This work investigates the electromechanical response of poled barium titanate (BaTiO_3) polycrystals with oxygen vacancies at room temperature. A phase field model is developed for ferroelectric polycrystals, coupled with the time-dependent Ginzburg-Landau theory and the oxygen vacancies diffusion, to demonstrate the interaction between oxygen vacancies and domain evolutions. To generate grain structures, the phase field model for grain growth is also employed. The strain vs stress curve and strain vs electric field curve are computed, and the effects of grain size and oxygen vacancy density on the elastic and piezoelectric properties of the BaTiO_3 polycrystals are discussed.

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In this study, the extended model with two scaling exponents is developed to reproduce the effects of swelling on the Young's modulus and the osmotic pressure of swollen elastomers. Two scaling exponents, m and n, are introduced into strain energy functions separated into deviatoric and volumetric parts, respectively. The two different swelling effects are predicted well by independently adjusting two scaling exponents; m takes a wide range of values depending on elastomers, while n is almost independent of elastomers and takes a negative value. It is found that under uniaxial loading subsequent free swelling, the extended model is able to predict strain softening, which is thus related with strain localization followed by swelling-induced rupture. Experiments show that swelling-induced rupture occurs when small extension is applied with good solvents. This tendency is successfully predicted with an appropriate set of the material parameters including two scaling exponents.

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[in Japanese]

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We investigate the statistical properties of the desiccation crack pattern. From the analysis of the numerical simulation of a continuum model, it is found that the fragment size distribution obeys a dynamic scaling law that the distribution can be collapsed into a time-invariant curve by scaling with the mean of fragment size. In order to explain the scaling law, a stochastic model in which a size-dependent lifetime of fragment is introduced into Gibrat process is proposed. According to the scaling analysis of the stochastic model, the scaling law can be explained theoretically. Furthermore, a experiment of desiccation cracking of a paste composed of water and powder of magnesium carbonate hydroxide is carried out in order to confirm the scaling law. As a result, it is found that the experiment shows the scaling law and agrees with our theoretical results well.

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[in Japanese]

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The stock price prediction using Bayesian network has been presented by some researches. Their results showed that the prediction algorithm using Bayesian network has good prediction accuracy, This paper presents the improved algorithm in which the prediction accuracy of Nikkei stock average is enhanced by using NASDAQ index data. The accuracy of the present algorithm is compared with the precious algorithms in order to confirm the validity.

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Vehicle following model is very effective for increasing the traffic capacity and enhancing the traffic safety. This paper describes the vehicle velocity control model of the four-vehicles when two vehicles merge into the platoon of other vehicles. Traffic flow simulation of four LEGO Mindstorms is performed. The experimental result is compared with the simulation result in order to confirm the validity of the model.

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[in Japanese]

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This paper presents a direct numerical simulation of a flexible filament in a flowing soap film and a small-scale von Karman vortex street trailing behind the filament. The numerical method is an interface-tracking ALE finite element method with an implicit and monolithic time integration scheme. The numerical results are discussed in terms of fluid dynamics and the benchmark of the computational method

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This paper proposes a level set based topology optimization method for steady state incompressible viscous flow problem. The optimization problem is formulated to minimize the total pressure loss and maximize angular momentum under a volume constraint. The optimization algorithm is developed based on this formulation. In addition the adjoint variable method is applied for the sensitivity analysis. The level set function updating scheme uses a reaction-diffusion equation. Several examples are shown to confirm the method.

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[in Japanese]

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Unusual emergence of magnetization induced by vacancy-strain interaction in non-magnetic ferroelectric PbTiO_3 is investigated using first-principle calculations. Atomic-scale ferromagnetism is observed at an oxygen vacancy under tensile strain, while under compressive strain it exhibits anti-ferromagnetism. These emerged magnetic properties are characterized by the split of defect electronic states via strain. We also reveal that the magnetic properties are changed by the polarization switching, that is, applied strain oxygen vacancies in PbTiO_3 exhibit atomic-scale multiferroicity and magnetoelectric effect.

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A new meshfree numerical analysis, termed the seamless domain method (SDM), is applied in a multiscale technology. The SDM requires only a small number of points and does not require a stiffness equation, mesh, grid, cell, or element. The SDM consists of two analyses. The first is a microscopic analysis of local simulated domain to obtain shape functions for interpolation of dependent-variable distributions and influence coefficients for calculation of interaction between the points. These allow an SDM solution to represent a heterogeneous material without homogenization. The second step is a macroscopic analysis of a seamless global domain without mesh or grid. Various numerical examples illustrated that the method worked out both steady temperature fields and linear elastic fields. All the SDM solutions using only a few hundreds of points were as accurate as those from traditional finite-element analysis using more than two hundred thousands of nodes.

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[in Japanese]

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As a way to reduce the huge computational cost of unsteady calculation in computational fluid dynamics, it has been proposed approximate solution using the non-linear harmonic method. In this method, the unsteady flow field is calculated by decomposing to time average term and time variation term, and flow field is reconstructed from the results of each terms. A method of reconstructing the unsteady flow field from the result,If you have applied to a turbo machinery, non-steady-state calculation is one wing only minutes with no need Since it is sufficient in modeling is possible savings significant computation time and memory.In this time, we introduce a variety of case studies in turbomachinery.

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