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  • Computer Science  (174,576)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
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  • 2
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    Expert systems 1 (1984), S. 0 
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  • 3
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    Expert systems 1 (1984), S. 0 
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  • 4
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 5
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 6
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 7
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: Abstract: This paper considers an application of decision aiding for maritime operations, viz the design of an intelligent operator aid for dynamic route planning. The limitations of some existing methods are discussed and an Al approach is proposed that combines algorithmic and heuristic processing elements within an embedded system. The aid consists of three elements: a intelligent front end, a route planner and an explanation facility.
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  • 8
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: Abstract: Recent developments in a subarea of computer science called artificial intelligence have included the creation of expert systems that are capable of solving difficult applications problems which require expert knowledge for their solution. Such expert systems have been found to be useful in a number of applications (e.g. medicine, biochemistry and mineral exploration). In this paper the author presents an expert system for solving problems concerning income and transfer tax planning for individuals In developing this system, a theoretical structure and a set of decision rules were specified and then programmed into a rule-based system that had previously been used for medical diagnosis (Mycin [1]) Once the system was developed, its problem-solving capabilities were refined and verified by a panel of tax experts using a blind verification procedure. This verification step demonstrated that an expert system could be developed in that domain.
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  • 9
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 10
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: Abstract: The purpose of this paper is to design an expert system or an intelligent procedure' that purports to screen hazard potentials of environmental chemicals on the basis of structure-activity relationships in the study of chemical carcinogenesis, particularly with respect to analysing the current state of known structural information about chemical carcinogens and predicting the possible carcinogenicity of untested chemicals An analysis of a computerised database of known carcinogens (knowledge base) is being performed using the structure-activity trees in order to test the validity of the tree as a classification scheme (inference engine) and to evaluate trends or patterns that may exist between chemical structure and specificity for target tissue, route of administration, and animal species. Practical applications of the structure-activity tree depend on its eventual validation as a predictor of carcinogenic activity.
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  • 11
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 12
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 13
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    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: Abstract: Activities concerning expert systems in Japan are outlined. Expert systems are receiving increasing attention in Japan, together with fifth-generation computers. Rather than describing the details of individual systems, a variety of expert systems are briefly introduced with their aims and features.
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  • 14
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
    ISSN: 1468-0394
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: Abstract: Analysis of the job shop scheduling domain has indicated that the crux of the scheduling problem is the determination and satisfaction of a large variety of constraints. Schedules are influenced by such diverse and conflicting factors as due date requirements, cost restrictions, production levels, machine capabilities and substitutability, alternative production processes, order characteristics, resource requirements, and resource availability. This paper describes ISIS, a scheduling system capable of incorporating all relevant constraints in the construction of job shop schedules. We examine both the representation of constraints within ISIS, and the manner in which these constraints are used in conducting a constraint-directed search for an acceptable schedule. The important issues relating to the relaxation of constraints are addressed. Finally, the interactive scheduling facilities provided by ISIS are considered.
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  • 15
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 16
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    Expert systems 1 (1984), S. 0 
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  • 17
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    Expert systems 1 (1984), S. 0 
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    Topics: Computer Science
    Notes: Abstract: Log interpretation science is a controversial and rapidly changing domain. Designing interpretation models is a highly experimental process which involves trials with a computer program as an integral part of the design. Therefore conventional software engineering techniques, which require a complete specification of the problem before the program is written, are often not applicable or fail to produce high quality software. The development of expert systems has provided the techniques, tools, and capabilities to let us seek alternate methods to produce log interpretation software: exploratory programming environments and automatic programming systems. An exploratory programming environment combines the power of interactive graphics and programming tools to merge the design and programming tasks into a single process where model and program develop together. An automatic programming system will embody the knowledge of the programming process and of some log interpretation heuristics to produce log processing programs from interactive specifications expressed in familiar terms. These facilities will allow log interpretation model designers, who are non-computer specialists, to produce high quality software as the end result of a model design.
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  • 18
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    Expert systems 1 (1984), S. 0 
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  • 19
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    Expert systems 1 (1984), S. 0 
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  • 20
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    Expert systems 1 (1984), S. 0 
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  • 22
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    Mathematical programming 19 (1980), S. 300-312 
    ISSN: 1436-4646
    Keywords: Equilibrium Prices ; Nonconvex Mathematical Programming ; Shadow Prices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper a definition is proposed for the concept of shadow prices in nonconvex programming. For a nonlinear program with equality and inequality constraints, existence of these prices and bounds for their possible values are obtained under the Mangasarian—Fromowitz regularity condition. Their exact values and some continuity properties are obtained under the more restrictive linear independence regularity condition. A definition of equilibrium prices is also proposed. Under convexity assumptions, all definitions and results coincide with those already known on this subject in convex programming.
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  • 23
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    Mathematical programming 19 (1980), S. 313-327 
    ISSN: 1436-4646
    Keywords: Retrogressing Paths ; Homotopy Method ; Fixed-point Algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract For certain functionsf fromR n toR n , the Eaves—Saigal algorithm computes a path inR n × (0, 1] which converges to a zero off. In this case, it is shown that even whenf is of classC ∞ and has a unique zero, the converging path may retrogress infinitely many times.
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  • 24
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    Mathematical programming 21 (1981), S. 190-203 
    ISSN: 1436-4646
    Keywords: Complementarity Problem ; Cones ; Topological Degree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we consider the problem of establishing the number of solutions to the complementarity problem. For the case when the Jacobian of the mapping has all principal minors negative, and satisfies a condition at infinity, we prove that the problem has either 0, 1, 2 or 3 solutions. We also show that when the Jacobian has all principal minors positive, and satisfies a condition at infinity, the problem has a unique solution.
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  • 25
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    Mathematical programming 21 (1981), S. 233-234 
    ISSN: 1436-4646
    Keywords: Polytope ; Subdivision ; Simplex ; Volume ; Centroid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Subdivisions of polytopes are described which place any chosen vertex in a (near-) minimal number of simplices. Ancillary procedures to find volumes and centroids of polytopes are indicated.
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  • 26
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    Mathematical programming 21 (1981), S. 301-318 
    ISSN: 1436-4646
    Keywords: Semi-infinite Programs ; Open Helly-type Theorems ; Finite Subprograms ; Convex Programs ; Multi-criteria Programs ; Quasi-convex Programs ; Quasi-differentiable Programs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We show that a semi-infinite quasi-convex program with certain regularity conditions possesses finitely constrained subprograms with the same optimal value. This result is applied to various problems.
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  • 27
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    Mathematical programming 21 (1981), S. 348-356 
    ISSN: 1436-4646
    Keywords: Multi-extremal Optimization ; Multinomial Distribution ; Bayes Estimate ; Monte Carlo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The solution of ak-extremal problem is defined as the set of pairs (x i * , θi),i = 1, ⋯ ,k, where x t * isi th local minimum andθ i is the volume of the set of attraction of this minimum. A Bayesian estimate ofk and (θ 1 , ⋯ , θ k ) is constructed.
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    Mathematical programming 22 (1982), S. 71-81 
    ISSN: 1436-4646
    Keywords: Blocking ; Antiblocking ; Polarity ; Penumbra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract E. Johnson has recently shown that the concept of a penumbra leads to a simple geometric description of the blocker and antiblocker of a given set. Here we develop some basic results on penumbras which permit us to slightly generalize and simplify results on their relationship to blocking and antiblocking theory. In addition, motivated by the obvious symmetry of our results, we examine the effect of reversing the blocking and antiblocking operations.
