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Ueda, Yoshio*; Oya, Kaoru*; Ashikawa, Naoko*; Ito, Atsushi*; Ono, Tadayoshi*; Kato, Daiji*; Kawashima, Hisato; Kawamura, Gakushi*; Kenmotsu, Takahiro*; Saito, Seiki*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 88(9), p.484 - 502, 2012/09
no abstracts in English
Asakura, Nobuyuki; Ashikawa, Naoko*; Ueda, Yoshio*; Ono, Noriyasu*; Tanabe, Tetsuo*; Nakano, Tomohide; Masuzaki, Suguru*; Itami, Kiyoshi; Kawano, Yasunori; Kawahata, Kazuo*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 87(7), p.485 - 486, 2011/07
no abstracts in English
Ishida, Michihiko; Hayashi, Yoshiaki*; Ueda, Yoshinori*; Yoshida, Kazuo
Nihon Genshiryoku Gakkai Wabun Rombunshi, 9(1), p.71 - 81, 2010/03
A special committee of "Research on the analysis methods for accident consequence of nuclear fuel cycle facilities (NFCF)" was organized by the Atomic Energy Society of Japan (AESJ) under the entrustment of Japan Atomic Energy Agency (JAEA) for a research on the state-of-the-art of consequence analysis method for Probabilistic Safety Assessment (PSA) of NFCF such as fuel reprocessing and fuel fabrication facilities. The objectives of this research is to obtain the basic useful information related for establishing the quantitative performance requirement and for risk-informed regulation through qualifying issues needed to be resolved for applying PSA to NFCF. In this technical report, it was summarized that the research result about basic experimental data related to the consequence of the radiolytically generated hydrogen gas explosion postulated in the radioactive solution reserve tank caused by the loss of dilution air supply.
Idomura, Yasuhiro; Yoshida, Maiko; Yagi, Masatoshi*; Tanaka, Kenji*; Hayashi, Nobuhiko; Sakamoto, Yoshiteru; Tamura, Naoki*; Oyama, Naoyuki; Urano, Hajime; Aiba, Nobuyuki; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 84(12), p.952 - 955, 2008/12
no abstracts in English
Maehira, Takahiro*; Hotta, Takashi; Ueda, Kazuo*; Hasegawa, Akira*
New Journal of Physics (Internet), 8(2), p.24_1 - 24_20, 2006/02
Times Cited Count:16 Percentile:64.23(Physics, Multidisciplinary)By using a relativistic band-structrue calculation method, we investigate energy band structures and the Fermi surfaces of NpTGa, PuTGa
, and AmCoGa
with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between
and Ga
electrons. For PuTGa
, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. It is also found that the Fermi surfaces of NpFeGa
, NpCoGa
, and NpNiGa
are similar to those of UCoGa
, UNiGa
, and PuCoGa
, respectively, except for small details. For AmCoGa
, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa
. The similarity is basically understood by a rigid-band picture.
Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*
Physical Review B, 69(10), p.104504_1 - 104504_9, 2004/03
Times Cited Count:163 Percentile:97.05(Materials Science, Multidisciplinary)In order to discuss superconductivity in orbital degenerate systems, a microscopic Hamiltonian is introduced. Based on the degenerate model, a strong-coupling theory of superconductivity is developed within the fluctuation exchange (FLEX) approximation where spin and orbital fluctuations, spectra of electron, and superconducting gap function are self-consistently determined. Applying the FLEX approximation to the orbital degenerate model, it is shown that the -wave superconducting phase is induced by increasing the orbital splitting energy which leads to the development and suppression of the spin and orbital fluctuations, respectively. It is proposed that the orbital splitting energy is a controlling parameter changing from the paramagnetic to the antiferromagnetic phase with the
-wave superconducting phase in between.
Hotta, Takashi; Ueda, Kazuo*
Physical Review Letters, 92(10), p.107007_1 - 107007_4, 2004/03
Times Cited Count:13 Percentile:59.02(Physics, Multidisciplinary)We discuss microscopic aspects of odd-parity triplet pair in orbital degenerate systems. From the concept of off-diagonal long-range order, a pair state is unambiguously defined as the eigenstate with the maximum eigenvalue of pair correlation function. Performing this scheme by a numerical technique, we clarify that the odd-parity triplet pair occurs as an out-of-phase combination of local triplets induced by Hund's rule coupling for the lattice including two sites in the unit cell.
