bluuebunny/crossref_metadata_2025 huggingface dataset:
Renormalized Versus Unrenormalized Perturbation-Theoretical Approaches to the Mott Transition
Authors: Lange Ekkehard
Published: October 2003

I employ an exactly soluble toy model to investigate why unrenormalized perturbation theory works better than fully self-consistent approaches in describing the correlation-driven metal–insulator transition.
Multifractality–Monofractality Phase Transition in the Anderson Model
Authors: Bershadskii A.
Published: October 2003

It is shown that statistics of multifractality–monofractality phase transition is described by a generalization of the Bernoulli distribution (multifractal Bernoulli distribution). It is also shown that this distribution is observed in numerical simulations of multifractal wave functions which use the Anderson model, both for short- and long-range disorder. In the last case (corresponding to the dipole interactions) the multifractal specific heat of the most eigenstates — c ≃ d/3, where d is dimension of the space.
The Lifetime Distribution of Tl2+ Defect Configurations in K2SO4 Crystals
Authors: Mamin George V. , Efimov Vladimir N.
Published: October 2003

The coexistenceof EPR lines corresponding to ranges of fast and slow motion of relaxing Tl 2+ defects in K 2 SO 4 crystals was observed. The coexistence was determined to come from the lifetime distribution of Tl 2+ low symmetry defect configurations. The shape of the distribution was fixed.
On the Ehrenberg–Siday–Aharonov–Bohm (ESAB) and Aharonov–Casher (AC) Effects
Authors: Freeman G. R. , Coulson L. D. , March N. H.
Published: October 2003

When an electron beam passes outside a confined magnetic flux, the motional magnetic field of the electrons overlaps the confined flux. The potential energy of the magnetic dipolar interaction of the motional magnetic field with the confined magnetic flux causes the velocity of the electrons to change slightly, which shifts the phase of the electron de Broglie wave. When portions of an electron beam pass on different sides of a confined flux and are then mixed, they produce an interference pattern. There is a similar magnetic dipolar interaction, with resulting velocity and phase changes, when a beam of magnetic particles interacts with the motional magnetic flux produced by their crossing a strong electric field. These are classical electromagnetic dipolar (not Lorentz) interactions that causes changes in Berry's geometrical phase, but are not ESAB or AC effects. Data that were suggested to demonstrate the ESAB and AC effects have been quantitatively interpreted in terms of motional magnetic fields and velocity changes.
Pattern Formation and Competition in the Regime of the Conserved Cubic-Quintic Nonlinear Schrödinger Equation
Authors: Long Tao , He X. T.
Published: October 2003

In this letter, the pattern formation, pattern competition and spatiotemporal chaos are first investigated in the regime of cubic-quintic nonlinear Schrödinger equation in a near-integrable Hamiltonian continuum system using a few important representative manifolds in phase space. We find that the regular pattern competition can exist in some regions of the controlled parameters, and the spatiotemporal chaos may result from stochastic competition of the patterns. This conclusion may be generalized to the systems which have the saddle structure.
Inhomogeneous Magnetic Response in Anyon Fluid at High Temperature
Authors: Ferrer E. J. , de La Incera V.
Published: October 2003

The charged anyon fluid in the presence of an externally applied constant and homogeneous magnetic field is investigated at temperatures larger than the energy gap (T ≫ ω c ). It is shown that the applied magnetic field inhomogeneously penetrates the sample with a spatial periodicity depending on a wavelength that decreases with temperature. The distribution of charges in the (T ≫ ω c )-phase acquires a periodic spatial arrangement.
The Study of Wave Function and the Berry Phase of the Particles in Hall Fluid
Authors: Banerjee Dipti , Basu Banasri
Published: October 2003

We have calculated the Berry phase of Hall particles which are found to remain constant over the filling factor ν in a special arrangement. It has been found that the probability of getting this phase vanishes at ν > 1/5. This is the implication of the crystallization in the Hall fluid after the filling factor ν = 1/6.
On the Viscuous Damping Mechanisms for Vortices in Superconductors
Authors: Kteyan A. A. , Vardanian R. A.
Published: October 2003

Vortex drag mechanisms suggested by Tinkham and by Bardeen and Stephen are considered phenomenologically and shown to be identical.
Melting of a Star-Shaped Vortex in a Type-II Superconductor
Authors: Aruna A. , Shrivastava Keshav N.
Published: October 2003

Since the area of a star-shaped vortex is equal to that of a triangular vortex due to the flux quantization, the size of the star-shaped vortex is derivable from that of the triangular vortex. The fluctuation in the distance between vortices is used to find the flux-lattice melting temperature. It is found that the flux-lattice melting temperature of a star-shaped vortex is about one fourth that of a triangular vortex but at zero temperature, the melting field of a star-shaped vortex is about equal to that of the triangular vortex.
Current-in-Plane Magnetoresistance in a Magnetic Sandwich Structure with the Interface Inter-Diffusional Roughness
Authors: Xu Hui-Ying , Mai Zhen-Hong
Published: October 2003

