No abstract

Filters based on film bulk acoustic resonators (FBARs) are widely used for mobile phone applications, but they can also address wideband aerospace requirements. These devices need high electromechanical coupling coefficients to achieve large band pass filters. The piezoelectric material LiNbO 3 complies with such specifications and is compatible with standard fabrication processes. In this work, simple metal-LiNbO 3 -metal structures have been developed to fabricate single FBAR elements directly connected to each other on a single chip. A fabrication process based on LiNbO 3 /silicon Au-Au bonding and LiNbO 3 lapping/polishing has been developed and is proposed in this paper. Electrical measurements of these FBAR filters are proposed and commented exhibiting filters with 8% of fractional bandwidth and 3.3 dB of insertion losses. Electrical measurements show possibilities to obtain 14% of fractional bandwidth. These devices have been packaged, allowing for power handling, thermal, and ferroelectric tests, corresponding to spatial conditions.

Owing to the excellent tensile strength and corrosion-resistance of fiber reinforced unsaturated polyester composite, it is expected to solve the corrosion problem of building instead of steel bars in some special occasions. Bonding performance between concrete and FRP rebars was studied by pull-out test,the influences of the surface form, anchorage length and diameter of FRP rebar on bonding strength were discussed in detail.

The internal structure of magnetorheological fluid could change under external magnetic field, as well as its dielectric constant and magnetic conductance. A theoretical model of electromagnetic wave propagation in MRF was established and the basic formula of transmissivity was deduced. Theoretical simulation shows that the electromagnetic wave transmissivity decreases with the increasing of dielectric constant of magnetorheological fluid, and increases with the magnetic permeability. Theoretical analysis indicates that the change of its structure and dielectric magnetic properties of MR fluids is the main cause for the fact that the transmittance could be adjusted under external magnetic field.

In this paper, the dielectric constants of ER fluids with different particle concentration were measured by frequency method, and their electrical conductivities under different external electrical fields were also measured by method of conductivity cell constant. The results obtained from above measurements are as follows: the dielectric constant of ER fluid increases with the increasing of concentration; its electrical conductivity of the same concentration increases with the increasing of electrical field strength; for gradually increasing concentration, the conductivity first increases, then decreases. From analysis, it is suggested that the change of effective ion concentration of ER fluid is an important reason for its variation of conductivity.