Various aspects of surf ace acoustic wave device application are reviewed, focusing on the research and development activities in authors' laboratory since 1972. Filters, delay lines, wave guides, equalizers, resonators and oscillators were fabricated and tested. Their operational principles are described and their present characteristics are assessed compared with those of alternative devices. State of the art in nonlinear and active device application such as convolvers and image scanners are introduced. Problems to be solved and difficulties to be circumvented for surface acoustic wave devices to be practically utilized in these fields are pointed out. Materials and fabrication methods supporting surface acoustic wave technology are reviewed. Desirable properties of piezoelectric surface acoustic wave propagation media are discussed. Potential applications and future progress in prospect of surface acoustic wave devices are described.
A critical survey and a perspective of researches in laser Stark spectroscopy as a tech-nique to investigate vibration-rotation spectra of molecules are presented. After a brief introduction of the principle, the experimental method and the history of the laser Stark spectroscopy, a detailed description of a laser Stark spectrometer developed by the author and of its performance is given. Particular emphasis is placed on the methods invoked to improve the sensitivity and the accuracy of measurement by the spectrometer. A variety of molecules and their related problems of spectroscopic interest which might be studied by the laser Stark spectroscopy are discussed. The minimum detectable absorption attainable by a laser Stark spectrometer under the present state of art is estimated to be of the order of 10-14 cm-1 whereas its ultimate resolu-tion is limited to about ±100 kHz at wavelengths of 5-10 μm.
A movable L tube flow meter enables us to obtain ρQ2 where ρ is the density of fluid and Q is its volume flow rate. As the density of a gas however, is very sensitive to temperature and pressure, density measured at one location is not in general applicable to any other. Therefore, to obtain the mass flow rate of a gaseous substanceby a movable L tube flow meter, it is necessary to know the density at the inlet (or the outlet) end of the tube. For this purpose the density, temperature and pressure at an appropriate position in a flow line and, in addition, the temperature and pressure at inlet (or outlet) section are measured. By this method, it is experimentally shown that the mass flow rate of air as measured is approximately in agreement with theory.
General characteristics of the cross electrode type AC arc plasma generator are given for various operating conditions. A considerable variation of the heat losses at the cross electrode and the nozzle is observed with increasing arc current and gas flow rate. The measurements of the restriking voltage and the dead time of arc current after extinc-tion at each half cycle indicate that the polarity of arc, the magnitude of arc current and gas flow rate have a marked influence on the restriking characteristics. The dynamic behavior of an AC plasma jet is shown by high speed photography. The elongation speed of a jet depends mainly on the arc operating parameters (arc current, gas flow rate), and the duration time of a half cycle of an efficient jet is found to be from 3.5 msec to 6.5 msec.
This paper describes the outlines of the construction and the experimentally confirmed frequency stability of a cesium beam frequency standard which was recently assembled at the National Research Laboratory of Metrology. From the preliminary result of frequency stability measurement, it became clear that the major source of frequency instability for long term came from the change of the phase difference between the two exciting fields. In order to eliminate the change, the support of the feeder waveguide to the cavity resonator was improved. The frequency stability derived from the Allan variance is estimated to be 3×10-11τ-1/2 for short term and 1_??_2×10-13 for long term. The values of short term stability calculated from F values of the Ramsey resonance signals are in satisfactory agreement with the experimental values. By the analysis of fluctuations of various natures existing in the servo system, some useful measures for further improvement of frequency stability are pointed out.
The influence of initial molecular alignment in a liquid crystal (LC) on electrooptical properties of dynamic scattering devices has been studied using linearly polarized light as the incident light. In case the alignment is homogeneous, electrooptical parameters such as the transmittance and response times vary with the polarization direction of incident light and, contrary to expectation, the variations still persist up to such high voltages which induce violent hydrodynamic turbulence of LC; whereas in case of the homeotropic alignment the above variations are not detected. The experimental results have been qualitatively discussed in terms of the relationships between the intial LC alignments and the electric field-induced orientations of LC molecules.
The direction of rotation in a circularly polarized light transmitted through a choles-teric liquid crystal cell was studied by meas-uring the retardation between the ordinary component and the extraordinary component in a compensator placed upon the cell. The chirality of cholesteric liquid crystals was determined by comparing the experimental results with Priestley's theory. It is conse-quently shown that cholesteryl propionate has a left-handed helical structure and cholesteryl chloride has a right-handed helical structure.