9,156 research outputs found
The Role of Opacities in Stellar Pulsation
We examine the role of opacities in stellar pulsation with reference to
Cepheids and RR Lyraes, and examine the effect of augmented opacities on the
theoretical pulsation light curves in key temperature ranges. The temperature
ranges are provided by recent experimental and theoretical work that have
suggested that the iron opacities have been considerably underestimated. For
Cepheids, we find that the augmented opacities have noticeable effects in
certain period ranges (around ) even though there is a
degeneracy with mixing length. We also find significant effects in theoretical
models of B-star pulsators.Comment: 6 pages, 3 Figures, Proceeding for the "Workshop on Astrophysical
Opacities
Review of \u3ci\u3eSpatial Organization: The Geographer\u27s View of the World\u3c/i\u3e by Ronald Abler, John S. Adams, and Peter Gould
Most introductory textbooks in geography are content-oriented, some pay lip service to basic concepts in geography, and still others are like tombstones conveying concepts and content of a bygone era. Abler, Adams and Gould have presented an introductory text that is rich in concepts, is rooted in contemporary scientific thinking, and conveys a dynamic, futuristic view of geography. The basic thrust in the book is the circularly causal relationships between spatial structure and spatial processes. Geographers with a lands-and-peoples view of geography will be disappointed
A Generalized Statistical Model for THz wireless Channel with Random Atmospheric Absorption
Current statistical channel models for Terahertz (THz) wireless communication
primarily concentrate on the sub-THz band, mostly with - and
Gaussian mixture fading distributions for short-term fading and deterministic
modeling for atmospheric absorption. In this paper, we develop a generalized
statistical model for signal propagation at THz frequencies considering random
path-loss employing Gamma distribution for the molecular absorption
coefficient, short-term fading characterized by the
--- distribution, antenna misalignment errors, and
transceiver hardware impairments. The proposed model can handle various
propagation scenarios, including indoor and outdoor environments,
backhaul/fronthaul situations, and complex urban settings. Using Fox's
H-functions, we present the probability density function (PDF) and cumulative
distribution function (CDF) that capture the combined statistical effects of
channel impairments. We analyze the outage probability of a THz link to
demonstrate the analytical tractability of the proposed generalized model. We
present computer simulations to demonstrate the efficacy of the proposed model
for performance assessment with the statistical effect of atmospheric
absorption.Comment: This work has been submitted to IEEE for possible publcatio
Carrier Transport in Magnesium Diboride: Role of Nano-inclusions
Anisotropic-gap and two-band effects smear out the superconducting transition
(Tc) in literature reported thermal conductivity of MgB2, where large
electronic contributions also suppress anomaly-manifestation in their
negligible phononic-parts. Present thermal transport results on scarcely
explored specimens featuring nano-inclusions exhibit a small but clear
Tc-signature, traced to relatively appreciable phononic conduction, and its
dominant electronic-scattering. The self-formed MgO as extended defects
strongly scatter the charge carriers and minutely the phonons with their
longer-mean-free-path near Tc. Conversely, near room temperature, the
shorter-dominant-wavelength phonon's transport is hugely affected by these
nanoparticles, undergoing ballistic to diffusive crossover and eventually
entering the Ioffe-Regel mobility threshold regime.Comment: 14 pages, 4 figures, 28 reference
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