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Satoshi Tsujimoto, Ryogo Hirota
専門分野: Mathematical methods in physics.
1998 年 67 巻 6 号 p.
1809-1810
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We propose an ultradiscrete KdV equation in a coupled form and a Miura transformation relating it to the ultradiscrete Lotka-Volterra equation. Moreover we show that the ultradiscrete KdV equation under an appropriate boundary condition is equivalent to Takahashi's soliton cellular automaton.
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Kenji Imai
専門分野: Mathematical methods in physics.
1998 年 67 巻 6 号 p.
1811-1813
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Some (1+1) dimensional soliton equations covariant with respect to the Darboux transformation are derived systematically from the gl(2, C) linear system, which include the dark type nonlinear Schrödinger equation, the sinh-Gordon equation, the noncompact Heisenberg equation, the Harry-Dym equation, the integrable coupled dispersionless equations and new soliton equations.
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Yoshimasa Matsuno
専門分野: Mathematical methods in physics.
1998 年 67 巻 6 号 p.
1814-1817
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The solution of the Benjamin-Ono equation is presented for a stepinitial condition. This solution models the evolution of an internal borewave in deep fluids. The Whitham modulation theory is used toconstruct the asymptotic solution which provides an accurate description ofthe wave evolution in the small dispersion limit. It is shown that theinitial step profile evolves into a train of solitary waves and the total number of created solitary waves increases without limit in proportion to time. The amplitude of theleading solitary wave is then found to be four times the amplitudeof the initial step.
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Tsuyoshi Hondou
専門分野: Statistical physics and thermodynamics.
1998 年 67 巻 6 号 p.
1818-1821
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We consider the energetics of a multistable system driven bya nonthermal fluctuation. An analytical expression of the efficiency of energy transformation of fluctuation into coherent energy is derivedfor a process driven by a dynamic noise, in an overdumping limit of the system.The method is applied for the calculation of chaotic noise.
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Tetsuo Ohmi, Kazushige Machida
専門分野: Statistical physics and thermodynamics.
1998 年 67 巻 6 号 p.
1822-1825
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The Bogoliubov theory is extended to a Bose-Einstein condensation withinternal degrees of freedom, realized recently in
23Na gases whereseveral hyperfine statesare simultaneously cooled optically. Starting with a Hamiltonianconstructed from general gauge and spin rotation symmetry principles, fundamental equations for condensate are derived. The ground state wheretime reversal symmetry is broken in some cases and low-lying collectivemodes, e.g. spin and density wave modes, are discussed. Novel vortexas a topological defect can be created experimentally.
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Yoshihiro Murayama, Masaki Sano
専門分野: Mechanics, elasticity, and rheology.
1998 年 67 巻 6 号 p.
1826-1829
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Probability distribution functions (PDFs) of velocity fluctuations in a 2-d vibrated bed of granular materials are studied numerically using a viscoelastic particle model. The PDF of horizontal velocity is closely related to the packing density (P.D.) of particles. At low P.D., particles move randomly and their motions are uncorrelated, and the distribution is Gaussian. At high P.D., particle motions are correlated, and the PDF becomes a non-Gaussiandistribution with an exponential tail. The flatness factor of velocity fluctuations is calculated as a function of P.D., and continuous transition from Gaussian to non-Gaussian distribution is observed.
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Iwao Hosokawa, Shin–ichi Oide, Kiyoshi Yamamoto
専門分野: Fluid dynamics.
1998 年 67 巻 6 号 p.
1830-1833
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The one-dimensional (1D) surrogates of scalar dissipation rate as well as energy dissipation rate are often used in place of the true ones in investigations relevant to the Obukhof-Corrsin spectral form and the joint-multifractal nature of isotropic turbulence with an advected scalar. As a result of direct numerical simulation, it turns out that the surrogates cause a similar fundamental change in statistics to that caused by the 1D surrogate of energy dissipation rate in the treatment of the Kolmogorov similarity variable. The conditional and unconditional probability densites of the scalar similarity variable built from the true energy and scalar dissipations are never bimodal and always nearly Gaussian.
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Hervé Michallet, Eric Barthélemy
専門分野: Fluid dynamics.
1998 年 67 巻 6 号 p.
1834-1836
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Earlier work [Funakoshi and Oikawa: J. Phys. Soc. Jpn. 55 (1986) 128] has shown that a numerical approach based on Fourier series is relevant for describing long waves propagating on the interface of a two-fluid system (densities ρ
0 and ρ, ρ
0<ρ) in the case where the upper boundary is rigid. This method which was improved to take into account a free surface, is used to compute long waves for ρ
0/ρ=0.1. For this ratio, generalized long internal wave solutions are obtained, which exhibit a resonant behaviour between a baroclinic pulse-like wave and a barotropic short wave.
