10,596 research outputs found

    Comparison between measured turbine stage performance and the predicted performance using quasi-3D flow and boundary layer analyses

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    A method for calculating turbine stage performance is described. The usefulness of the method is demonstrated by comparing measured and predicted efficiencies for nine different stages. Comparisons are made over a range of turbine pressure ratios and rotor speeds. A quasi-3D flow analysis is used to account for complex passage geometries. Boundary layer analyses are done to account for losses due to friction. Empirical loss models are used to account for incidence, secondary flow, disc windage, and clearance losses

    Semi-leptonic decays heavy-light to heavy light

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    We present results for the QCD matrix elements involved in semi-leptonic decays of B-mesons into pseudo scalar heavy light states. The application of NRQCD heavy quarks allows for quark masses around the physical b-quark. We investigate the dependence of the form factors on the external momenta and looked at the mass dependence at zero recoil. For the first time, results for radially excited decay products are presented.Comment: 3 pages LaTeX, 5 figures, Talk given at LATTICE99(Heavy Quarks), June 29th to July 3rd, 1999, Pisa, Ital

    The unquenched Upsilon spectrum

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    We describe the bottomonium spectrum obtained on the UKQCD dynamical ensembles and its comparison to quenched results. We include a determination of alpha_s and m_b from the dynmaical results.Comment: Lattice 2000 (Heavy Quark Physics

    2dF QSO Redshift Survey

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    With approximately 6000 QSO redshifts,the 2dF QSO redshift survey is already the biggest complete QSO survey. The aim for the survey is to have 25000 QSO redshifts, providing an order of magnitude increase in QSO clustering statistics. We first describe the observational parameters of the 2dF QSO survey. We then describe several highlights of the survey so far, including new estimates of the QSO luminosity function and its evolution. We also review the current status of QSO clustering analyses from the 2dF data. Finally, we discuss how the complete QSO survey will be able to constrain the value of Omega_o by measuring the evolution of QSO clustering, place limits on the cosmological constant via a direct geometrical test and determine the form of the fluctuation power-spectrum out to the approximately 1000 Mpc scales only previously probed by COBE.Comment: 6 pages; to be published in Clustering at High Redshift, Marseille, June 1999, eds. A. Mazure, O. LeFevre, V. Lebru

    The 2dF QSO Redshift Survey

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    We present preliminary results from the 2-degree Field (2dF) QSO Redshift Survey currently under way at the Anglo-Australian Telescope. This survey aims to determine the redshifts of >25000 QSOs over a redshift range of 0.3<z<3.0 with the primary goal of investigating large-scale structure in the Universe to high redshift and at very large scales (~1000h-1Mpc). We describe the photometric procedure used to select QSO candidates for spectroscopic observation. We then describe results from our first 2dF observations, which have so far measured the redshifts for over 1000 QSOs. We already find a significant detection of clustering and have also found one close pair of QSOs (separation 17'') which are gravitational lens candidates. To keep up to date with the current progress of the survey see: http://msowww.anu.edu.au/~rsmith/QSO_Survey/qso_surv.htmlComment: 5 pages Latex including 6 figures, To appear in the proceedings of "Evolution of Large Scale Structure: From Recombination to Garching", held August 199

    QSO clustering and the AAT 2dF redshift survey

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    We review previous results on the clustering and environments of QSOs. We show that the correlation length for QSOs derived from existing surveys is r~5/h Mpc, similar to the observed correlation length for field galaxies at the present epoch. The galaxy environment for z<1 radio-quiet QSOs is also consistent with field galaxies. The evolution of the QSO correlation length with redshift is currently uncertain, largely due to the small numbers of QSOs (~2000) in surveys suitable for clustering analysis. We report on intial progress with the AAT 2dF QSO redshift survey, which, once completed will comprise almost 30000 QSOs. With over 1000 QSOs already observed, it is already the largest single homogeneous QSO survey. We discuss prospects for deriving limits on cosmological parameters from this survey, and on the evolution of large-scale structure in the Universe.Comment: Invited talk at RS meeting on 'Large Scale Structure in the Universe' held at the Royal Society on 25-26 March 1998 14 pages, 11 figre

    Heavy Domain Wall Fermions: The RBC and UKQCD charm physics program

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    We review the domain wall charm physics program of the RBC and UKQCD collaborations based on simulations including ensembles with physical pion mass. We summarise our current set-up and present a status update on the decay constants fDf_D, fDsf_{D_s}, the charm quark mass, heavy-light and heavy-strange bag parameters and the ratio Îľ\xi.Comment: 8 pagers, 4 figures, conference proceedings for Lattice2017 submitted to EPJ Web of Conference

    The 2dF QSO Redshift Survey - 10K@2K!

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    With ~10000 QSO redshifts, the 2dF QSO Redshift Survey (2QZ) is already the biggest individual QSO survey. The aim for the survey is to have ~25000 QSO redshifts, providing an order of magnitude increase in QSO clustering statistics. We first describe the observational parameters of the 2dF QSO survey. We then describe several highlights of the survey so far; we present new estimates of the QSO luminosity function and the QSO correlation function. We also present the first estimate of the QSO power spectrum from the 2QZ catalogue, probing the form of the fluctuation power-spectrum out to the \~1000h-1Mpc scales only previously probed by COBE. We find a power spectrum which is steeper than the prediction of standard CDM and more consistent with the prediction of Lambda-CDM. The best-fit value for the power spectrum shape parameter for a range of cosmologies is Gamma=0.1+-0.1. Finally, we discuss how the complete QSO survey will be able to constrain the value of Omega_Lambda by combining results from the evolution of QSO clustering and from a geometric test of clustering isotropy.Comment: 11 pages, 6 figures, latex, eso and springer sty files included. To appear in the proceedings of the MPA/ESO/MPA conference "Mining the Sky", Garching, July 31 - August 4 2000, eds. A.J. Banday et a
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