6,838 research outputs found

    The dyadic green's function for an infinite moving medium

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    Derivation of dyadic Green function for electromagnetic field in moving medium using Minkowski theory and method of Fourier analysi

    A table of the integrals <for the bessel, hankel, and neumann functions of order zero<

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    Tabulations of Bessel, Hankel, and Neumann functions of order zer

    Subsonic Longitudinal Performance Coefficient Extraction from Shuttle Flight Data: an Accuracy Assessment for Determination of Data Base Updates

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    Longitudinal performance comparisons between flight derived and predicted values are presented for the first five NASA Space Shuttle Columbia flights. Though subsonic comparisons are emphasized, comparisons during the transonic and low supersonic regions of flight are included. Computed air data information based on the remotely sensed atmospheric measurements as well as in situ Orbiter Air Data System (ADS) measurements were incorporated. Each air data source provides for comparisons versus the predicted values from the LaRC data base. Principally, L/D, C sub L, and C sub D, comparisons are presented, though some pitching moment results are included. Similarities in flight conditions and spacecraft configuration during the first five flights are discussed. Contributions from the various elements of the data base are presented and the overall differences observed between the flight and predicted values are discussed in terms of expected variations. A discussion on potential data base updates is presented based on the results from the five flights to date

    An adaptive array for interference rejection

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    Adaptive array based on feedback system for rejection of interfering signal

    Evaluation of the effects of space environment exposure on index of refraction and extinction coefficients of Apollo window materials

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    Temperature and radiation effects on index of refraction and extinction coefficients of Apollo window material

    Ambiguity of gamma-ray tracking of "two-interaction" events

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    Tracking of gamma-ray interactions in germanium detectors can allow reconstruction of the photon paths, and is useful for many applications. Scrutiny of the kinematics and geometry of gamma rays which are Compton scattered only once prior to full absorption reveals that there are cases where even perfect spatial and energy resolution cannot resolve the true interaction sequence and consequently gamma-ray tracks cannot be reconstructed. The photon energy range where this ambiguity exists is from 255 keV to around 700 keV. This is a region of importance for nuclear structure research where two-point interactions are probable.Comment: 8 pages, 2 figure

    Non-radial oscillations in M-giant semi-regular variables: Stellar models and Kepler observations

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    The success of asteroseismology relies heavily on our ability to identify the frequency patterns of stellar oscillation modes. For stars like the Sun this is relatively easy because the mode frequencies follow a regular pattern described by a well-founded asymptotic relation. When a solar like star evolves off the main sequence and onto the red giant branch its structure changes dramatically resulting in changes in the frequency pattern of the modes. We follow the evolution of the adiabatic frequency pattern from the main sequence to near the tip of the red giant branch for a series of models. We find a significant departure from the asymptotic relation for the non-radial modes near the red giant branch tip, resulting in a triplet frequency pattern. To support our investigation we analyze almost four years of Kepler data of the most luminous stars in the field (late K and early M type) and find that their frequency spectra indeed show a triplet pattern dominated by dipole modes even for the most luminous stars in our sample. Our identification explains previous results from ground-based observations reporting fine structure in the Petersen diagram and sub ridges in the period-luminosity diagram. Finally, we find `new ridges' of non-radial modes with frequencies below the fundamental mode in our model calculations, and we speculate they are related to f modes.Comment: 8 page, 5 figures, accepted by ApJL (ApJ, 788, L10
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