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  • Articles  (9,679)
  • Articles: DFG German National Licenses  (9,679)
  • Springer  (9,679)
  • 1990-1994  (9,533)
  • 1960-1964  (146)
  • Computer Science  (8,428)
  • Nature of Science, Research, Systems of Higher Education, Museum Science  (1,251)
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  • Articles  (9,679)
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  • 1
    Electronic Resource
    Electronic Resource
    A Farkas lemma for difference sublinear systems and quasidifferentiable programming (1994)
    Springer
    Mathematical programming 63 (1994), S. 109-125 
    Details
    ISSN: 1436-4646
    Keywords: Alternative theorems ; quasidifferentiable programming ; nonsmooth analysis ; optimality conditions ; difference convex programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A new generalized Farkas theorem of the alternative is presented for systems involving functions which can be expressed as the difference of sublinear functions. Various other forms of theorems of the alternative are also given using quasidifferential calculus. Comprehensive optimality conditions are then developed for broad classes of infinite dimensional quasidifferentiable programming problems. Applications to difference convex programming and infinitely constrained concave minimization problems are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582061
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  • 2
    Electronic Resource
    Electronic Resource
    A deep cut ellipsoid algorithm for convex programming: Theory and applications (1994)
    Springer
    Mathematical programming 63 (1994), S. 83-108 
    Details
    ISSN: 1436-4646
    Keywords: Convex programming ; deep cut ellipsoid algorithm ; rate of convergence ; location theory ; min—max programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper proposes a deep cut version of the ellipsoid algorithm for solving a general class of continuous convex programming problems. In each step the algorithm does not require more computational effort to construct these deep cuts than its corresponding central cut version. Rules that prevent some of the numerical instabilities and theoretical drawbacks usually associated with the algorithm are also provided. Moreover, for a large class of convex programs a simple proof of its rate of convergence is given and the relation with previously known results is discussed. Finally some computational results of the deep and central cut version of the algorithm applied to a min—max stochastic queue location problem are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582060
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  • 3
    Electronic Resource
    Electronic Resource
    The Steiner tree polytope and related polyhedra (1994)
    Springer
    Mathematical programming 63 (1994), S. 157-182 
    Details
    ISSN: 1436-4646
    Keywords: Steiner tree ; series—parallel graphs ; polyhedral characterization ; projection ; facets ; formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We consider the vertex-weighted version of the undirected Steiner tree problem. In this problem, a cost is incurred both for the vertices and the edges present in the Steiner tree. We completely describe the associated polytope by linear inequalities when the underlying graph is series—parallel. For general graphs, this formulation can be interpreted as a (partial) extended formulation for the Steiner tree problem. By projecting this formulation, we obtain some very large classes of facet-defining valid inequalities for the Steiner tree polytope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582064
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  • 4
    Electronic Resource
    Electronic Resource
    Examples of max-flow and min-cut problems with duality gaps in continuous networks (1994)
    Springer
    Mathematical programming 63 (1994), S. 213-234 
    Details
    ISSN: 1436-4646
    Keywords: Max-flow problem ; min-cut problem ; duality gap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Strang (Mathematical Programming 26, 1983) gave a method to establish a max-flow min-cut theorem in a domain of a Euclidean space. The method can be applied also to max-flow min-cut problems defined by Iri (Survey of Mathematical Programming, North-Holland, 1979) whenever the capacity functions of max-flow problems are bounded and continuous. This paper deals with max-flow min-cut problems of Strang and Iri with unbounded or noncontinuous capacity functions. It is proved that, in such problems, max-flow min-cut theorems may fail to hold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582067
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  • 5
    Electronic Resource
    Electronic Resource
    The complex of maximal lattice free simplices (1994)
    Springer
    Mathematical programming 66 (1994), S. 273-281 
    Details
    ISSN: 1436-4646
    Keywords: Minimal test sets for integer programming ; Simplicial complexes ; Maximal lattice free bodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The simplicial complexK(A) is defined to be the collection of simplices, and their proper subsimplices, representing maximal lattice free bodies of the form (x: Ax⩽b), withA a fixed generic (n + 1) ×n matrix. The topological space associated withK(A) is shown to be homeomorphic to ℝ n , and the space obtained by identifying lattice translates of these simplices is homeorphic to then-torus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581150
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  • 6
    Electronic Resource
    Electronic Resource
    Minimum cost multiflows in undirected networks (1994)
    Springer
    Mathematical programming 66 (1994), S. 313-325 
    Details
    ISSN: 1436-4646
    Keywords: Network ; Multicommodity flow ; Minimum cost flow ; Edge-disjoint paths
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetN = (G, T, c, a) be a network, whereG is an undirected graph,T is a distinguished subset of its vertices (calledterminals), and each edgee ofG has nonnegative integer-valuedcapacity c(e) andcost a(e). Theminimum cost maximum multi(commodity)flow problem (*) studied in this paper is to find ac-admissible multiflowf inG such that: (i)f is allowed to contain partial flows connecting any pairs of terminals, (ii) the total value off is as large as possible, and (iii) the total cost off is as small as possible, subject to (ii). This generalizes, on one hand, the undirected version of the classical minimum cost maximum flow problem (when |T| = 2), and, on the other hand, the problem of finding a maximum fractional packing ofT-paths (whena ≡ 0). Lovász and Cherkassky independently proved that the latter has a half-integral optimal solution. A pseudo-polynomial algorithm for solving (*) has been developed earlier and, as its consequence, the theorem on the existence of a half-integral optimal solution for (*) was obtained. In the present paper we give a direct, shorter, proof of this theorem. Then we prove the existence of a half-integral optimal solution for the dual problem. Finally, we show that half-integral optimal primal and dual solutions can be designed by a combinatorial strongly polynomial algorithm, provided that some optimal dual solution is known (the latter can be found, in strongly polynomial time, by use of a version of the ellipsoid method).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581152
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  • 7
    Electronic Resource
    Electronic Resource
    Second-order necessary and sufficient conditions in nonsmooth optimization (1994)
    Springer
    Mathematical programming 66 (1994), S. 379-402 
    Details
    ISSN: 1436-4646
    Keywords: Primary 49A52, 90C30 ; Secondary 26E15, 58C20 ; Nonsmooth analysis ; Second order necessary and sufficient conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we generalize and sharpen R.W. Chaney's results on unconstrained and constrained second-order necessary and sufficient optimality conditions [5–7] for general Lipschitz functions without the semismoothness assumption
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581156
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  • 8
    Electronic Resource
    Electronic Resource
    Error bounds for analytic systems and their applications (1994)
    Springer
    Mathematical programming 67 (1994), S. 1-28 
    Details
    ISSN: 1436-4646
    Keywords: Error bound ; Analytic systems ; Karush—Kuhn—Tucker conditions ; Affine variational inequality ; Complementarity problem ; Integer feasibility problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Using a 1958 result of Lojasiewicz, we establish an error bound for analytic systems consisting of equalities and inequalities defined by real analytic functions. In particular, we show that over any bounded region, the distance from any vectorx in the region to the solution set of an analytic system is bounded by a residual function, raised to a certain power, evaluated atx. For quadratic systems satisfying certain nonnegativity assumptions, we show that this exponent is equal to 1/2. We apply the error bounds to the Karush—Kuhn—Tucker system of a variational inequality, the affine variational inequality, the linear and nonlinear complementarity problem, and the 0–1 integer feasibility problem, and obtain new error bound results for these problems. The latter results extend previous work for polynomial systems and explain why a certain square-root term is needed in an error bound for the (monotone) linear complementarity problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582210
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  • 9
    Electronic Resource
    Electronic Resource
    An infeasible-interior-point algorithm for linear complementarity problems (1994)
    Springer
    Mathematical programming 67 (1994), S. 29-51 
    Details
    ISSN: 1436-4646
    Keywords: Infeasible-interior-point methods ; Linear complementarity problems ; Q-subquadratic convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We modify the algorithm of Zhang to obtain anO(n2L) infeasible-interior-point algorithm for monotone linear complementarity problems that has an asymptoticQ-subquadratic convergence rate. The algorithm requires the solution of at most two linear systems with the same coefficient matrix at each iteration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582211
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  • 10
    Electronic Resource
    Electronic Resource
    Quantitative stability in stochastic programming (1994)
    Springer
    Mathematical programming 67 (1994), S. 99-108 
    Details
    ISSN: 1436-4646
    Keywords: Stochastic programming with recourse ; Quantitative stability ; Lipschitz continuity ; Law of Iterated Logarithm ; Kolmogorov—Smirnov distance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we study stability of optimal solutions of stochastic programming problems with fixed recourse. An upper bound for the rate of convergence is given in terms of the objective functions of the associated deterministic problems. As an example it is shown how it can be applied to derivation of the Law of Iterated Logarithm for the optimal solutions. It is also shown that in the case of simple recourse this upper bound implies upper Lipschitz continuity of the optimal solutions with respect to the Kolmogorov—Smirnov distance between the corresponding cumulative probability distribution functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582215
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  • 11
    Electronic Resource
    Electronic Resource
    Polynomiality of infeasible-interior-point algorithms for linear programming (1994)
    Springer
    Mathematical programming 67 (1994), S. 109-119 
    Details
    ISSN: 1436-4646
    Keywords: Polynomial-time ; Linear programming ; Primal-dual ; Interior-point algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Kojima, Megiddo, and Mizuno investigate an infeasible-interior-point algorithm for solving a primal—dual pair of linear programming problems and they demonstrate its global convergence. Their algorithm finds approximate optimal solutions of the pair if both problems have interior points, and they detect infeasibility when the sequence of iterates diverges. Zhang proves polynomial-time convergence of an infeasible-interior-point algorithm under the assumption that both primal and dual problems have feasible points. In this paper, we show that a modification of the Kojima—Megiddo—Mizuno algorithm “solves” the pair of problems in polynomial time without assuming the existence of the LP solution. Furthermore, we develop anO(nL)-iteration complexity result for a variant of the algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582216
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  • 12
    Electronic Resource
    Electronic Resource
    Implementing an efficient minimum capacity cut algorithm (1994)
    Springer
    Mathematical programming 67 (1994), S. 325-341 
    Details
    ISSN: 1436-4646
    Keywords: Minimum capacity cut ; Network flow ; Polynomial algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper, we present an efficient implementation of theO(mn + n 2 logn) time algorithm originally proposed by Nagamochi and Ibaraki (1992) for computing the minimum capacity cut of an undirected network. To enhance computation, various ideas are added so that it can contract as many edges as possible in each iteration. To evaluate the performance of the resulting implementation, we conducted extensive computational experiments, and compared the results with that of Padberg and Rinaldi's algorithm (1990), which is currently known as one of the practically fastest programs for this problem. The results indicate that our program is considerably faster than Padberg and Rinaldi's program, and its running time is not significantly affected by the types of the networks being solved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582226
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  • 13
    Electronic Resource
    Electronic Resource
    A proximal-based decomposition method for convex minimization problems (1994)
    Springer
    Mathematical programming 64 (1994), S. 81-101 
    Details
    ISSN: 1436-4646
    Keywords: 90C25 ; Convex programming ; Proximal methods ; Augmented Lagrangian ; Decomposition-splitting methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper presents a decomposition method for solving convex minimization problems. At each iteration, the algorithm computes two proximal steps in the dual variables and one proximal step in the primal variables. We derive this algorithm from Rockafellar's proximal method of multipliers, which involves an augmented Lagrangian with an additional quadratic proximal term. The algorithm preserves the good features of the proximal method of multipliers, with the additional advantage that it leads to a decoupling of the constraints, and is thus suitable for parallel implementation. We allow for computing approximately the proximal minimization steps and we prove that under mild assumptions on the problem's data, the method is globally convergent and at a linear rate. The method is compared with alternating direction type methods and applied to the particular case of minimizing a convex function over a finite intersection of closed convex sets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582566
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  • 14
    Electronic Resource
    Electronic Resource
    Some perturbation theory for linear programming (1994)
    Springer
    Mathematical programming 65 (1994), S. 73-91 
    Details
    ISSN: 1436-4646
    Keywords: Perturbation theory ; Sensitivity analysis ; Infinite linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581690
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  • 15
    Electronic Resource
    Electronic Resource
    Scheduling two jobs with fixed and nonfixed routes (1994)
    Springer
    Computing 52 (1994), S. 17-30 
    Details
    ISSN: 1436-5057
    Keywords: 90B35 ; Optimization ; optimal makespan schedule ; optimal mean flow time schedule ; regular criterion ; polynomial time algorithm ; NP-hard problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es werden Reihenfolge-probleme mit zwei Aufträgen undm Maschinen untersucht, wobei die technologische Reihenfolge der Maschinen für den ersten Auftrag gegeben und für den zweiten Auftrag variabel ist. Es wird bewiesen, daß die Probleme “Minimierung der Gesamtbearbeitungszeit” und “Minimierung der mittleren Durchlaufzeit” NP-hard sind, wenn eine Unterbrechung der Operationen verboten ist. Für ein beliebiges reguläres Kriterium wird bei Zulassung von Unterbrechungen einO(n *) Algorithmus entwickelt, wobei mitn * die maximale Anzahl der Operationen für den ersten Auftrag bezeichnet wird.
