ITOCHU Techno Solutions Corporation

Tokyo, Japan

ITOCHU Techno Solutions Corporation

Tokyo, Japan
Time filter
Source Type

Kobayashi H.,ITOCHU Techno Solutions Corporation | Narushima Y.,Yokohama National University | Yabe H.,Tokyo University of Science
Optimization Methods and Software | Year: 2017

The conjugate gradient method is an effective method for large-scale unconstrained optimization problems. Recent research has proposed conjugate gradient methods based on secant conditions to establish fast convergence of the methods. However, these methods do not always generate a descent search direction. In contrast, Y. Narushima, H. Yabe, and J.A. Ford [A three-term conjugate gradient method with sufficient descent property for unconstrained optimization, SIAM J. Optim. 21 (2011), pp. 212–230] proposed a three-term conjugate gradient method which always satisfies the sufficient descent condition. This paper makes use of both ideas to propose descent three-term conjugate gradient methods based on particular secant conditions, and then shows their global convergence properties. Finally, numerical results are given. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Segawa M.,Tokyo University of Agriculture and Technology | Yamanaka A.,Tokyo University of Agriculture and Technology | Nomoto S.,ITOCHU Techno Solutions Corporation
Computational Materials Science | Year: 2017

The stagnant and inverse transformation stages during cyclic phase transformation in the two-phase region “ferrite + austenite” (intercritical region) of Fe-C-Mn and Fe-C-Mn-Si alloys were investigated using the non-equilibrium multi-phase-field (NEMPF) model, i.e. an MPF model with finite interface dissipation. We showed that if we used large interfacial permeability parameters that characterize the partitioning rate of solute atoms in the ferrite/austenite interface, the NEMPF model predicted the same transformation behavior as that simulated using the MPF model based on the assumption of the parallel tangent law. The simulation demonstrated that the inverse transformation stage, in which ferrite-to-austenite transformation proceeds despite decreasing temperature, could be naturally described by the NEMPF model coupled with the CALPHAD-based thermodynamic database. This study also elucidated a switching of the polarities of Mn and Si spike formed at the ferrite/austenite interface governed the driving force of the austenite-to-ferrite transformation and caused the stagnant stage where the phase transformation was suppressed. Furthermore, the impact of the amount of Mn and Si atoms on the stagnant stage length was examined using the NEMPF model. The simulations revealed that increasing the concentration of Mn and Si extended the stagnant stage, with a more pronounced effect with Mn rather than Si atoms. © 2017 Elsevier B.V.

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.

Tanimura S.,Osaka Prefecture University | Tanimura S.,Aichi University of Technology | Tsuda T.,ITOCHU Techno Solutions Corporation | Abe A.,ITOCHU Techno Solutions Corporation | And 2 more authors.
International Journal of Impact Engineering | Year: 2014

Applicability of constitutive models of Cowper-Symonds (CS), Modified Cowper-Symonds (Modified CS), Johnson-Cook (JC), Zerilli-Armstrong (ZA) and Tanimura-Mimura 2009 (TM2009) is discussed by comparing the properties of these models with experimental data. It is shown that the stress-strain curves at each strain rate, which are predicted by using the values of parameters published in the literature for the CS, MCS, JC and ZA models, can sometimes diverge from the experimental curves, not only for the large strain region near the true fracture strain, but also for the homogenous deformation region. It is only necessary to know the quasi-static stress-strain curve in advance for the TM 2009 model, because the set of parameters is given for each material group, and can be used for any material belonging to the group. Simple methods to estimate the quasi-static curve are discussed. © 2014 Elsevier Ltd. All rights reserved.

