In this paper the stress distributions around two openings (an elliptical goaf and a circular drift) situated in parallel in a plane are solved by using the complex stress functions and conformal representation.
First of all computations are made for such two examples as the center of the drift has the co-ordinates (8, -6) and (13, -6) which are represented in (x₁, y₁) co-ordinates.
The results show that stress distributions around the goaf are almost same as the case that the drift is non-existent, except the limited region of the periphery of the ellipse facing to the drift, but that the stress distributions around the drift are fairly different from those when the ellipse does not exist.
Furthermore the stress concentration around the drift is estimated where a principal stress acts on the plane with an inclination of α to x-axis.
As a result it is found that the maximum and minimum values of stress concentration around the drift and the position that they occur are varied greatly with α.
And the most dangerous position of the drift is near to a tip of the elliptical goaf.

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In this paper, the authors considered the two dimensional models of slurry that have large volume fraction of discon -tinuous phase by using the electrolytic-bath method and numerical method.
The main results obtained are as follows:
(1) The experimental results obtained by the electrolytic-bath method agree well with the results obtained by numerical method, and this experimental method has merit that the effectiveness of factor is appeared in clearly.
(2) In the models considered in this paper, one in which the discontinuous particles are arranged at random is shown most macroscopic homogenuous, and it is considered that this is the hest model in this paper.
(3) In the models predicted by other investigators, the mixture shown by Powers agrees best with our results.

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The positioning effect of the cylinder ports of air-passage-ways to the fore- and rear-chambers in the valve on the performance of an automatic air-rock-drill was studied theoretically and experimentally by making cylinders with the ports positioned near the exhaust port of air.
The results obtained in this study are as follows:
(1) The theoretical results calculated by the proposed theory in this study fairly well coincide with the experimental results obtained on the performance of the above cylinders.
(2)The average velocities of foregoing and returning valves increase linearly with input air pressure independently of the position of the above-mentioned ports in the cylinder. The velocities increase as inner pressure in the cylinder, when its port is open, increases and air in the chamber opposite to a compressed chamber of the valve is exhausted sufficiently.
(3)In case of a constant length of piston and a short interval of the cylinder ports, the valve motion is remarkably affected by the conditions of exhausting air in the valve. Therefore, interrelation of length of piston and diameter of the exhaust port in the valve as well as location of the cylinder ports must be considered when designing an air-rock-drill.
(4)In order to increase the blow-velocity of piston, the time when compressed air gets into each chamber must be delayed in the foregoing and returning process of the piston, reducing the compression ratio of the fore-chamber and increasing the piston-stroke.
(5)For an automatic air-rock-drill, the theoretical design of the drill with better performance could be considered since it is possible to control the time when compressed air enters the fore- and rear-chamber of the cylinder.

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In this paper, some problems about propertv of ANFO mixtures is examined, to change our easy preconception.
Each conclusion about these is as follows.
(1)The condition of confinement is one of the most important factor to initiate ANFO.Even enough amount of primer can not initiate ANFO (permitted by JIS) without adequate condition of confinement.On the contrary, if the condition of confinement is adequate ANFO can be initiated perfectly only with a No.6 cap (it is standard cap in Japan).
(2)Lead block expanding test for ANFO can be carried out without any modification.Ballistic mortar test can also be done with such a simple modification as to pack ANFO with aluminum foil and to stick the bottom of it to the end wall of chamber, or as to charge ANFO into a cylindrical tin foil with a tin plate on the bottom of it.and to explode it in the middle of chamber, so as to promote the cavity effect of cap. For reference, R.W.S of ANFO is 81.2.
(3) Ordinary necessary amount of primer should not be decided per total amount of ANFO in bore hole, but per diameter of bore hole.
(4)A postscript: ANFO which is exposed below the temperature of-18°C apt to break into fine particle, consequently, it is become more Sensitive.

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In this paper, the formulae estimating the average heat transfer coefficient (α_m) from the airway surface to the air stream in a mine gallery are proposed. They are the results of the experimental model studies which are reported in this paper and in previous ones. One of the main points is that the formula most suitable to the surface condition of the gallery has to be used.
On the base of the similarity law of heat transfer, the validity of the proposed formulae was checked with the “in situ” data already published. The estimated values of the formulae and the data were in good agreement.
Also, a generalized formula (Eq.(9)) applicable to the airways of various surface conditions was obtained. From this formula, α_m can be estimated, when the mean diameter (Dm), the Reynolds number (Re) and the friction factor (f) of the gallery are known. In case of the uniformly granular type rough surface, Eq.(9) may give smaller values in the range of 45 percent. On the other hand, in case of the timbered gallery with steel or wooden timberings etc., Eq.(9) may give larger values in the range of 45 percent.

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The use of suspension electrode for electrolytic refining of lead with a sulfamate electrolyte has been studied.
In current-potential measurements for suspension cathode and anode of lead particles it has been shown that the polarization on a fixed electrode (feeder) is only 10mV at a current density of 50A/dm².
The electrolysis is then carried out with a disk-like cell (13cm ID, 2.4cm H) which consists of a iower cathode chamber, an upper anode chamber, and a diaphragm between these chambers. Lead particles are kept in suspension in both chambers by vertical vibration and simultaneous horizontal shaking of the cell. At a cell current of 13.3A (current density: 20.9A/dm²) the cell voltage is 1.8V and the current efficiencies for the cathode and anode lead particles are about 100% and 110%, respectively.

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