In this study, the elastic-viscoplastic properties of ultrafine plate-fin structures which possess uncertainty factors in material properties of a base material are investigated using the Monte Carlo simulation. For this, a time-dependent homogenization theory is applied to the analysis of the elastic-viscoplastic properties of ultrafine plate-fin structures. Moreover, the Monte Carlo simulation with the Stepwise Limited Sampling (SLS) is used to take into account uncertainty factors in material properties. Then, using the present analysis method, the effects of uncertainty factors of material properties on the elastic-viscoplastic behavior of ultrafine plate-fin structures under uniaxial tension at high temperature are investigated. From this analysis, we can obtain the macroscopic and microscopic tail probability values by one tenth of computational time compared to the conventional Monte Carlo simulation.

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In this study, macro/meso/micro inelastic analysis method for plain-woven laminates is developed based on a homogenization theory for nonlinear time-dependent composites. For this, a three-scale modeling of plain-woven laminates is performed by considering a plain-woven laminate as a macrostructure, fiber bundles (yarns) and a matrix in the laminate as a mesostructure, and fibers and a matrix in the yarns as a microstructure. Then, a macroscopic constitutive equation of the laminate is derived by dually applying the homogenization theory for nonlinear time-dependent composites to not only the meso/micro scale but also the macro/meso scale. Using the present analysis method, the elastic-viscoplastic analysis of a plain-woven glass fiber/epoxy laminate subjected to on and off-axis loading is performed. Moreover, the analysis results are compared with the experimental data. It is shown that the present analysis method successfully takes into account the effects of inelastic properties of the epoxy not only around the fiber bundles but also inside of the fiber bundles. It is also shown that the results of analysis are in good agreement with experimental data.

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We have investigated adsorption and subsequent dissociation of oxygen molecules on the NiO surface with and without vacancies by ab initio molecular dynamics simulation to understand the elementary process of the oxygen reduction reaction in the SOFC cathode. Oxygen molecules were adsorbed both on the surfaces with and without vacancy. However, dissociation was confirmed only on the surface with oxygen vacancy. It is because positive charge of the Ni atoms near the oxygen vacancy was smaller than that without vacancy and electron of adsorbed oxygen molecules is transferred toward the Ni atoms resulting in the decrease of the strength of O-O bond in the oxygen molecule.

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[in Japanese]

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[in Japanese]

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Long term durability of solid oxide fuel cell (SOFC) is one of the critical problems to be solved. Thermal stress has severe impact to SOFC electrolyte and electrode which is made from dense or porous ceramics. SOFC stack has much more risk to lead thermal crack by inhomogeneous temperature distribution due to the stack structure and its flow channel shape. Direct internal reforming also increases the risk of SOFC thermal destruction. Paper-structured porous catalyst putting in SOFC stack can control the gas flow and reforming reaction distribution at the cell inside. This paper-structured catalyst also have disadvantage to lead much pressure loss. However, gas diffusivity control and internal reforming rate have an effect to decrease the temperature drop and keep homogeneous temperature on SOFC anode.

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[in Japanese]

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