78,236 research outputs found
Phonon-phason coupling in icosahedral quasicrystals
From relaxation simulations of decoration-based quasicrystal structure models
using microscopically based interatomic pair potentials, we have calculated the
(usually neglected) phonon-phason coupling constant. Its sign is opposite for
the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its
magnitude relative to the phonon and phason elastic constants is of order 1/10,
suggesting its effects are small but detectable. We also give a criterion for
when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included
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Assessing the effects of technological progress on energy efficiency in the construction industry: A case of China
Energy-saving technologies in buildings have received great attention from energy efficiency researchers in the construction sector. Traditional research tends to focus on the energy used during building operation and in construction materials production, but it usually neglects the energy consumed in the building construction process. Very few studies have explored the impacts of technological progress on energy efficiency in the construction industry. This paper presents a model of the building construction process based on Cobb-Douglas production function. The model estimates the effects of technological progress on energy efficiency with the objective to examine the role that technological progress plays in energy savings in China's construction industry. The modeling results indicated that technological progress improved energy efficiency by an average of 7.1% per year from 1997 to 2014. Furthermore, three main technological progress factors (the efficiency of machinery and equipment, the proportion change of the energy structure, and research and development investment) were selected to analyze their effects on energy efficiency improvement. These positive effects were verified, and results show the effects of first two factors are significant. Finally, recommendations for promoting energy efficiency in the construction industry are proposed
Numerical simulations of negative-index refraction in wedge-shaped metamaterials
A wedge-shaped structure made of split-ring resonators (SRR) and wires is
numerically simulated to evaluate its refraction behavior. Four frequency
bands, namely, the stop band, left-handed band, ultralow-index band, and
positive-index band, are distinguished according to the refracted field
distributions. Negative phase velocity inside the wedge is demonstrated in the
left-handed band and the Snell's law is conformed in terms of its refraction
behaviors in different frequency bands. Our results confirmed that negative
index of refraction indeed exists in such a composite metamaterial and also
provided a convincing support to the results of previous Snell's law
experiments.Comment: 18 pages, 6 figure
Spin Susceptibility of a 2D Electron System in GaAs towards the Weak Interaction Region
We determine the spin susceptibility in the weak interaction regime of
a tunable, high quality, two-dimensional electron system in a GaAs/AlGaAs
heterostructure. The band structure effects, modifying mass and g-factor, are
carefully taken into accounts since they become appreciable for the large
electron densities of the weak interaction regime. When properly normalized,
decreases monotonically from 3 to 1.1 with increasing density over our
experimental range from 0.1 to . In the high density
limit, tends correctly towards and compare well with recent
theory.Comment: Submitted to Physical Review
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