Historical and philosophical considerations on photometric unit system are introduced and absolute measurements of luminous intensity referring to the black body, which has been realized in various national laboratories, are reviewed. Investigations of absolute radiometers for the purpose of newly establishing the magnitude of the luminous flux unit are also surveyed.
In an attempt to establish a method for controlling the particle size of fine silver powders for the experimental use of thick-film materials, particle size and their distribution characteristics of silver powders prepared by chemical deposition from AgNO3 solution with NaOH and HCHO solutions were studied with correlation to the reaction conditions. The effect of batch size on the precipitation reactions and the influence of gelatine, added to both AgNO3 and NaOH solutions, on the particle shape and size of the silver powders were also studied using an electron microscope. A new method named “drop-to-drop method” for the preparation of the silver powders consisting of spherical particles the sizes of which can be regulated within the range from 0.1μm to 0.02μm with gelatine has been developed. The mean particle size deviation of the silver powders thus obtained was found to be 22.5%.
Bending piezoelectricity and bending electrostriction are observed in films of poly (vinylidene fluoride), poly (vinyl fluoride) and nylon 11, when they are elongated and polarized by a large static field at 70_??_90°C. When any of the above films with one end clamped is exposed to a low frequency alternating field, the other end vibrates. In the case of poly (vinylidene fluoride) film of 4cm long and 0. 002 cm thick, the vibration amplitude amounts to approximately 0.15 cm when the voltage of 300 volts is applied to the film. This value is too large to be reasonably explained by the bending effect of the bimorphic transducer action resulting from a lack of uniformity. By the direct and inverse effects, the constants of bending piezoelectricity were measured. As the values of the three constants namely, of piezoelectricity, bending piezo-electricity and bending electrostriction, show similar decrements when films are annealed in the vicinity of poling temperature, it can be supposed that the change of the constants is similarly relatad to the change of spontaneous polarization due to poling process.
The energy distribution of transmitted secondary electrons from some porous films was measured by an ac-retarding field method. Surface potential could be obtained from the rising point of the energy distribution curve. Variation of yield with surface potential was measured, and a relationship independent of mesh voltage was found between yield and surface potential for constant primary energy. The resistance of the porous film under primary electron bombardment was estimated from the values of saturated surface potential and yield. This value was much lower than the intrinsic resistance of the film. Stability of secondary current from porous films was considerably improved when they were prepared by simul-taneous evaporation of KCl and Al in an argon atomsphere. Secondary electron emission mechanism of thin porous films was discussed using the channel electron multiplier model.