Different theories on the Franz-Keldysh effect are briefly described with the experimental results on the electro-absorption effect for GaAs, Si and other materials, and the experimental results are compared with the theories. The experiments and the analysis of the electro-reflectance effect are also introduced. The practical applications of the Franz-Keldysh effect such as a modulating device of light intensity, a light deflection device and a light-activated negative registance device are discussed. According to the authors' work on the electro-absorption effect in CdS crystals, 90_??_95%' modulation has been obtained under a modulating field of 0.95×105 V/cm, using a specimen of 100μm thick and wavelength of 5120Ä. The frequency response of the effect has been concluded to be flat up to 107 Hz from the result in an application of a pulsed voltage.
A new classification of the snowcover is discussed, which is based upon the mechanical deformation of the natural snowcover beam. For example, a numerical factor eA of the beam is calculated as the ratio between the deformations when the beam is assumed of elastic or plastic property; and the beam of eA_??_1 is defined as an elastic one. Thereby the snowcover beam can be classified into three kinds: (1) elastic one, (2) plastic one for normal stress and rigid for shearing stress or (3) plastic one for shearing stress. Observed values of eA was 6_??_104 and the snowcover beams may be of the property (2). Now eA's are bound by certain maximum value eA* characterized at the district under consideration, and therefore eA* can be used to classify the snowcover. The value of eA* at the beginning of March is found as 60 at Fukui district and 104 at Hokkaido. It was obtained also that the elastic model of the snowslide in his previous report can be applicable only for the snowcover of the eA*'s less than 100, and that another type of the snowslide can be expected for the snowcover of eA*'s much greater than 100.
In order to find the radioactive γ or X-ray source suitable to the determination of ash content of coal by X-ray backscattering, various sources of energy below 60 keV have been observed. Monochromatic X-rays of energy between 10 and 35 keV were supplied by γ-ray excited X-ray sources which consist of the Am241 γ-ray source and various target materials of atomic number in the range from 35 to 56. Commercially available sources as Am241, H3/Zr and Fe55 were tested too. High sensitivity in the analysis was obtained with the sources of energy between 9 and 30 keV. The main difficulty of this method of analysis is that the intensity of scattered X-rays is not solely due to the ash content but dependent on the composition of ash, in particular, the content of Fe2O3. With Fe55 or the y-ray excited Sr K X-ray source the observed intensity of X-rays was independent of the Fe2O3 content. Above results lead to the conclusion that an X-ray source of energy slightly below 15 keV is the most suitable for the purpose.
Solid state Bragg-Gray cavity chamber is developed in which thin plates with various thickness of low-Z silver-activated phosphate glass are used as cavity solid. The method of measurement is improved. After some theoretical considerations, this method is verified to be useful by the experiments. With this method the absorbed dose of the wall material can be measured. Minimum measurable dose is 0.1 rad.