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Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:65 Percentile:0.09(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Manufacturing technology and material properties of high nitrogen austenitic stainless steel forgings for ITER TF coil cases

Oshikawa, Takumi*; Funakoshi, Yoshihiko*; Imaoka, Hiroshi*; Yoshikawa, Kohei*; Maari, Yasutaka*; Iguchi, Masahide; Sakurai, Takeru; Nakahira, Masataka; Koizumi, Norikiyo; Nakajima, Hideo

Proceedings of 19th International Forgemasters Meeting (IFM 2014), p.254 - 259, 2014/09

ITER is a large-scale experiment that aims to demonstrate that it is possible to produce commercial energy from fusion. ITER Toroidal Field Coil Case (hereinafter referred to as "ITER TFCC") is one of the important components of ITER. The ITER TFCC materials are made of high nitrogen austenitic stainless steel and having various configurations. The ITER TFCC material which manufactured by JCFC has a complex configuration with heaver thickness than other materials. It is difficult to form near net shape to delivery configuration by ordinary open die forging method such as upset and stretching, because the ITER TFCC materials manufactured by JCFC have a complex configuration. Therefore ingot weight and lead time of machining increase when ITER TFCC materials are forged by ordinary open die forging method. Moreover, in order to get good attenuation at Ultrasonic examination, it is necessarily to make fine and uniform grain of the material. However, it is impossible to control grain size of austenitic stainless steel by heat treatment. The grain becomes fine and uniform by only forging process with suitable condition. Therefore, JCFC has studied suitable forging method to become near net shape to delivery configuration and also to get fine grain of center of the material. Based on these result, ITER TFCC materials were manufactured. This innovative forging process led to reduce the weight of ingot compared with general forging. And it had good Ultrasonic attenuation. It was confirmed that the results of material test and nondestructive examination satisfied the requirements of Japan domestic agency (hereinafter referred to as "JADA"). Moreover, the test coupons were taken from center of thick part of product and used for various tests. As the result of tests, it was confirmed that results of material test satisfied the requirements of JADA. It is clear that this innovative forging method is very suitable process for manufacturing of ITER TFCC materials.

Journal Articles

Role of cerium oxide in the enhancement of activity for the oxygen reduction reaction at Pt-CeO$$_{x}$$ nanocomposite electrocatalyst; An in situ electrochemical X-ray absorption fine structure study

Masuda, Takuya*; Fukumitsu, Hitoshi*; Fugane, Keisuke*; Togasaki, Hirotaka*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Yoshikawa, Hideki*; Kobayashi, Keisuke*; Mori, Toshiyuki*; et al.

Journal of Physical Chemistry C, 116(18), p.10098 - 10102, 2012/05

 Times Cited Count:87 Percentile:5.99(Chemistry, Physical)

In situ electrochemical X-ray absorption fine structure (XAFS) measurements were performed at the Pt L$$_{3}$$ and Ce L$$_{3}$$ edges of the Pt-CeO$$_{x}$$/C catalyst, which was prepared by a combined process of precipitation and coimpregnation methods, as well as at the Pt L$$_{3}$$ edge of the conventional Pt/C catalyst in oxygen-saturated H$$_{2}$$SO$$_{4}$$ solution to clarify the role of CeO$$_{x}$$ in the reduction of the overpotential for the oxygen reduction reaction (ORR) at the Pt-CeO$$_{x}$$ nanocomposite compared with the conventional Pt/C catalyst. XAFS measurements clearly show that the enhancement of ORR activity is attributed to the inhibition of Pt oxide formation by the CeO$$_{x}$$ layer, of which Ce$$^{3+}$$ was oxidized to Ce$$^{4+}$$ instead of Pt at the Pt oxide formation potential.

Journal Articles

Mass production and quality control of Nb$$_3$$Sn superconducting strands for ITER toroidal field coils

Nabara, Yoshihiro; Nunoya, Yoshihiko; Isono, Takaaki; Hamada, Kazuya; Uno, Yasuhiro; Takahashi, Yoshikazu; Nakajima, Hideo; Tsuzuku, Seiji*; Tagawa, Kohei*; Miyashita, Katsumi*; et al.

Teion Kogaku, 47(3), p.140 - 146, 2012/03

no abstracts in English

Oral presentation

Development of fuel design system for BWR composed of open computer code, 3

Yoshikawa, Takamichi*; Iwasaki, Tomohiko*; Endo, Hideki*; Suyama, Kenya; Shikoda, Keiji*; Yamada, Kohei*; Hamahata, Yoshiki*; Oeda, Shin*

no journal, , 

In order to develop a fuel design system of BWR based on opened calculation codes, a burnup code system SWAT2 using continuous energy Mote Carlo code was revised to include a function of branch calculation. A tool to evaluate lattice constants used in calculation code adopting modern nodal method was also developed and validated by comparison with CASMO.

Oral presentation

Effect of electrochemical pre-treatment and interface structure between Pt and CeO$$_{x}$$ for improvement of oxygen reduction reaction activity on Pt-CeO$$_{x}$$ model electro catalysis

Fugane, Keisuke*; Mori, Toshiyuki*; Wu, Y. Y.*; Yamamoto, Shunya; Maekawa, Yasunari; Yoshikawa, Hideki*; Yamashita, Yoshiyuki*; Ueda, Shigenori*; Vladimir, M.*; Suzuki, Akira*; et al.

no journal, , 

no abstracts in English

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