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  • 1
    Electronic Resource
    Electronic Resource
    Two-photon resonant four-wave mixing processes in atomic barium (1980)
    Springer
    Applied physics 23 (1980), S. 333-339 
    Details
    ISSN: 1432-0630
    Keywords: 42.65 ; 32
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of a N2-laser pumped dye-laser (P L ≈20kW, Δv L 〈 10 GHZ) different two-photon resonant four-wave coupling processes in Ba vapour (n Ba≈1016 cm−3) using the Ba states 6s8s 1 S o and 7s5d 1 D 2 were investigated. Coherent line radiation with conversion rates up to 10−3 was generated within the range of λ=190–200 nm by sumfrequency mixingv UV=2v 1+v 2 of 3 laser photons and within the range of λ=250–380 nm by couplingv UV=2v 1±v IR of 2 laser photons with one photonv IR stimulated emitted in laser-induced Ba transitions. For the second coupling type the various nonlinear processes contributing to the formation of the coupling components are discussed. The power of the UV-component as function of inensity and resonance detuning of the laser as well as on the phase-mismatch was calculated on the basis of the small signal theory and compared to the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00914920
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  • 2
    Electronic Resource
    Electronic Resource
    Saturation of resonant frequency conversion processes in cadmium vapour (1984)
    Springer
    Applied physics 33 (1984), S. 225-234 
    Details
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated two-photon resonant up conversion of 375 to 159 nm coherent radiation using the four-frequency process ω159=2ω375+ω1040 in cadmium vapour, where the ir component (1040 nm) is internally generated by the 375 nm pump tuned to the Cd two-photon transition 5s 2 1 S 0→5s6s 1 S 0. Scaling laws and tuning behaviour of both the 159 and 1040 nm output power were measured up to 1×108 W cm−2 pump intensity and 2×1017 cm−3 Cd number density. The results are compared to numerical calculations based on semiclassical theory in a stationary perturbation approximation up to third order. Here, in accordance with experimental results, the ir component was assumed to originate from a superposition of stimulated emission and parametric generation. The observed saturation effects turned out to be mainly due to population changes of the atomic levels involved and are qualitatively reproduced by calculations. Discrepancies with respect to absolute output levels are discussed in terms of the approximations in the theoretical formalism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697332
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  • 3
    Electronic Resource
    Electronic Resource
    On boundary conditions for unbounded flows (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 179-185 
    Details
    ISSN: 1069-8299
    Keywords: finite elements ; fluid flow ; open boundaries ; Sommerfield boundary conditions ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We examine a method to impose boundary conditions on arbitrary boundaries, introduced to make domains of infinite extent finite for the purpose of numerical calculations, when a finite element discretization based on linear, bilinear or trilinear elements is used, in one, two or three dimensions, respectively. In particular, we look at the so-called ‘free’ boundary condition, which consists in retaining the boundary integrals generated by the weighted-residuals formulation along the open boundaries and adding them to the stiffness matrix. We show that this procedure is exactly equivalent to imposing on the boundary nodes a Sommerfeld radiation condition in one dimension, and a slightly modified form of the Sommerfeld boundary condition in two and three dimensions. We also show that the procedure is not applicable to the purely elliptic case.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640110211
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  • 4
    Electronic Resource
    Electronic Resource
    A poisson equation formulation for pressure calculations in penalty finite element models for viscous incompressible flows (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 30 (1990), S. 349-361 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The calculation of pressures when the penalty function approximation is used in finite element solutions of laminar incompressible flows is addressed. A Poisson equation for the pressure is formulated that involves third derivatives of the velocity field. The second derivatives appearing in the weak formulation of the Poisson equation are calculated from the C0 velocity approximation using a least squares method. The present scheme is shown to be efficient, free of spurious oscillations, and accurate. Examples of applications are given and compared with results obtained using mixed formulations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620300209
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  • 5
    Electronic Resource
    Electronic Resource
    Finite element techniques for fluid flow, J. J. Connor and C. A. Brebbia, Newnes-Butterworth, London/Boston, 1976. No. of pages: 310. Price: $10·00 (1977)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 1343-1343 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620110815
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  • 6
    Electronic Resource
    Electronic Resource
    Letters to the editor (1979)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 14 (1979), S. 153-155 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620140113
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  • 7
    Electronic Resource
    Electronic Resource
    An ‘upwind’ finite element scheme for two-dimensional convective transport equation (1977)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 131-143 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620110113
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  • 8
    Electronic Resource
    Electronic Resource
    On quadratic elements in finite element solutions of steady-state convection - diffusion equation (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1041-1052 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150706
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  • 9
    Electronic Resource
    Electronic Resource
    A note on upwinding and anisotropic balancing dissipation in finite element approximations to convective diffusion problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1705-1711 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In one dimension, Petrov - Galerkin nonsymmetric weighting for the convective diffusion equation can be interpreted as an added dissipation. The addition of an appropriate amount of dissipation can therefore give the same oscillation-free solutions as the ‘unwinding’, Petrov - Galerkin, finite element methods. The ‘balancing dissipation’ is optimally chosen so that excessive dissipation does not occur. A scheme is presented for extending this approach to two-dimensional problems, and numerical examples show that the new method can be used with improved computational efficiency.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620151111
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  • 10
    Electronic Resource
    Electronic Resource
    Solution of the Pontriagin-Vitt equation for the moments of time to first passage of the randomly accelerated particle by the finite element method (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1408-1412 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The Pontriagin-Vitt equation governing the mean of the time of first passage of a randomly accelerated particles has been studied extensively by Franklin and Rodemich.1 In their paper is presented the analytic solution for the two-sided barrier problem and solutions by several finite difference procedures.This note demonstrates solution of the problem by a Petrov-Galerkin finite element method using upstream weighting functions,2 shown to give rapidly convergent results. In addition, the equation is generalized to include higher statistical moments, and solutions for the first few ordinary moments are reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150913
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