bluuebunny/crossref_metadata_2025 huggingface dataset:
PURELY NOISE-INDUCED PHASE TRANSITION IN THE MODEL OF GENE SELECTION WITH COLORED NOISE TERM
Authors: SOLDATOV A. V.
Published: November 2004

Gene selection model with colored noise term is investigated by means of a new version of approximate effective Markovian equation proposed earlier. The steady-state probability density is derived for the whole range of model and noise parameters. It is proved that at least for the so-called symmetric case, the increase of the colored noise correlation time τc while the noise intensity D being fixed leads to the same noise-induced transition as the increase of the noise intensity for the white noise case.
UNRENORMALIZED AND RENORMALIZED DISCRETE-SPECTRUM LAMB-SHIFT CONTRIBUTIONS FOR 1S AND 2S HYROGENIC STATES
Authors: SEKE JOSIP
Published: November 2004

A general formula due to Moses (Phys. Rev. A8, 1710 (1973)) for exact transition matrix elements in nonrelativistic hydrogenic atoms has been reduced by carrying out additional calculations. By using the obtained result, unrenormalized (finite) and renormalized Lamb-shift contributions stemming from individual discrete states as well as from the whole discrete spectrum are calculated.
SURFACE-INDUCED DIPOLE MOMENTS OF GALLIUM, INDIUM, AND TIN ON MOLYBDENUM SURFACE
Authors: SAADAT A. R.
Published: November 2004

Liquid gallium (Ga), indium (In), and tin (Sn) were deposited on a molybdenum (Mo) surface. The surface-induced dipole moments of adsorbed adatoms Ga, In, and Sn on Mo were determined experimentally using field-ion and field-emission microscopy. The procedure of the experiment consisted of measuring the change in work function of Mo due to the adsorbed adatoms. The coverage of adatoms was obtained directly from a field-ion image of the surface using a field-ion microscope. The work function changes were obtained by measuring the field-emission currents and plotting the Fowler–Nordhiem curves.

The results of this experiment for the induced dipole moments of Ga, In, and Sn adatoms were found to be 2.35 (D) for Ga, 2.39 (D) for In, and 2.25 (D) for Sn. These values are in good agreement with calculations using the charge transfer theory of chemisorption.
IDENTIFICATION OF MAGNETIC REVERSIBILITY IN Cu–NbIN SITU COMPOSITES
Authors: XIAO Y. G. , LI J. W. , YIN B. , ZHAO Z. X. , FINNEMORE D. K. , VERHOEVEN J. D.
Published: November 2004

Irreversibility temperatures in Cu–Nb in situ formed composites have been investigated by dc magnetization measurements. An extended region of magnetic reversibility is identified. The observed irreversibility line is shown to follow the theoretical prediction of vortex-lattice melting with a reasonable Lindemann parameter.
THERMOELECTRIC EFFECTS IN Bi–Pb–Sr–Ca–Cu–O SUPERCONDUCTOR
Authors: NAQVI S. M. M. R. , DABIR S. , RIZVI H. , FATIMA SHABIH , RAZA S. MOHSIN
Published: November 2004

We have prepared the bulk samples of 2223 Bi–Pb–Sr–Ca–Cu–O superconductor with a T c of 106 K. Temperature dependence of electrical resistivity and thermoelectric power (TEP) measurements were performed on the samples. The behaviour of thermoelectric power near and above the transition temperature can be described on the basis of thermodynamic fluctuations of superconducting order parameter.
THEORETICAL MODEL FOR THE HIGH-FREQUENCY DYNAMICAL SUSCEPTIBILITY IN THE IMPROPER SEGNETOELECTRICS
Authors: RUSTAMOV K. A. , GADJIEV B. R.
Published: November 2004

Description of the temperature and frequency dependences of the dynamical susceptibility in improper segnetoelectrics in the incommensurate phase near the incommensurate–commensurate phase transition is presented. The used model is based on the theory of three interacting nonlinear oscillators.
THEORY OF GIANT MAGNETORESISTANCE IN NONMULTILAYER MAGNETIC SYSTEMS
Authors: SHENG L. , XING D. Y.
Published: November 2004

We present a simple theoretical description of recently measured giant magnetoresistance (GMR) effect in granular ferromagnetic systems. We propose that single-domain ferromagnetic particles embedded in a metallic medium form a series of randomly distributed and spin-dependent potential barriers and wells. This spin-dependent scattering is considered as the main origin of the GMR effect. Good agreement with experiment is found for phase-separated Co x Cu 1−x samples.
THE EFFECT OF 3dn IMPURITIES IN THE YBa2Cu3O7−δ SUPERCONDUCTOR
Authors: LIMA G. A. R. , TORRES VITOR , FAZZIO A.
Published: November 2004

