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Air-Coupled Surface Wave Transmission Measurement Across A Partially Closed Surface-Breaking Crack In Concrete
Previous researchers have demonstrated that the transmission of surface waves is effective to estimate the depth of a surface-breaking crack in solids. However, most of the results were obtained using a well-defined crack (or notch) in laboratory. In fact, there is a critical gap to apply the theory to surface-breaking cracks in concrete structures subjected to external loadings where the cracks are generally ill-defined, and partially closed. In this study, the authors investigated transmission coefficients of surface waves across a partially closed surface-breaking crack in concrete subjected to monotonically increasing compressive loadings. First, a concrete beam (0.5 X 0.154 X 2.1 m(3)) having two surface-breaking cracks with various crack widths was prepared in laboratory. Second, transmission coefficients of impact-induced surface waves were measured across a surface-breaking crack in the concrete beam with increasing compressive loadings from 0 to 140kN (10% of the ultimate compressive strength of the concrete beam). External post-tensioning was used to apply the compression. For comparison purpose, sensitivity of surface wave velocity to compressive loading was also investigated. As a result, observations in this study reveal that transmission coefficient is a more sensitive acoustic parameter than phase velocity to evaluate a surface-breaking cracking in concrete subjected to compressive loadings.Civil, Architectural, and Environmental Engineerin
Nematicity as a route to a magnetic field-induced spin density wave order; application to the high temperature cuprates
The electronic nematic order characterized by broken rotational symmetry has
been suggested to play an important role in the phase diagram of the high
temperature cuprates. We study the interplay between the electronic nematic
order and a spin density wave order in the presence of a magnetic field. We
show that a cooperation of the nematicity and the magnetic field induces a
finite coupling between the spin density wave and spin-triplet staggered flux
orders. As a consequence of such a coupling, the magnon gap decreases as the
magnetic field increases, and it eventually condenses beyond a critical
magnetic field leading to a field-induced spin density wave order. Both
commensurate and incommensurate orders are studied, and the experimental
implications of our findings are discussed.Comment: 5 pages, 3 figure
Signatures of Electronic Nematic Phase at Isotropic-Nematic Phase Transition
The electronic nematic phase occurs when the point-group symmetry of the
lattice structure is broken, due to electron-electron interactions. We study a
model for the nematic phase on a square lattice with emphasis on the phase
transition between isotropic and nematic phases within mean field theory. We
find the transition to be first order, with dramatic changes in the Fermi
surface topology accompanying the transition. Furthermore, we study the
conductivity tensor and Hall constant as probes of the nematic phase and its
transition. The relevance of our findings to Hall resistivity experiments in
the high- cuprates is discussed.Comment: 5 pages, 3 figure
Subwavelength localization and toroidal dipole moment of spoof surface plasmon polaritons
We experimentally and theoretically demonstrate subwavelength scale localization of spoof surface plasmon polaritons at a point defect in a two-dimensional groove metal array. An analytical expression for dispersion relation of spoof surface plasmon polaritons substantiates the existence of a band gap where a defect mode can be introduced. A waveguide coupling method allows us to excite localized spoof surface plasmon polariton modes and measure their resonance frequencies. Numerical calculations confirm that localized modes can have a very small modal volume and a high Q factor both of which are essential in enhancing light-matter interactions. Interestingly, we find that the localized spoof surface plasmon polariton has a significant toroidal dipole moment, which is responsible for the high Q factor, as well as an electric quadrupole moment. In addition, the dispersion properties of spoof surface plasmon polaritons are analyzed using a modal expansion method and numerical calculations
Collective modes and sound propagation in a p-wave superconductor: SrRuO
There are five distinct collective modes in the recently discovered p-wave
superconductor SrRuO; phase and amplitude modes of the order parameter,
clapping mode (real and imaginary), and spin wave. The first two modes also
exist in the ordinary s-wave superconductors, while the clapping mode with the
energy is unique to SrRuO and couples to the sound
wave. Here we report a theoretical study of the sound propagation in a two
dimensional p-wave superconductor. We identified the clapping mode and study
its effects on the longitudinal and transverse sound velocities in the
superconducting state. In contrast to the case of He, there is no resonance
absorption associated with the collective mode, since in metals , where is the Fermi velocity, {\bf q} is the wave
vector, and is the frequency of the sound wave. However, the velocity
change in the collisionless limit gets modified by the contribution from the
coupling to the clapping mode. We compute this contribution and comment on the
visibility of the effect. In the diffusive limit, the contribution from the
collective mode turns out to be negligible. The behaviors of the sound velocity
change and the attenuation coefficient near in the diffusive limit are
calculated and compared with the existing experimental data wherever it is
possible. We also present the results for the attenuation coefficients in both
of the collisionless and diffusive limits at finite temperatures.Comment: RevTex, 12 pages, 2 figures, Replaced by the published versio
Interplay between Fermi surface topology and ordering in URuSi revealed through abrupt Hall coefficient changes in strong magnetic fields
Temperature- and field-dependent measurements of the Hall effect of pure and
4 % Rh-doped URuSi reveal low density (0.03 hole/U) high mobility
carriers to be unique to the `hidden order' phase and consistent with an
itinerant density-wave order parameter. The Fermi surface undergoes a series of
abrupt changes as the magnetic field is increased. When combined with existing
de Haas-van Alphen data, the Hall data expose a strong interplay between the
stability of the `hidden order,' the degree of polarization of the Fermi liquid
and the Fermi surface topology.Comment: 4 pages, 4 figures, Accepted to Phys. Rev. Let
Performance Evaluation of Finite-Life Real Estate Investment Trusts
This study analyzes the investment performance of real estate investment trusts, comparing the finite-life trusts (FREIT) with traditional REITs and stock returns. The results indicate that the FREITs performed more poorly than the REITs, with both the FREITs and REITs underperforming the market index over the period studied. It was also found that while portfolio risk diversification benefits may exist for the REITs and FREITs, it is not clear that the reduced risk is warranted by the large reduction in returns. Finally, this research shows that little total or unanticipated inflation hedging capability exists for the REITs or FREITs over the period studied, although anticipated inflation hedging capabilities were found.
Dispersive Gap Mode of Phonons in Anisotropic Superconductors
We estimate the effect of the superconducting gap anisotropy in the
dispersive gap mode of phonons, which is observed by the neutron scattering on
borocarbide superconductors. We numerically analyze the phonon spectrum
considering the electron-phonon coupling, and examine contributions coming from
the gap suppression and the sign change of the pairing function on the Fermi
surface. When the sign of the pairing function is changed by the nesting
translation, the gap mode does not appear. We also discuss the suppression of
the phonon softening of the Kohn anomaly due to the onset of superconductivity.
We demonstrate that observation of the gap dispersive mode is useful for
sorting out the underlying superconducting pairing function.Comment: 7 pages, 12 figures, to be published in J. Phys. Soc. Jp
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