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Institution

Japan Atomic Energy Research Institute

Government
About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.
Topics: Neutron, Irradiation, Tokamak, Ion, Polymerization


Papers
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Journal ArticleDOI
TL;DR: In this paper, a new method of global sensitivity analysis of nonlinear models is proposed based on a measure of importance to calculate the fractional contribution of the input parameters to the variance of the model prediction.

1,662 citations

Journal ArticleDOI
11 Jul 2002-Nature
TL;DR: X-ray diffraction and absorption is used to show that LaFe0.05O3, one of the perovskite-based catalysts investigated for catalytic converter applications since the early 1970s, retains its high metal dispersion owing to structural responses to the fluctuations in exhaust-gas composition that occur in state-of-the-art petrol engines.
Abstract: Catalytic converters are widely used to reduce the amounts of nitrogen oxides, carbon monoxide and unburned hydrocarbons in automotive emissions. The catalysts are finely divided precious-metal particles dispersed on a solid support. During vehicle use, the converter is exposed to heat, which causes the metal particles to agglomerate and grow, and their overall surface area to decrease. As a result, catalyst activity deteriorates. The problem has been exacerbated in recent years by the trend to install catalytic converters closer to the engine, which ensures immediate activation of the catalyst on engine start-up, but also places demanding requirements on the catalyst's heat resistance. Conventional catalyst systems thus incorporate a sufficient excess of precious metal to guarantee continuous catalytic activity for vehicle use over 50,000 miles (80,000 km). Here we use X-ray diffraction and absorption to show that LaFe0.57Co0.38Pd0.05O3, one of the perovskite-based catalysts investigated1,2,3,4 for catalytic converter applications since the early 1970s, retains its high metal dispersion owing to structural responses to the fluctuations in exhaust-gas composition that occur in state-of-the-art petrol engines5. We find that as the catalyst is cycled between oxidative and reductive atmospheres typically encountered in exhaust gas, palladium (Pd) reversibly moves into and out of the perovskite lattice. This movement appears to suppress the growth of metallic Pd particles, and hence explains the retention of high catalyst activity during long-term use and ageing.

971 citations

Journal ArticleDOI
TL;DR: In this article, an efficient simulation approach under constant external stress and temperature, modifying Parrinello-Rahman (PR) method using useful sampling techniques developed recently, such as massive Nos\'e-Hoover chain method and hybrid Monte Carlo method, was proposed.
Abstract: Molecular simulations, when they are used to understand properties characterizing the mechanical strength of solid materials, such as stress-strain relation or Born stability criterion, by using elastic constants, are sometimes seriously time consuming. In order to resolve this problem, we propose an efficient simulation approach under constant external stress and temperature, modifying Parrinello-Rahman (PR) method using useful sampling techniques developed recently---massive Nos\'e-Hoover chain method and hybrid Monte Carlo method. Test calculations on the Ni crystal employing the embedded atom method have shown that our method greatly improved the efficiency in sampling the elastic properties compared with the conventional PR method.

940 citations

Journal ArticleDOI
25 Aug 2005-Nature
TL;DR: Experimental evidence for ferroelectricity arising from electron correlations in the triangular mixed valence oxide, LuFe2O4 is reported, and resonant X-ray scattering measurements are used to determine the ordering of the Fe2+ and Fe3+ ions.
Abstract: Ferroelectric materials have a spontaneous electric polarization and are widely used in electronic devices including memories. Conventional ferroelectricity arises from ionic displacement, but an alternative mechanism has been proposed based on ordered electrons. Evidence for the latter behaviour has now been found in a mixed valence oxide. This type of ferroelectricity may offer potential for devices with enhanced controllability. Ferroelectric materials are widely used in modern electric devices such as memory elements, filtering devices and high-performance insulators. Ferroelectric crystals have a spontaneous electric polarization arising from the coherent arrangement of electric dipoles1 (specifically, a polar displacement of anions and cations). First-principles calculations2,3 and electron density analysis4 of ferroelectric materials have revealed that the covalent bond between the anions and cations, or the orbital hybridization of electrons on both ions, plays a key role in establishing the dipolar arrangement. However, an alternative model—electronic ferroelectricity5—has been proposed in which the electric dipole depends on electron correlations, rather than the covalency. This would offer the attractive possibility of ferroelectric materials that could be controlled by the charge, spin and orbital degrees of freedom of the electron. Here we report experimental evidence for ferroelectricity arising from electron correlations in the triangular mixed valence oxide, LuFe2O4. Using resonant X-ray scattering measurements, we determine the ordering of the Fe2+ and Fe3+ ions. They form a superstructure that supports an electric polarization consisting of distributed electrons of polar symmetry. The polar ordering arises from the repulsive property of electrons—electron correlations—acting on a frustrated geometry.

842 citations

Journal ArticleDOI
13 Jan 2000-Nature
TL;DR: An in situ X-ray diffraction observation of a liquid–liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms, strongly suggestive of a first-order liquid– liquid phase transition.
Abstract: First-order structural phase transitions are common in crystalline solids, whereas first-order liquid-liquid phase transitions (that is, transitions between two distinct liquid forms with different density and entropy) are exceedingly rare in pure substances But recent theoretical and experimental studies have shown evidence for such a transition in several materials, including supercooled water and liquid carbon Here we report an in situ X-ray diffraction observation of a liquid-liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms In addition to a known form of liquid phosphorus--a molecular liquid comprising tetrahedral P4 molecules--we have found a polymeric form at pressures above 1 GPa Changing the pressure results in a reversible transformation from the low-pressure molecular form into the high-pressure polymeric form The transformation is sharp and rapid, occurring within a few minutes over a pressure range of less than 002 GPa During the transformation, the two forms of liquid coexist These features are strongly suggestive of a first-order liquid-liquid phase transition

719 citations


Authors

Showing all 7708 results

NameH-indexPapersCitations
William F. DeGrado11059943508
David J. Hill107136457746
Makoto Fujita9845136732
Yuliang Zhao9353830249
Yi Luo8166830958
Timothy J. White7246620574
Takeji Hashimoto7143117381
Toshiki Tajima6862722528
Hajime Akimoto6738516568
Andreas Schadschneider6635820856
Tomoyuki Takahashi6418717199
Hiroshi Nishihara6261614683
Hirofumi Uchimiya6223311496
A. Loarte6139514856
Masahide Asano6015912332
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20222
20211
20201
20192
20181
20174