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Minamoto S.,ITOCHU Techno Solutions Corporation | Kato M.,Japan Atomic Energy Agency | Konashi K.,Tohoku University
Journal of Nuclear Materials | Year: 2011

Combination of an oxygen vacancy formation energy calculated using first-principles approach and the configurational entropy change treated within the framework of statistical mechanics gives an expression of the Gibbs free energy at large deviation from stoichiometry of plutonium oxide PuO2. An oxygen vacancy formation energy 4.20 eV derived from our previously first-principles calculation was used to evaluate the Gibbs free energy change due to oxygen vacancies in the crystal. The oxygen partial pressures then can be evaluated from the change of the free energy with two fitting parameters (a vacancy-vacancy interaction energy and vibration entropy change due to induced vacancies). Derived thermodynamic expression for the free energy based on the SGTE thermodynamic data for the stoichiometric PuO2 and the Pu 2O3 compounds was further incorporated into the CALPHAD modeling, then phase equilibrium between the stoichiometric Pu2O 3 and non-stoichiometric PuO2-x were reproduced. © 2011 Elsevier B.V. All rights reserved. Source

Koike A.,Isuzu Advanced Engineering Center | Yokoyama A.,Kyoto Institute of Technology | Akita R.,ITOCHU Techno Solutions Corporation
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2016

Fiber Reinforced Plastics (FRP) has been applied in the aerospace field. In recent years, the application to the automobile field has been considering. In order to apply a FRP to the automobile field, not only the strength, but the fracture has to be determined, due to crash of a car. Authors have been working for the FRP to use of an energy absorbing device. In this paper, fracture mechanism analysis of the FRP tube at initial stage had been done with the consideration of continuous random fibers. Especially the initial micro-fracture of the trigger part of FRP tube was observed, and the transition process of initial micro-fracture to a continuous and stable fracture which is called 'progressive crushing mode' was analyzed. Source

Abe Y.,ITOCHU Techno Solutions Corporation | Kato N.,University of Tokyo
Nonlinear Processes in Geophysics | Year: 2014

We herein report the results of some numerical simulations of complex earthquake cycles using a three-degree-of-freedom spring-block model with a rate-and state-dependent friction law. The model consists of three blocks on a conveyor belt that is moving at a steady rate. Observed complex slip behaviour in the simulations is classified into five slip patterns, and for each of these the parameter dependence of the slip patterns is demonstrated by means of phase diagrams. Aperiodic slip patterns occur for wider ranges of the parameter space in the three-block system than in the two-block system. Chaotic slip behaviour known here as "intermittency" is found in the three-block system, in which two different slip patterns occur alternately with variable durations. By calculating Lyapunov exponents, we quantify the dependence of slip evolution on the initial conditions for each slip pattern. For cases where intermittent slip patterns occur, the time evolution of the Lyapunov exponent is correlated with changes in slip behaviour. © 2014 Author(s). Source

Abe Y.,ITOCHU Techno Solutions Corporation | Kato N.,University of Tokyo
Pure and Applied Geophysics | Year: 2013

Numerical simulations of complex earthquake cycles are conducted using a two-degree-of-freedom spring-block model with a rate- and state-friction law, which has been supported by laboratory experiments. The model consisted of two blocks coupled to each other and connected by elastic springs to a constant-velocity, moving driver. By widely and systematically varying the model parameters, various slip patterns were obtained, including the periodic recurrence of seismic and aseismic slip events, and several types of chaotic behaviour. The transition in the slip pattern from periodic to chaotic is examined using bifurcation diagrams. The model system exhibits typical period-doubling sequences for some parameter ranges, and attains chaotic motion. Simple relationships are found in iteration maps of the recurrence intervals of simulated earthquakes, suggesting that the simulated slip behaviour is deterministic chaos. Time evolutions of the cumulative slip distance in chaotic slip patterns are well approximated by a time-predictable model. In some cases, both seismic and aseismic slip events occur at a block, and aseismic slip events complicate the earthquake recurrence patterns. © 2012 The Author(s). Source

Fukumoto S.,Nippon Steel & Sumitomo Metal Corporation | Oikawa Y.,Nippon Steel & Sumitomo Metal Corporation | Tsuge S.,Nippon Steel & Sumitomo Metal Corporation | Nomoto S.,ITOCHU Techno Solutions Corporation
ISIJ International | Year: 2010

The formation of σ phase was investigated in Fe-Cr-Ni-Mo alloys with high nitrogen content. The amounts of the σ phase are correlated with the calculated δ-Fe values. The Md-PHACOMP (Phase Computation) method, which takes into consideration the effect of nitrogen and carbon content as well as microsegregation at the interdendritic region, can predict the σ precipitations. The numerical methodology for a multi-phase-field model can be also applied to σ phase formation by δ to (γ+σ) transformation. © 2010 ISIJ. Source

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