Zou Xinye

The Band Gaps of Plate-Mode Waves in One-Dimensional Piezoelectric Composite Plates: Polarizations and Boundary Conditions

Theoretical studies are presented for the band structures of plate-mode waves in a one-dimensional (1-D) phononic crystal plate consisting of piezoelectric ceramics placed periodically in an epoxy substrate. The dependences of the widths and starting frequencies of first band gaps (FBG) on the filling fraction and the thickness to lattice pitch ratio are calculated for different polarizations of piezoelectric ceramics under different electric boundary conditions, i.e., short circuit (SC) and open circuit (OC). We found that the FBG always is broadened by polarizing piezoelectric ceramics, and the FBG widths with SC always are larger than that with OC for the same polarization. Our research shows that there are three critical parameters which determine the FBG: the polarized directions, the filling fraction, and the ratio of the plate thickness to the lattice pitch, respectively. Therefore, we can control the width and starting frequency of the FBG in the engineering according to need by choosing these parameters of the system.

Concealing a Passive Sensing System with Single-Negative Layers

We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped with a transparent protective layer), using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed system. The numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak loss. This may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.

Controlling an acoustic wave with a cylindrically-symmetric gradient-index system*

We present a detailed theoretical description of wave propagation in an acoustic gradient-index system with cylindrical symmetry and demonstrate its potential to numerically control acoustic waves in different ways. The trajectory of an acoustic wave within the system is derived by employing the theory of geometric acoustics, and the validity of the theoretical descriptions is verified numerically by using the finite element method simulation. The results show that by tailoring the distribution function of the refractive index, the proposed system can yield a tunable manipulation of acoustic waves, such as acoustic bending, trapping, and absorbing.