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  • 29
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    Mathematical programming 22 (1982), S. 121-121 
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  • 30
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    Mathematical programming 22 (1982), S. 148-162 
    ISSN: 1436-4646
    Keywords: Set Covering Problem ; Median Problem ; Location Problems ; Heuristics ; Worst Case Analysis ; Continuous Location Problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We describe in this paper polynomial heuristics for three important hard problems—the discrete fixed cost median problem (the plant location problem), the continuous fixed cost median problem in a Euclidean space, and the network fixed cost median problem with convex costs. The heuristics for all the three problems guarantee error ratios no worse than the logarithm of the number of customer points. The derivation of the heuristics is based on the presentation of all types of median problems discussed as a set covering problem.
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  • 31
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    Mathematical programming 22 (1982), S. 227-230 
    ISSN: 1436-4646
    Keywords: Minimax ; Nonconvex Optimization ; Stationary Points
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We give a short proof that in a convex minimax optimization problem ink dimensions there exist a subset ofk + 1 functions such that a solution to the minimax problem with thosek + 1 functions is a solution to the minimax problem with all functions. We show that convexity is necessary, and prove a similar theorem for stationary points when the functions are not necessarily convex but the gradient exists for each function.
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  • 32
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    Mathematical programming 18 (1980), S. 186-196 
    ISSN: 1436-4646
    Keywords: Weber's Problem ; Weiszfeld's Method ; Optimal Location
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract For solving the Euclidean distance Weber problem Weiszfeld proposed an iterative method. This method can also be applied to generalized Weber problems in Banach spaces. Examples for generalized Weber problems are: minimal surfaces with obstacles, Fermat's principle in geometrical optics and brachistochrones with obstacles.
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  • 33
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    Mathematical programming 18 (1980), S. 84-88 
    ISSN: 1436-4646
    Keywords: Complementary Pivot Algorithms ; Triangulations ; Vector Labels ; Borsuk's Theorem on Antipodal Points
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this short note a simple and constructive proof is given for Borsuk's theorem on antipodal points. This is done through a special application of the complementary pivoting algorithm.
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  • 34
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    Mathematical programming 18 (1980), S. 110-110 
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  • 35
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    Mathematical programming 18 (1980), S. 155-168 
    ISSN: 1436-4646
    Keywords: Constrained Optimization ; Differential Equation ; Global Solution ; Nonlinear Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A new method is presented for finding a local optimum of the equality constrained nonlinear programming problem. A nonlinear autonomous system is introduced as the base of the theory instead of usual approaches. The relation between critical points and local optima of the original optimization problem is proved. Asymptotic stability of the critical points is also proved. A numerical algorithm which is capable of finding local optima systematically at the quadratic rate of convergence is developed from a detailed analysis of the nature of trajectories and critical points. Some numerical results are given to show the efficiency of the method.
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  • 36
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    Mathematical programming 18 (1980), S. 215-227 
    ISSN: 1436-4646
    Keywords: Frank—Wolfe Theorem ; Quadratic Programming ; Norm Coercive Functions ; Polyhedral Sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The Frank—Wolfe theorem states that a quadratic function, bounded below on a nonempty polyhedral convex set, attains its infimum there. This paper gives sufficient conditions under which a function either attains its infimum on a nonempty polyhedral convex set or is unbounded below on some halfline of that set. Quadratic functions are shown to satisfy these sufficient conditions.
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    Mathematical programming 18 (1980), S. 248-273 
    ISSN: 1436-4646
    Keywords: Legendre Transform ; Stationary Points ; Convex Functions ; Duality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this work non-convex programs are analyzed via Legendre transform. The first part includes definitions and the classification of programs that can be handled by the transformation. It is shown that differentiable functions that are represented as a sum of strictly concave and convex functions belong to this class. Conditions under which a function may have such representation are given. Pseudo duality is defined and the pseudo duality theorem for non linear programs with equality constraints is proved. The techniques described are constructive ones, and they enable tocalculate explicitly a pseudo dual once the primal program is given. Several examples are included. In the convex case these techniques enable the explicit calculation of the dual even in cases where direct calculation was not possible.
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  • 38
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    Mathematical programming 18 (1980), S. 286-290 
    ISSN: 1436-4646
    Keywords: Facility Location ; Steiner's Problem ; Location on the Sphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This note describes the nature of optimal solutions for the spherical Steiner-Weber location problem for the case of unit weights and either 3 or 4 demand points (requireing 4 demand points to lie in an open hemisphere). Geometrically appealing results which are necessary conditions for optimum solutions and spherical analogs of known planar results are obtained.
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  • 39
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    Mathematical programming 24 (1982), S. 257-268 
    ISSN: 1436-4646
    Keywords: Nondifferentiable Programming ; Convex Analysis ; Sensivity Analysis ; Duality Theory ; Second Order Derivative ; Second Order Methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We study differential properties of the support function of the∈-subdifferential of a convex function; applications in algorithmics are also given.
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  • 40
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    Mathematical programming 18 (1980), S. 62-67 
    ISSN: 1436-4646
    Keywords: Economic Interpretation ; Mathematical Programming ; Duality ; Stochastic Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The purpose of this note is to interpret a class of stochastic programming problems in economic terms. The primal stochastic program is shown to represent a certain production program of an entrepreneur. The dual program, which is also a stochastic program, represents the problem of a contractor who desires to purchase the entrepreneur's resources and sell product back to him.
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    Mathematical programming 21 (1981), S. 120-120 
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  • 42
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    Mathematical programming 21 (1981), S. 319-330 
    ISSN: 1436-4646
    Keywords: Nonlinear Programming ; Geometric Programming ; Duality Theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The several published methods for mapping a dual solution estimate to a primal solution estimate in posynomial geometric programming provide no criteria for deciding how much deviation from primal feasibility, or discrepancy between the primal and dual objective function values, should be permitted before the primal solution estimate is accepted by the designer. This paper presents a new and simple dual-to-primal conversion method that uses the cost coefficients to provide a sound economic criterion for determining when to accept a primal solution estimate. The primal solution estimate generated is the exact solution to a modified primal obtained from the given primal by modifying the cost coefficients, with the exponent matrix left unchanged. The method is shown to have desirable properties when coupled with a convergent dual algorithm.
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    Mathematical programming 22 (1982), S. 93-103 
    ISSN: 1436-4646
    Keywords: Linear Programming ; Relaxation Method ; Polynomiality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A class of linear programs is given in which the relaxation method for inequalities, under the same operating rules as Khacian's method, is not polynomial in the length of the input. This result holds for any value of the relaxation parameter.
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    Mathematical programming 22 (1982), S. 117-120 
    ISSN: 1436-4646
    Keywords: Augmenting Path Algorithm ; Boolean Lattice ; Jordan-Hölder Theorem ; Matroid Intersection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It is noted that the decomposition of a network presented by J.C. Picard and M. Queyranne through an algorithmic argument may be defined from a general lattice-theoretic result for more general problems for which the equalities of maximum-flow minimum-cut type hold.