    Notes: Abstract The shop-scheduling problem with two jobs andm machines is considered under the condition that the machine order is fixed in advance for the first job and nonfixed for the second job. The problems of makespan and mean flow time minimization are proved to be NP-hard if operation preemption is forbidden. In the case of preemption allowance for any given regular criterion theO(n *) algorithm is proposed. Here,n * is the maximum number of operations per job.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02243393
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  • 16
    Electronic Resource
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    A universal generator for discrete log-concave distributions (1994)
    Springer
    Computing 52 (1994), S. 89-96 
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    ISSN: 1436-5057
    Keywords: 65C10 ; 68C25 ; Random number generation ; log-concave distributions ; rejection method ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir erklären einen Algorithmus, der Stichproben von beliebigen log-konkaven Verteilungen (z.B. Binomial- und Hypergeometrische Verteilung) erzeugt. Er basiert auf Verwerfung von einer diskreten dominierenden Verteilung, die aus Teilen der geometrischen Verteilung zusammengesetzt wird. Der Algorithmus is gleichmäßig schnell für alle diskreten log-konkaven Verteilungen und nicht viel langsamer als Algorithmen, die nur für eine bestimmte Verteilung verwendet werden können.
    Notes: Abstract We give an algorithm that can be used to sample from any discrete log-concave distribution (e.g. the binomial and hypergeometric distributions). It is based on rejection from a discrete dominating distribution that consists of parts of the geometric distribution. The algorithm is uniformly fast for all discrete log-concave distributions and not much slower than algorithms designed for a single distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02243398
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  • 17
    Electronic Resource
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    Error analysis of null space algorithm for linear equality constrained least squares problems (1994)
    Springer
    Computing 52 (1994), S. 161-176 
    Details
    ISSN: 1436-5057
    Keywords: 65G05 ; 65K05 ; 90C20 ; Error analysis ; constrained optimization ; least squares problems ; null space method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die numerische Stabilität des Nullraum-Verfahrens [2], [7] für lineare Ausgleichsprobleme mit linearen Gleichungs-Nebenbedingungen wird einer Rückwärtsanalyse unterzogen. An Hand einer Klasse von Testproblemen wird experimentell das Verhalten des Verfahrens dargestellt.
    Notes: Abstract The numerical stability of the null space method [2], [7] for linear least-squares problems with linear equality constraints is studied using a backward error analysis. A class of test problems is also considered in order to show experimentally the behaviour of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02238074
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  • 18
    Electronic Resource
    Electronic Resource
    Verified inclusion for eigenvalues of the first order PLL equation with general phase detector characteristics (1994)
    Springer
    Computing 52 (1994), S. 213-232 
    Details
    ISSN: 1436-5057
    Keywords: 34B30 ; 65L15 ; 39A10 ; 65G10 ; Hill's equation, cycle slip rate ; eigenvalues ; continued fractions ; verfication ; comparison theorem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir stellen eine Methode vor, die mit Hilfe von Matrix-Kettenbrüchen und dem Sturm'schen Vergleichssatz die Verifikation von Eigenwerten des Randwertproblems der Phase-Locked-Loop-Gleichung erster Ordnung $$pu'' + (\lambda + \tilde g)u = 0$$ ,p = 1/SNR, mit allgemeiner phasenvergleichender Charakteristik $$\tilde g(\phi )$$ erlaubt.
    Notes: Abstract We present a method depending on matrix continued fractions and Sturm's comparison theorem to obtain verified inclusions for eigenvalues of the underlying boundary value problem of the first-order phase locked loop equation $$pu'' + (\lambda + \tilde g)u = 0$$ ,p = 1/SNR with general phase detector characteristic $$\tilde g(\phi )$$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246504
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  • 19
    Electronic Resource
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    Lower bounds for 1-, 2- and 3-dimensional on-line bin packing algorithms (1994)
    Springer
    Computing 52 (1994), S. 281-297 
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    ISSN: 1436-5057
    Keywords: 90B35 ; 90C27 ; Combinatorial problems ; on-line ; bin packing ; suboptimal algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung In dieser Arbeit untersuchen wir asymptotische untere Schranken von on-line Algorithmen für verschiedene Arten des Bin-Packungsproblems. Kürzlich haben Galambos und Frenk einen einfachen Beweis der unteren Schranke 1.536... für das eindimensionale Packungsproblem angegeben. Ausgehend von ihren Überlegungen präsentieren wir eine allgemeine Technik zur Herleitung unterer Schranken auch für andere Packungsprobleme. Wir verwenden diese Technik, um neue untere Schranken für das zweidimensionale (1,802...) und das dreidimensionale (1,974...) Packungsproblem zu beweisen.
    Notes: Abstract In this paper we discuss lower bounds for the asymptotic worst case ratio of on-line algorithms for different kind of bin packing problems. Recently, Galambos and Frenk gave a simple proof of the 1.536 ... lower bound for the 1-dimensional bin packing problem. Following their ideas, we present a general technique that can be used to derive lower bounds for other bin packing problems as well. We apply this technique to prove new lower bounds for the 2-dimensional (1.802...) and 3-dimensional (1.974...) bin packing problem.
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    URL: http://dx.doi.org/10.1007/BF02246509
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  • 20
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    Numerical approaches to the kinetic semiconductor equation (1994)
    Springer
    Computing 52 (1994), S. 39-49 
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    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung In dieser Arbeit untersuchen wir mehrer Methoden zur numerischen Berechnung von Transportphänomenen in Halbleitern, die auf kinetischen Gleichungen basieren. Insbesondere betrachten wir den Aufwand an Rechenzeit für die verschiedenen Algorithmen, der in einigen Fällen die Anwendung auf höherdimensionale Probleme unmöglich macht.
    Notes: Abstract In this paper we consider several methods for the numerical computation of carrier transport effects in semiconductors based on kinetic equations. We especially discuss the computational costs of the different algorithms, which in some cases prohibit their application to higher dimensional problems.
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    URL: http://dx.doi.org/10.1007/BF02243395
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  • 21
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    An efficient implementation of certain iterative refinement preconditioners (1994)
    Springer
    Computing 52 (1994), S. 51-63 
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    ISSN: 1436-5057
    Keywords: 65F10 ; 65N20 ; 65N30 ; Preconditioning ; conjugate gradients ; local refinement ; elliptic problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Präkonditionierte iterative Methoden von Typ der konjugierten Gradienten zur Lösung elliptischer und parabolischer Probleme werden auf lokal verfeinerten Gittern untersucht. Die Komponenten des während der Iteration berechneten Residuumsvektors werden betrachtet. Man erkennt, daß sie nur an den Knoten nahe dem Übergang zwischen feinem und grobem Gitter ungleich null sind. Diese Eigenschaft wird verwendet, um die präkonditionierte CG-Methode oder, wenn wie im parabolischen Fall die Matrix nicht symmetrisch ist, verallgemeinerte CG- oder GMRES-Methoden zu formulieren. Dadurch wird Speicherplatz und Rechenaufwand eingespart.
    Notes: Abstract Preconditioned iterative methods of conjugate gradient type for solving elliptic and parabolic problems discretized on grids wth local refinement are considered. The sparsity pattern of the residuals computed throughout the iterative process is investigated. It turns out that they are nonzero only near the interface nodes between the coarse-and fine-grids. This observation is used to formulate the preconditioned CG, and when the matrix is not symmetric as in the parabolic case—the generalized CG and GMRES methods, thus substantially saving storage and computation.