By introducing a thin transition sublayer to describe the interface structure with large inter-diffusion, the impurities and other defects at it, current-in-plane (CIP) giant magnetoresistance (GMR) is calculated based on the Kubo formalism in real spaces. The oscillations of CIP GMR versus the thicknesses of various layers are predicted due to the quantum size effect. The contribution of the interface inter-diffusional roughness on the GMR effect is discussed with the variations of the thicknesses of ferromagnetic and nonmagnetic layers.
Synthesis and Characterization of La2Ca2Cu2O7 Compound
Authors: Kaliyaperumal L. K. , Srinivas J. , Jeyabalan K.
Published: October 2003

Synthesis and characterization of La 2 Ca 2 Cu 2 O 7 compound at ambient pressure is reported here. The powder X-ray diffraction analysis shows that the compound crystallizes in an orthorhombic crystal system with lattice parameters a = 5.770(4) Å, b = 5.887(7) Å and c = 27.37(2) Å.
Ionic Clusters in Aluminium–Sodium Fluoride Melts
Authors: Akdeniz Z. , Çiçek Z. , Pastore G. , Tosi M. P.
Published: October 2003

From Raman scattering experiments three types of charged AlF n cluster (with n = 4, 5 and 6) have been proposed to coexist in liquid alkali fluoroaluminates such as cryolite ( Na 3 AlF 6). We characterize these isolated clusters by a phenomenological ionic model and employ it to examine how local screening of the excess charge on a cluster may be effected by sodium ions at various compositions in the liquid. We provide the first theoretical explanation for the stability of the AlF 5 cluster at the compositions Na 3 AlF 6 and Na 2 AlF 5.
Polaron Crystallization and Melting: Effects of the Long-Range Coulomb Forces
Authors: Fratini S. , Quémerais P.
Published: October 2003

On examining the stability of a Wigner crystal in an ionic dielectric, two competitive effects due to the polaron formation are found to be important: (i) the screening of the Coulomb force 1/εsr, which destabilizes the crystal, compensated by (ii) the increase of the carrier mass (polaron mass). The competition between the two effects is carefully studied, and the quantum melting of the polaronic Wigner crystal is examined by varying the density at zero temperature. By calculating the quantum fluctuations of both the electron and the polarization, we show that there is a competition between the dissociation of the polarons at the insulator-to-metal transition (IMT), and a melting towards a polaron liquid. We find that at strong coupling, a liquid state of dielectric polarons cannot exist, and the IMT is driven by the polaron dissociation. Next, taking into account the dipolar interactions between localized carriers, we show that these are responsible for an instability of the transverse vibrational modes of the polaronic Wigner crystal as the density increases. This provides a new mechanism for the IMT in doped dielectrics, which yields interesting dielectric properties below and beyond the transition. An optical signature of such a mechanism for the IMT is provided.
Tunneling Spectra of NbSe3 in Magnetic Fields
Authors: Haifeng He , Yunping Wang , Shanlin Li , Xiunian Jing , Guohong Li , Li Lu , Dianlin Zhang
Published: October 2003

The charge density wave gaps of NbSe 3 have been carefully determinated by tunneling spectroscopy. In contrast to earlier work, the gap parameter associated with the 59 K transition obtained in the present measurements is very close to the mean field value. The gap structures for both the 145 K and 59 K transitions are found to be essentially independent of the applied magnetic field H. The present findings strongly suggest that the anomalous magnetotransport properties of the material originate from some other mechanism than a H-induced improvement of Fermi surface nesting.
Correlation Energy of Double-Electron System Obtained by Using B-Spline Basic Sets
Authors: Liu Lianjun , Li Long , Wu Liangkai , Zhang Zhehua , Xu Jingwen , Qiao Haoxue , Li Baiwen
Published: October 2003

We adopt B-spline finite basic sets to calculate correlation energy of the ground states for five kinds double-electron atoms or ions, which is above 1st order of magnitude better than the standard configuration-interaction (CI) method and modified configuration-interaction (MCI) method. These results show its superiority when we use it to deal with the problems of atom structure.
Ultrasonic Velocity Studies on Tl2Ba2Ca2Cu3O10 Superconductor
Authors: Yahya A. K. , Abd-Shukor R.
Published: October 2003

Ultrasonic longitudinal and shear velocities propagated at 7–10 MHz in bulk Tl 2 Ba 2 Ca 2 Cu 3 O 10 have been measured between 80 K and 300 K. Shear velocity measurements revealed a pronounced slope discontinuity of 421 ppm/K at around 160 K. A similar slope change was not observed in the longitudinal mode. The slope change around 160 K for the shear mode is suggested to be attributed to some form of correlated Tl and O(4) orderings in the material.
TDPAC and Positron Lifetime Studies in Cold-Worked TiHf
Authors: Govindaraj R. , Rajaraman R.
Published: October 2003

Well annealed reference TiHf hcp samples are characterized by Time differential perturbed angular correlation (TDPAC) of 133–482 keV γ–γ cascade of 181 Ta and positron lifetime measurements to be free from lattice defects of detectable concentrations. TDPAC measurement on the 50% cold-worked sample shows that a fraction 0.16 of probe nuclei is associated with a cold-working induced defect which is interpreted to be faulted dislocation loop. The complete dissociation of these defects from Hf atoms is observed following the annealing treatment of the sample at 723 K. Predominant annihilation of positrons at dislocation kind of defects is observed by positron lifetime measurements in the cold-worked sample. Complete defect recovery of the sample is seen following the annealing step at 873 K, by positron lifetime measurements. XRD measurement of the cold-worked sample shows the predominant orientation of microcrystallites along [Formula: see text] direction.
An Effective Low-Energy Quasiparticle Model with Attractive Interaction
Authors: Ferraz A. , Ohmura Y.
Published: October 2003

