This paper deals with the problems of transverse and torsional wave propagation in an infinite thin elastic plate with circular holes. The dynamical moment concentrations along holes are obtained and compared with those for a single hole. When the wave length becomes infinity, it is ascertained that the dynamical solutions tend to statical ones.

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Refrigerant vapors were filled in the high pressure side of a shock tube, and measurements were made as the vapors condensed spontane usly through adiabatic expansion in the rarefaction wave. The experimental observations were analyzed on the basis of the classical nucleation theory, and for each of the test vapors, the surface energy density (or the surface tension) of critical-sized droplets, which corresponds to the activation energy in chemical reactions, was evaluated utilizing the condensation point locus on the P-T plane. It turned out that the estimated surface tension was consistently smaller than the macroscopic value for three kinds of refrigerants studied. In the case of methyl alcohol vapor, for which the expansion rate was varied over a wide range, the condensation locus was found to shift accordingly in agreement with the theoretical prediction. It was also shown that the droplet growth history could be inferred from the temporal change of the light transmission.

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Spreading velocity of a bubble front and thickness of a micro-liquid layer are measured experimentally for two cases-a flattened bubble in a narrow space between a pair of parallel disks, and a bubble in normal boiling at low pressures. In the former case, the thickness of liquid-layer is determined by optical means for a bubble made by spurting air into water and alcohol. In the latter case, the thickness of liquid-layer is determined from the evaporating velocity of the liquid-layer for a bubble in saturated boilling of water at the pressure of 0.11kg/cm² abs. The following empirical formulae are derived from the experimental results : dh/dr=1.4(μU₀/σ)²/3 H1/r(U₀r/ν)¹/2 for a flattened bubble in a narrow space between a pair of parallel disks, and dh/dr=0.65(μU₀/σ)¹/6 1/(U₀r/ν)1/2 for a bubble in normal boiling at low pressures, where h : thickness of a micro-liquid-layer, r : radial coordinate (distance measured from a nucleation center), μ : viscosity of liquid, U₀ : local velocity of a bubble front at the positon of r, σ : surface tension, H : half of normal distance between a pair of parallel disks, and ν : kinematic viscosity of liquid.

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Some experimental studies for examining the maximum heat fluxes in pool boiling of saturated water on partly ill-wettable heating surface are continued. Ill-wettable parts are realized by putting thin layers of silastic adhesive. In the previous report, experiments were carried out varying the width of such a region but in this report the test section has two parallel ill-wettable parts and the distance between these two parts is varied in order to examine their interference. In this case as the heat removal rates change locally, there exists a considerable temperature distribution along the heating surface. Especially in the normal part between two ill-wettable regions nucleate boiling having tolerably high superheat occurs. Such a boiling is examined by measuring the surface temperature, heat transfer coefficient and average void fraction.

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In this paper, the experimental studies for the basic problem of the contact between gear teeth are presented. When a concentrated load acts on an infinite elastic solid, Sneddon's solutions are applied to the contact between gear teeth on the hypothesis that the effect of gear profile can be neglected in discussing local deformation on "line of contact". Correct functions are suggested. These correct functions contain the effect for the deformations with the distance from the free edge to the posiitons where a concentrated load acts on and where deformations are measured. There were applied to the contact between a finite width roller and a same width flat surface. The deflections and the load distribution were evaluated to make use of Sneddon's equation and the correct functions. The evaluatd results with these equations coincided with experimental results. And it becomes clear that the width of a gear tooth should be taken into consideration on the deflection when the width is narrow.

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The generation mechanism of the radial vibration and the axial one of spur gears is theoretically analyzed in consideration of not only the stiffness of shafts and bearings but also the mass of shafts in this report, where the concerned system of an infinite degree-of-freedom is converted to that of a finite one which has the same kinetic energy as the former, based on the assumption that the static characteristics of shafts and bearings can be applied to the dynamic condition. This analysis and the comparison of the calcutated results based on it with the experimental ones indicate that the vibration model, represented by a system of coupled vibration, can give a comparatively good explanation of the characteristics of three-directional vibrations obtained experimentally and that the conversion ratios from the circumferential vibration to the radial and the axial one depend on the combination of gears, shafts and bearings.

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