Kato, Tetsu*; Kawamura, Yamato*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa; Fujii, Shun*
International Journal of Offshore and Polar Engineering, 31(3), p.316 - 324, 2021/09
The development of a side thruster system (vehicle (ASV)) that can maintain the direction of travel on the autonomous surface will be explained. Currently, we are working on a mud radioactivity survey in collaboration with Japan Agency for Marine-Earth Science and Technology, Japan Atomic Energy Agency, and Tokyo University of Marine Science and Technology. Deposited at the mouth of Fukushima Prefecture, Japan, the main purpose is to collect unmanned mud using ASV. The Mad Collection has developed a side thruster system and implemented it in ASV. We have confirmed the operation of the ASV with the joystick by using the thruster system for operating the ASV by one person using the joystick.
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.
Nagai, Takayuki; Okamoto, Yoshihiro; Akiyama, Daisuke*; Uehara, Akihiro*; Fujii, Toshiyuki*; Sekimoto, Shun*
KURNS Progress Report 2019, P. 257, 2020/08
To understand the influence of glass structural change by neutron irradiation and boron isotope composition, glass samples were made from enrichment boric acid reagents and neutron irradiation of those samples was carried out in Pn-2 of KUR. The structural change of glass sample after the irradiation will be estimated in 2020FY. Before neutron irradiation test of glass samples, the Si-O bridging structure difference by boron isotope composition compared by using a Raman spectrometry.
Nagai, Takayuki; Kobayashi, Hidekazu; Okamoto, Yoshihiro; Akiyama, Daisuke*; Sato, Nobuaki*; Uehara, Akihiro*; Fujii, Toshiyuki*; Sekimoto, Shun*
KURNS Progress Report 2018, P. 105, 2019/08
To understand this structural change of a borosilicate glass by a neutron irradiation in detail, the irradiation test was carried out in KUR in 2017FY. The glass structure was estimated by using Raman spectrometry in 2018FY. Comparing with the Raman spectra of glass samples before and after irradiation, it could be observed the change of peak height of Si-O bridging structure by the irradiation.
Nakamura, Toshihiro*; Adachi, Sadao*; Fujii, Minoru*; Sugimoto, Hiroshi*; Miura, Kenta*; Yamamoto, Shunya
Physical Review B, 91(16), p.165424_1 - 165424_8, 2015/04
Semiconductor nanocrystals have unique electrical and optical properties, because of the quantum confinement effect, and the doping of impurities into nanocrystals. In this study, we investigated the photoluminescence (PL) properties of phosphorus- (P) and boron- (B) co-doped Si nanocrystals (Si NCs), which was synthesized using an ion implantation technique. The Si-NC size (average diameter: 3.5, 4.4, 5.2 nm) and the P and B ion doses (0.1-4.510 cm)values were systematically varied. We find that the PL peak energy shifts to lower values with increasing the average diameters of Si NCs and PB ion dose. The results of PL measurements indicate that the PL spectra are due to the band-to-band transition at the reduced Si-NC band gap caused by the formation of impurity and the radiative transitions between defect- and/or impurity-related localized states. It was found that the PL properties can be controlled by varying the Si-NC size as well as the dopant concentration.
Nakagawa, Masahiro; Nojima, Shun; Fujii, Katsutoshi; Shishido, Nobuhito; Sakai, Toshiya; Umehara, Takashi; Shimizu, Isamu
Hoken Butsuri, 47(3), p.189 - 193, 2012/10
It is essential to wear an air-purifying respirator in the radiation works in a contaminated atmosphere. A breath-responsive-powered air-purifying respirator (BR-PAPR) has been recently developed. However, no research has yet been conducted to determine the protection factor (PF) of the BR-PAPR in actual workplaces. In this study, the PFs of the BR-PAPR were measured by a man-test apparatus and compared with those of a non-powered full face mask. The PFs were measured under three different situations; normal wearing condition, clogging the filter and leaving a gap between the face and the mask. Under these situations, it was found that the PFs of the BR-PAPR are higher than those of the non-powered full face mask. PFs greater than 4000 were obtained for 95% of the subjects who wear the BR-PAPR, and PFs over 6667, the upper limit of the man-test apparatus, were obtained for 49% of them. The questionnaire survey was conducted for workers. The results showed that the workers feel a reduced burden when they wear the BR-PAPR. The results of this study showed high protection performance and operation efficiency of the BR-PAPR.
