Internal friction in two kinds of iron-manganese alloy which contain Mn 17.5% and Mn 12.8% respectively and one kind of copper-aluminum alloy containing 13% Al were measured with a torsion pendulum, and internal friction peaks were observed in the temperature range in which the martensite or reverse martensite transformation is taken place. The condition for the appearance of this internal friction peak is that it occurs only when accompanied by the process of martensite-type transformation.Systematic observations were made with iron-manganese alloy containing 17.5% Mn, and it was found that the height of internal friction peak increases with the increase of the rate of heating (or cooling) or the stress, decreases with the increase of the frequency of vibration or the carbon content in the specimen. All these may be explained by the reason that the more the amount of new phase has transformed in one period of vibration, the larger is the internal friction.The mechanism of the internal friction peak was discussed. The conclusion was reached that because of the suddeness of the formation of martensite, the applied external forces due to torsion pendulum may be considered as constant during the time of formation for martensite plates, and since half of the work done by the external forces during the alteration must be lost as confirmed by the calculation of interaction energies between stresses and iuhomogenities, it consequently gives rise to the substantial portion of internal friction. On the other hand, the stress-induced phase transformation also gives rise to a minor portion of internal friction.

An equivalent circuit of transistors operating in saturation region is suggested. This circuit contains a transistor operating in active region and a diode biased in forward direction. By using this equivalent circuit, the physical meaning of storage time of transistors may be explained more intuitively. With this, the storage time in drift transistor, Which is common base connected, has been investigated. By solving the continuity equation, the steady state and the transient components of the densities of minority carriers in diode near the p-n-junction is obtained. By setting these two components equal in magnitude and opposite in sign, we get a formula, from which the storage time may be determined. The storage time in some special cases has been calculated. The results show that the storage time depends upon the life time of minorities and the surface recombination velocities both in base region and in collector region. This may be a guide for design a transistor with more short storage time.

Three different forms of coupling through a small hole are treated by approxi mate methods, which are justified from good physical reasoning. These are the end on coupling between a rectangular and a circular waveguides, the coupling between a TE₁₀ mode in a rectangular waveguide and a TM₁₂₀ mode in a circular cavity through a circular hole in the side wall of the circular cavity and the coupling between a TE₀₁ mode in a rectangular waveguide and a TM_mn mode in circular waveguide through a circular hole in the side wall of the latter. The purpose of this paper is to demonstrate the methods of handling problems of complicated microwave component parts. A few formulas developed in this paper are believed to be new and useful in design works.

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This paper describes a new method for refining super-pnrity Ga (99.9999%). By means of this method it provides multiple zone on one side of the helix of plastic tubing in which the material to be refine1 is filled. Thus when the helix rotates, the melting zones travel endlessly throughout the specimen. The efficieney of this arrangement is thought to be higher than that of the conventional one.

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