| 1. |
- Axsäter, Sven, et al.
(författare)
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Optimal "Position-Based" Warehouse Ordering in Divergent Two-Echelon Inventory Systems
- 2008
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 56:4, s. 976-991
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Tidskriftsartikel (refereegranskat)abstract
- A continuous-review two-echelon inventory system with one central warehouse and a number of nonidentical retailers is considered. The retailers face independent Poisson demand and apply standard (R, Q) policies. The retailer order quantities are fixed integer multiples of a certain batch size, representing the smallest pallet or container size transported in the system. A warehouse order may consist of one or several such batches. We derive a new policy for warehouse ordering, which is optimal in the broad class of position-based policies relying on complete information about the retailer inventory positions, transportation times, cost structures, and demand distributions at all facilities. The exact analysis of the new policy includes a method for determining the expected total inventory holding and backorder costs for the entire system. The class of position-based policies encompasses both the traditional installation-stock and echelon-stock (R, Q) policies, as well as the more sophisticated policies recently analyzed in the literature. The value of more carefully incorporating a richer information structure into the warehouse ordering policy is illustrated in a numerical study.
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| 2. |
- Eriksson, Kimmo, et al.
(författare)
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Optimal Expected Rank in a Two-Sided Secretary Problem
- 2007
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 55:5, s. 921-931
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Tidskriftsartikel (refereegranskat)abstract
- In a two-sided version of the famous secretary problem, employers search for a secretary at the same time as secretaries search for an employer. Nobody accepts being put on hold, and nobody is willing to take part in more than N interviews. Preferences are independent, and agents seek to optimize the expected rank of the partner they obtain among the N potential partners. We find that in any subgame perfect equilibrium, the expected rank grows as the square root of N (whereas it tends to a constant in the original secretary problem). We also compute how much agents can gain by cooperation.
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| 3. |
- Klamroth, Kathrin, et al.
(författare)
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Integrating Approximation and Interactive Decision Making in Multicriteria Optimization
- 2008
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 56:1, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- We present a new interactive hybrid approach for solving multicriteria optimization problems where features of approximation methods and interactive approaches are incorporated. We produce rough approximations of the nondominated set and let the decision maker indicate with the help of reference points where to refine the approximation. In this way, (s)he iteratively directs the search toward the best nondominated solution. After the decision maker has identified the most interesting region of the nondominated set, the final solution can be fine-tuned with existing interactive methods. We suggest different ways of updating the reference point as well as discuss visualizations that can be used in comparing different nondominated solutions. The new method is computationally relatively inexpensive and easy to use for the decision maker.
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| 4. |
- Larsson, Torbjörn, 1957-, et al.
(författare)
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Global optimality conditions for discrete and nonconvex optimization-with applications to Lagrangian heuristics and column generation
- 2006
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 54:3, s. 436-453
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Tidskriftsartikel (refereegranskat)abstract
- The well-known and established global optimality conditions based on the Lagrangian formulation of an optimization problem are consistent if and only if the duality gap is zero. We develop a set of global optimality conditions that are structurally similar but are consistent for any size of the duality gap. This system characterizes a primal-dual optimal solution by means of primal and dual feasibility, primal Lagrangian ε-optimality, and, in the presence of inequality constraints, a relaxed complementarity condition analogously called δ-complementarity. The total size ε + δ of those two perturbations equals the size of the duality gap at an optimal solution. Further, the characterization is equivalent to a near-saddle point condition which generalizes the classic saddle point characterization of a primal-dual optimal solution in convex programming. The system developed can be used to explain, to a large degree, when and why Lagrangian heuristics for discrete optimization are successful in reaching near-optimal solutions. Further, experiments on a set-covering problem illustrate how the new optimality conditions can be utilized as a foundation for the construction of new Lagrangian heuristics. Finally, we outline possible uses of the optimality conditions in column generation algorithms and in the construction of core problems. © 2006 INFORMS.
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| 5. |
- Marklund, Johan
(författare)
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Controlling Inventories in Divergent Supply Chains with Advance-Order Information
- 2006
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 54:5, s. 988-1010
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers a generic one-warehouse multiple-retailer inventory system under continuous review, where customers provide perfect advance-order information. More specifically, each customer order entails a due date specifying when the customer wants the item delivered. The information is perfect in the sense that a placed order cannot be revised. With the intent of using the advance-order information fully throughout the supply chain, each installation replenishes its stock using order base-stock policies (see Hariharan and Zipkin 1995). As for stock allocation, the presence of advance-order information at the central warehouse raises important questions regarding when reservations should be made for different retailers, i.e., how to make best use of the available temporal information to allocate items to retailers. Exact and approximate cost evaluation techniques are presented for the general case, the general reservation policy, as well as for the two special cases of reserving as early as possible, the complete reservation policy, and as late as possible, the last-minute allocation policy. A numerical study illustrates the performance of the proposed heuristics and provides insights on the value of using advance-order information in supply chain inventory control.
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