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Hashimoto, Kei*; Shiwaku, Toru*; Aoki, Hiroyuki; Yokoyama, Hideaki*; Mayumi, Koichi*; Ito, Kozo*
Science Advances (Internet), 9(47), p.eadi8505_1 - eadi8505_8, 2023/11
Times Cited Count：5 Percentile：45.8(Multidisciplinary Sciences)
pellet in molten Zr claddingIto, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*
Journal of Nuclear Science and Technology, 60(4), p.450 - 459, 2023/04
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Yoshida, Masayuki*; Nishihata, Itsuki*; Matsuda, Tomoki*; Ito, Yusuke*; Sugita, Naohiko*; Shiro, Ayumi*; Shobu, Takahisa; Arakawa, Kazuto*; Hirose, Akio*; Sano, Tomokazu*
Journal of Applied Physics, 132(7), p.075101_1 - 075101_9, 2022/08
Times Cited Count：5 Percentile：64.66(Physics, Applied)Uehara, Akihiro*; Matsumura, Daiju; Tsuji, Takuya; Yakumaru, Haruko*; Tanaka, Izumi*; Shiro, Ayumi*; Saito, Hiroyuki*; Ishihara, Hiroshi*; Homma-Takeda, Shino*
Analytical Methods, 14(24), p.2439 - 2445, 2022/06
Times Cited Count：3 Percentile：57.45(Chemistry, Analytical)Uehara, Akihiro*; Shuhui, X.*; Sato, Ryotaro*; Matsumura, Daiju; Tsuji, Takuya; Yakumaru, Haruko*; Shiro, Ayumi*; Saito, Hiroyuki*; Tanaka, Izumi*; Ishihara, Hiroshi*; et al.
Advances in X-Ray Chemical Analysis, Japan, 53, p.223 - 229, 2022/03
no abstracts in English
Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.
Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12
Times Cited Count：6 Percentile：49.29(Geosciences, Multidisciplinary)The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
Tetsu To Hagane, 107(9), p.760 - 768, 2021/09
Times Cited Count：0 Percentile：0(Metallurgy & Metallurgical Engineering)no abstracts in English
Shibayama, Yuki; Hojo, Tomohiko*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Matsuno, Takashi*; Akiyama, Eiji*
ISIJ International, 61(4), p.1322 - 1329, 2021/04
Times Cited Count：3 Percentile：24.75(Metallurgy & Metallurgical Engineering)Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
ISIJ International, 61(4), p.1170 - 1178, 2021/04
Times Cited Count：3 Percentile：24.75(Metallurgy & Metallurgical Engineering)Hojo, Tomohiko*; Akiyama, Eiji*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Kinugasa, Junichiro*; Yuse, Fumio*
Corrosion Science, 177, p.108957_1 - 108957_9, 2020/12
Times Cited Count：18 Percentile：75.61(Materials Science, Multidisciplinary)Hydrogen assisted cracking on hemispherically-stretch-formed specimens of transformation induced plasticity-aided martensitic steel was investigated. Hydrogen charging induced cracking around the foot of the impression formed on the steel sheet, and the cracks propagated along the radial direction toward the hillside and the plains. Distributions of stress, plastic strain and volume fraction of retained austenite were analyzed employing the energy-dispersive X-ray diffraction method utilizing the synchrotron X-ray radiation at SPring-8. It was notable that the crack initiation took place in the region where the measured tensile stress was the highest. Influences of plastic strain and resulted martensitic transformation were also suggested.
Seki, Akiyuki; Mayumi, Akie; Wainwright-Murakami, Haruko*; Saito, Kimiaki; Takemiya, Hiroshi; Idomura, Yasuhiro
Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.158 - 164, 2020/10
We developed a method to estimate the temporal change of the air dose rate at the location with sparse (in time) measurements by using the continuous measurement data from the nearby monitoring post. This method determines an observation model from the correlation between sparse data at the target location and dense data at the monitoring post based on a hierarchical Bayesian model. The developed method was validated against the air dose rate measured at the monitoring posts in Fukushima prefecture from 2012 to 2017. The results showed that the developed method can predict the air dose rate at almost all target locations with an error rate of less than 10%.
Hojo, Tomohiko*; Kumai, B.*; Koyama, Motomichi*; Akiyama, Eiji*; Waki, Hiroyuki*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Nagasawa, Akihiko*
International Journal of Fracture, 224(2), p.253 - 260, 2020/08
Times Cited Count：14 Percentile：66.22(Materials Science, Multidisciplinary)In the study, the pre-strain effect on hydrogen embrittlement property of the ultra-high-strength transformation-induced plasticity -aided bainitic ferrite steel was investigated towards application for automobile frame parts. 3-10% tensile pre-strain suppressed hydrogen-induced mechanical degradation relative to total elongation while 12-15% pre-strained specimen did not exhibit elongation after hydrogen charging. The advantageous effect of the 3-10% pre-strain was attributed to the suppression of crack initiation related to retained austenite. The TRIP by pre-straining decreased the volume fraction of retained austenite before hydrogen charging, thereby reducing existing probabilities of preferential crack initiation sites and propagation paths. Conversely, high pre-strain such as 12-15% does not effectively work due to work hardening resulting in increases in hydrogen embrittlement susceptibility and a significant increase in hydrogen content due to the multiplication of dislocations.
