Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 71, Issue 9
Displaying 1-50 of 52 articles from this issue
  • Shohei Fukano, Yumino Hayase, Hiizu Nakanishi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2075-2077
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Motivated by bouncing motion of an inelastic particle on a vibrating board, a simple two-dimensional map is constructed and its behavior is studied numerically. In addition to the typical route to chaos through a periodic doubling bifurcation, we found peculiar behavior in the parameter region where two stable periodic attractors coexist. A typical orbit in the region goes through chaotic motion for an extended transient period before it converges into one of the two periodic attractors. The basin structure in this parameter region is almost riddling and the fractal dimension of the basin boundary is close to two, i.e., the dimension of the phase space.
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  • Yutaka Moritomo, Kenichi Kato, Akira Kuriki, Masaki Takata, Makoto Sak ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2078-2081
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Temperature dependence of atomic coordinates is determined for RbMn[Fe(CN)6] by means of synchrotron-radiation (SR) X-ray powder structural analysis. We observed a structural transition from the cubic (F¯43m; Z = 4) to the tetragonal (I¯4m2; Z = 2) phase at ≈ 210 K in the cooling run and at ≈ 300 K in the warming run. In the low-temperature tetragonal phase, we found Jahn–Tellar type distortion of the MnN6 octahedra and compression of the averaged Fe–C bond distance. These structural data suggest that the structural transition is triggered by the inter-metallic charge-transfer from the Mn(II) site to the Fe(III) site.
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  • K. Kato, E. Nishibori, M. Takata, M. Sakata, T. Nakano, K. Uchihira, M ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2082-2085
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    In order to explore the origin of the metal-insulator (M-I) transition, the precise crystal structures of the hole-doped Mott insulator system, Y1-xCaxTiO3 (x=0.37, 0.39 and 0.41), are studied for the temperature range between 20 K and 300 K by synchrotron radiation (SR) X-ray powder diffraction. For both Y0.63Ca0.37TiO3 and Y0.61Ca0.39TiO3 compositions, the orthorhombic (Pbnm) - monoclinic (P21/n) structural phase transition occurs at approximately 230 K, which is much higher than their individual M-I transition temperatures, i.e., 60 K and 130 K, respectively. For these compositions, significant phase separation (low-temperature orthorhombic + monoclinic) is also found in the vicinity of the M-I transition temperature. On the other hand, Y0.59Ca0.41TiO3, which does not exhibit M-I transition and preserves a metallic behavior down to 1.5 K, is in a two phase state from 20 K to 300 K. It is concluded that the existence of the phase separation causes the M-I transition in Y1-xCaxTiO3, and the low-temperature orthorhombic phase contributes to the metallic property of this system.
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  • Shigeki Miyasaka, Yoichi Okimoto, Yoshinori Tokura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2086-2089
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Anisotropic optical spectra coupled with antiferromagnetic spin ordering (SO) and orbital ordering (OO) have been investigated for single crystals of LaVO3 and YVO3. The orbital-dependent Mott-Hubbard gap transitions are observed around 2 eV. The transitions composed of the two peaks show distinct anisotropy and selection rules, reflecting the respective SO and OO patterns. The temperature dependence of the anisotropic transitions clearly indicates the SO/OO correlation and the evolution of the order parameters.
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  • Agung Budiyono, Katsuhiro Nakamura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2090-2093
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Using the semiclassical Kubo formula for conductivity, we give a periodic-orbit picture for the recently observed fractal magnetoconductance fluctuations in submicron-scale phase coherent ballistic billiards. The self-similar conductance fluctuations are shown to be caused by the self-similar unstable periodic orbits which are generated through a sequence of isochronous pitchfork bifurcations of straight-line librating orbits oscillating towards harmonic saddles. The saddles are naturally created right at the point of contact with the leads or at certain places in the cavity as a consequence of the softwall confinement. Therefore, our mechanism is able to explain all the self-similar magnetoconductance fluctuations in general softwall billiards. In contrast to the existing theory which claims that a classical mixed phase space is necessary, we argue that, even in the fully chaotic phase space, the self-similar magnetoconductance fluctuations should be observed as long as the self-similar unstable periodic orbits are preserved.
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  • Kensuke Kobayashi, Hisashi Aikawa, Shingo Katsumoto, Yasuhiro Iye
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2094-2097
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We have measured transport through mesoscopic Aharonov-Bohm (AB) rings with two different four-terminal configurations. While the amplitude and the phase of the AB oscillations are explained well within the framework of the Landauer-Büttiker formalism, it is found that the probe configuration strongly affects the coherence time of the electrons, i.e., the decoherence is strongly reduced in the configuration of so-called nonlocal resistance. This result should provide an important clue in clarifying the mechanism of quantum decoherence in solids.
