74,142 research outputs found
Layered Kondo lattice model for quantum critical beta-YbAlB4
We analyze the magnetic and electronic properties of the quantum critical
heavy fermion superconductor beta-YbAlB4, calculating the Fermi surface and the
angular dependence of the extremal orbits relevant to the de Haas--van Alphen
measurements. Using a combination of the realistic materials modeling and
single-ion crystal field analysis, we are led to propose a layered Kondo
lattice model for this system, in which two dimensional boron layers are Kondo
coupled via interlayer Yb moments in a state. This model fits
the measured single ion magnetic susceptibility and predicts a substantial
change in the electronic anisotropy as the system is pressure-tuned through the
quantum critical point.Comment: Fig.3 and 4 have been updated, typos corrected in v2. Published at
http://link.aps.org/doi/10.1103/PhysRevLett.102.07720
High Spectral Purity, Narrow Linewidth Laser Transmitter for Dial Measurements
A laser transmission with very high degree of spectral purity was described. Amplified Spontaneous Emission (ASE) dependence on the oscillator energy and the detuning away from the gain curve center are demonstrated. The effects of both finite laser linewidth and spectral purity on humidity measurements are experimentally demonstrated
Null Geodesic Expansion in Spherical Gravitational Collapse
We derive an expression for the expansion of outgoing null geodesics in
spherical dust collapse and compute the limiting value of the expansion in the
approach to singularity formation. An analogous expression is derived for the
spherical collapse of a general form of matter. We argue on the basis of these
results that the covered as well as the naked singularity solutions arising in
spherical dust collapse are stable under small changes in the equation of
state.Comment: 10 pages, Latex File, No figure
Identification and analysis of factors affecting thermal shock resistance of ceramic materials in solar receivers
An analysis was conducted of the possible modes of thermal stress failure of brittle ceramics for potential use in point-focussing solar receivers. The pertinent materials properties which control thermal stress resistance were identified for conditions of steady-state and transient heat flow, convective and radiative heat transfer, thermal buckling and thermal fatigue as well as catastrophic crack propagation. Selection rules for materials with optimum thermal stress resistance for a particular thermal environment were identified. Recommendations for materials for particular components were made. The general requirements for a thermal shock testing program quantitatively meaningful for point-focussing solar receivers were outlined. Recommendations for follow-on theoretical analyses were made
Almost unbiased ratio and product-type estimators in systematic sampling
In this paper we have suggested almost unbiased ratio-type and product-type estimators for estimating the population mean Y of the study variate y using information on an auxiliary variate x in systematic sampling. The variance expressions of the suggested estimators have been obtained and compared with usual unbiased estimator y*, Swain's (1964) ratio estimator y*R and Shukla's product estimator y*p. It has been shown that the proposed estimators are more efficient than usual unbiased estimator y*, ratio estimator y*R and product estimator y*p. An empirical study is carried out to demonstrate the superioriy of the constructed estimators over the estimators y*, y*R and y*p
Free-energy functional for freezing transitions: Hard sphere systems freezing into crystalline and amorphous structures
A free-energy functional that contains both the symmetry conserved and
symmetry broken parts of the direct pair correlation function has been used to
investigate the freezing of a system of hard spheres into crystalline and
amorphous structures. The freezing parameters for fluid-crystal transition have
been found to be in very good agreement with the results found from
simulations. We considered amorphous structures found from the molecular
dynamics simulations at packing fractions lower than the glass close
packing fraction and investigated their stability compared to that
of a homogeneous fluid. The existence of free-energy minimum corresponding to a
density distribution of overlapping Gaussians centered around an amorphous
lattice depicts the deeply supercooled state with a heterogeneous density
profile
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