Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 72, Issue 12
Displaying 1-50 of 54 articles from this issue
  • Wen-Xiu Ma
    2003 Volume 72 Issue 12 Pages 3017-3019
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A Darboux transformation is furnished for a Schrödinger self-consistent source equation, along with a solution formula. Soliton, positon and negaton solutions to the Schrödinger self-consistent source equation are further constructed. The resulting solutions resemble those of the KdV equation with self-consistent sources, but the space and time variables are involved in a slightly different manner.
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  • Yoshiaki Rikitake, Hiroshi Imamura, Hiromichi Ebisawa
    2003 Volume 72 Issue 12 Pages 3020-3023
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We theoretically study the time evolution of an exciton qubit (quantum dot) and a photon qubit (photonic cavity) coupled with each other. Special attention is paid to the effect of pure dephasing and energy dissipation in the quantum dot. We find that the pure dephasing brings about the oscillation of the entropy of the quantum dot with the half period of Rabi oscillation. Finite entanglement remains in the steady state. This state can be used for preparing the Bell state between photon and exciton qubits. The energy dissipation suppresses the amplitude of the oscillation of the entanglement between the exciton and photon qubits. We also find that the energy dissipation in the quantum dot changes the oscillation period of the entropy of the quantum dot.
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  • Jun-ichi Inoue, Kazuo Ohtaka
    2003 Volume 72 Issue 12 Pages 3024-3027
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A theory of hybridization between a localized mode and free modes in photonics is presented. It is the photonic counterpart of the Anderson model for the s- and d-electrons problem in solid-state physics. The localized mode corresponding to a d-electron is found to be a photon virtual bound state. The photonic density of states analytically obtained from the present theory is compared with numerical results, showing good agreement. The present theory supports the “heavy photon” concept proposed for photonic crystals.
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  • Katsunori Yoshimatsu, Jiro Mizushima
    2003 Volume 72 Issue 12 Pages 3028-3031
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The instability and transition of radially outgoing flow between two parallel disks with two symmetrically attached inlet pipes through which fluid enters are investigated theoretically and experimentally assuming an incompressible and axisymmetric flow field. The flow is steady and symmetric with respect to the center plane between the two disks at small Reynolds numbers, but becomes asymmetric above a critical Reynolds number. Numerical simulations and the linear stability analysis reveal that steady asymmetric flows result from the instability of the steady symmetric flow. The axisymmetry and the transition were confirmed in our experiments with flow visualization.
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  • X. He, X. Y. Li, B. X. Liu
    2003 Volume 72 Issue 12 Pages 3032-3034
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    In the equilibrium-immiscible Cu–Ru system, a metastable crystalline (MC) alloy of face-centered cubic (FCC) structure was formed in the appropriately designed Cu25Ru75 multilayered films upon room-temperature ion beam manipulation using 200 keV xenon ions. More interestingly, an amorphous alloy was obtained in the Cu50Ru50 multilayered films at low irradiation dose and it transformed into the FCC MC alloy upon further irradiation at high dose. We report, in this Letter, experimental observations of the metastable alloy formation and briefly discuss the role of interfacial free energy in the metastable alloy formation observed in the Cu–Ru system.
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  • Hirohiko Sato, Toshiyuki Ogawa, Noriki Okuda, Junichi Wakabayashi
    2003 Volume 72 Issue 12 Pages 3035-3038
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A new phase of ternary ruthenium oxide, Ba2Ru7O18, is discovered. The lattice parameters are: triclinic, a=6.71(4) Å, b=7.10(4) Å, c=7.46(4) Å, α=93.2(2)°, β=94.6(2)°, γ=115.7(2)°. It has a Ba2Zn7F18-type structure composed of an egde-shared and corner-shared network of RuO6 octahedra. The magnetic susceptibility around room temperature exhibits a Pauli paramagnetism with a relatively large value of χ=3.4×10−4 emu/mol at 300 K, while it exhibits a large temperature dependence in the low temperature range without any evidence of magnetic phase transitions down to 2 K. The resistivity at 300 K is 1.1×10−3 Ω cm, larger than that of normal metal. Unlike conventional metals, the resistivity exhibits T1.2-linear dependence in the low temperature region. These anomalous behaviors of magnetism and resistivity can be interpreted in terms of the non-Fermi liquid state.
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  • Melike Abliz, Masato Hedo, Zenji Hiroi, Takehiko Matsumoto, Masafumi H ...
    2003 Volume 72 Issue 12 Pages 3039-3040
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Electrical resistivity measurements of Cd2Re2O7 under pressure and magnetic field have been performed. The two superconducting transitions previously observed under pressure become one under a magnetic field of 0.2 T. The superconductivity transition temperature Tc increases linearly from 1 K to 2.4 K with increasing pressure up to 2.4 GPa in the field. The upper critical field Hc2 observed by measurements of the field dependence of electrical resistivity under pressure increases to about 4T with increasing pressure up to 2.4 GPa. The Grüneisen parameters of Tc, Hc2, and Ts are estimated to be 96, 243, and −32, respectively.
