| 1. |
- Andersson Granberg, Tobias, et al.
(författare)
-
Decision support tools for ambulance dispatch and relocation
- 2007
-
Ingår i: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 58, s. 195-201
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the development of decision support tools for dynamic ambulance relocation and automatic ambulance dispatching is described. The ambulance dispatch problem is to choose which ambulance to send to a patient. The dynamic ambulance relocation problem occurs in the operational control of ambulances. The objective is to find new locations for some of the ambulances, to increase the preparedness in the area of responsibility. Preparedness is a way of evaluating the ability to serve potential patients with ambulances now and in the future. Computational tests using a simulation model show that the tools are beneficial in reducing the waiting periods for the patients.
|
|
| 2. |
- Gunnarsson (Lidestam), Helene, et al.
(författare)
-
A combined terminal location and ship routing problem
- 2006
-
Ingår i: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 57:8, s. 928-938
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider a combined terminal location and ship routing problem at Södra Cell AB. The purpose is to supply the customers' annual demand for pulp products while minimizing the distribution costs. Customers are supplied with various pulp products from pulp mills in Scandinavia by ships, trains, or lorries. The ship routes go from the pulp mills to terminals in Europe. From each terminal, the products are transported to customers by lorry, train, or barge. Some customers can be supplied directly from the pulp mills by trains or lorries. We have developed a mathematical model to select which terminals to use and, at the same time, determine the shipping routes. The mixed integer programming model was solved directly using a commercial solver. When the number of routes generated is large, the time required to obtain an optimal solution is too long. Hence, we have developed heuristics in order to obtain an acceptable solution in reasonable time. In addition to the basic case, five different scenarios were tested. Our heuristics provide solutions that are within 0.12% of the optimal ones.
|
|
| 3. |
- Nilsson, Andreas, et al.
(författare)
-
A simple improvement on Silver's heuristic for the joint replenishment problem
- 2008
-
Ingår i: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 59:10, s. 1415-1421
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we revisit the well-known joint replenishment problem. There is a family of items with a major fixed cost associated with any replenishment of the family and a minor, (item-dependent) setup cost for each item that is included in the replenishment. In contrast with optimization methods and sophisticated (iterative) heuristics that have been presented in the literature, we present a simple (including ease of understanding) improvement routine to be used in conjunction with the original, simple approach advocated by one of the authors 30 years ago. Tests on 48,000 examples reveal that the improvement routine does, indeed, substantially improve performance and with relatively little extra computational effort. Thus, it should be of particular interest to practitioners and for teaching materials.
|
|
| 4. |
- Tansini, Libertad, 1973, et al.
(författare)
-
New measures of proximity for the assignment algorithms in the MDVRPTW
- 2006
-
Ingår i: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 57:3, s. 241-249
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes new proximity measures for assignment algorithms for the Multi-Depot Vehicle Routing Problem with Time Windows (MDVRPTW). Given the intrinsic difficulty of this problem class, two-step approximation methods of the type 'cluster first, route second' seem to be the most promising for practical size problems. The focus is on the clustering phase, the assignment of customers to depots. Our approach is to extend the existing metrics with time windows. New measures that include time windows and distances are added to two assignment heuristics, that previously only used distance to evaluate proximity between customers and depots. A computational study of their performance is presented, which shows that the inclusion of time windows in the measures of proximity gives better results, in terms of routing, than only using the distance.
|
|
