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Kamiya, Tomohiro; Yoshida, Hiroyuki
Physics of Fluids, 37(10), p.103359_1 - 103359_23, 2025/10
In this study, we developed a conservative scheme based on a volume of fluid (VOF) and a ghost fluid method for liquid-gas two-phase compressible fluid simulations. We treated several one- and two-dimensional numerical problems to investigate the capability and applicability of the proposed method for compressible two-phase fluid simulations. The results agree well with the exact solutions or the numerical results of previous studies. Furthermore, the results also show that the proposed method can almost completely ensure the conservation property. Consequently, we concluded that the proposed method could simulate compressible two-phase flows and conserve mass, momentum, and total energy.
Kogawa, Hiroyuki; Wakui, Takashi; Futakawa, Masatoshi
Fluids (Internet), 10(1), p.3_1 - 3_15, 2025/01
Microbubbles have been applied in various fields. In mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for the life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, and result in reducing the damage. Recently, when the proton beam power was increased and the amount of injected gas bubbles was increased, unique damage morphologies were observed on solid-liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage; i.e. the directions of streak-like defects which are formed by connecting pit damage coincides with the direction of gas bubble trajectories, and the distances between pits was understandable taking the natural period of gas bubble vibration into account. This indicates that the gas microbubbles to reduce the macroscopic pressure waves have potential to be inceptions of the cavitation damage due to the microscopic pressure emitted from gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles; reducing macroscopic pressure waves and microscopic pressure due to bubble dynamics.
Takanashi, Koki; Seki, Takeshi*
Magune, 19(3), p.100 - 106, 2024/06
Perpendicular magnetic anisotropy of thin films currently plays an important role in spintronics as well as magnetic recording. Regarding perpendicular magnetic anisotropy, in this article, the fundamentals, the research history, and the recent research trends are reviewed, showing specific examples with perpendicular magnetization such as magnetic multilayers, ordered alloy films, rare earth-transition metal amorphous alloy films, and inhomogeneous or granular films. The physical origins for perpendicular magnetic anisotropy, including interface anisotropy due to structural symmetry breaking, magnetoelastic anisotropy due to strain, bulk-type magnetocrystalline anisotropy, and directional pair ordering of atoms, are discussed in each example.
Suzuki, Seiya; Nemoto, Yoshihiro*; Shiiki, Natsumi*; Nakayama, Yoshiko*; Takeguchi, Masaki*
Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)
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HRLSawada, Atsushi; Sakamoto, Kazuhiko*; Watahiki, Takanori*; Imai, Hisashi*
SKB P-17-06, 154 Pages, 2023/08
Collaborative Laboratories for Advanced Decommissioning Science; The University of Electro-Communications*
JAEA-Review 2022-029, 37 Pages, 2022/11
JAEA-Review-2022-029.pdf:1.89MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2021. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Semiautonomous remote-control technology of an articulated mobile robot to recover from stuck states" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The purpose of this work is to establish a recovery method of an articulated mobile robot from stuck states. In this work, a control method of the robot to recover from stuck states by using redundancy of the system is proposed. In addition, we develop two interfaces. One is a display interface as an operator can understand the situation of the robot and surrounding terrain, and the other is a control interface to provide a target motion using the proposed control method.
Kawashima, Hiroyuki; Kurosawa, Takuma*; Teshigawara, Makoto; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi; Kogawa, Hiroyuki
Advanced Experimental Mechanics, 7, p.43 - 48, 2022/08
Laser cutting is expected for reducing the volume of radioactive components by taking account of radioactive levels. The scattering of radioactive dust such as fume and spatter, which is generated throughout the laser cutting process, gets to be a major issue for practical usage in cutting highly radioactive substances. One of driving forces of the spatter is likely to be attributed to the cavitation bubble collapsing caused by rapid thermal loading due to laser irradiation. In order to elucidate the mechanism of spattering, the technique of spark discharge in water was availed to generate the cavitation bubble. The growth and collapse behaviors influenced by the interaction between a free surface and bubbles resulting the spattering phenomena are observed by using an ultra-high-speed video camera, and the numerical simulation was carried out as well.