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    URL: http://dx.doi.org/10.1007/BF02243396
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  • 22
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    On numerical cubatures of nearly singular surface integrals arising in BEM collocation (1994)
    Springer
    Computing 52 (1994), S. 139-159 
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    ISSN: 1436-5057
    Keywords: 65N38 ; 45B05 ; 45E05 ; 45Z10 ; 65Y20 ; Boundary element method ; numerical quadrature ; collocation ; panel method ; cubature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die Arbeit präsentiert effiziente Verfahren zur Bestimmung fast singulärer Integrale, wie sie in großer Anzahl bei der Diskretisierung von Integralgleichungen durch Kollokation auftreten. Die Methode basiert auf der Einführung von lokalen Polarkoordinaten um eine Dreiecksecke. Die innere Integration läßt sich analytisch durchführen, wobei man entweder entsprechende numerisch stabile Formeln oder Funktionsapproximationen verwenden kann. Die äußere Integration kann mit gewünschter Genauigkeit mittels Gauß-Legendre-Quadratur ermittelt werden. Numerische Tests unterstreichen die Effizienz unserer Methode.
    Notes: Abstract In this paper we present efficient methods to approximate nearly singular surface integrals arising massively when discretizing boundary integral equations via the collocation method. The idea is to introduce local polar coordinates centred at a corner of the triangle. Thus it is possible to perform the inner integration analytically, where either the corresponding formulae can be evaluated numerically stable or can be replaced by simple (rational) approximation quite efficiently. We show that the outer integration can be performed by simple Gauß-Legendre quadrature and how to adapt the order of the Gauß formulae to a required order of consistency. Numerical tests will emphasize the efficiency of our method.
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    URL: http://dx.doi.org/10.1007/BF02238073
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  • 23
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    The interval Sylvester equation (1994)
    Springer
    Computing 52 (1994), S. 233-244 
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    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird eine notwendige und hinreichende bedingung für die Existenz der Lösung der Intervall-Sylvester Gleichung angegeben. Dazu wird eine modifizierte Oettli Ungleichung abgeleitet, um die Lösung zu charakterisieren. Mehrere direkte Methoden für das Lösen der Gleichung werden vorgeschlagen und miteinander verglichen. Diese Methoden basieren auf verschiedenen Techniken wie Simulation, Lineare Programmierung, dem Zusammenhang zwischen einer Intervall-Sylvester Gleichung und einem Intervall-linearen System wie auch der Sensitivitätsanalyse. Weiters wird eine iterative Technik bereitgestellt, für die Konvergenz-Bedingungen verfügbar sind. Als Anwendung wird die Wurzel einer Intervall-Matrix berechnet.
    Notes: Abstract In this paper a necessary and sufficient condition for the existence of a solution for the interval Sylvester equation is given. A modified Oettli's inequality is derived to characterize the solution. Many direct methods for solving the equation are suggested and compared to each other. These methods are based on different techniques such as simulation, linear programming, correspondence between an interval Sylvester equation and an interval linear system as well as sensitivity analysis. An iterative technique for solving the interval Sylvester equation is provided with special conditions to guarantee the convergence. The square root of an interval matrix is calculated as an application to solving interval Sylvester equations.
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    URL: http://dx.doi.org/10.1007/BF02246505
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    A fast dot-product algorithm with minimal rounding errors (1994)
    Springer
    Computing 52 (1994), S. 355-369 
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    ISSN: 1436-5057
    Keywords: (Exact) computer arithmetic ; numerical algorithms ; dot-product computation ; summation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird ein Algorithmus vorgestellt, der ein Skalarprodukt beliebiger Länge auswertet. Bei der Berechnung tritt nur ein minimaler Rundungsfehler auf, der nicht von der Anzahl der Summanden abhängt. Der Algorithmus hat einen konstanten Speicherbedarf, einen linearen Rechenaufwand und es ist keine Erweiterung der arithmetischen Grundoperationen notwendig. Durch eine kleine Änderung erhält man einen Algorithmus, der das Ergebnis in Maschinengenauigkeit berechnet. Wegen seiner einfachen Struktur kann der Algorithmus leicht in Hardware realisiert werden.
    Notes: Abstract We present a new algorithm which computes dot-products of arbitrary length with minimal rounding errors, independent of the number of addends. The algorithm has anO(n) time andO(1) memory complexity and does not need extensions of the arithmetic kernel, i.e, usual floating-point operations. A slight modification yields an algorithm which computes the dot-product in machine precision. Due to its simplicity, the algorithm can easily be implemented in hardware.
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    URL: http://dx.doi.org/10.1007/BF02276882
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    Modified compound quadrature rules for strongly singular integrals (1994)
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    Computing 52 (1994), S. 337-354 
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    ISSN: 1436-5057
    Keywords: Primary 65D30 ; 41A55 ; Secondary 65R10 ; Cauchy principal value integrals ; Hadamard finite part integrals ; modified quadrature formula ; midpoint formula ; trapezoidal formula ; Simpson formula ; Peano constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir zeigen, daß der Fehlerterm jedes modifizierten zusammengesetzten Quadraturverfahrens für Cauchy-Hauptwert-Integrale mit Exaktheitsgrads die bestmögliche Größenordnung in den KlassenC k [−1,1],k=1,2,...,s hat, aber nich inC s+1[−1,1]. Explizite obere Schranken für die Fehlerkonstanten der modifizierten Mittelpunkt-, Trapez- und Simpson-Verfahren werden angegeben. Des weiteren werden die Ergebnisse auf die entsprechenden Verfahren für Finite-Part-Integrale vom Hadamardschen Typ verallgemeinert.
    Notes: Abstract We show that the error term of every modified compound quadrature rule for Cauchy principal value integrals with degree of exactnesss is of optimal order of magnitude in the classesC k [−1,1],k=1,2,...,s, but not inC s+1[−1,1]. We give explicit upper bounds for the error constants of the modified midpoint rule, the modified trapezoidal rule and the modified Simpson rule. Furthermore, the results are generalized to analogous rules for Hadamard-type finite part integrals.
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    Heuristics for laying out information graphs (1994)
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    Computing 52 (1994), S. 389-405 
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    ISSN: 1436-5057
    Keywords: 05C99 ; 68P20 ; 68R10 ; 90C27 ; Graph layout ; graph partitioning ; combinatorial optimization ; information retrieval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Der Begriff eines Informationsgraphen wird als eine Repräsentation für objektorientierte Datenbanken vorgestellt. Das Wiederauffinden von Informationen ergibt sich als Optimierungsproblem bezüglich der so entstandenen Informationsgraphen. Das Layout stellt nicht nur den Raumbedarf der Datenbank sondern auch den Zeitbedarf des Wiederauffindens der Informationen dar. Heuristiken für das Wiederauffindungsproblem werden identifiziert und experimentell ausgewertet. Eine neue Heuristik-connectivity traversal-ergibt sowohl ein schnelles Wiederauffindungsverfahren wie auch qualitativ hochwertige Layouts.
    Notes: Abstract The concept of an information graph is introduced as a representation for object-oriented databases. The retrieval layout problem is an optimization problem defined over the class of information graphs. The layout abstracts the space efficiency of representing the database as well as the time efficiency of information retrieval. Heuristics for the retrieval layout problem are identified and evaluated experimentally. A new heuristic, connectivity traversal, is found to be fast and to produce high quality layouts.
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    URL: http://dx.doi.org/10.1007/BF02276884
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    Efficient implementation of a 2nd derivative method for stiff ODEs (1994)
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    Computing 53 (1994), S. 95-99 
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    ISSN: 1436-5057
    Keywords: 65F35 ; 65L05 ; 65L07 ; Obrechkoff formula ; stiff differential equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die Padé- oder Obrechkoff-Verfahren, die auf diagonalen oder subdiagonalen Padé-Approximationen der Exponentialfunktion beruhen, vereinen hohe Genauigkeit mit guter Stabilität; wegen des Auftretens höherer Ableitungen sind sie aber nur schwer effizient zu implementieren. Für das subdiagonale Verfahren dritter Ordnung mit zweiten Ableitungen haben wir eine Implementierung gefunden, die zu einem Code geführt hat, der für nicht besonders große, stark steife Systeme bei mäßigen Genauigkeitsforderungen konkurrenzfähig mit gängigen Codes ist.
    Notes: Abstract Padé or Obrechkoff methods based on diagonal or subdiagonal Padé approximations for the exponential function combine high accuracy and good stability; but the occurrence of higher derivatives makes their efficient implementation difficult. For the 3rd order subdiagonal 2nd derivative method, we have found an implementation which has resulted in a competitive code for moderately large, strongly stiff systems, under moderate accuracy requirements.
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    A class of nonmonotone stabilization trust region methods (1994)
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    Computing 53 (1994), S. 119-136 
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    ISSN: 1436-5057
    Keywords: 90C30 ; 65K05 ; Unconstrained optimization ; trust region method ; nonmonotone stabilization method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Für das nichtrestringierte Optimierungsproblem wird eine neue Klasse von Trust-Region-Verfahren vorgestellt, die mit einer nichtmonotonen Stabilisierungsstrategie arbeiten. Die Konvergenzeigenschaften dieser Verfahren werden unter gewissen Regularitätsannahmen untersucht. Umfangreiche numerische Beispiele zeigen die hohe Effizienz dieser Verfahren.
    Notes: Abstract A class of trust region methods in unconstrained optimization is presented, by adopting a nonmonotone stabilization strategy. Under some regularity conditions, the convergence properties of these methods are discussed. Extensive numerical results which are reported show that these methods are very efficient.
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    On the robustness of the dampedV-cycle of the wavelet frequency decomposition multigrid method (1994)
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    Computing 53 (1994), S. 155-171 
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    ISSN: 1436-5057
    Keywords: 65F10 ; 65N30 ; Wavelets ; wavelet packets ; robust multilevel methods ; V-cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir betrachten den gedämpftenV-Zyklus für die Wavelet-Variante der “Frequenzzerlegungs-Multigridmethode” von Hackbusch [Numer. Math.56, 229–245 (1989)]. Es wird gezeigt, daß die Konvergenzgeschwindigkeit bei hinreichender Dämpfung durch Anisotropie nicht beeinflußt wird, aber noch von der Anzahl des Niveaus abhängt. Unsere Analyse beruht auf Eigenschaften von Wavelet-Paketen, die formuliert und bewiesen werden. Numerische Schätzungen der Konvergenzgeschwindigkeit erläutern die theoretischen Ergebnisse.
