This paper presents a simplified method, based on the displacement discontinuity method, to conduct stress analysis for tabular mining. In this method, the average displacement discontinuities of each excavated panel are first estimated by considering only mining conditions. Then, displacements and stresses at any point including the ground surface are calculated by substituting the average displacement discontinuities into the solution of an elastic problem for a point dislocation in a semi-infinite elastic medium.
Number of necessary elements to model the problem and program size are so small that the calculation can be executed on personal computers. This method would become a mining engineers' useful tool for strata control.

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In order to control air condition in any specific branch such as coal faces and/or advancing faces in an underground coal mine, the macroscopic characteristics of a complicated mine ventilation network have been investigated, using computer simulation with varying aerodynamic resistances of each branch in the network.
Main results of the paper are as follows; 1) It is shown as one of the macroscopic characteristics of a ventilation network that airflow rate of a specific branch due to varying aerodynamic resistance of a regulator is a linear function of airflow rate in other branches under new condition of the network.
2) The macroscopic characteristics mentioned in 1) is available to select branches for setting a regulator or a velocity sensor to control airflow rate of a specific branch.
3) Provided that the macroscopic characteristics related to airflow rates in the specific branches and two branches with a sensor under the condition of varying aerodynamic resistance of a regulator, measured airflow rates in two branches confirm the aerodynamic resistance of the regulator, and airflow rate in the specific branch can be estimated from the measured airflow rates.
4) Providing that the macroscopic characteristics caused by variation of aerodynamic resistance of all the branches in the network, the branch's varied aerodynamic resistance can be detected by measured airflow rates in two branches with a velocity sensor.
An air distribution in the network can be estimated from the measured airflow rate by using equation 2. The coefficients in the equation are given by the regression lines, in airflow rates between a chord branch and the branch with velocity sensor, for the branches with varied aerodynamic resistance.

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In the case of lifting of manganese nodules by air lift pump, gas-liquid-solid three phase flow is formed in lifting pipe. Accordingly, its lifting characteristics are influenced by the length and diameter of the lifting pipe.
We considered static pressure profile, flow pattern and average hold-up from the experimental results of a 200m vertical test plant and laboratory size small equipments and clarified the influence of length and diameter of lifting pipe for them.
Main results of this study are summarized as follows: 1) From theoretical consideration, we derived dimensionless numbers shown in the equation (8).
2) Analyzing wave form of static pressure at the adjacent point of discharge, fundamental property of flow pattern of both tests is similar and it is noregard to the length of lifting pipe.
3) Profile of static pressure in axial direction of lifting pipe was obtained as shown in Fig. 5.
4) Profile of flow pattern in axial direction of lifting pipe was clarified as shown in Fig. 6.
5) Relations between average hold-up and Froude number in two phase operation and three phase operation were presented by the equations (19) and (26).

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This paper deals with the buckling problem of circular cylindrical shells surrounded with liquid under external uniform pressure as the first stage to analyze the stability of cylindrical offshore structures. A theoretical analysis is performed by means of the Galerkin method on the basis of the Donnell-type equation for shells, taking the effect of the axisymmetric deformation due to the static liquid pressure into consideration. Calculations are carried out for both simply supported and clamped shells and the buckling conditions are determined for various values of the shell geometric parameter Z, liquid pressure parameter p_x, liquid depth ratio l₀ and the external pressure parameter k_p.
The main results obtained may be summarized as follows:(1) The buckling liquid depth ratio to decreases monotonously with an increase in the values of p_x and k_p.
(2) Using the liquid pressure parameter p_x (the ratio of the maximum liquid pressure when the cylinder is surrounded with liquid up to the upper end to the critical uniform pressure p₀, for the empty one), the effects of the boundary conditions and the shell geometries on the buckling condition are almost negligible.
(3) When the cylinder buckles at l₀=1.0 under the surrounding liquid only, the critical value of the liquid pressure parameter is p_x=2.0 regardless of the boundary conditions and the shell geometries Z. Therefore, the cylinder does not buckle for p_x<2.0 and buckles at l₀<1.0 for p_x>2.0.
(4) The effects of the surrounding liquid and the external pressure on the prebuckling and buckling deformation are clarified by means of the contour map representation.

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Flotation is a very important method for separation, condensation, recovery and purification of substances and it is employed satisfactory for technical production. In order to investigate a mechanism of flotation for the soluble inorganic salts, subsequent experiments were carried out as a basic investigation.
We observed whether or not the crystal surface of the soluble inorganic salts is changed to the hydrophobic one by adding a surfactant such as a saturated fatty acid or its sodium salt. Then we discussed the effect of pH on forming the hydrophobic crystal surface.
The results showed that the crystal surface of the soluble inorganic salt was easy to change to the hydrophobic one in the pH range alkaline, and by more carbon number of saturated fatty acid than C₈. The more carbon number of fatty acid increased, the more they changed to the hydrophobic one.
Saturated fatty acid of carbon number C₈-C₁₈ or it's salts are effective to promote forming the hydrophobic surface of the soluble inorganic salts such as sodium or potassium chloride.

