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  • 1
    Digitale Medien
    Digitale Medien
    Numerical aspects of the generalized CG-method applied to least squares problems (1989)
    Springer
    Computing 41 (1989), S. 171-178 
    Details
    ISSN: 1436-5057
    Schlagwort(e): 65 F 10 ; 65 N 20 ; The Generalized Conjugate Gradient (GCG) method ; The adjusted GCG (AGCG) method ; SOR method ; Conjugate Gradient (CG) method and least squares (LS) problems
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die verallgemeinerte Methode der konjugierten Gradienten (GCG) von Concus und Golub [1] und Widlund [2] und ihre angepaßte Form (AGCG) werden bei der numerischen Lösung von Least-Squares-Problemen untersucht. Einige numerische Vergleiche mit dem SOR-Verfahren [3] und dem CG-Verfahren [4] werden gezogen und deuten an, daß die GCG-Methode stets besser als die SOR-Methode ist und daß das AGCG-Schema allen anderen erwähnten Methoden vorzuziehen ist.
    Notizen: Abstract The Generalized Conjugate Gradient (GCG) method of Concus and Golub [1] and Widlund [2] and its adjusted form (AGCG) are considered for the numerical solution of the least squares problems. Some numerical comparisons with the SOR [3] and CG [4] method are also given indicate that the GCG method is always better than the SOR [3] and that the adjusted GCG (AGCG) scheme is preferable to the CG, GCG and SOR methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02238742
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  • 2
    Digitale Medien
    Digitale Medien
    Error study on numerical approximation of radiation boundary condition for one-dimensional wave equation (1993)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 9 (1993), S. 475-482 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The radiation boundary condition is frequently used at the artificial outflow boundary created in the numerical computation of fluid flow problems to allow outgoing waves to leave the domain undisturbed. However, the numerical approximation of the radiation boundary condition will produce errors which will affect the interior solution. In this work the errors due to two different numerical approximations of the radiation boundary condition are studied, with the one-dimensional wave equation being used as the model equation. A theoretical analysis shows that: (a) if the numerical approximation of the boundary condition generates a celerity error, a reflected wave with amplitude proportional to the size of the celerity error is produced; (b) if the numerical approximation of the boundary condition generates a numerical diffusion and hence an amplitude damping error, a reflected wave with amplitude proportional to the magnitude of the numerical diffusion is produced. A modification of the Sommerfeld radiation boundary condition to account for the linear bottom friction effect is investigated. Numerical experiments show that the use of the backward characteristics scheme with quadratic interpolation is able to reduce significantly the reflection of the wave at the outflow boundary and that the scheme is unconditionally stable.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640090604
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  • 3
    Digitale Medien
    Digitale Medien
    The selection of a stable rat hepatoma variant with concomitant increase in ploidy and permeability to glycerol (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 94 (1978), S. 197-203 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: By repeated selection for longer survival in an isotonic solution of glycerol, a stable subline of Novikoff rat hepatoma cells has been isolated. The cells exhibit markedly increased resistances to osmotic lysis in isotonic solutions of glycerl. They are twice as large and have twice as many chromosomes as cells of the parental line. It is suggested that the osmotic stress procedure can be extended for the selection of numerous kinds of mutants and can be used as a method of analysis of membrane properties.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040940209
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  • 4
    Digitale Medien
    Digitale Medien
    Factors affecting the generation of mast cells from multipotential colony-forming cells (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 121 (1984), S. 167-173 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The cells responsible for the long-term in vitro generation of murine mast cells have been examined. Sequential analysis of all colony types obtained from cultures of spleen or bone marrow cells showed that only colonies derived from multipotential cells (mixed-erythroid colonies) or mast cell progenitors, contained cells responsible for mast cell generation in liquid cultures. Primary colony growth and subsequent maintenance of mast cells in liquid cultures was dependent upon pokeweed mitogen-stimulated spleen cell-conditioned medium (SCM). Mixed-erythroid colonies from 14-day cultures of spleen cells had the greatest capacity for mast cell generation. Analysis by clone splitting and transfer to high (20%) and low (2.5%) concentrations of SCM showed that the concentration of SCM used in either the primary colony culture or subsequent liquid culture phase altered both the proliferative capacity of the mast cells generated and the frequency of mast cell progenitors within individual mixed-erythroid colonies. Thus, mixed-erythroid colonies stimulated with 2.5% SCM contained the highest proportion of mast cell progenitors (34% of colonies) and when stimulated with 20% SCM, approximately fourfold higher numbers of mast cells were produced at weekly intervals from liquid cultures maintained in 2.5% SCM compared to parallel liquid cultures containing 20% SCM. These studies confirm the hemopoietic origin of mast cells and demonstrate that a factor(s) in SCM is able to modulate their proliferative potential.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041210121
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  • 5
    Digitale Medien
    Digitale Medien
    The D1/2-norm of the SOR and Cyclic Chebyshev Semi-Iterative (CCSI) methods for a class of non-symmetric matrices (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 547-557 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The Successive Overrelaxation (SOR) and the Cyclic Chebyshev Semi-Iterative (CCSI) methods are considered for solving the non-symmetric linear systems Ax = b when A has the form \documentclass{article}\pagestyle{empty}\begin{document}$$ {\bf A} = \left({\begin{array}{*{20}c} {{\bf D}_1} & {\bf F} \\ {-{\bf F}^{\rm T}} & {{\bf D}_{\rm 2}}\\ \end{array}} \right) $$\end{document} with D1 and D2 symmetric positive definite (SPD).The D1/2-norms of both methods are determined and it is shown that, though the SOR method is better based on the spectral radius, the CCSI scheme is far better than SOR according to the D1/2-norm.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270308