The electronic structure of the CuO chain and the CuO 2 plane in the superconductor YBa 2 Cu 3 O 7−δ doped with 3dn transition-metal (TM) atoms are investigated. The calculations were performed through the semiempirical INDO/S technique, where the correlation effects are taken into account by the Configuration Interaction (CI) procedure. We also calculated, for all 3dn impurities, the Hubbard parameters Udd corresponding to a narrow band. The results obtained demonstrate clear chemical trends in the electronic structure of the 3d's, from Ti to Ni, when they substitute Cu(1) and Cu(2) sites; the hybridization decreases when the atomic number Z decreases. Our work provides a picture which is important to understand the change in T c when the host is doped with TM atom.
PROJECTED DYNAMICS AND NOISE-INDUCED TRANSITIONS IN CHEMICALLY REACTING SYSTEMS
Authors: WU XIAO-GUANG
Published: November 2004

Our studies on noise-induced transitions and projected dynamics in bistable chemical reactions are reviewed. We show that the noise-induced barrier crossing rates are determined by the time-dependent rate kernels that evolve according to projected dynamics. The rate kernels behave differently for projected and ordinary dynamics when barrier-crossing processes are fast. The validity of a phenomenological rate law description is discussed and rate coefficients for some chemically reacting systems are computed.
RECENT PROGRESS ON HIGH-ORDER HARMONIC GENERATION USING LASER-PRODUCED IONS
Authors: MIDORIKAWA KATSUMI , KUBODERA SHOICHI , TASHIRO HIDEO , TOYODA KOICHI
Published: November 2004

The recent progress of the high-order harmonic generation in laser-produced ions is presented. The experimental results obtained at RIKEN using a 500-fs KrF laser (248 nm) are summarized. Rare gas-like ions produced much higher-order harmonics than rare gases did when the laser intensity was increased to 1017 W/cm 2. In addition to rare gas-like ions, various metal ions were used as nonlinear media. The maximum harmonic orders are found to be simply proportional to the ionization potentials of the nonlinear media, including neutral rare gases. The maximum harmonic order observed was the 21st (11.8 nm) in Pb 2+. The advantages of using ions in laser-produced plasmas as nonlinear media for the high-order harmonic generation are discussed.
MICROSCOPIC ORIGIN OF THE DX CENTER IN GaAs AND AlxGa1−xAs
Authors: SAITO MINEO , OSHIYAMA ATSUSHI
Published: November 2004

The DX center in n-type Al x Ga 1−x As has been studied over the past two decades because of technological importance and physical interest. We review from the theoretical side the development of studies on the microscopic origin of the DX center. Recent studies based on the state-of-the-art technique calculations especially focus on the neutral onsite and negatively charged broken-bond models among many models proposed so far. It has not been confirmed from total energy calculations which model is energetically stable. Many theoretical efforts, however, reveal that the broken-bond model reproduces a variety of experimental results for the DX center and is hence the best candidate.
MINIMAL ANOMALOUS OCCUPANCY IN HIGH-Tc SUPERCONDUCTIVITY
Authors: MÉNDEZ-MORENO R.M. , MORENO M. , OROZCO S. , ORTÍZ M.A.
Published: November 2004

A study of a minimal anomalous occupancy is carried out when a small gap occurs near the Fermi surface. A limit which tends softly to the normal occupancy can be introduced. This framework is applied to a quasi-bidimensional fermion gas which can mimick the copper oxide planes in cuprate superconductors. The energy scale implied by this minimally anomalous occupancy (the soft normal limit) for high-T c cuprate superconductors is of the order of the Debye energy. Yet this anomalous occupancy framework overcomes the phonon barrier and a good description for the critical temperature of a representative set of high-T c copper oxide superconductors is obtained.
VOLUME DEPENDENCE OF VANADIUM MAGNETISM
Authors: ELZAIN M.E.
Published: November 2004

The first principle discrete variational method in the spin polarized local density approximation is used to calculate the local properties of 15 atom clusters representing variable crystal size bcc vanadium. Four distinct magnetic configurations are recognized as the lattice constant varies from 5.4 to 8.4 (a.u). At the lowest end, the clusters are paramagnetic (PM) whereas at the upper end, clusters are ferromagnetic (FM). In between, antiferromagnetic couplings prevail. The local magnetic moment increases, in a fashion not unlike second order transitions, from zero in the PM range to nonzero in the AFM region. Transitions between other phases are first order. The systematics of these transitions are ascribed to the general shape of the density of states. The contact magnetic hyperfine field, charge density, and 3d partial occupations at the central sites are also calculated.
QUANTUM ELECTROMAGNETIC FIELD PROPAGATION IN ONE-DIMENSIONAL INHOMOGENEOUS DIELECTRICS WITH DISPERSION
Authors: KIREEV A.N. , DUPERTUIS M.A.
Published: November 2004

An exactly solvable scalar microscopic model describing a radiation field and its interaction to a matter degrees of freedom in one-dimensional inhomogeneous dielectric with dispersion is proposed. A consistent canonical quantization scheme for the model is developed. Two modes of quantum collective excitations of polariton type are found in the general case. The case of an interface between two semi-infinite media is considered explicitly.
ON LOGARITHMIC CORRECTIONS IN TWO-DIMENSIONAL PERCOLATION
Authors: MARSILI M. , JUG G.
Published: November 2004