We consider the "high-energy" single-particle states of a strongly interacting electron liquid. These states should be taken into account whenever there are strong incoherent effects produced by interactions. Considering the presence of these particles which are confined in a thin shell in momentum space around [Formula: see text] as well as "low-energy" quasiparticles we derive an effective model by integrating out the "high-energy" fields. The resulting theory produces an effective interaction for the quasiparticles which may be large and negative. This produces an instability which drives the electron liquid towards superconductivity or another non-perturbative regime.
Formation of d-Wave Pairons in Cuprates via Longitudinal-Optical-Phonon Exchange
Authors: Fujita Shigeji , Morabito David L.
Published: October 2003

The d-wave Cooper pairs (pairons) in cuprates with a strong binding along the a- and b-axes are shown to arise from the optical-phonon-exchange attraction.
Creating Coherent States in a Mesoscopic Josephson Junction
Authors: Bin Shao , Zou Jian , Li Qianshu
Published: October 2003

We examine a system of mesoscopic Josephson junction driven by classical field and solve the time-dependent Schrödinger equation of the system with the help of the time-dependent invariant of the Hamiltonian operator. We show that the state of the system can evolve a pure coherent state when the junction is prepared initially in its ground state.
Chaotic Behavior in a Dynamic System Related to the Stationary Path of the Path-Integral for a Brownian Particle in a Double-Well Potential
Authors: Chen L. Y.
Published: October 2003

Considering the path-integral approach to the Brownian motion of a particle in a double-well potential, the joint probability for a possible trajectory (path) is a positive definite functional of the path. In the practically important low temperature or low friction regime, the probability functional is found to comprise dominant contributions from the stationary paths. The corresponding dynamics behaves chaotically, exhibiting intermittency as well as sensitivity to the initial conditions. The first Lyapunov exponent is found to be positive and the attractor in the phase space to be of fractal structure.
Transport Phenomena in the Mixed and Normal State of (Bi1.6Pb0.4)Sr2Ca2(Cu1-xFex)3Oy Epitaxial Thin Films
Authors: Ilonca G. , Pop A. V. , Benea D. , Lung C. , Lachescu M. , Deltour R.
Published: October 2003

We had performed a study on magnetoresistivity, Seebeck, Nernst and Hall effects in the mixed and normal state for Bi2223 thin films in magnetic fields between 0 and 5 T and in the temperature range 5–300 K. The critical temperatures, the Hall concentration, the Nernst and Seebeck coefficients depend strongly on the iron content in the samples. From our experimental data in the mixed state and fluctuation regime, the upper critical field slope (dBc2/dT )=-2:55 T/K was obtained, corresponding to ab-plane coherence length ξab=14 Å. The experimental data are in agreement with the predictions of the time-dependent Ginsburg–Landau theory.
Calculation of the Specific Heat for the First Order Phase Transition in NH4Br
Authors: Yurtseven H. , Yanik A. , Sherman W. F.
Published: October 2003

We calculate in this work the specific heat CVI using the predictions of an Ising model for the NH 4 Br crystal (T C =234 K, P=0). Our calculated CVI values are in good agreement with the experimentally observed CP data from the literature. This shows that the observed behavior of NH 4 Br can be described adequately in the lattice region under an Ising model studied here.
Influence of Thermal Neutrons on Fatty Acids with a Mesomorphic Behavior
Authors: Honciuc M. , Slavnicu E.
Published: October 2003

The paper describes the influence of thermal neutron irradiation on the smectic liquid crystal (SLC) properties of fatty acids: lauric, archydic, elaidic and arachidonic. These fatty acids are precursors or constituents of biological membranes. Microstructural aspects and electric measurements of the dependence of current intensity through the sample on the applied external voltage I=I(U) are presented. An outline of a thermodynamic model in good agreement with the experiments is also given.
Fermionic Coherent State Representation for Generalized Fermionic Bogolyubov Transformation
Authors: Fan Hong-Yi , Fan Yue , Chan F. T.
Published: October 2003

We show that the generalized fermionic Bogolyubov transformation generator [Formula: see text], where Λ is an even n×n matrix, has the manifest fermionic coherent state representation [Formula: see text] The normally ordered form of V(Λ) can be obtained through the technique of integration within an ordered product of fermionic operators. This work is a supersymmetric partner of Ref. 1.
The Fe Influence on the Vortex Response to the AC Field in Bulk (Bi, Pb):2223 Superconductor
Authors: Pop A. V.
Published: October 2003

The effect of Fe 3+ ions on the inter- and intragranular Tp and Tg temperatures of the imaginary peaks of the AC susceptibility has been studied for a (Bi, Pb):2223 superconductor. The linear dependencies of Tp and Tg as a function of AC field amplitude agree with Muller critical state model. The Fe 3+ ions induced a fast decrease of inter and intragranular pinning force densities. The intergrain critical current density J cj calculated from χ″(T) curve is lower in x=0.02 Fe doped sample than in x=0.00 sample. J cj (T) dependence near Tc agrees with the assumption of SNS intergrain junctions.
Stability and Spin Density in Doped Quasi-One-Dimensional Non-Conjugated Organic Ferromagnets
Authors: Yao K. L. , Zhao M. , Liu Z. L.
Published: October 2003

