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Tanaka M.,Toyota Central RD Labs. Inc. | Balzani D.,TU Dresden | Schroder J.,University of Duisburg - Essen
Lecture Notes in Applied and Computational Mechanics | Year: 2016

In this contribution robust numerical schemes for an efficient implementation of tangent matrices in finite strain problems are presented and their performance is investigated through the analysis of hyperelastic materials, inelastic standard dissipative materials in the context of incremental variational formulations, and thermo-mechanics. The schemes are based on highly accurate and robust numerical differentiation approaches which use non-real numbers, i.e., complex variables and hyper-dual numbers. The main advantage of these approaches are that, contrary to the classical finite difference scheme, no round-off errors in the perturbations due to floating-point arithmetics exist within the calculation of the tangent matrices. This results in a method which is independent of perturbation values (in case of complex step derivative approximations if sufficiently small perturbations are chosen). An efficient algorithmic treatment is presented which enables a straightforward implementation of the method in any standard finite-element program. By means of hyperelastic, finite strain elastoplastic, and thermo-elastoplastic boundary value problems, the performance of the proposed approaches is analyzed. © Springer International Publishing Switzerland 2016.

Hazama H.,Toyota Central RD Labs. Inc. | Matsubara M.,Toyota Central RD Labs. Inc. | Asahi R.,Toyota Central RD Labs. Inc. | Takeuchi T.,Nagoya University
Journal of Applied Physics | Year: 2011

We have synthesized off-stoichiometric Ti-Ni-Sn half-Heusler thermoelectrics in order to investigate the relation between randomly distributed defects and thermoelectric properties. A small change in the composition of Ti-Ni-Sn causes a remarkable change in the thermal conductivity. An excess content of Ni realizes a low thermal conductivity of 2.93 W/mK at room temperature while keeping a high power factor. The low thermal conductivity originates in the defects generated by an excess content of Ni. To investigate the detailed defect structure, we have performed first-principles calculations and compared with x ray photoemission spectroscopy measurement. Based on these analyses, we conclude that the excess Ni atoms randomly occupy the vacant sites in the half-Heusler structure, which play as phonon scattering centers, resulting in significant improvement of the figure of merit without any substitutions of expensive heavy elements, such as Zr and Hf. © 2011 American Institute of Physics.

Sasaki T.,Paul Scherrer Institute | Sasaki T.,Toyota Central RD Labs. Inc. | Godbole V.,Paul Scherrer Institute | Takeuchi Y.,Toyota Central RD Labs. Inc. | And 2 more authors.
Journal of the Electrochemical Society | Year: 2011

The effect of Mg-substitution in Li(Ni,Co,Al)O2 during overcharge was studied by scanning electron microscopy (SEM) observations and in situ synchrotron X-ray Diffraction (XRD) measurements. The higher Mg-substituted samples showed higher electrochemical stability during the overcharge cycling. After overcharge, the non Mg-substituted sample featured many cracks, not only at the grain boundaries in secondary particles but also inside the primary particles. This morphological change is assigned to the drastic shrinking of the c-axis during overcharge. The Mg-substitution suppressed the c-axis shrinking and consequently avoided the cracking of the particles. This effect of Mg-substitution in Li(Ni,Co,Al)O2 correlates with the electrochemical stability during the overcharge cycling. © 2011 The Electrochemical Society.

Murai S.,Kyoto University | Yao S.,Kyoto University | Nakamura T.,Toyota Central RD Labs. Inc. | Kawamoto T.,Kyoto University | And 3 more authors.
Applied Physics Letters | Year: 2012

We have prepared a three-dimensional magnetophotonic crystal and observed modulated Faraday rotation around its photonic band gap. The magnetophotonic crystal was prepared by the self-assembly of highly monodispersed silica spheres, which were heavily impregnated with maghemite (γ - Fe 2 O 3) nanoparticles. The slab sample with a thickness of 10 μ m shows a clear photonic band gap centered at λ 620 nm in optical transmittance. Faraday rotation is notably modified inside the photonic band gap. © 2012 American Institute of Physics.

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