The possibility of unusual leading logarithmic corrections to the asymptotic behavior of the percolation connectedness length ξ in two dimensions is explored through a finite-size transfer-matrix analysis on strips of widths L≤12. It is found that, for both square-site and triangular-site percolation problems, no such corrections arise and the accepted exact value of the critical exponent ν is recovered.
DYNAMIC PROPERTIES OF SEQUENTIAL TUNNELING THROUGH DOUBLE-BARRIER SYSTEMS
Authors: CHEN L.Y.
Published: November 2004

In this paper, we present an analytical stochastical approach to the dynamic properties of sequential tunneling through double-barrier systems. The effect of charge accumulation is included in the investigation of dynamic conductance and noise current power density at finite frequency. Albeit in the sequential tunneling limit the quantum phase coherence of electron waves is destroyed by inelastic scattering while traversing the junction, the occupation of resonance states by fermionic particles sojourning in the well along with the charge accumulation within and around the structure still give rise to strong correlation among tunneling events. This correlation determines the characteristic frequency of the system and leads to significant suppression of shot noise. The low frequency noise current power density compares agreeably with experimental measurements.
COLORED POLYMERS
Authors: PESANDO IGOR
Published: November 2004

We show that non-oriented colored polymers (self-avoiding walks with different types of links) are in the same universality class of the ordinary self-avoiding walks, while the oriented colored are not.
ORIENTATIONAL GLASS TRANSITION AND STRUCTURAL RELAXATION IN SOLID C60
Authors: MEINGAST CHRISTOPH , GUGENBERGER FRANK
Published: November 2004

We review recent experiments and models dealing with glass transition and the associated structural relaxation in solid C 60. This glass transition is thought to result from the freezing-in of thermally-induced dynamic orientational disorder in an otherwise orientationally-ordered crystalline structure. The structural relaxation is shown to be approximately exponential and linear (in the relaxation nomenclature), and the relaxation time nearly follows an Arrhenius temperature dependence over some 15 decades. C 60 is thus an example of an extremely ‘strong’ glass former in the ‘strong-fragile’ classification. The relaxation data are consistent with the simple structural model derived from X-ray and neutron diffraction, in which each C 60 molecule can be in two different, but energetically nearly equivalent (Δ≈10 meV ) orientational states, which are separated by an energy barrier of Ea≈250 meV . Small deviations from this simple picture are attributed to a slight temperature dependence of both Δ and Ea due to a changing local environment.
THOULESS NUMBER AND SPIN DIFFUSION IN QUANTUM HEISENBERG FERROMAGNETS
Authors: KOPIETZ PETER
Published: November 2004

Using an analogy between the conductivity tensor of electronic systems and the spin stiffness tensor of spin systems, we introduce the concept of the Thouless number g0 and the dimensionless frequency-dependent conductance g(ω) for quantum spin models. It is shown that spin diffusion implies the vanishing of the Drude peak of g(ω), and that the spin diffusion coefficient Ds is proportional to g0. We develop a new method based the Thouless number to calculate D s , and present results for D s in the nearest-neighbor quantum Heisenberg ferromagnet at infinite temperatures for arbitrary dimension d and spin S.
MEAN-FIELD STUDIES OF 2D HUBBARD HAMILTONIANS COUPLED VIA INTERLAYER PAIR TUNNELING
Authors: ZECCHINA R.
Published: November 2004

In the framework of two different mean-field theories characterized by pairing and magnetic in-plane order parameters, we study the thermodynamics of a model defined by 2D Hubbard Hamiltonians coupled via a pair-hopping term. The interplay between the pair-hopping amplitude and the effective on-site interaction U is thoroughly discussed.
Pb-DOPING EFFECTS IN Hg1−xPbxBa2Ca2Cu3O8+δ
Authors: XUE Y.Y. , HUANG Z.J. , QIU X.D. , BEAUVAIS L. , ZHANG X.N. , SUN Y.Y. , MENG R. , CHU C.W.
Published: November 2004

Samples with a nominal composition of Hg 1−x Pb x Ba 2 Ca 2 Cu 3 O 8+δ (x~0.1, 0.2, and 0.3) have been synthesized and characterized. The Pb-doping promotes the formation of the three CuO2-layer compound Hg 1−x Pb x Ba 2 Ca 2 Cu 3 O 8+δ, and reduces the release of Hg vapor at the synthesis temperature. The intergrain electric coupling is also significantly enhanced by the doping, resulting in lower normal-state resistivity and higher intergrain critical current density. The carrier concentration of the as-synthesized samples increases with the increase of x, ranging from underdoped (x~0) to overdoped (x≥0.2).
ZERO AND FINITE TEMPERATURE STUDY OF SINGLE FULLERENE CAGES AND CARBON “ONIONS” — GEOMETRY AND SHAPE
Authors: MAITI A. , BRABEC C.J. , BERNHOLC J.
Published: November 2004