    Notes: Abstract The dampedV-cycle of the wavelet variation of the “Frequency decomposition multigrid method” of Hackbusch [Numer. Math.56, pp. 229–245 (1989)] is considered. It is shown that the convergence speed under sufficient damping is not affected by the presence of anisotropy but still depends on the number of levels. Our analysis is based on properties of wavelet packets which are supplied and proved. Numerical approximations to the speed of convergence illustrate the theoretical results.
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    Variable order composite quadrature of singular and nearly singular integrals (1994)
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    Computing 53 (1994), S. 173-194 
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    ISSN: 1436-5057
    Keywords: Primary: 65D30, 41A55 ; Secondary: 65D32 ; Singular integrals ; numerical integration ; exponential convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir stellen eine Klasse von zusammengesetzten Quadraturformeln variabler Ordnung vor, die sich zur numerischen Integration von Funktionen mit einer Singularität im Inneren oder in der Nähe des Integrationsbereichs eignen. Für alle Integranden in dem abzählbar normierten RaumB β wird eine exponentielle Konvergenz des Verfahrens bewiesen. Numerische Beispiele zeigen, daß die ermittelten asymptotischen exponentiellen Konvergenzraten scharf sind und schon bei einer kleinen Zahl von Quadraturknoten erreicht werden.
    Notes: Abstract A class of variable order composite quadrature formulas for the numerical integration of functions with a singularity in or near to the region of integration is introduced. Exponential convergence of the method is shown for all integrands in the countably normed spaceB β. Numerical examples are presented which demonstrate that the asymptotic exponential convergence rates obtained here are sharp and already observed for a small number of quadrature points.
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    Editorial (1994)
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    Computing 53 (1994), S. I 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/BF02307373
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    Information frameworks for conceptual engineering design (1994)
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    Engineering with computers 10 (1994), S. 22-32 
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    ISSN: 1435-5663
    Keywords: Conceptual design ; Database ; Frameworks ; Information management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An information modeling approach is used to gain an understanding of the information and decision content of conceptual engineering design. Information frameworks are presented that attempt to represent the key decisions made during conceptual design. Elements of the frameworks are derived from results from design theory and methodology and decision theory. Using a number of products, the frameworks are demonstrated in simulated design situations. The models provide an explicit, generic and consistent perspective for identifying the information content of conceptual designs.
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    Aluminium electrolytic cells: A computer simulator for training and supervision (1994)
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    Engineering with computers 10 (1994), S. 12-21 
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    ISSN: 1435-5663
    Keywords: Aluminium electrolysis ; Expert systems ; Modelling ; Simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A workstation-based simulator of an aluminium electrolytic cell has been constructed. A mathematical model of the cell is integrated with a database and a knowledge base, and the simulator serves as a tool for the training of personnel and for research related to cell dynamics and cell control. When used in conjunction with an expert system, it provides a powerful decision-making tool or an efficient supervisory system. The mathematical model, the simulator itself, the user environment, the interactive simulation procedure as well as examples of the use of the simulator are presented in detail.
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    A review of automatic dimensioning and tolerancing schemes (1994)
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    Engineering with computers 10 (1994), S. 63-80 
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    ISSN: 1435-5663
    Keywords: Dimensioning ; Tolerancing ; Variational geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dimensioning and tolerancing are very important issues in product design and manufacture. This paper gives a survey and review of the current state-of-the-art solutions to the problem of finding a meaning for dimensions and tolerances. Dimensioning and tolerancing in current engineering practices and researches in these topics are also discussed.
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    A new programming paradigm for engineering design software (1994)
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    Engineering with computers 10 (1994), S. 95-111 
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    ISSN: 1435-5663
    Keywords: Engineering design ; Formal ; Functional programming ; Object orientation ; Programming language
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Currently available programming and database systems are insufficient for engineering applications. The authors contend that a logical progression from a formal conceptual model of the engineering domain to a computational model will lead to new programming paradigms capable of directly supporting engineering applications in a rigorous, concise manner. A formal domain model devised by the authors, theHybrid Model (HM) of design information, is briefly introduced. It is an extension of axiomatic set theory and is discussed in detail elsewhere. HM forms the basis ofDesigner, a prototype-based object-oriented programming language supporting a signature-based canonical message-passing mechanism and multiple inheritance. Designer is implemented using the Scheme programming language. Because Designer satisfies a formal conceptual model, and because it is based on a formally specified language, its robustness and logical validity are superior to those of other languages not founded on formal principles. Designer combines concepts of functional and object-oriented programming to provide the formal rigor and flexibility to capture the complex and strongly interrelated information that designers use. Examples demonstrate how Designer represents design information. The results of the authors' research indicate that Designer can capture design information (including aspects of functional requirements and design intent) effectively and efficiently.
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    Rule-based design of a material processing component (1994)
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    Engineering with computers 10 (1994), S. 81-94 
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    ISSN: 1435-5663
    Keywords: Design ; Expert system ; Extension ; Material processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The main thrust of this research is in developing aknowledge-based system for the design of components for a material processing system. In particular, this paper concentrates on developing methodologies forinitial design andredesign in a quantitative and qualitative format. A die for plastic extrusion has been selected as the subject material processing component. A design algorithm using best first heuristic search and expert knowledge, both in procedural and declarative form, is the core of the scheme. Apart from this expert, the suggestedselection procedure for candidate design is also seen to accelerate the design scheme. The methodologies presented enableefficient design of the component. Some generality has been accomplished by the implementation of the techniques to dies of different cross-sectional shapes. The software is written inLisp within an object-oriented software package using analysis modules written in C.
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    Announcement (1994)
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    Engineering with computers 10 (1994), S. 124-124 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    URL: http://dx.doi.org/10.1007/BF01200182
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    A tandem architecture for cooperating knowledge-based concurrent engineering systems (1994)
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    Engineering with computers 10 (1994), S. 112-123 
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    ISSN: 1435-5663
    Keywords: Agent-based framework ; Architecture ; Concurrent engineering ; Cooperating expert systems ; Tandem integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper proposes a tandem architecture for cooperating heterogeneous expert systems. Two levels of meta and working expert systems are involved. The working-level expert systems (W-ES), which may be implemented in their own computational environments and in private proof languages, are mainly for application computations. The meta-level expert systems (M-ES), using a common argument language, are mainly responsible for cooperation. The prototype AGENTS system is described for constructing M-ES. Interaction among W-ES has been transformed into two forms: communication between M-ES through ordinary AGENTS messages and communication between M-ES and the corresponding W-ES using the Deductive Inference Language (DIL). DIL predicates are provided for defining DIL: messages, actuators and converters for interpreting DIL queries and instantiating variables. By this approach, stand-alone capability of infividual systems is retained at the working-level and cooperation is achieved effectively with minimum embellishment at the meta-level.
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    A proposed structure for a rule-based description of parametric forms (1994)
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    Engineering with computers 10 (1994), S. 155-161 
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    ISSN: 1435-5663
    Keywords: Constrains ; Geometric ; Parametric ; Product form
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Much work has been carried out on the creation of protocols for the exchange of data between CAD systems, but very little on the transfer of knowledge. The knowledge behind the development of a product is vital if modifications and adaptations are to be made within a concurrent development environment. Current CAD systems only contain a limited level of product knowledge through user-defined parametric structures. It is the underlying relationships in these programs that need to be communicated between systems, rather than the form of their individual programming languages. A generic structure is proposed that is able to handle both the current level of parametric programming and is suited to the resolution of conflict through the use of constraint modelling procedures. The structure of a parametric description is described and decomposed into its fundamental components. These components are then re-formed within a truth maintenance structure to allow a transfer protocol to be created. The derived protocol structure is then demonstrated on a number of simple examples.
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    Concurrent iterative design and the integration of finite element analysis results (1994)
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    Engineering with computers 10 (1994), S. 245-257 
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    ISSN: 1435-5663
    Keywords: Design methodology ; Iterative design ; Concurrent design ; Features ; Form templates ; Finite element analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract To help foster concurrency in engineering design, methodologies are needed to support the interpretation and abstraction of numerical simulation results for design modification purposes. A methodology is presented in this paper for the integration of continuum-based numerical simulations into a computational system for concurrent design of mechanical components. The technique involves conversion of low-level numerical data, such as that obtained by finite element analysis, into high-level symbolic representations calledform templates. The form templates are based onrudimentary features which carry meaningful qualitative descriptions abstracted from either manufacturing and/or functional numerical simulations. The form templates are superimposed on the design's primary representation in the solid modeler to facilitate the cognitive mapping of concurrent destructive or constructive solid modeling features for design modifications. Examples are presented to demonstrate the methodology.
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    Computers, postmodernism and the culture of the artificial (1994)
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    AI & society 8 (1994), S. 1-16 
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    ISSN: 1435-5655
    Keywords: History of computing ; Data processing ; Artificial intelligence ; Virtual reality ; Modernism ; Postmodernism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The term ‘the artificial’ can only be given a precise meaning in the context of the evolution of computational technology and this in turn can only be fully understood within a cultural setting that includes an epistemological perspective. The argument is illustrated in two case studies from the history of computational machinery: the first calculating machines and the first programmable computers. In the early years of electronic computers, the dominant form of computing was data processing which was a reflection of the dominant philosophy of logical positivism. By contrast, artificial intelligence (AI) adopted an anti-positivist position which left it marginalised until the 1980s when two camps emerged: technical AI which reverted to positivism, and strong AI which reified intelligence. Strong AI's commitment to the computer as a symbol processing machine and its use of models links it to late-modernism. The more directly experiential Virtual Reality (VR) more closely reflects the contemporary cultural climate of postmodernism. It is VR, rather than AI, that is more likely to form the basis of a culture of the artificial.