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  • Yuji Aoki, Takahiro Namiki, Shuji Ohsaki, Shanta R. Saha, Hitoshi Suga ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2098-2101
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We report measurements of low-temperature specific heat on the 4ƒ2-based heavy-fermion superconductor PrOs4Sb12. In magnetic fields above 4.5 T in the normal state, distinct anomalies are found which demonstrate the existence of a field-induced ordered phase (FIOP). The Pr nuclear specific heat indicates an enhancement of the 4ƒ magnetic moment in the FIOP. Utilizing a Maxwell relation, we conclude that anomalous entropy, which is expected for a single-site quadrupole Kondo model, is not concealed below 0.16 K in zero field. We also discuss two possible interpretations of the Schottky-like anomaly at ∼3 K, i.e., a crystalline-field excitation or a hybridization gap formation.
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  • Yukio Tanaka, Yasunari Tanuma, Kazuhiko Kuroki, Satoshi Kashiwaya
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2102-2105
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We study the influence of a magnetic field H on the zero bias conductance peak (ZBCP) due to zero energy Andreev bound states (ZES) in a normal metal/unconventional superconductor. For p-wave junctions, ZBCP does not split into two by H even for sufficiently low transparent junctions, where ZBCP clearly splits for d-wave. This unique property originates from the fact that for p-wave superconductors, perpendicularly injected quasiparticles form ZES, which contribute most dominantly to the tunneling conductance. In addition, we show that for px+ipy-wave superconductor junctions, the height of ZBCP is sensitive to H due to the formation of a broken time reversal symmetry state. We propose that tunneling spectroscopy in the presence of a magnetic field, i.e., magnetotunneling, is a promising method of determining the pairing symmetry of unconventional superconductors.
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  • Hyun-Tak Kim
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2106-2108
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    For the mechanism of high-Tc superconductivity in inhomogeneous Bi2Sr2CaCu2O8+x superconductors, we demonstrate the intrinsic superconducting gap, Δi, and pairing symmetry by using a developed Δ=Δi/ρ, where Δ is the observed energy gap and 0<ρ≤ 1 is band filling. When ρ=1, Δ=Δi≤10 meV, measured at a node, is intrinsic. When 0<ρ<1, Δ implies an averaging of Δi over the measurement region, which is an effect of the measurement. From spectra of the density of states (DOS), b=2Δi/kBTc is less than 4 when ρ=1 and the DOS indicates s-wave symmetry. The superconducting gap anisotropy is attributed to the inhomogeneity of the metal phase and the insulating d-wave phase in the measurement region.
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  • Hidekazu Morita, Shinji Watanabe, Masatoshi Imada
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2109-2112
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We study phase diagrams of the Hubbard model on anisotropic triangular lattices, which also represents a model for κ-type BEDT-TTF compounds. In contrast with mean-field predictions, path-integral renormalization group calculations show a universal presence of a nonmagnetic insulator sandwiched by an antiferromagnetic insulator and paramagnetic metals. The nonmagnetic phase does not show simple translational symmetry breakings such as flux phases, implying a genuine Mott insulator. We discuss possible relevance to the nonmagnetic insulating phase found in κ-(ET)2Cu2(CN)3.
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  • Tota Nakamura, Shin-ichi Endoh
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2113-2116
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The possibility of a simultaneous spin-glass and chiral-glass transition is pointed out in the three-dimensional ± J Heisenberg model. It is investigated by the nonequilibrium relaxation method starting from the paramagnetic state. The finite-time scaling analysis of the relaxation function of the infinite-size system gives the spin-glass transition at Tsg/J=0.21-0.03+0.01 and the chiral-glass transition at Tcg/J=0.22-0.04+0.01: these coincide within the acceptable range of numerical error. The critical exponent of the spin-glass susceptibility obtained is γsg= 1.9 ± 0.4, which is in agreement with the results of experiments on insulating and canonical spin-glass materials.
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  • Hiroyuki Nakamura, Akihito Nakahara, Masayuki Shiga, A. V. Tsvyashchen ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2117-2120
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The ground-state magnetism of a high-pressure-synthesized cubic Laves phase compound LaCo2 was investigated by 59Co NMR experiments. At low temperatures, we found two kinds of NMR signals corresponding to small internal fields, -2.8 and 0.1 T, which are separated due to the anisotropy in the hyperfine field. This result reveals the weak ferromagnetism in LaCo2, indicating that a small spontaneous Co moment can exist in rare-earth-cobalt Laves phase compounds with neither a molecular exchange field from rare-earth atoms nor effects of disorder. The ordered moment and the easy magnetization axis are estimated to be <0.1 μB/Co and [111], respectively.