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Water content of a packed bed of particles dewatered by a centrifuge and filter is significantly influenced by the drain height of the packed bed. Drain height is used to be measured by Haines apparatus in a gravitational field. However, the measurement of drain height for fine particles less than 50μm diameter is difficult because their drain heights are generally more than a few meters. Therefore, measurement of the drain height of fine particles in a centrifugal force field was investigated.
Experimental work on glass spheres and calcium carbonate powder was carried out using a vertical-axis centrifuge and acrylic dewatering tube. The residual equilibrium saturation of the packed bed from 1 to 4cm high was measured under the centrifugal force ranging from 100 to 4, 500 G. The drain height in a centrifugal force field was obtained from analysis of the curve of saturation of the packed bed plotted against the centrifugal force. The values of drain constant obtained by this method agreed with those calculated from the data based on the Haines apparatus in a gravitational field. It is suggested that this method can be applied to measure the drain height of fine particles less than 50μm diameter with a small amount of sample and in a few hours.

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With the development of new functional materials widely applied in electronics and other fields, slicing dust generated in wafer making process has recently increased. The dust consists of small amounts of these materials and large amounts of abrasives such as green carborundum. In order to reuse it as refining raw materials, it is necessary to separate these materials from abrasives.
The separation of gadolinium gallium garnet (GGG) from green carborundum (GC) has been investigated with flotation method. GGG can be selectively floated from GC by using dodecylammonium acetate as a collector, surfuric acid or phosphoric acid as an activator for GGG and starch as a depressor for GC. Corn starch solubilized in alkali solution is more selective depressor for GC than soluble starch. The use of surfuric acid is superior to that of phosphoric acid from economical and environmental points of view. It is suggested that the activation for GGG with surfuric acid is caused by the specific adsorption of sulfate ion and by the chemical interaction between sulfate ion and dodecylammonium ion on GGG surface.

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Extraction of vanadium from boiler slag derived from oil fired power plant was carried out by water leaching of heated sample under addition of sodium hydroxide. Salting out and crystallization of vanadate salt from leaching liauor was done with the addition of ammonium chloride and ethanol.
In the water leaching using the addition of sodium hydroxide and heating, vanadium was effectively extracted from boiler slag. For instance, the extraction ratio of vanadium was 99.9 percent when the sample heated for 120 min at 120°C with 6 ml/g-slag of 50% NaOH solution was leached by water for 60 min at 25°C.
In the salting out of vanadium with addition of ammonium chloride to the leaching liquor, the deposit obtained at pH 8.36 was identified as ammonium metavanadate, NH₄VO₃. On the other hand, in the case of addition of ethanol, the deposit was crystalized as sodium vanadate, NaV₃O.2H₂O.

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The extraction of Indium (III) from sulfuric acid solutions by di-2-ethylhexyl di-thiophosphoric acid (DEHDTPA, SH) diluted in kerosene was investigated under various aqueous conditions. The distribution ratio decreases monotonically with increasing aqueous acidities. In addition, the extraction with increasing of indium concentration was studied under definite sulfuric acid concentration. It was found that indium is extracted as a 1: 3=metal: reagent complex.
Infrared and high resolution nuclear magnetic resonance spectra were also studied for the extracted organic phase in order to elucidate the extraction mechanism. As the results, the following equation is given for the extraction of Indium (III) by DEHDTPA In³⁺ _(a) +3 (SH) _(o) ⇔InS_{3 (o)} +3H _(a) where S is the anion (C₈H₁₇O) ₂ PS₂^-.
Furthermore, extraction of zinc (II), cadmium (II), iron (III) and gallium (III) by DEHDTPA were carried out under various sulfuric acid concentrations. The separation factors can be accurately estmated on the basis of distribution ratios. It is apparent from the separation factors that separations of indium from zinc, iron and gallium are feasible, but that from cadmium is difficult.

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A study of extraction of metals from deep-sea manganese nodules was made by the sulfating roasting with SO₂ gas in a temperature range from 100 to 1, 000°C followed by the water leaching. The effects of roasting conditions on the extraction percentages of Ni, Co, Cu, Mn and Fe by the water leaching were investigated. The selective extraction of Ni, Co and Cu from the roasted ore was also attempted by the ammonia leaching. The results obtained are summarized as follows.
The highest degree of sulfation of manganese nodules was effected using a SO₂: O₂=2: 1 gas mixture at 400°C. The extraction percentages of Mn, Co, Ni, Cu and Fe by the water leaching of the roasted ore were about 90%, 90%, 70%, 70% and 0%, respectively.
When the roasted ore was leached in an ammoniacal solution, selective extraction of Ni, Co and Cu was greater using higher concentrations of ammonium ion. Under optimum conditions of ammonia leaching, the extraction percentages of Ni, Co, Cu, Mn and Fe were about 70%, 70%, 70%, 5% and 5%, respectively.

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