134,243 research outputs found

    A high-Q^2 measurement of the photon structure function F_2^gamma at LEP2

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    The photon structure function F_2^gamma has been measured at of 706 GeV^2, using a sample of two-photon events with a scattered electron observed in the OPAL electromagnetic endcap calorimeter. The data were taken during the years 1997-1999, when LEP operated at e+e- centre-of-mass energies ranging from 183 to 202 GeV, and correspond to an integrated luminosity of 424 pb^-1. This analysis represents the highest measurement of F_2^gamma made to date.Comment: 6 pages, 3 figures, To appear in the proceedings of Photon 2000, Ambleside, Englan

    Measurements of hadronic structure functions of the photon at LEP

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    The present status of the measurements of hadronic structure functions of the photon, investigated in deep inelastic electron-photon scattering at LEP, is presented. This article covers the hadronic structure function F_2^gamma of quasi-real photons as well as the structure function of virtual photons. Special emphasis is given to new developments in the analysis and to the most recent measurements.Comment: 6 pages, 4 figures, To appear in the proceedings of DIS 2001, Bologna, Ital

    Turbulence measurements in the compressor exit flow of a General Electric CF6-50 engine

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    Ruggedized cooled film probes were used to measure CF6-50 compressor exit turbulence properties at three different engine idle condition test points. The turbulence probe was coupled to a constant temperature anemometer and signal conditioning system. An on-line readout system connected to the anemometer was used to check the data as it was acquired. At engine idle conditions, the turbulence intensity ranged from 4.8 percent to 5.6 percent and the length scale ranged from 5.64 cm to 6.95 cm. The length scale values are somewhat larger than the passage height at the measurement plane (5.54 cm), which indicates that the shape of the turbulent eddies are elongated in the axial direction. The microscale values range from about 0.73 cm to about 0.98 cm. Power spectral density distributions show that a large proportion of the turbulent energy at the measurement plane is concentrated at frequencies below one kilohertz

    Mixed partial-wave scattering with spin-orbit coupling and validity of pseudo-potentials

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    We present exact solutions of two-body problem for spin-1/2 fermions with isotropic spin-orbit(SO) coupling and interacting with an arbitrary short-range potential. We find that in each partial-wave scattering channel, the parametrization of two-body wavefunction at short inter-particle distance depends on the scattering amplitudes of all channels. This reveals the mixed partial-wave scattering induced by SO couplings. By comparing with results from a square-well potential, we investigate the validity of original pseudo-potential models in the presence of SO coupling. We find the s-wave pseudo-potential provides a good approximation for low-energy solutions near s-wave resonances, given the length scale of SO coupling much longer than the potential range. However, near p-wave resonance the p-wave pseudo-potential gives low-energy solutions that are qualitatively different from exact ones, based on which we conclude that the p-wave model can not be applied to the fermion system if the SO coupling strength is larger or comparable to the Fermi momentum.Comment: 10 pages, 8 figures. Published version with figures improve

    L-band, 1.2 m parabolic antenna-noise temperature measurement

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    Extensive antenna-noise temperature measurements at 1.6 GHz (L-band) were made using a 1.2 m (4 ft. diameter) parabolic dish antenna mounted on the flying bridge of a modern 15,690-ton, commercial-container ship. Both in-harbor and at-sea radiometer measurements were made that indicated a steady background, antenna-noise temperature value slightly less than 70 degrees Kelvin (K) at elevation angles of 5 percent, and greater, at 1.6 GHz. A comparison of theoretical and measured values indicate excellent agreement within about 5K for at-sea data. These measurements are helpful to RF equipment designers of maritime, L-band shipboard terminals for operation with the two, geostationary, maritime satellites, Marisat-A and -B

    Navigation system and method

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    In a global positioning system (GPS), such as the NAVSTAR/GPS system, wherein the position coordinates of user terminals are obtained by processing multiple signals transmitted by a constellation of orbiting satellites, an acquisition-aiding signal generated by an earth-based control station is relayed to user terminals via a geostationary satellite to simplify user equipment. The aiding signal is FSK modulated on a reference channel slightly offset from the standard GPS channel. The aiding signal identifies satellites in view having best geometry and includes Doppler prediction data as well as GPS satellite coordinates and identification data associated with user terminals within an area being served by the control station and relay satellite. The aiding signal significantly reduces user equipment by simplifying spread spectrum signal demodulation and reducing data processing functions previously carried out at the user terminals
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