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  • Keiji Fukui, Akio Kotani
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2121-2124
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The incident photon angle dependence is calculated analytically with an atomic model for the spectrum of magnetic circular dichroism of resonant X-ray two-photon absorption (MCD-RXTA). From a general expression of the angle dependence for circularly polarized incident photons, a simple and symmetric expression of MCD-RXTA is derived in the case where the MCD is observed for both photons. When the incidence angle of one of the photons is perpendicular to the magnetization direction, the MCD-RXTA is brought about by the quantum mechanical interference effect of the coherent second-order optical process. Numerical calculations of MCD-RXTA spectra are also performed for the Gd 3d-4f and 2p-3d RXTA for a Gd3+ system.
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  • Atsushi Goto, Tadashi Shimizu, Kenjiro Hashi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2125-2127
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We propose a method of controlling a quantum logic gate in a solid-state NMR quantum computer. A switchable interqubit coupling can be generated using the longitudinal component of the Suhl-Nakamura interaction induced by a local singlet-triplet excitation in a one-dimensional antiferromagnet with a spin gap.
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  • N. H. Abdel-Wahab, Magdy E. Amin, M. F. Mourad
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2129-2132
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    In this paper, we investigate the entanglement degree in the interaction of a two-level atom prepared in a momentum eigenstate with an additional Stark-shift. We use the quantum entropy as a measure of the entanglement degree. The constants of motion and the density matrix of the system are obtained. The effect of the detuning and the Stark-shift parameters when the atom is prepared initially in the upper state are investigated. It is found that the detuning and the Stark shift affected on the entanglement of the atomic system, and the influence of the center-of-mass motion play an important role in the entanglement degree.
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  • Hyun-Joo Kim, Youngki Lee, Byungnam Kahng, In-mook Kim
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2133-2136
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    While many scale-free (SF) networks have been introduced recently for complex systems, most of them are binary random graphs. Here we introduce a weighted SF network in associated with the cross-correlations in stock price changes among the S&P 500 companies, where all vertices (companies) are fully connected and each edge has nonuniform weight given by the covariance between the two returns connected, normalized by their volatilities. Influence-strength (IS) is defined as the sum of the weights on the edges incident upon a given vertex. Then the IS distribution in its absolute magnitude |q| exhibits a SF behavior, PI(|q|)∼ |q| with the exponent η ≈ 1.8(1).
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  • Atsushi Fukumi, Dilip Angom, Ichita Endo, Takayoshi Horiguchi, Masatak ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2137-2141
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The Stark-induced electric dipole (E1) transition for a high-lying odd-parity level in atomic samarium (Sm) was observed with an optical double-resonance technique as a preliminary study for measuring parity nonconservation (PNC). While a pump laser was locked to an E1 transition from the 0-cm-1 to 15650.55-cm-1 levels, a probe laser was tuned to the parity forbidden transitions under static electric field. For the probe transition from the 15650.55-cm-1 to 28233.08-cm-1 levels, we have observed the Stark-induced E1 transition. In order to investigate the contribution of the 28233.08-cm-1 level to the Stark-induced E1 transition, the tensor polarizability was measured. We have found that the observed Stark-induced E1 transition is anomalously strong compared with the one estimated from α2 and an E1 transition measured as a reference. The transition is one of candidates for improving the precision of the PNC measurements.
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  • Yasufumi Susuki, Takeshi Ikeda, Katsuhiko Katsura
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2142-2147
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Neutral fractions are measured for ions transmitted parallel to the beam direction at the incidence of (0.3-0.6) MeV H+ beams on a poly-crystalline aluminum foil with a variance in the angle of incidence θ. The fraction measured for the equivalent ion-energy decreases with the decreasing angle of incidence. The relative difference between the fractions at the normal (θ=90°ree) and inclined (θ=30°ree) incidence increases slightly with the increasing energy of the ions. The dependence of fraction on the angle is calculated by using a model for the charge-exchange that includes not only the electron loss from and electron capture into the 1s state of hydrogen, but also the electron loss after an excitation of hydrogen in collisions with the atoms on the topmost layer of the surface. The electron loss of the excited hydrogen enhances the decrease of the fraction at the inclined incidence and this improves the calculated results to reproduce the experimental one.
