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77 results on '"Akoshima, Megumi"'

73. Research and development of metrological standards for thermophysical properties of solids in the National Metrology Institute of Japan.

Author

BABA, TETSUYA, YAMADA, NAOFUMI, TAKETOSHI, NAOYUKI, WATANABE, HIROMICHI, AKOSHIMA, MEGUMI, YAGI, TAKASHI, ABE, HARUKA, and YAMASHITA, YUICHIRO

Subjects
THERMOPHYSICAL properties, GLASS transition temperature, METROLOGY, STANDARDIZATION, RESEARCH institutes
Abstract

As the national metrology institute representing Japan, the mission of the National Metrology Institute of Japan (NMIJ) is establishment of the national standards and reference materials. Research for thermophysical properties of solid is mainly performed by the thermophysical properties section in the material properties and metrological statistics division of NMIJ. Mission of the thermophysical properties section is to establish the national standard, the reference materials and the traceability for thermophysical property measurements from the view point of industrial, regulatory, and global needs. Reliable measurement methods, metrological standards, document standards such as ISO standards and Japanese industrial standards (JIS) have been developed for thermal conductivity, specific heat capacity, a thermal diffusivity, a thermal effusivity relating in transfer and storage of thermal energy and thermal expansion coefficient to express in temperature change of dimension of materials. The thermophysical properties section is also engaged in development of novel measurement technologies, such as a hybrid pulse heating method in order to measure multi properties simultaneously up to melting point of metals in faster than one second and pulsed light heating thermoreflectance methods in order to measure thermophysical properties of thin films. [ABSTRACT FROM AUTHOR]

Published
2010

74. μ+SR Study on Bi2Sr2Ca1− xY x(Cu1− yZn y)2O8+δ around the Hole Concentration of $$\frac{1} {8} $$ per Cu.

Author

Watanabe, Isao, Akoshima, Megumi, Koike, Yoji, Ohira, Seiko, and Nagamine, Kanetada

Abstract

In order to study the “ $$\frac{1}{8}$$ effect” in different high-Tc oxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi2 Sr2 Ca1− x Yx (Cu1− y Zny )2 O8+δ , around the hole concentration p= $$\frac{1}{8}$$ per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at $$p \sim \frac{1}{8}$$ per Cu, proving the existence of the “ $$\frac{1}{8}$$ effect" in the Bi-2212 system as well. [ABSTRACT FROM AUTHOR]

Published
1999
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75. Exploring Advantages of Diverse Carbon Nanotube Forests with Tailored Structures Synthesized by Supergrowth from Engineered Catalysts

Author

Zhao, Bin, Futaba, Don N., Yasuda, Satoshi, Akoshima, Megumi, Yamada, Takeo, and Hata, Kenji

Abstract

We explored advantages of diverse carbon nanotube forests with tailored structures synthesized by water-assisted chemical vapor deposition (CVD) growth (supergrowth) from engineered catalysts. By controlling the catalyst film thickness, we synthesized carbon nanotube (CNT) forests composed from nanotubes with different size and wall number. With extensive characterizations, many interesting dependencies among CNT forest structures and their properties, which were unknown previously, were found. For example, multiwalled carbon nanotubes (MWNTs) showed superior electronic conductivity while single-walled carbon nanotubes (SWNTs) showed superior thermal diffusivity, and sparse MWNTs achieved lower threshold voltage for field emission than dense SWNTs. These interesting trends highlight the complexity in designing and choosing the optimum CNT forest for use in applications.

Published
2009
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76. μ+SR Study on Bi2Sr2Ca1−xYx(Cu1−yZny)2O8+δaround the Hole Concentration of $$\frac{1} {8} $$ per Cu

Author

Watanabe, Isao, Akoshima, Megumi, Koike, Yoji, Ohira, Seiko, and Nagamine, Kanetada

Abstract

In order to study the “ $$\frac{1}{8}$$ effect” in different high-Tcoxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi2Sr2Ca1−xYx(Cu1−yZny)2O8+δ, around the hole concentration p= $$\frac{1}{8}$$ per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at $$p \sim \frac{1}{8}$$ per Cu, proving the existence of the “ $$\frac{1}{8}$$ effect" in the Bi-2212 system as well.

Published
1999
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