10,484 research outputs found
Comparison between measured turbine stage performance and the predicted performance using quasi-3D flow and boundary layer analyses
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
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
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
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
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
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
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 , , the charm quark mass, heavy-light and heavy-strange
bag parameters and the ratio .Comment: 8 pagers, 4 figures, conference proceedings for Lattice2017 submitted
to EPJ Web of Conference
The Fall of the Quasar Population
We derive quantitative predictions of the optical and X-ray luminosity
functions (LF) for QSs in the redshift range . Based on BH paradigm, we
investigate how the accretion is controlled by the surrounding structures, as
these grow hierarchically. We argue that for efficient black hole
fueling is triggered by the encounters of a gas-rich host with its companions
in a group. The dispersion of the dynamical parameters in the encounters
produces a double power-law LF. Strong luminosity evolution (LE) is produced as
these encounters deplete the gas supply in the host; an additional, milder
density evolution obtains since the interactions become progressively rarer as
the groups grow richer but less dense. From the agreement with the optical and
the X-ray data, we conclude that the evolution of the bright quasars is
articulated in two ways. Earlier than the gas-rich protogalaxies grow by
merging, which also induces parallel growth of central holes accreting at
Eddington rates. In the later era of group assemblage the host encounters with
companions drive onto already existing holes further but meager accretion;
these consume the gas in the hosts, and cause supply-limited emissions which
are intermittent, go progressively sub-Eddington and peter out. Then other
fueling processes come to the foreground; we discuss the faint emissions,
especially noticeable in X-rays, which are expected when hosts in the field
cannibalize satellite galaxies with their meager gas contents.Comment: 12 pages Latex + 3 EPS figures, ApJ in press, we have corrected the
previous printing problems with the style \ca
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