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  • Tohru Nakano, Daigen Fukayama, Alexander Bershadskii, Toshiyuki Gotoh
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2148-2157
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Using data of a direct numerical simulation (DNS) of 3D turbulence it is shown that the moments of order between 1 and 6 of both longitudinal and transverse components of velocity increment for forced as well as decay turbulence can be described by stretched lognormal distribution for all scales from the dissipation to the inertial ranges and for all values of Reynolds number investigated in this DNS (50<Rλ<459). A new (local) version of extended self-similarity has been used for this purpose. Effects of vortex structure on increment of velocity field in forced and in decay turbulence are briefly discussed.
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  • Tatsufumi Nakamura, Susumu Kato, Tomokazu Kato
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2158-2163
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    A new method, based on a theory of a stochastic process, to study the mechanism of the anomalous absorption of an intense laser light in an overdense plasma is presented. A basic process of the anomalous skin effect is treated as a stochastic process in the time scale of electron Lamour motion in the laser field, i.e., microscopic scale. A diffusion equation in momentum space which describes the time evolution of electron distribution function is derived. The distribution function evolves to anisotropic in momentum space. The absorption coefficient and skin depth are analytically extended to the relativistic intensity regime by taking into account the time evolution of the electron distribution function.
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  • Yoshimitsu Amagishi, Takanori Hishida, Tatsuya Ino, Motoshi Kobayashi, ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2164-2168
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We have observed two kinds of magnetohydrodynamic (MHD) instabilities excited in a current-carrying cylindrical plasma that was produced by a magneto-plasma-dynamic (MPD) arcjet. The “net current” in the plasma excites the instability with the azimuthal mode number m=1, which is deduced to be a kink mode from MHD theory. On the other hand, the m=0 instability is excited by the “total current” flowing to the cathode, and this mode was found to be responsible for the modulation of electron temperature. They are converted respectively to m=1 compressional Alfvén wave and m=0 global Alfvén eigenmode, propagating along the axial magnetic field in the current-free region.
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  • K. H. Pae, S. J. Hahn
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2169-2173
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The time-dependent spatio-temporal structures in positive-bias plasma diodes are investigated by employing a one-dimensional particle simulation. Nonlinear evolution of a large-amplitude self-oscillation and transitions to chaos are analyzed by using the time-varying potential profiles and their power spectra. The three standard routes to chaos (period doubling, intermittency, and quasiperiodicity) are observed and the first observation of the attractor-competing phenomena is also reported.
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  • Masayoshi Takahashi, Eiji Izawa, Jiro Etou, Tomoyuki Ohtani
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2174-2177
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Water in fluid inclusions achieved a superheated condition by isochoric cooling method and the kinetic characteristic of bubble nucleation in water was investigated. The conventional study did not succeed in drawing a picture of bubble nucleation in water. The present study demonstrates that the homogeneous nucleation theory can describe the kinetic property of bubble nucleation in water, and that density fluctuation is a random event which brings about bubble nucleation in superheated water, and the lifetime of superheated water can be predicted with respect to the depth of penetration into the metastable region by the theory.
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  • Hitoshi Furukawa, Tetsuo Ohmi
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2178-2185
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We calculate the thermal conductivity of solid 3He in U2D2 phase. In this system, magnons are the dominant heat carriers. The experiment by Feng et al. shows that scattering of magnons by some kind of magnetic defects becomes important at low temperatures. We suppose that the magnetic plane defects (MPDs) originate from lattice dislocations, and calculate the thermal conductivity by the same procedure as used in the calculation of Kapitza Resistance (KR). From our results, we find that our model is able to explain the experimental result qualitatively. We also estimate the mean distance between magnetic plane defects and get the reasonable value.
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  • Ho-Young Kwak, Jung-Yeul Jung, Jae-Ho Hong
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2186-2191
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    As the temperature of liquid under negative pressure approaches the absolute zero, nucleation due to thermal fluctuations rarely occurs. Instead of thermal motion, quantum fluctuations may induce the formation of nuclei for transition into a new phase from the metastable state. In this study, a theoretical investigation with molecular cluster model was performed on liquid helium under negative pressure to examine the thermal as well as the quantum nucleation of bubbles and the cross-over temperature from the thermal to the quantum regime. The energy barrier against nucleation was estimated from the molecular interaction due to London's dispersion force. The phase transition from liquid to vapor was shown to be only possible due to the quantum tunneling below 0.25 K for helium-4 and 0.175 K for helium-3. The cross-over temperatures which depends on the square root of the single particle quantum vibrational energy times the free energy of the critical cluster were comparable to the calculated results obtained through the density functional approach and the functional-integral approach. Also, the negative pressures needed for bubble nucleation on vortices lines were calculated and the results were found to be in good agreement with observations.
