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  • Articles  (19)
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  • Articles  (19)
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  • Springer  (19)
  • American Chemical Society
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Computing 29 (1982), S. 373-380 
    ISSN: 1436-5057
    Keywords: 68C25 ; 68C20 ; Analysis of algorithms ; computational complexity ; cost complexity ; Ruffini-Horner method ; polynomial evaluation ; polynomial translation ; computer algebra ; unlimited precision arithmetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die Verminderung der Zahl der Multiplikationen bei der Berechnung eines Polynoms und seinen Ableitungen bringt nicht unbedingt eine entsprechende Verminderung der gesamten Berechnungskosten. In dieser Arbeit werden Kosten-Analysen einer Algorithmen-Familie vorgestellt, die alle Ableitungen eines Polynoms mit 3n−2 Multiplikationen oder Divisionen berechnet. Dies repräsentiert eine Verbesserung im Vergleich mit den klassischen Methoden, die 1/2n(n+1) Multiplikationen benötigen. Jedoch offenbart die Analyse die Gegenwart eines Ausgleichs zwischen den Kosten der Multiplikationen bzw. Divivionen und den übrigen Kosten. Dadurch bleibt die Komplexität für alle AlgorithmenO(ξ2 n 3), wie stark auch immer die Verminderung der Zahl der arithmetischen Operationen ist.
    Notes: Abstract Reducing the number of multiplications for the evaluation of a polynomial and its derivatives does not necessarily mean that one should expect a commensurate reduction of the total cost of computation. In this paper we present a cost analysis for a family of algorithms, which computes all derivatives of a polynomial in 3n−2 multiplications or divisions. This represents an improvement over the classical methods, which require 1/2n(n+1) multiplications. The analysis, however, reveals the presence of a multiplications-divisions cost trade-off due to which the cost complexity remainsO(ξ2 n 3) for all algorithms irrespective of any reduction in the number of arithmetic operations.
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  • 2
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    Springer
    Mathematical programming 23 (1982), S. 181-192 
    ISSN: 1436-4646
    Keywords: Linear Complementarity Problem ; Stability ; Classes of Matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It has been shown previously that the Linear Complementarity Problem is stable when the defining matrix is positive semidefinite and when (locally) the set of solutions is nonempty and bounded. We enlarge the class of matrices for which this is true and also demonstrate how the boundedness condition leads to other stability type questions.
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  • 3
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    Computing 29 (1982), S. 11-29 
    ISSN: 1436-5057
    Keywords: 68C25 ; 68E99 ; Binary search trees ; height-balanced trees ; AVL trees ; weight-balanced trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Eine Methode, die von Yao formuliert und von Brown angewendet wurde, gestattet es, schranken für den Anteil von Knoten mit bestimmten Eigenschaften in Bäumen anzugeben, die durch eine Folge von zufälligen Einfügungen entstehen. Für den Fall von AVL-Bäumen (höhenbalanziert) zeigen wird, daß solche Methoden nicht erweitert werden können, um bessere Schranken als die bisher bekannten zu berechnen. Dann wenden wir diese Methode auf gewichtsbalanzierte Bäume und auf eine Art von “schwach balanzierten” Bäumen an und bestimmen die Verteilung der gewichtsbalanzierten Faktoren der inneren Knoten in einem Zufallsbaum, der durch binäre Suche und Einfügen entsteht; ferner zeigen wir, daß in einem solchen Baum ungefähr 72% der inneren Knoten gewichtsbalanzierte Faktoren zwischen $$1 - \sqrt 2 /2$$ und $$\sqrt 2 /2$$ haben.
    Notes: Abstract A method formulated by Yao and used by Brown has yielded bounds on the fraction of nodes with specified properties in trees bult by a sequence of random internal nodes in a random tree built by binary search and insertion, and show that in such a tree about bounds better than those now known. We then apply these methods to weight-balanced trees and to a type of “weakly balanced” trees. We determine the distribution of the weight-balance factors of the internal nodes in a random tree built by binary search and insertion and show that in such a tree about 72% of all internal nodes have weight balance factors lying between $$1 - \sqrt 2 /2$$ and $$\sqrt 2 /2$$ .
