Local and electronic structures of BaTiO/KNbO nanocomposite particles

Yoneda, Yasuhiro; Kobayashi, Toru; Tsuji, Takuya; Shibata, Goro; Takeda, Yukiharu*; Saito, Yuji; Khanal, G. P.*; Fujii, Ichiro*; Ueno, Shintaro*; Sato, Yukio*; et al.

Japanese Journal of Applied Physics, 64(8), p.08SP07_1 - 08SP07_8, 2025/08

https://doi.org/10.35848/1347-4065/adf4f1

It has become possible to synthesize high-quality composite nanoparticles in which a different material is grown on the surface of nanoparticle crystals. To evaluate such nanostructures, it is effective to combine different evaluation methods at various scales. We performed various structural and electronic state evaluations of BaTiO/KNbO nanocomposite particles using synchrotron radiation. From the structural evaluation, it was confirmed that the nanocomposite particles have a core of 100 nm of BaTiO covered with 20 nm of KNbO. The O-K absorption edge spectrum of the outermost surface KNbO was different from that of the bulk and nanoparticles, and it was found that the chemical bonding state changes when KNbO is made into composite particles.

Development of a control system for core-sampling USV that combines sliding mode control and neural network

Morito, Makoto*; Fujii, Shun*; Yoshimura, Koki*; Sanada, Yukihisa; Baba, Shoichiro*; Matsunaga, Hiroshi*; Mori, Takami*; Sato, Keiichiro*; Tahara, Junichiro*

Proceedings of 34th International Ocean and Polar Engineering Conference (ISOPE-2024), p.3754 - 3761, 2024/06

This study proposes a method that combines sliding mode control and neural networks as a control method for unmanned surface vehicle to measure radiation in submarine soil. Sliding mode control is used as the base of control input, and corrective inputs are added using a neural network controller so that one of the parameters of sliding mode control, , and its rate of change are reduced. After producing a control system using this method, we conducted simulation tests and sea area tests to evaluate whether the survey could be conducted using this method.

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Invention of automatic movement and dynamic positioning control method of unmanned vessel for mud mining

Fujii, Shun*; Kato, Tetsu*; Kawamura, Yamato*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa

Proceedings of 26th International Symposium on Artificial Life and Robotics (AROB 26th 2021), p.280 - 285, 2021/01

In recent years, autonomously navigating unmanned vessels have been actively studied, and many of these vessels are designed to perform unmanned operations such as observation and transportation. On the other hand, this study uses an unmanned ship with a moon pool that collects seabed mud, which is difficult for ordinary ships. Vessels used since the area are highly turbulent due to wind, so it is necessary to maintain a fixed point and orientation when removing mud. The ship is equipped with side thrusters to maintain a fixed point and bow direction. In this study, the control method was devised to maintain fixed point and orientation, and the control method is based on robust sliding mode control. The proposed control method was verified by simulation, and the desired behavior was confirmed.

Short- and middle-ranges order structures of KNbO nanocrystals

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Nagata, Hajime*; Ohara, Koji*; Wada, Satoshi*

Japanese Journal of Applied Physics, 58(SL), p.SLLA03_1 - SLLA03_7, 2019/11

https://doi.org/10.7567/1347-4065/ab37e2

Crack expansion and fracturing mode of hydraulic refracturing from Acoustic Emission monitoring in a small-scale field experiment

Ishida, Tsuyoshi*; Fujito, Wataru*; Yamashita, Hiroto*; Naoi, Makoto*; Fujii, Hirokazu*; Suzuki, Kenichiro*; Matsui, Hiroya

Rock Mechanics and Rock Engineering, 52(2), p.543 - 553, 2019/02

AA2017-0694.pdf:2.54MB

https://doi.org/10.1007/s00603-018-1697-5

We pressurized and injected water in a hole drilled downward from a floor of the 500 m level gallery in MIU, central Japan. Acoustic emissions (AEs) monitored with 16 sensors in four boreholes located 1 m away from the HF hole exhibited two-dimensional distributions, which likely delineate a crack induced by the fracturing. Expansions of the regions in which AEs occurred were observed only immediately after the first and second BDs. Many AE events in other periods were distributed within the regions where AE events had already occurred. The initial motion polarities of P-waves indicate that tensile-dominant AE events occurred when the regions expanded and they were distributed primarily on the frontiers of the regions where AE events had already occurred. The experimental results suggest that increasing the injection flow rate is effective for generating new cracks in the refracturing, with the new crack expansions being induced by tensile fracturing.

