bluuebunny/crossref_metadata_2025 huggingface dataset:
TEMPERLEY-LIEB OPERATORS AND CRITICAL A-D-E MODELS
Authors: PEARCE Paul A.
Published: November 2004

A review is given of recent work connecting exactly solvable lattice models with Temperley-Lieb and Hecke algebras, Dynkin diagrams of simply-laced Lie algebras, conformal and modular invariance and Virasoro characters.
YANG-BAXTER ALGEBRAS, INTEGRABLE THEORIES AND BETHE ANSATZ
Authors: DE VEGA H.J.
Published: November 2004

The Yang-Baxter algebras (YBA) are introduced in a general framework stressing their power to exactly solve the lattice models associated to them. The algebraic Bethe Ansatz is developed as an eigenvector construction based on the YBA. The six-vertex model solution is given explicitly. The generalization of YB algebras to face language is considered. The algebraic BA for the SOS model of Andrews, Baxter and Forrester is described using these face YB algebras.

It is explained how these lattice models yield both solvable massive QFT and conformal models in appropiated scaling (continuous) limits within the lattice light-cone approach. This approach permit to define and solve rigorously massive QFT as an appropiate continuum limit of gapless vertex models.

The deep links between the YBA and Lie algebras are analyzed including the quantum groups that underly the trigonometric/hyperbolic YBA. Braid and quantum groups are derived from trigonometric/hyperbolic YBA in the limit of infinite spectral parameter.

To conclude, some recent developments in the domain of integrable theories are summarized.
CRITICAL SPIN-1 VERTEX MODELS AND O(n) MODELS
Authors: NIENHUIS Bernard
Published: November 2004

A method is presented by which critical and multicritical points of spin-1 (three-state) vertex models and classical O(n) models on two-dimensional lattices are determined. It is a straightforward generalization of the ideas that earlier led to the determination of critical points and critical exponents of a honeycomb O(n) model. On the square lattice the methods leads to tricritical as well as critical loci. For n=2 a larger critical manifold is found than for other values of n. At the critical and multicritical points thus produced the models turn out to be soluble. The method is applicable to O(n) models and spin-1 vertex models on any planar lattice.
CONFORMAL INVARIANCE IN ONE-DIMENSION AND A TWO-COMPONENT LOG-GAS
Authors: FORRESTER P.J. , ROSINBERG M.L.
Published: November 2004

Conformal invariance in one-dimension implies the correlation functions must be constant. It is demonstrated by an exact solution that all the correlations between like species in a two-component lattice gas with the logarithmic potential have the conformal invariance property at the metal- insulator transition. A further exactly solvable isotherm of the model system is studied and the corresponding density of zeros for the grand partition function is obtained explicitly. A phase transition along this isotherm can be induced by appropriate choice of the parameters.
DIFFERENTIAL EQUATIONS FOR QUANTUM CORRELATION FUNCTIONS
Authors: Its A.R. , Izergin A.G. , Korepin V.E. , Slavnov N.A.
Published: November 2004

The quantum nonlinear Schrödinger equation (one dimensional Bose gas) is considered. Classification of representations of Yangians with highest weight vector permits us to represent correlation function as a determinant of a Fredholm integral operator. This integral operator can be treated as the Gelfand-Levitan operator for some new differential equation. These differential equations are written down in the paper. They generalize the fifth Painlève transcendent, which describe equal time, zero temperature correlation function of an impenetrable Bose gas. These differential equations drive the quantum correlation functions of the Bose gas. The Riemann problem, associated with these differential equations permits us to calculate asymp-totics of quantum correlation functions. Quantum correlation function (Fredholm determinant) plays the role of τ functions of these new differential equations. For the impenetrable Bose gas space and time dependent correlation function is equal to τ function of the nonlinear Schrödinger equation itself, For a penetrable Bose gas (finite coupling constant c) the correlator is τ-function of an integro-differentiation equation.
SQUEEZING PHENOMENA IN INTERACTING ELECTRON-PHONON SYSTEMS
Authors: FEINBERG D. , CIUCHI S. , de PASQUALE F.
Published: November 2004

The molecular crystal model of electrons coupled to Einstein phonons is studied as a function of the two parameters: the coupling constant A and the ratio of the electron-phonon coupling energy to the phonon energy, denoted by α. Both the one-electron and the many-electron models are studied, starting (for the former) from the adiabatic limit and (for the latter) from the anti-adiabatic one. In the “multiphonon” regime α>1, the sharp crossover between quasi-free electrons (λ≪1) and small polarons (λ≫1) is investigated, emphasizing the anomalous lattice fluctuations which occur in the intermediate regime (λ≈1). These fluctuations are due to the band motion of the electrons strongly coupled to the lattice and are shown in turn to weaken the electron mass renormalization inherent to self-trapping. In a relevant part of the intermediate region the effective electron mass slowly increases with λ, due to a competition between the phonon dressing effect and the reduction of lattice momentum fluctuations. This reduction is reminiscent of squeezing phenomena occurring in quantum optics. In a gaussian approximation squeezed phonon states imply a dynamical phonon softening.
SYSTEMATIC APPROACH TO CRITICAL PHENOMENA BY THE EXTENDED VARIATIONAL METHOD AND COHERENT-ANOMALY METHOD
Authors: KAWASHIMA NAOKI , KATORI MAKOTO , TSALLIS CONSTANTINO , SUZUKI MASUO
Published: November 2004

A general procedure to study critical phenomena of magnetic systems is discussed. It consists of systematic series of Landau-like approximations (extended variational method) and the coherent-anomaly method (CAM). As for susceptibility, the present method is equivalent to the power-series CAM theory. On the other hand, the EVM gives a set of new approximants for other physical quantities. Applications to d-dimensional Ising ferromagnets are also described. The critical points and exponents are estimated with high accuracy.
ESSENTIALS OF ANYONS
Authors: STONE MICHAEL
Published: November 2004