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  • K. Ishida, Y. Ihara, Y. Maeno, C. Michioka, M. Kato, K. Yoshimura, K. ...
    2003 Volume 72 Issue 12 Pages 3041-3044
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Co nuclear-quadrupole-resonance (NQR) studies were performed in the recently discovered superconductor NaxCoO2·yH2O to investigate physical properties in the superconducting (SC) and normal states. Two samples from the same NaxCoO2 were examined, a SC bilayer-hydrate sample with Tc∼4.7 K and a non-SC monolayer-hydrate sample. From the measurement of nuclear-spin lattice relaxation rate 1⁄T1 in the SC sample, it was found that the coherence peak is absent just below Tc and that 1⁄T1 is proportional to temperature far below Tc. These results, which are in qualitative agreement with the previous result by Fujimoto et al., suggest strongly that unconventional superconductivity is realized in this compound. In the normal state, 1⁄T1T of the SC sample shows a gradual increase below 100 K down to Tc, whereas 1⁄T1T of the non-SC sample shows the Korringa behavior in this temperature range. From the comparison between 1⁄T1T and χbulk in the SC sample, the increase in 1⁄T1T is attributed to nearly ferromagnetic fluctuations. These remarkable findings suggest that the SC sample possesses nearly ferromagnetic fluctuations, which are possibly related to the unconventional superconductivity in this compound. The implication of this finding is discussed.
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  • Zenji Hiroi, Kazuyuki Matsuhira, Masao Ogata
    2003 Volume 72 Issue 12 Pages 3045-3048
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A spin-ice compound, dysprosium titanate, Dy2Ti2O7, is studied by specific heat measurements in magnetic fields applied along the [110] direction of the cubic unit cell. Above a magnetic field of 0.4 T, a relatively sharp peak at T=1.1 K in the specific heat appears from a broad peak associated with spin-ice freezing at low fields. This new peak is almost independent of the magnetic field up to 1.5 T, while another broad, field-dependent peak is detected at a higher temperature. Under a magnetic field along [110], Ising spins on the pyrochlore lattice can be considered to form two orthogonal sets of chains, parallel and perpendicular to the field direction. It is suggested that these perpendicular chains behave as unique ferromagnetic Ising spin chains without long-range order, giving rise to the observed field-independent peak.
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  • Zenji Hiroi, Tohru Yamauchi, Yuji Muraoka, Takaki Muramatsu, Jun-Ichi ...
    2003 Volume 72 Issue 12 Pages 3049-3052
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The efficiency of photocarrier injection in a VO2/TiO2:Nb heterostructure is studied by measuring IV characteristics at room temperature under ultraviolet light irradiation. It is revealed that photogenerated hole carriers in the TiO2:Nb substrate are injected and accumulated in the VO2 film by the photovoltaic effect. The surface charge density is controlled successfully in a wide range of 109–1013 cm−2 as a function of light irradiance. The maximum hole density of 9×1018 cm−3 is attained at a light irradiance of 133 mW/cm2, which is estimated by assuming the uniform distribution of holes in the film. It is suggested that high efficiency can be achieved by utilizing the large dielectric constant of titanium oxide substrates.
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  • Masakazu Kunitomo, Rina Etoh, Toshiro Kohmoto, Yukio Fukuda, Masao Has ...
    2003 Volume 72 Issue 12 Pages 3053-3054
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The temperature dependence of proton spin–lattice relaxation rate was measured in a molecular crystal, tribromoacetamide (TBAA). An anomalous narrow peak of the relaxation rate, which may be related to the critical phenomena accompanying phase transition, has been found in the vicinity of phase transition temperatures. Another peak has also been observed, which is an ordinary broad one characteristic of the relaxation caused by the fluctuation of the dipolar interaction.
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  • Ning Wang, Miki Wadati
    2003 Volume 72 Issue 12 Pages 3055-3062
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A geometric description is introduced to consistently define initial and/or boundary value problem, zero curvature representation and monodromy operator for noncommutative (nc, for short) soliton equations. Based on the description, it is shown that many known commutative/noncommutative soliton equations can be obtained in a unified way. The integrability of a nc-NLS equation and a generalized large N-limit of matrix NLS equation is studied; a generalized conservation law for the nc-NLS equation is presented, and the generalized large N-limit of matrix NLS equation is shown to be integrable in the sense that there exist an infinite number of independent conserved quantities in involution.
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  • H. H. Dai, Xianguo Geng
    2003 Volume 72 Issue 12 Pages 3063-3069
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The 2+1-dimensional modified Toda lattice is decomposed into solvable ordinary differential equations with the help of the 1+1-dimensional relativistic Toda lattices. Based on the decomposition and the theory of algebraic curve, the straightening out of various flows, including the continuous flow and discrete flow, is exactly given through the introduced Abel–Jacobi coordinates. The explicit theta function solutions for the 2+1-dimensional modified Toda lattice are obtained explicitly.