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Tomohiro Seko, Tadao Ishii
専門分野: Thermal properties of condensed matter.
1998 年 67 巻 6 号 p.
1837-1839
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Molecular dynamics simulation is carried out on β -AgI, and negative expansion of the c-axis is investigated. It is explicitly confirmed that this anomalous c-axis negative expansion is directly related to the excitation of defects as proposed in the theory of cluster-distortion coupling model. This defect-induced c-axis distortion is quite consistent with the experimental results.
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Tomoya Isoshima, Kazushige Machida
専門分野: Quantum fuids and solids: liquid and solid helium.
1998 年 67 巻 6 号 p.
1840-1843
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The entire excitation spectrum within thePopov approximation of the Bogoliubov theory for a cylindrically symmetricBose-Einstein condensate radially trappedby a harmonic potential is calculated.The full dispersion relation and the temperature dependenceof its zero sound mode propagating along the axial directionare evaluated in a self-consistent manner.The sound velocity is shown to depend not only on the peak density, but also on the axial area density.Recently conducted sound velocity experiment on a gas of Na atomsis discussed in light of the present theory.
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Ryu Takayama, Osamu Sakai
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
1844-1847
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We study how the Kondo effect is affected by the Coulomb interaction between conduction electrons on the basis of a simplified model. The single impurity Anderson model is extended to include the Coulomb interaction on the nearest-neighbour ligand orbital. The excitation spectra are calculated using the numerical renormalization group method.The effective bandwidth on the ligand orbital, D
eff, is defined to classify the state. This quantity decreases as the Coulomb interaction increases. In the D
eff > Δ region, the low energy properties are described by the Kondo state, where Δ is the hybridization width. As D
eff decreases in this region, the Kondo temperature T
K is enhanced, and its magnitude becomes comparable to Δ for D
eff -- Δ. In the D
eff < Δ region, the local singlet state between the electrons on the f and ligand orbitals is formed.
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Hitoshi Seo, Hidetoshi Fukuyama
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
1848-1851
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The origin of the spin gap behavior in the low-temperature dimerized phase of θ-(BEDT-TTF)
2RbZn(SCN)
4 has been theoretically studied based on the Hartree-Fock approximation for the on-site Coulomb interaction at absolute zero. Calculations show that, in the parameter region considered to be relevant to this compound, antiferromagnetic ordering is stabilized between dimers consisting of pairs of molecules coupled with the largest transfer integral. Based on this result an effective localized spin 1/2 model is constructed which indicates the existence of the frustration among spins. This frustration may result in the formation of spin gap.
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Hideki Abe, Hideaki Kitazawa, Haruyoshi Aoki
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
1852-1855
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The de Haas-van Alphen (dHvA) effects have been studied in an antiferromagnetic heavy Fermion compound CeRh
2Si
2 with fields in the high symmetry planes of (001), (110) and (010). More than twenty separate dHvA branches have been observed ranging from 33, T to 9170, T; most of the branches are observed in limited regions of the field directions. The largest cyclotron mass obtained is 4.4, m
0, which is rather small compared to the estimate from the Sommerfeld coefficient. This implies that heavy Fermi surfaces remain uncovered.
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Marcus Metzler, Imre Varga
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
1856-1859
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We numerically investigate the spectral statistics of quasienergies for the unitary network operator U of the Chalker--Coddington network. The shape of the level spacing distribution as well the scaling of itsmoments is compared to known results for quantum Hall systems. We alsodiscuss the influence of multifractality on the tail of the spacing distribution.
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Tomosuke Aono, Mikio Eto, Kiyoshi Kawamura
専門分野: Electronic transport in condensed matter.
1998 年 67 巻 6 号 p.
1860-1863
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The conductance through two quantum dots connected in seriesis studied below the Kondo temperature, based onthe slave boson formalism of the Anderson model.The transport properties are characterized bythe ratio of the magnitude of the tunneling coupling betweentwo dots to the width of the level broadening.When the ratio is less than unity, the Kondo resonant states are formed between each dot and an external lead, and the conductance is determined by the hopping betweenthe two resonant states.When the ratio is larger than unity, these Kondo resonances are split intothe bonding and antibonding peaks, which are located below and above the Fermi levelin the leads, respectively, for low gate voltages.As a result, the conductance is suppressed.The conductance has a maximum of 2 e^2/h when the bondingpeak is matched with the Fermi level by controlling the gate voltage.