Scaling arguments are used to show that above a critical size of several thousand atoms, there is a stability crossover from single to multilayer cages. Conjugate gradient minimization using a classical three-body interatomic potential, as well as tight-binding electronic structure calculations yield ground-state configurations for large fullerene shells that are polyhedral with clearly faceted geometry. The structure, energetics and configurational entropy associated with low-energy defects are calculated and the number of defects estimated as a function of temperature. The role of these thermally generated defects on the shape of large fullerenes is investigated in order to explain the nearly spherical shapes of the newly discovered carbon “onions”.
A PHYSICAL PICTURE OF PROXIMITY EFFECT BETWEEN SUPERCONDUCTOR AND MAGNETIC MANGANESE OXIDE
Authors: KASAI MASAHIRO , OHONO TOSHIYUKI , KOZONO YUZOO
Published: November 2004

We have investigated the proximity effect between superconductor and magnetic manganese oxide La 1−x Ca x MnO z (LCMO) or La 1−x Sr x MnO z (LSMO). Experimental studies revealed that supercurrents pass through the magnetic material only in the region where the magnetic state transits from ferromagnetism to antiferromagnetism, where spin fluctuation is large. The anisotropy of the junction characteristics suggested that spin dynamics plays an important role in the novel kind of proximity effect. In this letter, experimental results are reviewed and a physical picture coupled to spin fluctuation is proposed.
DENSITY FUNCTIONAL THEORY AND STATISTICAL GAUGE FIELDS
Authors: GELLER MICHAEL R.
Published: November 2004

We consider the possibility that the exchange-correlation vector potential of density functional theory and the Chern-Simons gauge potential, used to change the statistics of particles in two dimensions, are related. By comparing the corresponding gauge invariant field strengths and their dependence on density and external magnetic field, we find no connection between these two potentials, in contrast to a recent proposal.
QUANTUM STOCHASTIC LIOUVILLE EQUATION OF ITO TYPE
Authors: SAITO T. , ARIMITSU T.
Published: November 2004

The quantum stochastic Liouville equation of Ito type is derived, for the first time, within Nonequilibrium Thermo Field Dynamics (NETFD), a unified canonical formalism for dissipative and/or stochastic fields. With the stochastic time-evolution generator of Ito type, the whole framework is inspected. Since most of the mathematical formulations of noncommutative stochastic variables are based on the equations of Ito type, the construction of the quantum stochastic Liouville equation has been highly desired. It is expected that the unified framework may provide us with a deeper insight for the mathematical foundation of quantum stochastic variables as well as for the physical one.
OFFLINE HANDWRITING RECOGNITION USING SYNTHETIC TRAINING DATA PRODUCED BY MEANS OF A GEOMETRICAL DISTORTION MODEL
Authors: VARGA T. , BUNKE H.
Published: November 2004

A perturbation model for the generation of synthetic textlines from existing cursively handwritten lines of text produced by human writers is presented. The goal of synthetic textline generation is to improve the performance of an offline cursive handwriting recognition system by providing it with additional training data. It can be expected that by adding synthetic training data the variability of the training set improves, which leads to a higher recognition rate. On the other hand, synthetic training data may bias a recognizer towards unnatural handwriting styles, which could lead to a deterioration of the recognition rate. In this paper the proposed perturbation model is evaluated under several experimental conditions, and it is shown that significant improvement of the recognition performance is possible even when the original training set is large and the textlines are provided by a large number of different writers.
MOUSE AND DISPLAY TABLETS AS CURSOR CONTROL DEVICES
Authors: STEVENSON ROGER , PHILLIPS JAMES G. , TRIGGS TOM J.
Published: November 2004

Given the proliferation of touch-sensitive screen technologies, the factors contributing to efficiency of cursor control device were examined to better inform choice and design of Graphical User Interfaces. Fitts' law can be used to describe the relative efficiency of these cursor control devices. Experiment One required 18 participants to move a cursor between targets depicted upon a WACOM PL400 display graphics tablet, over various amplitudes, using a computer mouse or stylus, examining the speed and accuracy of cursor placement. The touch sensitive screen allowed faster acquisition of targets than the mouse. Since the mouse has a higher control/display ratio (gain) than the touch sensitive screen, Experiment Two addressed manipulation of the gain settings on computer mouse performance. Low gain offered some accuracy benefits. Possible posture problems associated with the touch sensitive screen were explored in Experiment Three. Screen orientation had little effect upon cursor positioning performance, suggesting the benefits of the touch sensitive screen can be transferred to user-friendly postures.
AN OVERVIEW OF THE PHILIPS RESEARCH SYSTEM FOR LARGE VOCABULARY CONTINUOUS SPEECH RECOGNITION
Authors: NEY H. , STEINBISS V. , HAEB-UMBACH R. , TRAN B.-H. , ESSEN U.
Published: November 2004