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  • 4
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    Computing 29 (1982), S. 227-239 
    ISSN: 1436-5057
    Keywords: 68C25 ; Bin packing ; approximation algorithms ; stochastic algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Beim eindimensionalen Packungsproblem besteht die Aufgabe darin, eine Liste vonn Eingabegrößen in möglichst wenige “Behälter” der Höhe 1 zu packen. Es wird eine Klasse von linearen Online-Algorithmen zur näherungsweisen Lösung des Packungsproblems mit Eingabegrößen, die einer bekannten Wahrscheinlichkeitsverteilung unterliegen, vorgestellt. Jeder dieser Algorithmen hängt von der Wahrscheinlichkeitsverteilung und einem Parameter ab, der die Güte des Algorithmus beeinflußt. Es wird gezeigt, daß sich der Erwartungswert der relativen Packungsdichte bei wachsender Anzahl der Eingabegrößen beliebig dicht dem Optimum nähert.
    Notes: Abstract In the one-dimensional bin packing problem a list ofn items has to be packed into a minimum number of unit-capacity bins. A class of linear online algorithms for the approximate solution of bin packing with items drawn from a known probability distribution is presented. Each algorithm depends on the distribution and on a parameter controlling the performance of the algorithm. It is shown that with increasing number of items the expected performance ratio has an arbitrary small deviation from optimum.
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  • 5
    ISSN: 1572-9125
    Keywords: 65G05 ; 65D05 ; 68C25 ; 65D99 ; Evaluation of polynomials ; Lagrange form of a polynomial ; error analysis ; error norm ; numerical stability ; Lebesgue constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract For evaluation schemes based on the Lagrangian form of a polynomial with degreen, a rigorous error analysis is performed, taking into account that data, computation and even the nodes of interpolation might be perturbed by round-off. The error norm of the scheme is betweenn 2 andn 2+(3n+7)λ n , where λ n denotes the Lebesgue constant belonging to the nodes. Hence, the error norm is of least possible orderO(n 2) if, for instance, the nodes are chosen to be the Chebyshev points or the Fekete points.
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  • 6
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    Numerische Mathematik 40 (1982), S. 39-46 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65D15 ; CR: 5.13
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary In the univariate case the ɛ-algorithm of Wynn is closely related to the Padé-table in the following sense: if we apply the ɛ-algorithm to the partial sums of the power series $$f(x) = \sum\limits_{i = 0}^\infty {c_i x^i } $$ then ε 2m l−m is the (l, m) Padé-approximant tof(x) wherel is the degree of the numerator andm is the degree of the denominator [1 pp. 66–68]. Several generalizations of the ɛ-algorithm exist but without any connection with a theory of Padé-approximants. Also several definitions of the Padé-approximant to a multivariate function exist, but up till now without any connection with the ɛ-algorithm. In this paper, we see that the multivariate Padé-approximants introduced in [3], satisfy the same property as the univariate Padé-approximants: if we apply the ɛ-algorithm to the partial sums of the power series $$f\left( {x_1 ,...,x_n } \right) = \sum\limits_{i_1 + ... + i_n = 0}^\infty {c_{i_1 ...i_n } x_1^{i_1 } ...x_n^{i_n } } $$ then ε 2m (l−m) is the (l, m) multivariate Padé-approximant tof(x 1, ...,x n ).
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  • 7
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    Numerische Mathematik 39 (1982), S. 411-420 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65D15 ; CR: 5.13
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary We transform a complex approximation problem into an equivalent semiinfinite optimization problem whose constraints are described in terms of a quantity ϕ∈[0,2π[=I. We study the effect of disturbing the problem by replacingI by a compact subsetM⊂I which includes as special case the discrete case whereM consists only of finitely many points. We introduce a measure ɛ for the deviation ofM fromI and show that in any complex approximation problem the minimal distance of the disturbed problem converges quadratically with ɛ→0 to the minimal distance of the undisturbed problem which is a generalization of a result by Streit and Nuttall. We also show that in a linear finite dimensional approximation problem the convergence of the coefficients of the disturbed problem is in general at most linear. There are some graphical representations of best complex approximations computed with the described method.
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  • 8
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    Numerische Mathematik 40 (1982), S. 93-98 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65D15 ; CR: 5.15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Description / Table of Contents: Zusammenfassung Der Quotienten-Differenzen-Algorithmus nach Rutishauser ist geeignet zur Bestimmung von Polen meromorpher Funktionen, gegeben durch eine Taylorreihe. Sind mehrere Pole betragsgleich, so kann eine Polynomfolge bestimmt werden, deren Grenzpolynom diese Pole als Nullstellen hat. Die Konvergenz wurde von Rutishauser jedoch nicht bewiesen. Ein Beweis wird in der vorliegenden Arbeit präsentiert.