Cantarel, V.; Yamagishi, Isao
Journal of Nuclear Science and Technology, 59(7), p.888 - 897, 2022/07
Times Cited Count：4 Percentile：67.35(Nuclear Science & Technology)
and GeO liquidsKawaguchi, Munemichi; Uno, Masayoshi*
Journal of Crystal Growth, 585, p.126590_1 - 126590_7, 2022/05
Phase-field mobility, 
, and crystal growth rates in crystallization of 11 oxides or mixed oxides in undercooled silicates, SiO and GeO liquids were calculated with a simple phase-field model (PFM), and material dependence of the was discussed. Ratios between experimental crystal growth rates and the PFM simulation with 
were confirmed to be proportional to a power of 
on the solid/liquid interface process during the crystal growth in a log-log plot. We determined that parameters, 
and 
, of the 
were 
to 
m
J
s and 
to 
, which were unique for the materials. It was confirmed that our PFM simulation with the determined reproduced quantitively the experimental crystal growth rates. The has a proportional relationship with the diffusion coefficient of a cation molar mass average per unit an oxygen molar mass at 
in a log-log graph. The depends on the sum of the cation molar mass per the oxygen molar mass, 
, in a compound. In 
, the decreases with the cation molar mass increasing. The assumed cause is that the B represents the degree of the temperature dependence of the . Since the cation molar mass is proportional to an inertial resistance of the cation transfer, the decreases with inverse of the cation molar mass. In crystallization of the silicates of heavy cation in 
, the saturates at approximately 0.67, which leads to 
.
Dehbi, A.*; Cheng, X.*; Liao, Y.*; Okagaki, Yuria; Pellegrini, M.*
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 15 Pages, 2022/03
Horiguchi, Naoki; Yoshida, Hiroyuki; Yamamura, Sota*; Fujiwara, Kota*; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 14 Pages, 2022/03
Collaborative Laboratories for Advanced Decommissioning Science; The University of Electro-Communications*
JAEA-Review 2021-025, 33 Pages, 2021/11
JAEA-Review-2021-025.pdf:1.68MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Semi- autonomous remote-control technology of an articulated mobile robot to recover from stuck states" conducted in FY2020. The purpose of this work is to establish a recovery method of an articulated mobile robot from stuck states. In this work, a control method of the robot to recover from stuck states by using redundancy of the system is proposed. In addition, we develop two interfaces. One is a display interface as an operator can understand the situation of the robot and surrounding terrain, and the other is a control interface to provide a target motion using the proposed control method. Finally, the effectiveness of them is demonstrated by experiments using an actual robot.
Collaborative Laboratories for Advanced Decommissioning Science; The University of Electro-Communications*
JAEA-Review 2020-025, 34 Pages, 2020/12
JAEA-Review-2020-025.pdf:2.73MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Semiautonomous Remote-control Technology of an Articulated Mobile Robot to Recover from Stuck States". The purpose of this work is to establish a recovery method of an articulated mobile robot from stuck states. In this work, a control method of the robot to recover from stuck states by using redundancy of the system is proposed. In addition, we develop two interfaces. One is a display interface as an operator can understand the situation of the robot and surrounding terrain, and the other is a control interface to provide a target motion using the proposed control method. Finally, the effectiveness of them is demonstrated by experiments using an actual robot.
Ito, Kanae; Harada, Masashi*; Yamada, Norifumi*; Kudo, Kenji*; Aoki, Hiroyuki; Kanaya, Toshiji*
Langmuir, 36(43), p.12830 - 12837, 2020/11
Times Cited Count：16 Percentile：52.54(Chemistry, Multidisciplinary)Wang, Y.*; Tomota, Yo*; Omura, Takahito*; Gong, W.*; Harjo, S.; Tanaka, Masahiko*
Acta Materialia, 196, p.565 - 575, 2020/09
Times Cited Count：45 Percentile：89.21(Materials Science, Multidisciplinary)El-Asaad, H.*; Nagai, Haruyasu; Sagara, Hiroshi*; Han, C. Y.*
Annals of Nuclear Energy, 141, p.107292_1 - 107292_9, 2020/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Atmospheric dispersion simulations can provide crucial information to assess radioactive plumes in the environment for nuclear emergency preparedness. However, it is a difficult and time-consuming task to make simulations assuming many possible scenarios and to derive data from a vast number of results. Therefore, an interface was developed to assist users in conveying characteristics of plumes from simulation results. The interface uses a large database that contains WSPEEDI-II simulations for the first 20-days of radioactive release from the Fukushima Daiichi Nuclear Power Plant, and it displays essential quantitative data to the user from the database. The user may conduct sensitivity analysis with the help of the interface by changing release condition to generate many different case scenarios.
Uesawa, Shinichiro; Yoshida, Hiroyuki
Mechanical Engineering Journal (Internet), 7(3), p.19-00539_1 - 19-00539_9, 2020/06
Uesawa, Shinichiro; Miyahara, Naoya; Horiguchi, Naoki; Yoshida, Hiroyuki; Osaka, Masahiko
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05
Yoshida, Hiroyuki; Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Ose, Yasuo*
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11
Gu, B.; Takahashi, Saburo*; Maekawa, Sadamichi
Physical Review B, 96(21), p.214423_1 - 214423_6, 2017/12
Times Cited Count：9 Percentile：37.85(Materials Science, Multidisciplinary)