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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 12 (1977), S. 247-254 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By applying the powerful direct optimization technique of conjugate gradients as adapted for the optimization of an open shell energy functional, a uniformly balanced (15s 10p) Gaussian basis set was obtained for the silicon atom. The quality of this basis set, as defined in terms of “exponent forces” or energy gradient |g|, is compatible with the quality of suitably chosen (10s 5p) carbon and (5s) hydrogen basis sets. Contractions better than double zeta were determined for all three bases of Si, C, and H. Using the primitive and contracted bases, ab initio SCF MO calculations were carried out on molecules of SiH4, CH4, and H2. Some of the computed results obtained for H2C = SiH2 are also included as an illustration for organo-silicon compounds.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 12 (1977), S. 355-368 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The valence tautomers of C2H3N have been examined by non-empirical molecular orbital calculations using two split-valence shell basis sets. All geometries were fully optimized using the 4-31G basis set and these structures were then used in 6-31G basis set calculations. The order of stability of the three possible cyclic isomers is 1-azirine 〉 cyclic carbene 〉 2-azirine. The profiles for conversion of vinylmethylene into cyclopropene, vinylnitrene into 1-arizine, and iminomethylene into 2-azirine have all been shown to have barriers.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2019-06-27
    Beschreibung: A complete theory of aeroacoustics of homentropic fluid media is developed and compared with previous theories. The theory is applied to study the interaction of sound with vortex flows, for the DC-9 in a standard take-off configuration. The maximum engine-wake interference noise is estimated to be 3 or 4 db in the ground plane. It is shown that the noise produced by a corotating vortex pair departs significantly from the compact M scaling law for eddy Mach numbers (M) greater than 0.1. An estimate of jet impingement noise is given that is in qualitative agreement with experimental results. The increased noise results primarily from the nonuniform acceleration of turbulent eddies through the stagnation point flow. It is shown that the corotating vortex pair can be excited or de-excited by an externally applied sound field. The model is used to qualitatively explain experimental results on excited jets.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-CR-2987
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2019-06-27
    Beschreibung: The basic theory of aeroacoustics of homentropic fluid media is applied to the problems of sound scattering, production, and stimulated emission. A general theory of scattering from low speed three-dimensional vortex flows is presented. Specific results are given for the horseshoe vortex and vortex ring. The noise of an elementary corotating vortex pair in various flows is calculated. It is shown that a potential flow and shear flow can substantially increase the basic pair noise. Small reverse shears can annihilate vortex pairs and eliminate the pair noise mechanism. The pair results are used to explain qualitatively the operation of noise suppression devices. The stimulated emission of a single vortex pair and four and six vortex arrays is demonstrated. The results for six vortices illustrate how external pure tones can amplify the broadband noise of a jet in agreement with recent experimental evidence.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-CR-3139 , ARAP-363
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2019-07-13
    Beschreibung: The noise radiated by an elementary corotating vortex pair in a shear flow is calculated. It is shown that a small shear can substantially increase the noise while small reverse shears can annihilate vortex pairs and thus reduce the pair noise mechanism. The resonant excitation of an ensonified vortex pair and the broadband noise amplification of a six vortex cluster is calculated. The results are in qualitative agreement with recent experimental findings on jet broadband noise amplification.
    Schlagwort(e): ACOUSTICS
    Materialart: Mechanics of sound generation in flows; Aug 28, 1979 - Aug 31, 1979; Goettingen
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2019-07-13
    Beschreibung: A description is presented of an improved version of a comprehensive theory of aeroacoustics which, in its original form, had first been reported by Yates and Sandri (1976). The new theory departs in several basic aspects from the concepts provided by Lighthill (1952), Ribner (1964), and Lilley et al. (1974). A detailed derivation of the theory is given for the case of constant entropy flows, taking into account the production of sound by a 'primary' fluid flow, the processing of sound by a flow, and the effects of sound on a primary flow. An investigation is conducted regarding the processing and the production of sound by vortex flow. Questions related to the excitation of a fluid flow by sound are also considered.
    Schlagwort(e): ACOUSTICS
    Materialart: AIAA PAPER 77-1352 , Aeroacoustics Conference; Oct 03, 1977 - Oct 05, 1977; Atlanta, GA
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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