This paper describes the results of investigating the microscopic features of a commercially available 35°-rotated Y-cut (ST-cut) quartz surface using atomic force microscopy (AFM) and X-ray diffraction analysis. X-ray diffraction analysis suggests that distortions in the peaks are due to the existence of a dislocation or plane slip near the surface, but precise analysis was impossible in this experiment. Data from AFM showed that a flat area with an interesting particle image exists on the surface along with a heterogeneous damage layer at a depth of about 30 nm.
150 MHz rectangular AT-cut quartz crystal units were prepared by means of photolithography. For the elimination of the effect on a frequency response by the mechanically damaged layer, chemical etching on both sides was employed. Gold evaporated films were used as the electrodes for frequency stability during long-term driving. As a result, crystal units which had excellent frequency stability during long-term driving and low crystal impedance were obtained. Furthermore, a Colpitts crystal oscillator was constructed, and some experimental data are presented.
A comprehensive analysis of gened relativistic spacetimes which admit a shearfree, irrotational and geodesic time-like coogruence is presented. The equations governing the models for a gened energy-momentum tensor are wrilten down. Coordinates in which the metric of such spacetimes takes on a simplified form are established. The general subwses of 'zero anisotropic stress', 'zero heat-flux vector' and 'two-component Ruids' are investigated. In particular, perfect-fluid Friedmann-Robertson-Walker models and spatially homogeneous models are discussed. Models with a variety of physically relevant energy-momentum tensors are considered. Anisowopic fluid models and viscous fluid models with heat conduction are examined. Also. models with B perfect Ruid plus a magnetic field or with pure radiation. and models with two non-collinw perfect fluids (satisfying a variety of physical conditions) are inwtigated. In particular. models with a (single) perfect Ruid which is tilting with respect to the shem-free, vorticity-free and acceleration-free time-like congruence are discussed.PACS numbers: 0420J. 9880H
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