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  • 45
    ISSN: 1436-4646
    Keywords: Geometric Programming ; Code Comparisons ; Numerical Testing ; Nonlinear Programming
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Ten codes or code variants were used to solve the five equivalent posynomial GP problem formulations. Four of these codes were general NLP codes; six were specialized GP codes. A total of forty-two test problems was solved with up to twenty randomly generated starting points per problem. The convex primal formulation is shown to be intrinsically easiest to solve. The general purpose GRG code called OPT appears to be the most efficient code for GP problem solution. The reputed superiority of the specialized GP codes GGP and GPKTC appears to be largely due to the fact that these codes solve the convex primal formulation. The dual approaches are only likely to be competitive for small degree of difficulty, tightly constrained problems.
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    Mathematical programming 22 (1982), S. 231-235 
    ISSN: 1436-4646
    Keywords: Integer Programming ; Covering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetA be a non-negative matrix with integer entries and no zero column. The integer round-up property holds forA if for every integral vectorw the optimum objective value of the generalized covering problem min{1y: yA ≥ w, y ≥ 0 integer} is obtained by rounding up to the nearest integer the optimum objective value of the corresponding linear program. A polynomial time algorithm is presented that does the following: given any generalized covering problem with constraint matrixA and right hand side vectorw, the algorithm either finds an optimum solution vector for the covering problem or else it reveals that matrixA does not have the integer round-up property.
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    Mathematical programming 21 (1981), S. 1-18 
    ISSN: 1436-4646
    Keywords: Game Theory ; Cost Allocation ; Spanning Tree
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    Notes: Abstract We consider the problem of cost allocation among users of a minimum cost spanning tree network. It is formulated as a cooperative game in characteristic function form, referred to as a minimum cost spanning tree (m.c.s.t.) game. We show that the core of a m.c.s.t. game is never empty. In fact, a point in the core can be read directly from any minimum cost spanning tree graph associated with the problem. For m.c.s.t. games with efficient coalition structures we define and construct m.c.s.t. games on the components of the structure. We show that the core and the nucleolus of the original game are the cartesian products of the cores and the nucleoli, respectively, of the induced games on the components of the efficient coalition structure.
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    Mathematical programming 21 (1981), S. 119-119 
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    Mathematical programming 21 (1981), S. 121-136 
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    Keywords: Linear Programming ; Polynomial Algorithms ; Total Unimodularity
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    Topics: Computer Science , Mathematics
    Notes: Abstract This paper describes several algorithms for solution of linear programs. The algorithms are polynomial when the problem data satisfy certain conditions.
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    Mathematical programming 21 (1981), S. 182-189 
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    Keywords: Equilibrium ; Linear Monetary Economy ; Linear Programming
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    Notes: Abstract An algorithm is presented for computing equilibria in a linear monetary economy, that is, an exchange economy in which all individuals have linear utility functions and in which goods are bought and sold only in exchange for money. The algorithm computes the equilibrium prices by solving a finite sequence of linear programming problems.
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    Mathematical programming 21 (1981), S. 229-232 
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    Keywords: Primal Feasible Basis ; Dual Feasible Basis ; Basic Variable ; Nonbasic Variable ; Optimal Basic Solution
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    Topics: Computer Science , Mathematics
    Notes: Abstract In a recent paper M.C. Cheng proposed new criteria for the simplex algorithm which guarantee that (i) a nonbasic variable of a basic feasible solution will remain nonbasic in an optimal basic solution, (ii) a basic variable of a basic solution will remain basic in an optimal basic solution. This comment gives (i) a slight generalization of the first result and (ii) a counterexample to the second proposition.
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    Mathematical programming 21 (1981), S. 240-240 
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    Mathematical programming 21 (1981), S. 241-261 
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    Keywords: Dual problem ; Duality Theory ; Optimality Conditions ; Price Functions ; Nonlinear Programming ; Integer Programming
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    Notes: Abstract We survey some recent developments in duality theory with the idea of explaining and unifying certain basic duality results in both nonlinear and integer programming. The idea of replacing dual variables (prices) by price functions, suggested by Everett and developed by Gould, is coupled with an appropriate dual problem with the consequence that many of the results resemble those used in linear programming. The dual problem adopted has a (traditional) economic interpretation and dual feasibility then provides a simple alternative to concepts such as conjugate functions or subdifferentials used in the study of optimality. In addition we attempt to make precise the relationship between primal, dual and saddlepoint results in both the traditional Lagrangean and the more general duality theories and to see the implications of passing from prices to price functions. Finally, and perhaps surprisingly, it appears that all the standard algorithms terminate by constructing primal and dual feasible solutions of equal value, i.e., by satisfying generalised optimality conditions.
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    Mathematical programming 21 (1981), S. 358-358 
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    Mathematical programming 22 (1982), S. 12-38 
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    Keywords: Graph ; Matching ; Branching ; Linear Programming ; Polyhedron
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    Notes: Abstract Matching forests generalize branchings in a directed graph and matchings in an undirected graph. We present an efficient algorithm, the PMF Algorithm, for the problem: given a mixed graphG and a real weight on each of its edges, find a perfect matching forest of maximum weight-sum. The PMF Algorithm proves the sufficiency of a linear system which definesP = (G) andP(G), the convex hull of incidence vectors of perfect matching forests and matching forests respectively ofG. The algorithm also provides a generalization of Tutte's theorem on the existence of perfect matchings in an undirected graph.
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    Mathematical programming 22 (1982), S. 122-123 
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    Mathematical programming 22 (1982), S. 141-147 
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    Keywords: Integer Rounding ; Pluperfect Graphs ; Combinatorial Optimization
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    Notes: Abstract LetA be a nonnegative integral matrix with no zero columns. Theinteger round-up property holds forA if for each nonnegative integral vectorw, the solution value to the integer programming problem min{1 ⋅y: yA ≥ w, y ≥ 0, y integer} is obtained by rounding up to the nearest integer the solution value to the corresponding linear programming problem min{1 ⋅y: yA ≥ w, y ≥ 0}. Theinteger round-down property is similarly defined for a nonnegative integral matrixB with no zero rows by considering max{1 ⋅y: yB ≤ w, y ≥ 0, y integer} and its linear programming correspondent. It is shown that the integer round-up and round-down properties can be checked through a finite process. The method of proof motivates a new and elementary proof of Fulkerson's Pluperfect Graph Theorem.
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    Mathematical programming 22 (1982), S. 236-237 
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    Mathematical programming 22 (1982), S. 304-315 
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    Keywords: Location Theory ; Tree Networks ; Rigid Circuit Graphs ; Polynomial Algorithms
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    Notes: Abstract We discuss several forms of thep-center location problems on an undirected tree network. Our approach is based on utilizing results for rigid circuit graphs to obtain polynomial algorithms for solving the model. Duality theory on perfect graphs is used to define and solve the dual location model.
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    Mathematical programming 23 (1982), S. 111-116 
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    Keywords: Multicriteria Optimization ; Convex Analysis
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    Notes: Abstract Existence and characterization theorems for the efficient (nondominated) set of decisions inR n are presented. The existence is proved when the set of decisions satisfies some compactness conditions. The efficient set is characterized in terms of the exposed efficient decisions when certain convexity and compactness conditions are satisfied.
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    Mathematical programming 23 (1982), S. 170-180 
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    Keywords: Set Covering ; Heuristic Algorithms ; Worst Case Analysis ; Bounds
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    Notes: Abstract In [2], Chvatal provided the tight worst case bound of the set covering greedy heuristic. We considered a general class of greedy type set covering heuristics. Their worst case bounds are dominated by that of the greedy heuristic.