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  • Hiroshi Kawai, Yoshihide Yoshimoto, Hiromitsu Shima, Yoshimichi Nakamu ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2192-2199
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The time-resolving dynamical Monte Carlo simulations (TDMCS) on Ge(001) surface at 200 K for the orientational arrangement at finite temperature are performed. The model potential for the continuous values of the tilting angles are obtained. The coefficients in the model potential are obtained from results of the first-principles calculations. The transition rates of the dimer flip-flop motion for TDMCS are obtained from the model potential. The images of time-resolving constant-height current mode STM (TCHC STM) calculated from TDMCS results at 200 K exhibit the glimmering near kinks at step edge. The attempt frequency of the transition rates is confirmed as 3.0 THz from the frequecy of the single event of the dimer flip-flop for the period of 56 μs. The calculated results of TDMCS reproduce well results of the experimental TCHC STM.
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  • Shin-ichi Kimura, Mitsuru Okuno, Hideki Iwata, Hideaki Kitazawa, Giyu ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2200-2207
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The electronic structure of CeSb in the magnetically ordered states is examined by measuring the optical reflectivity, the magnetic linear dichroism and the magnetic circular dichroism spectra at low temperatures under magnetic fields in the infrared region. The optical conductivity spectrum, as well as the reflectivity spectrum changes significantly with the complex magnetic phase diagram, and gives detailed information of electronic structures in the ordered states. The spectra in the ordered states cannot be explained only by the energy band folding due to the appearance of the periodic magnetic structure. By comparing with the calculated optical conductivity spectra, we found that not only the Ce4ƒ-Sb5p mixing but also the Ce5d-Sb5p mixing mainly works in the ordered states.
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  • Toshikazu Nakamura, Masateru Taniguchi, Yohji Misaki, Kazuyoshi Tanaka ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2208-2215
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Low-temperature electronic phases in a new two-component organic conductor, a segregated-stack charge-transfer salt called (CHTM-TTP)2TCNQ, are investigated. The ESR g tensor analyses indicate that there exist itinerant CHTM-TTP spins and localized TCNQ spins at R.T. The temperature dependence of the physical parameters reveals that this salt undergoes two drastic, successive phase transitions at low temperatures. The effective moment of the localized TCNQ spins decreases at the 245 K transition and completely disappears at the transition around 195 K. These curious physical properties are explained by the drastic changes in the electronic states of the two different types of spins. The spin susceptibility was decomposed into the contribution of each of the two spin species by using ESR, 1H-NMR, and static susceptibility analyses. We present a microscopic investigation of the two-spin system with itinerant and localized moments.
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  • Koujin Takeda, Ikuo Ichinose
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2216-2223
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    In the previous paper, we studied the random-mass Dirac fermion in one dimension by using the transfer-matrix methods. We furthermore employed the imaginary vector potential methods for calculating the localization lengths. In particular, we investigated effects of the nonlocal but short-range correlations of the random mass. In this paper, we shall study effects of the long-range correlations of the random mass especially on the delocalization transition and singular behaviors at the band center. We calculate localization lengths and density of states for various nonlocally correlated random mass. We show that there occurs a “phase transition” as the correlation length of the random Dirac mass is varied. The Thouless formula, which relates the density of states and the localization lengths, plays an important role in our investigation.
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  • Tatsuya Yaguchi, Tsuneya Ando
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2224-2233
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Localized cap states are discussed in caps consisting of q graphene sheets of regular triangles (1 ≤ q ≤ 6) attached to a metallic nanotube both analytically and numerically in an effective-mass approximation. There are cap states at ε = 0 (the energy of a carbon π-orbital) associated with first excited conduction band and highest valence band. Cap states associated with other bands lie in the vicinity of the corresponding band edges. The wave function behaves as r-1/5 in the vicinity of a five-membered ring for states with ε = 0, where r is the distance from the ring.
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  • Yusuke Takazawa, Yoshiki Imai, Norio Kawakami
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2234-2239
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Correlation effects on electron transport through a system of T-shaped double-dots are investigated, for which only one of the dots is directly connected to the leads. We evaluate the local density of states and the conductance by means of the non-crossing approximation at finite temperatures as well as the slave-boson mean field approximation at zero temperature. It is found that the dot which is not directly connected to the leads considerably influences the conductance, making its behavior quite different from the case of a single-dot system. In particular, we find a novel phenomenon in the Kondo regime with a small inter-dot coupling, i.e. Fano-like suppression of the Kondo-mediated conductance, when two dot levels coincide with each other energetically.
