The free vibrations (in plane) of a piezoelectric thin plate (polarized in the thickness direction) of an equilateral triangular shape are studied. The finite element method is used to obtain the lowest 24 modes of the plate and the results are as follows. (1) Modes are grouped into three classes according to the displacement of the three symmetrical lines, "Symmetrical lines extensional modes (E modes), " "symmetrical lines bending modes (B modes)" and "mixed modes (M modes and M' modes). " (2) Respective "mixed modes" consist of two degenerate modes, Which is symmetrical with respect to a symmetrical line on one side and antisymmetrical on the other, and are resolved with the perturbation of geometrical symmetry. (3)The difference of the natural frequencies between the analyses with 256 constant-strain triangular elements and the experiments is less than 3% for 3 modes (M_1, M_2 and E_1) and was less than 10% for the other modes. It is also pointed out that certain modes are applicable to a resonator or multiple mode filter.
An autoregressive moving-average with adaptive orders of poles and zeros is adopted as a model for the production process of voiceless stop consonants. Analysis of 90 utterances of CV-syllables containing /p/, /t/ and /k/ indicates that the features of the three voiceless stop consonants can be quite explicitly represented by the trajectories of poles and zeros from the noise burst to the onset of the following vowel. If the orders of the model are optimized for voiceless stop consonants, the sum of the order of the AR scheme n and that of the MA scheme m is less than the order of the conventional all-pole model for vowels. Speech analysis with both adaptive and fixed orders of the model reveals the relation between the reduction of the amount of computation in the feature extraction and the decrease in the estimation accuracy. Separability of the three consonants is also examined for the estimated parameters.
The temperature stability is a very important factor in Surface Acoustic Wave (SAW) devices. At present, ST-cut quartz is widely used to realize a zero temperature coefficient, but it is not sufficient for recent SAW devices. Other more stable cuts should therefore be found. In this paper a new cut of quartz with zero slope temperature is discovered theoretically and experimentally. In the theory a temperature dependence of time delay is calculated and a family of curves giving Euler's angles for zero slope temperature is obtained when the temperature is -10, 20, 50 and 80 degree. Then a new cut with more stable temperature dependence is selected. The new cut of plate is demonstrated experimentally from the theoretical prediction. The resulting temperature dependence is better than the St-cut and the fraction time delay is less than 10 ppm in the temperature range from 0 to 55 degrees. This new cut of quartz must be useful for may SAW devices.
An H-shaped longitudinal resonator mode of a piezo-ceramic has been used as a filter for the intermediate frequency (IF). However, the design of the filter of an H-shaped resonator is not easy because the measured vales of resonant frequency do not agree with the calculated ones, which were roughly given by using its equivalent network theory. In this paper, the H-shaped resonator is investigated by using the finite element method in order to make the design of the filter easy practically. In the first part of this paper, the relations between the dimensions of each several parts of the H-shaped vibrator and the resonant frequencies are definitely shown by some analyses and experiments. The second part contains the analys of vibrational modes ; that is, it is found that the vibrational nodal points in common with both resonances of in-phase mode and out-ofphase mode exist under the condition of some specific dimensions. Therefore, it is expected that, by supporting the resonator at these nodal points, decrease of its quality factor Q can be prevented. This is confirmed experimentally in this paper Finally, one example of the IF filter using this H-shaped vibrator and its filter characteristic are shown.