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  • K. W. Chow, C. C. Mak
    2003 Volume 72 Issue 12 Pages 3070-3074
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    (2+1) (2 spatial and 1 temporal) dimensional patterns of standing waves are calculated theoretically for the Davey–Stewartson equations (DS). DS are relevant in hydrodynamic free surface waves of finite depth, and constitute a system of evolution equations with rich structure. The Hirota bilinear method, theta and Jacobi elliptic functions are employed. The wave patterns will be periodic in two mutually perpendicular spatial directions. The long wave limit can be taken by letting one of the spatial periods to become large. Special bright or dark solitons will result. The validity of all these solutions is verified independently by direct differentiation with the software MATHEMATICA.
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  • Xing-Biao Hu, Wei-Min Xue
    2003 Volume 72 Issue 12 Pages 3075-3078
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A bilinear Bäcklund transformation (BT) and the associated nonlinear superposition formula are found for the negative Volterra hierarchy. As an application of the obtained results, soliton solutions to the negative Volterra hierarchy are re-derived.
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  • Masaaki Kitaguchi, Haruhiko Funahashi, Terunao Nakura, Kaoru Taketani, ...
    2003 Volume 72 Issue 12 Pages 3079-3081
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We have measured the transverse coherence length of a cold neutron beam using Jamin-type cold neutron spin interferometer. It can control the transverse shift between the superposed two paths with no dispersion. We have observed clearly that the contrast of interference fringes varies according to the coherence function determined by the collimation of the beam. The measured coherence length was consistent with the estimate by the standard deviation of the neutron transverse momentum distribution.
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  • Naoki Seto, Jun’Ichi Yokoyama
    2003 Volume 72 Issue 12 Pages 3082-3086
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We propose a method to probe the equation of state of the early universe and its evolution, using the stochastic gravitational wave background from inflation. A small deviation from purely radiation dominated universe (w=1⁄3) would be clearly imprinted on the gravitational wave spectrum ΩGW(f) due to the nearly scale invariant nature of inflationary generated waves.
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  • Ramendra Nath Majumdar
    2003 Volume 72 Issue 12 Pages 3087-3090
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    In a recent publication, Phys. Rev. C 63 (2001) 65806, experimental datas on the coulomb dissociation cross sections of 8B have been reported. In the present research, a theoretical attempt has been made to explain these results that are based on direct fragmentation model when 8B interacts with 107Ag and 208Pb target nuclei. The symmmetric momentum distribution of the ejected 7Be might be due to outcome of both nuclear and coulomb effect for the dissociation of 8B.
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  • Nengwu Zheng, Jing Fan, Dongxia Ma, Tao Wang
    2003 Volume 72 Issue 12 Pages 3091-3096
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Within the Weakest Bound Electron Potential Model (WBEPM) theory, calculations for energy levels and transition probabilities of singly ionized aluminum (Al II) are performed, and good agreement with experimental or accepted values is obtained. To treat properly the perturbed states, foreign perturbers are taken into account in studying the energy levels, meanwhile, a set of coupled equations is employed to determine the parameters effective nuclear charge Z′, effective principal quantum number n′, and effective angular quantum number l′ needed for the calculation of transition probabilities.
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  • Shigeyuki Aono
    2003 Volume 72 Issue 12 Pages 3097-3105
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The algebra representing electron is spinor. The many electron problem is investigated with the Nambu 2×2 spinor. Operators then are expressed 2×2 matrices. The electron–electron interaction is decomposed into couplings between various electron densities by using the Pauli spin matrices. The diagonal ones of them refer to the direct and exchange interactions and the off-diagonal terms to those for superconducting. The Roothaan theory is rewritten. The approximation beyond the Hartree–Fock is discussed.
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  • Shintaro Kuronuma, Masaki Sano
    2003 Volume 72 Issue 12 Pages 3106-3112
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A tube conveying flow becomes unstable by the flutter instability and exhibits chaotic behavior when the flow rate increases sufficiently high. The dynamics of a hanging tube conveying air flow is investigated with varying the flow rate and the length of the tube. Two different boundary conditions at the hanging end of the tube are applied; one is the rigid end, and the other is axially rotatable. Depending on different boundary conditions, several intriguing dynamics and bifurcation sequences are observed. The dynamic modes of the tube are classified according to their symmetries and power spectra.