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Hirokazu Tsunetsugu, Masatoshi Imada
専門分野: Electronic transport in condensed matter.
1998 年 67 巻 6 号 p.
1864-1867
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Drude weight of optical conductivity is calculated at zero temperature by exact diagonalization for the two-dimensional t-J model with the two-particle term, W. For the ordinary t-J model with W=0, the scaling of the Drude weight D ∝ δ
2 for small doping concentration δ is obtained, which indicates anomalous dynamic exponent z=4 of the Mott transition.When W is switched on, the dynamic exponent recovers its conventional value z=2. This corresponds to an incoherent-to-coherent transition associated with the switching of the two-particle transfer.
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José V. Alvarez, José González, Francisco Guinea, ...
専門分野: Superconductivity.
1998 年 67 巻 6 号 p.
1868-1871
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We apply a renormalization group approach to the determination of the phase diagram of the t-t
′ Hubbard model at the Van Hove filling, as function of t
′ / t, for small values of U / t.The model presents ferromagnetic, antiferromagnetic and d-wavesuperconducting phases. Antiferromagnetism and d-wavesuperconductivity arise from the same interactions, and competein the same region of parameter space.
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Hiroshi Shimahara
専門分野: Superconductivity.
1998 年 67 巻 6 号 p.
1872-1875
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Effects of the phase fluctuations of the order parameter on the stability of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states are examined in exactly two-dimensional (2D) type-II superconductors with cylindrically symmetric Fermi surface on the basis of a generalized Ginzburg-Landau theory. It is found that for the FFLO states with oscillations in a single direction, not only the long-range order but also quasi-long-range order (QLRO), which is characterized by a power law decay of the order parameter correlation function, is suppressed by the phase fluctuations at any finite temperatures. On the other hand, for the FFLO states with order parameter structures such as triangular and square lattices, it is shown that the QLRO is possible as the uniform BCS state. Systems with anisotropy in the Fermi surface and pairing are also discussed.
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Naoto Nagaosa, Shuichi Murakami
専門分野: Magnetic properties and materials.
1998 年 67 巻 6 号 p.
1876-1878
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We theoretically study the lattice instability in the spin-gap systems under a magnetic field. When the magnetic field is larger than a critical value h
c1, the spin gap collapses and the magnetization phenomenon occurs.We found that lattice distortion occurs in the spin ladder at an incommensurate wave vector corresponding to the magnetization, while it does not occur in the Haldane system.At low temperatures the magnetization curve shows a first order phase transition with this lattice distortion.
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Keiichi Koyama, Tsuneaki Goto, Hironobu Fujii, Nao Takeshita, Nobuo Mo ...
専門分野: Magnetic properties and materials.
1998 年 67 巻 6 号 p.
1879-1882
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Magnetization and electrical resistivity measurements have been performed for Ce
2Fe
17 under high pressures of up to 1.2, GPa and high magnetic fields of up to 17, T. At ambient pressure, two antiferromagnetic phases appear at T
N=215, K and T
c=125, K with decreasing temperature. A metamagnetic transition from the antiferromagnetic to the forced ferromagnetic state is observed at 4.2, K. The transition field increases with increasing pressure, whereas the saturation magnetization, saturation field and T
N decrease. New magnetic phases, which are different from the two antiferromagnetic and forced ferromagnetic phases, are observed under high pressure and high magnetic fields.
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Hiroyuki Ohsumi, Keisuke Tajima
専門分野: Magnetic properties and materials.
1998 年 67 巻 6 号 p.
1883-1885
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Lattice modulations induced by magnetic structures in Ho have been studied by X-ray diffraction under magnetic field in a temperature range between 30, K and 110, K. Several satellite reflections caused by the lattice modulations have been observed along the c
*-axis only in a helifan phase. The range of the helifan phase could be determined accurately from the observation of the satellites which show different behavior between increasing and decreasing magnetic field processes.
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Kum–Bae Kim, Kwang–Sei Lee, Cheol Eui Lee
専門分野: Dielectric properties and materials.
1998 年 67 巻 6 号 p.
1886-1889
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The low-temperature II-III phase transition of TlH_2PO_4 (ferroelastic in phase II) at 230 K(T
c2) was studied by a polarizing microscope between 300 and 80 K. Despite the II-III phase transition at T
c2, the two kinds offerroelastic domain structures with the (100) and/or (001) and (201) domainboundaries werestill observed below T
c2 and were nearly temperature-independent.No new domain structures corresponding toantiferroelectric or ferrielectricorientation states were observed in phase III. The possible intermediatestructural phasetransition near 130 K suggested by vibrational spectroscopic study [B.Pasquier et al.:Chem. Phys. 171 (1993) 203] was not detected. The transition at T
c2 without opticallydetectable new domains indicates that the monoclinic crystal system of thephase II persistsin phase III from 300 to 80 K and that the nature of the II-III phasetransition of TlH_2PO_4 is not ferroic, but is nonferroic.
