"Resonance" phenomena in thermal diffusion processes in two-layer   structures
  The dependence on chopper frequency of the effective thermal diffusivity and effective thermal conductivity in photoacoustic experiments is discussed. The theoretical model of a two-layer structure at rear-surface illumination in the high frequency limit is considered. It is shown that the effective thermal diffusivity presents ``resonance'' while the effective thermal conductivity sharply changes its magnitude and sign. Such ``resonant'' behavior strongly depends on the surface thermal conductivities associated with the interface thermal contacts. 
Yu. G. Gurevich, G. N. Logvinov, N. Munoz-Aguirre, L. Martinez-Perez