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    Notes towards a definition of human-centred computing (1994)
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    AI & society 8 (1994), S. 60-70 
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    ISSN: 1435-5655
    Keywords: Computer concepts ; Computer supported collaborative work ; Human-centred computing ; System design methodology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Current usage of the expression “human-centred” in computing contexts suffers from a lack of clarity, and involves internal contradictions. It is not enough to base the concept of human-centredness on ideas of social utility, collaborative working or human controllability. However, the concept of human action (which embodies reference to human freedom) provides a theoretical underpinning to human-centredness by combining, from a human standpoint, concern with process and concern with goals. This has consequences for the design process, prompting us to include new concerns in our system specifications and providing some pointers towards human-centred design methodology.
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    What goes on when a designer thinks? (1994)
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    AI & society 8 (1994), S. 45-59 
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    ISSN: 1435-5655
    Keywords: Computerisation ; Design ; Metaphors ; Tacit knowledge ; Thinking ; Unthinkables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Design can be thought of as a model for such endeavours as are intended to result in industrially manufactured products by means of thinking and other intellectual activity. Familiarity with the thinking involved in the designing process is important, not only for those engaged in training designers, but for anyone desirous of systemizing the endeavour. One procedure for approaching an understanding of the way designers think is to describe it with the help of different metaphors. There are some metaphors for thinking about complicated and interrelated phenomena that should lend themselves to illustrating the thinking involved in design, albeit with reservations — e.g. the difficulty of allowing due consideration for what is unthinkable and indescribable in this context.
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    Information society and cohesion: Diversity or integration? (1994)
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    AI & society 8 (1994), S. 95-96 
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    Introduction to cohesion (1994)
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    AI & society 8 (1994), S. 97-106 
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    The future of European cohesion (1994)
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    AI & society 8 (1994), S. 123-130 
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    ISSN: 1435-5655
    Keywords: Cohesion ; Diversity ; Regional development ; Technology policy ; Integration ; Development ; Scenario
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In its broadest sense, cohesion is an ultimate goal for Europe. In a study about long term future scenarios for Europe it appears that deepening of the integration process may induce decreasing cohesion, unless measures are taken to promote regional diversity as a vector of development. The widening of Europe also raises threats to cohesion, but a well prepared scenario for a Development Belt surrounding the EC may positively enhance the cohesion process.
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    European diversity in science and technology (1994)
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    AI & society 8 (1994), S. 107-122 
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    Keywords: Diversity ; Coherence ; Cohesion ; Network ; Learning ; Local systems of innovation
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    Notes: Abstract A clear understanding of the concept and consequences of diversity in science and technology is a key issue for Europe, when considering the current debate on cohesion Put forward within the Single European Act. According to Article 130B of the Single Act, all European policies, including technological policies must contribute to the achievement of a greater cohesion throughout the EC. The European market is generally presented as mainly a patchwork of national or even regional characteristics, with compartmentalized niches, and specific regulations. But does cohesion mean decreasing disparities between regions, which in such case signifies a passive policy of reallocation of resources within the EC, at the risk of generating uniformity? Or, does cohesion mean integration of all innovative and creative efforts, which implies a more complex policy of stimulation, under the condition to maintain a certain diversity? Must the governments systematically reduce diversity, or on the contrary must they enlarge diversity? How can they distinguish between negative and positive aspects of diversity? How do they operate a trade off between economies of scale and economies of diversity? To try to answer these political issues and to set up a coherent industrial policy at the EC level, a careful analysis of the sources of diversity, of the mechanisms that generate or reduce diversity, of the ways to valorize diversity are discussed in this paper
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    The lack of cohesion as the crucial problem for post-socialist societies (1994)
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    AI & society 8 (1994), S. 151-163 
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    Keywords: Cohesion ; Central and Eastern Europe ; Interdisciplinary approach ; Post-socialist societies ; Transition
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    Notes: Abstract After the collapse of the command structures of the party-state in society and economy, it appeared that the integrative mechanisms as they are developing now in the post-socialist countries have a very limited cohesiveness in the sense that they can not easily support disequilibria and resist disruptions. The asynchronous collapse of old and developing of new integrative mechanisms created integrational vacuums at various levels. The dynamics of this process of conflicting time scales created additional problems of cohesion in each of the domains. It appeared that (dis)integration processes in politics and economics are closely interrelated. Marketization in itself offered enforced fragmentation rather than furthering cohesíon. The link between cohesion within Central and Eastern Europe and Europe at large is also discussed here.
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    The baltic region as an industrial estate: An institutionalist critique (1994)
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    AI & society 8 (1994), S. 164-185 
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    ISSN: 1435-5655
    Keywords: Baltic states ; Bazaar economy ; Flexible specialisation ; Globalisation ; Industrial estates ; Innovation ; Institutionalism ; Interfirm co-operation ; Low policy ; Negotiation ; New institutions ; Regional co-operation ; Relevant social groups ; Routines ; Selection mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This article seeks to explain and conceptualise certain aspects of industrial and technological change at the regional level, using the Baltic region as a case. The concept of “new institutions” is applied to understand recent attempts to stimulate organised behaviour, trustrelations and co-operation at the level of low policy. New regional institutions deal with competing pressure groups, but their strength lies mostly in the ability to orchestrate and influence pressure groups in a formative way. The article identifies potential starting points for this regional involvement. It is divided into three parts. First, some of the economic problems and potentials of the Baltic states are scrutinised. Second, some features of new institutions are explored at the theoretical level. Third, some aspects of international policy-making are briefly discussed, especially the concept of low policies and bottom-up approaches.
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    The prospects of labour-oriented science and research in the nineties (1994)
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    AI & society 8 (1994), S. 197-206 
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    Keywords: Europe ; Labour ; New technologies ; Research ; Science ; Trade unions
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    Notes: Abstract A series of decisions covering agriculture as well as industrial and regional policy fundamentally affect the very own interests of the dependently employed. For some years, the trade unions of all European countries have been on the defensive, undergoing a legitimation crisis. The improvement of the social charter and of the rights of the European Parliament are not sufficient to overcome this crisis and to secure a human, social, ecological and democratic future. For this reason, the order of the day must not only be a socially and ecologically compatible design for technology, but a socially and ecologically oriented one. There is certainly an enormous quantity of accompanying research within the European Community, but it is doubtful in how far this research takes into account the requirements of the majority of the population.
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    What does teamworking mean? — A session report, European conference on the role of research for the social shaping of new technologies (1994)
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    AI & society 8 (1994), S. 270-273 
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    The role of research for the social shaping of new technologies: Designing a research strategy (1994)
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    AI & society 8 (1994), S. 245-269 
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    Keywords: National change programmes ; Participative action research ; Research strategy ; Worklife development ; Workplace reform
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    Notes: Abstract With increasing flexibility of technology and a shift towards competence being the core of competitive edge in worklife, the need for new organizational concepts or models which givejoint optimization across human and technological dimensions has been acknowledged in leading, innovative enterprises. National crossdisciplinary research based productivity programmes are appearing in several countries. Due to internationalization and the general shortcomings of bureaucratic organizational forms, regional networks of enterprises in cooperation with public R&D institutions seem to provide answers to needs of regions to remain competitive. The paper discusses the possible role of social science in a multilevel, participative strategy for developing new, democratic and productive organizational forms in worklife. Aspects of national productivity programmes in Scandinavia, Germany and Australia are discussed in connection with the situation in Italy as analyzed through some recent research projects.
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    Managerial innovations: Some main tendencies (1994)
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    AI & society 8 (1994), S. 285-291 
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    Difficulties and potentialities of group work (1994)
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    AI & society 8 (1994), S. 298-303 
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    Notes: Conclusions As my paper draws to a close, it may seem quite clear that by posing such questions about the organisation of work and labour, one opens up more problems than are actually solved. There is one question in particular that has to be answered. I shall ask that question rhetorically: Can there be a world in which group activities are not started up?
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    Some consequences of current scientific treatments of consciousness and selfhood (1994)
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    AI & society 8 (1994), S. 305-314 
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    Keywords: Consciousness ; Selfhood ; Science of Mind
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    Notes: Abstract For a variety of reasons, consciousness and selfhood are beginning once again to be intensively studied in a scientific frame of reference. The notions of each which are emerging are extremely varied: in the case of selfhood, the lack of an adequate vocabulary to capture various aspects of subjectivity has led to deep confusion. The task of the first part of this article is to clear up this terminological confusion, while salvaging whatever is valuable from the contemporary discussion. The more important task of the second part is to discuss the moral issues inevitably involved in any treatment, scientific or otherwise, of the modern identity.
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    Characterising Artificial Intelligence technology for international transfer (1994)
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    AI & society 8 (1994), S. 315-325 
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    Keywords: Artificial intelligence technology ; International technology transfer
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    Notes: Abstract One of the central factors influencing the process and the outcome of technology transfer is the nature of the technology being transferred. This paper identifies and discusses the main characteristics of Artificial Intelligence (AI) technology from the point of view of international technology transfer. It attempts to indicate the peculiarities of AI in this context and move towards a framework to assist recipient decision makers in optimising the formulation of their policies on AI technology transfer. The five AI characteristics identified here relate to complexity, localisation, uncertainty, capital intensiveness and awareness. Some of these features are in principle common with other high technologies, but still bear some aspects specific to AI, albeit only the intensity with which they characterise the technology. The complexity of AI technology partially stems from its multi-disciplinary nature. Certain sub-areas of AI are locally bound and therefore need local innovative capabilities to develop on the fundamental concepts. The uncertainty in AI projects stems mainly from the two factors of high rate of change and the difficulties of quantifying the gains of transferring cognitive load from human to machine. Expensive human skill and enabling technologies are required to develop, maintain and use AI systems efficiently, making such projects highly capital intensive. Finally, AI is a young field and is not always completely open about itself which makes the decision makers' awareness an important issue to be addressed in the growth of AI applications.
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    Implications of a logical paradox for computer-dispensed justice (1994)
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    AI & society 8 (1994), S. 357-359 
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    Intelligent systems at home in 2000 (1994)
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    AI & society 8 (1994), S. 359-363 
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    Knowledge discovery and system-user partnership: On a production “adversarial partnership” approach (1994)
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    AI & society 8 (1994), S. 341-356 
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    Keywords: Knowledge discovery ; Database mining ; User intention ; Database security ; “Adversarial partnership”
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    Notes: Abstract We examine the relationship between systems and their users from the knowledge discovery perspective. Recently knowledge discovery in databases has made important progress, but it may also bring some potential problems to database design, such as issues related to database security, because an unauthorised user may derive highly sensitive knowledge from unclassified data. In this paper we point out that there is a need for a comprehensive study on knowledge discovery in human-computer symbiosis. Borrowing terms from algorithm design and artificial intelligence literature, we propose a notion called database-user adversarial partnership. We point out that this notion is general enough to cover various knowledge discovery and security of issues related to databases and their users. Furthermore, we point out the notion of database-user adversarial partnership can be further generalised into system-user adversarial partnership. Opportunities provided by knowledge discovery techniques and potential social implications are also discussed.