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  • Yoshiro Shimojo, Takehiko Ishiguro, Makariy A. Tanatar, Alexey E. Kova ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2240-2246
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The superconductivity of the quasi two-dimensional (2D) organic compound α-(BEDT-TTF)2NH4Hg(SCN)4 in the magnetic field applied exactly parallel to the conducting plane is studied through the measurement of the specific heat, thermal conductivity and ac susceptibility in accordance with the resistance, covering the whole temperature range. According to the bulk measurements, the upper critical field Hc2 is close to the field giving the end-point of zero-resistance, while the onset-junction and midpoint criteria from the resistance measurement give notable overestimation of Hc2, indicating fluctuating and/or inhomogeneous contributions to superconductivity. The Hc2 at low temperature (0.1 K) is isotropic within the 2D plane and comparable to the BCS Pauli paramagnetic limit, although no first-order transition feature is observed. The detailed resistive transition characteristics are presented.
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  • Daisuke Matsunaka, Hideaki Kasai, Hiroshi Nakanishi, Ayao Okiji
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2247-2252
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We study effects of an oxygen vacancy on the electronic state of the CuO2 plane in the normal state, on the basis of the d-p model. We calculate the local density of states at copper sites and oxygen sites around the px-oxygen vacancy, at T=Tc. The spatial distribution has a shape which oscillates along the diagonal directions, reflecting the form of the Fermi surface. We find that another gentle oscillation along the X axis appears in the local density of states of d- and px-electron, while disappears in that of py-electron due to the crystal structure.
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  • Hiroshi Yoshie, Eiji Hirachi, Hiroshi Honda, Wataru Takahashi, Yasushi ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2253-2256
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The nuclear magnetic resonance of 59Co nuclei in magnetic domains of Ce(Co1-xFex)4B (0≤ x≤ 0.20) has been measured under external magnetic fields up to 5 T at 4.2 K. Spin reorientation was observed, which is a change in the magnetization direction from that parallel to the c-axis below Fe concentration x=0.1 to that perpendicular to the c axis above x=0.20. The 59Co hyperfine field at the 6i site in Ce(Co1-xFex)4B is divided into two above x=0.20 associated with the spin reorientation.
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  • Ryousuke Shiina
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2257-2262
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The quadrupolar phase transition of CeB6 in high magnetic fields is studied by mapping the multipolar RKKY model to an effective orbital Hamiltonian. The fluctuation correction to the mean-field solution of the effective Hamiltonian is analyzed as a function of the strength and the direction of the magnetic field. The results are combined with the low-field analysis of the previous paper to obtain a possible high-field phase diagram for CeB6.
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  • Ashis Bhattacharjee, Yasuhiro Nakazawa, Hayao Kobayashi, Michio Sorai
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2263-2267
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    AC magnetic susceptibility (χAC-iχ′′) of {NBu4[FeIIFeIII(ox)3]} was measured in the 4-50 K range for different frequencies (0.1-1000 Hz). Both of the χ(T) and χ′′(T) plots showed two peaks in two temperature regions: 4-33 K and 33-50 K. The χ(T) and χ′′(T) peaks in the 33-50 K range can be associated with the magnetic phase transition at the Néel temperature (43.3 K). However, the χ(T) peak in the 4-33 K range was found to be shifted towards lower temperature from 15.5 K to 13.5 K with increasing frequency, accompanied by a decrease in peak height. The fractional relative change in the peak temperature per decade change in frequency was calculated. The χ′′(T) in the 4-33 K range exhibited a broad peak around 25 K. The frequency dependence of χ(T) and χ′′(T) in the 4-33 K range occurred in the region where the irreversibilities in the ZFC (zero-field-cooled)-FC (field cooled) susceptibilities appeared. In this temperature range, a small heat capacity anomaly was detected and the negative magnetization effect took place in earlier reports. The wait-time dependence study of ZFC magnetization revealed an aging phenomenon. The frequency dependent peaks observed in the AC susceptibility and the aging phenomenon occurred below the Néel temperature might be indicative of the existence of a spin glass-like state in the present material at low temperatures.
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  • Ae Ran Lim, Tae Jong Han, Jae Kap Jung, Hyun Min Park
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2268-2270
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The proton NMR line width and spin-lattice relaxation times for the NH4HSO4 single crystal were studied over a wide temperature range. The proton spin-lattice relaxation time for NH4HSO4 has a minimum value, which is attributed to the effect of molecular motion. The 1H spin-lattice relaxation times occurring in phases I and III are attributed to the same motions of NH4 ions. The activation energies for the reorientation motions in phases I and III are 0.98 and 4.61 kcal/mol, respectively. In phase II, the activation energy is 5.92 kcal/mol. The large change in the activation energy between phases I and II indicates that the NH4 groups are affected during this transition; however, the motion of the NH4+ ions between phases II and III does not play an important role in the phase change.