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
Times Cited Count:2 Percentile:6.38(Physics, Fluids & Plasmas)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.
Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*
Journal of Physics; Condensed Matter, 15(28), p.S2087 - S2093, 2003/07
Times Cited Count:14 Percentile:57.26(Physics, Condensed Matter)Rich physics is expected to appear due to the coupling between orbital and spin degrees of freedom in strongly correlated electron system with orbital degeneracy. Especially, it is considered that the superconducting transition in orbital degenerate system is one of the most interesting phenomena. For instance, triplet superconductivity occurs in SrRuO
where three cylindrical Fermi surfaces are observed. Also, heavy fermion superconductors are considered to have potentially orbital degree of freedom due to large degeneracy of
-electron states. We discuss the effect of orbital fluctuations on superconductivity by using random phase approximation and fluctuation exchange (FLEX) approximation. It is also expected that the FLEX approximation is useful to study the correlation between spin and orbital fluctuations for the orbital degenerate system.
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
no abstracts in English
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
Times Cited Count:33 Percentile:68.27(Physics, Fluids & Plasmas)no abstracts in English
Maehira, Takahiro; Hotta, Takashi; Ueda, Kazuo; Hasegawa, Akira*
Physical Review Letters, 90(20), p.207007_1 - 207007_4, 2003/05
Times Cited Count:94 Percentile:92.17(Physics, Multidisciplinary)By using a relativistic linear augmented-plane-wave method, we clarify energy band structures and Fermi surfaces of recently discovered plutonium-based superconductor PuCoGa. We find several cylindrical sheets of Fermi surfaces with large volume, quite similar to CeMIn
(M=Ir and Co) isostructural with PuCoGa
, in spite of different
-electron numbers between Ce
and Pu
ions. This similarity is simply understood by a concept of electron-hole conversion in a tight binding model constructed based on the
-
coupling scheme. Due to the present results, we provide a possible scenario to explain why a transition temperature is so high as 18.5K in PuCoGa
.
Maehira, Takahiro; Hotta, Takashi; Ueda, Kazuo; Hasegawa, Akira*
Journal of the Physical Society of Japan, 72(4), p.854 - 864, 2003/04
Times Cited Count:75 Percentile:89.97(Physics, Multidisciplinary)In order to investigate electronic properties of recently discovered heavy fermion superconductors CeTIn (T=Ir and Co), we employ the relativistic linear augmented-plane-wave (RLAPW) method to clarify the energy band structures and Fermi surfaces of those materials.The obtained energy bands mainly due to the large hybridization between Ce
and In 5
states well reproduce the Fermi surfaces consistent with the de Haas-van Alphen experimental results. For the purpose, we construct a tight-binding model for CeTIn
by including
-
and
-
hoppings as well as
-
hybridization, which are expressed by the Slater-Koster integrals, determined by the direct comparison with the band-calculation result. Similarity and difference between CeIrIn
and CeCoIn
are discussed based on the obtained tight-binding model, suggesting a significant importance of the effect of crystalline electric field to understand the difference in electronic properties among CeTIn
.
Hotta, Takashi; Ueda, Kazuo
Physical Review B, 67(10), p.104518_1 - 104518_16, 2003/03
Times Cited Count:88 Percentile:93.16(Materials Science, Multidisciplinary)We construct a microscopic model for -electron systems, composed of
-electron hopping, Coulomb interaction, and crystalline electric field terms. based on the
-
coupling scheme. The Hamiltonian obtained is regarded as an orbital degenerate Hubbard model, since it includes two pseudo-spin and three pseudo-orbital degrees of freedom. For practical purposes, it is further simplified into a couple of two-orbital models by discarding one of the three orbitals. One of those simplified models is here analyzed using the exact diagonalization method to clarify ground-state properties by evaluating several kinds of correlation functions. We attempt to discuss a possible relation of the present results with experimental observations for recently discovered heavy fermion superconductors CeMIn
(M=Ir, Co, and Rh), and a comprehensive scenario to understand superconducting and antiferromagnetic tendencies in the so-called ``115'' materials such as CeMIn
, UMGa
, and PuCoGa
from the microscopic viewpoint.
