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Journal Articles

Atomic position and the chemical state of an active Sn dopant for Sn-doped $$beta$$-Ga$$_{2}$$O$$_{3}$$(001)

Tsai, Y. H.*; Kobata, Masaaki; Fukuda, Tatsuo; Tanida, Hajime; Kobayashi, Toru; Yamashita, Yoshiyuki*

Applied Physics Letters, 124(11), p.112105_1 - 112105_5, 2024/03

 Times Cited Count:0 Percentile:0.00

Journal Articles

In-situ neutron diffraction study of lattice deformation behaviour of commercially pure titanium at cryogenic temperature

Lee, M.-S.*; Kawasaki, Takuro; Yamashita, Takayuki*; Harjo, S.; Hyun, Y.-T.*; Jeong, Y.*; Jun, T.-S.*

Scientific Reports (Internet), 12(1), p.3719_1 - 3719_10, 2022/03

 Times Cited Count:6 Percentile:61.59(Multidisciplinary Sciences)

Journal Articles

Deep learning approach for an interface structure analysis with a large statistical noise in neutron reflectometry

Aoki, Hiroyuki; Liu, Y.*; Yamashita, Takashi*

Scientific Reports (Internet), 11(1), p.22711_1 - 22711_9, 2021/11

 Times Cited Count:9 Percentile:66.25(Multidisciplinary Sciences)

Journal Articles

GPU-acceleration of locally mesh allocated two phase flow solver for nuclear reactors

Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.210 - 215, 2020/10

This paper presents a GPU-based Poisson solver on a block-based adaptive mesh refinement (block-AMR) framework. The block-AMR method is essential for GPU computation and efficient description of the nuclear reactor. In this paper, we successfully implement a conjugate gradient method with a state-of-the-art multi-grid preconditioner (MG-CG) on the block-AMR framework. GPU kernel performance was measured on the GPU-based supercomputer TSUBAME3.0. The bandwidth of a vector-vector sum, a matrix-vector product, and a dot product in the CG kernel gave good performance at about 60% of the peak performance. In the MG kernel, the smoothers in a three-stage V-cycle MG method are implemented using a mixed precision RB-SOR method, which also gave good performance. For a large-scale Poisson problem with $$453.0 times 10^6$$ cells, the developed MG-CG method reduced the number of iterations to less than 30% and achieved $$times$$ 2.5 speedup compared with the original preconditioned CG method.

JAEA Reports

The International Atomic Energy Agency Nuclear Energy Management School 2012

Ohgama, Kazuya; Ando, Yoko; Yamaguchi, Mika; Ikuta, Yuko; Shinohara, Nobuo; Murakami, Hiroyuki; Yamashita, Kiyonobu; Uesaka, Mitsuru*; Demachi, Kazuyuki*; Komiyama, Ryoichi*; et al.

JAEA-Review 2013-004, 76 Pages, 2013/05

JAEA-Review-2013-004.pdf:13.53MB

JAEA together with the Japan Nuclear Human Resource Development Network (JN-HRD Net), the University of Tokyo (UT) and the Japan Atomic Industrial Forum (JAIF) cohosted the IAEA-Nuclear Energy Management School in Tokai Village, aiming that Japan will be the center of nuclear HRD in the Asian region. In the school, not only lectures by IAEA experts, but also lectures by Japanese experts and technical visits were included for foreign participants. The school contributed to the internationalization of Japanese young professionals, development of nuclear human resource of other countries, and enhancement of cooperation between IAEA and Japan. Additionally, collaborative relationship within JN-HRD Net was strengthened by the school. In this report, findings obtained during the preparatory work and the school period are reported for future international nuclear HRD activities in Japan.

