Yoshifumi Harada

Dynamical Scaling for Sound Propagation in Critical Binary Mixture

Sound absorption measurements for the critical binary mixture of 3-methylpentane-nitroethane have been made over a wide frequency range, 10 -1 <ω * <10 6 , to determine the universal function based on the extended dynamical scaling idea.

An Improvement of Absorbing Boundary Condition Based on Algorithm of Constrained Interpolation Profile Method for Finite-Difference Time-Domain Acoustic Simulation

In this study we examined an improved reasonable absorbing boundary condition (ABC). We examined ABC on the basis of the algorithm of the constrained interpolation profile (CIP) method for finite-difference time-domain (FDTD) acoustic simulation. Analysis of one-dimensional sound propagation with CIP-ABC was implemented. The results obtained in this study clarified that improved CIP-ABCs have better absorption performance than first-order Murs ABC. That is, CIP-ABCs maintain a reflection coefficient that is lower than that of Murs ABC in all frequency ranges.

Ultrasonic Absorption of n-BuOH-Water System with Hypercritical Point

Sound absorption of n-BuOH/H 2 O/Ca(SCN) 2 system with a hypercritical point (HCP) has been measured along the lower critical solution temperature (LCST) line. The critical divergence decreases near HCP. The equivalence of the HCP state and “pseudocritical” state is pointed out.

Critical Divergence of Ultrasonic Absorption in Binary Fluids

Ultrasonic absorption measurements for a critical binary mixture of 3-methylpentane-nitroethane have been made over a wide reduced frequency range, 10-1<ω*106; ω*=ω/ωc, where ω is the frequency of sound and ωc is the relaxation frequency. Near the critical temperature Tc=26.50°C a critical divergence of sound absorption was observed. The experimental results were analyzed numerically within the framework of the existing mode coupling theory for sound propagation. In order to clarify the discrepancy between the theory and the experiment, a computer calculation was made on a set of critical relaxation curves and temperature dispersion relations. As a result, it is shown that the existing mode coupling theory breaks down over a wide range of frequency and temperature. The universal scaling function for this binary mixture has been derived empirically using the extended dynamical scaling approach.

Localized Traveling Wave Front in Binary Fluid Convection

We performed an experiment on Rayleigh Benard convection in a binary fluid in the strong non-linear regime in a slot channel. Double localized traveling wave (DLTW) state was realized near the saddle node point. We have measured the local dynamics at the fronts which separate a convection region and a conduction region in the DLTW and found the chaotic dynamics at the fronts. We suggest that the fronts in DLTW as a cohernt structure are stabilized by the chaotic dynamics.

Intermittency in the Coupled Chaos Oscillators

We performed a simulation of the coupled chaos oscillator which consists of two Chua circuits using a circuit simulator and found an on-off intermittency near the transition to synchronized states. A phase diagram with two parameter space which are a control parameter of the Chua circuit and the strength of the coupling between the circuits was obtained. A complicated route to complete synchronized state was found with increasing the strength of the coupling under the fixed control parameter R around the bifurcation point to chaotic state with a double scroll attractor.