These lecture notes are intended to provide an introduction to Chern-Simons theories and “anyons” for readers with interests in condensed matter physics. I discuss applications of anyons in the fractional quantum Hall effect and to superconductivity.
COMPLETE INTEGRABILITY AND THE PAINLEVÉ PROPERTY
Authors: PURI SANJAY
Published: November 2004

We present a systematic review of the connection between the complete integrability of (finite-dimensional and infinite-dimensional) Hamiltonian and non-Hamiltonian dynamical systems and the singularity structure of their equations of motion. We make a special attempt to separate the many conjectures in the field from the few rigorous results. The singularity analysis of ordinary and partial differential equations is illustrated by means of four examples. In the Appendix, we present a brief review of the special properties of soliton equations and the relations between them. We summarize these relations in a tabular form.
TWO-DIMENSIONAL ISING MODEL IN ANNEALED RANDOM FIELDS
Authors: GONÇALVES L.L. , HORIGUCHI T.
Published: November 2004

The critical behaviour of the two-dimensional Ising model in annealed random fields is studied. Two different kinds of random field are considered and exact results obtained for the transition temperature when the field distribution is symmetric. In the first case the random field is unrestricted and the explicit results obtained for discrete and gaussian field distributions show the annealed field favours the ordering of the system. In the second case the random field satisfies a constraint and explicit results are also obtained for discrete and gaussian field distributions. In the discrete distribution the field assumes the values ±h0,0 and it is shown that there is a critical field hc such that for h0>hc the system presents a reentrant phase transition. In this case the ferromagnetic ground state becomes unstable and there is the appearance of a superantiferromagnetic phase. For h0<hc the ferromagnetic state is stable and the transition temperature decreases due to the presence of the random field.
ALGEBRAIC VARIETIES FOR THE CHIRAL POTTS MODEL
Authors: AVAN J. , MAILLARD J-M. , TALON M. , VIALLET C.
Published: November 2004

We describe the symmetries of the chiral checkerboard Potts model (duality, inversion relation, …) and write down the algebraic variety corresponding to the integrable case advocated by Baxter, Perk, Au-Yang. We examine some of its subvarieties, in different limits and for various lattices, with a special emphasis on q=3. This yields for q=3, a new algebraic variety where the standard scalar checkerboard Potts model is solvable. By a comparative analysis of the parametrization of the integrable four-state chiral Potts model and the one of the symmetric Ashkin-Teller model, we bring to light algebraic subvarieties for the q-state chiral Potts model which are invariant under the symmetries of the model. We recover in this manner the Fateev-Zamolodchikov points.
QUASICRYSTALLOGRAPHY ON THE SPIRAL OF ARCHIMEDES
Authors: BURSILL L. A.
Published: November 2004

The concept of a spiral lattice is discussed. Some examples of known mineral structures, namely clino-asbestos, halloysite and cylindrite, are then interpreted in terms of this structural principle. An example of a synthetic sulphide catalyst spiral structure having atomic dimensions is also described. All of these inorganic spiral structures are based on the spiral of Archimedes. The principles for a new type of crystallography, based on the Archimedian spiral, are then presented.
ELEMENT CONCENTRATION CHANGES IN SUPERCONDUCTING MATERIALS FROM THE Bi-Cd-Sr-Ca-Cu OXIDE SYSTEM
Authors: KONSTANTINOV K. , KARBANOV S. , SOULEVA A. , ATANASSOV S.
Published: November 2004

Superconducting materials from the system Bi-Cd-Sr-Ca-Cu-O with critical temperature in the range of 86–96 K have been synthesized. The starting materials as well as the synthesized samples have been analysed by ICP spectrometry. A slight increase in element concentrations of the synthesized superconducting materials has been observed. This fact should be considered when materials with precisely stoichiometry are synthesized.
MORPHOLOGICAL EVOLUTION OF DROPLETS IN OSTWALD RIPENING
Authors: IMAEDA TATSUHIRO , KAWASAKI KYOZI
Published: November 2004

The multipole expansion theory presented recently by the authors for Ostwald ripening in a two-dimensional system is extended to apply to the three-dimensional ripening process. A fairly reasonable computation time is enough to simulate the morphological evolution of many droplets.
A BRIEF REVIEW OF RECENT STUDIES OF C, Si AND Ge METALLIC LIQUIDS
Authors: DHARMA-WARDANA M.W. C. , PERROT FRANÇOIS
Published: November 2004

A brief review of recent studies of C, Si and Ge metallic liquids is presented. We compare results from density functional calculations using (a) a model of diffusively free ions as in a simple metal or plasma (b) Car-Parrinello type MD-simulations which involve many center interactions and (c) Stillinger-Weber type models which start from the Lennard-Jones covalent-bond prototype. The simple metallic model using one-parameter pseudopotentials and pair-potentials lead to structure factors S(k) in good agreement with experiment, with Car-Parrinello MD calculations and those of Stillinger and Weber. The shoulder structure in the S(k) is explained in the metallic model in terms of competing minima in the pair-potential. The metallic model predicts that l-Carbon has a single sp-band, is highly conducting and strongly compressible, with a broad peak in S(k) located near the ‘hump’ in the S(k) of l-Si. The structure factors and pair correlation functions were calculated using the modified hyper-netted chain equation.
MICROSTRUCTURE AND Jc OF YBCO SUPERCONDUCTOR PREPARED BY DIRECTION SOLIDIFICATION PROCESS
Authors: LIU F.S. , MOU H.L. , WANG K.G. , ZHANG T.J. , WU X.Z. , ZHOU L.
Published: November 2004