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Kaizo Nakamura, Minoru Shigoku, Kanji Kondo, Osamu Arimoto
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 年 67 巻 6 号 p.
1890-1893
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
A new type of experiment was performed to investigate the effective nonradiative process causing the fast decay of the forbidden 1s triplet exciton luminescence with polarization E // b in β-ZnP
2. Excitation spectra of anti-Stokes 1s singlet exciton luminescence with E // c have been measured by varying the excitation energy with E // b around the 1s triplet exciton absorption peak which is located about 2 meV below the singlet exciton luminescence. A sharp peak of excitation efficiency has been confirmed at the triplet exciton resonance for the first time. Temperature dependence of the excitation peak is in accordance with the thermal behavior of the singlet exciton polariton luminescence both from lower- and upper-branches. This anti-Stokes acoustic phonon scattering of triplet exciton into singlet states is one of the main causes of the short lifetime of triplet exciton in β-ZnP
2. Spin flip mechanism is briefly discussed.
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Itaru Hataue
専門分野: Mathematical methods in physics.
1998 年 67 巻 6 号 p.
1895-1911
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
In the present paper the structure of dynamical systems which were produced by discretizing the two-dimensional Burgers' equation is analyzed. An analytical approach and several numerical nonlinear dynamics approaches such as bifurcation diagram and so on are applied in order to discuss the structure of asymptotic numerical solutions. In particular, the dependence of the nonlinear structure of the numerical solutions on the temporal discretization parameter (Δ t) are considered. Furtheremore, these numerical approaches are applied to the analyses of the results of more practical two-dimensional CFD (Computational Fluid Dynamics) calculations. The subsonic flow around a circular cylinder is selected as a model and the dependence of the structure of dynamical systems which are given from the computed time series of the drag coefficient on the temporal discretization parameter is discussed.
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Elman M. Shahverdiev
専門分野: Mathematical methods in physics.
1998 年 67 巻 6 号 p.
1912-1917
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Chaos synchronization in some autonomous dynamical systems of high dimensionality is studied in general case. A simple method to make all Lyapunov exponents negative is proposed. As an example chaos synchronization in both classical and modified Lorenz models is investigated. A comparison between the modified Lorenz model and classical Lorenz system is conducted. The influence of the additional to classical Lorenz system terms which intensifies the vorticity and stabilizes the temperature field on the chaos synchronization is studied. It has been established that this influence depends on the sign and magnitude of these terms.
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Shin–ichi Sasa, Tatsuo Shibata
専門分野: Statistical physics and thermodynamics.
1998 年 67 巻 6 号 p.
1918-1923
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We extend the Langevin dynamics so that particles can be exchanged with a particle reservoir. We show that grand canonical ensembles are realized at equilibrium and derive the relations of thermodynamics for processes between equilibrium states.As an application of the proposed evolution rule, we devisea simple model of Brownian motors driven by particle exchange.
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Minoru Yoshimoto, Shigeru Kurosawa, Hiroyuki Nagashima
専門分野: Statistical physics and thermodynamics.
1998 年 67 巻 6 号 p.
1924-1929
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The mechanism and the characteristics of appearance of order in chaos with Gaussian white noise are investigated in the logistic map. This order (noise-induced order) appears as the constancy of the topological entropy and the decrease of the Kolmogorov entropy. Analysis of n-times iterated map reveals that “noise-induced order” is caused by the increase of the length of the laminar region and the subsequent change of the invariant density, where “local structure” overcomes “global structure”. We find that “noise-induced order” is accelerated by an increase of the noise period, and takes place only in chaos near period-five and -under windows.
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Yukiko Umeno, Masahiro Shiroishi, Miki Wadati
専門分野: Statistical physics and thermodynamics.
1998 年 67 巻 6 号 p.
1930-1935
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The integrability of the one-dimensional (1D) fermion chain model is investigated in the framework of the Quantum Inverse Scattering Method(QISM). We introduce a new R-operator for the fermion chain model, which is expressed in terms of the fermion operators.The R-operator satisfies a new type of the Yang-Baxter relation with fermionic L-operator. We derive the fermionic Sutherlandequation from the relation, which is equivalent to the fermionic Lax equation. It also provides a mathematical foundationof the boost operator approach for the fermion model.In fact, we obtain some higher conserved quantities of the fermion model using the boost operator.