This paper gives an overview of a research system for phoneme based, large vocabulary continuous speech recognition. The system to be described has been applied to the SPICOS task, the DARPA RM task and a 12000 word dictation task. Experimental results for these three tasks will be presented. Like many other systems, the recognition architecture is based on an integrated statistical approach. In this paper, we describe the characteristic features of the system as opposed to other systems: (1) The Viterbi criterion is consistently applied both in training and testing. (2) Continuous mixture densities are used without any tying or smoothing; this approach can be viewed as a sort of ‘statistical template matching’. (3) Time-synchronous beam search is used consistently throughout all tasks; extensions using a tree organization of the vocabulary and phoneme lookahead are presented so that a 12000 word task can be handled.
DICTATION MACHINE BASED ON JAPANESE CHARACTER SOURCE MODELING
Authors: SHIKANO KIYOHIRO , YAMADA TOMOKAZU , KAWABATA TAKESHI , MATSUNAGA SHOICHI , FURUI SADAOKI , HANAZAWA TOSHIYUKI
Published: November 2004

This paper describes a phonetic typewriter and a dictation machine that utilize the underlying statistical structure of phoneme or character sequences. The approach of using syllable or character trigrams is applied to language source modeling. The language source models are obtained by calculating trigram probabilities from a large text database. These models are combined with the HMM-LR continuous speech recognition system.3,6 The phonetic typewriter is tested using 274 phrases uttered by one male speaker. The syllable source model achieves a 94.9% phoneme recognition rate with the test-set phoneme perplexity of 3.9. Without the syllable source model, the phoneme recognition rate is only 73.2%. A trigram model based on characters is also evaluated. This character source model can reduce the syllable perplexity significantly to 7.7, compared with 10.5 of the syllable source model. The character source model achieves a 78.5% character transcription rate for the 274 phrase utterances. The experimental results show that a syllable source model and a character source model are very effective for realizing a Japanese dictation machine.
RECOGNITION OF MANDARIN SYLLABLES BASED ON THE DISTRIBUTION OF TWO-DIMENSIONAL CEPSTRAL COEFFICIENTS
Authors: WANG HSIAO-CHUAN , PAI HSIAO-FEN
Published: November 2004

This paper presents a speech recognition method based on the distribution of two-dimensional cepstral (TDC) coefficients. For each recognition unit, a TDC matrix is calculated. A set of selected TDC coefficients forms a pattern to represent this speech segment. By assuming the Gaussian distribution of the TDC coefficients, a statistical model for a class of speech patterns is generated. The recognition process is to evaluate the probability of a TDC pattern belonging to a specific pattern class and to find the model which gives the highest probability. This method is applied to the recognition of Mandarin syllables. The experimental result shows that the proposed method is very promising for syllabic languages such as Mandarin.
PATH-CONTROLLED GRAPH GRAMMARS FOR SYNTACTIC PATTERN RECOGNITION
Authors: AIZAWA KUNIO , NAKAMURA AKIRA
Published: November 2004

The graph structure is a strong formalism for representing pictures in syntactic pattern recognition. Many models for graph grammars have been proposed as a kind of hyper-dimensional generating systems, whereas the use of such grammars for pattern recognition is relatively infrequent. One of the reasons is the difficulty of building a syntax analyzer for such graph grammars. In this paper, we define a subclass of nPCE graph grammars and present a parsing algorithm of O(n) for both sequential and parallel cases.
SHAPE RECOVERY AND ERROR CORRECTION BASED ON HYPOTHETICAL CONSTRAINTS BY PARALLEL NETWORK FOR ENERGY MINIMIZATION
Authors: KAKUSHO KOH , DAN SEIICHIRO , ABE NORIHIRO , KITAHASHI TADAHIRO
Published: November 2004

Three-dimensional (3D) shape recovery from a monocular image is the inverse process of optical projection and necessitates the use of additional constraints on 3D features of the objects. We have proposed the method of shape recovery based on some hypothetical constraints and its realization by energy minimization using a parallel network. In this paper, we will discuss an extension of our proposal with the aim of correcting noise and errors in an input image through the process of shape recovery. It is hardly possible to extract edges and vertexes free from noise and errors from a real image. For the robustness of the system, we must provide our system with the ability to correct such noise and errors. In this extension, we can also modulate the inclination of the process toward model-driven or data-driven.
LEARNING EQUAL MATRIX GRAMMARS BASED ON CONTROL SETS
Authors: TAKADA YUJI
Published: November 2004

An equal matrix grammar is a parallel rewriting system. In this paper, we consider the problem of learning equal matrix grammars from examples. We introduce a learning method based on control sets and show two subclasses learnable in polynomial time with learning methods for regular sets. We also show that for any equal matrix language there exists an equal matrix grammar learnable efficiently from positive structural examples only.
LEARNING OF RECOGNIZABLE PICTURE LANGUAGES
Authors: SIROMONEY RANI , MATHEW LISA , SUBRAMANIAN K.G. , DARE V.R.
Published: November 2004

Learning of certain classes of two-dimensional picture languages is considered in this paper. Linear time algorithms that learn in the limit, from positive data the classes of local picture languages and locally testable picture languages are presented. A crucial step for obtaining the learning algorithm for local picture languages is an explicit construction of a two-dimensional on-line tessellation acceptor for a given local picture language. A polynomial time algorithm that learns the class of recognizable picture languages from positive data and restricted subset queries, is presented in contrast to the fact that this class is not learnable in the limit from positive data alone.
OFF-LINE VERIFICATION OF JAPANESE SIGNATURES AFTER ELIMINATION OF BACKGROUND PATTERNS
Authors: YOSHIMURA ISAO , YOSHIMURA MITSU
Published: November 2004

A system of off-line signature verification composed of a preprocessing stage and a verification stage is proposed in this paper. It is assumed that each signature is written on a surface with a background pattern and a sample of the background pattern is available. The preprocessing stage to eliminate the background pattern from a signature image consists of 5 steps: the position adjustment between a signature image and a background image, the filtering of the background pattern by local maximization, the clipping of random noises from the background pattern, the background elimination by transformation of the multilevel signature image to a binary signature image through subtraction and thresholding, and the smoothing for defects recovery and isolated noise elimination. The effect of the preprocessing operation is illustrated in figures. The verification stage following the preprocessing stage is based on the Arc Pattern Method proposed in Ref. 7. An experiment is performed to examine the performance of the proposed system. Twenty Japanese autographs, for which 20 authentic signatures, 10 genuine counter signatures and 10 forged counter signatures are provided, are used in the experiment. The experiment achieved an error rate of as low as approximately 14%.
VLSI ARCHITECTURES FOR PATTERN MATCHING
Authors: RANGANATHAN N. , SASTRY RAGHU
Published: November 2004

The recognition of patterns is an important task in robot and computer vision. The patterns themselves could be one- or two-dimensional, depending upon the application. Pattern matching is a computationally intensive and time consuming operation. The design of special purpose hardware could speed up the matching task considerably, making real-time responses possible. Advances in parallel processing and VLSI technologies have made it possible to implement inexpensive, efficient and very fast custom designs. Many approaches and solutions have been proposed in the literature for hardware implementations of pattern matching techniques. In this paper, we present a detailed overview of some of the important contributions in the area of hardware algorithms and architectures for pattern matching.
A TWO-PARAMETER GENERATE-AND-TEST METHOD FOR CAMERA PARAMETER ESTIMATION WITH ANY PLANAR CALIBRATION OBJECT
Authors: CHEN ZEN , WANG CHAO-MING
Published: November 2004

In this paper we address the camera parameter estimation problem using an arbitrary planar calibration object. We intend not to use a system of linear or nonlinear equations in terms of the camera parameters derived from the correspondence relationships between the image features (points or lines) and the object features. Instead, we assume that the shape of the planar object can be arbitrary. Therefore, there may not exist any extractable object point or line features. We formulate the estimation method as a generate-and-test method. To make the method effective, we reduce the dimensionality of the parameter space from six to two using a simplified model of the perspective transformation under some mild conditions. Furthermore, several other measures are also taken to cut down the generation time and the verification time. Real, computer-generated, and noisy imagery data are used to illustrate our method in the experiments. The statistics on the speed performance of the method are also included.
A MODEL-BASED SPLIT-AND-MERGE METHOD FOR CHARACTER STRING RECOGNITION
Authors: NISHIDA HIROBUMI , MORI SHUNJI
Published: November 2004

Recognition of handwritten character strings is a challenging problem, because we need to cope with variations of shapes and touching/breaking of characters at the same time. A natural approach to recognizing such complex objects is as follows: The object is decomposed into segments, and meaningful partial shapes (shapes which are recognized as some characters) are constructed by merging segments locally. Then, a globally consistent interpretation of the object is determined from the combination of partial shapes. This approach can be referred to as a model-based split-and-merge method. Based on this idea, we present an algorithm for recognition and segmentation of character strings. We give systematic performance statistics by experiments using handwritten numerals. This algorithm can be applied to character strings composed of any number of characters and any type of touching or breaking, whether the number of constituent characters is known or unknown.
BEHAVIOR-BASED ACTIVE VISION
Authors: PINHANEZ CLAUDIO S.
Published: November 2004

A vision system was built using a behavior-based model, the subsumption architecture. The so-called active eye moves the camera’s axis through the environment, detecting areas with high concentration of edges, with the help of a kind of saccadic movement. The design and implementation process is detailed in the article, paying particular attention to the fovea-like sensor structure which enables the active eye to efficiently use local information to control its movements. Numerical measures for the eye’s behavior were developed, and applied to evaluate the incremental building process and the effects of the saccadic movements on the whole system. A higher level behavior was also implemented, with the purpose of detecting long straight edges in the image, producing pictures similar to hand drawings. Robustness and efficiency problems are addressed at the end of the paper. The results seem to prove that interesting behaviors can be achieved using simple vision methods and algorithms, if their results are properly interconnected and timed.
A SIMPLE DISCRIMINATOR FOR IDENTIFYING FAULTS IN HIGHLY STRUCTURED DIAGNOSABLE SYSTEMS
Authors: KOHDA TOHRU
Published: November 2004

It is known that there exist several classes of systems for which faults can be efficiently diagnosed. All of the faulty units in most of these classes, however, must be permanently faulty. In this paper, a special class of optimally t/r/τ-diagnosable systems is defined which are composed of subsystems, each of which has a kernel unit v. A simple discriminator is given for identifying the state of each kernel unit v as a function of the numbers of six test outcome patterns observed in the subsystems. Our class is a generalized version of Mallela’s independent diagnosable systems. The diagnosis quality of the discriminator is as follows: whenever a given syndrome is hf(τ)-compatible from a t/r-fault situation, then (1) if the discriminator identifies a unit as being faulty, it is always correct; and (2) the discriminator identifies at least all of the permanently faulty units.
COMBINING THE FOLDING AND TESTING FOR PROGRAMMABLE LOGIC ARRAYS
Authors: WEI KAI-CHENG , LIU BIN-DA
Published: November 2004

Different from the previous techniques which treated the folding and testing for PLAs as separate problems, this paper presents a new approach to combine the bipartite folding and testing for PLA’s in the same procedure. Fewer silicon area than other existing comparable techniques is required to make the PLA testable. Experimental results show that this technique can reduce chip area, test length, test storage and time complexity.
ON THE GLOBAL BEHAVIOR OF SELF-OSCILLATORY SYSTEMS
Authors: MOROZOV A.D.
Published: November 2004

The problem of the global behavior of the system with 3/2 degrees of freedom is considered in this paper. The results of the theoretical investigation of the case when the systems approach a nonlinear Hamiltonian system are presented. Using, for example, the Duffing-van der Pol equation, computer analysis gives good agreement with theory when the external force has moderate amplitude values (“miracle of a small parameter”). The bifurcations of the invariant torus and resonances are analyzed as a function of the system parameters.
A TUTORIAL GLOSSARY OF GEOMETRICAL DYNAMICS
Authors: THOMPSON J.M.T. , STEWART H.B.
Published: November 2004

We present here an informal, encyclopedic glossary of terms and formulae covering the new geometrical concepts of nonlinear dynamics and chaos. It is arranged as an alphabetical dictionary, which can also be read as a connected introduction to the subject by following the go to instructions starting with the entry dynamical system and ending with archetypal equations.
CONVERGENCE OF JULIA SETS IN THE APPROXIMATION OF λez BY λ[1+(z/d)]d
Authors: KRAUSKOPF BERND
Published: November 2004

The polynomials Pd,λ(z)≔λ[1+(z/d)]dconverge uniformly on compact sets to Eλ(z)≔λez. What this convergence means for the dynamics of these functions when iterated was first studied in Devaney et al. [preprint]. Here we show the convergence of the corresponding Julia sets in the Hausdorff metric for two cases: (1) for λ such that Eλ has an attracting periodic orbit, in which case its Julia set is a Cantor set of curves, and (2) for λ such that the Julia set of Eλ is the whole plane [Formula: see text]. Finally, we give the key ideas of the algorithms designed to illustrate this convergence.
BISPECTRAL AND TRISPECTRAL CHARACTERIZATION OF TRANSITION TO CHAOS IN THE DUFFING OSCILLATOR
Authors: CHANDRAN VINOD , ELGAR STEVE , PEZESHKI CHARLES
Published: November 2004

Higher-order spectral (bispectral and trispectral) analyses of numerical solutions of the Duffing equation with a cubic stiffness are used to isolate the coupling between the triads and quartets, respectively, of nonlinearly interacting Fourier components of the system. The Duffing oscillator follows a period-doubling intermittency catastrophic route to chaos. For period-doubled limit cycles, higher-order spectra indicate that both quadratic and cubic nonlinear interactions are important to the dynamics. However, when the Duffing oscillator becomes chaotic, global behavior of the cubic nonlinearity becomes dominant and quadratic nonlinear interactions are weak, while cubic interactions remain strong. As the nonlinearity of the system is increased, the number of excited Fourier components increases, eventually leading to broad-band power spectra for chaos. The corresponding higher-order spectra indicate that although some individual nonlinear interactions weaken as nonlinearity increases, the number of nonlinearly interacting Fourier modes increases. Trispectra indicate that the cubic interactions gradually evolve from encompassing a few quartets of Fourier components for period-1 motion to encompassing many quartets for chaos. For chaos, all the components within the energetic part of the power spectrum are cubically (but not quadratically) coupled to each other.
GLOBAL NONLINEAR NOISE REDUCTION USING RADIAL BASIS FUNCTIONS
Authors: HOLZFUSS JOACHIM , KADTKE JAMES
Published: November 2004

A global nonlinear technique for noise reduction is described which is able to separate a noise source from a periodic or chaotic signal. The method is based on interpolation of the global flow of nonlinear dynamical systems with radial basis functions. Preliminary results indicate it provides a considerable increase of the signal-to-noise ratio. The algorithm is described in detail and numerical examples are given.
ANOTHER LOOK AT EVIDENCE ON THE DISTRIBUTION OF CERTAIN SPECULATIVE PRICES
Authors: JADITZ TED , JOHNSON DAVID , McCLELLAND ROBERT
Published: November 2004