Polycrystalline YBCO superconductors have been prepared by a directional solidification process (DSP). X-ray diffraction pattern reveals the YBa 2Cu3 O 7−y phase of the samples possessing strong texture which grows out along the length of the tape-shape sample. This dense, regularly aligned, plate-shaped crystal structure is beneficial to transporting superconducting current according to the Jc measurement at 0–1 T and 77 K. Three basic defects and the reason for forming them are discussed. Jc values are measured by the standard four-probe dc resistive method at a criterion of 1 μv/cm. The optimum Jc values of DSP samples are over 12200 A/cm 2 and more than 4200 A/cm 2 at 77 K and 0–1 T respectively.
NON-EQUILIBRIUM TRICRITICAL BEHAVIOR IN LASERS
Authors: MORTAZAVI MANSOUR , SINGH SURENDRA
Published: November 2004

Tricritical behavior in lasers is reviewed briefly. Threshold behavior in the laser with a saturable absorber is interpreted in terms of first- and second-order phase transitions within the framework of Landau theory (mean field). The intersection of the lines of first- and second order phase transitions in this system provides an example of a non-equilibrium tricritical point. By varying the operating parameters of a He:Ne laser with an intracavity Ne absorber it was possible to operate the laser near the tricritical point. Experimental results are compared with the predictions of mean field theory.
EXACTLY SOLUBLE MODEL OF A METAL WITH RANDOM SCATTERING CENTERS
Authors: CHEN HUA , MATTIS DANIEL
Published: November 2004

We describe a “backward scattering” model in which an electron of wavevector k can be scattered only to − k , by means of a random matrix element v(k). Many observables, including density of states and heat capacity, can be calculated exactly in this model for arbitrary probability distribution P(v) of the random potentials. We apply it to superconductivity, where this scattering supplies a “pair breaking” mechanism. There, we calculate the decrease of Tc with the strength of the disorder potential 〈|v(k)|〉, and determine the manner in which Tc→0 with increasing disorder.
WEAK LOCALIZATION AS A PROBE FOR AN INHOMOGENEOUS MAGNETIC FIELD DISTRIBUTION
Authors: BENDING S.J. , VON KLITZING K. , PLOOG K.
Published: November 2004

Type II superconducting films have been prepared on top of the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. In an applied magnetic field the inhomogeneous flux distribution at the superconductor is projected down onto the electron gas. At low applied fields the distribution at the 2DEG takes the form of flux tubes which are much narrower than an electron inelastic scattering length. In this regime we observe a qualitatively new weak localization magnetoconductivity proportional to |B| in contrast to the B2 homogeneous result and in semi-quantitative agreement with the theory of Rammer et al.1 We further demonstrate that the 2DEG can be used as a probe of the spatial distribution of an inhomogeneous magnetic field
SIMULATION OF ENERGETIC CLUSTER IMPACTS ON METALLIC TARGETS
Authors: SHAPIRO M.H. , TOMBRELLO T.A.
Published: November 2004

We review recent progress in the use of molecular dynamics (MD) simulations to study the energetic collisions of cluster ions with metallic surfaces. MD simulations have been used to predict the energy, number-density, and confinement-time properties of the highly nonlinear collision cascades initiated by cluster impacts; as well as to predict the yields, energy-distributions, and angle-distributions of ejected cluster-atoms and target-atoms.
ISOTOPE SHIFT OF THE ENERGY GAP OF DIAMOND
Authors: COLLINS A.T. , LAWSON S.C. , DAVIES G. , KANDA H.
Published: November 2004

Optical absorption and cathodoluminescence measurements show that the indirect energy gap of 13 C diamond is 13.6±0.2 meV larger than for 12 C diamond. Calculations based on the measured shift of the energy gap with temperature, allowing only for changes in electron-phonon coupling, yield a value for the isotope shift of 13.5±2.0 meV , in excellent agreement with experiment.
SQUEEZED EXCITONS IN SEMICONDUCTORS
Authors: BA AN NGUYEN
Published: November 2004

The concept is introduced of squeezed excitons that appear during the process of their interaction with squeezed photons. Situations are considered where the excitons initially are in the Fock or coherent states. For the excitons to become squeezed it is more favourable to prepare them beforehand in a coherent state than in a Fock one. The squeezing degree of excitons depends on that of the initial photons and on detuning.
MECHANISM OF SOLID STATE REACTION FROM 2212 TO 2223 IN BSCCO STUDIED BY HREM
Authors: WEN SHULIN
Published: November 2004

Two mechanisms of solid state reaction from 2212 to 2223 in Bi-Sr-Ca-Cu-O have been investigated and are elucidated in this paper. The first mechanism is related to nucleation of 2223 phase in a liquid matrix with the composition of Bi 2 SrCaCu 2 O +Ca 2 CuO 3+ CuO and subsequent growth. The second mechanism is related to intragrain reaction in which only two layers of atoms (a Ca layer and a CuO layer) are required to move into the 2212 structure forming the 2223 structure. To study the mechanisms of such a solid state reaction may be very important for the preparation of pure 2223 phase in Bi-Sr-Ca-Cu-O .
POINT-CONTACT SPECTRA OF THE NONSUPERCONDUCTING COPPER-OXIDE CERAMICS: OBSERVATION OF MULTIPLE RESISTANCE PEAKS
Authors: SVISTUNOV V.M. , REVENKO YU. F. , GRIGUT O.V. , POPOV O.A. , BELOGOLOVSKII M.A. , KHACHATUROV A.I.
Published: November 2004