Electronic structure of BaFeO studied by X-ray spectroscopy

Mizumaki, Masaichiro*; Fujii, Hitoshi*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Uozumi, Takayuki*; Takano, Mikio*

Physica Status Solidi (C), 12(6), p.818 - 821, 2015/06

https://doi.org/10.1002/pssc.201400252

We investigated the electronic structure of BaFeO by using HAXPES and XAS measurements and first principle studies. The experimental and theoretical results indicated that BaFeO is a negative charge transfer compound. We concluded that the on-site Coulomb energy and the strong hybridization between Fe-3d and O-2p orbitals play a very important role of emergence of negative charge transfer. And we found the new structure in the Fe-2p XPS spectrum and concluded this structure is originated from non-local screening.

Quantitative analysis of neodymium, uranium, and palladium in nitric acid solution by reflection absorption spectrophotometry

Fujii, Toshiyuki*; Egusa, Soichiro*; Uehara, Akihiro*; Yamana, Hajimu*; Morita, Yasuji

Journal of Radioanalytical and Nuclear Chemistry, 295(3), p.2059 - 2062, 2013/03

https://doi.org/10.1007/s10967-012-2211-2

Quantitative analysis of Nd, U, or Pd in 3 mol dm (M) HNO was performed by reflection absorption spectrophotometry at ultraviolet-visible-near-infrared (UV/Vis/NIR) region. A sample chamber with optics for reflection measurement was designed and attached to a UV/Vis/NIR spectrophotometer by optical fibers. The reflection absorbance showed linear relations with concentrations of Nd, U, and Pd at the absorbance region less than 0.1. The quantitative analysis was found to be possible for 3 M HNO solutions containing [Nd] ca. 0.2 M, [U] ca. 0.04 M, or [Pd] ca. 0.01 M at maximum.

Electronic absorption spectra of palladium(II) in concentrated nitric acid solutions

Fujii, Toshiyuki*; Egusa, Soichiro*; Uehara, Akihiro*; Kirishima, Akira*; Yamagishi, Isao; Morita, Yasuji; Yamana, Hajimu*

Journal of Radioanalytical and Nuclear Chemistry, 290(2), p.475 - 478, 2011/11

https://doi.org/10.1007/s10967-011-1284-7

Palladium complexation in concentrated nitric acid solutions was studied by UV/Vis absorption spectrophotometry. The ionic strength of the solutions was fixed to = 1, 3, or 5 M by mixing of HNO and HClO. The major palladium species were found to be Pd, PdNO, and Pd(NO). The formation constant of PdNO was determined to be = 1.32 ( = 1 M), 1.49 ( = 3 M), or 1.47 ( = 5 M), while that of Pd(NO) to be = 0.45 ( = 3 M) or 0.14 ( = 5 M).

Burial environment and corrosion of iron sword excavated from Ohtake-nishi archaeological site in Yao City, Osaka Prefecture

Mitsui, Seiichiro; Fujii, Atsuhiro*; Higuchi, Megumi*; Nishimura, Kosuke*

Nihon Bunkazai Kagakkai Dai-27-Kai Taikai Kenkyu Happyo Yoshishu, p.36 - 37, 2010/06

An ancient iron sword (ca 2,000 year old) excavated from Ohtake-nishi archaeological site in Osaka Prefecture, is one of the oldest cast iron swords in the Kinki region. Because of a good state of preservation, such as the sharply-defined ridge on the surface, we studied relationship between burial environment and corrosion. As environmental conditions, we investigated groundwater chemistry and corrosion rate with iron probe monitor, etc. As for corrosion state, we analyzed corrosion depths with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the Eh and dissolved oxygen level as environmental conditions were very low, and that the maximum corrosion rate (810 mm/y) evaluated from measured corrosion depths was smaller than the probe corrosion rate (510 mm/y) by two orders of magnitude and identified siderite as a corrosion product. The results suggested that the siderite on the surface of the iron sword inhibited corrosion reaction.