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  • Takao Yoshinaga, Takuya Yoshida
    2003 Volume 72 Issue 12 Pages 3113-3122
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We investigate nonlinear wave behavior of a free liquid sheet subject to a temperature difference between both surfaces. Considering the temperature dependence of the surface tension and viscosity, we analytically obtain a nonlinear evolution equation for the sinuous (antisymmetric) mode under the membrane approximation. For infinitesimal disturbances or without temperature difference, the equation is reduced to the linearized K–dV equation in which the mode is neutrally stable. When weak nonlinearity is considered in the equation, however, the mode is modulationally unstable for the temperature difference above a critical value. Numerical analysis on the equation shows that the sheet becomes unstable with steepening and distortion above the critical temperature difference. In particular, for large temperature difference, the bulge (symmetric) mode is additionally induced on the sinuous mode and this induced mode is expected to cause the breakup of the sheet. On the other hand, the temperature dependence of the viscosity affects on the growth rate of the mode due to the instability.
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  • Shin Nakamura, Kenichi Oikawa
    2003 Volume 72 Issue 12 Pages 3123-3127
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We propose the use of Mössbauer quadrupole effect as a sensitive probe to determine structural feature precisely. This method has been applied, together with the high-resolution neutron powder diffraction measurements, to the structure analysis of the ordered double perovskites Sr2FeMoO6 and Sr2FeReO6 at room temperature. Results of Rietveld refinement were verified by the Mössbauer quadrupole effect. We have concluded that the space groups of Sr2FeMO6 (M = Mo and Re) are I4⁄m, but not I4⁄mmm as has been frequently pronounced. The spins of M = Re specimen are aligned in ab-plane, while those of M = Mo specimen are aligned in ab-plane or along c-axis.
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  • Yoshiharu Suzuki, Osamu Mishima
    2003 Volume 72 Issue 12 Pages 3128-3131
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We make three kinds of low density glassy waters, low-density amorphous ice (LDA), amorphous solid water (ASW) and hyperquenched glassy water (HGW), and examine the changes in their Raman spectra of OH-stretching vibrational regions by annealing at 1 bar. The irreversible change in Raman profile for LDA is observed above its calorimetric glass transition temperature (Tg) of ∼130 K below 144 K. The degree of the change in Raman spectra of LDA at the annealing temperature appears to be different from those for ASW and HGW. These results suggest a possibility that the modification in the hydrogen-bonded network of LDA during the annealing occurs above the calorimetric Tg.
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  • Masaru Sugiyama, Kuniaki Goto, Kazunori Takada, Giovanna Valenti, Carm ...
    2003 Volume 72 Issue 12 Pages 3132-3141
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    As typical nonequilibrium phenomena, linear waves propagating in isotropic solids at finite temperatures are studied on the basis of both microscopic and macroscopic systems of basic equations, which were proposed in the previous papers of the present series. The temperature dependences of the propagation speeds of the longitudinal and transverse harmonic waves are derived explicitly for several metals. Their amplitude ratios are also obtained as the functions of the temperature. Singularities of the physical quantities at the melting point are found out and discussed. The validity of the so-called local equilibrium assumption, which has usually been taken for granted in nonequilibrium thermodynamics, is reexamined by comparing the macroscopic results with the microscopic ones in detail. And a possibility of going beyond the local equilibrium assumption in the analyses is discussed in connection with extended thermodynamics.
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  • Hirofumi Wada
    2003 Volume 72 Issue 12 Pages 3142-3150
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We investigate the dynamics of phase separation in two-component fluid membranes confined between parallel and rigid bounding plates. Through numerical simulation, we find dramatic slow coarsening of the order parameter field within the simulation time. In particular, a microphase separation is obtained as an equilibrium phase for sufficiently large values of the elastic coupling, being consistent with the previous mean-field analysis. We also provide the physical interpretation of such slow kinetics in terms of the elastic effects arising from the Helfrich interactions, together with theoretical analysis on the average domain size in the strong segregation regimes.
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  • Chi-Chuan Hwang, Jee-Gong Chang, Jian-Ming Lu, Hong-Chang Lin
    2003 Volume 72 Issue 12 Pages 3151-3157
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    This paper employs a dual damascene simulation to study the filling mechanisms of a dual via for the ionized physical vapor deposition (IPVD) process. The study focuses principally upon the influence of incident atom energy and via geometry upon the final dual via coverage. Additionally, the improvement in coverage which results from the use of beveled edges within the via is also considered. The molecular dynamics (MD) method is employed to simulate the filling process. The simulation is based upon three MD models, namely the dual via model, the deposition model and the potential model. Furthermore, the simulation incorporates the thermal control layer marching algorithm in order to increase the accuracy of the solution and to reduce the computational time. The results of the study show that in general, the coverage of both vias improves as the incident energy of the deposited atom increases, i.e. the filling pattern changes from anti-conformal to conformal, and then finally to super-filling as the incident energy increases. Typically, the optimum coverage of the upper via is obtained for a large via-radius ratio. However, it is found that coverage of the lower via is not only dependent upon the via-ratio, but that it is also strongly influenced by the incident energy of the deposited atoms. At lower incident energy levels, the via geometry effect governs the coverage results. However, as the incident energy increases, the incident energy effect becomes the dominant factor in determining the final coverage. It is determined that the interaction of these two effects influences the nature of the relationship between the coverage percentage and incident energy for different ranges of the via-radius ratio.
