The purpose of the present investigation was to obtain the relation between the absorbing energy of shiled plates in resisting the penetration by a rifle bullet and the physical properties of the material of the plate.
For the purpose mentioned above, we obtained at first experimentally the so-called “characteristic curves” of the shielding efficiency of the various metals under the conditions of three different initial velocities of the bullet, and secondly, based on the results of the above-mentioned experiments, the following relation was deduced
v₂=v₁-2/mv₁(At²+Bt⁴),
where v₁, v₂, m and t denote the initial and residual velocity of the bullet, the mass of the bullet and the thickness of the shield plate respectively.
Next, using the above-mentioned experimental results, we arrived at the following results that A and B, the coefficients of the resistance, depend respectively on the hardness (H), the internal viscosity (μ) and also on the thermal diffusivity (K) of the metal of the shield plate, connected with each other by the following expression
where y=A or B, x=μH/K; a, b are the constants depending merely on the initial velocity of the bullet.

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The solubilities of hydrogen in binary alloys, whose equilibrium diagrams are of simple and typical types, such as a single (Cu-Ni system) or two series of solid solution (Fe-Co system) or a mixture of two saturated solid solutions (Co-Cu system) or of two phases lying between compounds (Ni-Sb system), were measured, and the results were explained with the aid of equilibrium diagrams. The conclusions reached are as follows: -
Solubilities of hydrogen in the alloy forming a single series of solid solution change with the variation of composition, indicating a continuous curve with or without a maximum point, while those in the alloy forming a mixture of two phases change in a linear relation with a change of composition, and also the solubility curves abruptly change by the transformation or indicate a broken point at the composition of a stable compound.

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This paper contains the results of experiments on the corrosion of copper containing various amounts, Ag, A1, Cd, Co, Cr, Fe, Mn, Ni, P, Sb, Si, Sn and Zn, when immersed in 10 per cent hydrochloric and sulphuric acid solutions. The resistivities of many famous copper alloys against the acids were also studied, and from the results of the above experiments, many alloys were prepared and then compared their resistivities under the same acids at room temperature. According to these experiments, the resistivity of 10% A1-Cu alloy against 10 percent hydrochloric acid was the best and many alloys having better reseistivity than that of Ampco metal were found. In the case of 10 percent sulphuric acid good acid-resisting alloys such as AS4 and AS5 which are better than 10% A1-Cu alloys and Ampco metal were found. The appearance of the specimens of copper, Ampco, Everdur, 10% A1-Cu and newly prepared alloys as attacked after 70 days or 368 hours by 10 per cent hydrochloric and sulphuric acids are respectively shown in photographs.

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The effect of carbon on the allotropic transformation of cobalt is thoroughly investigated by means of microscopie, dilatometric and magnetic analyses, and a revised. equilibrium diagram is proposed. The allotropic transformation point of cobalt lowers at first with the increase of carbon and reaches the lowest temperature at about 0.1% C. With a further increasing content of carbon the transformation point rises, and by the peritectoid reaction at 502° and 0.27 per cent carbon α-phase decomposes to β-phase and graphite. According to the cooling curves, the transformation point lowers with the addition of carbon and at 0.25% C and 341° a eutectoid reaction occurs.

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Sn, Zn, Al, Cu and brass were sprayed on glass plate with electrically operated pistol under various conditions, and the forms and sizes of their particles were examined from their microphotographs. The air pressure is an important factor affecting the size, that is, the size decreases considerably as the pressure rises. The spraying distance, the distance between the pistol and the articles to be coated, has also a great influence upon the size, while the arc voltage and the wire feeding speed has a very little. influence. From the form of each particle, it is deduced that the disintegration and the association of the particles occur during the transportation. And also, it was possible to observe the orientation of the particles along the track of coating.

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