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    A technique for speeding up the solution of the Lagrangean dual (1994)
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    Mathematical programming 63 (1994), S. 23-45 
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    Keywords: Lagrangean relaxation ; linear programming relaxation ; polynomial algorithm
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    Topics: Computer Science , Mathematics
    Notes: Abstract We propose techniques for the solution of the LP relaxation and the Lagrangean dual in combinatorial optimization and nonlinear programming problems. Our techniques find the optimal solution value and the optimal dual multipliers of the LP relaxation and the Lagrangean dual in polynomial time using as a subroutine either the Ellipsoid algorithm or the recent algorithm of Vaidya. Moreover, in problems of a certain structure our techniques find not only the optimal solution value, but the solution as well. Our techniques lead to significant improvements in the theoretical running time compared with previously known methods (interior point methods, Ellipsoid algorithm, Vaidya's algorithm). We use our method to the solution of the LP relaxation and the Langrangean dual of several classical combinatorial problems, like the traveling salesman problem, the vehicle routing problem, the Steiner tree problem, thek-connected problem, multicommodity flows, network design problems, network flow problems with side constraints, facility location problems,K-polymatroid intersection, multiple item capacitated lot sizing problem, and stochastic programming. In all these problems our techniques significantly improve the theoretical running time and yield the fastest way to solve them.
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    Representations of quasi-Newton matrices and their use in limited memory methods (1994)
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    Mathematical programming 63 (1994), S. 129-156 
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    Keywords: Quasi-Newton method ; constrained optimization ; limited memory method ; large-scale optimization
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    Notes: Abstract We derive compact representations of BFGS and symmetric rank-one matrices for optimization. These representations allow us to efficiently implement limited memory methods for large constrained optimization problems. In particular, we discuss how to compute projections of limited memory matrices onto subspaces. We also present a compact representation of the matrices generated by Broyden's update for solving systems of nonlinear equations.
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    Global minimization by reducing the duality gap (1994)
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    Mathematical programming 63 (1994), S. 193-212 
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    Keywords: Global optimization ; nonconvex programming ; duality gap ; branch and bound method ; decomposition ; nonsmooth optimization ; pooling problem
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    Topics: Computer Science , Mathematics
    Notes: Abstract We derive a general principle demonstrating that by partitioning the feasible set, the duality gap, existing between a nonconvex program and its lagrangian dual, can be reduced, and in important special cases, even eliminated. The principle can be implemented in a Branch and Bound algorithm which computes an approximate global solution and a corresponding lower bound on the global optimal value. The algorithm involves decomposition and a nonsmooth local search. Numerical results for applying the algorithm to the pooling problem in oil refineries are given.
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    Call for nominations: The 1993 Lanchester Prize (1994)
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    Mathematical programming 63 (1994), S. 255-256 
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    Topics: Computer Science , Mathematics
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    A new pivoting algorithm for the linear complementarity problem allowing for an arbitrary starting point (1994)
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    Mathematical programming 63 (1994), S. 235-252 
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    Keywords: Linear complementarity problem ; pivoting algorithm ; stationary point problem
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    Notes: Abstract The linear complementarity problem is to find nonnegative vectors which are affinely related and complementary. In this paper we propose a new complementary pivoting algorithm for solving the linear complementarity problem as a more efficient alternative to the algorithms proposed by Lemke and by Talman and Van der Heyden. The algorithm can start at an arbitrary nonnegative vector and converges under the same conditions as Lemke's algorithm.
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    The pin redistribution problem in multi-chip modules (1994)
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    Mathematical programming 63 (1994), S. 297-330 
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    Notes: Abstract We introduce thepin redistribution problem (PRP), which arises from layout design ofmulti-chip modules. The problem is to redistribute the pins uniformly over the MCM substrate using a number of pin redistribution layers. Pin redistribution is very important in MCM design because it has been used to not only provide a minimum spacing between signal wires in dense signal distribution layers, but also provide engineering change capability [3, 4]. Moreover, our experience [10] showed that the capacitive coupling noise between vias (one of the major problems in designing MCMs) induced by many layers (up to 63 layers) can be reduced using the pin redistribution technique. The goal of the problem is to minimize the number of layers required to redistribute the entire set. As a net is undefined, a number of challenging issues arise. Three effective approaches are proposed for solving this problem.
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    Optimal mapping in direct mapped cache environments (1994)
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    Mathematical programming 63 (1994), S. 371-387 
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    Notes: Abstract In this paper we study positioning strategies for improving the performance of a memory system with a direct mapped cache. A positioning technique determines for every program item, (instruction or data), its address in main memory. Assuming the Independent Reference Model, we break the general positioning problem into two, the collision minimization and the grouping problems and show optimal algorithms for both problems. Using these algorithms we derive an optimal algorithm for the general positioning problem. Since the optimal positioning is of very special structure we consider other, less restricted, positionings. We show that the quality of a class of natural assignments that distribute the items almost arbitrarily is good as long as the optimal hit ratio is sufficiently large. Another possible requirement is that the items should be distributed as evenly as possible. We find an optimal assignment for the special case of the pair assignment. In addition we look at the expected performance gain of two frequently suggested cache features. The cache bypass feature supports the access of items in memory without loading the item into the cache. We show an assignment with best possible hit ratio. Also it is shown that a cache which employs a random assignment policy, i.e., the assignment of an item is determined randomly, does not improve the expected hit ratio.
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    Random walks, totally unimodular matrices, and a randomised dual simplex algorithm (1994)
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    Mathematical programming 64 (1994), S. 1-16 
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    Keywords: Random walks ; Totally unimodular matrices ; Uniform generation ; Linear programming ; Diameter of polytopes
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    Topics: Computer Science , Mathematics
    Notes: Abstract We discuss the application of random walks to generating a random basis of a totally unimodular matrix and to solving a linear program with such a constraint matrix. We also derive polynomial upper bounds on the combinatorial diameter of an associated polyhedron.
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    A strategy for array management in local memory (1994)
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    Mathematical programming 63 (1994), S. 331-370 
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    Notes: Abstract One major point in loop restructuring for data locality optimization is the choice and the evaluation of data locality criteria. In this paper we show how to compute approximations of window sets defined by Gannon, Jalby, and Gallivan. The window associated with an iterationi describes the “active” portion of an array: elements that have already been referenced before iterationi and that will be referenced after iterationi. Such a notion is extremely useful for data localization because it identifies the portions of arrays that are worth keeping in local memory because they are going to be referenced later. The computation of these window approximations can be performed symbolically at compile time and generates a simple geometrical shape that simplifies the management of the data transfers. This strategy allows derivation of a global strategy of data management for local memories which may be combined efficiently with various parallelization and/or vectorization optimizations. Indeed, the effects of loop transformations fit naturally into the geometrical framework we use for the calculations. The determination of window approximations is studied both from a theoretical and a computational point of view, and examples of applications are given.
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    Dynamic factorization in large-scale optimization (1994)
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    Mathematical programming 64 (1994), S. 17-51 
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    Keywords: Factorization ; Linear programming ; Generalized upper bounds ; Pure networks ; Generalized networks
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    Topics: Computer Science , Mathematics
    Notes: Abstract Factorization of linear programming (LP) models enables a large portion of the LP tableau to be represented implicitly and generated from the remaining explicit part. Dynamic factorization admits algebraic elements which change in dimension during the course of solution. A unifying mathematical framework for dynamic row factorization is presented with three algorithms which derive from different LP model row structures: generalized upper bound rows, pure network rows, and generalized network rows. Each of these structures is a generalization of its predecessors, and each corresponding algorithm exhibits just enough additional richness to accommodate the structure at hand within the unified framework. Implementation and computational results are presented for a variety of real-world models. These results suggest that each of these algorithms is superior to the traditional, non-factorized approach, with the degree of improvement depending upon the size and quality of the row factorization identified.
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    A class of gap functions for variational inequalities (1994)
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    Mathematical programming 64 (1994), S. 53-79 
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    Keywords: Finite-dimensional variational inequalities ; Merit functions ; Variational principles ; Successive approximation algorithms ; Descent algorithms
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    Topics: Computer Science , Mathematics
    Notes: Abstract Recently Auchmuty (1989) has introduced a new class of merit functions, or optimization formulations, for variational inequalities in finite-dimensional space. We develop and generalize Auchmuty's results, and relate his class of merit functions to other works done in this field. Especially, we investigate differentiability and convexity properties, and present characterizations of the set of solutions to variational inequalities. We then present new descent algorithms for variational inequalities within this framework, including approximate solutions of the direction finding and line search problems. The new class of merit functions include the primal and dual gap functions, introduced by Zuhovickii et al. (1969a, 1969b), and the differentiable merit function recently presented by Fukushima (1992); also, the descent algorithm proposed by Fukushima is a special case from the class of descent methods developed in this paper. Through a generalization of Auchmuty's class of merit functions we extend those inherent in the works of Dafermos (1983), Cohen (1988) and Wu et al. (1991); new algorithmic equivalence results, relating these algorithm classes to each other and to Auchmuty's framework, are also given.
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    The P-matrix problem is co-NP-complete (1994)
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    Mathematical programming 64 (1994), S. 173-178 
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    Keywords: P-matrix ; Linear complementarity problem ; Interval matrix ; NP-complete
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    Notes: Abstract Recently Rohn and Poljak proved that for interval matrices with rank-one radius matrices testing singularity is NP-complete. This paper will show that given any matrix family belonging to the class of matrix polytopes with hypercube domains and rank-one perturbation matrices, a class which contains the interval matrices, testing singularity reduces to testing whether a certain matrix is not a P-matrix. It follows from this result that the problem of testing whether a given matrix is a P-matrix is co-NP-complete.