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    Mathematical programming 23 (1982), S. 216-226 
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    Keywords: Nonsmooth Optimization ; Subgradient ; Subdifferential ; Bundle Type Method ; Deletion Rule ; Resetting
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    Notes: Abstract A numerical method for the unconstrained minimization of a convex nonsmooth function of several variables is presented. It is closely related to the ‘bundle type’ approach and to the conjugate subgradient method. A way is suggested to reduce the amount of information to be stored during the computational procedure. Global convergence of the method to the minimum is proved.
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    Mathematical programming 23 (1982), S. 326-340 
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    Keywords: Optimization ; Quasi-Newton ; Conjugate Gradient
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    Notes: Abstract In this paper we study conjugate gradient algorithms for large optimization problems. These methods accelerate (or precondition) the conjugate gradient method by means of quasi-Newton matrices, and are designed to utilize a variable amount of storage, depending on how much information is retained in the quasi-Newton matrices. We are concerned with the behaviour of such methods on the underlying quadratic model, and in particular, with finite termination properties.
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    Mathematical programming 23 (1982), S. 357-360 
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    Mathematical programming 18 (1980), S. 138-145 
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    Keywords: Set-covering Problem ; Branch and Bound ; Lower Bounds ; Steiner Triple Systems
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    Notes: Abstract Fulkerson et al. have given two examples of set covering problems that are empirically difficult to solve. They arise from Steiner triple systems and the larger problem, which has a constraint matrix of size 330 × 45 has only recently been solved. In this note, we show that the Steiner triple systems do indeed give rise to a series of problems that are probably hard to solve by implicit enumeration. The main result is that for ann variable problem, branch and bound algorithms using a linear programming relaxation, and/or elimination by dominance require the examination of a super-polynomial number of partial solutions
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    Mathematical programming 18 (1980), S. 228-228 
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    Mathematical programming 18 (1980), S. 232-232 
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    Mathematical programming 18 (1980), S. 308-329 
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    Keywords: Polytopes ; Linear Programming
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    Notes: Abstract This paper provides answers to several questions raised by V. Klee regarding the efficacy of Mattheiss' algorithm for finding all vertices of convex polytopes. Several results relating to the expected properties of polytopes are given which indicate thatn-polytopes defined by “large” numbers of constraints are difficult to obtain by random processes, the expected value of the number of vertices of polytope is considerably less than Klee's least upper bound the expected performance of Mattheiss' algorithm is far better than Klee's upper bound would suggest.
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    Computing 24 (1980), S. 341-347 
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    Keywords: Numerical analysis ; Volterra integral equations of the second kind ; stability
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    Description / Table of Contents: Zusammenfassung Ziel dieser Arbeit ist es, die Stabilitätseigenschaften einer Klasse Volterrascher Integralgleichungen zweiter Art zu untersuchen. Unsere Behandlung ist der üblichen Stabilitätsanalyse ähnlich, in der die Kernfunktionen zu einer im voraus beschränkten Klasse von Testfunktionen gehören. Wir haben die Klasse der “endlich zerlegbaren” Kerne betrachtet. Stabilitätsbedingungen werden abgeleitet und verglichen mit den Bedingungen für die einfache Testgleichung. Es zeigt sich, daß die neuen Kriteria einschränkender sind als die konventionellen Bedingungen. Der praktische Wert wird getestet durch numerische Experimente mit der Trapezregel.
    Notes: Abstract The purpose of this paper is to analyse the stability properties of a class of multistep methods for second kind Volterra integral equations. Our approach follows the usual analysis in which the kernel function is a priori restricted to a special class of test functions. We consider the class of finitely decomposable kernels. Stability conditions will be derived and compared with those obtained with the simple test equation. It turns out that the new criteria are more severe than the conventional conditions. The practical value is tested by numerical experiments with the trapezoidal rule.
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    Keywords: 65 J ; 65 H
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    Description / Table of Contents: Summary A generalization of the concept of a divided difference operator introduced by J. W. Schmidt is derived. The inclusion of solutions by certain Regula-falsi-methods realized by a well known approximation of the Jacobian matrix, which is no divided difference operator in the sense of Schmidt but a realization of this generalization, is proved.
    Notes: Zusammenfassung Durch Verallgemeinerung des von J. W. Schmidt eingeführten Steigungsbegriffes gelingt es, bei Durchführung gewisser Verfahren vom Regula-falsi-Typ mit einer naheliegenden und häufig verwendeten Approximation der Funktionalmatrix, die keine Steigung im herkömmlichen Sinne darstellt, jedoch eine Realisierung der oben genannten Verallgemeinerung liefert, Einschließungsaussagen für Lösungen von Operatorgleichungen nachzuweisen.
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    Computing 26 (1981), S. 57-66 
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    Description / Table of Contents: Abstract An algorithm is proposed for computation of the exponential of a matrixX which uses the well known continued fraction expansion of tanhX. ForX essentially-nonnegative the following is proved: In interval arithmetic the algorithm is feasible, numerically convergent and bound conserving; after possibly a few initial steps it gives alternatively lower and upper bounds to the exact result.
    Notes: Zusammenfassung Es wird ein Algorithmus zur Berechnung der Exponentialfunktion von MatrizenX vorgeschlagen, der die Kettenbruch-Entwicklung von tanhX benutzt. IstX wesentlich-nichtnegativ, dann gilt: Der Algorithmus ist in Intervall-Arithmetik durchführbar, numerisch konvergent und schrankentreu; von einem Index an liefert er alternierend untere und obere Schranken für das exakte Ergebnis.
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    Computing 26 (1981), S. 45-56 
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    Keywords: Order-convex operator ; Banach space ; Existence ; Convergence ; Operator equation ; partially ordered topological linear space ; 65J15 ; 47H17 ; 47H07
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    Description / Table of Contents: Zusammenfassung SeiF:X→Y ein ordnungskonvexer Operator, woX, Y halbgeordnete Banachräume sind. Es werden zwei verwandte Verfahren zur Lösung der GleichungF(x)=0 diskutiert, von denen eines schon von Pasquali beschrieben worden ist (s. [2]), das andere von Wolfe [12]. Existenz- und Konvergenzsätze für diese Verfahren sind dargestellt und mit Hilfe von Beispielen illustriert. Ferner liegen einige Bemerkungen über ein Verfahren von Traub vor, das auch schon von Wolfe diskutiert worden ist [12].
    Notes: Abstract LetF:X→Y be an order-convex operator, whereX, Y are partially ordered Banach spaces. Two related methods for the solution ofF(x)=0 are discussed, one of which has been studied by Pasquali (see [2]) and the other by Wolfe [12]. Existence-convergence theorems for the methods are given, and these are illustrated with the aid of example. Some remarks are also made on a method due to Traub [7] which has also been discussed by Wolfe [12].
