The efforts in modeling the solid p

The efforts in modeling the solid plate as a piezoelectric material provide opportunities to investigate the effects of fluid dielectric properties such as dielectric permittivity and conductivity. Fig. 5 shows two sets of dispersion spectra for two bi-layer systems with fluid layers of two different fluid dielectric permittivities. Here the propagation direction is Φ = 60°. Along this direction, the effects of varying the fluid dielectric constant are most pronounced. The first bi-layer system has a water layer with a fluid dielectric permittivity of εwt = 79.8ε0, where ε0 is the dielectric permittivity in a vacuum. The second bi-layer system is modeled to have a fluid layer with a reduced dielectric permittivity of 0.7εwt = 55.86ε0. The dispersion spectra are shown to be influenced by the fluid permittivity. In particular, bi-layer modes near the low-frequency part of the S0 mode are most influenced by the reduction of dielectric permittivity. With the decreased dielectric permittivity, these SF modes have higher phase velocities. Withthe fluid further modeled as a lossy dielectric medium, Fig. 6 shows the influences of fluid conductivity on the dispersion spectra of guided modes [19]. The fluid modeled as a lossy dielectric media has a complex dielectric permittivity of εf = ε′ + i(σ/ω), where ε′ is the real dielectric permittivity (now 79.8ε0) and σ is the fluid conductivity. These two sets of dispersion spectra presented in Fig. 6 correspond to (a) a water layer without conductivity and (b) a water layer with a fluid conductivity of σ = 0.1 Ω−1·m−1. Again, the effect of fluid conductivity has the most pronounced effect along the propagation direction of Φ = 60°. The fluid conductivity further reduces the phase velocities of the SF modes.