The effects of polarons on the stability of ferromagnetic state in doped quasi-one-dimensional non-conjugated organic ferromagnets are investigated. It is shown that spin density wave of doped main chain near the polaron appears amplitude distortion which changes the stability of the ferromagnetic state. If the spins of polarons along the main chain are contrary to those of side radicals' electrons, the stability of the ferromagnetic state will be strengthened. Under the opposite condition, the stability will be weakened.
XANES Study of Superconducting Lu0.7Ca0.3Ba2Cu3O7-δ Annealed in Argon, Air and Oxygen
Authors: Padalia B. D. , Gupta Sanjay , Prakash Om , Gnanasekar K. I. , Keer H. V. , Selvam P. , Sathe V. G. , Pimpale A. V.
Published: October 2003

Cu K-XANES mesurements have been made on argon, air and oxygen annealed superconducting Lu 0.7 Ca 0.3 Ba 2 Cu 3 O 7-δ compounds. The Cu 1+ peak which is absent for the oxygen annealed sample, appears on air annealing and becomes prominent on argon annealing. For the argon annealed sample, the white line, assigned to Cu 2+, shifts towards the lower energy side and its width increases compared to that of the oxygen and the air annealed samples. From the ratio of areas of Cu 1+ and Cu 2+ deconvoluted peaks and the oxygen content ( O 7-δ), it has been possible to estimate the effective charges (n) on Cu ions separately for the Cu(1) chain and the Cu(2) plane sites. The value of n>2 on Cu of the Cu(2) sheets is found essential for superconductivity. In the light of the observed Tc values, the results are interpreted in terms of under-, near optimum- and over-doping of holes in the CuO 2 planes respectively for the argon, air and oxygen annealing conditions. The analysis of the results provides convincing evidence for hole doping of the CuO 2 planes directly by the divalent Ca in LuBa 2 Cu 3 O 7-δ.
Dynamical and Thermal Properties of Biological Membranes
Authors: Zhang Ling-Yun , Sun Hong
Published: October 2003

The dynamical and thermal properties of biological membrane is theoretically discussed. A nonlinear excitation of biological membrane can be obtained in the presence of an electric field across the biological membrane. The solitary wave can provide an efficient mechanism for the open and closed mechanism of ion channel in the biological membrane. On the other hand, the lipid ordering within the layers is strongly influenced by temperature. By using soliton statistics, the thermal fluctuation of the splay wave and the specific heat of the biomembrane has also been investigated.
Temperature Dependence of Electron Mobility in Doped n-Ge
Authors: Jakeli I. , Kekelidze N. , Ambokadze I. , Shamugia N. , Baskoutas S. , Kapaklis V.
Published: October 2003

In this work we point out experimentally the anomalous behavior of the total mobility as a function of temperature for a specified doped n-Ge sample. Three perfect Ge crystals were grown, with As and Ga as donor and acceptor impurities, with suitable concentrations in one of the crystals, in order to satisfy the condition which is imposed by a theoretical model e.g. 5×10-2<NA/ND<0:33 and ND+NA>8×1013 cm-3. Therefore for this specified crystal the mobility reaches at T=9 K a maximum, at T=23 K it reaches a minimum, at T 25 K it increases according to T-3/2 law, and then decreases monotonously according to T-3/2 law due to the phonon scattering. In contrast in the other two samples, the mobilities rst increase monotonously and then at 18 K and at 26 K decrease monotonously due to the T-3/2 law.
A Simple Path Integral Argument of the One-Dimensional Quantum Electron Localization and the 3D Bell Path Integral Representation
Authors: Botelho Luiz C. L.
Published: October 2003

We give a simple path integral argument of the electron localization phenomena in the one-dimensional Schrödinger equation at a WKB limit of large electron mass. Additionally, we present a many body. Bell path integral representation for the three-dimensional case.
Localization in the Hopping Disordered Bose Hubbard Model
Authors: Sheshadri K.
Published: October 2003

The zero-temperature superfluid (SF)–Bose glass (BG) transition in the strongly correlated (U=∞) Bose Hubbard model in d dimensions driven by disorder in hopping is studied using a simple analytic technique. The transition is identified as the point at which the density of states for local rotations of phase of the superfluid order parameter is enhanced at the lowest energies. This identification leads to the values ν=2/d and z=d/2 for the correlation length and dynamical exponents, respectively, by an approximation calculation of the low-energy density of states for large d. At the transition, the singular part of the compressibility κ vanishes, so κ is finite.
Interchain Alignments and Ground State in Organic Ferromagnets
Authors: Wang W. Z. , Yao K. L. , Lin H. Q.
Published: October 2003

Two kinds of alignments of two neighboring π-conjugated organic ferromagnetic chains are studied by considering the itinerary of electrons, electron–phonon coupling, the Hubbard repulsion and the interchain coupling. It is shown that the out-of-phase alignment is a more stable ferromagnetic structure than in-phase alignment. For out-of-phase alignment, there is a structure transition at a critical interchain coupling, at which the dimerizations of two chains have the same size and reverse sign. Interchain coupling results in transfer of spin density between each main chain and the side radicals.
Superconductivity and Normal-State Properties of (Y1-x-yZrxCay)Ba2Cu3O7-δ Compounds
Authors: Deac I. Gr. , Pop A. V. , Pop V. , Tetean R. , Kovacs D. , Borodi G.
Published: October 2003

The electrical and magnetic properties of ( Y 1-x-y Zr x Ca y) Ba 2 Cu 3 O 7-δ ceramics are investigated by using resistivity, ac and dc susceptibility measurements. X-ray powder diffraction has been used to find the lattice parameters of the samples. The samples are orthorhombic, except the sample with x=0.15 and y=0.2 which is tetragonal. All the samples are superconducting. There is no significant change in Tc for the Zr-doped ( Y 1-x Zr x) Ba 2 Cu 3 O 7-δ samples, while for the ( Y 0.85-y Zr 0.15 Ca y) Ba 2 Cu 3 O 7-δ compounds the Tc decrease with the dopant content and they show temperature dependent dc magnetic susceptibility, in the normal state.
Silicon and Zinc Co-Doped InGaN Films with High Luminuous Efficiency Grown by LP-MOVCD at High Growth Temperature
Authors: Tong Y. Z. , Li F. , Zhang G. Y. , Yang Z. J. , Jin S. X. , Ding X. M. , Gan Z. Z.
Published: October 2003

Silicon and zinc co-doped InGaN films were grown by low pressure MOCVD at growth temperature from 820°C to 1060°C. The 455 nm blue light emitting peak was obtained by Si and Zn co-doping. It was found that the photoluminescence intensity of the 455 nm wavelength peak dramatically increases with increasing of growth temperature. The luminous efficiency nearly increases 100 times from 820°C to 1060°C. It was demonstrated that the characteristics mainly come from improvement of crystalline quality instead of the change of Zn or Si doping density in the InGaN films.
Quantum Geometry for the Brownian Particle
Authors: Botelho Luiz C. , da Silva Edson P.
Published: October 2003

We quantize a classical dissipative system defined by a Brownian particle by means of a Feynman path integral (quantum geometry for the Brownian particle).
Stochastic Resonance in Bistable Systems: The Effect of Simultaneous Additive and Multiplicative Correlated Noises
Authors: Tessone Claudio J. , Wio Horacio S.
Published: October 2003

We analyze the effect of the simultaneous presence of correlated additive and multiplicative noises on the stochastic resonance response of a modulated bistable system. We find that when the correlation parameter is also modulated, the system's response, measured through the output signal-to-noise ratio, becomes largely independent of the additive noise intensity.
Exact Analytic Results for Composite Fermions in a Rajaraman–Sondhi Like Formulation
Authors: Rao Sumathi
Published: October 2003

We obtain the exact spectrum and the unique ground state of two composite fermions (in a Rajaraman–Sondhi like formulation) in an external magnetic field B. We show that the energy eigenvalues decrease with increasing angular momentum, thus making it energetically favourable for composite fermions to stay apart. Generalizing this result to a gas of composite fermions, we provide an energetic justification of the Laughlin and Jain wave-functions.
Teleporting the Schrödinger Cat State
Authors: Moussa M. H. Y. , Baseia B.
Published: October 2003

We present a scheme for the teleportation of a coherent state or a mesoscopic superposition of coherent states — the Schrödinger-cat state. The proposal involves a mesoscopic-correlated state as the quantum channel which is generated through an adaptation of a quantum switch scheme. The required joint measurement performed in a mesoscopic Bell basis is accomplished through a technique for detection of a Schrödinger-cat state "trapped" in a cavity.
Soliton Creation and Annihilation in Josephson Junction in the Presence of Periodic Perturbation
Authors: Shaju P. D. , Kuriakose V. C.
Published: October 2003

The soliton creation and annihilation processes are demonstrated numerically, in the long overlap Josephson junction in the first, second and third Zero-Field Step (ZFS) cases, using the perturbed sine-Gordon (sG) equation in the presence of periodic point-like weak inhomogeneities. In all the ZFS cases, the created soliton is found to be in a bunched (congealed) mode with the other solitons. The I–V characteristics, corresponding to the kink dynamics under a dc bias, at which the creation and annihilation phenomena demonstrated is compared with that of an anti-kink dynamics under the same bias condition.
Equivalence in Mapping of Conductivity, Elasticity and Diffusion Equations Appears or Disappears
Authors: Skal Asya S.
Published: October 2003

Equivalence in mapping of diffusion and conductivity equations appears when diffusion and conductivity belong to the same universality class and disappears in the opposite case. For asymptotic long-time behavior one exponent of regular diffusion coefficient above the threshold [Formula: see text] and two below the threshold [Formula: see text] and [Formula: see text] are introduced, using the conductivity critical exponent (μ and s) and the Hall coeffcient critical exponent Re(p-pc)-g if R2/R1→1 and Re(p-pc)2s if R2/R1→1 and p<pc. In the first two cases equivalence between the diffusion and conductivity problems are disappear. A problem with this analogy lies in an intrinsic property that for percolation lattice the diffusion coeffcient is not a self-averaging quantity unlike the conductivity.