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Takasi Endo
専門分野: Measurement science, general laboratory techniques, and instrumentation systems.
1998 年 67 巻 6 号 p.
1936-1938
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
An estimator is proposed for the location parameter of the Cauchy distribution.The estimator gives the efficient estimation for large sample sizes.
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Kei Odai, Hideki Ono, Hideo Suzuki
専門分野: Electronic structure of atoms and molecules: theory.
1998 年 67 巻 6 号 p.
1939-1947
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Considering a system composed of even valence-shell electrons and formulating a CI calculation with inclusion of all the singly-excited and the simultaneous doubly-excited singlet configurations of the system, we extend our previous INDO theory of the relation between bond length and bond order for the ground-state singlet configuration. \cite{rf:1}It is thus shown that the previous relation for the ground-state singlet configuration can generally be applied to any singlet state by replacing every bond order of the ground-state singlet configuration with that of the ground or the excited singlet-state.It is also pointed out that bond orders of each singlet state can correctly be calculated by our projection-operator method.
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Jong–Hoon Huh, Yoshiki Hidaka, Shoichi Kai
専門分野: Fluid dynamics.
1998 年 67 巻 6 号 p.
1948-1954
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The experimental study on transition processes of the spatio-temporal chaos (STC) as well as periodic patterns in homeotropically aligned nematicliquid crystals is reported under superimposing magnetic fields withelectric fields. The strong dependence of the threshold for STC on thestrength of magnetic fields is observed above certain normalized voltageε
th, where the two types of STC are found out below andbeyond the characteristic value of the magnetic field H
* = 620 G.The periodic patterns were observed for the normalized voltageε below ε
th. Below H
* the soft-modeturbulence appears due to the Goldstone mode related to a continuousrotational-symmetry which can be controlled by the application of H.Beyond H
*, the conventional STC called defect turbulence, which issimilar to STC in the planar system, is observed.
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Hiroshi Amemiya
専門分野: The physics of plasmas and electric discharges.
1998 年 67 巻 6 号 p.
1955-1962
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The criterion for the formation of a stable ion sheath is considered for an arbitrary electron energy distribution function F(E) to estimate the ion flux from a plasma containing negative ions. The cases of Maxwellian, Druyvesteyn and other energy distributions are discussed for comparison. As an application of the present method, the diagnostic of negative ion containing plasmas by using the kinetic energy distribution and probe characteristics is considered. The range of applicability of the present model is given. As another application, the ion current densities extractable from an ion source are estimated.
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Satoru Tanaka, Makoto Ichimura, Seiichi Takayama, Masaaki Inutake, Shi ...
専門分野: The physics of plasmas and electric discharges.
1998 年 67 巻 6 号 p.
1963-1967
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Validity of averaged minimum-B configuration onMagnetohydrodynamics (MHD) stability of the GAMMA10 tandem mirror arestudied in the ion cyclotron range of frequency (ICRF)-heated, hot ionmode plasma. It has been observed that the plasma can not be sustainedmostly owing to the flute interchange mode when the high power ICRF isapplied for the central cell ion heating. As the ratio of the centralcell beta to the anchor cell beta increases, the amplitude of the fluteinterchange mode increases. The anchor cell plasma is also sustained bythe another ICRF source in the central cell. The flute type MHDinstability in GAMMA10 is well controlled by the phased ICRF antennas inthe central cell.
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Noriko Koide, Masatomo Sato
専門分野: The physics of plasmas and electric discharges.
1998 年 67 巻 6 号 p.
1968-1972
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
In dusty plasmas, the fluctuation of charge on dust grains may have a significant influence on collective phenomena in the plasma. We study this dust charging effect on the electrostatic drift flow in dusty plasmas paying particular attention to the formation of quasi-stationary coherent structures. Two regimes of different time scales, the ion-drift regime and the dust-drift regime of much lower frequency, are considered by deriving for each regime a pair of coupled equations describing the temporal change of the stream function of drift flow and the dust-charge fluctuation. For both regimes, the current to dust grains must be small enough to yield a quasi-stationary flow. In the case of ion-drift flow, the small current is consistent with the low level excitation of the charge fluctuation, giving no appreciable influence on the coherent structure. In dust-drift flow, the charge fluctuation with a finite amplitude may behave in phase with the potential, acting to reduce the increase of the propagation speed of coherent vortices with the dust density reported earlier without taking account of the dust-charging effect.
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Naoko Matsushita, Takao Ohta
専門分野: Equations of state, phase equilibria, and phase transitions.
1998 年 67 巻 6 号 p.