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  • Hiroyuki Ishii, Kozo Okazaki, Atsushi Fujimori, Y. Nagamoto, T. Koyana ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2271-2275
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We have studied the electronic structure of the skutterudite compounds CoSb3 and Co(Sb0.96Te0.04)3 by photoemission spectroscopy. Valence-band spectra revealed that a significant amount Sb 5p states are present near the Fermi level and are hybridized with Co 3d states just below it. The spectra are well reproduced by the band-structure calculation, suggesting that the effect of electron correlations is not important. When Te is substituted for Sb and n-type carriers are doped into CoSb3, the spectra are shifted to higher binding energies as described by the rigid-band model. From this shift and the free-electron model for the conduction and valence bands, we have estimated the band gap of CoSb3 to be 0.03-0.04 eV, consistent with transport measurements. Photoemission spectra of RhSb3 have also been measured and revealed expected similarities to and differences from those of CoSb3. Unusual temperature dependence has been observed for the spectra of CoSb3 and RhSb3 in the vicinity of the Fermi level.
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  • Masaya Nagai, Makoto Kuwata-Gonokami
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2276-2279
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We study on the sub-picosecond mid-infrared pump-probe reflection spectroscopy on photo-doped Si and GaAs. We discover experimentally that spectral profile of metallic reflection near the plasma resonance brings us the information on both of carrier density and spatial inhomogeneity. The red-shift of the plasma resonance indicates the reduction of carrier density near the surface, while the broadening of plasma resonance is caused by the steep spatial gradient of carrier density rather than carrier damping. The spectral profile of reflection in Si shows that the carrier diffusion dominates the spatial-temporal evolution of the photo-doped carriers.
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  • Ken-ichi Hino
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2280-2285
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Fano resonance profiles of excitons in an asymmetric double quantum well of 165-Å-GaAs/14-Å-AlAs/48-Å-GaAs and in a shallow 200-Å-thick single quantum well of GaAs/Al0.045Ga0.955As are calculated with high accuracy by solving a multi-channel scattering problem based on the excitonic 4 × 4-Luttinger Hamiltonian. Anomalous excitons caused by oblique transitions between the different quantum wells of the asymmetric double quantum well system are found. Hole subband mixing is crucial in these novel exciton states and just Coulomb coupling without this effect does not suffice for pronounced peaks obtained by the calculations. Moreover, odd-parity light-hole exciton states are examined in both quantum well systems concerned here, and it is shown that these also manifest themselves as conspicuous peaks due to the hole subband mixing. Such two types of exciton Fano resonance are successfully identified as peaks observed in the existing experiments for high-resolution spectra.
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  • R. B. Chen, F. L. Shyu, C. P. Chang, M. F. Lin
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2286-2289
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    Optical properties of single-walled boron nitride nanotubes have been studied theoretically. The dielectric functions calculated from the gradient approximation and the random-phase approximation are consistent with each other. The imaginary and the real parts of the dielectric function, respectively, exihibit the special peaks and dips. The strong e-h absorption peaks at ω < 4 γ0 comes from the π band and the others from the π + σ bands (γ0 is the nearest-neighbor interaction of 2pz orbitals). Such single-particle excitations also induce the peak structures in the reflectance spectrum. On the other hand, the loss function shows the prominent π- and π+σ-plasmon peaks. The π and π+σ plasmons (collective excitations) reveal themselves in the reflectance spectrum as strong and abrupt edges. The optical properties are affected by the polarization direction and the nanotube radius, but not the chiral angle. The calculated results could be experimentally checked with optical spectroscopies or EELS.
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  • Z. F. Li, B. X. Liu
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2290-2294
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The Ni-W multilayered films were designed and prepared to have a same total thickness but different layer numbers. The as-deposited films were then subjected to ion irradiation at room temperature and the experimental results showed that the thickness of single layers could significantly influence the alloying behavior emerged in the Ni-W films. When the single layer thickness was about 4-6 nm, amorphous phases were only obtained in the W-enriched multilayers at relatively high irradiation doses. Whereas the single layer thickness was down to 2-3 nm, amorphous phases were formed in both W-enriched and Ni-enriched multilayers at relatively low irradiation doses. In thermodynamic modeling, a Gibbs free energy diagram was constructed applying Miedema's model, and the calculated results were in good agreement with the experimental observations. Besides, irradiation induced amorphization is also discussed in terms of the physical characteristics of the involved far-from-equilibrium process.
