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  • 1
    Electronic Resource
    Electronic Resource
    Crystalline-to-amorphous transition in chemical vapor deposition of pseudomorphic Si1−x−yGexCy films (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1634-1636 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic SiGeC films have been grown on (100) Si by atmospheric pressure chemical vapor deposition at 600 and 700 °C using SiH2Cl2, GeH4, and C2H4 precursors. Films with C concentrations of up to 2.5 at. % were entirely pseudomorphic and a 120-nm-thick Si66.5Ge31C2.5 film had 90% substitutional carbon. With increasing C incorporation due to increased ethylene flow, a layered structure was formed consisting of an amorphous film overlaying a buried pseudomorphic film. The crystalline-to-amorphous transition was initiated by the accumulation of C on the epitaxial growth surface. This deteriorated surface resulted in the formation of stacking faults along {111} planes and subsequent amorphization. Defect formation and amorphization could be prevented by periodically growing a thin Si epilayer. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120001
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  • 2
    Electronic Resource
    Electronic Resource
    Band gap of Ge rich Si1−x−yGexCy alloys (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2557-2559 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si1−x−yGexCy films ( x≈0.90, y≤0.02) were grown by molecular beam epitaxy on Si substrates. Infrared optical absorption was used to obtain the band gap energy at room temperature. Biaxial strain obtained from x-ray diffraction measurements verified the presence of nearly relaxed films, and the total and substitutional C contents were obtained from channeling C-resonance backscattering spectrometry. We show by direct measurements that interstitial C had a negligible impact on the band gap, but substitutional C was found to increase the band gap with respect to equivalently strained Si1−xGex alloys. While strain decreases the band gap, the effect of substitutional C on the band gap depends on the Si and Ge fractions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117738
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  • 3
    Electronic Resource
    Electronic Resource
    Encapsulation of Ag films on SiO2 by Ti reactions using Ag–Ti alloy/bilayer structures and an NH3 ambient (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3251-3253 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin encapsulated silver films have been prepared on oxidized silicon by nitridation of ∼200-nm-thick Ag–19 at. % Ti alloy films and Ag(120 nm)/Ti(22 nm) at 300–700 °C in an ammonia ambient. The encapsulation process has been studied in detail by Rutherford backscattering, and scanning Auger and secondary-ion-mass spectrometry, which showed that Ti-nitride and Ti-oxide-silicide formation take place at the surface and the Ag–Ti/SiO2 interface, respectively. Four-point-probe analysis of the alloy films suggests that the resistivity is controlled by the residual Ti concentration. Resistivity values of ∼4 μΩ cm were measured in encapsulated Ag alloy films with initial low Ti concentrations. The annealed bilayer structure had minimal Ti accumulations in Ag and the resistivity values were comparable to that of the as-deposited Ag (∼3 μΩ cm). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116564
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of a 2D vortex pair and its 3D breakup: an experimental study (1997)
    Springer
    Experiments in fluids 23 (1997), S. 29-37 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Vortex pairs are studied using a dye tracing visualisation technique and a particle tracking velocimetry system. The vortex pairs are produced by gravity induced inlets of water issued through a uniform gap. The inlet Reynolds number is Re=Ud/ν≈875 in all tests (d being the gap width and U the cross sectional mean velocity), i.e. the flow is in the laminar regime. Initially, the dipolar vortex structure is two-dimensional, but after travelling a distance of a few times its own width, the flow structure becomes unstable, breaks up and changes into a three-dimensional flow structure. The breakup appears to be caused by an axial flow in the core centres of each vortex of the dipolar structure. These axial flows are induced by boundary effects related to the von Karman viscous pump. After the breakup, it is believed that a vortex ring is formed through reconnection of rudiments from the dipolar structure mediated by the wall induced vorticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050083
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  • 5
    Electronic Resource
    Electronic Resource
    DESIGN OF ENERGY CONSERVING ALGORITHMS FOR FRICTIONLESS DYNAMIC CONTACT PROBLEMS (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 863-886 
    Details
    ISSN: 0029-5981
    Keywords: energy conservation ; dynamics ; contact ; finite elements ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper proposes a formulation of dynamic contact problems which enables exact algorithmic conservation of linear momentum, angular momentum, and energy in finite element simulations. It is seen that a Lagrange multiplier enforcement of an appropriate contact rate constraint produces these conservation properties. A related method is presented in which a penalty regularization of the aforementioned rate constraint is utilized. This penalty method sacrifices the energy conservation property, but is dissipative under all conditions of changing contact so that the global algorithm remains stable. Notably, it is also shown that augmented Lagrangian iteration utilizing this penalty kernel reproduces the energy conserving (i.e. Lagrange multiplier) solution to any desired degree of accuracy. The result is a robust, stable method even in the context of large deformations, as is shown by some representative numerical examples. In particular, the ability of the formulation to produce accurate results where more traditional integration schemes fail is emphasized by the numerical simulations. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Energy consistent algorithms for frictional contact problems (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 42 (1998), S. 799-827 
    Details
    ISSN: 0029-5981
    Keywords: contact ; friction ; dynamics ; finite elements ; conservative algorithms ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, the energy and momentum conserving algorithmic paradigm is extended to encompass a phenomenon featuring physical dissipation: dynamic frictional contact. Whereas in other works dealing with conservative systems the chief aim is often the maintenance of numerical stability in the non-linear regime, in this investigation we seek to achieve not only this benefit but also the accurate algorithmic production of physical dissipation associated with frictional processes. The approach here features a product formula algorithm for the evolution of local frictional conditions, with the associated operator split guided by an a priori energy estimate. The resulting algorithm is characterized by exact conservation of energy during stick friction, and positive dissipation consistent with the frictional model used during slip. Effectiveness of the algorithm is demonstrated by a series of finite element simulations involving large deformations and frictional slip, complete with appropriate comparisons to more traditional schemes. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    An augmented Lagrangian quasi-Newton solver for constrained nonlinear finite element applications (1995)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 38 (1995), S. 3571-3590 
    Details
    ISSN: 0029-5981
    Keywords: quasi-Newton solver ; augmented Lagrangians ; nonlinear finite elements ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A solution scheme is presented for constrained non-linear equations of evolution that result, for example, from the finite element discretization of mechanical contact problems. The algorithm discussed utilizes a quasi-Newton non-linear equation solving strategy, with constraints enforced by an augmented Lagrangian iteration procedure. Through presentation of a simple model problem and its generalization, it is shown that the iterations associated with both the quasi-Newton algorithm and the augmentation procedure can be interwoven to produce a highly efficient and robust solution strategy.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620382103
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  • 8
    Electronic Resource
    Electronic Resource
    A finite element formulation of thermomechanical rate-dependent frictional sliding (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 4275-4311 
    Details
    ISSN: 0029-5981
    Keywords: friction ; finite elements ; thermomechanical coupling ; thermal contact ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this work, a combined theoretical and numerical approach is taken to consider the dynamic behaviour and the thermomechanical interactions of systems in which friction has an important role. Emphasis is placed on the proper numerical description of fully coupled thermomechanical response on frictional interfaces. From a theoretical standpoint, the first and second laws of thermodynamics are carefully formulated in the context of large deformations, giving rise to a numerical description of contact interaction that is consistent with these laws. Physical observations encompassed by the proposed interface description include thermal softening of frictional response, rate dependence, pressure dependent heat conduction across the interface, and heat sinks on the interfaces created by trapped wear debris. The finite element implementation of the framework is discussed and demonstrated, with numerical examples successfully describing such phenomena as fading braking torque in automobiles and the observed temperature and friction evolution at the interface between a gun barrel and a projectile passing through it. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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