1973-1981
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We carry out computer simulations of a structural phase transitionbetween a hexagonal symmetry and a square symmetry in two dimensions. Our model is a partialdifferential equation which admits a periodic array of domains inequilibrium. The kinetics of the structural transition is studiedby analyzing the scattering function of the domain structures andby extracting the time--dependence of the volume fraction of oneof the structures.
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Tadashi Muranaka, Yasuaki Hiwatari
専門分野: Thermal properties of condensed matter.
1998 年 67 巻 6 号 p.
1982-1987
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The dynamical properties of the supercooled liquids and glasses have been studied via molecular dynamics (MD) simulation. We have found the spatial heterogeneity for long time region in our model fluids. The main factor of this heterogeneity originates from the linearly correlated jump motion, which changes the configurations even in the glass state. This type of jump motion is assisted by the linearly correlated motion which takes place in much shorter time region than that of the residence time of successive jump motions. Therefore it is concluded that the longtime heterogeneity in glasses originates from the linearly correlated motion in short time region.
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Takashi Nishikawa, Masaya Kato, Masaki Kanada, Toshihiko Fukamachi, Ka ...
専門分野: Thermal properties of condensed matter.
1998 年 67 巻 6 号 p.
1988-1993
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The specific heat C of CuNb
2O
6 with quasi-one-dimensional zig-zag spin S=1/2 chains has been measured in the temperature (T) range between 1.6, K and 40, K. For the orthorhombic phase, a sharp anomaly of C is observed at the antiferromagnetic transition temperature T
N-- 7.3, K. The T-dependence of C of the monoclinic phase, whose ground state has a spin gap, can be well described by the exchange parameters determined by fitting the magnetic susceptibility χ calculated for a model of a ferromagnetic-antiferromagnetic alternating bond to the experimentally obtained χ . The gap-value estimated from the low temperature behavior of C is about 21, K, which is also consistent with the ones obtained by other measurements. Results of the measurements of the magnetic susceptibilities χ and the specific heats C of M--Cu
1-xZn
xNb
2O
6 (0≤ x≤ 0.5) and their structural parameters are also presented.
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Kazuya Morikawa, Tooru Atake, Mitsuo Wada, Toshihisa Yamaguchi
専門分野: Thermal properties of condensed matter.
1998 年 67 巻 6 号 p.
1994-1998
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The heat capacity of Li
2Ge
7O
15 and LiNaGe
4O
9 was measured by adiabatic calorimetry between 13 and 300, K. A typical second-order type of anomaly due to the ferroelectric phase transition was observed at 282.4, K for Li
2Ge
7O
15 and at 121.6, K for LiNaGe
4O
9, and the entropy of transition was determined as 1.50 and 1.95, JK
-1mol
-1, respectively. Smoothed heat capacity values at selected temperatures and some other thermodynamic functions such as enthalpy, entropy and Gibbs energy were calculated from the experimental data and tabulated in a table.
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Takuo Ito, Hiroshi Kamimura
専門分野: Transport properties of condensed matter (nonelectronic).
1998 年 67 巻 6 号 p.
1999-2007
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
A model for the mechanism of ionic conductivity in the high temperature paraelastic phase of M
3H(XO
4)
2 [M=Rb, Cs, X=S, Se] type crystals is proposed. The key features of the conduction mechanism are the following; (1) two kinds of defect states, H
2XO
4(+e) and XO
4(-e), are formed thermally by breaking of a hydrogen-bond, (2) the H
2XO
4(+e) defect state and the XO
4(-e) defect state move coherently from an XO
4 tetrahedron to a distant XO
4 as the result of successive proton tunneling among hydrogen-bonds. The density of states and the mobility are calculated for the coherent motions of these defect states by the recursion method and the Kubo formula, respectively. The density of states shows the characteristic feature of the Bethe lattice, i.e., the twin peak structure due to self-similarity, while the conductivity is obtained as an order of a magnitude of 10
-3 Ω
-1cm
-1 at the ferroelastic transition temperature, consistent with experiments.
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Fuyuki Shimojo, Kozo Hoshino, Hideo Okazaki
専門分野: Transport properties of condensed matter (nonelectronic).
1998 年 67 巻 6 号 p.
2008-2011
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The proton diffusion in protonic conductor Y-doped SrCeO_3 is studied by an ab initio molecular-dynamics simulation.The probable migration paths of a proton and its dynamic process are investigated in detail.The microscopic mechanism of the proton diffusionis discussed in comparison with that in Sc-doped SrTiO_3.
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Junko Habasaki, Isao Okada, Yasuaki Hiwatari
専門分野: Transport properties of condensed matter (nonelectronic).
1998 年 67 巻 6 号 p.