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    Computing 26 (1981), S. 19-31 
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    Description / Table of Contents: Zusammenfassung Gegeben sei ein Pseudo-Zufallszahlen-Generator, der gleichverteilte StichprobenU aus dem Intervall (0, 1) liefert, und eine statistische Verteilung, beschrieben durch ihre VerteilungsfunktionF(x). Dann erzeugt die InversionsmethodeX←F −1(U) Stichproben vonF(x). Ein Verfahren wird entwickelt, das “Guide”-Tafeln erstellt, mit dem Ziel, diese Inversion zu ermöglichen, so daß das Verfahren für beliebigeF(x) effizient wird. Für diskrete Verteilungen sind diese Tafeln klein und leicht zu erstellen, und der entstehende Stichproben-Algorithmus kann mit bekannten allgemeinen Verfahren gut konkurrieren. Stetige Verteilungen erfordern längere Vorbereitungszeiten und mehr Speicherplatz für die Tafeln. Diese werden mit Hilfe gegebener Wahrscheinlichkeitsdichtenf(x) vorbereitet. Die Methode ist anwendbar auf “vernünftige”f(x), einschließlich der normalerweise in der Statistik vorkommenden Fälle. Aufgrund der angeführten Rechenerfahrung mit Poisson-, Normal-, Gamma- und Cauchy-Verteilungen zeigt sich, daß unser allgemeines Verfahren fast so schnell ist, wie die besten bekannten Methoden, die speziell auf diese Verteilungen zugeschnitten wurden.
    Notes: Abstract Given a basic pseudo-random number generator which returns uniformly distributed samplesU from the interval (0, 1) and a statistical distribution as defined by its distribution functionF(x). Then the inversion methodX←F −1 (U) produces samples fromF(x). A procedure is developed which prepares “guide tables” in order to facilitate this inversion so that sampling becomes efficient for arbitraryF(x). For discrete distributions these tables are small and easy to set up, and the resulting sampling algorithm compares well with known general methods. Continuous distributions require longer set-up times and more space for tables. These are prepared using given probability densitiesf(x). The method can cope with “reasonable”f(x) including most cases which are commonly encountered in statistics. The reported computational experience, on Poisson, Normal, Gamma and Cauchy distributions, indicates that our general routine is almost as fast as the best known sampling algorithms which were specially designed for these distributions.
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    Computing 26 (1981), S. 67-71 
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    Description / Table of Contents: Zusammenfassung Die Berechnung von beliebigen Funktionen dreieckiger Matrizen ist rekursiveweise ermöglicht mittels einfacher Eigenschaften, dagelegt in diesem Bericht.
    Notes: Abstract Any function of a triangular matrix can be recursively calculated on the basis of simple properties stated in this paper.
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    Computing 26 (1981), S. 73-77 
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    Keywords: Cauchy type singular integral equations ; natural interpolation formulae ; Gauss-Chebyshev quadrature rule ; Nyström (quadrature) method for integral equations ; direct numerical solution of Cauchy type singular integral equations ; Primary: 65R20 ; Secondary: 45E05, 45L10, 65D05
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    Description / Table of Contents: Zusammenfassung Eine singuläre Integralgleichung erster Art vom Cauchy-Typ kann entweder direkt, mittels einer Gaußschen numerischen Integrationsformel, oder durch Reduktion auf eine äquivalente Fredholmsche Integralgleichung zweiter Art, wo die Nyström-Methode anwendbar ist, gelöst werden. In dieser Arbeit wird bewiesen, daß unter geeigneten und sinnvollen Bedingungen die Ausdrücke der unbekannten Funktion der Integralgleichung, die einerseits bei den natürlichen Integrationsformeln der direkten Methode und anderseits bei der Nyström-Methode entstehen, im ganzen Integrationsintervall gleich sind.
    Notes: Abstract A Cauchy type singular integral equation of the first kind can be numerically solved either directly, through the use of a Gaussian numerical integration rule, or by reduction to an equivalent Fredholm integral equation of the second kind, where the Nyström method is applicable. In this note it is proved that under appropriate but reasonable conditions the expressions of the unknown function of the integral equation, resulting from the natural interpolation formulae of the direct method, as well as of the Nyström method, are identical along the whole integration interval.
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    Computing 26 (1981), S. 79-82 
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    Description / Table of Contents: Zusammenfassung Es werden notwendige und hinreichende Bedingungen für das Problem der linearen Optimierung mit Intervallkoeffizienten angegeben, bei denen jedes Problem der linearen Optimierung, dessen Koeffizienten in gegebenen Intervallen fixiert werden, eine optimale Lösung besitzt.
    Notes: Abstract Necessary and sufficient conditions for a linear programming problem whose parameters (both in constraints and in the objective function) are prescribed by intervals are given under which any linear programming problem with parameters being fixed in these intervals has a finite optimum.
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    Computing 26 (1981), S. 87-89 
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    Description / Table of Contents: Zusammenfassung Tseitin [3] und Galil [1] haben gezeigt, daß es in der Aussagenlogik für unendlich vielen KlausenmengenS(n) der Längen gibt, so daß jeder reguläre Resolutionsbeweis fürS(n) mindestens 2 cn (für einec〉0) verschiedene Klausen enthält. Wir geben hier einen einfacheren Beweis für die viel schwächere aber dennoch nichtpolynomiale Schranke 2 clog 2 n an.
    Notes: Abstract Tseitin [3] and Galil [1] have proven that for infinitely manyn there is a set of clausesS(n) of the propositional calculus of lengthn such that any regular resolution proof ofS(n) produces at least 2 cn distinct new clauses for somec〉0. We show that it is possible to obtain a much weaker but still non-polynomial bound of 2 clog 2 n by a simpler argument.
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    Computing 26 (1981), S. 83-86 
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    Description / Table of Contents: Zusammenfassung Wir wenden den Satz, daß für eine Segmentfunktionf, deren SegmentableitungD(f) auf dem Segment [0, 1] von oben beschränkt ist, der Hausdorff-Abstand zwischenD(f) und der Ableitung eines linearen Operators durch den Modul derH-Stetigkeit vonD(f) und Konstante nach oben beschränkt ist, an auf Bernstein-Polynome und Mirakyan-Szász-Operatoren.
    Notes: Abstract Given a segment functionf, whose segment-derivative is bounded from above on the segment [0, 1] we applicate the theorem, that the Hausdorff distance betweenD(f) and the derivative of a linear operator is bounded from above by the modulus of H-continuity ofD(f) and some constants, to Bernstein polynomials and Mirakyan-Szász-operators.
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    Computing 26 (1981), S. 91-105 
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    Keywords: 65N20 ; Adaptive mesh refinement ; multigrid methods ; finite element methods
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    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Das Unterprogramm PLTMG ist ein FORTRAN-Programm zur Lösung selbstadjungierter elliptischer Randwertprobleme für beliebige Bereiche desR 2. Es basiert auf einer stückweise-linearen Finite-Element-Methode, einer adaptiven Gitterverfeinerungsmethode und einer mehrstufigen iterativen Methode zur Lösung des resultierenden Systems linearer Gleichungen. In dieser Arbeit wird die Methode beschrieben, und einige numerische Ergebnisse und Vergleiche werden dargelegt.
    Notes: Abstract Subroutine PLTMG is a Fortran program for solving self-adjoint elliptic boundary value problems in general regions ofR 2. It is based on a piecewise linear triangle finite element method, an adaptive grid refinement procedure, and a multi-level iterative method to solve the resulting sets of linear equations. In this work we describe the method and present some numerical results and comparisons.