Journal Articles

Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), 2; A Comparative study on edaravone derivatives

Hata, Kuniki; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Fu, H. Y.*; Yamashita, Shinichi; Nakagawa, Hidehiko*

Journal of Radiation Research, 52(1), p.15 - 23, 2011/01

 Times Cited Count:21 Percentile:60.99(Biology)

Journal Articles

Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

Yan, Y.*; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Hata, Kuniki; Meesungnoen, J.*; Jay-Gerin, J.-P.*

Canadian Journal of Chemistry, 88(10), p.1026 - 1033, 2010/10

 Times Cited Count:1 Percentile:7.10(Chemistry, Multidisciplinary)

The optical absorption spectra of the solvated electron (e$$_{rm sol}^-$$) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220-270 $$^{circ}$$C. Over the density range studied ($$sim$$0.45-0.59 g/cm$$^{3}$$), the position of the absorption maximum ($$E$$$$_{rm Amax}$$) of e$$_{rm sol}^-$$ is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, $$E$$$$_{rm Amax}$$ decreases monotonically with increasing temperature in passing through the phase transition at $$T$$$$_{rm c}$$ (239.5 $$^{circ}$$C). By contrast, at a fixed density, $$E$$$$_{rm Amax}$$ exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and supercritical regimes.

Journal Articles

Pulse radiolysis studies on the temperature-dependent spectrum and the time-dependent yield of solvated electron in Propane-1,2,3-triol

Lin, M.; Fu, H.*; Lampre, I.*; De Waele, V.*; Muroya, Yusa*; Yan, Y.*; Yamashita, Shinichi; Katsumura, Yosuke; Mostafavi, M.*

Journal of Physical Chemistry A, 113(44), p.12193 - 12198, 2009/10

 Times Cited Count:7 Percentile:22.32(Chemistry, Physical)

With a revisit of the absorption coefficient of the solvated electron in propane-1,2,3-triol, the temperature dependent behavior of the absorption spectrum of solvated electron was studied from room temperature to 573 K by pulse radiolysis techniques. The change in the absorption spectrum of solvated electron in propane-1,2,3-triol observed by cooling down from a high temperature to 333 K is compared with that occurring during the electron solvation process at 333 K. The effect of the specific molecular structure of propane-1,2,3-triol compared to other alcohols is discussed.

Journal Articles

Development of a SH wave single unit electromagnetic acoustic transducer (EMAT) for MONJU reactor vessel in-service inspection

Xu, Y.*; Tagawa, Akihiro; Fujiki, Kazunari*; Ueda, Masashi; Yamashita, Takuya

Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 9 Pages, 2009/07

In-service inspection is carried out to confirm the integrity of the main components of "MONJU". The ambient temperature during the inspection is 200 $$^{circ}$$C and the irradiation field is 10 Gy/hr. A Periodic Permanent Magnet (PPM) structure has been used for electromagnetic acoustic transducer (EMAT). The PPM structure is the structure of putting in order alternately the S pole and N pole laterally magnetized magnets. A Halbach magnet structure is the structure which sandwiched the longitudinally magnetized magnets between each magnet of PPM structure. Thereby, magnetic flux density is improved 1.4 times. Moreover, it also checked aiming at 4 times as many improvement in detection sensitivity as this by a new signal processing method. The high temperature characteristic and high temperature durability of Halbach type EMAT in 200 hours which corresponds the twice of inspection time under the 200 $$^{circ}$$C inspection environment are reported.

Journal Articles

Neutronics analysis of the ITER NB system; Nuclear responses of the components and shutdown dose around the NB injector

Shibata, Keiichiro*; Maki, Koichi*; Inoue, Takashi*; Hanada, Masaya; Okumura, Yoshikazu; Yamashita, Y.*

Fusion Engineering and Design, 51-52, p.357 - 362, 2000/11

 Times Cited Count:1 Percentile:12.05(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design analysis for reducing dose rate in the NBI to realize direct access by workers for a fusion experimental reactor

Inoue, Takashi; ; ; Yamashita, Y.*

Fusion Technology 1996, 0, p.1799 - 1802, 1996/00

no abstracts in English

JAEA Reports

ITER neutral beam injection system; Japanese design proposal

Ohara, Yoshihiro; Tanaka, Shigeru; Akiba, Masato; Araki, Masanori; Fujisawa, Noboru; Hanada, Masaya; Inoue, Takashi; ; Mizuno, Makoto; Okumura, Yoshikazu; et al.