2012-2017
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Long time (-- 1 ns region) molecular dynamics (MD) simulations of lithium metasilicate (Li_2SiO_3) and a mixed alkali silicate (LiKSiO_3) glass have been performed to confirm the mechanism of the “mixed alkali effect, ” which has been previously deduced from the shorter time behavior. In the Li_2SiO_3 system, long time behavior of lithium ion has been characterized by a component showing the enhanced diffusion (Lévy flight) due to cooperative jumps. The main diffusion and conduction processes of silicate glasses are not the single jumps but the cooperative jumps.The component taking the accelerated dynamics is found to be nearly absent in the mixed alkali system.Contributions of both temporal and spatial aspects for the particle dynamics are separated. The large change in the spatial parameters has been observed on mixing. Interception of the jump path due to other kinds of ion path suppresses the cooperative jump process.
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Yüksel Ufuktepe, Shin–ichi Kimura, Toyohiko Kinoshita, Kris ...
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
2018-2026
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Electronic structures of thulium monochalcogenides (TmS, , TmSe, , TmTe) were studied both experimentally and theoretically using a resonant photoemission technique in the photon energy range around Tm 4d edge (100--190, eV). The experimental results show a large resonant enhancement of 4f photoelectron emission around the 4d threshold with sharper multiplet structures than those reported before. The calculated results are in good agreement with the experimental ones both for divalent and trivalent features of Tm ions. We observed different types of valence structures for TmS, TmSe and TmTe compounds, due to change in mean valence. We have estimated the mean valence of each sample from absorption spectra and from off-resonant photoemission spectra. The meaning of these values is discussed as compared with those for the values obtained from the measurements of magnetic susceptibilities.
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Katsuyuki Matsunaga, Isao Tanaka, Hirohiko Adachi
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
2027-2036
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We have carried out first principles molecular orbital calculations on an interstitial Ag in AgBr and AgI, using the discrete variational (DV)-Xα method. Although AgBr and AgI are considered to be ionic compounds, Ag-4d orbitals are well admixed with anion-p orbitals in their valence band. In the presence of an interstitial Ag (Ag
i), an interstitial level appears within the band gap. The interstitial orbital is found to be more delocalized around the Ag
i in AgBr than in AgI. As a result, the interstitial level in AgBr reinforces the Ag
i-Ag covalent bond. The Ag
i-Ag covalent bond in AgBr is stronger than any other covalent bonds around the Ag
i. On the other hand, the Ag
i-Ag covalent bond in AgI is much weaker than the Ag-I bond at normal sites. Since the formation of strong Ag
i-Ag bond is essential for the agglomeration of Ag atoms, an Ag cluster can be formed easier in AgBr than in AgI.
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Masahiko Higuchi, Akira Hasegawa
専門分野: Electron states in condensed matter.
1998 年 67 巻 6 号 p.
2037-2047
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
A new formulation of a relativistic current- and spin-density functional theory is proposed. By choosing the charge density and the magnetization density as the two basic variables, a single-particle equation is derived in a form suitable to an isolated atom or ion. The effect of the orbital current is included implicitly through the spin-orbit interaction and explicitly through the Zeeman term in which the spin and the orbital angular momenta couple with an effective magnetic field. The effective magnetic field is given by the variation of the exchange and correlation energy functional with respect to the magnetization density which consists of the spin and the orbital angular momentum density, and should be determined self-consistently. The single-particle equation is applied to an atomic structure calculation for the trivalent ions of the lanthanide series, and the total spin and the orbital angular momenta are found to obey Hund's rules well.
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Kurt Hiebl
専門分野: Electronic transport in condensed matter.
1998 年 67 巻 6 号 p.
2048-2054
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
A detailed study of measurements of ac susceptibility χ
ac, electrical resistivity ρ and magnetoresistance of intermetallic compounds within the solid solution U
1-xY
xCu
2Si
2 (x=0, 0.5, 0.875, 1) crystallizing with the tetragonal ThCr
2Si
2 structure type is presented. Both samples, rich in uranium, undergo an antiferromagnetic to ferromagnetic transition, whereas the sample with dilute uranium concentration exhibits only antiparallel spinalignment as confirmed by the maxima of both the curves concerning the temperature dependence of the real and imaginary parts of χ
ac and the singularities of dρ /dT, respectively. YCu
2Si
2 is a temperature independent Pauli-paramagnet, and the ρ
(T) plot reflects a normal metallic behavior. The low temperature resistivity for the anisotropic ferromagnets can be described assuming an energy gap Δ in the spin wave energy spectrum. The resistivity of the dilute as well as the dense uranium concentrated samples studied in the paramagnetic state was found to be determined by an interplay of Kondo scattering and crystal-field (CF) effects; the groundstate of the uranium U
4+ ion with 5f
2 configuration is probably the pair of two closely spaced singulets Γ
1t--Γ
2t of the CF levels of the
3H
4 term. The magnetoresistivity, Δρ /ρ, at T=5, K is negative for UCu
2Si
2 according the reduction of the spin disorder resistivity with applied field in the ordered state. The yttrium rich sample reveals a weakly positive magnetoresistance due to the Lorentz force. Δρ /ρ for ferromagnetic U
0.5Y
0.5Cu
2Si
2 is weakly negative stemming from the large magnetocrystalline anisotropy (coercive field μ
0H>4, Tesla) and changes sign in external fields μ
0H>0.7, T.
