Application of the photo-elastic method to measurement of dynamic stress distribution for NS-GT cut quartz crystal resonators
NS-GT cut quartz crystal resonators are widely used as a frequency standard element in consumer products and communication equipment. The vibration mode of the resonators was analyzed by the finite element method (FEM) because they have a complicated shape. As a result, an asymmetrical vibration mode at the main resonant frequency has been obtained by the FEM simulation. But, it is necessary to confirm the asymmetrical vibration mode experimentally because it is just a simulation. In this paper, stress distributions of the NS-GT cut quartz crystal resonators are measured experimentally by using a dynamic photo-elastic method when the resonators are vibrating in the resonant frequency; thereafter, vibration modes of the NS-GT cut resonators are estimated with the experimental data of the stress distributions. This experiment for the NS-GT cut quartz crystal resonators exposes the existence of a twisted asymmetrical vibration mode at the main resonant frequency, with the magnitude of the twisted vibration in proportion to thickness of the resonators.
Measurement of vibration modes of the NS-GT out quartz crystal oscillating in the by-resonant frequency
Stress distributions of two samples of the NS-GT cut quartz crystal resonator, one of which had a thickness of 80 /spl mu/m and the other 150 /spl mu/m, were measured by the dynamic photo-elastic method as the resonators were vibrating in each by-resonant frequency. Thereafter, vibration modes of those resonators have been estimated by the experimental data of obtained stress distributions. The estimated vibration mode of the resonator of 80 /spl mu/m coincided with the result of the finite element method simulation (FEM). The vibration mode of NS-GT cut quartz crystal resonators was a simple extension mode within z'-direction at the by-resonant oscillation. The resonator of 150 /spl mu/m does not coincide with the result of the FEM. It has a very complicated twist asymmetrical vibration mode at the by resonant frequency. We can only estimate the vibration mode of the resonator of 150 /spl mu/m experimentally by using a dynamic photo-elastic method. The vibration mode of the NS-GT cut quartz crystal resonator, when its thickness were thick, and it vibrated in its by-resonant frequency, were composed of the longitudinal stress T3' belong to z'-direction of the plate and the shearing stress T5' caused by the elastic stiffness constant c55 of the plate.
New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum.
Ten novel C21 pregnane glycosides, extensumside C-L (1-10), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, 1H-1H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3β,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure-taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds 1, 3, 4, and 6 in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots.