bluuebunny/crossref_metadata_2025 huggingface dataset:
ON A DYNAMICS APPROACH TO WETTING TRANSITIONS
Authors: HUANG Z. Q. , DING E. J. , CHEN J. Y.
Published: November 2004

In a recent development, wetting transition is considered in the dynamics approach in which the wetting problem of the Sullivan model is equivalent to a classical particle moving in a force field. This article reviews this recent development for modeled solid-fluid interfaces and phase transitions in confined fluids. A simple dynamics approach within van der Waals framework is formulated and applied to various wetting problems which are transformed into problems in classical dynamics. Emphasis is placed on the order of the transitions.
HETEROJUNCTION BAND DISCONTINUITY CHANGE BY ULTRATHIN INTRALAYER: Na
Authors: XU SHIHONG , LIU XIANMING , MA MAOSHENG , ZHU JINGSHENG , ZHANG YUHENG , XU PENGSHOU , XU ZHENJIA
Published: November 2004

The changes of band offset of Ge-GaAs(100) heterojunction are observed by means of an ultrathin Na intralayer with the photoemission spectroscopy. 1 ML Na intralayer increases the valence-band discontinuity of Ge-GaAs by 0.19 eV on the average.
EFFECT OF THE LOCAL SUBSTITUTION OF Co FOR Cu(1) ON THE ELECTRONIC STRUCTURE OF YBa2Cu3O7
Authors: GE JIU-YUAN , ZHOU YUN-SONG , ZHONG LI-YUAN , WANG HUAI-YU
Published: November 2004

The electronic density of states (DOS) of both pure and Co-substituted YBa 2 Cu 3 O 7 has been calculated by a recursion method. The results show that the total DOS at the Fermi level of YBa 2 Cu 3 O 7 mainly comes from the contributions of the O 2p and Cu 3d orbitals. After Co doping, the O 2p–Cu 3d bonds are destroyed while the O 2p–Co 3d bonds are formed at lower energies, and the total DOS at the Fermi level decreases strikingly. In addition, our results reveal that the CuO chain has a one-dimensional feature.
CHARGE-SPIN SEPARATION, FRACTIONAL STATISTICS AND SUPERCONDUCTIVITY IN THE t-J MODEL
Authors: WENG Z. Y. , SHENG D. N. , TING C. S.
Published: November 2004

A generalized slave-particle scheme is introduced to the t-J model including the non-local effects. We find a charge-spin decoupled state in which the non-local gauge fields play the roles of statistics-transmutation. As a result, the gauge fluctuation becomes massive and the electromagnetic response function exhibits the Meissner effect, like in the free-semion system, but without breaking the time-reversal and parity symmetries due to the cancellation between charge and spin degrees of freedom in the low-energy, long-wavelength regime. We also calculate the momentum distribution of electrons which shows a characteristic scale equals to the Fermi momentum kf.
PREPARATION OF BiPbSrCaCuO SILVER CLAMP THICK FILM AND TRANSPORT CURRENT CHARACTERISTIC
Authors: WANG YUGUI , HAN HANMIN , HAN GUCHANG , WANG SHUNXI , WANG ZHIHE
Published: November 2004

Bi(2223) silver clamp thick films with nominal composition Bi 1.8 Pb 0.4 Sr 2 Ca 2 Cu 3 O y were prepared through physical deposition on Ag-plate. The influence of silver clamp on the phase growth was studied. The Ag clamp can prevent the volatizable composition of oxygen material such as Pb from evaporation during heat treatment process, and make thick film in the atmosphere of low oxygen pressure, thus accelerating the transition from 80 K phase to 110 K phase. For the sample sintered and cool-pressed 3 times, the critical current density was 22 kA/cm 2 at 77.3 K and zero magnetic field. At H = 1 T , Jc = 2.8 kA/cm 2. When H exceeds 4 T, supercurrent almost disappeared. The transport current characteristic indicates that there exists weak link among grains. The influence of cooling cycles on Jc is also discussed.
ON THE THEORY OF THE ONE-DIMENSIONAL LUTTINGER LIQUID
Authors: MINIC DJORDJE
Published: November 2004

Basic properties of the one-dimensional Luttinger liquid are studied from the point of view of an effective conformal field theory.
THE d-DISTANCE PROPERTY OF d-SYMBOLIC QUASIPERIODIC SEQUENCES
Authors: IGUCHI KAZUMOTO , YOSHIKAWA TOSHIO
Published: November 2004

We prove the d-distance property of d-symbolic quaisperiodic sequences by using the ray approach, which was recently introduced by Iguchi.
STRINGS COMPLETE THE SPECTRUM OF 1-D δ-FUNCTION FERMIONS
Authors: WILLIAMS ERIC D.
Published: November 2004

We study the completeness of the nested Bethe ansatz eigenfunctions for a one dimensional gas of spin-1/2 fermions interacting via a repulsive delta-function potential. We show the completeness of the eigenfunctions for a system in an infinite box with N fermions and the orientation of either one or two of the spins differing from the rest. This demonstrates that the spin bound states (also called Λ-strings) are necessary for completeness of the spectrum.
BREAKDOWN OF LANDAU FERMI LIQUID IN 2D
Authors: CHEN HUA , MATTIS DANIEL
Published: November 2004

We study the paramagnetic phase of the Hubbard model at low density in 2D. In addition to the Landau Fermi liquid phase at small U > 0, in which fk is discontinuous at kF, we find a novel "Quantum Fermi Liquid" (QFL) phase for [Formula: see text](≈ 17 ∊F) in which fk is continuous at kF but df/dk|F = −∞. The lifetime of QFL quasiparticles at kF is τ ∝ T−1 (rather than T−2). The phenomenological "Marginal Fermi Liquid" is identified as a special case of the QFL at [Formula: see text] precisely.
ELECTRICAL CONDUCTIVITY OF COBALT-SUBSTITUTED BaZn-W HEXAGONAL FERRITES
Authors: REDDY V. DEVENDER , REDDY P. VENUGOPAL
Published: November 2004

The D.C. electrical conductivity of cobalt substituted BaZn-W hexagonal ferrites has been studied as a function of composition and temperature over a temperature range of 300–800 K. It has been observed that the cobalt doping has no influence on the RT values of electrical conductivity, although it does affect many other physical properties. For the first time, the authors noticed two clear and distinct transitions in the conductivity vs. temperature plots of all the samples, the first being ≈475 K and the second near their Curie temperatures. The transition T1 has been attributed to the spin reorientation while the second could be due to the Curie temperature. The activation energy values obtained for the paramagnetic region are found to be higher than those of the ferrimagnetic one for all the samples.
SPONTANEOUS MAGNETIZATION OF THE ISING MODEL ON THE UTIYAMA LATTICE
Authors: LIN K.Y. , CHU C.C.
Published: November 2004

We have calculated exactly the spontaneous magnetization of the two-dimensional Ising model on a particular case of the Utiyama lattice. Our result includes the square, triangular, honeycomb, and 4–8 lattices as special cases.
TIME-RESOLVED STUDY OF PHONON-POLARITONS IN LiTaO3 AT ROOM TEMPERATURE
Authors: HUNSCHE S. , BAKKER H.J. , KURZ H.
Published: November 2004

We present a time-resolved study of phonon-polaritons in the ferroelectric LiTaO 3 at room temperature. The coherent generation and phase-sensitive detection of polaritons, using femtosecond Laser pulses, allow precise determination of polariton frequencies and dephasing times. The experimental data clearly show a resonance at 0.95 THz that has not been found in previous IR and Raman studies. The simultaneous coherent excitation of polaritons in the upper and the lower dispersion branch associated with this resonance leads to the observation of phonon-polariton beats, A quantum-mechanical model of the lowest A 1 lattice vibration in LiTaO 3 is developed, which provides a quantitative description of the low-frequency dielectric response, including the polariton dispersion and dephasing. Within this model, the transition at 0.95 THz can be identified as a classically forbidden tunneling resonance.
DISCONTINUOUS PHASE TRANSITION OBTAINED WITH THE THERMAL BOSON EXPANSION FOR THE HEISENBERG FERROMAGNET
Authors: BRAJCZEWSKA M. , FIOLHAIS C. , PROVIDÊNCIA J. DA
Published: November 2004

Spin waves at finite temperature of an Heisenberg ferromagnet (S=1/2) have been defined in the framework of the thermal boson expansion. We analyze the discontinuous phase transition which appears when this theory of thermal magnons breaks down. Temperatures corresponding to a maximal superheating point, T1, a minimal supercooling point, T0, and a transition point, TC, such that T0≤TC≤T1, have been identified. The temperature TC agrees closely with the “exact” critical temperature known for the model.
INVESTIGATION OF QUANTUM TRANSMISSION EFFECT ON PROPERTY OF PLANAR-DOPED BARRIER DIODE
Authors: SHENG HANYU , CHUA SOO-JIN
Published: November 2004

The quantum-mechanical effect on the current-voltage characteristic of a planar-doped barrier diode is investigated. The results show that the transmission coefficient will reach 1 when the energy of the incident electron is 2/3 the barrier height. For a specific energy, the transmission coefficient will dramatically decrease with increasing barrier thickness. Comparing with the thermionic emission current, the quantum effect current becomes larger at higher bias.
MODELING MESOSCALE DYNAMICS OF FORMATION OF δ′-PHASE IN Al-Li ALLOYS
Authors: GOLDSTEIN R.S. , ZIMMER M.F. , OONO Y.
Published: November 2004

A mesoscale minimal model study of the α−δ′ two-phase system is presented. A minimal model free energy is introduced which reveals universal features of the ordering dynamics of the disordered into the L1 2 ordered state. Static phenomenological parameters of the minimal model are chosen to reproduce the equilibrium phase diagram, and dynamical ones are chosen to reproduce recent experimental scattering results by H. Chen’s group.
SCANNING TUNNELING MICROSCOPY DETERMINATION OF THE REACTION PATH OF Sb4 ON Si(001)
Authors: MO Y. W.
Published: November 2004

The complex reaction path of the chemisorption of Sb 4 on Si(001) is directly determined with the scanning tunneling microscopy. Four distinct types of precursors are observed which can be converted to the final state either by thermal annealing or by a STM tip-induced conversion process. The thermal conversion path of the precursors to the final state is identified.
STUDIES OF F ON SUPERCONDUCTIVITY IN HIGH-Tc (Bi,Pb)SrCaCu(O,F) SUPERCONDUCTORS
Authors: CAI JIANGUO , ZHANG XIAOLONG , ZHOU XIANGHUA , WEI QIN
Published: November 2004

In this article, the experimental results of the superconductivity in high-Tc (Bi,Pb) 2 Sr 2 Ca 2 Cu 3( O y, F x), x = 0–0.84, is described. Its critical current density Jc is about ten times larger than that of undoped F sample undergoing the same technology. The causes for the increase in Jc are studied by several experimental methods. The difference in quantity between Meissner effect and shield effect indicates that the effect on superconductivity is from the weak-link regions of the superconductor grains. SEM shows that F atoms doped in BPSCCO superconductor can make its grains grow larger, arrange regularly, and increase in touch area. These changes strengthen the netty link between grains. The magnitude of residual magnetization of F-doped sample is eight times as large as that of the undoped one. The flux pinning potential U0 is calculated from the Bean model. The U0 in F-doped sample (when H = 64 Oe, x = 0.64) is eight times as large as that in the undoped one.
X-RAY ABSORPTION STUDIES OF MIXED-VALENT BI OXIDES WITH PEROVSKITE STRUCTURE
Authors: BERGHÖFER GERD , REINEN DIRK , AKHTAR GHULAM , HORMES JOSEF
Published: November 2004

X-ray absorption near edge spectra (XANES) have been measured on the Bi M 5 edge of the semiconducting perovskite-type solid solution Ba 1+x Bi 1−x O 3−δ (−0.43 ≤ x ≤ 0.43) and of superconducting Ba 0.6 K 0.4 BiO 2.93. The results are interpreted on the basis of the mean Bi valence as determined by iodometric analyses. The near edge spectra and the pre-edge features of the semiconducting samples show distinct differences ascribable to separate Bi(III) and Bi(V) oxidation states, in agreement with the structural results, and their relative intensities directly reflect the Bi(V) content. The spectrum of superconducting Ba 0.6 K 0.4 BiO 2.93 is comparable to the spectra of the semiconducting compounds with a similar Bi oxidation state, with an additional absorption about 20 eV beyond the absorption edge, however. Structural data are also presented.
SYNTHESIS OF NEW 1223-TYPE SUPERCONDUCTING LAYERED CUPRATE (Tl,Cr)Sr2Ca2Cu3O9
Authors: CHEN Z. Y. , SHENG Z. Z. , LI Y. F. , PEDERSON D. O.
Published: November 2004

A new 1223-type (Tl,Cr)-based superconducting layered cuprate ( Tl 1−x Cr x) Sr 2 Ca 2 Cu 3 O 9 with x = 0.25 or 0.50 has been successfully synthesized in the pure or nearly pure form and identified by powder X-ray diffraction analyses. An excessive quantity of thallium is necessary for the formation of the (Tl,Cr)-based 1223-type compound without any Ba. Resistance measurements showed that the new (Tl,Cr)-based 1223 cuprate exhibits Tc(onset) above 100 K and Tc(ρ = 0) of 94 K. Effects of the Cr amount and preparation conditions on the formation and superconductivity of the (Tl,Cr)-based 1223-type cuprate are discussed.
THE EXPERIMENTALLY OBSERVED OPTICAL COTTON–MOUTON EFFECT: EVIDENCE FOR THE PHOTON'S LONGITUDINAL MAGNETIC FIELD, B(3)
Authors: EVANS M. W.
Published: November 2004

The recent experimental observation of the optical Cotton–Mouton effect is consistent with the induction of magnetization by the longitudinal component of the photon's magnetic field, whose classical counterpart is the equivalent flux density B(3). In the optical Cotton–Mouton effect observed by Zon et al.,16 the field B(3) acts at second order and is independent of the polarization of the inducing laser beam propagating parallel to a permanent magnetic field. The optical Cotton–Mouton effect is therefore proportional to the laser intensity as observed.16
QUANTUM GROUPS, SQUEEZING, BLOCH, AND THETA FUNCTIONS
Authors: CELEGHINI E. , DE MARTINO S. , DE SIENA S. , VITIELLO G. , RASETTI M.
Published: November 2004

We realize the deformation of the Weyl–Heisenberg algebra in terms of finite difference operators within the Fock–Bargmann representation. This allows us to incorporate in a unified q-algebra structure, the notions of squeezing and lattice quantum systems resorting to the properties of theta functions.
DEFECT THEORY OF SOLID–LIQUID TRANSITION AND INTERFACE
Authors: FERRAZ A.
Published: November 2004

In this work, we develop a field theory model for the solid–liquid transition and planar interface induced by dislocation lines in an elastic continuum. We show that the phase transition which emerges from our model is of first order kind. We calculate the interface solution, the surface tension and, finally, we end up discussing the stability of the field solutions.
SU(2) TO U(1) MICROSCOPIC TRANSITION IN THE HEISENBERG CHAIN
Authors: CARMELO J. M. P. , LIN H. Q.
Published: November 2004

We find that the nature of the gapless low-energy excitations of the spin 1/2 isotropic Heisenberg chain with J < 0 (antiferromagnetic chain at magnetic field H = 0) is different in the usual SU(2) "phase" and in the finite-magnetic field "phase" of symmetry U(1). This is shown to have relevant consequences for the microscopic description of the low-energy physics, which is different from the usual "spinon" two-kink picture. The use of the until now hidden "Landau-liquid" character of the model reveals a number of unexpected aspects of its physics and deepens the microscopic understanding of this fundamental quantum system.
EXACT GROUND STATE OF THE GENERALIZED HUBBARD MODEL FOR A WIDE RANGE OF PARAMETERS
Authors: OVCHINNIKOV A. A.
Published: November 2004

We present the exact ground-state wave function and energy of the generalized Hubbard model, subjected to the condition that the number of doubly-occupied sites is conserved for a wide physically relevant range of parameters. For one hole and one doubly-occupied site, the existence of the ferromagnetic ground state is proved which allows one to determine the critical value of the on-site repulsion corresponding to the point of metal–insulator transition.
SUPERCONDUCTING MAGNETIC ENERGY STORAGE: CONVENTIONAL AND TRAPPED FIELD
Authors: RABINOWITZ MARIO
Published: November 2004

Superconducting magnetic energy storage (SMES) is a most efficient system for energy storage because it stores energy directly in electrical form. The SMES concept is described and analyzed with an examination of its economic viability. The impact of high-temperature supeconductivity on SMES is explored, and a trapped energy storage (TES) innovation that may have beneficial technical and economic ramifications is introduced. In addition to presenting a broad overview, this paper may be of help to those making an evaluation of the potential impact of SMES/TES on the development of new energy sources, and to determine for which energy sources it is most appropriate.
CHAOS AND QUANTUM FLUCTUATIONS IN A QUARTIC HAMILTONIAN SYSTEM
Authors: JOY M. P. , SABIR M.
Published: November 2004

Quantum chaos in a quartic oscillator system given by [Formula: see text] is studied using Gaussian Effective Potential method. It is shown that though quantum fluctuations reduce chaos, there is a correspondence between classical behavior and quantum behavior with regard to integrability and chaos.
THE EXACT SOLUTION OF THE BCS SELF-CONSISTENCY EQUATION AND THE IMPLICATIONS
Authors: HAO ZHIDONG
Published: November 2004

The existence of a first order differential equation for the temperature dependence of the energy gap parameter Δk for each k state is pointed out. By using this equation, exact solution for the energy and temperature dependences of Δk is obtained. The energy range over which Δk is appreciable is within a few kBT c around the Fermi surface. Each k state may have its own temperature T c k, above which Δk = 0. In general, these T c k are not necessarily the same for all k states (the superconducting transition temperature T c corresponds to the largest T c k). Limitations of the BCS cutoff approximation are pointed out.
BEHAVIOR OF STEP EDGES ON Si(001)
Authors: ZANDVLIET H.J.W. , ELSWIJK H.B.
Published: November 2004

The morphology of monatomic step edges on vicinal Si (001) surfaces is briefly reviewed. With increasing miscut angle, the Si (001) surface exhibits an interesting sequence of phase transitions. For a miscut angle smaller than about 0.03°, a hilly structure with step loops is found, whereas a phase of wavy steps coexisting with a phase of straight steps is observed in the range of 0.03°–0.1°. If the miscut angle lies in the range of 0.1° up to about 3°, two types, one much straighter than the other, of monatomic step edges develop. For even larger miscut angles, a phase of straight biatomic step edges is found.

The fundamental energetic parameters, like kink formation energies, step edge energies and step-step interactions, which govern the thermodynamic behavior are determined using Scanning Tunneling Microscopy (STM) images of 0.5° misoriented Si (001). Despite the weak strength of energetic and entropic step-step interactions as compared to the interactions along the step edge, i.e. the kink formation and step edge energies, they have a profound effect on the meandering of the step edges. Both entropic and energetic step-step interactions are proportional to L−2 (where L is the average terrace length). The behavior of the step edges at temperatures above room temperature will be addressed with the aid of a high-temperature STM. The freeze-out temperature, T f , of the monatomic step edges is estimated to be higher than 600–700 K. The temperature T f is significantly above the roughening temperature, Tr, of the step edges. This means that at room temperature, the monatomic step edges on vicinal Si (001) are always rough.
VARIATIONAL STUDY ON INSTABILITY OF NAGAOKA STATE IN A THERMODYNAMIC LIMIT
Authors: SHEN SHUN-QING , QIU ZHAO-MING
Published: November 2004

In this paper, we have rigorously shown that, in a thermodynamic limit, there always exists a one-spin-flipped state degenerate with the Nagaoka state in one-band Hubbard model on a two and three-dimensional simple cubic lattice when the number of holes [Formula: see text] (with 0≤α<1, N∧ and N e are the numbers of sites and electrons respectively) for all U (including U=∞). It is also shown that there does not exist a finite critical value U c for which, when U>U c , the Nagaoka state has the ground-state energy of the system for a two-dimensional square lattice when ρ→0.
THE QUASICLASSICAL LOCALIZATION OF THE STATES AND OBTAINING OF CLASSICAL EQUATIONS OF MOTION FROM QUANTUM THEORY
Authors: BAGROV V.G. , BELOV V.V. , ROGOVA A.M. , TRIFONOV A. YU.
Published: November 2004

The concept of quasiclassically localized states is defined and the theorem about the possibility of the quasiclassical localization on the phase trajectories only (solutions of corresponding classical equations of Hamilton) is proved.
FLUCTUATION EFFECTS IN A CLASS OF SYSTEMS WITH TWO ORDER PARAMETERS
Authors: CESARE L. DE , RABUFFO I. , UZUNOV D.I.
Published: November 2004

The phase transitions described by coupled spin -1/2 Ising models are investigated with the help of the mean field and the renormalization group theories. Results for the type of possible phase transitions and their fluctuation properties are presented. A fluctuation-induced second-order phase transition is predicted.
CLUSTER VARIATION APPROACH TO THE ANTIFERROMAGNETIC TRANSITION OF THE t-J MODEL
Authors: DANANI ANDREA , PELIZZOLA ALESSANDRO
Published: November 2004

The antiferromagnetic phase transition associated with the breaking of the magnetic SU(2) symmetry of the t-J model is investigated by means of the cluster variation method in the pair approximation. The disordered and antiferromagnetic phases are characterized by means of their symmetry properties, and an analytical implicit expression is given for the Néel temperature.
UNIFORM UPPER BOUNDS IN THE FRÖHLICH POLARON THEORY
Authors: BOGOLUBOV N.N. , SOLDATOV A.V.
Published: November 2004

We present a very simple method to derive the upper bound of the ground-state energy for the Fröhlich polaron theory. The obtained bounds are proved to be uniform for all values of the interaction parameter.
THERMO FIELD DYNAMICS OF DEFORMED SYSTEMS
Authors: MONTEIRO M.R.- , RODITI I.
Published: November 2004

We discuss the formalism of Thermo Field Dynamics for deformed systems. We apply this method to the study of the statistics of q-bosonic oscillators.
DICKE HAMILTONIAN AND SUPERRADIANT PHASE TRANSITIONS
Authors: GIUDICE E. DEL , MELE R. , PREPARATA G.
Published: November 2004

We show that a correct analysis of the gauge-invariance properties of the em coupling of atomic systems with single-mode em radiation fields allows to overcome the “no-go” theorem for superradiant phase transitions in systems governed by the Dicke Hamiltonian
AUTOMATIC DETECTION OF HANDWRITING FORGERY USING A FRACTAL NUMBER ESTIMATE OF WRINKLINESS
Authors: CHA SUNG-HYUK , TAPPERT CHARLES C. , GIBBONS MICHAEL , CHEE YI-MIN
Published: November 2004

We investigate the detection of handwriting forged by novices. To facilitate document examination it is important to develop an automated system to identify forgeries, or at least to identify those handwritings that are likely to be forged. Because forgers often carefully copy or trace genuine handwriting, we hypothesize that good forgeries — those that retain the shape and size of genuine writing — are usually written more slowly and are therefore wrinklier (less smooth) than genuine writing. From online handwriting samples we find that the writing speed of the good forgeries is significantly slower than that of the genuine writings. From corresponding offline samples we find that the wrinkliness of the good forgeries is significantly greater than that of the genuine writings, showing that this feature can help identify candidate forgeries from scanned documents. Using a total of eight handwriting distance features, including the wrinkliness feature, we train a neural network to achieved 89% accuracy on detecting forged handwriting on test samples from ten writers.
SEPARATING FIGURES, MATHEMATICAL FORMULAS AND JAPANESE TEXT FROM FREE HANDWRITING IN MIXED ONLINE DOCUMENTS
Authors: MOCHIDA KEISUKE , NAKAGAWA MASAKI
Published: November 2004

This paper describes a method for separating online handwritten patterns into Japanese text, figures and mathematical formulas. Today, Tablet PCs and electronic whiteboards provide much larger writing area for pen interfaces unlike PDAs (Personal Digital Assistants), through which users can easily input text, write mathematical formulas and draw figures on the screen. The fact that these objects can be written by a single pen (marker) without switching the device, mode, software or whatever else, and without any writing restrictions such as grids or boxes is one of the most important benefits of the pen interfaces. However, the task of segmenting these objects is challenging. To address this issue, we have applied a probabilistic model employing stroke features, stroke crossings and stroke densities. Further, we partially apply the approach of segmentation by recognition. Although the current recognizer for formulas is not a true recognizer, we have achieved about 81% correct segmentation for all the strokes when applied to our newly prepared database of mixed patterns. This method has been compared with a neural-network. The results show that our method is generally better but less effective in distinguishing figures from other components.
THE GENERATION OF VELOCITY PROFILES WITH AN ARTIFICIAL SIMULATOR
Authors: DJIOUA MOUSSA , PLAMONDON RÉJEAN
Published: November 2004

A few years ago, a Kinematic Theory was proposed to analyze rapid human movements. The theory is based on a delta-lognormal equation which can be used to globally describe the basic properties of velocity profiles using seven parameters. This realistic model has been of great use to solve pattern recognition problems (signature verification, handwriting analysis and segmentation, etc.). To go further in that direction, a better understanding of the model is a prerequisite. This can be either in the context of psychophysical studies involving human subjects or in the context of computer simulations. In this paper, we use the same model form to develop a simulator that generates human-like velocity profiles. A basic subsystem model is both proposed and constructed with a Simulink Matlab tool; then many of these are connected to create an artificial neuromuscular network. Combining two networks in parallel, one agonist and the other antagonist, a synergy simulator is constructed. The similarity of the velocity patterns produced by the simulator is analyzed using a delta-lognormal parameter extractor. It is shown that the parameters extracted from artificially generated profiles vary in the same intervals as those of experimental profiles produced by human subjects. In future works the simulator tool will be used to study the control of rapid human movements.
ASSESSING VISUO-SPATIAL NEGLECT THROUGH FEATURE SELECTION FROM SHAPE DRAWING PERFORMANCE AND SEQUENCE ANALYSIS
Authors: CHINDARO SAMUEL , GUEST RICHARD , FAIRHURST MICHAEL , POTTER JONATHAN
Published: November 2004

The reported work aims to objectively and accurately assess the post-stroke clinical condition of visuo-spatial neglect using a series of standardized geometric shape drawing tasks. We present a method implementing existing pencil-and-paper diagnostic methods and define a set of static and dynamic features that can be extracted from drawing responses captured online using a graphics tablet. We also present a method for automatically assessing the constructional sequence of the drawing using Hidden Markov Models. The method enables the automated extraction, position identification and drawing order of individual sides of a shape within a drawing. Discrimination between two populations (a neglect population and stroke subjects without neglect as determined by existing standard assessment methods) using a combination of performance features and constructional sequence is examined across three separate drawing tasks. Results from experimentation show how a combination of sequence and performance features is able to generalize across a wide variety of input samples and obtain a diagnostic classification which can be used alongside other forms of conventional assessment. Furthermore, the application of a multi-classifier combination strategy leads to a significant increase in recognition ability.
A SPEECH UNDERSTANDING SYSTEM FOR INFORMATION RETRIEVAL
Authors: BAGGIA P. , FISSORE L. , GIACHIN E. , MICCA G. , RULLENT C. , LAFACE P.
Published: November 2004

This paper describes a Continuous Speech Understanding System that allows information services to be accessed through the telephone line. It accepts queries within a restricted semantic domain, expressed in free but syntactically correct natural language, with a lexicon of the order of 800 words. In the implementation here described, a user can access an electronic mailbox or a train information service through a PABX telephone line.

The architecture of the system is based on two main modules that represent and use different knowledge sources. A speaker independent recognition module generates, for each utterance, a lattice of word hypotheses which is the interface to an understanding module that performs the syntactic and semantic analysis. The recognition module is based on Hidden Markov Models of subword units, and performs the acoustic decoding process according to a beam search strategy. The understanding module finds the most likely sequence of words and represents its meaning in a format which facilitates the access to a database. It makes use of a modified caseframe analysis guided by the word hypotheses scores.

Experiments were performed with 600 sentences from 10 speakers on the E-Mail application task. Using 15 Gaussian mixtures per state, a word accuracy of 75.7 was obtained with a test vocabulary of 787 words and no linguistic constraints. Linguistic processing of the corresponding lattices achieved a sentence understanding rate of 82%.
KNOWLEDGE-BASED TECHNIQUES IN ACOUSTIC-PHONETIC DECODING OF SPEECH: INTEREST AND LIMITATIONS
Authors: FOHR DOMINIQUE , HATON JEAN-PAUL , LAPRIE YVES
Published: November 2004

A major step in the process of speech understanding is the acoustic-phonetic decoding which can be defined as the automatic mapping of the continuous speech wave into a set of predetermined linguistic units such as phones, diphones, syllables, etc. This paper relates to the approach of this problem which consists in exploiting an explicit description of all kinds of available knowledge about the speech communication phenomena, in the general framework of an artificial intelligence knowledge-based system.

We will first recall the main difficulties of acoustic-phonetic decoding with a practical example. We will then present the APHODEX system that we have been designing for the past eight years, in terms of software architecture and of knowledge representation and reasoning. The practical evaluation of this system will then be carried out at the different levels of feature extraction, segmentation and labelling. Finally, we will discuss the limitations of our approach and present the ongoing effort to overcome these limitations, especially through the use of abductive reasoning.
ACOUSTIC-PHONETIC DECODING OF SPANISH CONTINUOUS SPEECH
Authors: GALIANO I. , SANCHIS E. , CASACUBERTA F. , TORRES I.
Published: November 2004

The design of current acoustic-phonetic decoders for a specific language involves the selection of an adequate set of sublexical units, and a choice of the mathematical framework for modelling the corresponding units.

In this work, the baseline chosen for continuous Spanish speech consists of 23 sublexical units that roughly correspond to the 24 Spanish phonemes. The process of selection of such a baseline was based on language phonetic criteria and some experiments with an available speech corpora.

On the other hand, two types of models were chosen for this work, conventional Hidden Markov Models and Inferred Stochastic Regular Grammars. With these two choices we could compare classical Hidden Markov modelling where the structure of a unit-model is deductively supplied, with Grammatical Inference modelling where the baseforms of model-units are automatically generated from training samples.

The best speaker-independent phone recognition rate was 64% for the first type of modelling, and 66% for the second type.
CONTEXT-SENSITIVITY OF PUZZLE GRAMMARS
Authors: LAROCHE P. , NIVAT M. , SAOUDI A.
Published: November 2004

We study some properties of array grammars, called puzzle grammars, introduced in Ref. 7. We give a new method, using puzzle grammar, for generating the set of rectangles. We prove that the emptiness problem for puzzle grammar is undecidable. We show that the non-overlapping problem for puzzle grammar is decidable.
COMPONENT-ORIENTED ALGORITHMS FOR SIGNATURE VERIFICATION
Authors: DIMAURO G. , IMPEDOVO S. , PIRLO G.
Published: November 2004

Signing is a complex and highly variable process. It results from simple bodily motions of a ballistic nature whose combined effects produce the fundamental components of the signature. Therefore, signature verification can be performed by adopting local verification strategies for the detection of personal characteristics in fundamental components.

In this paper, an on-line component-oriented signature verification system is presented. During the training phase, the set of fundamental components of each signer is derived and a suitable component-oriented knowledge-base is created by an automated technique. The verification is accomplished through a step-wise process. In the first step the structural organization of the signature is checked. In the second step each component is examined using spectral analysis. The experimental result shows the effectiveness of this approach compared with other techniques in the literature.
THE DESIGN OF AN ON-LINE SIGNATURE VERIFICATION SYSTEM: FROM THEORY TO PRACTICE
Authors: PLAMONDON RÉJEAN
Published: November 2004

This paper reports on the major decisions that have to be made throughout the design phase of an automatic signature verification system. It shows how knowledge about signature control and generation, in terms of a realistic mathematical and psychophysical model, can be helpful in guiding and orienting design choices and related research activities. A system designed according to this methodology is described and the results of a robust forgery test are presented.
A NEW PARALLEL THINNING METHODOLOGY
Authors: ZHANG Y.Y. , WANG P.S.P.
Published: November 2004

A perfectly parallel thinning algorithm (PPTA) is proposed. It can generate perfect skeletons, which consist of end points, break points, and hole points only. Experimental results show that the proposed PPTA can also preserve image connectivity, produce thinner skeletons, and is faster than many existing thinning algorithms. For example, it is twice as fast as one of the fastest parallel thinning algorithm by Holt, Stewart, Clint and Perrorte.
AUTOMATIC INPUT OF LOGIC DIAGRAMS BY RECOGNIZING LOOP-SYMBOLS AND RECTILINEAR CONNECTIONS
Authors: KIM SOO HYUNG , KIM JIN HYUNG
Published: November 2004

An automatic system that reads an image of a logic diagram, digitized by a document scanner, and generates a description of the diagram in terms of logic symbols and their interconnections is proposed. The digitized image is converted into a set of line segments by way of a sequence of picture processing operations, Then symbols and connections are recognized by identifying loops and rectilinear polylines. Graphical description of a set of symbol models is provided as prior knowledge about input diagrams.

Experiments show that the system can recognize more than 96% of logic symbols and connections and that an A4 size diagram (210×297 mm ) of average complexity can be processed within 10 seconds on a workstation.
EFFECTIVE COMPUTATION OF THE POINCARÉ MAP FOR THE ANALYSIS OF NONLINEAR DYNAMIC CIRCUITS/SYSTEMS USING RUNGE-KUTTA TRIPLES
Authors: FINGER L. , UHLMANN H.
Published: November 2004

An enhancement of the classical Runge—Kutta technique for numerical simulations is presented for the computer-aided global analysis of nonlinear dynamic circuits/systems. With Runge—Kutta triples a remarkable saving of calculation time can be achieved by using an interpolation polynomial for dense output. The Runge—Kutta triples are applied to calculate the Poincaré map for autonomous models/systems.
DIGITAL RESTORATION OF DAMAGED PHONOGRAPH RECORDS
Authors: KASPARIS TAKIS , LANE JOHN
Published: November 2004

A method for digital restoration of phonograph recordings contaminated by impulsive noise is proposed. Impulses are suppressed by applying median filtering on contaminated signal regions only, thus minimizing distortion of clean passages and loss of high musical frequencies. The algorithm can be implemented on a personal computer equipped with any inexpensive sound board, and thus it can be used for the restoration of damaged records in home collections. In experiments with old recordings the improvement in sound quality was dramatic. The restored audio signal can be archived in digital form on regular computer back-up tapes or on digital audio tapes, or it can be played through the sound board and stored onto an analog recording media such as high-quality cassette tapes.
ANALYSIS OF A CLASS OF NETWORKS BASED ON CUBIC STAR GRAPHS
Authors: MADABHUSHI S.V.R. , LAKSHMIVARAHAN S. , DHALL S.K.
Published: November 2004

A new class of interconnection networks based on a family of graphs, called cubic graphs are introduced. These latter graphs arise as Cayley graphs of certain subgroups of the symmetric group. It turns out that these Cayley graphs are a hybrid between the binary hypercube and the star graph, and hence are called cubic star graphs, and are denoted by CS(m, n), m≥1 and n≥1. CS(m, n) inherits several of the properties of the hypercube and the star graph. In this paper, we present an analysis of the symmetric and topological properties. In particular, it is shown that CS(m, n) is edge transitive and hence maximally fault tolerant. We give an algorithm for finding the shortest path and provide an enumeration of the node disjoint paths. Optimal algorithms for single source and all-source broadcasting (also called gossiping) are derived. It is shown that CS(m, n) is Hamiltonian and interesting embeddings of several cycles, grids, and binary trees are derived. The paper concludes with a comparison of CS(m, n) with the binary hypercube and the star graph.
BIFURCATION STRUCTURE IN A MODEL OF A FREQUENCY MODULATED CO2 LASER
Authors: MIRA C. , DJELLIT I.
Published: November 2004

This paper concerns the bifurcation properties of a model of a frequency modulated CO 2 laser in the form of a two-dimensional ordinary differential equation with a parametric periodic excitation. These properties are related to the bifurcation curves organization (structure) in a parameter plane (amplitude, frequency of the modulation). Two basic bifurcation structures appear, one concerning the higher harmonic solutions, the other the subharmonic solutions. Qualitative changes of these structures are considered when a third parameter (pump parameter) is varied.
NOISE REDUCTION BY GRADIENT DESCENT
Authors: DAVIES MIKE
Published: November 2004

The problem of reducing noise in a time series from a nonlinear dynamical system can be formulated as a nonlinear minimisation process. This paper demonstrates that this can be easily solved using a steepest descent method without any of the stability problems that have been associated with using a Newton method [Hammel, 1990; Farmer & Sidorowich, 1991]. The optimisation function to be minimised is also shown not to contain any local minima if the trajectory is always hyperbolic. So that in this case this method will converge eventually to a purely deterministic trajectory. Finally this method is compared with a recently proposed algorithm [Schreiber & Grassberger, 1991], which can be viewed as an alternative gradient descent method.
THE RECONSTRUCTION OF THE FOKKER-PLANCK AND MASTER EQUATIONS ON THE BASIS OF EXPERIMENTAL DATA: H-THEOREM AND S-THEOREM
Authors: KLIMONTOVICH Yu. L.
Published: November 2004

The method of reconstruction of Fokker-Planck and Master equations for nonlinear open systems on the basis of experimental time series is considered. In the process of time evolution the entropy of a system, renormalized to the given value of the mean effective energy, increases in accordance with the kinetic equations (H-theorem). The evolution of the renormalized entropy of stationary states in the space of rule (control) parameters is also considered (S-theorem).
VARIETY OF TYPES OF CRITICAL BEHAVIOR AND MULTISTABILITY IN PERIOD-DOUBLING SYSTEMS WITH UNIDIRECTIONAL COUPLING NEAR THE ONSET OF CHAOS
Authors: KUZNETSOV A.P. , KUZNETSOV S.P. , SATAEV I.R.
Published: November 2004

The dynamics of two unidirectionally coupled period-doubling systems is investigated depending on three relevant parameters (control parameters of subsystems and coupling). There is a hierarchy of critical behavior types. Feigenbaum’s critical surfaces existing in the parameter space are bounded by tricritical lines and intersect along the bicritical line. These lines, in turn, intersect at a new multicritical point BT. Universality and scaling properties for all the critical situations are discussed, and the table of critical indices is given.
THE INTERACTION OF STRUCTURES AND SPATIOTEMPORAL CHAOS IN MODELS OF COUPLED WAVES
Authors: BAZHENOV M.V. , RABINOVICH M.I.
Published: November 2004