Ueda, Kazuo; Hotta, Takashi
JAERI-Review 2002-037, 31 Pages, 2002/12
Strongly correlated f- and d-electron systems including heavy Fermion systems and transition metal oxides are important source of exciting new phenomena in condensed matter physics. Recently it has been recognized in more profound way that the orbital degeneracy of the f- and d-electrons plays very important role underlying those exotic phenomena. The idea of the present workshop is to bring active researchers in the field together and to exchange ideas in informal atmosphere. In the workshop many interesting results were presented and stimulating discussions were made as clearly seen by the present report.
Takimoto, Tetsuya; Hotta, Takashi; Maehira, Takahiro; Ueda, Kazuo*
Journal of Physics; Condensed Matter, 14(21), p.L369 - L375, 2002/06
Times Cited Count:56 Percentile:86.21(Physics, Condensed Matter)A microscopic Hamiltonian of the orbitally-degenerated Hubbard model reflecting correct symmetry of -orbitals is proposed to discuss superconductivity in
-electron systems. In the degenerated region, cancellation among spin and orbital fluctuations basically destabilizes singlet superconductivity, while
-wave superconductivity mediated by spin fluctuations emerges out of the suppression of orbital fluctuations due to the lift of orbital degeneracy. We argue that the present scenario can be applied to recently discovered Ce-based heavy-fermion superconductor.
Maehira, Takahiro; Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*; Higuchi, Masahiko*; Hasegawa, Akira*
Journal of the Physical Society of Japan, Vol.71, Supplement, p.285 - 287, 2002/00
Times Cited Count:8 Percentile:49.64(Physics, Multidisciplinary)Recently a new family of Ce-based heavy fermion superconductor (T=Rh, Ir, and Co) has been reported. The dHvA effect has been successfully observed in
and
.The angular dependence of dHvA branches is well explained by a quasi-two dimensional Fermi surface(F.S.). In order to clarify band structures of Ce-115 systems such as CeIrIn
and CeCoGa
, two-step strategy is here employed. In the first step, the F.S. are derived by using the RLAPW method. In the next step, the band structure near the Fermi level is reanalyzed by using a simple tight-binding model. Namely, hopping amplitudes of
-electrons between neighboring Ce ions are parameterized to reproduce the F.S. obtained in the band-calculation. By further adding the Coulomb interaction terms into this tight-binding model, a simple many-body Hamiltonian for Ce-compounds can be constructed. This Hamiltonian opens a way to discuss magnetism and superconductivity in
-electron systems from the microscopic viewpoint.
Saito, Yuji; Kimura, Hiroaki*; Suzuki, Yoshio*; Nakatani, Takeshi*; Matsushita, Tomohiro*; Muro, Takayuki*; Miyahara, Tsuneaki*; Fujisawa, M.*; Soda, Kazuo*; Ueda, Shigenori*; et al.
Nuclear Instruments and Methods in Physics Research A, 467-468(Part.1), p.553 - 556, 2001/07
Times Cited Count:23 Percentile:81.79(Instruments & Instrumentation)no abstracts in English
Saito, Yuji; Kimura, Hiroaki*; Suzuki, Yoshio*; Nakatani, Takeshi*; Matsushita, Tomohiro*; Muro, Takayuki*; Miyahara, Tsuneaki*; Fujisawa, M.*; Soda, Kazuo*; Ueda, Shigenori*; et al.
Review of Scientific Instruments, 71(9), p.3254 - 3259, 2000/09
Times Cited Count:187 Percentile:98.96(Instruments & Instrumentation)no abstracts in English
Ikeda, Norio*; Sasaki, Nobuyuki*; Oshima, Kazuo*; Yamaguchi, Kohei*; Saito, Shigeyuki*; Abe, Yoriyuki*; Katano, Takashi*; Ueda, Akira*
JNC TJ7440 2005-071, 122 Pages, 1998/03
no abstracts in English