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| 2. |
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| 3. |
- Hellstrand, Johan, et al.
(författare)
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A characterization of the uncapacitated network design polytope
- 1992
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Ingår i: Operations Research Letters. - 0167-6377 .- 1872-7468. ; 12:3, s. 159-163
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Tidskriftsartikel (refereegranskat)abstract
- The uncapacitated network design problem is considered. We show that the feasible polytope of the continuous relaxation of this problem has the property that any path along the edges of the convex hull of its integer points is also a path along the edges of the polytope itself. This property may be of computational interest since it implies the possibility of solving the uncapacitated network design problem by a pivoting scheme. © 1992.
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| 4. |
- Jörnsten, Kurt O., et al.
(författare)
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An entropy model with variable target
- 1990
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Ingår i: Environment and planning A. - : SAGE Publications. - 0308-518X .- 1472-3409. ; 22:4, s. 493-506
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an entropy model with variable target is presented, in which target values are assumed to belong to a specified convex set, so that multiple base-year information and forecasts of future trends can be handled without prior aggregation of such information into one fixed target.Three solution methods for such a model are presented -- one cutting-plane and two search methods -- all of which utilize the fact that entropy models with fixed targets can be solved efficiently. Some comments on potential applications and reasonable target-set specifications are made and numerical examples are presented
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| 5. |
- Larsson, Torbjörn, et al.
(författare)
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A Lagrangean heuristic for the capacitated concave minimum cost network flow problem
- 1994
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Ingår i: European Journal of Operational Research. - : Elsevier BV. - 0377-2217 .- 1872-6860. ; 78:1, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- We propose a heuristic solution technique for the capacitated concave minimum cost network flow problem based on a Lagrangean dualization of the problem. Despite its dual character the algorithm guarantees the generation of primal feasible solutions which are local optima and therefore candidates of being the global optimum. The Lagrangean dual is solved by a subgradient search procedure and provides a lower bound to the optimal value. The lower bound is, in general, stronger than the one obtained by a linear approximation of the original problem. It can be used as a judgement of the quality of the solution or in a branch and bound procedure. Computational results from randomly generated problems are presented
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| 6. |
- Larsson, Torbjörn, et al.
(författare)
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A partial linearization method for the traffic assignment problem
- 1993
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Ingår i: Optimization. - : Informa UK Limited. - 0233-1934 .- 1029-4945. ; 28:1, s. 47-61
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new solution technique for the traffic assignment problem. The approach is based on an iteratively improved nonlinear and separable approximation of the originally nonseparable objective function, and resembles the Frank-Wolfe algorithm in the sense that the subproblem separates with respect to commodities. Since the single-commodity subproblems are strictly convex, the new algorithm will not suffer from the poor convergence behaviour of the Frank-Wolfe algorithm, which is a consequence of the extreme solutions of its linear subproblems. The solution method is outlined along with convergence results, and a dual approach to the solution of the strictly convex subproblems is described. The performance of the algorithm is illustrated with two numerical examples
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| 7. |
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| 8. |
- Larsson, Torbjörn, et al.
(författare)
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An algorithm for nonlinear programs over Cartesian product sets
- 1990
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Ingår i: Optimization. - : Informa UK Limited. - 0233-1934 .- 1029-4945. ; 21:4, s. 535-542
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Tidskriftsartikel (refereegranskat)abstract
- We describe a solution procedure for nonseparable nonlinear programming problems over Cartesian product sets. Problems of this type frequently arise in transportation planning and in the analysis and design of computer communication networks. The basic algorithmic concept is to induce separability by linearizing the nonseparable part of the objective function, This algorithm and the well-known Frank-Wolfe method have many similarities. It is illustrated by a small numerical example.
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| 10. |
- Larsson, Torbjörn, 1950-
(författare)
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Det svenska statsskicket
- 1994
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Denna bok ger en grundläggande översikt över det svenska statsskickets uppbyggnad och funktion. Framställningen är uppbyggd kring tre teman. För det första görs i varje kapitel en kritisk granskning av hur den svenska demokratin i teorin är tänkt att fungera och hur den i praktiken utövas. För det andra anläggs genomgående ett historiskt perspektiv för att öka förståelsen för det svenska statsskickets nuvarande utformning och särdrag.
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