    Notes: Summary The Quotient-Difference Algorithm of Rutishauser can be used for the determination of poles of a meromorphic function given by its power series. If some of the poles have same modulus, a sequence of polynomials can be determined such that the limiting polynomial has exactly these poles as zeros. The convergence has not been proved by Rutishauser, however. A proof is presented in this paper.
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  • 9
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    Numerische Mathematik 40 (1982), S. 229-243 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65D15 ; CR: 5.13
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary This paper deals with the problem of uniqueness in one-sidedL 1-approximation. The chief purpose is to characterize finite dimensional subspacesG of the space of continuous or differentiable functions which have a unique best one-sidedL 1-approximation. In addition, we study a related problem in moment theory. These considerations have an important application to the uniqueness of quadrature formulae of highest possible degree of precision.
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  • 10
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    Numerische Mathematik 39 (1982), S. 65-84 
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65D15 ; CR: 5.13
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary The problem of finding optimal cycles in a doubly weighted directed graph (Problem A) is closely related to the problem of approximating bivariate functions by the sum of two univariate functions with respect to the supremum norm (Problem B). The close relationship between Problem A and Problem B is detected by the characterization (7.4) of the distance dist (f, t) of Problem B. In Part 1 we construct an algorithm for Problem A where the essential role is played by the minimal lengthsy j(k) defined by (2.3). If weight functiont≡1 then the minimum of Problem A is computed by equality (2.4). Ift≡1 then the minimum is obtained by a binary search procedure, Algorithm 3. In Part 2 we construct our algorithms for solving Problem B by following exactly the ideas of Part 1. By Algorithm 4 we compute the minimal pseudolengthsh k(y, M) defined by (7.5). If weight functiont≡1 then the infimum dist(f,t) of Problem B is obtained by equality (7.12) which is closely related to (2.4). Ift≢1 we compute the infimum dist(f,t) by the binary search procedure Algorithm 5. Additionally, Algorithm 4 leads to a constructive proof of the existence of continuous optimal solutions of Problem B (see Theorem 7.1e) which is already known in caset≡1 but unknown in caset≢1. Interesting applications to the steady-state behaviour of industrial processes with interference (Sect. 3) and the solution of integral equations (Problem C) are included.
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  • 11
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    Journal of mathematical biology 16 (1982), S. 49-55 
    ISSN: 1432-1416
    Keywords: Stability ; Diffusion ; Parabolic equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Models for a single species that inhabits an environment that is spatially varying are presented. Simple necessary and sufficient conditions for stability, which are independent of the exact details of the dispersal process, are developed in the case of large diffusion rates. The results highlight the important stabilizing nature of diffusion in a spatially varying environment.
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  • 12
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    Journal of mathematical biology 14 (1982), S. 71-75 
    ISSN: 1432-1416
    Keywords: Epidemiology ; Two host models ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract An epidemic model is derived for a two host infectious disease. It is shown that if a non-trivial equilibrium solution exists, it is globally stable. This result is also proved for a similar one host model.
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  • 13
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    Journal of mathematical biology 16 (1982), S. 33-48 
    ISSN: 1432-1416
    Keywords: Sterile insect release ; Predation ; Stability ; Limit cycles ; Optimal control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A model for the sterile insect release method of pest control in which the target species is under predatory or parasitic regulation is analyzed. The equations are nondimensionalized and the rescaled parameters are interpreted. There are four types of equilibria, whose existence and stability depend on which of ten regions of parameter space contain the rescaled parameters, and in turn give minimal release rates to achieve eradication of the pest. In at least one region, Hopf bifurcation theory shows the existence of limit cycles, but they are found to be unstable. In addition, the optimal release rate to minimize a total cost functional for pest control by the sterile release method is studied. Both approaches show that when predation accounts for a large fraction of the natural deaths, the necessary release rate and total cost are higher than for weak predation. If the predators are removed without being replaced by any other source of mortality, the cost rises in all cases but rises much more dramatically for cases with strong predation. A definite danger of the sterile release method when some predatory control exists is that the predators are frequently driven extinct before the prey, so that the target species could explode to much higher levels and be more difficult to eradicate again after the sterile release is terminated.
