No abstract

Mechanical testing of glassy and rubbery polymers in numerical simulations: Role of boundary conditions in tensile stress experimentsThe vacuum deposition of metals onto poly (dimethylsiloxane) (PDMS) gels was studied as a function of the crosslink density and the polymer substrate temperature during the deposition. Reflectance and conductance measurements were used to characterize the quality of the resulting metal films. Variations in the measurements were found to depend on the substrate temperature during metallization and on the particular metal used. For most cases, the variations of conductance and reflectance can be accounted for by cracks in the metal film and the coarseness of the surface texture.

No abstract

No abstract

No abstract

A simple regular electrode structure for surface acoustic wave (SAW) devices is proposed. The structure consists of an interdigital transducer in the form of a ring placed on the Z cut of a hexagonal piezoelectric crystal. Finite thickness electrodes produce the known slowing effect for a SAW in comparison with this SAW on a free surface. The closed “slow” electrode region with the “fast” surrounding region forms an open waveguide resonator structure with the acoustic field concentrated in the electrode region. If the radius of the structure is large enough for a given wavelength, an acceptable level of radiation losses can be reached. The electrical admittance of such resonator does not have sidelobes.

A SAW resonator filter using not only transverse but also longitudinal modes is presented. The design principle permits to construct four-pole filters without cascading or parallel connection. The input and output transducers arranged side by side have equal construction characterized by unsymmetrical withdrawing weighting. Neighboring disturbing longitudinal modes are suppressed due to weighting determined by an iterative procedure. The successful application of the principle to a device is demonstrated by experimental measurements.

The results of an ultrasonic study of SrTi03 in the temperature range from 20 to 120K using an electrostrictive interdigital transducer for longitudinal waves and e piezoelectric transducer for shear waves have been presented. A thermally activated relaxation loss mechanism due to straininduced domain wall motion has been observed in the tetragonal phase of SrTiO3. Below 40K anomalies in the velocity and attenuation have been found for both longitudinal and shear waves. The decrease of the velocity has been connected with the anomalous temperature behavior of the elastic constant c44 and peaks of the attenuation could be explained by fluctuations.