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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 47 (1990), S. 269-296 
    ISSN: 1436-4646
    Keywords: Cross decomposition ; convergence ; linear programming ; mixed integer programming ; nonlinear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Cross decomposition is a recent method for mixed integer programming problems, exploiting simultaneously both the primal and the dual structure of the problem, thus combining the advantages of Dantzig—Wolfe decomposition and Benders decomposition. Finite convergence of the algorithm equipped with some simple convergence tests has been proved. Stronger convergence tests have been proposed, but not shown to yield finite convergence. In this paper cross decomposition is generalized and applied to linear programming problems, mixed integer programming problems and nonlinear programming problems (with and without linear parts). Using the stronger convergence tests finite exact convergence is shown in the first cases. Unbounded cases are discussed and also included in the convergence tests. The behaviour of the algorithm when parts of the constraint matrix are zero is also discussed. The cross decomposition procedure is generalized (by using generalized Benders decomposition) in order to enable the solution of nonlinear programming problems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 82 (1998), S. 355-390 
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper, we discuss modeling with the specific purpose of solving the models withdifferent decomposition techniques. We first briefly describe the basic primal, dual andprimal - dual decomposition techniques, where a master problem is constructed by veryspecific modeling. The main part of the paper contains a discussion of variables and constraintduplication techniques, used to create a structure which can be used in decompositionmethods, i.e. enabling decomposition by modeling. We mainly treat linear mixed integerprogramming problems with several sets of variables andyor constraints. We propose severalways of incorporating variable andyor constraint duplication techniques in cross decomposition.In some cases, the constraints corresponding to the Lagrange multipliers that areneeded as input to the Lagrangian relaxation are not present in the primal subproblem.Despite this, we show how to determine these multipliers optimally. In some combinations,the input to a subproblem is not unique, and we discuss how to handle this non-uniquenessin an advantageous way. An application to the capacitated facility location problem isdescribed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 85 (1999), S. 157-179 
    ISSN: 1436-4646
    Keywords: Key words: transportation – d.c. functions – decomposition methods – branch-and-bound ; Mathematics Subject Classification (1991): 90C26, 90B06
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Well known extensions of the classical transportation problem are obtained by including fixed costs for the production of goods at the supply points (facility location) and/or by introducing stochastic demand, modeled by convex nonlinear costs, at the demand points (the stochastic transportation problem, [STP]). However, the simultaneous use of concave and convex costs is not very well treated in the literature. Economies of scale often yield concave cost functions other than fixed charges, so in this paper we consider a problem with general concave costs at the supply points, as well as convex costs at the demand points. The objective function can then be represented as the difference of two convex functions, and is therefore called a d.c. function. We propose a solution method which reduces the problem to a d.c. optimization problem in a much smaller space, then solves the latter by a branch and bound procedure in which bounding is based on solving subproblems of the form of [STP]. We prove convergence of the method and report computational tests that indicate that quite large problems can be solved efficiently. Problems up to the size of 100 supply points and 500 demand points are solved.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transmission electron microscopic analysis of serial sections showed that the receptor cells are innervated by only one neuron and not two as previously believed. The neuron's two dendrites constitute the afferent sensory nerves to the caudal ganglion where the neuron's cell body is located. Its neurite was traced a few micrometers, but the synaptic terminals were not identified. This sensory system in Oikopleura is compared with a similar caudal sensory system in the tadpole larva of Diplosoma macdonaldi investigated by Torrence and Cloney. ‘Wiring diagrams’ are proposed for the two systems. The ganglia, which receive the afferent sensory neurons, are discussed in terms of models for further research on simple integration systems.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Zoomorphology 104 (1984), S. 298-303 