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  • 80
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    Description / Table of Contents: Zusammenfassung Die Benutzung algebraischer Eigenwerte zur näherungsweisen Berechnung der Eigenwerte von Sturm-Liouville-Operatoren ist bekanntlich nur für die Grundschwingung und einige weitere Harmonische zufriedenstellend. In dieser Arbeit zeigen wir, wie man den asymptotischen Fehler, der bei verwandten aber einfachen Sturm-Liouville-Operatoren auftritt, dazu benutzen kann, um gewisse Klassen algebraischer Eigenwerte so zu korrigieren, daß die gleichmäßig gute Approximationen liefern.
    Notes: Abstract The use of algebraic eigenvalues to approximate the eigenvalues of Sturm-Liouville operators is known to be satisfactory only when approximations to the fundamental and the first few harmonics are required. In this paper, we show how the asymptotic error associated with related but simpler Sturm-Liouville operators can be used to correct certain classes of algebraic eigenvalues to yield uniformly valid approximations.
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  • 81
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    Computing 26 (1981), S. 107-121 
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    Keywords: Primary: 65 H ; Secondary: 47 H ; Turning points ; Newton-like methods ; continuation methods ; local convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die RaumkurveL werde implizit durch das nichtlineare (n, n+1)-SystemH(u)=0 definiert. Es wird ein neues direktes Newton-ähnliches Verfahren zur Bestimmung der Rückkehrpunkte vonL beschrieben, das pro Schritt lediglich die Berechnung einer Jacobimatrix und 5 Funktionswerten vonH erfordert. Außerdem ist pro Schritt ein lineares Gleichungssystem der Dimensionn+1 mit 4 verschiedenen rechten Seiten zu lösen. Unter passenden voraussetzungen wird die lokale undQ-quadratische Konvergenz des Verfahrens bewiesen, sofern eine gewisse Diskretisierungsschrittweise geeignet gewählt wird. Zwei numerische Beispiele bestätigen die theoretischen Resultate.
    Notes: Abstract Let the space curveL be defined implicitly by the (n, n+1) nonlinear systemH(u)=0. A new direct Newton-like method for computing turning points ofL is described that requires per step only the evaluation of one Jacobian and 5 function values ofH. Moreover, a linear system of dimensionn+1 with 4 different right hand sides has to be solved per step. Under suitable conditions the method is shown to converge locally withQ-order two if a certain discretization stepsize is appropriately chosen. Two numerical examples confirm the theoretical results.
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  • 82
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    Computing 26 (1981), S. 155-166 
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    Keywords: decomposable searching problem ; dynamization ; merging ; quad-trees ; k-d trees ; halfspaces ; maximal elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir definieren zwei Klassen zerlegbarer Suchprobleme und untersuchen, wie man diese Probleme effizient dynamisch lösen könnte. Für die erste Klasse (DD) zeigen wir, daß man sowohl das Einfügen als auch das Streichen von einzelnen Elementen im Zeitmittel effizient durchführen kann. Für die zweite Klasse (MD) zeigen wir zudem, daß man mit der Benützung einer schnellen Mischungsprozedur die Effizienz noch um ein wenig verbessern kann. Alss Anwendungen zeigen wir z. B. die effiziente Dynamisierung von Quadbäumen und vom gemeinsamen Durchschnitt endlich vieler Halbebenen in der Ebene.
    Notes: Abstract We define two classes of decomposable searching problems and consider ways of efficiently dynamizing them. For the first class, DD, we show that both insertions and deletions can be processed efficiently. For the second class, MD, we exploit a merge technique to obtain better insertion times. We also give a number of examples of problems to which the methods apply, including the dynamic maintenance of quadtrees and of the common intersection of finitely many halfspaces in the plane.
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  • 83
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    Keywords: 90C30 ; 65K05 ; Nonlinear programming algorithms ; penalty algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Diese Arbeit beschreibt einen Algorithmus zur Minimierung einer nichtlinearen Funktion mit nichtlinearen Ungleichungen und Gleichungen als Nebenbedingungen. Die vorgeschlagene Methode hat die Eigenschaft, daß sie unter schwachen Voraussetzungen gegen einen Kuhn-Tucker-Punkt des betrachteten Optimierungsproblems konvergiert und unter stärkeren Voraussetzungen eine quadratische Konvergenzgeschwindigkeit aufweist. Ähnlich wie eine vor kurzem von Rosen vorgeschlagene Methode benutzt der Algorithmus eine Straffunktion, um einen Punkt in der Nähe der optimalen Lösung zu berechnen und schaltet dann auf Robinsons Methode um. Die neue Methode hat gegenüber dem Verfahren von Rosen zwei neue Eigenschaften. Erstens wird der richtige Wert des Parameters in der Straffunktion automatisch gefunden. Zweitens enthalten die mit der Methode von Robinson gelösten Teilprobleme nur lineare Gleichungen als Nebenbedingungen. Die Teilprobleme können daher besonders leicht gelöst werden. Vorläufige numerische Ergebnisse werden berichtet.
    Notes: Abstract This paper presents an algorithm for the minimization of a nonlinear objective function subject to nonlinear inequality and equality constraints. The proposed method has the two distinguishing properties that, under weak assumptions, it converges to a Kuhn-Tucker point for the problem and under somewhat stronger assumptions, the rate of convergence is quadratic. The method is similar to a recent method proposed by Rosen in that it begins by using a penalty function approach to generate a point in a neighborhood of the optimum and then switches to Robinson's method. The new method has two new features not shared by Rosen's method. First, a correct choice of penalty function parameters is constructed automatically, thus guaranteeing global convergence to a stationary point. Second, the linearly constrained subproblems solved by the Robinson method normally contain linear inequality constraints while for the method presented here, only linear equality constraints are required. That is, in a certain sense, the new method “knows” which of the linear inequality constraints will be active in the subproblems. The subproblems may thus be solved in an especially efficient manner. Preliminary computational results are presented.
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  • 84
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    Computing 26 (1981), S. 209-225 
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    Description / Table of Contents: Zusammenfassung Es wird gezeigt, wie das probabilistische Konzept der Stoppzeit eines Zufallsprozesses für eine iterative Methode zur Lösung eines Systems linearer Gleichungen herangezogen werden kann. Alle bekannten iterativen Näherungsmethoden zur Lösung linearer Gleichungssysteme, wie z. B. die Blockmethoden nach Jakobi und Gauss-Seidel und Überrelaxationsmethoden, entsprechen verschieden gewählten Stoppzeiten. Das probabilistische Verfahren bietet die Möglichkeit, Lösungstechniken für die spezielle Struktur des Problems zu adaptieren. Darüber hinaus führen die vorgeschlagenen Methoden zu einer schnelleren Konvergenz.
    Notes: Abstract In this paper it is demonstrated how the probabilistic concept of a stopping time in a random process may be used to generate an iterative method for solving a system of linear equations. Actually all known iterative approximation methods for solving linear equations are generated by various choices of a stopping time e. g. the point and block Jacobi methods, the point and block Gauss-Seidel Methods and overrelaxation methods are covered. The probabilistic approach offers—in a natural way—the possibility of adapting the solution technique to the special structure of the problem. Moreover, posterior bounds for the solution are constructed, which lead to faster convergence of the approximations than with usual prior bounds.
