A critical slope of hopper walls for mass-flow of bulk solids was calculated from both the angle of internal friction and the angle of wall friction by Jenike's method and others. Jenike's method was based on the criteria of existing solutions for the equations of the radial stress field. The angle of internal friction of various bulk solids was in the range of 26 to 35 degrees while the angle of wall friction on various materials ranged from 11 to 29 degrees.
Calculated results of the critical slope compared favorably with the results of the flow pattern of bulk solids which were observed in conical and pyramidal hoppers with wall slope of 48 to 84 degrees. Consequently Jenike's method was useful for the hopper design.

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An electrokinetic method with ion exchange reactions was investigated for the remediation of heavy metal contaminated soils which have an extremely low hydraulic permeability. Various consolidated bentonite cakes contaminated with Zn, having different permeation properties, were prepared by a mechanical expression method, and the removal of Zn²⁺ from the cake was carried out by the electrokinetic method with the addition of Na⁺. Under the condition of a constant current density, an increase in Na⁺ concentration led to a higher rejection ratio of Zn²⁺. However, the permeation rate of the liquid through the cake was decreased with Na⁺ concentration. Therefore, it is important to select an appropriate concentration of Na⁺ for the effective removal of Zn²⁺ from the contaminated soil. Also, the rejection performance was little influenced by the permeability of the cake. Consequently, the electrokinetic method developed in this work was found to be useful for the remediation of contaminated soils with extremely low hydraulic permeability.

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The present work estimated the removal efficiency of a bag filter system for total dioxin and dioxin-like compounds including gaseous ones with an injection of adsorbents of activated carbon particles, by taking into account the distributions of gas flow rate and accumulated dust on the individual bag filters in a bag filter house. As a result, it was found that the bag filters with a low dust accumulation operated at a higher gas flow rate has a lower removal efficiency for gaseous dioxins, and we derived the relationships between the removal efficiency of dioxins and the operational and structural parameters of a bag filter system, such as, the filtration velocity, the dust-cleaning pressure, the number of bag filters, the configuration of bag filters, and the amount of injected activated carbons. The present model successfully predicted the on-site data measured for the bag filter systems.

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A method for estimating the particle diameter of submicron ceramic powder ground by a tumbling ball mill is proposed by using the Particle Element Method (PEM). The method employs both the experimental grinding test and the simulation results with the minimum grinding energy concept. When mill capacity is approximately 10 times that used for the experiments mimicking a pilot plant, the ground particle diameter estimated from the friction energy showed good correlation with the experimental results. The analysis based on the minimum grinding energy suggests that the principal factor in the grinding of submicron powder is the friction between the ball and the wall. This method is useful for estimating a particle diameter of ground submicron powder.

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Nanometer-scale coinage metal particles were coated with silica by a modified Stöber method. Silica shell thickness was varied from 30 to 90nm for Au core particles and from 28 to 76nm for Ag core particles. The optical spectra of the silica-coated Au and Ag nanoparticles agreed with predictions by Mie theory. For Cu nanoparticles, silica-coating was also successfully performed with the use of silane coupling agent as a stabilizer.

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