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  • Hiroshi Kawai, Ryo Miyata, Yoshihide Yoshimoto, Masaru Tsukada
    2003 Volume 72 Issue 12 Pages 3158-3163
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The improved model potential of the dimer system on Si(001) surface is obtained based on the results of the first-principles calculation (FPC). The transition rates of the dimer flip-flop motion are obtained from the model potential. The time-resolving dynamical Monte Carlo simulations (TDMCS) on Si(001) surface at 70 K for the orientational arrangement are performed. The time series of the time-averaged local order parameter for c(4×2) structure are calculated from the results of TDMCS. The time series are shown to reproduce well the results of time-resolving constant-height current mode STM observed at 70 K. The improved model potential is confirmed to be well effective.
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  • Kunihisa Morita, Hideaki Maebashi, Kazumasa Miyake
    2003 Volume 72 Issue 12 Pages 3164-3173
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    It is discussed on the fluctuation-exchange (FLEX) approximation that the charge susceptibility χc increases divergently in the 2D tt′ Hubbard model near the half-filling as the strength of the onsite Coulomb interaction U is approached to the critical value Ucr for the critical point to onset of the antiferromagnetic (AF) order. It turns out that the main origin of the divergence of χc is the Aslamazov–Larkin (AL) type contribution which can be taken into account by the FLEX approximation and is enhanced by the strong AF correlations because two AF-fluctuation modes and the vertex corretions work cooperatively to enhance χc. Indeed, AL-type contribution almost exhausts the enhanced part of χc in the region U\\simeqUcr. This result is consistent with experimental observations in under-doped cuprates LSCO and quantum Monte Carlo simulations by Furukawa and Imada [J. Phys. Soc. Jpn. 62 (1993) 2557].
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  • Akira Ochiai, Yuji Shima, Makoto Shirakawa
    2003 Volume 72 Issue 12 Pages 3174-3181
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    A structural transition from the cubic anti-Th3P4 structure to the trigonal one has been found in the single crystal of Eu4As3 as the temperature is decreased below 340 K. Anomalies in the structural, transport and thermal properties associated with this transition are very similar to those found in the charge ordering of Yb4As3 and Sm4Bi3. The absence of orbital moment for Eu2+ ions indicates that the orbital freedom plays no role in the charge ordering in Eu4As3. The ferromagnetic transition at 18 K is dominated by the exchange interaction between a divalent ion and a trivalent ion. We also discuss the role of the orbital freedom in the charge ordering of Eu4As3, Yb4As3, and Sm4Bi3.
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  • Masami Tsubota, Fumitoshi Iga, Toshihiro Nakano, Kazuyuki Uchihira, So ...
    2003 Volume 72 Issue 12 Pages 3182-3188
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The measurements of electrical resistivity, magnetic susceptibility, specific heat, thermopower and powder x-ray diffraction under pressure have been performed on single crystals of Y1−xCaxTiO3 (0.37≤x≤0.41) to investigate the hole-doping effect and pressure effect on the metal–insulator (MI) transition. In the low-temperature metallic state, the Ti moment is much reduced from S=1⁄2 spin moment in the high-temperature insulating state. Upon applying pressure on the sample with x=0.37 at temperatures below 200 K, the volume fraction of the orthorhombic phase exceeds that of the monoclinic phase, which is associated with the insulator to metal transition. The good correspondence between the xT and PT phase diagrams in the vicinity of the MI transition shows that the effect of hole doping by 1% Ca substitution is equivalent to the effect of application of pressure of 0.41 GPa. The phase separation temperature agrees well with the MI transition temperature, and both temperatures increase linearly with increasing x or pressure. These results indicate that the MI transition in Y1−xCaxTiO3 is driven by percolation of the low-temperature orthorhombic domains.
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  • Shuichi Fukuda, Yuji Nakanuma, Junji Sakurai, Akihiro Mitsuda, Yosikaz ...
    2003 Volume 72 Issue 12 Pages 3189-3196
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    To investigate the valence transition of Eu in the pseudo-binary compounds series, EuCu2(SixGe1−x)2, measurements of the lattice constants, the X-ray absorption spectroscopy (XAS), the magnetic susceptibility, χ, the electric resistivity, ρ, the thermoelectric power, S, and the specific heat, C, have been carried out. The antiferromagnetic order for the samples with 0≤x≤0.50, the temperature-induced valence transition for the samples with 0.68≤x≤1.0 and the state with a high electronic specific heat coefficient for the samples having the intermediate range of x of the above two were observed. The plotting of the Néel temperature, TN, and of the valence transition temperature, TV, as the function of x is found to resemble very well to the Doniach diagram, giving an evidence of the competition of the two interactions, the one for the valence transition, the other for the magnetic order. The observation of the sign change of S near to the temperature TV is found to be a new feature of Eu compounds.
