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Nakata, Koki; Onuma, Yuichi*; Kim, S. K.*
Physical Review B, 105(18), p.184409_1 - 184409_7, 2022/05
Times Cited Count：2 Percentile：34.67(Materials Science, Multidisciplinary)We show that the ratio of the thermal to spin transport coefficient of magnons in insulating magnets exhibits a different behavior from the linear response and the universal law breaks down in the strong nonlinear regime.
Nakata, Koki; Onuma, Yuichi*
Physical Review B, 105(14), p.144436_1 - 144436_7, 2022/04
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)Using a junction of the ferromagnetic insulators irradiated by linearly polarized laser, we propose a method for the generation of dc and ac spin currents of magnons across the junction interface, and provide an analytical formula for magnon transport induced by the inversion symmetry breaking.
Nakata, Koki; Onuma, Yuichi*
Physical Review B, 104(6), p.064408_1 - 064408_8, 2021/08
Times Cited Count：9 Percentile：62.1(Materials Science, Multidisciplinary)Using the quantum Boltzmann equation for Bose systems, we have developed the formula for thermal transport of bosons and found a difference from the conventional, with a particular focus on magnons.
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JNC TY9400 2003-006, 481 Pages, 2003/05
JNC-TY9400-2003-006.pdf:2.27MB
Coupled, macro-micro modeling based on real microstructure have been developed for hot deformation of structures and equipments of nuclear plant. This modeling method is based on the homogenization method and related computational and theoretical mechanics for materials. Its features are summarized below. (1)Hierarchical modeling:Hot deformations of structual members and specimens as well as deformation of microstructure are evaluated independently. Therefore, macro-level damage can be avaluated only with the constitutional relations among materials and micro-machanics of hot deformation. (2)Coupled modeling:Models for deformation, thermal conduction and diffusion are strongly coupled in each level of hierarchy. (3)Real microstructure:Automatically modeling based on real microstructure taken from optical microscope enabled to describe the continuum mechanics of polycrystalline materials. Especislly void generation can be treated appropriately. (4)Micro-mechanics of hot deformation:Degradation procedure of materials from virgin materials to failure can be expressed because void generation, void coalescence and crack formation are treated directly. (5)Damage of structural members and specimens: Damage of structural members and specimens could be evaluated from homogenized mechanical properties calculated from mechanical properties of micro-structure. Developed modeling method makes full yse of the micro-structure obtained from microscopic observation and experimental data of mechanical properties of structual members and specimens toward the quantitative avaluation of material and structural integrity.