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The structure of three cell types in the sensory vesicle is described: (1) The statocyte, with its intracellular statolith, is attached to the medial wall of the vesicle via delicate shaft cells. (2) Cells along the dorsal, ventral and lateral walls which contact the surface of the statocyte with long, slender cilia. These cells are presumed to be primary sensory cells. (3) Presumed secretory cells, along the rostral and dorsal walls, may have a dual function: (a) secretion of the vesicle fluid, and (b) stabilization of the wall by turgor created in characteristic intercellular cavities. The sensory vesicle in Oikopleura contains undoubtedly typical “statocyst components” adequate for a free-swimming animal, whereas the ascidian system is suggested to be a device that responds to gravitational stimuli and, together with temporary photoreceptors, aids the larva in finding optimal settling conditions.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Each second brain nerve consists of only one single fibre terminating at two different types of touch receptors in the oral region. The two nerves are the dendrites of two perikarya in the forebrain and are the master neurons for ciliary reversal in the stigmata, which is a two-neuron reflex. By axoaxonal synapses they control one motor neuron in the midbrain, i.e. the command neuron for ciliary reversal in both rings. This cell sends one axon branch in each third nerve to the cilia cells. In the left nerve this fibre is closely associated with a coarsely granulated accessory fibre, which apparently regulates the ciliary beat. The third nerves also contain one fibre each from another motor neuron in the hindbrain. These fibres make synaptic contacts at some specialized epidermal cells in the lateral trunk behind the ciliary rings. A few previously unknown nerves in the dorsal forebrain innervate epidermal cells. It is likely that the complicated epidermal motor innervation regulates the secretory activity of the oikoplasts or of the epidermal cells in constructing a new house, including the necessary complicated filters and food trapping mechanisms.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0878
    Keywords: Retina ; Polistotrema stouti ; Epithelial cells ; Receptor cells ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of receptor and epithelial cells in the retina of the pacific hagfish, Polistotrema stouti, has been investigated and compared with previous observations made in the atlantic hagfish, Myxine glutinosa. The receptor cells in Polistotrema have cylindrical outer segments which consist of numerous discs arranged perpendicularly to the long axis of the cell. Characteristic synaptic bodies (synaptic lamellae) occur at the receptor base. Membranous inclusions in the epithelial cells suggest phagocytosis of outer segments. In Myxine, the outer segments are whorl-like, and synaptic bodies are absent at the receptor base. There are no signs of phagocytosis in the epithelial cells. The results are discussed from a functional and phylogenetical point of view.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical methods of operations research 39 (1994), S. 157-186 
    ISSN: 1432-5217
    Keywords: Linear Programming ; Lagrange Multipliers ; Mathematical Programming ; Decomposition Methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The mean value cross decomposition method for linear programming problems is a modification of ordinary cross decomposition that eliminates the need for using the Benders or Dantzig-Wolfe master problem. It is a generalization of the Brown-Robinson method for a finite matrix game and can also be considered as a generalization of the Kornai-Liptak method. It is based on the subproblem phase in cross decomposition, where we iterate between the dual subproblem and the primal subproblem. As input to the dual subproblem we use the average of a part of all dual solutions of the primal subproblem, and as input to the primal subproblem we use the average of a part of all primal solutions of the dual subproblem. In this paper we give a new proof of convergence for this procedure. Previously convergence has only been shown for the application to a special separable case (which covers the Kornai-Liptak method), by showing equivalence to the Brown-Robinson method.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Computational optimization and applications 4 (1995), S. 293-316 
    ISSN: 1573-2894
    Keywords: transportation ; decomposition methods ; separable programming ; the Frank-Wolfe method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The stochastic transportation problem can be formulated as a convex transportation problem with nonlinear objective function and linear constraints. We compare several different methods based on decomposition techniques and linearization techniques for this problem, trying to find the most efficient method or combination of methods. We discuss and test a separable programming approach, the Frank-Wolfe method with and without modifications, the new technique of mean value cross decomposition and the more well known Lagrangean relaxation with subgradient optimization, as well as combinations of these approaches. Computational tests are presented, indicating that some new combination methods are quite efficient for large scale problems.
    Type of Medium: Electronic Resource
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