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  • 14
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    Journal of mathematical biology 12 (1982), S. 101-114 
    ISSN: 1432-1416
    Keywords: Predator-prey systems ; Harvesting ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The global behaviour of a class of predator-prey systems, modelled by a pair of non-linear ordinary differential equations, under constant rate harvesting and/or stocking of both species, is presented. Theoretically possible structures and transitions are developed and validated by computer simulations. The results are presented as transition loci in the F-G (prey harvest rate-predator harvest rate) plane.
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  • 15
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    Journal of mathematical biology 14 (1982), S. 231-250 
    ISSN: 1432-1416
    Keywords: Predator-prey ; Age structure ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A general predator-prey model is considered in which the predator population is assumed to have an age structure which significantly affects its fecundity. The model equations are derived from the general McKendrick equations for age structured populations. The existence, stability and destabilization of equilibria are studied as they depend on the prey's natural carrying capacity and the maturation periodm of the predator. The main result of the paper is that for a broad class of maturation functions positive equilibria are either unstable for smallm or are destabilized asm decreases to zero. This is in contrast to the usual rule of thumb that increasing (not decreasing) delays in growth rate responses cause instabilities.
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  • 16
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    Journal of mathematical biology 15 (1982), S. 37-50 
    ISSN: 1432-1416
    Keywords: Reaction-diffusion system ; Stationary solution ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We consider a spatial population growth process which is described by a reaction-diffusion equation c(x)u t = (a 2(x)u x ) x +f(u), c(x) 〉0, a(x) 〉 0, defined on an interval [0, 1] of the spatial variable x. First we study the stability of nonconstant stationary solutions of this equation under Neumann boundary conditions. It is shown that any nonconstant stationary solution (if it exists) is unstable if a xx⩽0 for all xε[0, 1], and conversely ifa xx〉0 for some xε[0, 1], there exists a stable nonconstant stationary solution. Next we study the stability of stationary solutions under Dirichlet boundary conditions. We consider two types of stationary solutions, i.e., a solution u 0(x) which satisfies u 0 x≠0 for all xε[0, 1] (type I) and a solution u 0(x) which satisfies u 0x = 0 at two or more points in [0, 1] (type II). It is shown that any stationary solution of type I [type II] is stable [unstable] if a xx ⩾0 [a xx ⩽0] for all xε[0, 1]. Conversely, there exists an unstable [a stable] stationary solution of type I [type II] if a xx 〈0 [a xx 〉0] for some xε[0, 1].
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  • 17
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    Journal of mathematical biology 15 (1982), S. 239-247 
    ISSN: 1432-1416
    Keywords: Predator-prey model ; Behavioral adaptation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The Volterra-Lotka predator-prey equations are modified so that the predator's ability to utilize the prey varies in proportion to the average number of encounters between the two species in the past. The behavior of this adaptive system is then described in terms of three parameters — the carrying capacity of the prey, the relative death rate of the predator, and the predator's memoryspan. The most stable situation is shown to occur when the carrying capacity of the prey is large, the predator's death rate is close to zero, and the predator is able to adapt quickly to changing levels of prey density.
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  • 18
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    Journal of mathematical biology 16 (1982), S. 25-31 
    ISSN: 1432-1416
    Keywords: Stability ; Community matrix ; Lotka-Volterra models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The explicit function of the community matrix of a three dimensional Lotka-Volterra model is delineated by a set of necessary and sufficient conditions for a positive equilibrium to be asymptotically stable. In the special case that the community matrix is quasi weakly diagonally dominant, it is shown that a positive determinant for the community matrix is not only necessary but is also sufficient for stability. The results are specific to three dimensional models and do not extend to communities of dimension greater than three.
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  • 19
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    Journal of mathematical biology 16 (1982), S. 103-112 
    ISSN: 1432-1416
    Keywords: Bifurcation ; Competition ; Diffusive Lotka-Volterra system ; Predator-prey interaction ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Three examples of the diffusive 3-species Lotka-Volterra system with constant interaction parameters are given, and by bifurcation techniques shown to have stable spatially non-constant equilibrium solutions. One example is competitive; the second one predator-two-competing prey and the third involves two predators and a single prey.
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