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Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level.

The numerical simulation of flow-induced structures is important for the flow analysis of complex fluids. Several schemes have been proposed for coupling the macro-flow computation and the microsimulation of the inner structure of complex fluids. In the present study, the flow-induced structure of star polymers was numerically simulated using a coupling method of multi-particle collision dynamics (MPCD) and coarse-grained molecular dynamics (MD). The polymers were modeled as elastic dumbbells, which consist of finitely extensible nonlinear elastic springs and beads. The motion of the beads was computed by MD. The MPCD was applied to model the effect of Brownian motion and hydrodynamic interactions among the beads. In the present study, the MPC-AT+a algorithm was employed for the collision steps in MPCD computations. The behavior of linear polymers in a shear flow was numerically analyzed to confirm the validity of the present simulation scheme. The numerical results agree well with both experimental results and predictions by other numerical methods. Furthermore, the simulation of star polymers under shear flow was carried out. The present simulation captured characteristic behaviors such as the configuration of the star polymers, which was more compact for polymers with more arms due to extruded volume effects, polymers tumbling at high Weissenberg numbers, and the fluctuation in expansions in the direction of flow decreasing for polymers with more arms.

The NTCIR INTENT task comprises two subtasks: Subtopic Mining, where systems are required to return a ranked list of subtopic strings for each given query; and Document Ranking, where systems are required to return a diversified web search result for each given query. This paper summarises the novel features of the Second INTENT task at NTCIR-10 and its main findings, and poses some questions for future diversified search evaluation.

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