To investigate geometrical parameters such as surface area and volume of particulates and shape parameters as elongation, flatness and so on, salient silhouettes of a sample of pebbles were analyzed three-dimensionally with the discrete Fourier transformation rotationg about a single axis. From the results, the surface area and the volume were well correlated with a set of the sine coefficients. The Characteristic forms of pebbless were allocated in a three-dimensional space where the Fourier coefficients (parameters) were combined.

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Nitrogen adsorption isotherms at 77K on non-porous powders, such as γ-Fe₂O₃, A1100 and SM and silicon carbide, SiC(P) have been measured. The application of experimental isotherms to the 3-parametric adsorption equation was compared with that of the BET equation. The applicable relative pressure range of the 3-parametric adsorption equation was compared with that of the BET equation. The applicable relative pressure range of the 3-parametric adsorption equation was wider, from 0.05 to 0.65, than that of the BET equation which was in the range from 0.05 to 0.35. The surface areas, ∑^T obtained from the 3-parametric adsorption equation showed an agreement within 10% with that from the BET equation, ∑^B. Since the straight line in α_s-plots of N₂ adsorption isotherms were found to pass through the origin of the coordinate, the powders were confirmed to have no micropore. The outer plane surface areas, ∑^T_αs and ∑^B_αs, were determined from the slope of the straight line in α_s-plots of the standard isotherm of N₂ on non-porous hydroxylated silica, on the basis of the surface areas by application of the standard isotherm to the 3-parametric adsorption equation and BET equation, respectively. There is a reasonable agreement of ∑^T and ∑^B with ∑^T_αs, and ∑^B_αs, respectively, and therefore it will be difficult to determine which surface areas were the most reasonable. However, the surface areas obtained from the measurement of the particle diameter in use of a photograph of a scanning electron microscope showed better and reasonable agreement with the surface areas from the 3-parametric adsorption equation than that from BET equation. Therefore, the 3-parametric adsorption equation seemed to be more reasonable than the BET equation.

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A method is described for the design of a prism-shaped insert which is equipped in a rectangular converging hopper over its outlet in order to prevent the formation of a static stable arch in a cohesive powder. The critical span of the static arch is estimated from Jenike's procedure that is modified on the basis of static stresses developed during the initial fill of the hopper, using with results of a fixed volume direct shear test.
Safety factors are considered in regard to the size of the hopper outlet and the span of the wedge-type channel constructed around the prism-shaped insert. When the values of the safety factors are given, the optimum dimensions of the prism-shaped insert are determined.
A prism-shaped insert of 700mm in width and 2180mm in length is designed in order to initiate the discharge of wet coals from existing rectangular bunkers with a capacity of 640m³ and a hopper outlet of 615mm in diameter. It did so with complete success.

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This study is undertaken to investigate the interaction which appears at the interface between a solid particle and its surrounding medium during crushing. The crushing experiments are carried out on alumina powder surrounded by air and liquids. The products taken from the crushing machine are dispersed in the liquid to prepare samples which can be used for the measurements of R (electric resistance) and pH in the dispersed system.
From measured data of R and pH, good knowledge about the interaction was obtained. The results were found to be as follows:
(1) In the dry crushing process, the electric resistance, R, of a dispersed system tends to decrease because of the concentration of the dissociation ions, OH^-tends to increase.
(2) The electic resistance, R the wet crushing process of a dispersed system tends to increase because of the concentration of the adsorped ions on the fresh surface shows an increasing tendency.
(3) The electric resistance of a dispersed system of crushed powders closely related to the disociation and adsorption of ions in the interface between particle and medium.

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