Strong differential resistance peaks have been observed in the point-contact characteristics of normal state copper-oxide ceramics. A possible interpretation of the spikes that have been found previously for a variety of high-Tc superconducting polycrystalline samples is discussed.
AN EXACTLY SOLVABLE FERMION MODEL: SPINONS, HOLONS AND A NON-FERMI LIQUID PHASE
Authors: BASKARAN G.
Published: November 2004

An interacting fermion model in d-dimensions is introduced and solved exactly. Low energy excitations have complete spin-charge decoupling. The holon spectrum is gapless and exhibits a pseudo-Fermi surface. Spinons have a gap and, as in the 1-D Hubbard model, the spinons exist only in a limited region of the Brillouin Zone. As a function of electron concentration the system exhibits metal insulator transition.
MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS I—LOW-FIELD MICROWAVE ABSORPTION IN A BiSrCaCuO THIN FILM DEPOSITED BY MOCVD
Authors: SUGAWARA K. , SUGIMOTO T. , YASUIKE K. , BAAR D.J. , SHIOHARA Y. , TANAKA S.
Published: November 2004

Non-resonant microwave absorption as a function of temperature and magnetic field has been studied in a Bi-Sr-Ca-Cu-O film prepared by MOCVD. A maximum in the absorption as a function of temperature was observed at approximately 60 K. An average Josephson loop diameter of about 0.9~1.5 microns was inferred from the experimental results. The absorption was found to depend on the angle of the film plane relative to the applied field.
SINGLE-PARTICLE EXCITATIONS IN SUPERFLUID HELIUM
Authors: YUKALOV V.I.
Published: November 2004

We show theoretically that the collective spectrum of a Bose liquid contains, besides the well-known phonon-roton branch, single-particle excitations existing below the roton-stability boundary k r , but above a threshold kt. The existence of these single-particle excitations is not an experimental artifact as has been supposed earlier. Calculations made for superfluid helium give the threshold momentum k t ≅1 Å−1. This value and the attenuation found of the single-particle excitations are in very good agreement with experimental data.
EFFECT OF DYNAMIC CONFORMATION DISTRIBUTIONS ON MOLECULAR TILT IN CHIRAL SMECTIC LIQUID CRYSTALS
Authors: LEE SIN-DOO , PATEL J. S. , GOODBY J. W.
Published: November 2004

It is shown that for some chiral smectic A materials the field-induced molecular tilt undergoes a peculiar sign inversion with respect to the layer normal as the temperature increases. The induced molecular tilt vanishes at a characteristic temperature in the smectic A state. This anomalous behavior can be described in terms of a dynamically fluctuating mixture of at least two molecular conformers, separated by an energy barrier in their liquid-crystalline states. The energy barrier between these two conformers is found to be comparable to the rotational barrier in normal hydrocarbons.
EXACT MEAN FIELD THEORY FOR CORRELATED LATTICE FERMIONS IN HIGH DIMENSIONS
Authors: VAN DONGEN P. G. J.
Published: November 2004

We review the recently introduced concept of exact mean-field theories for fermionic lattice models. The method is applied to the Extended Simplified Hubbard Model, which is an Extended Hubbard model (including nearest-neighbor interaction) where only the ↓-electrons can hop. The construction of an exact mean-field Hamiltonian is discussed and a summary is given of the results obtained for the critical temperature, the order parameter and the density of states.
PROBING SINGLE CHARGES BY SCANNING FORCE MICROSCOPY
Authors: SCHÖNENBERGER CH. , ALVARADO S. F.
Published: November 2004

The scanning force microscopy is used to charge insulating films locally and to monitor the decay thereafter. On Si 3 N 4 films the charge decay shows up as a discontinuous staircase, demonstrating single charge carrier resolution. The decay is controlled by thermionic emission. The smallest charge amount transferred into a PMMA film was only one or two electrons. The imaged charge area showed no broadening with time, indicating that the excess carriers are immobile.
DONOR LEVEL OF INTERSTITIAL HYDROGEN IN GaAs
Authors: CLERJAUD B. , GENDRON F. , KRAUSE M. , ULRICI W.
Published: November 2004

The carbon-hydrogen complex in GaAs only forms in p-type material. Diffusing hydrogen has to be in a positive charge state for such a complex to be formed. The corresponding hydrogen donor level is shown to be located around 0.5 eV above the top of the valence band.
THE INFLUENCE OF THE ANISOTROPY TO THE FLUX CREEP OF GdBa2Cu3Oy EPITAXIAL FILM
Authors: SHA J. , HE Z. H. , Zhu C. F. , Wang N. L. , Chen X. H. , Chen X. A. , Cao L. Z. , Zhang Q. R. , Yi H. R. , Li H. C.
Published: November 2004

I – V characteristics of epitaxial, c-axis-oriented GdBa 2 Cu 3 O y film was measured between 70 K and 90 K. A magnetic field of 3 T was applied parallel to the basal plane (a – b plane), the angle between the field and one side of the substrate being 0° or 60°. We found that there were differences between the I – V characteristics for the 0° and 60° cases due to the anisotropy of the superconductivity in the a – b plane.
DEFECTS IN AMORPHOUS Si:H — THE REHYBRIDIZED TWO-SITE (RTS) MODEL
Authors: REDFIELD DAVID
Published: November 2004

A comprehensive model for the metastable defects in amorphous Si:H is developed by adapting a recent theory for several kinds of defects in crystalline semiconductors, particularly the DX center in AlGaAs. This new model accounts in a unified way for all of the major observations of defects induced by light, quenching, doping, or compensation; as well as for their anneal. The stretched-exponential time dependence of defect densities with light exposure or annealing, and saturation of the density are also explained. This model is based on foreign atoms rather than on breaking of Si-Si bonds, and in undoped materials it is suggested that unintentional impurities are the source.
PHASE COHERENT BOND STATES
Authors: CHAKRABARTI J. , FAISAL F. H. M.
Published: November 2004

