
- Based on a variable-free combinatory form of definite clause logic programs we outline a methodology and supporting program environment COMBINDUCE for inducing well-moded logic programs from examples. The combinators comprise fold combinators for recursio
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| 5. |
- Hamfelt, Andreas, et al.
(författare)
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Towards a logic programming methodology based on higher-order predicates
- 1997
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Ingår i: NEW GENERATION COMPUTING. - : SPRINGER VERLAG. - 0288-3635. ; 15:4, s. 421-447
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines a logic programming methodology which applies standardized logic program recursion forms afforded by a system of general purpose recursion schemes. The recursion schemes are conceived of as quasi higher-order predicates which accept pr
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| 6. |
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| 7. |
- Lindeberg, Staffan, et al.
(författare)
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Age relations of cardiovascular risk factors in a traditional Melanesian society: the Kitava Study
- 1997
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Ingår i: American Journal of Clinical Nutrition. - 1938-3207. ; 66:4, s. 845-852
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Tidskriftsartikel (refereegranskat)abstract
- This study examined cross-sectional age relations of blood pressure, anthropometric indexes, serum lipids, and hemostatic variables in 203 subsistence horticulturists aged 20-86 y in Kitava, Trobriand Islands, Papua New Guinea. The population is characterized by extreme leanness (despite food abundance), low blood pressure, low plasma plasminogen activator inhibitor 1 activity, and rarity of cardiovascular disease. Tubers, fruit, fish, and coconut are dietary staples whereas dairy products, refined fat and sugar, cereals, and alcohol are absent and salt intake is low. Although diastolic blood pressure was not associated with age in Kitavans, systolic blood pressure increased linearly after 50 y of age in both sexes. Body mass index decreased with age in both sexes. Serum total cholesterol, triacylglycerol, low-density-lipoprotein cholesterol, and apolipoprotein B increased in males between 20 and 50 y of age, whereas high-density-lipoprotein cholesterol and apolipoprotein A-I decreased. There were no significant differences in these indexes with age in the few females studied. A slight linear age-related increase of lipoprotein(a) was present in males. Plasma fibrinogen, factor VII clotting activity, factor VIII clotting activity, and von Willebrand factor antigen increased with age in both sexes but plasminogen activator inhibitor 1 activity did not. The modest or absent relations between the indexes measured and age are apparently important explanations of the virtual nonexistence of stroke and ischemic heart disease in Kitava.
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| 8. |
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| 9. |
- Nilsson, Jorgen Fischer, et al.
(författare)
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Constructing Logic Programs with Higher Order Predicates
- 1995
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Ingår i: Proceedings of GULP-PRODE'95, the Joint Conference on Declarative Programming. - : Universita' Degli Studi di Salerno, Salerno. ; , s. 307-312
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Konferensbidrag (refereegranskat)
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| 10. |
- Schelén, Olov, et al.
(författare)
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Performance of QoS agents for provisioning network resources
- 1999
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Ingår i: 1999 Seventh International Workshop on Quality of Service. - Piscataway, NJ : IEEE Communications Society. - 0780356713 ; , s. 17-26
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Konferensbidrag (refereegranskat)abstract
- We have designed an agent-based architecture for quantitative service provisioning in differentiated services capable networks. For each link-state routing domain in the network there is a topology-aware QoS agent (also known as a bandwidth broker) responsible for admission control. The architecture provides resource reservations for aggregated virtual leased lines between network domains. In this paper, we present performance measurements for resource provisioning in a prototype QoS agent. This includes an evaluation of two data structures for advance reservations and accompanying algorithms. We also compare the cost for on-demand route computations with pre-computation of routes. The objective in this paper is to evaluate the performance of end-to-end admission control within a single link-state routing domain. In a domain with 15 routers, 28 transition networks and 64 stub networks, our prototype performs approximately 25000 end-to-end admission decisions per second. The results show that an ordinary PC can be used for running a QoS agent that performs path-sensitive admission control and maintains per link resource reservations in a link-state routing domain.
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