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Chih–Kai Yang
専門分野: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 年 67 巻 6 号 p.
2055-2057
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
Using a streamlined computation scheme, an efficient calculation of the electronic structure of Cu(001) is achieved. The method employs the tight-binding linear muffin-tin orbitals and takes advantage of a matrix operation that greatly reduces the computation time. Coupled with a scaling self-consistent procedure, reasonable results including layer-resolved local density of states, dipole moment, and work function are obtained. The results also strongly suggest that one empty overlayer is enough for surface calculation and that at least six more layers below the intended surface layer are needed in order to have a convergent local density of states.
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Mamoru Sakaue, Hideaki Kasai, Ayao Okiji
専門分野: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 年 67 巻 6 号 p.
2058-2066
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
The effect of interband excitations on time-resolved two-photon photoemission from an adsorbate-surface system is investigated. The system is assumed to be composed of two subbands in the bulk and a localized state of the adsorbate, which is in resonance with the upper energy subband. In the two-photon photoemission process, first, an electron in the lower energy subband is excited into the localized state by the pump photon, and subsequently excited above the vacuum level by the probe photon. The first excitation can be divided into two processes, i.e., the direct and the indirect one involving the interband excitation. The excitation probability due to the latter process reaches a maximum at a certain photon energy because of momentum conservation. A two-photon photoemission spectrum shows a peak due to the indirect process at an energy position where the initial state is fixed, as well as one due to the direct process where the intermediate state is fixed. The maximum of the cross-correlation trace of the pump and probe pulses (the pump-probe delay dependence of the photoelectron intensity) at the former peak shows little shift compared to that at the latter one. The intensity of the peak due to the indirect process increases as the pulse duration is decreased.
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Takafumi Kita
専門分野: Superconductivity.
1998 年 67 巻 6 号 p.
2067-2074
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
This paper presents a powerful method to obtain flux-lattice solutionsof the Ginzburg-Landau equations in any external field.A key point lies in expanding the order parameter Ψin a basis consisting of the eigenstates ofthe magnetic translation operators in the mean flux density B.It is shown that retaining a few terms in the expansionprovides practically exact solutions over0 <~ B ≤ H
c2.Abrikosov's result near H
c2 is obtained hereas a lowest-order approximation.The method clarifies how the higher-Landau-level mixing growsas the field is decreased from H
c2.
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Takafumi Kita
専門分野: Superconductivity.
1998 年 67 巻 6 号 p.
2075-2083
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
This paper generalizesthe method of using the magnetic Bloch states to obtain flux-latticesolutions of the Bogoliubov-de Gennes equations.Developed by several groups, this method has had a limited applicability to the s-wave pairingand to high-κ materials where thespatial variation of the magnetic field may be neglected.It is extended here so that:(i) an arbitrary anisotropic pairing can be handled;(ii) the effect of the screening current can be taken into account.Hence the formalism will enable a fully microscopicdescription of various Abrikosov lattices in clean type-II superconductorsover H
c1 ≤ H ≤ H
c2.
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Tadashi Fukuhara, Satoshi Akamaru, Tomohiko Kuwai, Junji Sakurai, Kuni ...
専門分野: Magnetic properties and materials.
1998 年 67 巻 6 号 p.
2084-2088
発行日: 1998/06/01
公開日: 1999/10/01
ジャーナル
認証あり
We have measured the temperature dependence of the magnetic susceptibility, the electrical resistivity, the specific heat and the Hall coefficient on the pseudo-binary series Ce(Ni
1-xPd
x)
2Ge
2 (1.0≥ x≥ 0.0). The Néel temperature decreases monotonously from 5.1, K for CePd
2Ge
2 to 2.8, K for Ce(Ni
0.8Pd
0.2)
2Ge
2 with decreasing Pd concentration. For x≤ 0.1, the ground state is paramagnetic.
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