JAERI-M 91-052, 176 Pages, 1991/03

JAERI-M-91-052.pdf:4.07MB

no abstracts in English

Journal Articles

Neutronics of neutral beam injector for ITER; Japanese proposal

Inoue, Takashi; Akiba, Masato; Araki, Masanori; Hanada, Masaya; ; Mizuno, Makoto; Okumura, Yoshikazu; Ohara, Yoshihiro; Seki, Masahiro; Tanaka, Shigeru; et al.

Fusion Engineering and Design, 18, p.369 - 376, 1991/00

 Times Cited Count:3 Percentile:40.77(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Inverter type high voltage DC power supply for negative-ion-based neutral beam injectors

Mizuno, Makoto; Dairaku, Masayuki; Ohara, Yoshihiro; ; Tanaka, Shigeru; ; Watanabe, Kazuhiro; Yamashita, Y.*;

IEEE 13th Symp. on Fusion Engineering, Vol. 1, p.574 - 577, 1989/00

no abstracts in English

Oral presentation

Pulse radiolysis study on temperature dependent absorption spectra and temporal behaviors of the yield of solvated electron in poly-alcohols

Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Yan, Y.*; Hata, Kuniki; Peng, J.

no journal, , 

With a re-evaluation of the extinction coefficients of solvated electron in 1,2-ethanediol (12ED), 1,2-propanediol (12PD), 1,3-propanediol (13PD), and glycerol (GLY), the time-dependent radiolytic yields of the solvated electron in these diols from the picosecond to the microsecond time range are described. The radiolytic yield of solvated electron in these viscous solvents is found to be quite different from that in aqueous solution. The temperature dependent absorption spectra of the solvated electron in 12ED, 12PD, 13PD, and GLY have been also investigated. Very interestingly, the red-shift of the spectrum with increasing temperature corresponds very well with the spectral shift of electron solvation obtained by femtosecond laser photolysis.

Oral presentation

Picosecond pulse radiolysis study on fast spur reaction kinetics in high temperature water up to supercritical states

Muroya, Yusa*; Lin, M.; Yan, Y.*; Han, Z.*; Yamashita, Shinichi; Ueda, Toru*; Mostafavi, M.*; Katsumura, Yosuke*

no journal, , 

no abstracts in English

Oral presentation

Antioxidative and radioprotective effects of edaravone

Hata, Kuniki; Urushibara, Ayumi; Lin, M.; Muroya, Yusa*; Yamashita, Shinichi; Yokoya, Akinari; Fu, H. Y.*; Katsumura, Yosuke*

no journal, , 

Oral presentation

Microbes capture and expose experiments on ISS proposed in Tanpopo mission

Kawaguchi, Yuko*; Sugino, Tomohiro*; Yang, Y.*; Takahashi, Yuta*; Yoshimura, Yoshitaka*; Tsuji, Takashi*; Kobayashi, Kensei*; Tabata, Makoto*; Hashimoto, Hirofumi*; Narumi, Issei; et al.

no journal, , 

no abstracts in English

Oral presentation

Tanpopo: astrobiology exposure and micrometeoroid-capture experiments; On the capture and space exposure experiments

Yokobori, Shinichi*; Yang, Y.*; Kawaguchi, Yuko*; Sugino, Tomohiro*; Takahashi, Yuta*; Narumi, Issei; Takahashi, Yuichi*; Hayashi, Nobuhiro*; Yoshimura, Yoshitaka*; Tabata, Makoto*; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of exascale matrix solvers based on communication avoiding algorithms

Imamura, Toshiyuki*; Idomura, Yasuhiro; Ina, Takuya*; Yamashita, Susumu; Onodera, Naoyuki; Ali, Y.*; Yamada, Susumu

no journal, , 

Towards exascale computing on the Post-K computer, a novel matrix solvers are developed by using communication avoiding algorithms. In this talk, we review two main approaches used in the three-dimensional thermal hydraulic multi-phase CFD code, JUPITER. One is a communication avoiding Krylov sub-space method, in which multiple basis vectors are generated and orthogonalized at once to reduce global collective communications. The other is a Krylov sub-space method with multi-grid preconditioning, which dramatically improve convergence property and reduce the number of iterations, and thus, global collective communications. We compare these approaches on the latest many core platform.

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