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  • Norihiko Takahashi, Kyozaburo Takeda
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2295-2303
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We have theoretically investigated a possible spin ground-state in the heteroatom-eaten π conjugated system. Deficient π electrons in this system function as a spin hole for the ground spin-configuration. The various spin ground-states, such as singlet (lower) and triplet (higher) ones are theoretically predicted. Furthermore, these π spin holes have a potential to induce a singlet-triplet instability.
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  • Balswaroop Bhatt, David Owen, Rameshwar P. Jaju
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2304-2309
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The present paper extends previous work by Bhatt et al. [J. Phys. Soc. Jpn. 69 (2000) 3133] referred as Part I. It deals with the switching effect of predation on prey species living in two habitats when the predatory rates are arbitrary. The predator feeds preferentially on the more abundant habitats population. Two habitats have been separated by a barrier so that the prey species is able to disperse among them at some cost of the population. The stability analysis has been carried out for non-zero equilibrium values. Using the conversion rate of the prey to predator as a bifurcation parameter, necessary and sufficient conditions for a Hopf bifurcation to occur have been derived. Two particular cases of predatory rates, namely, (i) multiplicative case and (ii) exponential case have been derived.
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  • Hiroki Tutu
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2310-2315
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The mound development of the cellular slime mold amoebae Dictyostelium discoideum is studied with an interface kinetic model for the height of cell layers. As a competitive role for the chemotaxis, we compare two types of curvature relaxations; the surface relaxation induced by cell-substrate affinity (model A), and that comes from a cell-cell adhesive effect (model B). It is found that both models are characterized by the growth law for the maximum mound height. Based on a self-similarity scaling hypothesis for the spatial structure of streaming pattern, we suggest a scaling law for the growth of mound-height hmax ∼ t1-1/α+β/α with α = 2 (4) for the model A (B) and a number 0 ≤ β < 1.
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  • Masahiro Nakagawa
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2316-2325
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    In this paper we shall investigate the statistical property and the memory capacity of the chaotic autoassociation memory. The present artificial neuron model is properly characterized in terms of a time-dependent sinusoidal activation function to involve a transient chaotic dynamics as well as the energy steepest descent strategy. It is elucidated that the present neural network has a remarkable retrieval ability beyond the conventional models with such a monotonous activation function as sigmoidal one. This advantage is found to result from the property of the analogue periodic mapping accompanied with a chaotic behaviour of the neurons as well as the symmetry of the dynamic equation which may be shown in the invariant measure determined by the Frobenius-Perron equation.
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  • Shin-ichi Tadaki, Katsuhiro Nishinari, Macoto Kikuchi, Yuki Sugiyama, ...
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2326-2334
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    We observe the congested traffic flow in Tomei Expressway, a Japanese expressway linking Tokyo with Nagoya. Congestion occurs at the upper stream of a traffic blockade, Nihonzaka tunnel, in contrast to preceding observations at the upper stream of an on-ramp. The flow on the fast lane is congested more severely than on the slow lane. The flow on the fast lane, however, almost always exceeds the one on the slow lane. The observed congested flow is stable and the average velocity on both lanes strongly correlated.
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  • Yoshihiro Ishibashi, Minoru Fukui
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2335-2338
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The bottleneck effect due to multiple gates on the traffic flow on one-dimensional roads is discussed. The local occupation probability method is adopted. Along with several concrete expressions of the flow, the symmetry aspect regarding the exchange of the order of the gates will be mentioned. Another interesting symmetry regarding the overall car density will be also mentioned for the cases where the separation of the gates is comparable with the length of the cyclic roads.
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  • Akihiro Sasoh, Taku Ohara
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2339-2347
    Published: 2002
    Released on J-STAGE: April 25, 2003
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    The shock wave relation for two-lane traffic flow with lane changes has been formulated. The post-shock condition is obtained by adding a source term which accounts for the lane changes to the continuity equation. The shock velocity, and the corresponding post-shock conditions are obtained from matching relation between the lanes. The source term is affected by the transverse velocity for the lane change. If the lane to which cars intend to change is not crowded and lane change is permitted without restriction, the source term linearly increases with increasing the transverse velocity. However, if the lane change motion is limited due to crowded traffic, the lane change rate is decreased; the traffic flow gets involved in more complicated shock wave dynamics. In any case, shock polar analysis eases the derivation and the comprehension of the matched shock relation.
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  • Jing-Bo Chen
    Article type: General Physics
    Subject area: Mathematical methods in physics.
    2002 Volume 71 Issue 9 Pages 2348-2349
    Published: 2002
    Released on J-STAGE: April 25, 2003
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