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  • 1980-1984  (3)
  • 1975-1979  (1)
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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A chalcogenide glass-ceramic (0.3 PbSe-0.7 Ge1.5 As0.5 Se3) which transmits in the infra-red region between 8 and 12 μm was produced from a phase separated parent glass. The glass transition temperature (T g) was increased from 280 to ∼ 340°C by crystallizing the phase with the lowerT g. Further heat-treatment produced a glass-ceramic that was up to 60% crystalline and contained PbSe, PbSe2 and GeSe2 crystals with a gran size of ∼ 0.5 μm. The infra-red transmission of the glass-ceramic decreased with increased crystallinity. The glass-ceramic modulus of rupture (38 MN m−2) was increased to as much as twice that of the glass and the Vickers hardness increased by 30% to ∼ 280 kg mm−2.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-07-13
    Description: An implicit delta form finite-difference algorithm for Euler equations in conservation law form has been used in preliminary calculations of three-dimensional wing-vortex interactions. Both steady and unsteady transonic flow wing-vortex interactions are computed. The computations themselves are meant to guide upcoming wind tunnel experiments of the same flow field. Various modifications to the numerical method that are intended to improve computational efficiency are also described and tested in both two- and three-dimensions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1206 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
    Format: text
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  • 3
    Publication Date: 2019-06-28
    Description: Unsteady interactions of strong concentrated vortices, distributed gusts, and sharp-edged gusts with stationary airfoils were analyzed in two-dimensional transonic flow. A simple and efficient method for introducing such vortical disturbances was implemented in numerical codes that range from inviscid transonic small disturbance to thin-layer Navier Stokes. The numerical results demonstrate the large distortions in the overall flow field and in the surface air loads that are produced by various vortical interactions. The results of the different codes are in excellent qualitative agreement, but, as might expected, the transonic small-disturbance calculations are deficient in the important region near the leading edge.
    Keywords: AERODYNAMICS
    Type: NASA-TM-86658 , REPT-85075 , NAS 1.15:86658 , USAAVSCOM-TM-84-A-10 , AD-A152417
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: A perturbation form of an implicit conservative, noniterative numerical algorithm for the two-dimensional thin layer Navier-Stokes and Euler equations is used to compute the interaction flow-field of a vortex with stationary airfoil. A Lamb-like analytical vortex having a finite core is chosen to interact with a thick (NACA 0012) and a thin (NACA 64A006) airfoil independently in transonic flow. Two different configurations of vortex interaction are studied, viz., (1) when the vortex is fixed at one location in the flowfield, and (2) when the vortex is convecting past the airfoil at freestream velocity. Parallel computations of this interacting flowfield are also done using a version of the Transonic Small Disturbance Code (ATRAN2). A special treatment of the leading edge region for thin airfoils is included in this code. With this, the three methods gave qualitatively similar results for the weaker interactions considered in this study. However, the strongest interactions considered proved to be beyond the capabilities of the small disturbance code. The results also show a far greater influence of the vortex on the airfoil flowfield when the vortex is stationary than when it is convecting with the flow.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-0254
    Format: text
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