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  • 2000-2004  (44)
  • 1975-1979  (2)
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  • 1
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wird ein halbanalytisches Berechnungsverfahren zur Bestimmung der instationären Temperaturen von Haut-Steg-Verbindungen vorgestellt, das den Einfluß einer Fügung zwischen Haut (Flansch eines Winkels) und Steg numerisch berücksichtigt. Ausgehend von den Temperaturfunktionen, die sich unabhängig voneinander für die beiden Strukturelemente bei gegebenen Randbedingungen und konstanter Randtemperatur an der Verbindungsstelle ergeben, kann der thermische Übergangswiderstand der Fügung (z.B. einer Nietverbindung) durch Formulierung einer Wärmebilanz sowohl oberhalb als auch unterhalb der Fügung auf einfache Art in die Berechnung einbezogen werden. Das Verfahren, das am Beispiel von Flugzeugstrukturen (versteifte Tragflügelgurtplatte, Tragflügelkasten) für den Sprung der Fluidtemperatur und des Wärmeübergangskoeffizienten untersucht wird, läßt sich auch auf ähnliche Probleme in anderen Ingenieursdisziplinen übertragen.
    Notes: Abstract A semi-analytical method is presented for calculating temperature transients in skin-web-configurations including the effect of a thermal joint resistance at the web-skin (flange) junction. Based on the temperature functions independently developed for both elements at given boundary conditions and constant junction temperature the joint resistance can be taken into account easily by formulation of a heat balance above and below the joint. The method, here applied to aircraft structures (stiffened panel, wing box) for the step functions of fluid temperature and heat transfer coefficient can also be extended to similar problems in other engineering fields of application.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wird ein einfaches Berechnungsverfahren vorgestellt, das eine Bestimmung des turbulenten Wärmeübergangs hinter einem hydrodynamischen Vorlauf gestattet. Durch eine Anpassung der Randbedingungen in der Reynoldsnalogie an die Strömungsverhältnisse bei unterschiedlichem Beginn von Temperatur- und Geschwindigkeitsgrenzschicht wird das Verhältnis der Nusseltzahlen einer Strömung mit Vorlauf zu der ohne Vorlauf formuliert. Dieses Nusseltzahlverhältnis stellt eine Korrekturfunktion für den Einfluß unbeheizter Anlaufstrecken dar und gestattet die Wärmeübergangsberechnung hinter hydrodynamischen Vorläufen aus den bekannten Gleichungen für den gleichzeitigen Beginn von Temperatur- und Strömungsgrenzschicht. Das Verfahren ist für Rohr-und Plattenströmungen anwendbar; die Korrekturfunktion ist in beiden Fällen eine Funktion der Vorlauflänge und der thermischen Lauflänge, für die Rohrströmung zusätzlich noch Funktion der Reynoldszahl.
    Notes: Abstract An analytical method is presented to calculate the turbulent heat transfer behind an hydrodynamic starting length. By modification of the boundary conditions in the Reynolds analogie with respect to the flow conditions for different running lengths of the boundary layer of temperatur and velocity the heat transfer ratio of a flow with to a flow without hydrodynamic starting length can be formulated. This heat transfer ratio is a correction function to describe the influence of an unheated starting length and allows the heat transfer calculation by using the well known heat transfer formulas for the simultaneous hydrodynamic and thermal start. The method can be applied as well to the flat plate flow as to the pipe flow. In both cases the correction function depends on the unheated starting length and the thermal running length, for the pipe flow additionaly on the Reynolds number.
