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  • 1
    Electronic Resource
    Electronic Resource
    An approach to optimal design of structures with non-linear response (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 36 (1993), S. 511-521 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A commonly adopted procedure to solve a structural optimum design problem is to improve the design iteratively by solving a sequence of simpler problems, where each of these is obtained as an approximation of the original problem. Considering structures with linear response, this procedure works very well and can be implemented quite straightforwardly. However, considering structures with non-linear response, the situation is more sophisticated since structural stability properties have to be taken into account.The paper presents an approach to optimal design of statically loaded structures with non-linear response. It is proposed to replace the original problem with a sequence of similar problems from which corresponding approximate problems can easily be obtained. These similar problems additionally contain an estimation of the critical load constraint while other constraints are imposed at some properly chosen load level, which is lower or at most equal to the critical load level. By this approach, the structural stability requirements are taken into account in an effective manner. The efficiency is illustrated with several examples involving kinematic as well as material non-linear effects.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620360309
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  • 2
    Electronic Resource
    Electronic Resource
    TLM modelling of diffusion, drift and recombination of charge carriers in semiconductors (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 219-225 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The paper provides an extension to the one-dimensional TLM diffusion model. The extended diffusion node presented here models the exact transport equation with diffusion drift and recombination of charge carriers in semiconductors. A general algorithm for providing a numerical solution to the transport phenomena is also presented here. The analytical solution for infinitely long semiconductors is compared with the TLM numerical results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660050403
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    New technique for finite difference analysis of optical waveguide problems (1994)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 7 (1994), S. 25-33 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The method of effective penetration depth is used to produce a novel scalar or polarized finite difference approach for the solution of optical rib waveguide field problems. The new method is quicker than previous finite difference approaches and requires less computer memory. Propagation constant values are presented for a range of semiconductor rib waveguides and are found to be indistinguishable from benchmark results produced using earlier methods of analysis. A simple polarization correction formula recently derived is confirmed by utilizing the good accuracy of these results. This enables discussion of the relationship between quasi-TE, quasi-TM and scalar modes, and a further substantial reduction of the cpu time.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660070104
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  • 4
    Electronic Resource
    Electronic Resource
    Flow development in entrance region of ducts (1993)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 9 (1993), S. 503-509 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The integral transform method is used to compute numerically the development of the velocity profile in the hydrodynamic entrance region for laminar flow inside a parallel plate channel. The results have user-prescribed accuracy and can be used to test other numerical methods.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640090608
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  • 5
    Electronic Resource
    Electronic Resource
    Transonic viscous-inviscid interaction by a finite element method (1991)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 13 (1991), S. 309-319 
    Details
    ISSN: 0271-2091
    Keywords: Viscous-inviscid interaction ; Shock wave-boundary layer interaction ; Boundary layers ; Finite element method for flow problems ; Zonal methods ; Choked viscous flows ; Stream function-vorticity formulation ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A method is outlined for solving two-dimensional transonic viscous flow problems, in which the velocity vector is split into the gradient of a potential and a rotational component. The approach takes advantage of the fact that for high-Reynolds-number flows the viscous terms of the Navier-Stokes equations are important only in a thin shear layer and therefore solution of the full equations may not be needed everywhere. Most of the flow can be considered inviscid and, neglecting the entropy and vorticity effects, a potential model is a good approximation in the flow core. The rotational part of the flow can then be calculated by solution of the potential, streamfunction and vorticity transport equations. Implementation of the no-slip and no-penetration boundary conditions at the walls provides a simple mechanism for the interaction between the viscous and inviscid solutions and no extra coupling procedures are needed. Results are presented for turbulent transonic internal choked flows.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650130304
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  • 6
    Electronic Resource
    Electronic Resource
    Optimization of mechanical systems: On strategy of non-linear first-order approximation (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 223-234 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents an extended approach to non-linear first-order approximation of non-linear programming problems and it explains how to transform an approximate problem into a strictly convex one. The essence of the proposed approximation technique is to rewrite each given function hj as a composite gj o Ψj. The function Ψj has to be chosen - the paper explains how to do this - while gj is linear approximated with gj. The approximation of hj is then obtained as gj o Ψj.This approach enables one to obtain approximate functions with variable conservativeness, which implies an adjustable approximate problem. A solution procedure, which replaces the original problem with a sequence of approximate problems, can therefore adjust each succeeding approximate problem to improve the convergence properties.The theory is illustrated with a three parameters controlled approximation. This technique represents, together with an optimality criteria based solution procedure, a powerful and economic tool for solving nonlinear programming problems. The three parameters, which influence to a great extent the conservativeness of the approximate functions, are under full control of the optimizer. They are varied automatically during the process of optimization to speed-up the convergence or to prevent oscillations.The benefits gained from the proposed approach are demonstrated on several numerical examples involving structures and a dynamic multibody system.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330202
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of several open boundary numerical treatments for laminar recirculating flows (1993)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 16 (1993), S. 403-419 
    Details
    ISSN: 0271-2091
    Keywords: Outflow boundary conditions ; Laminar recirculating flows ; Non-staggered grid systems ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Several open boundary conditions (OBCs) are compared and evaluated in the framework of the SIMPLE algorithm using staggered and non-staggered grid systems. The benchmark laminar flow test cases used for the OBC evaluation are Poiseuille-Benard flow in a channel and stratified backward-facing step flow. The investigated OBCs are linear explicit step space extrapolation, Orlanski's monochromatic wave, and pressure extrapolation. Orlanski's and pressure extrapolation open boundary treatment for unsteady and steady flows, respectively, yield little reflection and has proved to be adequate for engineering calculations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650160505
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  • 8
    Electronic Resource
    Electronic Resource
    Neural-network-based approximations for solving partial differential equations (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 195-201 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method, based on neural-network-based functions, for solving partial differential equations is reported in the paper. Using a ‘universal approximator’ based on a neural network and point collocation, the numerical problem of solving the partial differential equation is transformed to an unconstrained minimization problem. The method is extremely easy to implement and is suitable for obtaining an approximate solution in a short period of time. The technique is illustrated with the aid of two numerical examples.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100303
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  • 9
    Electronic Resource
    Electronic Resource
    Multiport approach for the analysis of microwave non-linear networks (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 67-81 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The state and output equations of the overall networks are derived from the state and output equations of individual multiports and knowledge of the interconnections between them. A generalized lumped-distributed L/D multiport is described by its associated state, output and non-linear equations in the time domain. Any network can be considered as composed of a set of multiports and independent sources. These equations have been incorporated into a computer-aided procedure for the analysis of L/D networks. The procedure can be used for the simulation of any non-linear microwave circuit and offers the facility of developing a multiport equivalent circuit for any linear or non-linear device or subcircuit. Several examples are successfully analysed using the developed general program.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060107
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Validation of structural computation codes in elastoviscoplasticity (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 29 (1990), S. 1109-1130 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper discusses various procedures for the implementation of viscoplastic constitutive equations in Finite Element Codes. The set of constitutive equations that has been used is described. Several kinds of implementation, using various numerical techniques, are proposed. Validations of these implementations and comparisons between them are investigated by means of a set of simple but comprehensive examples.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620290514
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