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  • Journals
  • Articles  (12,356)
  • Springer  (12,356)
  • 2000-2004  (12,356)
  • Computer Science  (7,424)
  • Natural Sciences in General  (4,960)
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  • Journals
  • Articles  (12,356)
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  • 1
    Electronic Resource
    Electronic Resource
    Exact order of Hoffman’s error bounds for elliptic quadratic inequalities derived from vector-valued Chebyshev approximation (2000)
    Springer
    Mathematical programming 88 (2000), S. 223-253 
    Details
    ISSN: 1436-4646
    Keywords: Mathematics Subject Classification (1991): 90C31, 41A50, 90C47
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. In this paper, we introduce the exact order of Hoffman’s error bounds for approximate solutions of elliptic quadratic inequalities. Elliptic quadratic inequalities are closely related to Chebyshev approximation of vector-valued functions (including complex-valued functions). The set of Chebyshev approximations of a vector-valued function defined on a finite set is shown to be Hausdorff strongly unique of order exactly 2 s for some nonnegative integer s. As a consequence, the exact order of Hoffman’s error bounds for approximate solutions of elliptic quadratic inequalities is exactly 2 -s for some nonnegative integer s. The integer s, called the order of deficiency (which is computable), quantifies how much the Abadie constraint qualification is violated by the elliptic quadratic inequalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070050015
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  • 2
    Electronic Resource
    Electronic Resource
    Error bounds for infinite systems of convex inequalities without Slater’s condition (2000)
    Springer
    Mathematical programming 88 (2000), S. 255-275 
    Details
    ISSN: 1436-4646
    Keywords: Key words: error bounds – Hölder error bound – semi–infinite program – convex inequalities – dual solutions – projection multipliers – weak Slater condition – Mangasarian–Fromovitz condition Mathematics Subject Classification (1991): 20E28, 20G40, 20C20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. The feasible set of a convex semi–infinite program is described by a possibly infinite system of convex inequality constraints. We want to obtain an upper bound for the distance of a given point from this set in terms of a constant multiplied by the value of the maximally violated constraint function in this point. Apart from this Lipschitz case we also consider error bounds of Hölder type, where the value of the residual of the constraints is raised to a certain power.¶We give sufficient conditions for the validity of such bounds. Our conditions do not require that the Slater condition is valid. For the definition of our conditions, we consider the projections on enlarged sets corresponding to relaxed constraints. We present a condition in terms of projection multipliers, a condition in terms of Slater points and a condition in terms of descent directions. For the Lipschitz case, we give five equivalent characterizations of the validity of a global error bound.¶We extend previous results in two directions: First, we consider infinite systems of inequalities instead of finite systems. The second point is that we do not assume that the Slater condition holds which has been required in almost all earlier papers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070050016
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  • 3
    Electronic Resource
    Electronic Resource
    Reminiscences on the development of the variational approach to Davidon’s variable-metric method (2000)
    Springer
    Mathematical programming 87 (2000), S. 265-280 
    Details
    ISSN: 1436-4646
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. In the mid-1960’s, Davidon’s method was brought to the author’s attention by M.J.D. Powell, one of its earliest proponents. Its great efficacy in solving a rather difficult computational problem in which the author was involved led to an attempt to find a “best” updating formula. “Best” seemed to suggest “least” in the sense of some norm, to further the stability of the method. This led to the idea of minimizing a generalized quadratic (Frobenius) norm with the quasi-Newton and symmetry constraints on the updates. Several interesting formulas were derived, including the Davidon-Fletcher-Powell formula (as shown by Goldfarb). This approach was extended to the derivation of updates requiring no derivatives, and to Broyden-like updates for the solution of simultaneous nonlinear equations. Attempts were made to derive minimum-norm corrections in product-form updates, with an eye to preserving positive-definiteness. In the course of this attempt, it was discovered that the DFP formula could be written as a product, leading to some interesting theoretical developments. Finally, a linearized product-form update was developed which was competitive with the best update (BFGS) of that time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070050114
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  • 4
    Electronic Resource
    Electronic Resource
    Interior-point methods for nonconvex nonlinear programming: orderings and higher-order methods (2000)
    Springer
    Mathematical programming 87 (2000), S. 303-316 
    Details
    ISSN: 1436-4646