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    The Steiner tree problem II: Properties and classes of facets (1994)
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    Mathematical programming 64 (1994), S. 231-246 
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    Keywords: Steiner tree ; Polyhedron ; Facets
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    Notes: Abstract This is the second part of two papers addressing the study of the facial structure of the Steiner tree polyhedron. In this paper we identify several classes of facet defining inequalities and relate them to special classes of graphs on which the Steiner tree problem is known to be NP-hard.
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    Duality in disjunctive programming via vector optimization (1994)
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    Mathematical programming 65 (1994), S. 21-41 
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    Keywords: Duality in nonlinear programming ; Family of linear programs ; Disjunctive programming ; Vector optimization
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In this paper, we develop a new duality theory for families of linear programs with an emphasis on disjunctive linear optimization by proposing a ‘vector’ optimization problem as dual problem. We establish that the well-known relations between primal and dual problems hold in this context. We show that our method generalizes the duality results of Borwein on families of linear programs, of Balas on disjunctive programs, and of Patkar and Stancu-Minasian on disjunctive linear fractional programs. Moreover, we can derive some duality results for integer and for fractional programs where the denominator is not assumed (as usual) to be greater than zero for each feasible point.
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    Solving cone-constrained convex programs by differential inclusions (1994)
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    Mathematical programming 65 (1994), S. 107-121 
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    ISSN: 1436-4646
    Keywords: Primary: 90C25, 90C48 ; secondary: 34A60, 90C15 ; Convex program ; Cone constraint ; Isotone projections ; Saddle point ; Differential inclusion ; Stochastic programming
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A differential inclusion is designed for solving cone-constrained convex programs. The method is of subgradient-projection type. It involves projection, penalties and Lagrangian relaxation. Nonsmooth data can be accommodated. A novelty is that multipliers converge monotonically upwards to equilibrium levels. An application to stochastic programming is considered.
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    A separation algorithm for the matchable set polytope (1994)
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    Mathematical programming 65 (1994), S. 139-150 
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    ISSN: 1436-4646
    Keywords: Combinatorial optimization ; Polyhedra ; Matching ; Matchable set ; Separation algorithm ; Augmenting path
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A matchable set of a graph is a set of vertices joined in pairs by disjoint edges. Balas and Pulleyblank gave a linear-inequality description of the convex hull of matchable sets. We give a polynomial-time combinatorial algorithm for the separation problem for this polytope, and a min—max theorem characterizing the maximum violation by a given point of an inequality of the system.
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    Interior-point algorithms for semi-infinite programming (1994)
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    Mathematical programming 65 (1994), S. 217-245 
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    ISSN: 1436-4646
    Keywords: Linear programming ; Semi-infinite programming ; Interior-point methods
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    Topics: Computer Science , Mathematics
    Notes: Abstract In order to study the behavior of interior-point methods on very large-scale linear programming problems, we consider the application of such methods to continuous semi-infinite linear programming problems in both primal and dual form. By considering different discretizations of such problems we are led to a certain invariance property for (finite-dimensional) interior-point methods. We find that while many methods are invariant, several, including all those with the currently best complexity bound, are not. We then devise natural extensions of invariant methods to the semi-infinite case. Our motivation comes from our belief that for a method to work well on large-scale linear programming problems, it should be effective on fine discretizations of a semi-infinite problem and it should have a natural extension to the limiting semi-infinite case.
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    Formulation of linear problems and solution by a universal machine (1994)
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    Mathematical programming 65 (1994), S. 263-309 
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    ISSN: 1436-4646
    Keywords: Linear ; Problems ; Universal ; Machines ; Predicate ; Logic ; Turing ; Complexity
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    Topics: Computer Science , Mathematics
    Notes: Abstract Using the predicate language for ordered fields a class of problems referred to aslinear problems is defined. This class contains, for example, all systems of linear equations and inequalities, all linear programming problems, all integer programming problems with bounded variables, all linear complementarity problems, the testing of whether sets that are defined by linear inequalities are semilattices, all satisfiability problems in sentenial logic, the rank-computation of matrices, the computation of row-reduced echelon forms of matrices, and all quadratic programming problems with bounded variables. A single, one, algorithm, to which we refer as theUniversal Linear Machine, is described. It solves any instance of any linear problem. The Universal Linear Machine runs in two phases. Given a linear problem, in the first phase a Compiler running on a Turing Machine generates alinear algorithm for the problem. Then, given an instance of the linear problem, in the second phase the linear algorithm solves the particular instance of the linear problem. The linear algorithm is finite, deterministic, loopless and executes only the five ordered field operations — additions, multiplications, subtractions, divisions and comparisons. Conversely, we show that for each linear algorithm there is a linear problem which the linear algorithm solves uniquely. Finally, it is shown that with a linear algorithm for a linear problem, one can solve certain parametric instances of the linear problem.
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    A two-stage successive overrelaxation algorithm for solving the symmetric linear complementarity problem (1994)
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    Mathematical programming 65 (1994), S. 365-380 
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    Keywords: SOR ; Symmetric linear complementarity problem ; Large-scale programming
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    Notes: Abstract We propose a two-stage successive overrelaxation method (TSOR) algorithm for solving the symmetric linear complementarity problem. After the first SOR preprocessing stage this algorithm concentrates on updating a certain prescribed subset of variables which is determined by exploiting the complementarity property. We demonstrate that this algorithm successfully solves problems with up to ten thousand variables.
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    A trust region algorithm for minimization of locally Lipschitzian functions (1994)
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    Mathematical programming 66 (1994), S. 25-43 
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    ISSN: 1436-4646
    Keywords: Trust region methods ; Locally Lipschitzian functions ; Global convergence
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    Topics: Computer Science , Mathematics
    Notes: Abstract The classical trust region algorithm for smooth nonlinear programs is extended to the nonsmooth case where the objective function is only locally Lipschitzian. At each iteration, an objective function that carries both first and second order information is minimized over a trust region. The term that carries the first order information is an iteration function that may not explicitly depend on subgradients or directional derivatives. We prove that the algorithm is globally convergent. This convergence result extends the result of Powell for minimization of smooth functions, the result of Yuan for minimization of composite convex functions, and the result of Dennis, Li and Tapia for minimization of regular functions. In addition, compared with the recent model of Pang, Han and Rangaraj for minimization of locally Lipschitzian functions using a line search, this algorithm has the same convergence property without assuming positive definiteness and uniform boundedness of the second order term. Applications of the algorithm to various nonsmooth optimization problems are discussed.
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    The maximum entropy method on the mean: Applications to linear programming and superresolution (1994)
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    Mathematical programming 66 (1994), S. 103-122 
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    Keywords: 42B05 ; 62A99 ; Maximum entropy ; Linear programming ; Inverse problems ; Superresolution
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    Notes: Abstract In this paper, we give two different results. We propose new methods to solve classical optimization problems in linear programming. We also obtain precise quantitative results for the superresolution phenomenon, as observed earlier by practical searchers on specific algorithms. The common background of our work is the generalized moment problem, which is known to be connected with linear programming and superresolution. We describe the Maximum Entropy Method on the Mean that provides solution to the problem and leads to computational criteria to decide the existence of solutions or not.
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    A distance constrainedp-facility location problem on the real line (1994)
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    Mathematical programming 66 (1994), S. 201-204 
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    Keywords: Location theory ; p-center problems ; Minimum cut problems
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    Notes: Abstract LetV = {v 1,⋯, v n } be a set ofn points on the real line (existing facilities). The problem considered is to locatep new point facilities,F 1,⋯, F p , inV while satisfying distance constraints between pairs of existing and new facilities and between pairs of new facilities. Fori = 1, ⋯, p, j = 1, ⋯, n, the cost of locatingF i at pointv j isc ij . The objective is to minimize the total cost of setting up the new facilities. We present anO(p 3 n 2 logn) algorithm to solve the model.
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    New improved error bounds for the linear complementarity problem (1994)
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    Mathematical programming 66 (1994), S. 241-255 
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    ISSN: 1436-4646
    Keywords: Linear complementarity ; Error bounds
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    Notes: Abstract New local and global error bounds are given for both nonmonotone and monotone linear complementarity problems. Comparisons of various residuals used in these error bounds are given. A possible candidate for a “best” error bound emerges from our comparisons as the sum of two natural residuals.
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    Characterizing consistency in probabilistic logic for a class of Horn clauses (1994)
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    Mathematical programming 66 (1994), S. 257-271 
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    ISSN: 1436-4646
    Keywords: Consistency ; Probabilistic logic ; Perfect graph
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    Notes: Abstract The problem of consistently assigning probabilities to logical formulas is an important problem. In this paper a set of logical formulas will be identified for which the problem can be solved. For every directed graph we define a set of logical formulas that it represents. If the underlying (undirected) graph is either perfect or t-perfect a closed form solution to the consistency problem can be given. A remarkable property of the class of formulas identified here is that it turns out to be closed under duality (if a set of formulas is represented by a digraph then the dual set of formulas is also represented by a digraph).
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    Stability for linearly constrained optimization problems (1994)
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    Mathematical programming 66 (1994), S. 351-360 
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    Keywords: Stationary solution ; Weakly stable ; Pseudo-weakly stable ; Linear constraints
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    Notes: Abstract We deal with finite dimensional differentiable optimization problems under linear constraints. Stability of stationary solutions under restricted perturbations of the constraints will be characterized. The restriction on the constraint perturbations is given by means of a certain rank condition; in particular, righthandside perturbations are allowed.
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    Superlinear convergence of infeasible-interior-point methods for linear programming (1994)
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    Mathematical programming 66 (1994), S. 361-377 
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    ISSN: 1436-4646
    Keywords: Linear programming ; Infeasible-interior-point methods ; Superlinear convergence
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    Notes: Abstract At present the interior-point methods of choice are primal—dual infeasible-interior-point methods, where the iterates are kept positive, but allowed to be infeasible. In practice, these methods have demonstrated superior computational performance. From a theoretical point of view, however, they have not been as thoroughly studied as their counterparts — feasible-interior-point methods, where the iterates are required to be strictly feasible. Recently, Kojima et al., Zhang, Mizuno and Potra studied the global convergence of algorithms in the primal—dual infeasible-interior-point framework. In this paper, we continue to study this framework, and in particular we study the local convergence properties of algorithms in this framework. We construct parameter selections that lead toQ-superlinear convergence for a merit function andR-superlinear convergence for the iteration sequence, both at rate 1 +τ whereτ can be arbitrarily close to one.
