Adhesion and coaggregation phenomena of acetate-utilizing methanogens in the methane fermentation process were examined. The surface characteristics of three acidogens enriched from the anaerobic sludge and the pure cultures of Methanosarcina barkeri and Methanosaeta concilli were estimated. As a result, the selective adhesion phenomena of acetate-utilizing methanogen onto the bamboo charcoal could be explained by the electrostatic interaction and the change of free energy of interaction between microbes and support materials. The non-washed proteolytic bacteria and Methanosarcina barkeri were found to coaggregate rapidly even though the change of free energy of interaction was positive. It is guessed that these two microbes coaggregate with biological interaction because proteolytic bacteria produce hydrogen which is the substrate of Methanosarcina barkeri. The proteolytic bacteria enriched in this study can be expected to be used as bioflocculant that rapidly forms the granule of acetate-utilizing methanogens.

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Nano composite particles of polyimide and carbon nano-tube (CNT) were obtained by processing mixtures of polyimide / CNT particles in a planetary ball mill. Two kinds of composite particles were obtained by changing the operating conditions. One was a uniform composite particle of polyimide and CNT, while the other was a composite particle in which surface of the polyimide particle was covered by CNT. When the content of CNT was high, volume resistivity of molding plates made by the former composite particles were proportional to the content of CNT. However, when the content of CNT was low, the molded plate that used the latter composite particle indicated a small volume resistivity. It was because the CNT that coated the particle surface formed continuous layers in the molding plate after compressing molding the compound particle.

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In this study, compression test was applied to evaluate rheological characteristics of wet powder. Various quantities of moistened lactose monohydrate and microcrystalline cellulose were compressed in a cylinder. Relationships between compression transmission rate p_T / P and dimensionless sample height H / D under various compression pressures P were fitted to a theoretical pressure transmission equation of p_T / P ＝exp (-4μKH / D）. As a result, high correlations were obtained between them, indicating that pressure transmission of wet powder behaved as the ideal condition. The stress applied to the cylinder inner wall during the compression test was measured using strain gauges attached to the cylinder wall and friction coefficient of the wall surface μ and Rankine coefficient K were calculated. Consequently, the behaviors of μ and K under various compression pressures, liquid contents and liquid viscosities were investigated. From these results, it was suggested that the method proposed in this study could estimate a state of the wet powder under pressure.

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We have made a Lagrangian sensor for real-time and non-invasive measurement of fluid force acting on a particle which moves freely in liquid. The sensor particle contains an acceleration sensor, magnetometer, microcomputer, wireless signal transmitter module and cells. The acceleration sensor detects the acceleration of particle （acting force divided by mass） for each instant of time. The magnetometer detects the direction of external magnetic field, which is oriented in the same direction as the gravity, for the removal of gravitational acceleration from acceleration signals with arbitrary attitude of particle. We have performed some preliminary experiments in order to check the accuracy of the measurement system. The measured results agree well with the theoretical prediction of particle motion in liquid. Moreover, we applied the Lagrangian sensor to a multi-particle system for the measurement of fluid force under the influence of other particles.

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Fine particles have a large specific surface area. Because of this, the particle-particle interaction force becomes larger than the gravity force. This force balance causes a high adhesion and a difficulty of its handling. One of techniques to improve the adhesive behavior is an admixture of nano-particle. However, the mechanism of this phenomenon has not been well understood. This paper introduces effects of diameter and surface coverage ratio of admixed nano-particles on particle-bed packing property in uni-axial compression test.

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