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  • 85
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    Computing 26 (1981), S. 227-237 
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    Description / Table of Contents: Zusammenfassung In dieser Arbeit werden mehrere systematische Möglichkeiten angegeben, die es erlauben, bei der Verwendung der intervallmäßigen Auswertung der Ableitung in Iterationsverfahren gewisse Intervalle durch reelle Zahlen zu ersetzen. Dadurch wird im allgemeinen die Konvergenz beschleunigt. Die gleiche Problemstellung wurde bereits von einem anderen Ausgangspunkt ausgehend in [5] betrachtet.
    Notes: Abstract We discuss several systematic possibilities for removing certain intervals when using an interval expression of the derivative in iterative methods. In general, the speed of convergence is accelerated in this way. Starting from a different point of view the same problem has been treated recently in [5].
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  • 86
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    Computing 26 (1981), S. 239-246 
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    Description / Table of Contents: Zusammenfassung Es werden charakteristische Eigenschaften solcher Approximationen gegeben. Ein Algorithmus, der gute, aber nicht unbedingt beste Approximationen liefert, wird diskutiert.
    Notes: Abstract Characteristic properties of such approximations are given. An algorithm providing good, but not necessarily best, approximations is also discussed.
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  • 87
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    Computing 26 (1981), S. 247-256 
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    Description / Table of Contents: Zusammenfassung In dieser Arbeit werden sämtliche Nyström-Methoden fünfter Ordnung füry″=f(x, y) angegeben, welche vier Funktionsauswertungen pro Schritt benötigen. Es wird gezeigt, daß sich darunter nur eine einzige mit einem nichtleeren Periodizitätsintervall befindet.
    Notes: Abstract In this paper all fifth order Nyström methods fory″=f(x, y) based on four evaluations off are presented. Furthermore, we prove that out of these methods there is only one with a non-vanishing interval of periodicity.
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  • 88
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    Computing 26 (1981), S. 271-274 
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    Keywords: 65 G 10 ; Differentiation ; interval valued functions
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    Description / Table of Contents: Abstract This paper is concerned with relations between several versions of differentiation of interval valued functions.
    Notes: Zusammenfassung Es werden Beziehungen zwischen verschiedenen Ableitungsbegriffen für intervallwertige Funktionen angegeben.
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  • 89
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    Computing 26 (1981), S. 315-326 
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    Description / Table of Contents: Zusammenfassung Es wird eine einfache, aber wirkungsvolle Methode zur exakten Lösung eines nichtlinearen Gleichungssystems, dessen Funktionalmatrix in der Lösung singulär ist, vorgestellt. Dies wird durch eine Vergrößerung des Gleichungssystems zu einem höherdimensionalen Gleichungssystem, dessen entsprechende Lösung isoliert ist, erreicht. Diese Lösung kann daher z. B. mit dem Newton-Verfahren, das lokal mindestens quadratisch konvergent und selbstkorrigierend ist, mit großer Genauigkeit bestimmt werden.
    Notes: Abstract A simple but efficient method to obtain accurate solutions of a system of nonlinear equations with a singular Jacobian at the solution is presented. This is achieved by enlarging the system to a higher dimensional one whose solution in question is isolated. Thus it can be computed e. g. by Newton's method, which is locally at least quadratically convergent and selfcorrecting, so that high accuracy is attainable.
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  • 90
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    Description / Table of Contents: Zusammenfassung In numerischen Rechnungen treten neben den ganzen Zahlen häufig auch reelle und komplexe Zahlen, reelle und komplexe Intervalle sowie Vektoren und Matrizen über diesen Mengen auf. In der vorliegenden Arbeit erweitern wir die ProgrammierspracheFORTRAN so, daß Ausdrücke mit Operanden und Operatoren für all diese Typen (Datenmengen) akzeptiert werden. Wir beginnen mit einer kurzen Zusammenstellung dieser Räume und der arithmetischen Verknüpfungen in den Teilmengen, welche auf einem Rechner darstellbar sind. Es folgt dann eine allgemeine Beschreibung der Spracherweiterung sowie der neuen Standardfunktionen und Standardformelfunktionen für die zusätzlichen Datentypen. Im zweiten Teil der Arbeit geben wir dann die vollständige Syntax für die erweiterte Sprache in Form von leicht lesbaren Syntaxdiagrammen an. Wir erläutern auch die Semantik der Spracherweiterung.
    Notes: Abstract In addition to the integers, the real and complex numbers, the real segments (intervals) and complex segments as well as vectors and matrices over all of these comprise the fundamental data types in computation. We extendFORTRAN so that it accepts operands and operators for all of these types as primitives in expressions. We briefly review the spaces corresponding to these data types and the definitions of the arithmetic operations in their computer representable subsets. Then we give a general description of the language extension including the additional basic external functions and intrinsic functions for the new data types. Following this we give the syntax for the extended language in the form of easily traceable syntax diagrams. Comments on the semantics are also included.
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  • 91
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    Computing 26 (1981), S. 327-332 
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    Keywords: 65 N 20 (Numerical solution of nonlinear boundary value problems)
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    Description / Table of Contents: Abstract For nonlinear SOR-methods (Newton-SOR-methods) we discuss the problem how to get asymptotic optimal relaxation parameters ω(v). Here the matrix of the linear system at each step of iteration has not to be consistently ordered, we only assume symmetry and definitness. Our parameters are easy to compute and fixed for all steps. As an example nonlinear elliptic differential equations and their numerical solution by the finite element method or classical difference approximation are considered.
    Notes: Zusammenfassung Für nichtlineare SOR-Verfahren (Newton-SOR-Verfahren) wird ein einfaches Verfahren zur Berechnung asymptotisch optimaler Relaxationsparameter ω(v) erörtert. Hierbei muß die Matrix des in jedem Iterationsschritt auftretenden linearen Gleichungssystems nicht notwendig konsistent geordnet sein, wir setzen nur Symmetrie und Definitheit voraus. Es zeigt sich, daß die Parameter unabhängig von der jeweiligen Iterationsstufe ν gewählt werden können. Ihre Berechnung wird im Zusammenhang mit der numerischen Lösung nichtlinearer elliptischer Differentialgleichungen vermittels der Methode der finiten Elemente oder der klassischen Differentenapproximation diskutiert.
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  • 92
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    Computing 26 (1981), S. 333-342 
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    Description / Table of Contents: Zusammenfassung Für Folgen aus einem iterativen Näherungsverfahren, die einem mit Hilfe von Potenzfunktionen beschreibbaren System von Ungleichungen genügen, wird gezeigt, daß ihre R-Ordnung mindestens gleich dem Spektralradius der Matrix aus den Exponenten ist, sofern ein zum Spektralradius gehörender Eigenvektor mit ausschließlich positiven Komponenten existiert.
    Notes: Abstract The R-order of sequences, coupled by a system (1) of difference inequalities, is shown to be at least equal to the spectral radius of the matrix of the exponents if a positive eigenvector belonging to the spectral radius exists.
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  • 93
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    Computing 26 (1981), S. 355-360 
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    Description / Table of Contents: Zusammenfassung Es wird gezeigt, daß die Sicherheit eines Programmes für gewöhnliche Differentialgleichungen durch einen einfachen Trick wesentlich erhöht werden kann. Mit Hilfe dieser Idee und einer A-stabilen Rosenbrock-Formel haben wir ein kleines Programm geschrieben, welches gute numerische Resultate liefert.
    Notes: Abstract This note points out that the reliability of step-by-step integrators for ordinary differential equations can be increased considerably by a simple trick. We incorporated this idea into a program based on an A-stable Rosenbrock formula. This program comprises about 100 statements only and gives good numerical results.