Phase coherent bond wavefunctions are shown to be approximate solutions of the antiferromagnetic Hamiltonian with the hopping term included (the t - J model) for t ≫ J. We determine the number of independent bond modes of this Hamiltonian in two dimensions. A brief discussion of the topological structure of the space of phases of the wavefunctions is given, and the main results of the analysis are briefly summarized at the end.
ELECTROMAGNETIC WAVE PROPAGATION IN PERIODIC DIELECTRIC MEDIA: THE PHOTONIC BAND STRUCTURE
Authors: SATPATHY SASHI , ZHANG ZE
Published: November 2004

The formation of photonic band structure by electromagnetic waves propagating in a periodic dielectric medium is discussed. The existence of a photonic gap at the Brillouin zone boundary is illustrated in the nearly-free-photon approximation. Numerical results obtained by solving the Maxwell's equations with the planewave method are presented for selected cases. For appropriate dielectric structures, a true photonic band-gap extending throughout the Brillouin zone can exist leading to the possibility of novel physical effects.
ON RELATION BETWEEN SYMMETRIC VERTEX MODEL AND ISING MODEL ON THE SQUARE LATTICE
Authors: SAMAJ L. , KOLESÍK M.
Published: November 2004

The symmetric version of the two-state vertex model on the square lattice is studied. It is shown that there exists a manifold in the vertex weights parameter space on which the model can be mapped onto the Ising model in a field. The choices of symmetric vertex weights for which the equivalence holds in the whole temperature range are briefly discussed.
TRANSIENT RESPONSE THEORY OF SEMICONDUCTOR SUPERLATTICES: CONNECTION WITH BLOCH OSCILLATIONS
Authors: IGNATOV ANATOLY A. , DODIN E. P. , SHASHKIN V. I.
Published: November 2004

Results of an analytical calculation of the drift velocity transient response of semiconductor superlattices (SL) based on the moment balance equations method are presented. It is shown that under definite conditions the transient response can exhibit oscillation behaviour at the characteristic "effective Bloch frequency" depending on the momentum and energy relaxation times. The criterion that determines when the negative differential velocity (NDV) effect in superlattices is accompanied by Bloch oscillations (BO) is formulated. The method used permits one to estimate the time of NDV formation in SL solely on the basis of the measured (or simulated) static V – E characteristic.
ANALYZING TRACE ELEMENTS BY RIS-TOF MASS SPECTROMETRY
Authors: MA W. Y. , HUI Q. , ZHAO W. Z. , WEN K. L. , XU X. Y. , CHEN D. Y.
Published: November 2004

A new method of laser resonance ionization spectroscopy combined with time-of-flight mass spectrometry (RIS-TOF) has been investigated to detect trace amounts of elements in a substance. It is based on thermal atomization of a substance in vacuum and detection of the trace atoms by the laser resonant ionization technique. A rather effective way of detecting atoms is by multistep excitation to autoionization states with laser beams. The measurement results of Au and Ru in solution samples and in geological samples are described. The direct detection limit of Au and Ru is 0.1 ppb in a 10 μl solution sample.
DEGRADATION OF Bi2Sr2Ca2Cu3Oy CERAMICS
Authors: GRISHIN A. M. , KORENIVSKI V. N. , UL'YANOV A. N.
Published: November 2004

The decrease of grain superconducting transition temperature of Bi 2 Sr 2 Ca 2 Cu 3 O y ceramics on low-temperature thermocycling has been revealed and studied. Results indicate that the multi-phase samples degrade more quickly and more considerably than the single-phase samples.
ELECTRON-PHONON INTERACTION FOR AN ANALYTIC SOLUTION TO THE BCS EQUATION FOR THE HIGH TEMPERATURE SUPERCONDUCTORS
Authors: GUPTA H. C.
Published: November 2004

An energy dependent electron-phonon interaction has been used in the BCS equation. This provides an exactly solvable analytic solution to the BCS equation for the superconducting transition temperature and the gap parameter at absolute zero. These analytically obtained equations reduce to standard BCS form when temperature is small. These equations are applicable to low as well as high temperature superconductors successfully for their superconducting transition temperature and the energy gap parameter.
ACOUSTIC PROPERTIES OF Nd2CuO4 AT LOW TEMPERATURES
Authors: FIL V. D. , ZVYAGINA G. A. , ZHERLITSYN S. V. , VITEBSKY I. M. , SOBOLEV V. L. , BARILO S. N. , ZHIGUNOV D. I.
Published: November 2004

Acoustic properties anomalies near the points of phase transition in the magnetic subsystem of Nd 2 CuO 4 have been studied. A spontaneous ferroelastic phase transition at T = 5 K and magnetic field induced ferroelastic phase transition (PT) associated with continuous spin reorientations at T < 0.5 K have been found. The exchange nature of magnetoelastic coupling is suggested.
THIN FILM ELECTRON INTERFEROMETRY
Authors: WANG Y. R. , KUBBY J. A. , GREENE W. J.
Published: November 2004

Electron transport through thin overlayers of tin grown on a silicon substrate, and stacking-fault contrast in topographic and conductivity images of Si (111) – 7 × 7 are investigated. Resonances that depend on structural integrity of the overlayer are observed in the conductivity images, and are interpreted as consequences of electron standing-wave formation within the overlayer. The experimental spectra are analyzed using a one-dimensional model which has scattering potentials located at the sample surface and at the overlayer-substrate interface. The agreement between experiment and theory demonstrates that electron-standing wave spectra, in conjunction with bias-dependent topographic and conductivity images, are useful for probing details of buried interfaces formed by surface reconstruction and in heteroepitaxial growth.
THE GLASS TRANSITION ANOMALIES OF MYOGLOBIN IN THE LIGHT OF MODE COUPLING THEORY
Authors: DOSTER W.
Published: November 2004

