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Summary We propose a constraint-based approach for the two-dimensional rectangular packing problem with orthogonal orientations. This problem is to arrange a set of rectangles that can be rotated by 90 degrees into a rectangle of minimal size such that no two rectangles overlap. It arises in the placement of electronic devices during the layout of 2.5D System-in-Package integrated electronic systems...
Summary Symmetries are usually not desirable in integer programming (IP) models, because they derogate the performance of state-of-the-art IP-solvers like SCIP [1]. The reason for this is twofold: Solutions that are equivalent to ones already discovered are found again and again, which makes the search space \unnecessarily large". Furthermore, the bounds obtained from the linear programming (LP)...
Summary The airline crew pairing problem (CPP) is one of the classical problems in airline operations research due to its crucial impact on the cost structure of an airline. Moreover, the complex crew regulations and the large scale of the resulting mathematical programming models have rendered it an academically interesting problem over decades. The CPP is a tactical problem, typically solved over...
Summary In the report polynomial approximation algorithms with performance guarantees are presented for some modifications of TSP: for the minimum-weigt 2-PSP on metric distances and for the maximum-weight m- PSP in Euclidean space Rk.
Summary Intense competition in the current business environment leads firms to focus on selecting the best R&D project portfolio. Achieving this goal is tied down by uncertainty which is inherent in all R&D projects and therefore, investment decisions must be made within an optimization framework accounting for unavailability of data. In this paper, such a model is developed to hedge against...
Summary This paper considers the problem of clustering the vertices of a complete, edge weighted graph. The objective is to maximize the edge weights within the clusters (also called cliques). This so called Clique Partitioning Problem (CPP) is NP-complete, but it has several real life applications such as groupings in exible manufacturing systems, in biology, in flight gate assignment, etc.. Numerous...
Summary We present a Branch-and-Bound (B&B) method using combinatorial bounds for solving makespan minimization problems with sequence dependent setup costs. As an application we present a laser source sharing problem arising in car manufacturing
Summary Layouting items in a 2D-constrained container for maximizing container value and minimizing wasted space is a 2D Cutting and Packing (C&P) problem. We consider this task in the context of layouting news articles on xed-size pages in a system for delivering personalized newspapers. We propose a grid-based page structure where articles can be laid out in different variants for increased...
Summary In Clustering Problems, groups of similar subjects are to be retrieved from large data sets. Meta-heuristics are often used to obtain high quality solutions within reasonable time limits. Tabu search has proved to be a successful methodology for solving optimization problems, but applications to clustering problems are rare. In this paper, we construct a tabu search approach and compare it...
Summary The bandwidth minimization problem is a classical combinatorial optimization problem that has been studied since around 1960. It is formulated as follows. Given a connected graph G = (V;E) with n nodes and m edges, find a labeling π, i.e. a bijection between V and {1; 2;… ; n}, such that the maximum difference |π(u)–(v)|, uv ε E, is minimized. This problem is NP-hard even for binary trees...
Summary Gomory mixed-integer cuts play a central role in solving mixedinteger linear programs and are an integral part of state-of-the-art optimizers. In this paper we present some of the the existing approaches for improving the performance of the Gomory mixed-integer cut. We briey discuss the ideas of the different techniques and compare them based on computational results.
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