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  • Artikel  (13)
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  • numerical simulation
  • optimization
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  • Artikel  (13)
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  • Springer  (13)
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  • American Institute of Physics (AIP)
  • American Physical Society
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Erscheinungszeitraum
  • 1995-1999
  • 1990-1994  (13)
  • 1955-1959
  • 1945-1949
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Thema
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 52 (1991), S. 11-17 
    ISSN: 1436-4646
    Schlagwort(e): Modeling ; cancer ; optimization ; optimal control ; drug delivery
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract In this paper we consider the problems of modeling the tumor growth and optimize the chemotherapy treatment. A biologically based model is used with the goal of solving an optimization problem involving discrete delivery of antineoplastic drugs. Our model is formulated via compartmental analysis in order to take into account the cell cycle. The cost functional measures not only the final size of the tumor but also the total amount of drug delivered. We propose an algorithm based on the discrete maximum principle to solve the optimal drug schedule problem. Our numerical results show nice interpretations from the medical point of view.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 51 (1991), S. 169-197 
    ISSN: 1572-9478
    Schlagwort(e): asteroid belt ; secular resonance ; action angle variables ; surface of section ; numerical simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper an analytical model, suitable for a global description of the dynamics in a secular resonance of order 1, is derived from the general perturbation study developed in a previous paper (Morbidelli and Henrard (1991)). Such a model is then used to study the secular resonances ν6, ν5 and ν16, and pictures illustrating the secular motion are obtained. The peculiarities of the ν5 resonances are discussed in detail. The results are compared with those obtained by the theories of Yoshikawa and Nakai-Kinoshita. Some numerical simulations performed by Ch. Froeschlé and H. Scholl are discussed in the light of the new theoretical results. New numerical experiments on the ν6 resonance are also presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Computing 47 (1991), S. 29-42 
    ISSN: 1436-5057
    Schlagwort(e): 65K05 ; Interval Newton method ; interval arithmetic ; optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Arbeit entwickelt ein optimales Intervall-Newton-Verfahren für Systeme von nichtlinearen Gleichungen, wie sie im Zusammenhang mit nichtlinearen Optimierungsaufgaben auftreten. Die Modifikationen des Intervall-Newton-Verfahrens in dieser Arbeit stellen numerisch wirkungsvolle Verbesserungen des allgemeinen Intervall-Newton-Verfahrens dar. In der Arbeit wird aufgezeigt, daß die Berechnung einer optimalen Schrittweite im Intervall-Newton-Verfahren notwendig ist, damit man die Generierung einer feiner werdenden Einschließungsfolge garantieren kann. Dieses Vorgehen wird als optimales Newton-Verfahren bezeichnet und für den mehrdimensionalen Fall implementiert. Die Arbeit zeigt dann die Verwendung des optimalen Intervall-Newton-Verfahrens als “feasible direction”-Verfahren im Zusammenhang mit Nichtnegativitätsbedingungen. In der Implementierung wird auch eine Technik der Matrizenzerlegung verwendet, die den Rechenaufwand für die Inverse der Hesseschen Matrix im Intervall-Newton-Verfahren vermindert. Das Vorgehen wird an mehreren Beispielen demonstriert, u.a. an Optimierungsaufgaben mit Störungen der Problemkoeffizienten. Die numerischen Ergebnisse bestätigen die Leistungsfähigkeit unserer Ansätze.