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  • Hirofumi Wada, Hironori Yoshioka, Tsuneaki Goto, Keiichi Koyama, Kazuo ...
    2003 Volume 72 Issue 12 Pages 3197-3203
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Magnetization curves were measured for GdMn2Ge2 single crystals, which show a first-order magnetic transition from a ferrimagnetic state to an antiferromagnetic state at T1=95 K. The field-induced transition from the ferrimagnetic state to a high-field state was observed for both Hc and H||c below T1. The transition field, HC, in Hc goes to zero with increasing temperature to T1, while that in H||c gradually decreases without falling to zero at T1. The results were analyzed in terms of a molecular field approximation, in which strong strain dependence of the interlayer Mn–Mn interaction was taken into consideration. The experimental data are well reproduced by the calculated results. The calculations predict that the compound undergoes double magnetic transitions in high magnetic fields for H||c just above T1, which was confirmed by the measurements.
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  • Takahiro Yamamoto, Rumi Manago, Yoshihiro Mori, Chikara Ishii
    2003 Volume 72 Issue 12 Pages 3204-3211
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Magnetization processes of frustrated Kondo necklace model are studied by means of a density matrix renormalization group (DMRG) method and an elementary band theory based on a bond-operator formalism. The DMRG calculations clearly show the cusp singularity in a low-magnetization region (0<m<1⁄2) besides that in a high-magnetization region (1⁄2<m<1) which is expected from previous studies on the magnetization curve of the Majumdar–Ghosh model. An appearance mechanism of the low-magnetization cusp is interpreted in terms of a double-well shape of a low-energy band arising from frustrations between nearest- and next-nearest-neighbor interactions. We also discuss critical behaviors of magnetization near the cusp and obtain a phase diagram showing whether the cusp appears in the magnetization curve or not.
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  • Kiyoichiro Motoya, Keiko Hioki, Jun-ichi Suzuki
    2003 Volume 72 Issue 12 Pages 3212-3218
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    In order to probe the microscopic mechanism of slow dynamics in spin-glass materials, a time-resolved small angle neutron scattering (SANS) experiment has been made. Time-resolved SANS patterns from a concentrated spin-glass alloy Fe0.70Al0.30 have been taken up to 20 h under various temperature and magnetic field with a typical time window of 10–30 min. We discuss the temperature and magnetic field dependence of the time evolution of the scattering pattern based on a magnetic cluster model.
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  • Peter Thalmeier, Ryousuke Shiina, Hiroyuki Shiba, Atsushi Takahashi, O ...
    2003 Volume 72 Issue 12 Pages 3219-3225
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We study the temperature and field dependence of multipolar excitations in CeB6 within RPA theory for the dynamical susceptibility. It is shown that the destruction of AFQ order at constant field close to TQ(H) should lead to a collapse of the high energy part of the excitation spectrum. In the disordered state above TQ(H) the dispersions show a qualitative change due to the vanishing multipolar order parameters. We also study the field dependence of excitations at constant temperature and compare with experimental results obtained at the X(001) point. In the low temperature T<<TQ and intermediate to high field regime HTQ we compare the results to those of the extended Holstein Primakoff (HP) approach and find complete agreement.
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  • N. Hanasaki, M. Matsuda, H. Tajima, T. Naito, T. Inabe
    2003 Volume 72 Issue 12 Pages 3226-3230
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We measured the static magnetic susceptibility and the electron spin resonance of the Fe(Pc)(CN)2 complexes, and investigated the molecular magnetism of the unit Fe(Pc)(CN)2. The magnetic susceptibility shows a highly anisotropic Curie behavior. Based on the electron spin resonance, we found a highly anisotropic g-value (g1=3.62, g2=1.11, and g3=0.52) in the molecular unit Fe(Pc)(CN)2. This anisotropy is caused by the molecular orbital angular momentum in the degenerate next highest occupied molecular orbitals of the molecular unit Fe(Pc)(CN)2. Since the molecular unit Fe(Pc)(CN)2 has a unique structure with fourfold symmetry, the molecular orbital angular momentum has a finite value of lz∼+1 and −1. The anisotropic molecular magnetism of the unit Fe(Pc)(CN)2 contributes the highly anisotropic Curie behavior. The molecular unit Fe(Pc)(CN)2 is a good candidate for a molecular magnet having high magnetic anisotropy.
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  • Aya Tobo, Kenichi Ishimoto, Junya Konno, Kenji Ohoyama, Koji Kaneko, Y ...
