This paper describes a mechanism of the newly found convection mode of vibrated granular beds which gives rise to multi-pairs of convection rolls. In beds of glass beads with mean diameters d ≤ 0.5 mm, neither the ambient air pressure nor vessel materials significantly affect the critical vibrational acceleration above which the convection mode changes. Measurements of air pressure within vibrating granular beds at two locations, near the side wall and in the middle of the bed, show different period-doubling bifurcations. There are differences in the phase and the magnitude of pressures between the two measured points. On the basis of these experimental findings we propose mechanisms for two convection modes in vibrated granular beds.

Some experiments concerning the mechanism of the thermal oxidation of silicon, are described. Experiments with a radioactive tracer using the sectioning technique indicate strongly that during the thermal oxidation of silicon the diffusion of oxygen is responsible for the growth of the oxide film. The same technique is applied to the study of the oxidation of copper. A physical picture for the oxidation of metals in general is derived from these series of experiments. Penetration curve for the diffusion of oxygen during the oxidation of silicon is obtained from infrared absorption measurements using the sectioning technique.

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Induced color of shielding window glass of various kinds by γ-ray irradiation is studied. With Co60−1 kc as radiation source, 23°±3°C as irradiation temperature, 105 R/h as exposure dose rate and 105−107 R as total exposure dose, the coloration increases gradually. Volume resistivity of glass and its change by gamma-ray irradiation are measured. 100 V dc is applied to a sheet of glass sandwiched between two electrodes to measure the change of its electric resistance with time. The quantity of induced space charge by radiation is calculated by time integration of the current which is obtained from reciprocal of the resistance. Resistance of high density glass is found to become minimum—hence the current becomes maximum—at the exposure dose of 106 R and increases as the dose increases, but resistance of medium density glass decreases gradually. Change of the resistance is exponential and the charge is always positive at any dose. This testifies that glass is electrized by radiation. On the other hand, linearity is established between the quantity of space charge and the dose in a range of 105 to 4×106 R. This suggests the possibility of the electrization to be utilized for dosimetry. The above not only demonstrates the physical properties of shielding window glass and the effect of radiation on it but seems to help to find the means of preventing the breakdown by radiation of glass.

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