The physics and some predictions of recent mode coupling theories concerning the liquid to glass instability are reviewed with the scope to explore its potential to explain the dynamics of non-simple liquids. It is proposed that the dynamics scaling behaviour observed in the neutron scattering spectra of myoglobin reveal a critical temperature which is associated with the arrest of density fluctuations.
CHARGE-FLUX DENSITY WAVES: ANYONS IN A PERIODIC POTENTIAL
Authors: Gaitonde D. M. , Rao Sumathi
Published: November 2004

We show that the lattice periodicity which causes a modulation of the charge density by a wave vector q also leads to a modulation of the flux density if the charged particles are anyons. Within mean field theory, we obtain a charge and flux density wave (CFDW) where the degenerate Landau levels of a constant magnetic field split into bands. For a weak periodic flux superimposed on a strong constant flux, anyon superconductivity at integer filling of Landau levels (corresponding to a statistics parameter of θ = π(1 − 1/ν) with ν = n = integer ) is not affected. However, at statistics corresponding to non-integer filling of Landau levels, for certain commensurability conditions between the lattice length (a), the magnetic length (l) and the filling fraction (ν), gaps open up at the Fermi level and convert an anyon metal into an anyon insulator.
SOLITARY WAVES IN A SPIN CHAIN UNDER A SUPER-LONG-WAVE APPROXIMATION
Authors: SHI ZHU-PEI , HUANG GUOXIANG , TAO RUIBAO
Published: November 2004

Solitary waves in a spin chain with biquadratic anisotropic exchange interaction are investigated by means of the Holstein-Primakoff bosonic representation of spin operators. It is argued that the modified terms of the nonlinear Schrödinger equation are restricted strongly by the relative ratio of two small parameters η and ε used in long wave approximation and semiclassical approximation respectively. When assuming that η and ε2 have the same order (η−ε2, the so-called “super-long wave approximation”), after retaining terms of the equivalent order O(ε8), we find that the motion of Bose operator in the anisotropic case satisfies Schrödinger equation with high-order nonlinear term α|α|4. Its solitary wave solution and relevant physical results are discussed.
ON THE RELATION BETWEEN DECAGONAL AND ICOSAHEDRAL QUASICRYSTALS
Authors: KNUPFER A. , KRAMER P.
Published: November 2004

A scheme for the relation between the decagonal and the icosahedral quasiperiodic phases is proposed. It is assumed that these phases share the 6D embedding and a fivefold axis with the primitive i-phase. The decagonal phase is interpreted as a rational approximant of the i-phase with a 6D sublattice. A simple model for the decagonal phase is used to compute kinematic diffraction data which show zone axes with pseudo fivefold and pseudo threefold symmetry.
ELECTRON-PHONON EFFECTS IN THE INFRARED SPECTRA OF HIGH Tc SUPERCONDUCTORS
Authors: TIMUSK T. , TANNER D.B.
Published: November 2004

This brief review discusses the evidence for and implications of strong interactions between certain phonon modes and some of the charge carriers in oxide superconductors. We suggest that the interaction, which involves oxygen vibrations, is sufficiently strong that the interacting carriers are rendered immobile. Other carriers interact only weakly; it is these latter free carriers which dominate the electrical conductivity and which condense to form a superfluid.
LONG RANGE ORDER IN THE BLUME-EMERY-GRIFFITHS MODEL
Authors: CORGINI M.
Published: November 2004

Using the Infrared Bounds method it ws demonstrated that a first order phase transition takes place in the m-dimensional (m≥3) Blume-Emery-Griffiths model.
THE AHARONOV-CASHER AND BERRY’S PHASE EFFECTS IN SOLIDS
Authors: BOGACHEK E.N. , KRIVE I.V. , KULIK I.O. , ROZHAVSKY A.S.
Published: November 2004

We consider the manifestations of charge-induced topological phase shift (Aharonov-Casher effect) in condensed matter physics. There will be an oscillating response to high voltage of the magnetic moment (persistent current) and conductivity, as well as a phase shift of the Aharonov-Bohm oscillation to a smaller voltage, for the normal metal ring threaded by a charged fiber. These oscillations shift in phase if the magnetic field vector rotates along the ring, as a consequence of the geometrical (Berry’s) phase associated with the electron spin.
THEOREMS FOR EXACT LOCAL EXCHANGE POTENTIAL
Authors: OU-YANG HUI , LEVY MEL
Published: November 2004

Theorems for the exact local Kohn-Sham exchange potential in density-functional theory are reviewed. Trial exchange potentials based on these theorems are illustrated.
ANNIHILATION OF MAGNETIC FLUX PAIRS IN A SUPERCONDUCTING TRANSITION
Authors: ENOMOTO YOSHIHISA
Published: November 2004

We study the dynamics of annihilation of magnetic flux pairs in a superconducting transition after a quench from a normal state at zero external magnetic field. Simulating an equation of motion for magnetic flux lines in a three dimensional system, we discuss the time-dependent behavior of the system by changing a quenching temperature. It is shown that the inverse square root of the total length of flux lines exhibits a crossover behavior from t1/2 to ln t as a function of time t, and the crossover time is an increasing function of a quenched temperature. The present results are in agreement with those of Liu, Mondello, and Goldenfeld.
LOW FIELD AC MAGNETIC SUSCEPTIBILITY MEASUREMENTS OF MANGANESE ALUMINOSILICATE GLASSES
Authors: RANA MAZHAR U. , ABBAS TAHIR , CHAUDHRY M. ASHRAF
Published: November 2004