Analogy between conductivity and elasticity appears for scalar forces and disappears for vector forces. The latter leads to new equivalence between elasticity and conductivity in a magnetic field.

The new formulae for a real part of dielectric constant in the static limit for p>pc and the low-frequency ac conductivity are determined due to the new critical exponent for regular diffusion.
Dynamic Monte Carlo Study of the Two-Dimensional Quantum XY Model
Authors: Ying H. P. , Luo H. J. , Schülke L. , Zheng B.
Published: October 2003

We present a dynamic Monte Carlo study of the spin-1/2 quantum XY model in two-dimensions at the Kosterlitz–Thouless phase transition temperature. The short-time dynamic scaling behaviour is found and the dynamical exponents θ, z and the static exponent η are determined.
Temperature Chaos and the Lattice Character of the Hooge Parameter in Semiconductors
Authors: Melkonyan S. V. , Gasparyan F. V. , Aroutiouyan V. M. , Asriyan H. V.
Published: October 2003

The influence of the electron–phonon interaction on formation of the low-frequency noise in semiconductors is theoretically considered. The determining role of scattering mechanisms in formation of the 1/f low frequency noise is shown. The temperature dependence of the Hooge parameter αH is revealed and explained. The lattice character of αH is proven.
Enhancing Retrieval in Neural Networks
Authors: Andrecut M.
Published: October 2003

A simple method for retrieving information in Hopfield neural network is discussed. Numerical simulations for different network sizes were performed in order to test the ability of the model in retrieving patterns. It is shown that an imposed external field (stimulus) enhances the retrieval results of the neural network. For random and unbiased patterns the critical saturation parameter is enhanced from α=0.14 up to α=0.5. Also, important enhancements of the critical saturation parameter are obtained low-activity patterns.
Bayesian Paradigms in Image Processing
Authors: Liu Zhi-Qiang
Published: October 2003

A large number of image and spatial information processing problems involves the estimation of the intrinsic image information from observed images, for instance, image restoration, image registration, image partition, depth estimation, shape reconstruction and motion estimation. These are inverse problems and generally ill-posed. Such estimation problems can be readily formulated by Bayesian models which infer the desired image information from the measured data. Bayesian paradigms have played a very important role in spatial data analysis for over three decades and have found many successful applications. In this paper, we discuss several aspects of Bayesian paradigms: uncertainty present in the observed image, prior distribution modeling, Bayesian-based estimation techniques in image processing, particularly, the maximum a posteriori estimator and the Kalman filtering theory, robustness, and Markov random fields and applications.
Robot Navigation by Visual Dead-Reckoning: Inspiration from Insects
Authors: Srinivasan M. V. , Chahl J. S. , Zhang S. W.
Published: October 2003

Insects such as ants and bees are capable of surprisingly good navigation, despite the small size and relative simplicity of their brains. Recent experimental research in our laboratory, summarized in this chapter, indicates that honeybees estimate the distance travelled to a food site in terms of the image motion that they experience en route. This finding has inspired us to design and build a robot that navigates using a visually-driven odometer.
Assessing Feature Importance in the Context of Object Recognition
Authors: West Geoff A. W.
Published: October 2003

A popular paradigm in computer vision is based on dividing the vision problem into three stages namely segmentation, feature extraction and recognition. For example edge detection followed by line detection followed by planar object recognition. It can be argued that each of these stages needs to be thoroughly described to enable vision systems to be configured with predictable performance. However an alternative view is that the performance of each stage is not in itself important as long as the overall performance is acceptable.

This paper discusses feature performance concentrating on the assessmentof edge-based feature detection and object recognition. Evaluation techniques are discussed for assessing arc and line detection algorithmsand for features in the context of verification and pose refinement strategies. These techniques can then be used for the design and integration of indexing and verification stages of object recognition. A theme of the paper is the need to assess feature extraction in the context of the chosen task.
Geometric Variations: Analysis, Optimization and Control
Authors: Daniel Brett T. , West Geoff A. W. , Cardew-Hall Michael
Published: October 2003

This paper is concerned with the design and manufacturing of 2D and 3D components in the context of process modeling and inspection. A methodology is proposed that models manufacturing processes and learns shape deformations that are the result of out-of-tolerance components. Then during inspection, a deformed shape is analyzed and the process parameter values determined. The key aspect of this approach is that the mapping between process parameters and shape is determined which is not possible using standard process modeling approaches such as finite element analysis. This is different to the traditional approach to tolerancing which is very much as additional procedure to design and doesn't consider process parameter variation, just shape variation. A review of tolerancing is presented as well as a description of techniques for process modeling.
Using Aspect Graphs to Control the Recovery and Tracking of Deformable Models
Authors: Dickinson Sven J. , Metaxas Dimitri
Published: October 2003

Active or deformable models have emerged as a popular modeling paradigm in computer vision. These models have the flexibility to adapt themselves to the image data, offering the potential for both generic object recognition and non-rigid object tracking. Because these active models are underconstrained, however, deformable shape recovery often requires manual segmentation or good model initialization, while active contour trackers have been able to track only an object's translation in the image. In this paper, we report our current progress in using a part-based aspect graph representation of an object14 to provide the missing constraints on data-driven deformable model recovery and tracking processes.
The Role of Machine Learning in Building Image Interpretation Systems
Authors: Caelli Terry , Bischof Walter F.
Published: October 2003