    2003 Volume 72 Issue 12 Pages 3231-3236
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Specific heat, dc- and ac-magnetic susceptibility and magnetization measurements were performed on rare earth intermetallic compounds Ce1−xLuxB2C2 (0≤x≤0.31) in order to elucidate the magnetic interaction in CeB2C2. In the process of the substitution of Ce by Lu in CeB2C2, the characteristics of magnetic transition change from a first-order transition to a second-order one. Furthermore, the spin-glass phase appears at Lu concentration x=0.31. We suppose that the ferromagnetic (FM) and antiferromagnetic (AFM) interactions compete and nearly cancel out each other in CeB2C2, and hence that a biquadratic interaction might cause the first-order magnetic transition at TN. The Lu substitution breaks the competition between AFM and FM interactions and brings forth randomness in interactions acting on each Ce moment. The typical spin-glass behavior of x=0.31 originates in this random distribution of magnetic interactions.
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  • Tomohiko Nakajima, Hiroshi Kageyama, Hideki Yoshizawa, Kenji Ohoyama, ...
    2003 Volume 72 Issue 12 Pages 3237-3242
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The most significant structural feature of the A-site ordered manganese perovskites, RBaMn2O6, is that the MnO2 square sublattice is sandwiched by two types of rock-salt layers, RO and BaO, with much different sizes and consequently the MnO6 octahedron itself is distorted in a noncetrosymmetric manner. The structures and electromagnetic properties of RBaMn2O6 (R = La, Pr and Nd) have been investigated. They have tetragonal structures with no tilt of MnO6 octahedra and show ferromagnetic metal transitions. The ground state is a coexistence of ferromagnetic metal and antiferromagnetic charge-orbital ordered phases for LaBaMn2O6 and A-type antiferromagnetic metal for PrBaMn2O6 and NdBaMn2O6. These ground state behaviors are explained by the effect of Mn–O distance on the bandwidth and the layer structure with the RO–MnO2–BaO–MnO2 stacking along the c-axis.
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  • Hiroyuki Nojiri, Hiroshi Kageyama, Yutaka Ueda, Mitsuhiro Motokawa
    2003 Volume 72 Issue 12 Pages 3243-3253
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The excited state energy spectrum of a two-dimensional dimer system SrCu2(BO3)2 has been investigated by high field ESR. Besides two non-degenerated one-triplet excitations, various types of multiple-triplet bound states are identified: singlet, triplet, and quintet. The intensity of these bound states is extremely strong because one-triplet process is strongly suppressed in the orthogonal dimer system. The bound singlet state is found slightly below the energy gap of the one-triplet state, indicating the proximity to a quantum critical point. A band of the two-triplet bound state splits due to distant neighbor interactions. The bound quintet state is the direct evidence of two-triplet object made up of four S=1⁄2 spins. The energy of the lowest quintet becomes lower than that of the one-triplet excitation before the closing of the lowest spin gap, namely, the quintet touches first to the ground singlet state. The present investigation exhibits an essential role of multiple-triplet bound states in the magnetic excitation spectrum.
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  • Koji Yoshida, Hiroki Kojima, Hajime Shimizu
    2003 Volume 72 Issue 12 Pages 3254-3258
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We studied magnetization and ESR on RuSr2R1.4Ce0.6Cu2O10 (Ru1222; R = Gd, Eu). A ferromagnetic hysteresis in MH curves is observed below TM=180 K. The saturation moment is smaller than that for the expected Ru5+. These results suggest that Ru1222 is weak ferromagnetic. Interestingly, an enhancement in M observed at 100 K is more substantial than that observed at TM. ESR measurements confirm that this anomalous behavior originates from a change in the Ru moment.
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  • Shigeru Takagi, Daisuke Maruta, Hiroshi Uozaki, Hideaki Tsuchiya, Yasu ...
    2003 Volume 72 Issue 12 Pages 3259-3265
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Extending previous 77Se NMR studies [J. Phys. Soc. Jpn. 72 (2003) 483], the microscopic magnetic properties of superconducting (TC≅5–6 K) λ-(BETS)2GaCl4 [BETS = bis(ethylenedithio)tetraselenafulvalene] have been investigated by 1H NMR in the normal state between 7.1 and 140 K on randomly oriented single crystals. Contrary to almost T-independent 1⁄(77T1T) of the 77Se NMR, 1⁄(1T1T) of the 1H NMR shows a significant increase below about 25 K. This quite contrasting low-T behavior in 1⁄(T1T) between 77Se and 1H is shown to be explained consistently in terms of the development of antiferromagnetic spin fluctuations of π-electrons, which has already been indicated by the 77Se NMR as a significant low-T decrease in the intrinsic uniform susceptibility χq=0(T) and no concomitant decrease in 1⁄(77T1T). In the explanation, it is pointed out that the inter-atomic dipolar interaction with the extended spin polarization of the HOMO plays an important role in the 1H nuclear magnetic relaxation, which has been disregarded in previous 1H NMR studies on related organic conductors.