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  • 94
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    Computing 26 (1981), S. 361-366 
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    Keywords: Convex hull ; average complexity ; geometrical complexity ; algorithms
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    Description / Table of Contents: Zusammenfassung Wir betrachtenn als unabhängig identisch verteilte Zufallsvektoren imR d mit der gemeinsamen Verteilungsdichtef. Die mittlere Konvexität eines Algorithmus zur Bestimmung der konvexen Hülle dieser Punkte seiE (C). Die meisten bekannten Algorithmen genügen für gewisse Klassen von Dichten der BedingungE (C)=0(n). In dieser Mitteilung zeigen wirE (C)=0(n) für Algorithmen, die im Vorlauf einen „Wegwerf-Schritt” benützen, wennf auf jedem nicht ausgearteten Rechteck desR 2 beschränkt ist und positiven Abstand von 0 besitzt.
    Notes: Abstract Considern independent identically distributed random vectors fromR d with common densityf, and letE (C) be the average complexity of an algorithm that finds the convex hull of these points. Most well-known algorithms satisfyE (C)=0(n) for certain classes of densities. In this note, we show thatE (C)=0(n) for algorithms that use a “throw-away” pre-processing step whenf is bounded away from 0 and ∞ on any nondegenerate rectangle ofR 2.
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  • 95
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    Computing 26 (1981), S. 367-378 
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    Keywords: Searchtrees ; 1–2 brother trees ; insertion ; deletion ; implementation ; PASCAL
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    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird eine PASCAL-Implementierung der Einfüge- und Entferne-Algorithmen für 1–2-Bruder-Bäume entwickelt. Die Implementierung ist nicht nur an sich interessant, sondern führte darüberhinaus zu einer Verbesserung des Entferne-Algorithmus.
    Notes: Abstract We derive an implementation in PASCAL of the insertion and deletion algorithms for 1–2 brother trees. The implementation is of interest not only in its own right but also in that it has given rise to an improved deletion algorithm.
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  • 96
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    Description / Table of Contents: Zusammenfassung Direkte Methoden zur Lösung von singulären Integralgleichungen vom Cauchy-Typus (S. I. G.) beruhen auf der Gaussschen Regel für numerische Integration, wobei die S. I. G. durch Anwendung der resultierenden Funktionalgleichung an geeignet gewählten Kollokationspunkten auf ein lineares Gleichungssystem reduziert wird. In diesem Artikel wurde die Äquivalenz dieser Methode mit derjenigen, welche auf der Lagrangeschen Interpolations-Approximation der unbekannten Funktion, beruht, gezeigt. Indirekte Methoden zur Lösung von S. I. G. können durch Anwendung derselben numerischen Regel an der Fredholmschen Integralgleichung, auf welche die S. I. G. reduziert wird, erhalten werden. In diesem Artikel wurde gezeigt, daß beide Methoden, im Sinne, daß sie dieselben numerischen Resultate liefern, äquivalent sind. Schließlich wurde mit Hilfe dieser Resultate der, Fehler und die Konvergenz der Methoden festgestellt.
    Notes: Abstract Direct methods for solving Cauchy-type singular integral equations (S.I.E.) are based on Gauss numerical integration rule [1] where the S.I.E. is reduced to a linear system of equations by applying the resulting functional equation at properly selected collocation points. The equivalence of this formulation with the one based on the Lagrange interpolatory approximation of the unknown function was shown in the paper. Indirect methods for the solution of S. I. E. may be obtained after a reduction of it to an equivalent Fredholm integral equation and an application of the same numerical technique to the latter. It was shown in this paper that both methods are equivalent in the sense that they give the same numerical results. Using these results the error estimate and the convergence of the methods was established.
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    Computing 27 (1981), S. 113-121 
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    Description / Table of Contents: Zusammenfassung Es wird eine Verallgemeinerung, der Methode von Walker für den Fall kontinuierlicher Verteilungen präsentiert. Die vorgeschlagene Methode arbeitet nach dem Rückweisungsverfahren, verwendet aber alle erzeugten Zufallswerte. Die Anwendung des Verfahrens auf den Generator für normalverteilte Zufallszahlen nach Kinderman und Ramage ergibt einen Algorithmus, der zum Algorithmus FL5 von Ahrens und Dieter äquivalent ist.
    Notes: Abstract A generalization of the Walker's method is presented for the case of continuous distributions. The proposed method is similar to the rejection technique but makes use of all the generated values. Application of the method for a normal random number generator of Kinderman and Ramage resulted in an algorithm that is equivalent to the FL5 procedure of Ahrens and Dieter.
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  • 98
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    Computing 27 (1981), S. 137-144 
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    Description / Table of Contents: Zusammenfassung Es wird eine Modifikation des Krawczyk-OperatorsK(X) zur Einschließung von Lösungen nichtlinearer Gleichungssysteme behandelt. Wenn für mindestens eine Komponentei die EinschließungK i (X)⊂int (X i ) gilt, kann der OperatorK(X) verbessert werden. Außerdem wird das verbesserte Verfahren mit anderen Modifikationen verglichen.
    Notes: Abstract A variation of the Krawczyk operator for including the solutions of a nonlinear system is introduced here. It improves the Krawczyk operatorK (X) wheneverK i (X)⊂int (X i ) for somei. A comparison with other variations is also given.
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    Computing 27 (1981), S. 145-154 
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    Description / Table of Contents: Zusammenfassung Diskutiert wird das diskrete Maximumprinzip für Finite-Element-Approximationen von elliptischen Standardproblemen in der Ebene. Schon im Fall Δu=0 treten bei stückweise quadratischen Elementen Verletzungen einer leicht verschärften Version des Prinzips auf, außer in einigen ganz speziellen Triangulierungsgeometrien.
    Notes: Abstract The discrete maximum principle for finite element approximations of standard elliptic problems in the plane is discussed. Even in the case Δu=0 a slightly stronger version of the principle does not hold with piecewise quadratic elements for all but some very special triangularisation geometries.
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  • 100
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    Computing 27 (1981), S. 205-215 
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    Description / Table of Contents: Zusammenfassung Bekanntlich erfordert die Berechung des Produkts zweier komplexer ZahlenX+iY undU+iV genau 3 reellem/d. In dieser Arbeit wird die algebraische Komplexität einiger anderer Operationen aus dem Bereich der komplexen Arithmetik untersucht. Zum Beispiel zeigen wir, daß die Inversion komplexer Zahlen genau 4 und die Division mindestens 5 reellem/d erfordert. Für das zweite Problem ist 6 als obere Schranke bekannt, so daß die genaue Komplexität der Division ein offenes Problem bleibt. Die Beweise benützen einige Kriterien, die auch allgemein für Komplexitätsbetrachtungen über fest vorgegebene Mengen rationaler Funktionen von Nutzen sein könnten.
    Notes: abstract It is well-known that the product of two complex numbersX+iY andU+iV requires exactly 3 realm/d. We study the algebraic complexity of several other operations from the repertoire of complex arithmetic. We show, for instance, that complex inversion requires exactly 4m/d and that general complex division requires at least 5m/d. For the latter problem an upperbound of 6m/d is known, leaving some speculation as to its precise complexity. The proofs illustrate several criteria which may be of more general use in assessing the complexity of concrete sets of rational functions.
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