    Notizen: Abstract This paper presents the development of an optimal interval Newton method for systems of nonlinear equations. The context of solving such systems of equations is that of optimization of nonlinear mathematical programs. The modifications of the interval Newton method presented in this paper provide computationally effective enhancements to the general interval Newton method. The paper demonstrates the need to compute an optimal step length in the interval Newton method in order to guarantee the generation of a sequence of improving solutions. This method is referred to as the optimal Newton method and is implemented in multiple dimensions. Secondly, the paper demonstrates the use of the optimal interval Newton method as a feasible direction method to deal with non-negativity constraints. Also, included in this implementation is the use of a matrix decomposition technique to reduce the computational effort required to compute the Hessian inverse in the interval Newton method. The methods are demonstrated on several problems. Included in these problems are mathematical programs with perturbations in the problem coefficients. The numerical results clearly demonstrate the effectiveness and efficiency of these approaches.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    The journal of supercomputing 5 (1991), S. 31-48 
    ISSN: 1573-0484
    Schlagwort(e): C language ; numerical computing ; Fortran ; data type ; floating point arithmetic ; optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract The predominant programming language for numerical and scientific applications is Fortran, and super-computers are primarily used to run large-scale numerical and scientific applications. C is not widely used for numerical and scientific programming, yet C provides many desirable linguistic features not present in Fortran-77. Furthermore, the existence of a standard library and preprocessor eliminates the worst portability problems. A comparison of C and Fortran-77 shows several key deficiencies in C that reduce its desirability for some numerical problems. Some of these problems have already been addressed by the new ANSI standard for C, but others remain. C with a few extensions and modifications could be suitable for all numerical applications and could become more popular in supercomputing environments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Natural hazards 4 (1991), S. 235-255 
    ISSN: 1573-0840
    Schlagwort(e): The 1960 Chilean tsunami ; numerical simulation ; Imamura number ; difference between farand near-field tsunamis ; sea-bottom scouring ; damage to aquaculture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract The 1960 Chilean tsunami which traveled the Pacific Ocean and caused much damages to Japan is simulated from its generation to the terminal effects on coastal areas. In the computation of ocean propagation by the linear longwave theory, a new technique is introduced to keep the same accuracy as the linear Boussinesq equation and reduce the CPU time as well as the computer memory. In the coastal transformation computation, the energy dissipation due to sea-bottom scouring is suggested to be included, particularly in the case of long bays. To obtain accurate results, the current velocity requires finer spatial grids than the water surface elevation. Damage done to pearl culture rafts are explained in terms of the computed current velocity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Machine vision and applications 4 (1991), S. 59-87 
    ISSN: 1432-1769
    Schlagwort(e): optimization ; feature extraction ; minimal encoding ; generic models
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract In this paper, we propose a unified optimization framework for feature extraction that lets us simultaneously take into account image data and semantic knowledge: We model objects using a language that specifies both photometric and geometric constraints and defines an information-theoretic objective function that measures the fit of the models to the data. We then treat the problem of finding objects as one of generating the optimal description of the image in terms of this language. We have validated our framework by performing extensive experiments on detecting objects in aerial imagery described by simple geometric constraints and have developed two algorithms for generating optimal descriptions. The first one starts with a rough sketch of a polygonal object and deforms the initial contour to maximize the objective function, thus finding object outlines. The second one automatically extracts complex rectilinear buildings from complex aerial images.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Acta mechanica Sinica 7 (1991), S. 243-250 
    ISSN: 1614-3116
    Schlagwort(e): damage and fracture model ; fracture initiation and crack propagation ; large elastic-plastic deformation ; numerical simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A unified damage and fracture model, the combinatory work density model, which is suitable for either non-cracked body or cracked body has been suggested[t−7]. In the present paper, the deformation and fracture of the two kinds of tensile spceimen and TPB specimen made of 40Cr steel have been simulated by using the new model together with the large elastic-plastic deformation finite element method. The results give a good picture of the whole deformation and fracture processes of the specimens in experiments; especially, the results on the TPB specimen can be used to obtain the relationship between load and displacement at the loading pointP-Δ, and between crack extension and displacement at the loading point Δa-Δ, the resistance curveJ R -Δa and the fracture toughnessJ 1C . All the results are in remarkable agreement with those obtained by experiments. Therefore the model suggested here can be used to simulate crack initiation and propagation in non-cracked body and fracture initiation and crack stable propagation in cracked body.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Applied mathematics and mechanics 12 (1991), S. 1-11 
    ISSN: 1573-2754
    Schlagwort(e): Newtonian fluid ; non-Newtonian fluid ; turbulent flows ; numerical simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract Using k-ε model of turbulence and measured wall functions, turbulent flows of Newtonian (pure water) and a sort of non-Newtonian fluid (dilute, drag-reduction solution of polymer) in a 180-degree curved bend were simulated numerically. The calculated results agreed well with the measured velocity profiles. On the basis of calculation and measurement, appropriateness of turbulence model to complicated flow in which the largescale vortex exists was analyzed and discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Computational economics 4 (1991), S. 15-31 
    ISSN: 1572-9974
    Schlagwort(e): Hill-climbing ; maximum likelihood estimation ; non-linear least squares ; optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Wirtschaftswissenschaften
