The frequency response of the multilayered acoustic cloak made of isotropic materials is analyzed by the acoustic scattering theory. When concealing a rigid cylinder, the acoustic total scattering cross section (TSCS) monotonically increases with frequency. If concealing penetrable materials, the cloak-induced reverse-phase monopole and dipole resonances can increase the TSCS around the resonant frequencies, while the in-phase monopole resonance decreases the TSCS. The results are confirmed by numerical simulations of the finite element method. © 2008 American Institute of Physics.

We have observed a photoinduced hphase transition (PIPT) in a spin-crossover Fe(II) complex Nafion-[Fe(Htrz)3] film (Nafion is an ion exchange polmer film, and Htrz-1, 2, 4-1H-triazole) from a low-spin (LS) state (S=0) to a high-spin (HS) state (S=2) below 150K. The phototransferred HS state relaxed to the initial LS state, exhibiting a nonexponeential time behavior, which has bee interpreted in terms of the ciical nucleation and subsequent growth of the LS clusters. We have also observed that the decay time Tc is approximately temperature independent inthe low temperature range of 4.2-20K, and then decreases exponentially with temperature.

Thermal diffusivity has been investigated in ordered double perovskite Sr2FeMoO6 measn of transient surface grating technique in te temperatue rage of 300-450K. The thermal diffusivity showas an apprecialve decrese form 39mm/2s at 300K to 37mm/2 at 360K in the ferromagnetic phase, and then steeply drops to 10mm2/s with furtherincreasing temperature above the critical temperature Tc～380K. Such an abrupt decrease of the thermal diffusivity has been ascribed to the structural phase transition at Tc. We further investigate the lattice effect on the thermal diffusivity in A2FeMoO6 (A=Ca, Sr and Ba) by substitution of CA2+or Ba2+ ions for Sr2+ions at 300K. We find that the thermal difusivity increases form 35mm2/s for A=Ca to 41mm2/s for A=Ba. Considering the change of the Fe-O-Mo bond angle and hence the wider one-electrom bandwidth W.

The themal diffusivity has been ivestigatedin double perovskite Sr2MMoO6 (M=Fe, Mn and Co) by means of the mirage effect. We have found that the thermal diffusivity of metallic Sr2FeMoO6 is 0.39 cm2/s, wihich is larger than that (0.33cm2/s) of insulating Sr2MnMoO6 and Sr2CoMoO6. We further investigate the substitution effects of the La3+ions for the Sr2+ions in Sr2FeMoO6 and Sr2MnMoO6, and have found that the thermal diffusivities of both samples significantly increase with the La cncentration. Such an enhancement of the thermal diffusivities has been a scribed ot occupation of the extra itinerant electrons on te conducion Mo4d band.

The second-harmonic sound beam nonlinearly generated by a conical source is analytically described It is shown that the radial second-hamonic beam is distributed as the Bessel function and independent of the porpagation distance. Anoher important feature is that the beamwidth of the second-harmonic component is just equal to 1/2 time that of the fundamental, not 1/√2 times in the general cases. A potential application of this beam in the acoustic noninearity parameter B/A imaging or measurement is also discussed.