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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3011-3015 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple and reproducible process for the open-tube diffusion of zinc from (ZnO)x(SiO2)1−x source films into GaAs, Al0.2Ga0.8As and GaAs0.6P0.4 is reported. (ZnO)x(SiO2)1−x films were deposited onto compound semiconductor substrates by metalorganic chemical vapor deposition. A capping layer of SiO2 was deposited on top of the source films. The diffusions were performed in flowing nitrogen at 650 °C. Diffusion depths from 0.2 μm to several micrometers were readily achieved. The diffusion front in n-type substrates is abrupt and the average hole concentration for diffused layers in GaAs is approximately 8 × 1019/cm3. The dependence of the diffusion depth on the source film composition (x=0.04–x=1.00) is presented. The dependence of the diffusion depth on the source film thickness and the SiO2 cap layer thickness is also reported.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 30 (1996), S. 307-320 
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Computational approaches based on previous nonlinear theoretical findings are developed for a Composite system, the Navier-Stokes system, and the Euler system of equations, in turn, with applications to incompressible boundary-layer transition and dynamic stall. The emphasis is on schemes appropriate for medium-to-large Reynolds numbers, and so as a start the computations are kept to two spatial dimensions. The Composite scheme is developed first, including significant normal-pressure-gradient effects as suggested by the theory. The same scheme is then modified to accommodate, iteratively, the Navier-Stokes form and then the Euler form, for comparison. The agreement between the three sets of results tends to be very close in the parameter ranges studied. The necessary extensions of the work are also discussed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 30 (1996), S. 611-645 
    ISSN: 1573-2703
    Keywords: compressible ; transition ; boundary layers ; interaction ; nonlinear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract An unstable inflection point developing in an oncoming two-dimensional boundary layer can give rise to nonlinear three-dimensional inflectional-wave/vortex interaction as described in recent papers by Hall and Smith [1], Brown et al. [2], and Smith et al. [3]. In the current study on the compressible range the flow is examined theoretically just downstream of the linear neutral position, in order to understand how the interaction may be initiated. The research addresses both moderately and strongly compressible regimes. In the latter regime the vorticity mode, the most dangerous one, is taken as the wave part, causing the hypersonic interaction to become concentrated in a thin temperature-adjustment layer lying at the outer edge of the boundary layer, just below the free stream. In both regimes, the result is a nonlinear integro-differential equation for the wave-pressure which implies four different types of downstream behaviour for the interaction-a far-downstream saturation, a finite-distance singularity, exponentially decaying waves (leaving pure vortex motion) or periodicity. In a principal finding of the study, the coefficients of the equation are worked out explicitly for hypersonic flow, and in particular for the case of unit Prandtl number and a Chapman fluid, where it is shown that for sufficiently high wall temperatures the wave angle of propagation must lie between 45° and 90° relative to the free-stream direction and also no periodic solutions may occur then. The theory applies also to wake flows and others. Connections with experimental findings are noted.
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  • 4
    Publication Date: 1968-07-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 5
    Publication Date: 1969-04-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 6
    Publication Date: 1983-12-15
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 7
    Publication Date: 2012-03-21
    Print ISSN: 1664-3607
    Electronic ISSN: 1664-3615
    Topics: Mathematics
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  • 8
    Publication Date: 1991-03-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 9
    Publication Date: 1994-10-25
    Description: In the fundamental configuration studied here, a steady hypersonic free stream flows over a thin sharp aligned airfoil or flat plate with a leading-edge shock wave, and the flow field in the shock layer (containing a viscous and an inviscid layer) is steady laminar and two-dimensional, for a perfect gas without real and high-temperature gas effects. The viscous and inviscid layers are analysed and computed simultaneously in the region from the leading edge to the trailing edge, including the upstream-influence effect present, to determine the interactive flow throughout the shock layer and the positions of the shock wave and the boundary-layer edge, where matching is required. Further theoretical analysis of the shock layer helps to explain the computational results, including the nonlinear breakdown possible when forward marching against enhanced upstream influence, for example as the wall enthalpy increases towards its insulated value. Then the viscous layer is computed by sweeping methods, for higher values of wall enthalpies, to prevent this nonlinear breakdown for airfoils including the flat plate. Thin airfoils in hypersonic viscous flow are treated, for higher values of the wall enthalpies and with the upstream-influence effect, as are hypersonic inviscid flows, by modifying the computational methods used for the flat plate. Also, the behaviour of the upstream influence for bodies of relatively large thickness, and under wall velocity slip and enthalpy jump for flat plates, is discussed briefly from a theoretical point of view. Subsequent to the present work, computations based on the Navier–Stokes and on the parabolized Navier–Stokes equations have yielded excellent and good agreement respectively with the present predictions for large Mach and Reynolds numbers. © 1994, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 10
    Publication Date: 2007-04-26
    Description: The three-dimensional incompressible turbulent flow through a slender bent pipe of simple cross-section is analysed, the pipe gradually bending the rapid flow through a substantial angle. The ratio of the relative radius of curvature to the magnitude of the turbulent fluctuations is crucial: analysis of the entry region involving exact solutions of the governing equations shows three different downstream developments, depending on the magnitude of that ratio. The main velocity components are found in each case, and one downstream development studied in detail is when turbulence dominates the flow.The main novel points and results are as follows. (i) The present physical situation which arises commonly in industrial settings has been little studied previously by theory or experiments. (ii) The working applies for any two-tier mixing-length model. (iii) As a most surprising feature, the fully developed flow far downstream is not unique, being found to depend instead on the global flow behaviour (thus the centreline velocity is not determined simply by the pressure drop, in contrast to the laminar case). (iv) A quite accurate predictive tool based on approximation is suggested for the downstream flow. (v) Crossflow maxima are found to occur very close to the walls, as observed in experiments. (vi) Other comparisons are made with experimental data and prove generally favourable. The main novel points and results are as follows. (i) The present physical situation which arises commonly in industrial settings has been little studied previously by theory or experiments. (ii) The working applies for any two-tier mixing-length model. (iii) As a most surprising feature, the fully developed flow far downstream is not unique, being found to depend instead on the global flow behaviour (thus the centreline velocity is not determined simply by the pressure drop, in contrast to the laminar case). (iv) A quite accurate predictive tool based on approximation is suggested for the downstream flow. (v) Crossflow maxima are found to occur very close to the walls, as observed in experiments. (vi) Other comparisons are made with experimental data and prove generally favourable. © Cambridge University Press 2007.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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