The characteristics of chemical lasers is reviewed in terms of the chemical pumping reaction and the collisional relaxation processes. The reported values of chemical reaction rate specific to each vibrational level of product molecules are summarized, and the principle of the product excitation is discussed. Also, the mechanism of V-R, T and V-V relaxations is explained briefly by the collision dynamics. The computer simulation of HF lasing system is made through the coupled differential equations of kinetics including the pumping reaction, the V-R, T and V-V relaxations, and the stimulated transitions.
Liquid crystals are being used in a variety of display devices which are based on electro-optical effects. In this paper, the liquid crystalline properties of liquid crystal materials and their molecular structure are discussed, especially from the view-point of a mesomorphic temperature range; the conductivity and temperature effects on the cut-off frequency of electrohydrodynamic instability in electrolyte-doped liquid crystals are studied to elucidate the limit in the operating temperature and frequency of liquid crystal display devices; the various orienting techniques and additives to realize the homeotropic and homogeneous alignment of liquid crystals are briefly described, and the representative electro-optical effects in liquid crystals used in display devices are surveyed.
This paper describes a method by which the processing of three dimensional information can be done by numerical reconstruction from an ultrasonic hologram using a digital computer. This numerical method gives not only the intensity but also the phase of the reconstructed wavefront. The intensity term shows the shape and the phase term shows the unevenness of the reconstructed image. The phase distribution of the reconstructed image is flat for a plane object and variable for a three dimensional object. It is possible to measure the unevenness of the original object from the phase distribution of the reconstructed wavefront. In the experiment, the magnitude and direction of the gradient of the object were quanti-tatively measured from the phase term of the reconstructed wavefront made by the numerical method.
The etch pit density was measured along the ‹111› axis in an N-type GaAs crystal annealed at 900°C under excess arsenic pressure ranging from 20 to 4000 Torr. After annealing, many new etch pits appeared just around the original dislocations and the maximum density was observed in the inside of the crystal. The density of an etch pit which appeared due to annealing increased with the decrease of excess arsenic pressure. From these results, it is supposed that As vacancies increased due to annealing coagulate around the original dislocations, thus forming new large defects. It is also suggested that new defects form dislocation loops because new etch pits appear and vanish in pairs during the etching of a specimen. At a higher arsenic pressure than 80 Torr, Ga vacancies, As interstitials and their complexes with other defects may be one of the factors of making new defects.
Electrical properties of the polycrystalline film of stannic oxide, prepared by oxidation of metallic tin in the air, are investigated under various environmental conditions, such as in N2-gas, dry-air and moist air at room temperature. In these experiments, voltage-current hystereses phenomena are observed with the voltage increasing and decreasing at the rate of 1×10-2 (volt•sec-1). In moist air, an extra-ordinary voltage-current hysteresis depending on humidity are observed.
A new type of electrochromism was found on titanium oxide prepared from the hydroly-sis of titanium tetrachroride with dilute hydro-chloric acid. To prepare the electrochromic panel, the titanium oxide powder with or without resin binder was sandwitched between two NESA glass electrodes. By applying a DC voltage (10_??_200V) to the electrodes, the color of the layer near the cathode changed rapidly from white to dark blue or black, and the dark color disappeared quickly to the original white by cutting off the voltage. The optical density of the dark color was 0.5_??_0.6 and the half life time of the colored state was about 2 seconds at room temperature.