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  • 1
    Electronic Resource
    Electronic Resource
    Complexity and Modeling Aspects of Mesh Refinement into Quadrilaterals (2000)
    Springer
    Algorithmica 26 (2000), S. 148-171 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Mesh generation, Bidirected flows, \cal NP -completeness, Mesh decomposition, Computer-aided design.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We investigate the following mesh refinement problem: Given a mesh of polygons in three-dimensional space, find a decomposition into strictly convex quadrilaterals such that the resulting mesh is conforming and satisfies prescribed local density constraints. The conformal mesh refinement problem is shown to be feasible if and only if a certain system of linear equations over GF(2) has a solution. To improve mesh quality with respect to optimization criteria such as density, angles, and regularity, we introduce a reduction to a minimum cost bidirected flow problem. However, this model is only applicable if the mesh does not contain branching edges, that is, edges incident to more than two polygons. The general case with branchings, however, turns out to be strongly ${\cal NP}$ -hard. To enhance the mesh quality for meshes with branchings, we introduce a two-stage approach which first decomposes the whole mesh into components without branchings, and then uses minimum cost bidirected flows on the components in a second phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004539910008
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  • 2
    Electronic Resource
    Electronic Resource
    Stochastic scheduling problems I — General strategies (1984)
    Springer
    Mathematical methods of operations research 28 (1984), S. 193-260 
    Details
    ISSN: 1432-5217
    Keywords: Analytic behaviour of strategies ; continuous strategies ; ES strategies ; MES strategies ; machine idleness ; monotonicity behaviour ; optimal strategies ; preselectivity ; regular measure of performance ; scheduling problems ; stability ; stochastic dynamic optimization ; stochastically ordered distributions ; stochastic scheduling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The paper contains an introduction to recent developments in the theory of non-preemptive stochastic scheduling problems. The topics covered are: arbitrary joint distributions of activity durations, arbitrary regular measures of performance and arbitrary precedence and resource constraints. The possible instability of the problem is demonstrated and hints are given on stable classes of strategies available, including the combinatorial vs. analytical characterization of such classes. Given this background, the main emphasis of the paper is on the monotonicity behaviour of the model and on the existence of optimal strategies. Existing results are presented and generalized, in particular w.r.t. the cases of lower semicontinuous performance measures or joint duration distributions having a Lebesgue density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01919323
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  • 3
    Electronic Resource
    Electronic Resource
    Scheduling project networks with resource constraints and time windows (1988)
    Springer
    Annals of operations research 16 (1988), S. 199-240 
    Details
    ISSN: 1572-9338
    Keywords: Scheduling ; project networks ; MPM-networks ; time-windows ; order theoretic approach to scheduling ; disjunctive graph method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Project networks with time windows are generalizations of the well-known CPM and MPM networks that allow for the introduction of arbitrary minimal and maximal time lags between the starting and completion times of any pair of activities. We consider the problem to schedule such networks subject to arbitrary (even time dependent) resource constraints in order to minimize an arbitrary regular performance measure (i.e. a non-decreasing function of the vector of completion times). This problem arises in many standard industrial construction or production processes and is therefore particularly suited as a background model in general purpose decision support systems. The treatment is done by a structural approach that involves a generalization of both the disjunctive graph method in job shop scheduling [1] and the order theoretic methods for precedence constrained scheduling [18,23,24]. Besides theoretical insights into the problem structure, this approach also leads to rather powerful branch-and-bound algorithms. Computational experience with this algorithm is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02283745
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  • 4
    Electronic Resource
    Electronic Resource
    Algorithmic aspects of the substitution decomposition in optimization over relations, set systems and Boolean functions (1985)
    Springer
    Annals of operations research 4 (1985), S. 195-225 
    Details
    ISSN: 1572-9338
