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Kobayashi, Keita; Nakamura, Hiroki; Okumura, Masahiko; Itakura, Mitsuhiro; Machida, Masahiko
Journal of Chemical Physics, 162(24), p.244508_1 - 244508_11, 2025/06
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)The specific heat anomaly in (anti-)fluorite structures was analyzed using machine learning molecular dynamics (MLMD) methods. By employing the Farthest Point Sampling method and the Bootstrap method, first-principles training data were efficiently generated, and machine learning potentials were created for thorium dioxide (fluorite structure) and lithium oxide (anti-fluorite structure). As a result, the MLMD method accurately reproduced the reported thermal properties of thorium dioxide and lithium oxide. These materials exhibit a specific heat anomaly at high temperatures due to sublattice disordering. However, the details are complex and not fully understood. In this study, by applying a local order parameter methodology, which has been used in the analysis of liquid-liquid phase transitions, we revealed that the anomalous specific heat in (anti-)fluorite structures can be interpreted as a consequence of local symmetry breaking.
Sakurai, Junya*; Torigata, Keisuke*; Matsunaga, Manabu*; Takanashi, Naoto*; Hibino, Shinya*; Kizu, Kenichi*; Morita, Akira*; Inomoto, Masahiro*; Shimohata, Nobuaki*; Toyota, Kodai; et al.
Tetsu To Hagane, 111(5), p.246 - 262, 2025/04
Hanari, Toshihide; Nakamura, Keita*; Imabuchi, Takashi; Kawabata, Kuniaki
Journal of Robotics and Mechatronics, 36(6), p.1537 - 1549, 2024/12
This paper describes three-dimensional (3D) reconstruction processes introducing the image selection method for efficiently generating a 3D model from an image sequence. To obtain suitable images for efficient 3D reconstruction, we tried to apply the image selection method to remove the redundant images in the image sequence. By the proposed method, the suitable images were selected from the image sequence based on optical flow measures and a fixed threshold. As a result, the proposed method can reduce the computational cost for the 3D reconstruction processes based on the image sequence acquired by the camera. We confirmed that the computational cost of the 3D reconstruction processes can reduce while keeping the 3D reconstruction accuracy at a constant level.
Nakamura, Keita*; Baba, Keita*; Watanobe, Yutaka*; Hanari, Toshihide; Matsumoto, Taku*; Imabuchi, Takashi; Kawabata, Kuniaki
Artificial Life and Robotics, 29(4), p.546 - 556, 2024/09
Nakamura, Keita*; Hanari, Toshihide; Imabuchi, Takashi; Kawabata, Kuniaki
Proceedings of 2024 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM 2024), p.7 - 8, 2024/07
Photogrammetry is a technique for 3D reconstruction of target objects from multiple images shot of the object. In the case of actual photography, the object may not be reconstructed due to the inability to shoot images suitable for photogrammetry because of vibration in the camera's angle of view of the object. Therefore, we implement this vibration by using random numbers and verify the influence of the magnitude of the vibration on the reconstruction result obtained by photogrammetry. The verification results show the relationship between the magnitude of the vibration and the success rate of 3D reconstruction.
Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki; Nakamura, Keita*; Yashiro, Hiroshi*
Artificial Life and Robotics, 29(2), p.358 - 371, 2024/05
Nakamura, Keita; Hanari, Toshihide; Matsumoto, Taku; Kawabata, Kuniaki; Yashiro, Hiroshi*
Journal of Robotics and Mechatronics, 36(1), p.115 - 124, 2024/02
Baba, Keita*; Watanobe, Yutaka*; Nakamura, Keita*; Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki
Proceedings of 29th International Symposium on Artificial Life and Robotics (AROB 29th 2024) (Internet), p.751 - 756, 2024/01
Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki; Yashiro, Hiroshi*; Nakamura, Keita*
Proceedings of 2023 IEEE International Conference on Robotics and Biomimetics (IEEE ROBIO 2023) (Internet), 7 Pages, 2023/12
Kobayashi, Keita; Okumura, Masahiko; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Urata, Shingo*; Suzuya, Kentaro
Scientific Reports (Internet), 13, p.18721_1 - 18721_12, 2023/11
Times Cited Count：18 Percentile：81.73(Multidisciplinary Sciences)The first sharp peak diffraction peak (FSDP) in the structure factor of amorphous materials is thought to reflect the medium-range order structure in amorphous materials, and the structural origin of the FSDP has been a subject of ongoing debate. In this study, we employed machine learning molecular dynamics (MLMD) with nearly first-principles calculation accuracy to investigate the structural origin of the FSDP in high-density silica glass. First, we successfully reproduced various experimental data of high-density silica glass using MLMD. Furthermore, we revealed that the development (or reduction) of the FSDP in high-density silica glass is characterized by the deformation behavior of ring structures in Si-O covalent bond networks under compression.
OKondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count：32 Percentile：95.20(Multidisciplinary Sciences)no abstracts in English
Ne at the transition into the island of inversion; Detailed structure study of NeWang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
Times Cited Count：5 Percentile：65.61(Astronomy & Astrophysics)Detailed 
-ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Hanari, Toshihide; Kawabata, Kuniaki; Nakamura, Keita*
Proceedings of 22nd World Congress of the International Federation of Automatic Control (IFAC 2023) (Internet) , p.11597 - 11602, 2023/07
Times Cited Count：0 Percentile：0.00(Automation & Control Systems)This paper describes the image selection method by multimodal detection for improving the computational efficiency of three-dimensional (3D) reconstruction based on images in a time-series. To decrease the calculation time of the 3D reconstruction, an adequate selection from the images is required. For this reason, we introduced multimodal detection by a statistical test on the image selection process, and then applied it to soundness evaluation of the displacements based on the optical flow between images acquired by a camera. The results suggest that suitable images can be extracted from the images in a time-series for decreasing the calculation time of the 3D reconstruction. Therefore, the suitable images selected by the proposed method contributed to efficiently performing the 3D reconstruction.
Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki; Yashiro, Hiroshi*; Nakamura, Keita*
Proceedings of 22nd World Congress of the International Federation of Automatic Control (IFAC 2023) (Internet) , p.12107 - 12112, 2023/07
Kobayashi, Keita; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Okumura, Masahiko
Materia, 62(3), p.175 - 181, 2023/03
no abstracts in English
Nakamura, Keita; Hanari, Toshihide; Kawabata, Kuniaki; Baba, Keita*
Artificial Life and Robotics, 28(2), p.352 - 360, 2023/02
Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki; Yashiro, Hiroshi*; Nakamura, Keita*
Proceedings of 28th International Symposium on Artificial Life and Robotics (AROB 28th 2023) (Internet), p.768 - 773, 2023/01
Kato, Masato; Machida, Masahiko; Hirooka, Shun; Nakamichi, Shinya; Ikusawa, Yoshihisa; Nakamura, Hiroki; Kobayashi, Keita; Ozawa, Takayuki; Maeda, Koji; Sasaki, Shinji; et al.
Materials Science and Fuel Technologies of Uranium and Plutonium mixed Oxide, 171 Pages, 2022/10
Innovative and advanced nuclear reactors using plutonium fuel has been developed in each country. In order to develop a new nuclear fuel, irradiation tests are indispensable, and it is necessary to demonstrate the performance and safety of nuclear fuels. If we can develop a technology that accurately simulates irradiation behavior as a technology that complements the irradiation test, the cost, time, and labor involved in nuclear fuel research and development will be greatly reduced. And safety and reliability can be significantly improved through simulation of nuclear fuel irradiation behavior. In order to evaluate the performance of nuclear fuel, it is necessary to know the physical and chemical properties of the fuel at high temperatures. And it is indispensable to develop a behavior model that describes various phenomena that occur during irradiation. In previous research and development, empirical methods with fitting parameters have been used in many parts of model development. However, empirical techniques can give very different results in areas where there is no data. Therefore, the purpose of this study is to construct a scientific descriptive model that can extrapolate the basic characteristics of fuel to the composition and temperature, and to develop an irradiation behavior analysis code to which the model is applied.
Nakamura, Keita; Baba, Keita*; Hanari, Toshihide; Kawabata, Kuniaki
Proceedings of 2022 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM 2022), p.1497 - 1498, 2022/07
Kobayashi, Keita; Okumura, Masahiko; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Cooper, M. W. D.*
Scientific Reports (Internet), 12(1), p.9808_1 - 9808_11, 2022/06
Times Cited Count：19 Percentile：75.82(Multidisciplinary Sciences)no abstracts in English
