In this paper, the modification of the measurement method for the powder porosity generated in a powder, which was studied by the authors, is discussed. And the following conclusions were obtained.
1) The measurement method on the basis of equal X-ray penetrations of a reference cell for powder porosity and a test cell presented in the last paper, was fundamentally modified and a new method based on any combination of two X-ray penetrations, mentioned above, was presented.
2) The new method was checked experimentally by the use of an X-ray radiograph system and was shown to be effective as a method for the measurement of the porosity generated in a powder.
3) Any shape of the reference cell for the powder porosity can be applied to the method presented in this paper.

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Experiments were carried out on the discharge of wet coals from experimental bunkers with a capacity of about 4m³. These bunkers were reduced to a scale of one-sixth the actual size of those in a coal thermal power station. Consequently, the coal bunker must be completely designed as a type of mass flow.
An improved hopper was proposed in order to reduce the critical size of hopper outlet. The improved hopper was a regular pyramidal hopper joined to a conical hopper, and a prismatic insert was installed between each opposite wall of the pyramidal hopper.
A method is described for the estimation of the critical size of the bridge in the hoppers at the commencement of flow on the basis of the conditions of the static state of stresses exerted by the bulk solid. The estimated values of the critical outlet size, using the fixed volume shear cell results, were in good agreement with the experimental results of the discharge.
The experimental results also indicate that the slope angle of the hopper walls was reasonably determined from both the angle of internal friction and the angle of wall friction according to Jenike's approach. Moreover, remnants of coal that adhered to the bunker walls were strongly affected by the wall materials used, such as steel and ultra high molecular weight polyethylene.

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Oil droplets collection characteristics of an electro-floatation machine with a rotating electrodes-cum-impeller has been studied in the hope that the machine might be used for waste water treatment. Bubble size does not depend on the concentration of Na₂SO₄ (electrolyte). Bubbles become smaller with the increase in the rotational speed of the impeller. When bubbles are not generated, the emulsion remains stable without the rotation of impeller. The collection rate increases gradually as the rotational speed increases. When bubbles are generated by electrolysis, the collection rate rises considerably. The collection rate increases with a rise in current intensity, though the proportion of the collected droplets decreases under the same amount of electricity. The collection rate increases with increasing rotational speed, asymptotically approaching a fixed rate. The concentration of the coagulant exerts a great influence on the collection rate. When the concentration becomes larger than 5×10^-8mol/m³, the collection rate is independent of the concentration.

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