Nomura Y.,ITOCHU Techno Solutions Corporation | Minamoto S.,ITOCHU Techno Solutions Corporation | Nomoto S.,ITOCHU Techno Solutions Corporation
ISIJ International | Year: 2010

The microstructural evolutions in a Sn-3Ag-0.5Cu system of lead free alloys were predicted by the multiphase field simulation coupled with CALPHAD thermodynamic database. In this simulation, the growth of Cu6Sn 5 at 250°C and the precipitations of Cu3Sn and Ag 3Sn at 150°C were calculated. These calculated micrographs were in good agreement with the experimental measurements. It was confirmed that this calculation method can be applied to the simulation of microstructures in the solidification of lead-free solder system including a Cu-substrate. © 2010 ISIJ.

Miyakawa T.,Tokyo University of Science | Miyakawa T.,Japan Agency for Marine - Earth Science and Technology | Matsuzawa R.,ITOCHU Techno Solutions Corporation | Katayama M.,ITOCHU Techno Solutions Corporation | And 2 more authors.
Aerosol Science and Technology | Year: 2013

Adhesion and bounce of liquid and solid particles upon high-velocity impact with a surface has been investigated using semi-empirical and explicit hydrodynamic simulations. Ammonium nitrate (AN) and sodium chloride (NaCl) were selected as test compounds for the liquid and solid particles, respectively, and tungsten (W) as the target surface. Changes in the shape, temperature, strain, and rebound velocity of these particles upon high-velocity impact are investigated assuming operational conditions (particle diameter, and velocity) of Aerodyne aerosol mass spectrometer (AMS). The simulations show that the AN particles adhere to the W surface, which is consistent with previous experimental studies. In the case of NaCl, the collection efficiencies depend significantly on the stress-strain characteristics of the crystal. Our results suggest that, in addition to particle phase and impact velocity, anisotropy of the elastic properties and brittleness are key factors in controlling the adhesion and bounce of solid particles. © 2013 American Association for Aerosol Research.

Wada T.,Tokyo Metroplitan University | Ho Y.,Tokyo Metroplitan University | Okubo K.,Tokyo Metroplitan University | Tagawa N.,Tokyo Metroplitan University | Hirose Y.,ITOCHU Techno Solutions Corporation
Physics Procedia | Year: 2015

This study addresses the efficient extension of the Super resolution FM-Chirp correlation Method (SCM) to the framework of synthetic aperture imaging. The original SCM needs to transmit focused beams many times while changing frequency little by little toward each direction to extract the carrier phase information which is useful for super resolution imaging. This multiple transmitting and receiving increase the amount of processing and puts a strict limit on the frame rate. Therefore, we extend the SCM to the synthetic aperture version called the SA-SCM, and confirm its performance through simulations based on the finite element method. © 2015 The Authors.

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).

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).

Zhan T.,Japan National Institute of Materials Science | Minamoto S.,ITOCHU Techno Solutions Corporation | Xu Y.,Japan National Institute of Materials Science | Tanaka Y.,Japan National Institute of Materials Science | Kagawa Y.,Japan National Institute of Materials Science
AIP Advances | Year: 2015

In this study, we investigated the temperature dependence and size effect of the thermal boundary resistance at Si/Ge interfaces by non-equilibrium molecular dynamics (MD) simulations using the direct method with the Stillinger-Weber potential. The simulations were performed at four temperatures for two simulation cells of different sizes. The resulting thermal boundary resistance decreased with increasing temperature. The thermal boundary resistance was smaller for the large cell than for the small cell. Furthermore, the MD-predicted values were lower than the diffusion mismatch model (DMM)-predicted values. The phonon density of states (DOS) was calculated for all the cases to examine the underlying nature of the temperature dependence and size effect of thermal boundary resistance. We found that the phonon DOS was modified in the interface regions. The phonon DOS better matched between Si and Ge in the interface region than in the bulk region. Furthermore, in interface Si, the population of low-frequency phonons was found to increase with increasing temperature and cell size. We suggest that the increasing population of low-frequency phonons increased the phonon transmission coefficient at the interface, leading to the temperature dependence and size effect on thermal boundary resistance. © 2015 Author(s).

Loading ITOCHU Techno Solutions Corporation collaborators
Loading ITOCHU Techno Solutions Corporation collaborators