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  • Numerical Methods and Modeling  (5)
  • Wiley-Blackwell  (5)
  • National Academy of Sciences
  • American Geophysical Union (AGU)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 2891-2909 
    ISSN: 0029-5981
    Keywords: C++ ; object-oriented ; solidification ; parallel ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper describes an implementation in C++ and in parallel of an explicit finite element formulation for the solution of transient heat conduction problems with phase change. The scheme requires a very small timestep because of its conditional stability, but, as no matrix inversion is required, the cost per timestep is an order of magnitude lower than for a conventional scheme.The principles of using object-oriented techniques for general finite element programming are briefly explained, while the advantages for parallel processing are described in detail, including the classes used to perform message passing.An example is given showing the performance of the scheme on two completely different parallel machines: a shared memory Silicon Graphics Power Challenge, and a distributed memory Cray T3D. The results indicate that the program scales efficiently for large meshes. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 3405-3419 
    ISSN: 0029-5981
    Keywords: finite element formulations ; semiconductor equations ; upwinding schemes ; time integration methods ; interpolation functions ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A number of transient and steady-state finite element formulations of the semiconductor drift-diffusion equations are studied and compared with respect to their accuracy and efficiency on a simple test structure (the Mock diode). A new formulation, with a consistent interpolation function used to represent the electron and hole carrier densities throughout the set of semiconductor drift-diffusion and Poisson's equations, is introduced. Results highlight the advantages in using consistent interpolation functions showing an increased accuracy in the calculated values and a saving in data storage and execution time. The results also illustrate how the use of different time integration methods affect the number of time steps required during transient simulations. The combination of the fully consistent DFUS with appropriate time integration methods is found to yield a saving of up to 80 per cent of the execution time required for standard spatial/temporal discretization techniques. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 42 (1998), S. 1091-1119 
    ISSN: 0029-5981
    Keywords: transient dynamics ; direct integration ; subcycling ; diffusion problems ; structural dynamics ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Subcycling algorithms which employ multiple timesteps have been previously proposed for explicit direct integration of first- and second-order systems of equations arising in finite element analysis, as well as for integration using explicit/implicit partitions of a model. The author has recently extended this work to implicit/implicit multi-timestep partitions of both first- and second-order systems. In this paper, improved algorithms for multi-timestep implicit integration are introduced, that overcome some weaknesses of those proposed previously. In particular, in the second-order case, improved stability is obtained. Some of the energy conservation properties of the Newmark family of algorithms are shown to be preserved in the new multi-timestep extensions of the Newmark method. In the first-order case, the generalized trapezoidal rule is extended to multiple timesteps, in a simple way that permits an implicit/implicit partition. Explicit special cases of the present algorithms exist. These are compared to algorithms proposed previously. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 13 (1997), S. 249-260 
    ISSN: 1069-8299
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The super-time-stepping algorithm is an improved timestepping scheme. It can significantly increase the performance of explicit methods, by reducing the restrictive timestep limits that exist. One of the drawbacks of the method is that the improvements are dependent on a set of parameters which are generally unknown. An investigation is performed to find the effect of these parameters and a method is described that estimates them. The technique is applied to a real problem and the results show a considerable improvement over a standard explicit timestepping scheme. The technique is implemented in an object-oriented manner, and details are given in an Appendix. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 2841-2855 
    ISSN: 0029-5981
    Keywords: transient ; structural dynamics ; explicit integration ; subcycling ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm for explicit integration of structural dynamics problems with multiple time steps is proposed that averages accelerations to obtain subcycle states at a nodal interface between regions integrated with different time steps. With integer time step ratios, the resulting subcycle updates at the interface sum to give the same effect as a central difference update over a major cycle. The algorithm is shown to have good accuracy, and stability properties in linear elastic analysis similar to those of constant velocity subcycling algorithms. The implementation of a generalised form of the algorithm with non-integer time step ratios is presented. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
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