Lens effect of acoustic waves in a two-dimensional (2D) phononic crystal is studied by numerical simulation based on the finite-difference time-domain (FDTD) method. We calculate the phonon band structure of 2D phononic crystals, consisting of metal cylinders placed periodically in water. Lens effect is observed for far-field wave in the phononic crystal with graded-index structure. These results indicate that a novel energy-transmission device can be designed using phononic crystals.

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In the one-dimensional metal photonic crystal made by stacking metal plates, it has been theoretically predicted that an incident light is amplified and that higher harmonics are generated by the interaction between light and the lattice vibration when the metal plates are artificially vibrated harmonically. When the vibration frequency of the lattice is rather large, the incident light can be amplified by just shaking the whole photonic crystal. In the present study, the lattice vibration frequency dependence of the transmission probability of the light with the same frequency as that of the incident wave is investigated in the case of shaking a whole photonic crystal, and a series of many resonance peaks of amplification is found out. It is shown that by comparing with photonic bands of higher harmonics, the amplification of light originates in resonance between the incident light and higher harmonics and that the resonant peaks are located on the band or band end of higher harmonics.

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[in Japanese]

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Heating of circular silicon wafer plate under laser annealing is modeled by Non-Linear FEM. Laser source is modeled by concave shaped plate with focus immediately beneath the wafer surface. Heat source is placed over the wafer surface with fixed temperature, and sinusoidal motion. The radiosity is calculated from the geometry around the heat source and the silicon wafer. The chronological change of temperature profile is reported under this situation.

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[in Japanese]

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[in Japanese]

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Direct silicon bonded (DSB) substrates with (110)/(100) hybrid orientation technology are attracting considerable attention as a promising technology for high performance bulk CMOS technology. We have investigated the structure of the (110)/(100) interface parallelling each <110> direction (DSB interface) by first-principles calculation. The our calculation showed that (i) Si atoms in the DSB interface formed covalent bonding, (ii) the dangling bonds in Si (110) and (100) surfaces disappeared due to restructuring in the DSB interface. Moreover, the calculated interfacial structure corresponds to the reported TEM observation.

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A graphite nanotube is composed of Gemini type hexabenzocoronene (Gemini-HBC) as the hole-transport layer and the fullerene as the electron-transport layer. We study the doping effect on the electronic properties of Gemini-HBC to make the absorption peak broader, expecting to cover an unharvested energy resource. Here we assume that structure of doped Gemini-HBC is well represented by substituting dopant atom to one of carbon sites. Calculations of the energy and absorption spectrum are performed by the ab-initio computational method. As a result, the absorption peak of the Gemini-HBC is about 0.5μm, whereas the first and second peaks for doped Gemini-HBC are also approximately 0.5μm. In addition, the absorption spectrum of F-doped Gemini-HBC has an additional peak around 0.95μm, implying the sunlight with the longer wavelength may be absorbed.

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Vacancy interaction in Si crystal is studied by molecular-dynamics simulations. Using tight-binding molecular dynamics and classical molecular dynamics methods, we calculate an effective interaction potential of Si vacancy pair in bulk and in a thin slab at several temperatures. In the case of vacancy pair in bulk crystal, results reveal that there is an effective "capture radius" of the vacancies at around 8 Åat 300K and 13 Å at 600K and 1000K. Stable structure and electronic states around the vacancies in Si slab near the surface are qualitatively different from their bulk properties, reflecting a proximity surface electronic state. Results of diffusion behavior and interaction potential of the vacancy pair in the slab at finite temperatures are also reported.

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Lithium ion battery (LiB) is widely used in portable electronic devices, such as cellular phones and laptop computers. Recently, needs for higher efficiency of the battery has been increasing rapidly due to the demand for electric and hybrid electric vehicle. At present, anode of LiB is mainly made of graphite. Recently, graphene has been attracting more attention as an alternative anode material. The effect of impurity doping to graphene has also been investigated recently. To optimize the materials combination for the anode applications microscopic mechanisms of such enhancement of electric capacity in LiB have to be identified. Using an ab-initio computational method, based on the density-functional theory, and its hybridized method with the classical molecular dynamics, we investigate dynamical behavior, such as diffusion processes, of Li atom in the carbon based materials with pristine, defected, and doped graphene.

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As a preliminary step for understanding the cloud micro physics, an efficient direct numerical simulation code for tracking a large number of small inertial particles which are convected by isotropic turbulence has been developed. Three dimensional FFT for the spectral method is constructed by using two dimensional domain decomposition and MPI, and the effective domain decomposition is explored. Under the action of the gravity and turbulence the equations of motion of a large number of particles are integrated and their spatial distribution is studied by changing the Stokes numbers.

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Effects of line polymers on the Taylor Couette flow are studied by using direct numerical simulation with MPI. A line polymer is modeled as a dumb-bell which undergoes the Brownian motion due to the thermal fluctuation and deformation by the fluid motion. The stress due to the polymers modifies the fluid motion, and it is found that the torque acting on the wall is reduced.

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We examined the effects of the polymer additives on statistically steady and homogeneous turbulence by direct numerical simulations (DNS) of turbulence coupled with the Brownian dynamics (BD) simulations of the enormous number of FENE-dumbbells. We observed a reduction of the energy dissipation rate and a decrease of the acceleration variance of fluid particle by the effects of polymer additives. We found that these were consistent with the results of recent experimental and numerical studies. The efficiency of the large-scale parallel computations was also examined.

