205,707 research outputs found
Crystal growth and in-plane optical properties of TlBaCaCuO (n=1,2,3) superconductors
Single crystals of thallium-based cuprates with the general formula
TlBaCaCuO(n=1,2,3) have been grown by the flux
method. The superconducting transition temperatures determined by the ac
magnetic susceptibility are 92 K, 109 K, and 119 K for n=1,2,3 respectively.
X-ray diffraction measurements and EDX compositional analysis were described.
We measured in-plane optical reflectance from room temperature down to 10 K,
placing emphasis on Tl-2223. The reflectance roughly has a linear-frequency
dependence above superconducting transition temperature, but displays a
pronounced knee structure together with a dip-like feature at higher frequency
below T. Correspondingly, the ratio of the reflectances below and above
T displays a maximum and a minimum near those feature frequencies. In
particular, those features in Tl2223 appear at higher energy scale than Tl2212,
and Tl2201. The optical data are analyzed in terms of spectral function. We
discussed the physical consequences of the data in terms of both clean and
dirty limit.Comment: 8 pages, 13 figures, to be published in Phys. Rev.
Neutrino Mass from Triplet and Doublet Scalars at the TeV Scale
If the minimal standard model of particle interactions is extended to include
a scalar triplet with lepton number and a scalar doublet with ,
neutrino masses eV is possible,
where GeV is the electroweak symmetry breaking scale,
TeV is the typical mass of the new scalars, and GeV is a soft
lepton-number-violating parameter.Comment: 6 pages, no figur
Shifting with
Precision measurements at the resonance agree well with the standard
model. However, there is still a hint of a discrepancy, not so much in by
itself (which has received a great deal of attention in the past several years)
but in the forward-backward asymmetry together with . The two
are of course correlated. We explore the possibilty that these and other
effects are due to the mixing of and with one or more heavy quarks.Comment: 11 pages, 1 Figure, LaTex fil
Canceling Quadratic Divergences in a Class of Two-Higgs-Doublet Models
The Newton-Wu conditions for the cancellation of quadratic divergences in a
class of two-Higgs-doublet models are analyzed as to how they may be satisfied
with a typical extension of the Standard Model of particle interactions.Comment: 5 pages, no figur
Quantization of static space-times
A 4-dimensional Lorentzian static space-time is equivalent to 3-dimensional
Euclidean gravity coupled to a massless Klein-field. By canonically quantizing
the coupling model in the framework of loop quantum gravity, we obtain a
quantum theory which actually describes quantized static space-times. The
Kinematical Hilbert space is the product of the Hilbert space of gravity with
that of imaginary scalar fields. It turns out that the Hamiltonian constraint
of the 2+1 model corresponds to a densely defined operator in the underlying
Hilbert space, and hence it is finite without renormalization. As a new point
of view, this quantized model might shed some light on a few physical problems
concerning quantum gravity.Comment: 14 pages, made a few modifications, added Journal-re
Numerical framework for transcritical real-fluid reacting flow simulations using the flamelet progress variable approach
An extension to the classical FPV model is developed for transcritical
real-fluid combustion simulations in the context of finite volume, fully
compressible, explicit solvers. A double-flux model is developed for
transcritical flows to eliminate the spurious pressure oscillations. A hybrid
scheme with entropy-stable flux correction is formulated to robustly represent
large density ratios. The thermodynamics for ideal-gas values is modeled by a
linearized specific heat ratio model. Parameters needed for the cubic EoS are
pre-tabulated for the evaluation of departure functions and a quadratic
expression is used to recover the attraction parameter. The novelty of the
proposed approach lies in the ability to account for pressure and temperature
variations from the baseline table. Cryogenic LOX/GH2 mixing and reacting cases
are performed to demonstrate the capability of the proposed approach in
multidimensional simulations. The proposed combustion model and numerical
schemes are directly applicable for LES simulations of real applications under
transcritical conditions.Comment: 55th AIAA Aerospace Sciences Meeting, Dallas, T
An integrated wind risk warning model for urban rail transport in Shanghai, China
The integrated wind risk warning model for rail transport presented has four elements:
Background wind data, a wind field model, a vulnerability model, and a risk model. Background
wind data uses observations in this study. Using the wind field model with effective surface
roughness lengths, the background wind data are interpolated to a 30-m resolution grid. In the
vulnerability model, the aerodynamic characteristics of railway vehicles are analyzed with CFD
(Computational Fluid Dynamics) modelling. In the risk model, the maximum value of three
aerodynamic forces is used as the criteria to evaluate rail safety and to quantify the risk level under
extremely windy weather. The full model is tested for the Shanghai Metro Line 16 using wind
conditions during Typhoon Chan-hom. The proposed approach enables quick quantification of real-
time safety risk levels during typhoon landfall, providing sophisticated warning information for
rail vehicle operation safety
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