    Keywords: Boolean function ; clutter ; combinatorial optimization ; computational complexity ; composition tree ; decomposition algorithm ; graph ; independence system ; matroid ; modular decomposition ; oracle algorithm ; relation ; set system ; substitution decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In the last years, decomposition techniques have seen an increasing application to the solution of problems from operations research and combinatorial optimization, in particular in network theory and graph theory. This paper gives a broad treatment of a particular aspect of this approach, viz. the design of algorithms to compute the decomposition possibilities for a large class of discrete structures. The decomposition considered is thesubstitution decomposition (also known as modular decomposition, disjunctive decomposition, X-join or ordinal sum). Under rather general assumptions on the type of structure considered, these (possibly exponentially many) decomposition possibilities can be appropriately represented in acomposition tree of polynomial size. The task of determining this tree is shown to be polynomially equivalent to the seemingly weaker task of determining the closed hull of a given set w.r.t. a closure operation associated with the substitution decomposition. Based on this reduction, we show that for arbitrary relations the composition tree can be constructed in polynomial time. For clutters and monotonic Boolean functions, this task of constructing the closed hull is shown to be Turing-reducible to the problem of determining the circuits of the independence system associated with the clutter or the prime implicants of the Boolean function. This leads to polynomial algorithms for special clutters or monotonic Boolean functions. However, these results seem not to be extendable to the general case, as we derive exponential lower bounds for oracle decomposition algorithms for arbitrary set systems and Boolean functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02022041
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  • 5
    Electronic Resource
    Electronic Resource
    Preface (1988)
    Springer
    Annals of operations research 16 (1988), S. IX 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02283731
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  • 6
    Electronic Resource
    Electronic Resource
    Editorial (1995)
    Springer
    Annals of operations research 55 (1995), S. iii 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02031714
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  • 7
    Electronic Resource
    Electronic Resource
    Book reviews (1983)
    Springer
    Mathematical methods of operations research 27 (1983), S. 67-72 
    Details
    ISSN: 1432-5217
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01916902
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  • 8
    Electronic Resource
    Electronic Resource
    Stochastic scheduling problems II-set strategies- (1985)
    Springer
    Mathematical methods of operations research 29 (1985), S. 65-104 
    Details
    ISSN: 1432-5217
    Keywords: Additive cost criterion ; analytic behaviour of strategies ; ES strategy ; list schedule ; MES strategy ; priority rule ; quasi-stability ; regular measure of performance ; scheduling problems ; set strategy ; shift property ; stability ; stochastic scheduling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The paper introduces the finite class of set strategies for stochastic scheduling problems. It is shown that the knownstable classes of strategies such as ES and MES strategies are of this type, as arelist-scheduling strategies such as LEPT and SEPT and other, more complicatedpriority-type strategies. Roughly speaking, set strategies are characterized by the fact that the decision as to which jobs should be started at timet depends only on the knowledge of the two sets of jobs finished up to timet and being processed at timet. Contrary to list scheduling strategies, set strategies may involve deliberate idleness of machines, i.e. may not be greedy and can therefore not generally be induced by priority rules. It is demonstrated that set strategies have useful properties. They are e.g.λ n -almost everywhere continuous and therefore show satisfactorystability behaviour w.r.t. weak convergence of the joint distribution of job durations. Furthermore, the optimum w.r.t.all strategies is already attained on this class if job durations are independent and exponentially distributed and the performance measure fulfills a certainshift condition. This shift property is a quite natural concept and generalizes aspects of the notion ofadditivity in semi-Markov decision theory and stochastic dynamic optimization. Its complete analytical characterization is a major object of this paper. Typical additive cost criteria such as makespan and flowtime are of course covered, which yields simultaneously a first step towards generalization of optimality of LEPT and SEPT rules, as known for special cases. In fact, in view of the obtained optimality result, the question of when deliberate idleness of machines can be avoided, gains considerable interest, as it characterizes stochastic environments in whichpriority strategies are optimal. This provides a major link with current research on the analysis of networks of queues in the context of computer systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01918198
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  • 9
    Electronic Resource
    Electronic Resource
    Book reviews (1983)
    Springer
    Mathematical methods of operations research 27 (1983), S. 211-216 
    Details
    ISSN: 1432-5217
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01916918
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  • 10
    Electronic Resource
    Electronic Resource
    Gewinnung von cDNA-Klonen zweier RNA-Tumorviren des bovinen leukämievirus (BLV) und des endogenen Katzenvirus RD 114 aus einer FLK-zellinie (1986)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 6 (1986), S. 16-17 
    Details
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/abio.370060110
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