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  • Koo-Chul Je
    2003 Volume 72 Issue 12 Pages 3266-3270
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We have investigated the importance of the relative phase (φ) between the THz field and the optical field, which is used to monitor the interband absorption, and cw optical absorption spectrum in biased semiconductor superlattices. All of the absorption spectra have Stark ladder structures and the peaks of the Stark ladders are changed for the different phases. Especially, it is demonstrated that the changes of the Stark ladders from those φ=0 occur periodically in four ladders for φ=π and in eight ladders for φ=π⁄2 in the absence of dynamical localization. The cw optical absorption spectrum, which is obtained as an average over the phases by using short pulse technique, have no gain peaks. Because this procedure leads to a cancellation of regions of negative absorption which may occur in the coherent THz-driven system.
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  • Keisuke Ohdaira, Hiroshi Murata, Shinji Koh, Motoyoshi Baba, Hidefumi ...
    2003 Volume 72 Issue 12 Pages 3271-3275
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We found that the AlInAs/AlGaAs self-assembled quantum dots (QDs) systematically changed from type-I to type-II band alignment in real and momentum space with increasing Al composition and QD coverage. A characteristic peak shift corresponding to the transition from type-I to type-II band alignment was observed when Al composition of AlGaAs matrix was increased. Time-resolved photoluminescence measurements revealed that there was a slow decay component corresponding to the type-II recombination as well as type-I-related fast component and that the slow component became dominant as Al composition of the matrix was increased. Samples containing only type-II QDs were successfully grown by optimizing the growth conditions and in these samples, a recombination lifetime of 30 ns, which was determined by the strong Γ–X mixing, was observed for the type-II transition.
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  • Masato Suzuki, Ken-ichi Fujii, Tyuzi Ohyama, Hiromi Kobori, Nobuo Kote ...
    2003 Volume 72 Issue 12 Pages 3276-3285
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    We have studied resonant Faraday effect (RFE) related to the intraband transitions in various semiconductors at low temperature through direct measurements for the Faraday rotation angle and ellipticity of the probe far-infrared (FIR) light. Through cyclotron resonance due to electrons in a thin n-InSb sample and two-dimensional electrons in the interface of GaAs/AlGaAs as well as the impurity absorption by donors in the n-InSb, we have made clear that RFE is dominated by the off-diagonal components of dielectric tensor. Experimental results for bulk n-InSb samples with various thicknesses have revealed a lot of properties of RFE as saturation effect on absorption. The oscillatory spectra induced by several twirls of the polarization plane have been observed in the extremely thick InSb sample. Spectra of the thick n-InSb also show high sensitivity of ellipticity for interference of circularly polarized lights. Besides, making use of the characteristic behavior on RFE, we can classify absorption lines due to impurities in Ge, i.e., the electron-type absorption or the hole-type one. By referring the experimental results to the theory based on Lorentz-oscillator model, we have made clear some characteristic features on RFE.
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  • Yoshihiro Asai, So Hirata, Koichi Yamashita
    2003 Volume 72 Issue 12 Pages 3286-3290
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    Mechanism of electron-excitation-induced polymerization from diacetylene monomer to polydiactylene was studied theoretically. The single electron configuration interaction (SE-CI) method based on ab-initio Hartree–Fock crystal orbital theory was used for the calculation. Potential energy curves of electronically excited singlet and triplet states along a hypothetical reaction coordinate were calculated. The lowest triplet state of miss-aligned diacetylene monomer was found to be metastable, which agrees with experiments. The local electronic excitation mechanism found in this polymerization reaction was discussed in the context of the polymerization initiated by scanning tunneling microscope (STM).
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  • Yuguo Yu, Feng Liu, Wei Wang
    2003 Volume 72 Issue 12 Pages 3291-3296
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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    The occurrence of synchronized oscillation and its critical behavior in a globally coupled stochastic Hodgkin–Huxley (HH) neuronal network are studied in this paper. It is found that there is a critical curve for the coupling strength versus noise intensity, which shows a V-shaped structure and divides the network behavior into an asynchronous firing state and a synchronous one. Analysis of the scaling behavior near the bifurcation point reveals that this transition is analogous to a second-order phase transition. The frequency of synchronized oscillations is within the range of 40–80 Hz, and its physical origin is explored by studying single HH neuron’s impedance. The intrinsic property of single neuron may account for the generation and the frequency characteristics of synchronized rhythmic oscillations.
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  • Lorenzo Frassinetti, Yasuyuki Yagi, Piero Martin, Haruhisa Koguchi, To ...
    2003 Volume 72 Issue 12 Pages 3297-3298
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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  • Takanori Fukami, Ruey-Hong Chen
    2003 Volume 72 Issue 12 Pages 3299-3300
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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  • Akira Oguri
    2003 Volume 72 Issue 12 Pages 3301-3302
    Published: December 15, 2003
    Released on J-STAGE: July 25, 2007
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