Nakamura, Toshihiro*; Adachi, Sadao*; Fujii, Minoru*; Miura, Kenta*; Yamamoto, Shunya
Physical Review B, 85(4), p.045441_1 - 045441_7, 2012/01
Silicon nanocrystals (Si-nc's) such as nanometer-sized Si dots embedded in a SiO matrix and porous Si have been intensively investigated because of their interesting photoluminescence (PL) properties. Si-nc's exhibit strong and visible emission at room temperature. Because of their compatibility with Si-based technology, light-emitting Si-nc's are an attractive candidate for materials used in various optoelectronic device applications. In this study, the PL properties of n- and p-type dopants phosphorus (P) and boron (B) co-doped Si-nc's prepared by the ion implantation were studied. For (P, B) co-doped Si-nc's, the donor-acceptor (D-A)-pair recombination emission was clearly observed on the long-wavelength side of the intrinsic Si-nc emission. The D-A-pair recombination energy is found to be smaller than the band-gap energy of bulk Si and is strongly dependent on the number of P and B impurities doped in a Si-nc's.
Osaka, Masahiko; Konashi, Kenji*; Hayashi, Hirokazu; Li, D.*; Homma, Yoshiya*; Yamamura, Tomoo*; Sato, Isamu; Miwa, Shuhei; Sekimoto, Shun*; Kubota, Takumi*; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Summer schools for future experts have successfully been completed under Japan Actinide Network (J-ACTINET) for the purpose of development of human resources who are expected to be engaged in every areas of actinide-research/engineering. The first summer school was held in Ibaraki-area in August 2009, followed by the second one in Kansai-area in August 2010. Two summer schools have focused on actual experiences of actinides in actinide-research fields for university students and young researchers/engineers as an introductory course of actinide-researches. Several quasi actinide-handling experiences at the actinide-research fields have attracted attentions of participants at the first school in Ibaraki-area. The actual experiments using actinides-containing solutions have been carried out at the second school in Kansai-area. Future summer schools will be held every year for the sustainable human resource development in various actinide-research fields.
Fujii, Toshiyuki*; Okude, Genki*; Uehara, Akihiro*; Sekimoto, Shun*; Hayashi, Hirokazu; Akabori, Mitsuo; Minato, Kazuo; Yamana, Hajimu*
Journal of Radioanalytical and Nuclear Chemistry, 288(1), p.181 - 187, 2011/04
Distribution behavior of Ce(III), Am(III), and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO)HO or molten calcium chloride hydrate CaClHO was studied radiochemically. In Ca(NO)HO systems, maximum separation factors of Ce and Cm to Am were observed to be 12 (Ce/Am) and 1.7 (Cm/Am). The distribution ratios of these elements increased with the decrease of water activity in the hydrates, and the extractabilities at the water deficient region was less sensitive compared to those at the water abundant region. This trend was similar to the coordination circumstance change observed in electronic absorption spectra of Nd(III) in the hydrates.
Saeki, Morihisa; Ishiuchi, Shunichi*; Sakai, Makoto*; Hashimoto, Kenro*; Fujii, Masaaki*
Journal of Physical Chemistry A, 114(42), p.11210 - 11215, 2010/10
Okude, Genki*; Fujii, Toshiyuki*; Uehara, Akihiro*; Sekimoto, Shun*; Minato, Kazuo; Yamana, Hajimu*
IOP Conference Series; Materials Science and Engineering, 9, p.012067_1 - 012067_7, 2010/05
Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.
Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12
no abstracts in English
Hoshino, Katsumichi; Suzuki, Takahiro; Isayama, Akihiko; Ide, Shunsuke; Takenaga, Hidenobu; Kubo, Hirotaka; Fujita, Takaaki; Kamada, Yutaka; Fujii, Tsuneyuki; Tsuda, Takashi; et al.
Fusion Science and Technology, 53(1), p.114 - 129, 2008/01
We report on the applications of the ECH to the JT-60U tokamak. The ECH contributes to the advanced tokamak study in JT-60U in such respects as (1)NTM suppression, (2)Study on the internal transport barrier, (3)Impurity exhaust, (4)Tokamak start-up without center solenoid, (5)Current hole study, (6)Confinement and transport study, and (7)Start-up and shut-down assist. These contributions comes from the good local coupling of the ECH to the tokamak plasma.
Saeki, Morihisa; Ishiuchi, Shunichi*; Sakai, Makoto*; Fujii, Masaaki*
Journal of Physical Chemistry A, 111(6), p.1001 - 1005, 2007/02
The structure of a jet-cooled 1-naphthol (1-NpOH) dimer was investigated by using resonant-enhanced two-photon ionization (R2PI) and ion-detected infrared (IR) dip spectroscopy. A geometrical optimization and a frequency calculation in (1-NpOH) were also performed at the MP2/cc-pVDZ level. Stable isomers in the MP2/cc-pVDZ calculation were classified into a structure dominated only by the - interaction and structures formed by cooperation between the - interaction and hydrogen bonding. On the basis of a comparison between the observed and calculated IR spectra, the geometry of (1-NpOH) was concluded to be a - stacking structure supported by hydrogen bonding.