The magnetic susceptibility of MnO.Al2O3.SiO2 spin glasses has been measured over a temperature range of 1.5–150 K using a low-field ac mutual inductance technique. The measuring frequency was 250 Hz with a field of 417 mOe (peak). The Mn concentration varied from 6 to 19 atomic percent (at %). At temperatures above 70 K, the susceptibilities follow a Curie-Wiess behavior with a negative Curie temperature and a Bohr magneton number corresponding nearly to the free ion value of Mn. However, below 70 K all glass samples show strong deviation from the Curie-Wiess behavior (a decrease in 1/χ), culminating in spin glass susceptibility maxima at liquid helium temperature for Mn concentration above 9 at %. These results suggest the formation of antiferromagnetic cluster which grows in size with decreasing temperature and becomes infinitely large as the spin glass freezing temperature is approached.
MADELUNG ENERGY AND STABILITY OF ORDERED LATTICE IN A(B′B″)O3
Authors: WANG QIANG , RUSHAN HAN , GAN Z.Z.
Published: November 2004

The Madelung energies of ionic crystal A(B′B″)O3 has been calculated for various B-site charge distributions, i.e., [Formula: see text], [Formula: see text] and [Formula: see text], and ordered superlattices, i.e., 1/2(111), 1/2(110) and 1/2(001). Calculation results show that the Madelung energy increases for a certain ordered structure as the difference in charge between B-site cations increases and demonstrate the experimental observations. Furthermore, the results point out that for a certain charge distribution the sequence of the structural stability is 1/2(001)<1/2(110)<1/2(111). This is in good agreement with experimental facts.
DIFFUSION TEXTURE GROWTH OF Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORS
Authors: TAN N.X. , BOURDILLON A.J. , TSAI W.H.
Published: November 2004

Typically, Bi-Sr-Ca-Cu-O superconductors have a peculiar crystal platelet morphology caused by preferred orientations during crystal growth. Aligned platelets can be formed by reaction between Pb-Bi-O and a ceramic precursor, such as SrCaCu2O4+y. The alignment is due to gravitational pull on the liquid phase during sintering. The processing, microstructure and superconducting transport properties of these aligned BSCCO materials have been characterized. Scanning electron microscopy shows that thick, fiber-textured, films grow in single domains. Zero resistivity at 100 K was observed in a textured specimen sintered for 100 hours. With differential thermal analysis, the flux action of lead, which accelerates the kinetics of Bi 2 Sr 2 Ca 2 Cu 3 O 10+y formation, is understood.
TEMPORAL FLUCTUATIONS OF AN IDEAL BROWNIAN GAS
Authors: FOGEDBY H.C. , JENSEN M.H. , ZHANG Y.-C. , BOHR T. , JENSEN H.J. , RUGH H.H.
Published: November 2004

An ideal gas of Brownian walkers is studied. We find that the temporal fluctuations of the particle density scale as ∆N(τ)~τ1/4 which implies that the corresponding power spectrum exhibits power law scaling with a universal exponent [Formula: see text], independent of dimension. This result is in agreement with earlier work by Voss and Clarke on the noisy diffusion equation.
STRETCHED EXPONENTIAL STRUCTURAL RELAXATION OF COMPOSITE MATERIALS INDUCED BY IMPURITIES DESORPTION IN VACUUM
Authors: KANIADAKIS G. , MIRALDI E. , FRULLA G.
Published: November 2004

The isothermal desorption of impurities, mainly of water, in epoxy reinforced with carbon fibres, kept in vacuum, induces time dependent dimensional variations that do not follow a simple power law. Assuming that dispersive transfer phenomena support the release of the adsorbed vapour, and consequently a “non-Debye” relaxation process, a new method for analysing the experimental data is presented. High accuracy measurements confirm the stretched exponential time dependence of the shrinkage of the examinated samples.
A NEW SUPERSYMMETRIC MODEL FOR SELF-AVOIDING POLYMERS
Authors: CASSI D. , PESANDO I.
Published: November 2004

A new supersymmetric lattice model is introduced that is directly related to the statistics of self-avoiding polymeric chains on generic graphs.
WAVE FUNCTION REPRESENTATION FOR THE GENERALIZED EIGENSTATES OF SU(1, 1) NONCOMPACT GENERATORS
Authors: PENNA VITTORIO
Published: November 2004

The SU(1, 1) algebra is represented by a two bosonic operator realization. This allows one to obtain a remarkable simplification of the SU(1, 1) noncompact generator eigenvectors by representing the Hilbert space basis in terms of two harmonic oscillator wave functions.
LEARNING RULES FOR ASSOCIATIVE MEMORIES
Authors: VERGINI EDUARDO G. , BLATT MARCELO G.
Published: November 2004

We discuss some of the most popular learning rules that can be used to construct Neural Networks that act as associative memories. The Hebb’s rule, perceptron type algorithms and the projector rule with local versions are included.
SPEED, ACCURACY, AND FLEXIBILITY TRADE-OFFS IN ON-LINE CHARACTER RECOGNITION
Authors: TAPPERT C. C.
Published: November 2004

An on-line character recognizer was improved by making trade-offs on computation speed, recognition accuracy, and flexibility. Firstly, the error rate was halved by increasing computation precision at the expense of speed, achieving a character recognition accuracy of 97.3 percent. Secondly, without loss of accuracy, computation speed was increased by an order of magnitude over the original speed, to 85 characters/second on the IBM System 370/Model 3081. This was done by using a fast linear match to narrow the character choices for a slow but accurate elastic (non-linear) match. Some loss in flexibility resulted, however, because the linear match requires the same number of handwritten strokes for input and prototype characters. Also, the error rate of elastic matching was found to be about half that of linear matching.
RESEARCH ON CHINESE OCR IN TAIWAN
Authors: CHENG FANG-HSUAN , HSU WEN-HSING
Published: November 2004

This paper describes typical research on Chinese optical character recognition in Taiwan. Chinese characters can be represented by a set of basic line segments called strokes. Several approaches to the recognition of handwritten Chinese characters by stroke analysis are described here.