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    Finite master programs in regularized stochastic decomposition (1994)
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    Mathematical programming 67 (1994), S. 143-168 
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    Keywords: Stochastic programming ; Decomposition ; Cutting plane methods
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    Notes: Abstract Stochastic decomposition is a stochastic analog of Benders' decomposition in which randomly generated observations of random variables are used to construct statistical estimates of supports of the objective function. In contrast to deterministic Benders' decomposition for two stage stochastic programs, the stochastic version requires infinitely many inequalities to ensure convergence. We show that asymptotic optimality can be achieved with a finite master program provided that a quadratic regularizing term is included. Our computational results suggest that the elimination of the cutting planes impacts neither the number of iterations required nor the statistical properties of the terminal solution.
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    Polyhedra for lot-sizing with Wagner—Whitin costs (1994)
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    Mathematical programming 67 (1994), S. 297-323 
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    Keywords: Lot-sizing models ; Polyhedral combinatorics
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    Notes: Abstract We examine the single-item lot-sizing problem with Wagner—Whitin costs over ann period horizon, i.e.p t+ht⩾pt+1 fort = 1, ⋯,n−1, wherep t, ht are the unit production and storage costs in periodt respectively, so it always pays to produce as late as possible. We describe integral polyhedra whose solution as linear programs solve the uncapacitated problem (ULS), the uncapacitated problem with backlogging (BLS), the uncapacitated problem with startup costs (ULSS) and the constant capacity problem (CLS), respectively. The polyhedra, extended formulations and separation algorithms are much simpler than in the general cost case. In particular for models ULS and ULSS the polyhedra in the original space have only O(n 2) facets as opposed to O(2 n ) in the general case. For CLS and BLS no explicit polyhedral descriptions are known for the general case in the original space. Here we exhibit polyhedra with O(2 n ) facets having an O(n 2 logn) separation algorithm for CLS and O(n 3) for BLS, as well as extended formulations with O(n 2) constraints in both cases, O(n 2) variables for CLS and O(n) variables for BLS.
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    Bounded knapsack sharing (1994)
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    Mathematical programming 67 (1994), S. 343-382 
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    ISSN: 1436-4646
    Keywords: Maximin programming ; Knapsack sharing problems ; Lower and upper bounds
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    Notes: Abstract A bounded knapsack sharing problem is a maximin or minimax mathematical programming problem with one or more linear inequality constraints, an objective function composed of single variable continuous functions called tradeoff functions, and lower and upper bounds on the variables. A single constraint problem which can have negative or positive constraint coefficients and any type of continuous tradeoff functions (including multi-modal, multiple-valued and staircase functions) is considered first. Limiting conditions where the optimal value of a variable may be plus or minus infinity are explicitly considered. A preprocessor procedure to transform any single constraint problem to a finite form problem (an optimal feasible solution exists with finite variable values) is developed. Optimality conditions and three algorithms are then developed for the finite form problem. For piecewise linear tradeoff functions, the preprocessor and algorithms are polynomially bounded. The preprocessor is then modified to handle bounded knapsack sharing problems with multiple constraints. An optimality condition and algorithm is developed for the multiple constraint finite form problem. For multiple constraints, the time needed for the multiple constraint finite form algorithm is the time needed to solve a single constraint finite form problem multiplied by the number of constraints. Some multiple constraint problems cannot be transformed to multiple constraint finite form problems.
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    On the use of an inverse shortest paths algorithm for recovering linearly correlated costs (1994)
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    Mathematical programming 63 (1994), S. 1-22 
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    Keywords: Graph theory ; shortest paths ; inverse problems ; quadratic programming ; traffic modelling
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    Notes: Abstract This paper considers the inverse shortest paths problem where arc costs are subject to correlation constraints. The motivation for this research arises from applications in traffic modelling and seismic tomography. A new method is proposed for solving this class of problems. It is constructed as a generalization of the algorithm presented in Burton and Toint (Mathematical Programming 53, 1992) for uncorrelated inverse shortest paths. Preliminary numerical experience with the new method is presented and discussed.
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    Call for papers (1994)
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    Mathematical programming 63 (1994), S. 127-127 
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    Topics: Computer Science , Mathematics
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    Efficient enumeration of the vertices of polyhedra associated with network LP's (1994)
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    Mathematical programming 63 (1994), S. 47-64 
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    Keywords: Enumeration ; generation ; listing ; vertex ; polyhedron ; network
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    Notes: Abstract Algorithms are given to list the vertices of polyhedra associated with network linear programs and their duals. Each algorithm has running time which is quadratic in the number of vertices of the polyhedron, and does not require that the polyhedron be either bounded or simple. The algorithms use characterizations of adjacent vertices in network and dual network LP's to perform an efficient traversal of the edge graph of the polyhedron. This contrasts with algorithms for enumerating the vertices of a general polyhedron, all of which have worst-case complexity which is exponential in the number of vertices of the polyhedron.
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    Inexact subgradient methods with applications in stochastic programming (1994)
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    Mathematical programming 63 (1994), S. 65-82 
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    Keywords: Subgradient methods ; Approximations ; stochastic optimization
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    Notes: Abstract In many instances, the exact evaluation of an objective function and its subgradients can be computationally demanding. By way of example, we cite problems that arise within the context of stochastic optimization, where the objective function is typically defined via multi-dimensional integration. In this paper, we address the solution of such optimization problems by exploring the use of successive approximation schemes within subgradient optimization methods. We refer to this new class of methods as inexact subgradient algorithms. With relatively mild conditions imposed on the approximations, we show that the inexact subgradient algorithms inherit properties associated with their traditional (i.e., exact) counterparts. Within the context of stochastic optimization, the conditions that we impose allow a relaxation of requirements traditionally imposed on steplengths in stochastic quasi-gradient methods. Additionally, we study methods in which steplengths may be defined adaptively, in a manner that reflects the improvement in the objective function approximations as the iterations proceed. We illustrate the applicability of our approach by proposing an inexact subgradient optimization method for the solution of stochastic linear programs.
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    Tree polytope on 2-trees (1994)
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    Mathematical programming 63 (1994), S. 183-191 
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    Keywords: Polyhedral characterization ; Steiner problem
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    Notes: Abstract We give a complete polyhedral characterization of the tree polytope (convex hull of the characteristic vectors of trees in the graph) on 2-trees.
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    Call for nominations for 1994 elections (1994)
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    Mathematical programming 63 (1994), S. 253-253 
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    Preface (1994)
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    Mathematical programming 63 (1994), S. iii 
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    Quadratic 0/1 optimization and a decomposition approach for the placement of electronic circuits (1994)
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    Mathematical programming 63 (1994), S. 257-279 
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    Keywords: Quadratic 0/1 optimization ; computational complexity ; VLSI-design
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    Topics: Computer Science , Mathematics
    Notes: Abstract The placement problem in the layout design of electronic circuits consists of finding a nonoverlapping assignment of rectangular cells to positions on the chip so that wireability is guaranteed and certain technical constraints are met. This problem can be modelled as a quadratic 0/1-program subject to linear constraints. We will present a decomposition approach to the placement problem and give results above NP-hardness and the existence ofε-approximative algorithms for the involved optimization problems. A graph theoretic formulation of these problems will enable us to develop approximative algorithms. Finally we will present details of the implementation of our approach and compare it to industrial state of the art placement routines.
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    A globally convergent primal—dual interior point algorithm for convex programming (1994)
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    Mathematical programming 64 (1994), S. 123-147 
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    Keywords: Primary 90C25 ; Secondary 49D45, 65K05 ; Interior-point methods ; Convex programming ; Karmarkar's algorithm ; Global convergence ; Potential function ; Potential reduction algorithms ; Armijo stepsize rule
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In this paper, we study the global convergence of a large class of primal—dual interior point algorithms for solving the linearly constrained convex programming problem. The algorithms in this class decrease the value of a primal—dual potential function and hence belong to the class of so-called potential reduction algorithms. An inexact line search based on Armijo stepsize rule is used to compute the stepsize. The directions used by the algorithms are the same as the ones used in primal—dual path following and potential reduction algorithms and a very mild condition on the choice of the “centering parameter” is assumed. The algorithms always keep primal and dual feasibility and, in contrast to the polynomial potential reduction algorithms, they do not need to drive the value of the potential function towards — ∞ in order to converge. One of the techniques used in the convergence analysis of these algorithms has its root in nonlinear unconstrained optimization theory.
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    A row-action method for convex programming (1994)
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    Mathematical programming 64 (1994), S. 149-171 
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    Keywords: 90C25 ; 90C30 ; Convex programming ; Row-action methods ; Iterative algorithms
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    Notes: Abstract We present a new method for minimizing a strictly convex function subject to general convex constraints. Constraints are used one at a time, no changes are made in the constraint functions (thus the row-action nature of the algorithm) and at each iteration a subproblem is solved consisting of minimization of the objective function subject to one or two linear equations. Convergence of the algorithm is established and the method is compared with other row-action algorithms for several relevant particular cases.
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    Two-edge connected spanning subgraphs and polyhedra (1994)
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    Mathematical programming 64 (1994), S. 199-208 
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    Keywords: Two-edge connected graphs ; Polyhedra ; Facets ; Series—parallel graphs
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    Notes: Abstract This paper studies the problem of finding a two-edge connected spanning subgraph of minimum weight. This problem is closely related to the widely studied traveling salesman problem and has applications to the design of reliable communication and transportation networks. We discuss the polytope associated with the solutions to this problem. We show that when the graph is series-parallel, the polytope is completely described by the trivial constraints and the so-called cut constraints. We also give some classes of facet defining inequalities of this polytope when the graph is general.
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    The Steiner tree problem I: Formulations, compositions and extension of facets (1994)
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    Mathematical programming 64 (1994), S. 209-229 
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    ISSN: 1436-4646
    Keywords: Steiner tree ; Polyhedron ; Facets ; Projection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we give some integer programming formulations for the Steiner tree problem on undirected and directed graphs and study the associated polyhedra. We give some families of facets for the undirected case along with some compositions and extensions. We also give a projection that relates the Steiner tree polyhedron on an undirected graph to the polyhedron for the corresponding directed graph. This is used to show that the LP-relaxation of the directed formulation is superior to the LP-relaxation of the undirected one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01582573
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