Machine learning has been applied to many problems related to scene interpretation. It has become clear from these studies that it is important to develop or choose learning procedures appropriate for the types of data models involved in a given problem formulation. In this paper, we focus on this issue of learning with respect to different data structures and consider, in particular, problems related to the learning of relational structures in visual data. Finally, we discuss problems related to rule evaluation in multi-object complex scenes and introduce some new techniques to solve them.
Recent Advances in Graph Matching
Authors: Bunke H. , Messmer B. T.
Published: October 2003

A powerful and universal data structure with applications invarious subfields of science and engineering is graphs. In computer vision and image analysis, graphs are often used for the representation of structured objects. For example, if the problem is to recognize instances of known objects in an image, then often models, or prototypes, of the known objects are represented by means of graphs and stored in a database. The unknown objects in the input image are extracted by means of suitable preprocessing and segmentation algorithms, and represented by graphs that are analogous to the model graphs. Thus, the problem of object recognition is transformed into a graph matching problem.

In this paper, it is assumed that there is an input graph that is given on-line, and a number of model, or prototype, graphs that are known a priori. We present a new approach to subgraph isomorphism detection which is based on a compact representation of the model graphs that is computed off-line. Subgraphs that appear multiple times within the same or within different model graphs are represented only once, thus reducing the computational effort to detect them in an input graph. In the extreme case where all model graphs are highly similar, the run time of the new algorithm becomes independent of the number of model graphs. We also describe an extension of this method to error-correcting graph matching. Furthermore, an approach to subgraph isomorphism detection based on decision trees is proposed. A decision tree is generated from the models in an off-line phase. This decision tree can be used for subgraph isomorphism detection. The time needed for decision tree traversal is only polynomial in terms of the number of nodes of the input graph. Moreover, the time complexity of the decision tree traversal is completely independent on the number of model graphs, regardless of their similarity. However, the size of the decision tree is exponential in the number of nodes of the models. To cut down the space complexity of the decision tree, some pruning strategies are discussed.
Cooperative Spatial Reasoning for Image Understanding
Authors: Matsuyama Takashi , Wada Toshikazu
Published: October 2003

Spatial Reasoning, reasoning about spatial information (i.e. shape and spatial relations), is a crucial function of image understanding and computer vision systems. This paper proposes a novel spatial reasoning scheme for image understanding and demonstrates its utility and effectiveness in two different systems: region segmentation and aerial image understanding systems. The scheme is designed based on a so-called Multi-Agent/Cooperative Distributed Problem Solving Paradigm, where a group of intelligent agents cooperate with each other to fulfill a complicated task. The first part of the paper describes a cooperative distributed region segmentation system, where each region in an image is regarded as an agent. Starting from seed regions given at the initial stage, region agents deform their shapes dynamically so that the image is partitioned into mutually disjoint regions. The deformation of each individual region agent is realized by the snake algorithm14 and neighboring region agents cooperate with each other to find common region boundaries between them. In the latter part of the paper, we first give a brief description of the cooperative spatial reasoning method used in our aerial image understanding system SIGMA. In SIGMA, each recognized object such as a house and a road is regarded as an agent. Each agent generates hypotheses about its neighboring objects to establish spatial relations and to detect missing objects. Then, we compare its reasoning method with that used in the region segmentation system. We conclude the paper by showing further utilities of the Multi-gent/Cooperative Distributed Problem Solving Paradigm for image understanding.
Human Understanding Limits in Visualization
Authors: Maeder Anthony J.
Published: October 2003

Many different techniques for visualizing data exist, and often users must experiment with several before selecting the most effective one for their problem. Knowledge of the characteristics of the human visual system can assist in our choice of visualization techniques. Limits imposed by our visual "cognitive bandwidth" mean that only detail up to these limits needs to be generated in a visualization scene. Some aspects of our visual process will be discussed and an approach will be described for modeling scene detail, which takes visual limits of such aspects into account.
A Strategy and Architecture for the Visualization of Complex Geographical Datasets
Authors: Gahegan Mark , O'Brien David
Published: October 2003

The use of computer visualization as a means to analyze complex geographic datasets is discussed. Visualization is a valuable tool for conducting exploratory data analysis on geographical data; making good use of the human eye's unparalleled ability to recognize structure and relationships that may be inherent within the data. Traditional GIS are extremely poor at visualization, being limited to a very restricted set of visual attributes with which to convey information (position, size, color). The use of a more sophisticated approach is discussed in detail. Specifically, a system to visualise complex environmental datasets is described, which makes use of knowledge concerning the problem domain as well as knowledge concerning human cognition.