A typical optical character recognition (OCR) system consists of four main parts: image preprocessing, feature extraction, radical extraction and matching. Image preprocessing is used to provide the suitable format for data processing. Feature extraction is used to extract stable features from the Chinese character. Radical extraction is used to decompose the Chinese character into radicals. Finally, matching is used to recognize the Chinese character.

The reasons for using strokes as the features for Chinese character recognition are the following. First, all Chinese characters can be represented by a combination of strokes. Second, the algorithms developed under the concept of strokes do not have to be modified when the number of characters increases. Therefore, the algorithms described in this paper are suitable for recognizing large sets of Chinese characters.
RECOGNIZING HANDWRITTEN CHINESE CHARACTERS BY STROKE-SEGMENT MATCHING USING AN ITERATION SCHEME
Authors: CHOU SHENG-LIN , TSAI WEN-HSIANG
Published: November 2004

The problem of handwritten Chinese character recognition is solved by matching character stroke segments using an iteration scheme. Length and orientation similarity properties, and coordinate overlapping ratios are used to define a measure of similarity between any two stroke segments. The initial measures of similarity between the stroke segments of the input and template characters are used to set up a match network which includes all the match relationships between the input and template stroke segments. Based on the concept of at-most-one to one mapping an iteration scheme is employed to adjust the match relationships, using the contextual information implicitly contained in the match network, so that the match relationships can get into a stable state. From the final match relationships, matched stroke-segment pairs are determined by a mutually-best match strategy and the degree of similarity between the input and each template character is evaluated accordingly. Certain structure information of Chinese characters is also used in the evaluation process. The experimental results show that the proposed approach is effective. For recognition of Chinese characters written by a specific person, the recognition rate is about 96%. If the characters of the first three ranks are checked in counting the recognition rate, the rate rises to 99.6%.
APPLICATIONS OF NEURAL NETWORKS TO CHARACTER RECOGNITION
Authors: GUYON I.
Published: November 2004

Among the many applications that have been proposed for neural networks, character recognition has been one of the most successful. Compared to other methods used in pattern recognition, the advantage of neural networks is that they offer a lot of flexibility to the designer, i.e. expert knowledge can be introduced into the architecture to reduce the number of parameters determined by training by examples.

In this paper, a general introduction to neural network architectures and learning algorithms commonly used for pattern recognition problems is given. The design of a neural network character recognizer for on-line recognition of handwritten characters is then described in detail.
IMAGE MODEL, POISSON DISTRIBUTION AND OBJECT EXTRACTION
Authors: PAL NIKHIL R. , PAL SANKAR K.
Published: November 2004

The theory of formation of an ideal image has been described which shows that the gray level in an image follows the Poisson distribution. Based on this concept, various algorithms for object background classification have been developed. Proposed algorithms involve either the maximum entropy principle or the minimum χ2 statistic. The appropriateness of the Poisson distribution is further strengthened by comparing the results with those of similar algorithms which use conventional normal distribution. A set of images with various types of histograms has been considered here as the test data.
AN ALTERNATIVE APPROACH IN APPROXIMATE REASONING USING FUZZY PRODUCTION RULES IN EXPERT SYSTEMS
Authors: HALIM M. , HO K. M. , LIU A.
Published: November 2004

This paper outlines an alternative approach using fuzzy production rules to handle approximate reasoning in expert systems without using the Generalised Modus Ponens (GMP) model by Zadeh. The proposed approach provides a method whereby a collection of rules is used to specify the properties of the inference as required by the expert. An example on the medical diagnosis of Acute Rheumatic Fever is used for illustration.
OPTIMAL HIDDEN UNITS FOR TWO-LAYER NONLINEAR FEEDFORWARD NEURAL NETWORKS
Authors: SANGER TERENCE D.
Published: November 2004

The output layer of a feedforward neural network approximates nonlinear functions as a linear combination of a fixed set of basis functions, or "features". These features are learned by the hidden-layer units, often by a supervised algorithm such as a back-propagation algorithm. This paper investigates features which are optimal for computing desired output functions from a given distribution of input data, and which must therefore be learned using a mixed supervised and unsupervised algorithm. A definition is proposed for optimal nonlinear features, and a constructive method, which has an iterative implementation, is derived for finding them. The learning algorithm always converges to a global optimum and the resulting network uses two layers to compute the hidden units. The general form of the features is derived for the case of continuous signal input, and this result is related to transmission of information through a bandlimited channel. The results of other algorithms can he compared to the optimal features, which in some cases have easily computed closed-form solutions. The application of this technique to the inverse kinematics problem for a simulated planar two-joint robot arm is demonstrated here.
SEGMENTATION OF ULTRASONIC IMAGES WITH NEURAL NETWORKS
Authors: SILVERMAN RONALD H.
Published: November 2004

Neural networks differ from traditional approaches to image processing in terms of their ability to adapt to regularities in image structure and to self-organize so as to implement directed transformations. Biomedical ultrasonic images are often degraded in quality by noise and other factors, making enhancement techniques particularly important. This paper describes use of back propagation and competitive learning for enhancement and segmentation of ultrasonic images of the eye. Of particular interest is the extension or these technique to segmentation of three-dimensional data sets, where simple thresholding and gradient operations are not entirely successful.