The effect of particle clustering on char combustion was investigated using three dimensional direct numerical simulation. Gas flow was computed with a second-order finite volume method and particles were tracked with the Lagrangian manner. The Field model was employed as a char combustion model. Taylor-microscale based Reynolds number in the flow field was about 46 and the gas temperature ranged from 1273 to 1873K. To compute flow field with and without particle clustering, Stokes number values were set to 1.1×10^-6 and 1.9 The heat of char combustion was ignored in order to maintain a constant temperature in the flow field. The numerical results show that particle clustering affects oxygen concentration distribution, and consequently the conversion behavior of coal particles. The higher the gas phase temperature, the more pronounced this effect becomes, leading to suppression of coal particle conversion by up to 10％. These results indicate the need for a new char combustion model, which takes into account the particle clustering effect.

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We report a scalable production process of mesoporous calcium carbonate with calcite and/or vaterite phase. Here the effect of fatty acids （butanoic acid, octanoic acid, and decanoic acid） addition on the particle properties such as particle shape, crystal phase, and specific surface area was investigated. In our process, two types of mesoporous particles with difference in the particle shape and crystal phase were mainly obtained. It was found that the fatty acid controlled the self-assembly pathway of colloidal calcium carbonate. The particle shape and crystal phase depended on the additive amount of fatty acid. When the fatty acid was added in small amount to the colloidal dispersion, crystal phase of mesoporous calcium carbonate was calcite. While, adequate or excess addition of the fatty acids was favorable to form vaterite phase. We have proposed the possible mechanism for formation of mesoporous calcium carbonate.

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Fabrication of microdevices has recently been a hot and challenging topic. Microrobots and microfluidics, which are typical examples of microdevices, require nano/microsized motors or pumps as their power source. Unlike currently available macro motors, the motion of nano/micromotors cannot be maintained by its inertia due to the larger viscous effect in a smaller system. Therefore, we must develop a micromotor and micropump working on a new principle.
In the present study, we propose a simple motile system wherein microparticles move continuously under a DC electric field. The motion involves two steps : chain-like arrangement of the particles on a negative electrode and subsequent periodic motion （i.e., spin and rotation） of the other particles in the vicinity of the chain-like ones. Characteristics of the motion depend on an electric field and particles morphology. Chemical nature of particles also affects their motion characteristics. These controllable motions are expected to be applicable for a micromotor and micropump.

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Agglomerated particle behavior in a pan-type pelletizer was simulated by Discrete Element Method （DEM） with/without considering adhesive force of liquid bridge, to know the effect on the velocity and trajectory of variously-sized particle in a pan by adhesive force. We selected the liquid bridge model proposed by Israelachvili, because it was quantitatively coincident with experimentally measured force by Willett in wide range of interparticle distance.
Velocity and trajectory of several size of particles were compared with experimental results obtained from image processing using high speed camera and their results were consistent each other only when adhesive force by liquid bridge was considered into the simulation. Especially in the experiment, large particles stuck to the pan around the bottom, raised along the rotation of the pan, and presented a maximum velocity at a fixed height by slide down. These trends could be represented in the simulation only when the liquid bridge force was considered.

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We analyzed the effect of a rotor-stator mixer's head geometry and rotor-stator clearance （0.5 to 2 mm） on the efficiency of dispersing coarse alumina aggregates （with a primary particle size of approximately 10 nm） in suspension. We examined the effects on the dispersion efficiency and focused on the shear rate near the surfaces of the rotor-stator, and performed a computational fluid dynamics （CFD） analysis using a turbulence model with a low Reynolds number. The measured dispersion values showed that the efficiency with which the aggregates were distributed changed with the mixing head geometry, but was not affected by the clearance. The results of the CFD simulation showed that the effect of the mixing head geometry and the clearance on the dispersion efficiency is related to the volume of those regions where the shear rate is high. These high shear rate regions were restricted to within approximately 50μm from the surfaces of the rotor and stator.

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Three-dimensional direct numerical simulation is performed in a particle-laden turbulent mixing layer to investigate the effects of a parcel modeling on the characteristics of particle dispersion, scalar diffusion and velocity fluctuation. The effects of the parcel model are carefully investigated and discussed in comparison with the case in which the parcel model is not used as a reference, RC, in terms of the number of particles represented by a parcel, N_p, and Stokes number defined by the particle relaxation time and Kolmogorov time scale, St. Results show that the parcel model can capture almost behavior of particle dispersion while the discrepancy between the model and RC becomes larger with increasing N_p. The evaporation rate is suppressed by employing the parcel model, because the vapor pressure in a cell is rapidly saturated by the parcel which represents a number of particles and subsequently the mass transfer number is underestimated. The trend of turbulence modulation is qualitatively captured by the cases employing the parcel model with the small N_p while the case with the larger N_p and St cannot capture the trend. It is therefore essential that N_p and St are carefully determined to avoid capturing the nonphysical behavior in a numerical simulation with the parcel model.

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We have fabricated nanocomposite ceramics of Bi_0.5Sb_1.5Te₃/PTFE （Poly-Tetra-Fluoro-Ethylene） to improve the mechanical properties of the state-of-the-art thermoelectric Bi_0.5Sb_1.5Te₃. The Bi_0.5Sb_1.5Te₃/PTFE ceramics were prepared by sintering mixed powders of micrometer size Bi_0.5Sb_1.5Te₃ and nanometer size PTFE. While the addition of excess amount of PTFE particles to the Bi_0.5Sb_1.5Te₃ matrix lead to deterioration of the thermoelectric performance by significant increase in electrical resistivity over the decrease in thermal conductivity, we found that addition of small amount （around 0.5 mass％） can lead to improvement of the mechanical strength up to 22％ of the original value without deteriorating the thermoelectric performance. Microstructural analysis revealed the presence of a void structure around the PTFE particles. We assume that the plasticity of PTFE is responsible for the improvement of the mechanical strength while both PTFE and the voids are responsible for the reduction in thermal conductivity.

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BaTiO₃ nanoparticles were synthesized by hydrothermal reaction in supercritical water using a continuous flow reactor. The reactant solution of 0.05 M TiO₂ sol and 0.06 M Ba（OH）₂ was prepared as starting materials. They were mixed with supercritical water at 400℃ under the pressure of 30 MPa and were kept for 0.1 s, 0.5 s or 2 s. The X-ray diffraction （XRD） results indicated that the crystalline phase of the obtained particles was only BaTiO₃. The diameter of BaTiO₃ nanoparticles measured on the transmission electron microscopy （TEM） images was about 30 nm regardless of reaction time. But on the surface of BaTiO₃ particle, oxygen defects were observed by high resolution TEM （HRTEM） and TEM-electron energy loss spectroscopy （TEM-EELS）.

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