Tsuruga, Kayoko; Kasahara, Junzo; Mikada, Hitoshi*; Yamaoka, Koshun; Fujii, Naoyuki
Chigaku Zasshi, 115(1), p.51 - 71, 2006/02
This paper proposes the idea (Exploration of Asperities-Reflectors System, EARS) for getting to know the occurrence of large - huge earthquakes which take place along a subduction plate boundary. A large earthquake along the subducting plate boundary is considered to occur repeatedly in the particular asperity, which is the region of strongly coupled zone of two plates. The regions other than asperities along the plate boundary are considered as stable - quasi-stable region in which slow-slip may release the strain energy caused by the oceanic plate subduction. The intensity of coupling and the heterogeneities in a particular large asperity is not possible to know at present. The strong seismic reflections from the subducting plate boundary were found in the aseismic forearc region in the Japan Trench. Similar strong PP reflections were also observed in the NE region of the Hamana Lake and the same region has also showed large aseismic slip detected by GPS. When we map the asperities-reflectors system, the continuous monitoring of seismic reflection intensity may give the change of the physical state at the subducting plate boundary. The rapid change may trigger a large earthquake at an adjacent asperity. We introduce the innovative measurement system, ACROSS, which has been developed for active monitoring by continuous sinusoidal elastic waves and also describe the recent submarine OBS system. To obtain real-time monitor of the transmission signals from ACROSS at the potential regions near the trenches can be done by use of submarine cables. A newly built system planned in the Tonankaki region should consider this requirement.
Moriyama, Shinichi; Seki, Masami; Terakado, Masayuki; Shimono, Mitsugu; Ide, Shunsuke; Isayama, Akihiko; Suzuki, Takahiro; Fujii, Tsuneyuki; JT-60 Team
Fusion Engineering and Design, 74(1-4), p.343 - 349, 2005/11
no abstracts in English
Suzuki, Takahiro; Isayama, Akihiko; Sakamoto, Yoshiteru; Ide, Shunsuke; Fujita, Takaaki; Takenaga, Hidenobu; Luce, T. C.*; Wade, M. R.*; Oikawa, Toshihiro; Naito, Osamu; et al.
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
no abstracts in English
Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.
Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02
The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.
Kasahara, Junzo; Tsuruga, Kayoko; Hasada, Yoko; Yamaoka, Koshun; Kunitomo, Takahiro; Watanabe, Toshiki; Fujii, Naoyuki
2004 AGU Fall Meeting Program and Abstract, S31C-07, 0 Pages, 2004/00
Recently, a very strong reflected PP phase from the subducting plate boundary was found beneath the aseismic forearc slope of the Japan Trench. Similar strong PP reflection phase was observed near the plate boundary of the subducting Philippine Sea Plate and the Eurasian Plate, in the western part of Shizuoka Prefecture. These strong PP reflections are interpreted as reflections from the non-asperity region along the plate boundary caused by the presence of low-Vp material. Using continuous transmission of seismic waves from the ACROSS source located and /or the new ACROSS source under planning and the high sensitivity seismometers along the NS traverse line, we can delineate the temporal variation of seismic wave properties of the anomalously reflected PP phase along the boundary of subducting Philippine Sea Plate.
Moriyama, Shinichi; Ikeda, Yoshitaka; Seki, Masami; Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken*; Isayama, Akihiko; Suzuki, Takahiro; Fukuda, Takeshi*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 79(9), p.935 - 944, 2003/09
An optimization of current profile is a key issue for attaining higher plasma performance in Tokamak, such as stabilization of neo-classical tearing mode (NTM) and control of internal transport barrier (ITB). In JT-60U, a high power electron cyclotron heating (ECH) system at 110 GHz has been developed for local plasma heating and current drive. We have demonstrated the technical feasibility of the antenna which can scan EC beam in both toroidal and poloidal directions. The toroidal scan enabled co- and counter- current drive and also pure plasma heating. An automatic stabilization of the NTM was demonstrated by means of current drive at the location of magnetic island using a feedback control of poloidal beam angle. The total injected power has been extended to 2.8 MW for 3.6 sec and each gyrotron delivers ~ 1 MW for 5 sec. This world record of the injection energy was attained by an upgrade of the gyrotron using RF absorber in the beam tunnel to suppress the parasitic oscillation and improvement of the transmission efficiency of the waveguide system.