Miyakawa, Susumu*; Ito, Toshimasa*; Iwahori, Keisuke*; Aoyama, Yoshihiko*; Kubo, Ryosuke*; Murata, Shinji*; Shobu, Takahisa; Shiro, Ayumi*; Kajiwara, Kentaro*
Zairyo, 69(4), p.308 - 314, 2020/04
White etching area which looks white with nital corrosive liquid may be recognized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial X-ray measurement equipment (B method) were investigated. The former was modified by surface residual stress according to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
Tsutsui, Nao; Ban, Yasutoshi; Suzuki, Hideya*; Nakase, Masahiko*; Ito, Sayumi*; Inaba, Yusuke*; Matsumura, Tatsuro; Takeshita, Kenji*
Analytical Sciences, 36(2), p.241 - 246, 2020/02
Times Cited Count：22 Percentile：81.93(Chemistry, Analytical)To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and 
-dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform the actual extraction flow sheet. The slopes of the distribution ratio versus TDdPTDA concentration and the distribution ratio versus nitric acid concentration were similar for F-3 and nitrobenzene systems but different from -dodecane system. These differences were attributed to the characteristics of the diluents. This study reveals high distribution ratios of Am (
) and Cm ( 
) for TDdPTDA, with the high separation factors (
s) of Am from Lns enough for their separation.
Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*
Metals, 9(11), p.1192_1 - 1192_13, 2019/11
Times Cited Count：15 Percentile：64.79(Materials Science, Multidisciplinary)The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.
Xu, P. G.; Harjo, S.; Ojima, Mayumi*; Suzuki, Hiroshi; Ito, Takayoshi*; Gong, W.; Vogel, S. C.*; Inoue, Junya*; Tomota, Yo*; Aizawa, Kazuya; et al.
Journal of Applied Crystallography, 51(3), p.746 - 760, 2018/06
Times Cited Count：26 Percentile：90.31(Chemistry, Multidisciplinary)Mayumi, Ren*; Semboshi, Satoshi*; Okamoto, Yoshihiro; Saito, Yuichi*; Yoshiie, Toshimasa*; Iwase, Akihiro*
Transactions of the Materials Research Society of Japan, 42(1), p.9 - 14, 2017/02
AlCu binary alloys were irradiated with 16 MeV Au, 4.5 MeV Ni or 4.5 MeV Al ions at room temperature. Changes in surface hardness and the local atomic structure around Cu atoms were examined by using the Vickers hardness measurement and the EXAFS measurements, respectively. Some specimens were aged at 453 K and Vickers hardness was measured. The computer simulation was also performed by using the rate equation method. The hardness of irradiated specimens increased much faster than that of the aged specimens and it became larger than the maximum value of the hardness for the aged specimens. The comparison of the experimental EXAFS result with that of FEFF simulation suggests that the ion irradiation produced small Cu precipitates in the specimens. The computer simulation visualized the growth process of Cu precipitates during the irradiation, and the result qualitatively corresponds to the experimental result.
SGo, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hiroyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.
JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06
Endo, Hitoshi; Mayumi, Koichi*; Osaka, Noboru*; Ito, Kozo*; Shibayama, Mitsuhiro*
Polymer Journal, 43(2), p.155 - 163, 2011/02
Times Cited Count：9 Percentile：29.92(Polymer Science)Polyrotaxane (PR) possesses a supramolecular structure in which cyclic molecules are threaded into an axial polymer. In this study, the static structure of PR dissolved in a good solvent was investigated using contrast variation small-angle neutron scattering. The conformation of the axial linear polymer and the alignment of cyclic molecules within the axial polymer were evaluated quantitatively with the help of a detailed derivation of scattering theory. The decomposed partial scattering functions of the cyclic molecules and the axial polymer and the cross-correlation between cyclic molecules and an axial polymer strongly supported the idea that the alignment of cyclic molecules threaded on the axial polymer is random. On the basis of experimental observation, the entropic origin of the stiffening of PR due to the array of cyclic molecules is discussed.
Ito, Masakazu*; Okamoto, Mayumi*; Shibata, Masahiro; Sasaki, Yasuo; Danhara, Toru*; Suzuki, Keizo*; Watanabe, Takashi*
PNC TN8430 93-003, 114 Pages, 1993/08
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