    Keywords: Key words: nonlinear programming – interior-point methods – nonconvex optimization – predictor-corrector – matrix ordering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. The paper extends prior work by the authors on loqo, an interior point algorithm for nonconvex nonlinear programming. The specific topics covered include primal versus dual orderings and higher order methods, which attempt to use each factorization of the Hessian matrix more than once to improve computational efficiency. Results show that unlike linear and convex quadratic programming, higher order corrections to the central trajectory are not useful for nonconvex nonlinear programming, but that a variant of Mehrotra’s predictor-corrector algorithm can definitely improve performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070050116
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  • 5
    Electronic Resource
    Electronic Resource
    Robust solutions of Linear Programming problems contaminated with uncertain data (2000)
    Springer
    Mathematical programming 88 (2000), S. 411-424 
    Details
    ISSN: 1436-4646
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Optimal solutions of Linear Programming problems may become severely infeasible if the nominal data is slightly perturbed. We demonstrate this phenomenon by studying 90 LPs from the well-known NETLIB collection. We then apply the Robust Optimization methodology (Ben-Tal and Nemirovski [1–3]; El Ghaoui et al. [5, 6]) to produce “robust” solutions of the above LPs which are in a sense immuned against uncertainty. Surprisingly, for the NETLIB problems these robust solutions nearly lose nothing in optimality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011380
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  • 6
    Electronic Resource
    Electronic Resource
    The mixed vertex packing problem (2000)
    Springer
    Mathematical programming 89 (2000), S. 35-53 
    Details
    ISSN: 1436-4646
    Keywords: Mathematics Subject Classification (1991): 90C10, 90C11, 90C57
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We study a generalization of the vertex packing problem having both binary and bounded continuous variables, called the mixed vertex packing problem (MVPP). The well-known vertex packing model arises as a subproblem or relaxation of many 0-1 integer problems, whereas the mixed vertex packing model arises as a natural counterpart of vertex packing in the context of mixed 0-1 integer programming. We describe strong valid inequalities for the convex hull of solutions to the MVPP and separation algorithms for these inequalities. We give a summary of computational results with a branch-and-cut algorithm for solving the MVPP and using it to solve general mixed-integer problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101070000154.
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  • 7
    Electronic Resource
    Electronic Resource
    Guest editorial (2000)
    Springer
    AI & society 14 (2000), S. 1-2 
    Details
    ISSN: 1435-5655
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206125
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic Meeting Support for Councils (2000)
    Springer
    AI & society 14 (2000), S. 48-70 
    Details
    ISSN: 1435-5655
    Keywords: Council work ; CSCW ; Evaluation ; Group support systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract City councils hold meetings several times a week. There is a need for computer support at certain meetings. This paper examines the potential for group support systems for use in city council meetings and shows in what ways they can be helpful in pre-meeting and post-meeting activities. The study is based on 17 computer-supported city council meetings, carried out in Stuttgart, Kornwestheim and other cities as part of the Cuparla Project between 1996 and 1998. Three of these meetings are described in the paper as brief case studies. Following this, all 17 meeting sequences are evaluated and analysed. Guidelines have been developed from the results of the study for the introduction of group support systems in city council meetings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206128
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  • 9
    Electronic Resource
    Electronic Resource
    The creative landscapes column: All our futures (2000)
    Springer
    AI & society 14 (2000), S. 142-149 
    Details
    ISSN: 1435-5655
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206132
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  • 10
    Electronic Resource
    Electronic Resource
    TheEvolve project: Component-based tailorability for CSCW applications (2000)
    Springer
    AI & society 14 (2000), S. 120-141 
    Details
    ISSN: 1435-5655
    Keywords: Coordination tool ; CSCW ; Software components ; Tailorability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Tailorability is generally regarded as a key property of groupware systems owing to the dynamics and differentiation of cooperative work. This article investigates the use of software components as a generic architectural concept for designing tailorable groupware applications. First, the issues raised by this approach are discussed in the context of an exploratory experiment during which component-based tailorability was applied to a real tailoring problem in thePoliTeam project. The experiment's results led us to concentrate on questions concerning the support of distributed CSCW applications. As a consequence, we have developed theEvolve platform, whose design concepts are described. Furthermore, a concrete example for the application of the approach to the design of a tailorable distributed coordination tool is given. We discuss related work, summarise the current state of the component-based tailorability approach and propose venues of further research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206131
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