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  • 3
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    In:  EOS, Transactions, American Geophysical Union, Suppl. ; 84, 46
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 4
    Publication Date: 2020-02-12
    Description: Two seismic wave attenuation factors, scattering attenuation Qs-1 and intrinsic absorption Qi-1 are measured using the Multiple Lapse Time Window (MLTW) analysis method for three different frequency bands, 1-2, 2-4, and 4-8 Hz. Data from 54 temporally deployed seismic stations located in northern Chile are used. This method compares time integrated seismic wave energies with synthetic coda wave envelopes for a multiple isotropic scattering model. In the present analysis, the wave energy is assumed to decay with distance in proportion to1/GSF,exo(-(Qs-1+Qi-1).w r/v), where r, w and v are the propagation distance, angular frequency and S wave velocity, respectively, and GSF is the geometrical spreading factor. When spatial uniformity of Qs-1, Qi-1 and v is assumed, i.e. GSF = 4pr2, the estimates of the reciprocal of the extinction length, Le-1 (=(Qs-1+Qi-1).w/v), are 0.017,0.012 and 0.010 km-1, and those of the seismic albedo, B0(=Qs-1/(Qi-1+Qi-1)), are 0.48, 0.40 and 0.34 for 1-2, 2-4 and 4-8 Hz, respectively, which indicates that scattering attenuation is comparable to or smaller than intrinsic absorption. When we assume a depth dependent velocity structure, we also find that scattering attenuation is comparable to or smaller than intrinsic absorption. However, since the quantitative estimates of scattering attenuation depend on the assumed velocity structure (strength of velocity discontinuity and/or Moho depth), it is important to consider differences in velocity structure models when comparing attenuation estimates.
    Keywords: 550 - Earth sciences
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  • 5
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 6
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 7
    Publication Date: 2020-02-12
    Description: We present a high resolution 3-D model of P-wave attenuation for the central Andean subduction zone. Data from 1500, mostly intermediate depth (60 - 250 km) earthquakes recorded at three temporary seismic networks covering the forearc, arc, and backarc around 23° S were used for tomographic inversion. The forearc is characterised by uniformly high Qp values, indicating low temperature rocks, in accordance with low surface heat flow values. Continuous regions of low Qp connect earthquake clusters at 100 km and 200 km depth with zones of active wedge, where they induce melting, explain our observations. We propose that low Qp regions indicate source and vertical, as is often implicitely assumed. Instead, sources of fluids are located at different depth levels, and ascent Cerro Tuzgle id fed by mantel melts which are imaged as a plume of low Qp material that reaches to the strong earthquake cluster at 200 km depth.
    Keywords: 550 - Earth sciences
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  • 8
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 9
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    In:  64. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (Berlin 2004)
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
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  • 10
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    In:  EOS, Transactions, American Geophysical Union, Suppl. ; 83, 47
    Publication Date: 2020-02-12
    Description: Conventionally, $SKS$ splitting observations are analyzed individually for each seismic station. However, waveforms from high-density two- and three-dimensional seismic arrays facilitate the application of new data processing and inversion techniques, which exploit the coherent nature of the recordings. In this approach, measured splitting parameters, which are obtained under the assumption of a single homogeneous anisotropic layer beneath a station, are not directly interpreted. Instead, the splitting parameters are used as a parameterization of the observed waveforms which allows for an efficient (automated) comparison with results from forward modeling. The formal inversion of the measured splitting parameters employs an iterative approach using ({it i}) a local optimization technique i.e. the downhill Simplex method and ({it ii}) a (global) genetic-algorithm search. The forward-modeling part involves the calculation of $SKS$ waveforms by a complete finite-difference method to solve the anisotropic wave equation. The misfit function is calculated from a comparison of frequency-dependent splitting parameters obtained from the observed and synthetic waveforms. We apply these techniques to the analysis of $SKS$ phases recorded along a 100-km profile with an average station spacing of 1.2 km. The measured splitting parameters show gradual short-scale variations along the profile. The model used in the inversion consists of an anisotropic crust and a 100-km thick anisotropic mantle layer. Variations in anisotropy are accounted for by 2-dimensional block structures. We show the convergence of the two inversion methods by gradually increasing the complexity of the model (as defined by the number of anisotropic blocks). Additional tests based on synthetic models demonstrate the potential and resolution of the inversion approaches.
    Keywords: 550 - Earth sciences
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