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  • 6
    Digitale Medien
    Digitale Medien
    Least-squares characteristics and finite elements for advection-dispersion simulation (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1343-1358 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The method of characteristics is combined with the method of least-squares to solve the advection equation within the finite element framework. Fourier mode analysis shows that the numerical scheme is stable and accurate even when a linear basis function is used. However, in practical application, the involvement of using numerical quadrature in this method can produce numerical instability, depending on the value of the Courant number used. It is found that using C1 continuous Hermitian cubic basis functions in the scheme reduces the degree of instability significantly and produces high accuracy. When being used in a split-operator approach, this method combines naturally with the standard finite element method and results in a highly accurate scheme for advection-dispersion simulation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620290615
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  • 7
    Digitale Medien
    Digitale Medien
    Evidence concerning the morphogenesis of saccular receptors in the bullfrog (Rana catesbeiana)Research sponsored by the Joint Services Electronics Program, Contract F44620-71-C-0087 and the United States Public Health Service, National Institute of Health, grant GM-17523-02. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 351-361 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: A dichotomy of hair-cell types has been found in the bullfrog sacculus, and considerable evidence supports the view that one type (“peripheral”) is transformed during macular growth to the other type (“central”). Between the periphery and the center of the macula, one finds a gradation of form from “peripheral” to “central” type. Occasionally in adults and more often in stage-26 tadpoles one finds the presumably younger peripheral type of hair cell occurring well beyond the limits of the macula proper. The apparent morphogenic sequence for saccular hair cells is (1) development of a kinocillum on an endolymphatic epithelial cell, (2) gradual transformation of microvilli into stereocilia, (3) growth of the stereocilia and development of kinociliary bulb, (4) achievement of final size and form.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051390305
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  • 8
    Digitale Medien
    Digitale Medien
    Efficient higher-order backward characteristics schemes for transient advection (1994)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 19 (1994), S. 997-1012 
    Details
    ISSN: 0271-2091
    Schlagwort(e): Advection ; Method of characteristics ; Finite difference ; Flux limiter ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: The use of the highest-order ((N - 1)th-order) Lagrangian interpolation Polynomial for the approximation of the exact solution in the backward characteristics scheme with N nodes is inefficient owing to the excessive number of terms in the polynomial. New schemes based on a combination of lower-order polynomials to approximate the exact solution are developed, with the relative weighting of the polynomials determined by Fourier mode analysis. With the addition of a flux limiter and a modified discriminator, the resulting schemes are oscillation-free, highly accurate, efficient and more cost-effective as compared with those schemes using the highest-order Lagrangian polynomial.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/fld.1650191104
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  • 9
    Digitale Medien
    Digitale Medien
    A PARALLEL COMPUTING SOLUTION OF HEAT AND MOISTURE TRANSFER IN UNSATURATED SOIL (1996)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 3793-3808 
    Details
    ISSN: 0029-5981
    Schlagwort(e): parallel computers ; parallel software ; finite difference ; heat and moisture transfer ; unsaturated soil ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: New parallel software for the analysis of coupled heat and moisture transfer in unsaturated soil is developed. The model, written in a two-dimensional polar co-ordinate formulation, is based on a finite difference self-implicit method. The code is programmed in FORTRAN with message passing libraries PARMACS and executed on a ‘Paramid’ parallel supercomputer. The validity of the parallel code by comparison of simulation results with experimentally measured values obtained from a laboratory heating experiment is examined. An assessment of the algorithm's performance on a large network of processors is also explored. It was found that the simulation results compared very well with the experimental measurements. The efficiency of the parallel code was also revealed leading to the conclusion that the algorithm was highly efficient in nature. The new parallel code was also found to be more efficient when dealing with larger problems requiring more finite difference nodal points, on a larger network of processors.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    NUMERICAL INVESTIGATION OF TURBULENT SHALLOW RECIRCULATING FLOWS BY A QUASI-THREE-DIMENSIONAL k-∊MODEL (1996)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 485-501 
    Details
    ISSN: 0271-2091
    Schlagwort(e): shallow recirculating flow ; multilayer model ; turbulence model ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A quasi-three-dimensional multilayer k- ∊ model has been developed to simulate turbulent recirculating flows behind a sudden expansion in shallow waters. The model accounts for the vertical variation in the flow quantities and eliminates the problem of closure for the effective stresses resulting from the depth integration of the non-linear convective accelerations found in the widely used depth- integrated models. The governing equations are split into three parts in the finite difference solution: advection, dispersion and propagation. The advection part is solved using the four-node minimax-characteristics method. The dispersion and propagation parts are treated by the central difference method, the former being solved explicitly and the latter implicitly using the Gauss-Seidel iteration method. The relative effect of bed-generated turbulence and transverse shear-generated turbulence on the recirculating flow has been studied in detail. In comparison with the results computed by the depth-integrated k-∊ model, the results computed by the present model are found to be closer to the reported data.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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