12,650 research outputs found

    Propfan noise propagation

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    The unconventional supersonic tip speed of advanced propellers has led to uncertainties about Propfan's noise acceptability and compliance with Federal Aviation Noise Regulation (FAR 36). Overhead flight testing of the Propfan with an SR-7L blade during 1989's Propfan Test Assessment (PTA) Program have shown unexpectedly high far-field sound pressure levels. This study here attempts to provide insights into the acoustics of a single-rotating propeller (SRP) with supersonic tip speed. At the same time, the role of the atmosphere in shaping the far-field noise characteristics is investigated

    Postfledging Survival, Movements, and Dispersal of Ring Ouzels (Turdus torquatus)

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    We thank Invercauld Estate for cooperation with access to Glen Clunie. S. Redpath, J. Wilson, and S. Roos provided valuable comments on the manuscript. This study was funded by the Royal Society for the Protection of Birds, Scottish Natural Heritage, and the Cairngorms National Park Authority. J.L.L. was supported by the Natural Environment Research Council.Peer reviewedPublisher PD

    Symmetry breaking and unconventional charge ordering in single crystal Na2.7_{2.7}Ru4_4O9_9

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    The interplay of charge, spin, and lattice degrees of freedom in matter leads to various forms of ordered states through phase transitions. An important subclass of these phenomena of complex materials is charge ordering (CO), mainly driven by mixed-valence states. We discovered by combining the results of electrical resistivity (ρ\rho), specific heat, susceptibility χ\chi (\textit{T}), and single crystal x-ray diffraction (SC-XRD) that Na2.7_{2.7}Ru4_4O9_9 with the monoclinic tunnel type lattice (space group CC2/mm) exhibits an unconventional CO at room temperature while retaining metallicity. The temperature-dependent SC-XRD results show successive phase transitions with super-lattice reflections at \textbf{q}1_1=(0, 12\frac{1}{2}, 0) and \textbf{q}2_2=(0, 13\frac{1}{3}, 13\frac{1}{3}) below TC2T_{\textrm{C2}} (365 K) and only at \textbf{q}1_1=(0, 12\frac{1}{2}, 0) between TC2T_{\textrm{C2}} and TC1T_{\textrm{C1}} (630 K). We interpreted these as an evidence for the formation of an unconventional CO. It reveals a strong first-order phase transition in the electrical resistivity at TC2T_{\textrm{C2}} (cooling) = 345 K and TC2T_{\textrm{C2}} (heating) = 365 K. We argue that the origin of the phase transition is due to the localized 4dd Ru-electrons. The results of our finding reveal an unique example of Ru3+^{3+}/Ru4+^{4+} mixed valance heavy \textit{d}4^4 ions.Comment: 10 pages, 9 figure

    Medium Resolution Near-Infrared Spectra of the Host Galaxies of Nearby Quasars

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    We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844 + 349 (z=0.064), PG 1226 + 023 (z=0.158), and PG 1426+015 (z=0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 um), Si I (1.589 um) and CO (6-3) (1.619 um), and measured the velocity dispersions of PG 0844 + 349 to be 132+/-110 km s-1 and PG 1426 + 015 to be 264+/-215 km s-1. By using an M_BH-sigma relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349, log(M_BH/M_SUN) = 7.7+/-5.5 and PG 1426+015, log(M_BH/M_SUN) = 9.0+/-7.5. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5.Comment: 16 pages, 5 figure
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