Dynamic and stochastic effects of the interaction of individual localized structures and lattices of structures of a nonlinear field are considered within one-dimensional large-box Ginzburg-Landau and Swift-Hohenberg models. The criterion of soliton “survival” in competition with counterpropagating modes is derived analytically for a quasigradient case. The criterion of linear stability of a spatially homogeneous regime, that is similar to the Benjamin-Feir condition, is obtained for coupled Ginzburg-Landau equations. The relation between the correlation dimensions of the space series of counterpropagating modes and the dimension of the time series is investigated. It is shown that within a quasigradient model of two weakly coupled counterpropagating modes, the field can be represented as a superposition of two fixed stochastic spatial lattices which correspond to these modes and move through one another at constant velocity. The dimension of the time series at a given point in space is close to the sum of dimensions of the spatial distributions of counterpropagating modes. With the increase of coupling, the interaction of coupled modes “loosens” the equilibrium state corresponding to fixed lattices and the dimension of the time series grows.
TRAVELING WAVE PROPAGATION IN A ONE-DIMENSIONAL FLUCTUATING MEDIUM
Authors: PÉREZ-MUÑUZURI V. , GÓMEZ-GESTEIRA M. , PÉREZ-VILLAR V. , CHUA L.O.
Published: November 2004

We investigate the one-dimensional motion of a traveling wave in a fluctuating medium. Two cases are studied; namely, fluctuating barriers with memory and continuously fluctuating medium. We have shown that as a result of the combination of noise and the spreading dynamics associated with traveling wave propagation, a signal propagates faster, even for values of coupling greater than the critical value associated with the propagation failure phenomena.
DETECTING NONLINEARITIES IN STATIONARY TIME SERIES
Authors: TAKENS FLORIS
Published: November 2004

In this review we survey methods for detecting nonlinearities in stationary time series. These methods are based on the estimation of so-called correlation integrals. These correlation integrals provide a way of analyzing time series and reveal aspects which are often complementary to the information one obtains from power spectra and autocorrelations. So we also focus our attention on the meaning and the estimation of the correlation integrals.
DYNAMICS OF A SINGLE MODEL NEURON
Authors: PASEMANN FRANK
Published: November 2004

The parametrized dynamics of a standard nonlinear model neuron with self-interaction is discussed. For units with a self-excitatory connection a hysteresis effect is observed, and the underlying mechanism is identified as that of a cusp catastrophe. This is true for discrete as well as for continuous dynamics. For the discrete dynamics of self-inhibiting units there appear period-doubling bifurcations from stationary states to stable period-2 orbits.
A STUDY OF BIFURCATIONS IN A CIRCULAR REAL CELLULAR AUTOMATON
Authors: WEITKÄMPER JÜRGEN
Published: November 2004

Real cellular automata (RCA) are time-discrete dynamical systems on ℝN. Like cellular automata they can be obtained from discretizing partial differential equations. Due to their structure RCA are ideally suited to implementation on parallel computers with a large number of processors. In a way similar to the Hénon mapping, the system we consider here embeds the logistic mapping in a system on ℝN, N>1. But in contrast to the Hénon system an RCA in general is not invertible. We present some results about the bifurcation structure of such systems, mostly restricting ourselves, due to the complexity of the problem, to the two-dimensional case. Among others we observe cascades of cusp bifurcations forming generalized crossroad areas and crossroad areas with the flip curves replaced by Hopf bifurcation curves.
UNIMODAL INTERVAL MAPS OBTAINED FROM THE MODIFIED CHUA EQUATIONS
Authors: MISIUREWICZ MICHAŁ
Published: November 2004

Following Brown [1992, 1993] we study maps of the real line into itself obtained from the modified Chua equations. We fix our attention on a one-parameter family of such maps, which seems to be typical. For a large range of parameters, invariant intervals exist. In such an invariant interval, the map is piecewise continuous, with most of pieces of continuity mapped in a monotone way onto the whole interval. However, on the central piece there is a critical point. This allows us to find sometimes a smaller invariant interval on which the map is unimodal. In such a way, we get one-parameter families of smooth unimodal maps, very similar to the well-known family of logistic maps x ↦ ax(1−x). We study more closely one of those and show that these maps have negative Schwarzian derivative. This implies the existence of at most one attracting periodic orbit. Moreover, there is a set of parameters of positive measure for which chaos occurs.
THE THEORY OF CONFINORS IN CHUA’S CIRCUIT: ACCURATE ANALYSIS OF BIFURCATIONS AND ATTRACTORS
Authors: LOZI RENÉ , USHIKI SHIGEHIRO
Published: November 2004

We apply the new concept of confinors and anti-confinors, initially defined for ordinary differential equations constrained on a cusp manifold, to the equations governing the circuit dynamics of Chua’s circuit. We especially emphasize some properties of the confinors of Chua’s equation with respect to the patterns in the time waveforms. Some of these properties lead to a very accurate numerical method for the computation of the half-Poincaré maps which reveal the precise structures of Chua’s strange attractors and the exact bifurcation diagrams with the help of a special sequence of change of coordinates.

We also recall how such accurate methods allow the reliable numerical observation of the coexistence of three distinct chaotic attractors for at least one choice of the parameters.

Chua’s equation seemssurprisingly rich in very new behaviors not yet reported even in other dynamical systems. The application of the theory of confinors to Chua’s equation and the use of sequences of Taylor’s coordinates could give new perspectives to the study of dynamical systems by uncovering very unusual behaviors not yet reported in the literature. The main paradox here is that the theory of confinors, which could appear as a theory of rough analysis of the phase portrait of Chua’s equation, leads instead to a very accurate analysis of this phase portrait.