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We have performed atomic force microscopy (AFM) simulation to clarify the microscopic mechanism of the AFM using a coupling model of atomic and continuum model. Dynamics of the cantilever is described by the continuum model and the atomistic interaction between the probe and surface is calculated by the Molecular Dynamics (MD) method. In order to couple the two different systems, we use MD/continuum hybrid method developed by our group. In this paper, we propose a simple model for AFM, where the probe and surface are consisted of Lennard-Jones atoms and cantilever is one-dimensional spring. We show frequency shift of the cantilever and the energy transfer from the cantilever to the atom on the surface.

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[in Japanese]

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[in Japanese]

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A numerical model that considers the influence of the uniform magnetic field on the membrane of the red blood cell (RBC) is described in this study. The spring-network model which discritizes the RBC membranes into springs and mass elements was employed. The magnetic effect of the phospholipid and the transmembrane protein which composes the RBC membrane is then modeled by applying rotary torque on the edges of these elements. Further, the RBC computation was coupled with fluid computation using the Immersed Boundary method. The behavior of the RBC was compared with experimental results which showed a reasonable correspondence confirming the validity of the present model. Furthermore, the magnetic force distributions on the membrane showed that the curvature at the edge of the RBC influences the RBC rotation dominantly. The results also showed that the overall anisotropic diamagnetic susceptibility of the RBC can be predicted from the present model.

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In this study, numerical simulation of flow in downstream region of an orifice were carried out with three turbulence models, LES standard Smagorinsky model, LES dynamic Smagorinsky model, and DBS model. As a result, average velocity fields are qualitatively and quantitatively equivalent among all cases. Turbulent energy fields are qualitatively equivalent, but slightly lower in DBS model's case.

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Turbulent mass transfer, which is one of the key factors on the evaluation of flow accelerated corrosion (FAC), was considered using the analogy with the turbulent heat transfer. The mass transfer in the straight pipe is suggested to be proportional to the wall friction factor as well as the turbulence energy. We proposed the effective friction velocity taking the turbulent velocity near wall surface into account, which is used to evaluate the mass transfer at the turbulent region such as elbow and the downstream of orifice. STAR-CCM+ code with realizable k-ε two-layer model is used to evaluate the mass transfer at the turbulent region, in which wall function is not used and lattice points are taken in the viscous sublayer to evaluate mass transfer near wall surface of turbulent region. By introducing a concept of "Threshold Mass Transfer Coefficient", geometry factor correlations were evaluated for elbow, orifice, T-union and separation, quantitatively.

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[in Japanese]

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Flows around a droplet in an oscillating pressure field are simulated numerically using the Arbitrary Lagrangian-Eulerian and level set coupled method. It is found that the oscillating flow region appears in the thin layer on the droplet surface, where the phase of the oscillation is shifted from that in the outer region.

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Numerical solving of flow around the complex-shape body is of importance in various scientific fields. But there are problems in that it takes too much computational time for the interpolation scheme between the body and computational grid. In the present paper, we propose the novel numerical scheme by using Cartesian grid with immersed boundary(IB) method; to treat the complex shape easily and to speed up, the interpolation scheme is improved using the material points constructing the body. By using the proposed scheme, the unsteady flow around a rotating electric fan located inside a duct is simulated. From the visualized instantaneous flow field, it is found that three-dimensional structures are formed behind the rotating fan.

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The flow around a rotating disk in a cylindrical casing is investigated by the numerical and experimental methods. The radius of the disk is shorter than the inner radius of the casing, as well as the thickness of the disk is smaller than the length of the casing. Therefore, the flow field has a radial gap in addition to a narrow axial gap. The rotation of the disk in a cylindrical casing generates the flow with bead-like and sickle-like vortex, and spiral rolls is confirmed by the numerical calculation between the disk and the stationary walls. We investigated by visualization the generation and the transition process of such a flow that depended on the Reynolds number. As a result, the critical Reynolds numbers at which the flow transition appears is examined.

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We performed numerical computations of Taylor vortex flow at small aspect ratio. When the flow developed from its initial state at rest, non-unique flow patterns appeared. This depended on the lengths of the cylinder and the final Reynolds number. In experiment, it is difficult to keep constant conditions because of the imperfection of the apparatus and the small disturbances of the flow field. Therefore, the experimental result may show variations inherit from imperfections. In this study, we focused our attention on the small fluctuations of flows. Two-dimensional numerical analysis is used to estimate the effect on the final modes of Taylor vortex flow. Statistical analysis of the results presents a favorable agreement with our prescribed experimental result.

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A numerical study is performed on the swirling flows driven by the rotating top disk in a cylindrical container. The top disk is heated and the bottom disk is cooled, while the sidewall is assumed as adiabatic, and the Boussinesq approximation is adopted. The flows are studied for wide ranges of the governing parameters, the Reynolds number, the cylinder aspect ratio, the stratification parameter, and the Prandtl number. The occurrence of the vortex breakdown is studied and the results are plotted in a form of flow patter diagrams.

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[in Japanese]

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We investigated splash produced by spherical object plunging to water surface. We focused on the effect of swelling of object which was made of hydro gel. We compared the splash versus of swelling of the object. The splash form we observed was crown-type that is formed by water jets with many droplets. The height of splash became higher as swelling increased, and the speed of the object sinking in the water also became higher. The velocity around the object increased according to swelling. The gel surface of object was effective for the reduction of friction of an object moving in liquid.

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Human has been developing technology with the help of animals and natural phenomena. However, there are major differences between nature and artifact comparing flying birds and swimming fishes with planes and ships. There are many things to acquire from animals and natures. The hydrodynamics of swimming fish have been studied, but there are still a lot of unclear points in swimming fish. In this paper, relation between thrust and swimming fish is researched by computing fluid dynamic.

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