Spin-glass transition in bond-disordered Heisenberg antiferromagnets coupled with local lattice distortions on a pyrochlore lattice

Motivated by puzzling characteristics of spin-glass transitions widely observed in pyrochlore-based frustrated materials, we investigate effects of coupling to local lattice distortions in a bond-disordered antiferromagnet on the pyrochlore lattice by extensive Monte Carlo simulations. We show that the spin-glass transition temperature \TSG is largely enhanced by the spin-lattice coupling, and furthermore, becomes almost independent of $\Delta$ in a wide range of the disorder strength $\Delta$. The critical property of the spin glass transition is indistinguishable from that of the canonical Heisenberg spin glass in the entire range of $\Delta$. These peculiar behaviors are ascribed to a modification of the degenerate manifold from continuous to semidiscrete one by the spin-lattice coupling.Comment: 4 pages, 3 figures, major revisions, accepted for publication in PR

Localizing Acoustic Energy in Sound Field Synthesis by Directionally Weighted Exterior Radiation Suppression

A method for synthesizing the desired sound field while suppressing the exterior radiation power with directional weighting is proposed. The exterior radiation from the loudspeakers in sound field synthesis systems can be problematic in practical situations. Although several methods to suppress the exterior radiation have been proposed, suppression in all outward directions is generally difficult, especially when the number of loudspeakers is not sufficiently large. We propose the directionally weighted exterior radiation representation to prioritize the suppression directions by incorporating it into the optimization problem of sound field synthesis. By using the proposed representation, the exterior radiation in the prioritized directions can be significantly reduced while maintaining high interior synthesis accuracy, owing to the relaxed constraint on the exterior radiation. Its performance is evaluated with the application of the proposed representation to amplitude matching in numerical experiments.Comment: Accepted to International Conference on Acoustics, Speech and Signal Processing (ICASSP) 202

Critical property of spin-glass transition in a bond-disordered classical antiferromagnetic Heisenberg model with a biquadratic interaction

Motivated by puzzling spin-glass behaviors observed in many pyrochlore-based magnets, effects of magnetoelastic coupling to local lattice distortions were recently studied by the authors for a bond-disordered antiferromagnet on a pyrochlore lattice [Phys. Rev. Lett. 107, 047204 (2011)]. Here, we extend the analyses with focusing on the critical property of the spin-glass transition which occurs concomitantly with a nematic transition. Finite-size scaling analyses are performed up to a larger system size with 8192 spins to estimate the transition temperature and critical exponents. The exponents are compared with those in the absence of the magnetoelastic coupling and with those for the canonical spin-glass systems. We also discuss the temperature dependence of the specific heat in comparison with that in canonical spin-glass systems as well as an experimental result.Comment: 4 pages, 2 figures, proceedings for LT2

Temperature Dependency of Bond Strength of Polyvinyl Acetate Emulsion Adhesives for Wood

Bond strengths of PVAc emulsion adhesives were evaluated in the range from -130 to 140 C in both tensile shear and tensile cross-lap joints of wood. Both shear and tension bond strengths strongly depended on rheological properties and tensile strengths of adhesives over the entire temperature range, and the maximum peaks of each bond strength and the film strength were observed around the Tg of PVAc. Higher shear bond strengths were observed in the lower temperature range, while the other bond strengths declined markedly. This phenomenon was explained by the possible occurrence of mechanical interlocking at wood surface and difference of its effectiveness with the direction of stress on the joint. Furthermore, a high amount of grafting effectively fortified both the bond and film strengths of adhesives throughout the temperature range investigated