In the realizations produced, the most salient attributes in the data, for a particular task, are assigned to the most striking visual attributes. Assignments are controlled by heuristics that may be changed to alter system behavior. Results are presented showing the application of this approach on datasets involving several multi-dimensional thematic layers of environmental data, used in mineral exploration.
Visualizing Spatial Data: The Problem of Paradigms
Authors: Robertson Philip K.
Published: October 2003

This paper describes the problem of developing working paradigms foradvanced spatial data applications. The key role of interactive visualization in enabling the expertise of specialists, if effectively integrated into their working environments, is described. The scope forapplying intelligence in designing visualizations to support,rather than to supplant, the expert is explored. A systematic framework describing the visualization design process, and an approach to applying intelligence around metavisualizations of the visualization design process, are summarized.
The Visitors Guide: A Simple Video Reuse Application
Authors: Shearer Kim , Venkatesh Svetha , Kieronska Dorota
Published: October 2003

One of the results of the surge in interest in the internet is the great increase in availability of pictorial and video data. Web browsers such as Netscape give access to an enormous range of such data. In order to make use of large amounts of pictorial and video data, it is necessary to develop indexing and retrieval methods.Pictorial databases have made great progress recently, to theextent that there are now a number of commercially available products. Video databases are now being researched and developed from a number ofdifferent viewpoints.Given a general indexing scheme for video, the next step is to reuse clipsin further applications.

In this paper we present an initial application for the reuse of video clips. The aim of the system is to resequence video clips for a particularapplication. We have chosen a well-constrained application for this purpose,the aim being to produce a video tour of a campus between designatedstart and destination points from a set of indexed videoclips. We use clips of a guide entering and leaving buildings on ourcampus, and when visitors select a start location and a destination, the systemwill retrieve clips suitable for guiding the visitor along the correct path.The system uses an index of spatial relationships of key objects for thevideo clips to decide which clips provide the correct sequence of motionaround the campus.

Although the full power of the indexing notation is unnecessary for this simple problem, the results from this initial implementation indicate that the concept could be applicable to more complex problems.
Conceptual Representation for Multimedia Information
Authors: Smith Roger W. , Kieronska Dorota , Venkatesh Svetha
Published: October 2003

Multimedia information is now routinely available in the forms of text, pictures, animation and sound. Although text objects are relatively easy to deal with (in terms of information search and retrieval), other information bearing objects (such as sound, images, animation) are more difficult to index. Our research is aimed at developing better ways of representing multimedia objects by using a conceptual representation based on Schank's conceptual dependencies. Moreover, the representation allows for users' individual interpretations to be embedded in the system. This will alleviate the problems associated with traditional semantic networks by allowing for coexistence of multiple views of the same information. The viability of the approach is tested, and the preliminary results reported.
On-Line Chinese Character Recognition Via a Representation of Spatial Relationships Between Strokes
Authors: Chen Ju-Wei , Lee Suh-Yin
Published: October 2003

Chinese characters are constructed by basic strokes based on structural rules. In handwritten characters, the shapes of the strokes may vary to some extent, but the spatial relations and geometric configurations of the strokes are usually maintained. Therefore these spatial relations and configurations could be regarded as invariant features and could be used in the recognition of handwritten Chinese characters. In this paper, we investigate the structural knowledge in Chinese characters and propose the stroke spatial relationship representation (SSRR) to describe Chinese characters. An On-Line Chinese Character Recognition (OLCCR) method using the SSRR is also presented. With SSRR, each character is processed and is represented by an attribute graph. The process of character recognition is thereby transformed into a graph matching problem. After careful analysis, the basic spatial relationship between strokes can be characterized into five classes. A bitwise representation is adopted in the design of the data structure to reduce storage requirements and to speed up character matching. The strategy of hierarchical search in the preclassification improves the recognition speed. Basically, the attribute graph model is a generalized character representation that provides a useful and convenient representation for newly added characters in an OLCCR system with automatic learning capability. The significance of the structural approach of character recognition using spatial relationships is analyzed and is proved by experiments. Realistic testing is provided to show the effectiveness of the proposed method.
A Belief-Based Approach for Adaptive Image Processing
Authors: Murino Vittorio , Foresti Gian Luca , Regazzoni Carlo S.
Published: October 2003

This paper proposes a new approach to the problem of intelligently regulating image-processing parameters of a distributed network. The proposed approach is based on two-step probabilistic process:

(a) belief updating, which consists in computing a functional cost at each node of the network and,

(b) belief maximization, which depends on maximizing this functional cost by using a stochastic optimization algorithm.

The architecture of an image processing system, consisting of three modules connected in a chain-like structure, is presented as an example showing the capabilities of the proposed approach. Each module is provided with a priori information about the set of parameters that manage a particular data transformation, and with evaluation criteria to judge data quality and to decide on the parameters to be adjusted. Experimental results obtained by using a digitally controlled camera and lens objective, are presented to show the validity of the proposed approach.
A Width-Independent Sequential Thinning Algorithm
Authors: Bhattacharya Prabir , Lu Xun
Published: October 2003

We propose a new sequential width-independent thinning algorithm for binary images. The algorithm uses a 4-neighbor distance transformation, and is designed to preserve the topological properties and shape of the object to be thinned. Comparison of the run time with a standard algorithm is given.
Setting Attribute Weights for Nearest Neighbor Learning Algorithms Using C4.5
Authors: Ling Charles X. , Parry John J. , Wang Handong
Published: October 2003

Nearest Neighbour (NN) learning algorithms utilize a distance function to determine the classification of testing examples. The attribute weights in the distance function should be set appropriately. We study situations where a simple approach of setting attribute weights using decision trees does not work well, and design three improvements. We test these new methods thoroughly using artificially generated datasets and datasets from the machine learning repository.