In this study,we investigate the nonlinear coupling magneto-electric(ME) effect of a giant magnetostrictive/piezoelectric composite cylinder.The nonlinear constitutive relations of the ME material are taken into account,and the influences of the nonlinear material properties on the ME effect are investigated for the static and dynamic cases,respectively.The influences of different constraint conditions on the ME effect are discussed.In the dynamic case considering nonlinear material properties,the double frequency ME response(The response frequency is twice the applied magnetic frequency) is obtained and discussed,which can be used to explain the experiment phenomenon in which the input signal with frequency f is converted to the output signal with 2 f in ME laminated structures.Some calculations on nonlinear ME effect are conducted.The obtained results indicate that the nonlinear material properties affect not only the magnitude of the ME effect in the static case but also the ME response frequency in the dynamic case.
A theoretical model taking into consideration the interface effects is established to predict the Seebeck coefficient and the electrical conductivity for a polycrystalline thermoelectric(TE)thin film.The interface scattering mechanisms(including the film-surface scattering and grain-boundary scattering)of the transport electrons in the film materials are revealed.The relations between the Seebeck coefficient,the electrical conductivity and the interface parameters(the film-surface reflection coefficient and the grain-boundary transmission coefficient)are then discussed with respect to the proposed model.The differences in the TE properties between the films and bulk materials caused by size restriction are investigated.The results indicate that the higher grain number leads to stronger grain-boundary scattering and more distinct size effects of the TE properties.In contrast to the surface effect,the grain-boundary effect plays a main role in the TE properties of TE films with polycrystalline structures.