    Notizen: Abstract This article describes EZClimb, a set of SAS/IML steps useful in solving numerical optimization problems. The program uses the method of modified quadratic hill-climbing with either analytical or numerical derivatives to maximize a user-defined criterion function. Modified quadratic hill-climbing is one of the more powerful algorithms known for function optimization but is not widely available outside of the software package GQOPT. The efficacy of the SAS steps is illustrated using Rosenbrock's function, Savin and White's Box-Cox extended autoregressive model, and Klein's Model I.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Water resources management 4 (1991), S. 251-271 
    ISSN: 1573-1650
    Schlagwort(e): Reservoir operation ; treatment of imprecision ; optimization ; satisficing ; fuzzy sets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie
    Notizen: Abstract Many modifications, extensions, discussions, and evaluations of chance-constrained reservoir operating models have been reported in the technical literature. Lack of economic data and the fact that the establishment of acceptable risk levels in these types of models involves a human factor with all its vagueness of perception, subjectivity, and attitudes may not permit proper application of either reliability or multiobjective programming approaches. This paper presents a unique methodology for handling a practical problem of selecting risk levels in chance-constrained reservoir operation modeling. The proposed methodology is based on fuzzy set theory. Two types of fuzzy sets are used in the formulation of the reservoir long-term planning model, one for constraints and one for the objective function. An iterative solution algorithm for deriving an optimal decision using fuzzy set operations and the chance-constrained approach is developed and presented. A practical application of the approach demonstrates the feasibility and efficiency of both the proposed approach and its iterative search procedure for selecting risk levels in chance-constrained reservoir modeling.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 6 (1991), S. 519-547 
    ISSN: 1573-1634
    Schlagwort(e): Heterogeneous porous media ; two-phase flow ; numerical simulation ; finite element method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract A mathematically rigorous method of homogenization is presented and used to analyze the equivalent behavior of transient flow of two incompressible fluids through heterogeneous media. Asymptotic expansions and H-convergence lead to the definition of a global or effective model of an equivalent homogeneous reservoir. Numerical computations to obtain the homogenized coefficients of the entire reservoir have been carried out via a finite element method. Numerical experiments involving the simulation of incompressible two-phase flow have been performed for each heterogeneous medium and for the homogenized medium as well as for other averaging methods. The results of the simulations are compared in terms of the transient saturation contours, production curves, and pressure distributions. Results obtained from the simulations with the homogenization method presented show good agreement with the heterogeneous simulations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 6 (1991), S. 479-499 
    ISSN: 1573-1634
    Schlagwort(e): Multiphase flow ; numerical simulation ; viscous fingering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract The ability to numerically simulate single phase and multiphase flow of fluids in porous media is extremely important in developing an understanding of the complex phenomena governing the flow. The flow is complicated by the presence of heterogeneities in the reservoir and by phenomena such as diffusion, dispersion, and viscous fingering. These effects must be modeled by terms in coupled systems of nonlinear partial differential equations which form the basis of the simulator. The simulator must be able to handle both single and multiphase flows and the transition regimes between the two. A discussion of some of the aspects of modeling dispersion and viscous fingering is presented along with directions for future work. The partial differential equation models are convection-dominated and contain important local effects. An operator-splitting technique is used to address these different effects accurately. Convection is treated by time stepping along the characteristics of the associated pure convection problem, and diffusion is modeled via a Galerkin method for single phase flow and a Petrov-Galerkin technique for multiphase regimes. ELLAM (Eulerian-Lagrangian Localized Adjoint Methods) are discussed to effectively treat the advection-dominated processes. Accurate approximations of the fluid velocities needed in the Eulerian-Lagrangian time-stepping procedure are obtained by mixed finite element methods. Adaptive local grid refinement techniques are then indicated to resolve important local phenomena around wells and large heterogeneities or to resolve the moving internal boundary layers which often govern the mass transfer between phases.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 64 (1991), S. 755-779 
    ISSN: 1572-9613
    Schlagwort(e): Neural networks ; associative memory ; hierarchically correlated patterns ; statistical mechanics of Ising systems ; replica formalism ; numerical simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A class of hierarchical neural network models introduced by Dotsenko for the storage and associative recall of strongly correlated memories is studied analytically and numerically. In these models, patterns stored in higher levels of the hierarchy represent generalized categories and those stored in lower levels describe finer details. We first show that the models originally proposed by Dotsenko have a serious flaw: they are not able to detect or correct errors in categorization which may be present in the input. We then describe three different models which attempt to overcome this shortcoming of the original models. In the first model, the interaction between different levels of the hierarchy has the form of an external field conjugate to memories stored in the lower level. In the second model, a three-spin interaction term is included in addition to the usual binary interactions of the Hopfield type. The third model makes use of a time delay mechanism to induce, if necessary, transitions between memory states and their complements. Detailed analytical and numerical studies of the performance of these models are presented. Our analysis shows that all three models are able to detect and also to correct in varying degrees any error in categorization that may be present in the input pattern.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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