Benoit Mandelbrot suggests that prices of certain commodities follow stable Paretian distribution laws. Our results indicate that ARCH-type models fit some Mandelbrot time series fairly well. In other cases, tests for nonlinear dependence and chaos reject the ARCH specification. However, the patterns of dependence exhibited by these data are generally not consistent with the hypothesis that they are generated by a chaotic dynamic process.
TOPOLOGICAL ANALYSIS OF CHAOTIC SIGNALS FROM A CO2 LASER WITH MODULATED LOSSES
Authors: LEFRANC MARC , GLORIEUX PIERRE
Published: November 2004

Unstable periodic orbits have been extracted from chaotic time series coming from a CO 2 laser with modulated losses. Topological analysis of their organization reveals that chaos in this laser occurs through the formation of a Smale’s horseshoe.
NONLINEAR FORECASTING OF SPIKE TRAINS FROM SENSORY NEURONS
Authors: LONGTIN ANDRÉ
Published: November 2004

The sequence of firing times of a neuron can be viewed as a point process. The problem of spike train analysis is to infer the underlying neural dynamics from this point process when, for example, one does not have access to a state variable such as intracellular voltage. Traditional analyses of spike trains have focussed to a large extent on fitting the parameters of a model stochastic point process to the data, such as the intensity of a homogeneous Poisson point process. This paper shows how methods from nonlinear time series analysis can be used to gain knowledge about correlations between the spiking events recorded from periodically driven sensory neurons. Results on nonlinear forecastability of these spike trains are compared to those on data sets derived from the original data set and satisfying an appropriately chosen null hypothesis. While no predictability, linear or nonlinear, is revealed by our analysis of the raw data using local linear predictors, it appears that there is some predictability in the successive phases (rather than intervals) at which the neurons fire.
CHAOTIC BURSTING IN A CONVECTING FLUID
Authors: METCALFE GUY , BEHRINGER R.P.
Published: November 2004

Mixtures of 3 He in superfluid 4 He provide an interesting and important system for testing theories of convection and for studying nonlinear dynamics. Here we describe experimental observations of chaotic bursting in a convecting layer of 3 He -superfluid-4 He . For aspect ratio Γ=6.0 and Prandtl number Pr=0.3, we find intermittent bursts out of a chaotic state. This state evolved via a series of well-defined transitions involving established routes to chaos. Above the onset of bursting the average length of a burst-free region l varies as a power law: l ∝(R−Rb)−γ with γ=4.6; a power-law dependence of l is expected. An unexpected result is that the average length of a burst varies as (R−Rb)δ with δ=2.0. In addition, a particularly novel state was seen for Γ=4.25 and Pr=0.12, where there occurs a reversible switching transition involving two chaotic attractors.
FREQUENCY DOMAIN APPROACH TO COMPUTATION AND ANALYSIS OF BIFURCATIONS AND LIMIT CYCLES: A TUTORIAL
Authors: MOIOLA JORGE L. , CHEN GUANRONG
Published: November 2004

This paper introduces a frequency domain approach together with some techniques and methodologies for the computation and analysis of bifurcations and limit cycles arising in nonlinear dynamical systems. The frequency domain approach discussed in this paper originates from the classical feedback control systems theory, which has been proven to be successful and efficient for the computation and analysis of regular as well as singular bifurcations and stable as well as unstable limit cycles. While describing these techniques and methods, two representative yet distinct applications of the approach are studied in detail: The graphical analysis of multiple parametric bifurcation curves and the numerical computation of multiple limit cycles. Compared to the classical time domain methods, both the advantages and the limitations of the frequency domain approach are analyzed and discussed. It is believed that this frequency domain approach to the study of nonlinear dynamics has great potential and promising future in both theory and applications.
ONE-DIMENSIONAL CHAOS IN IMPULSED LINEAR OSCILLATING CIRCUITS
Authors: GARDINI LAURA , LUPINI RENZO
Published: November 2004

The dynamics of a damped linear oscillating circuit subject to impulses is represented by a one-dimensional endomorphism (or noninvertible map) π: ℝ → ℝ. The asymptotic behavior of orbits in the phase-plane is characterized in terms of critical points and point singularities of π (fixed points or cycles). Their combined effect, that is, the merging of a critical point into a repelling cycle, causes a global bifurcation or a homoclinic bifurcation, with transition to chaotic oscillations.
TWO-PARAMETER STUDY OF TRANSITION TO CHAOS IN CHUA'S CIRCUIT: RENORMALIZATION GROUP, UNIVERSALITY AND SCALING
Authors: KUZNETSOV A. P. , KUZNETSOV S. P. , SATAEV I. R. , CHUA L. O.
Published: November 2004

A complex fine structure in the topography of regions of different dynamical behavior near the onset of chaos is investigated in a parameter plane of the 1D Chua's map, which describes approximately the dynamics of Chua's circuit. Besides piecewise-smooth Feigenbaum critical lines, the boundary of chaos contains an infinite set of codimension-2 critical points, which may be coded by itineraries on a binary tree. Renormalization group analysis is applied which is a generalization of Feigenbaum's theory for codimension-2 critical points. Multicolor high-resolution maps of the parameter plane show that in regions near critical points having periodic codes, the infinitely intricate topography of the parameter plane reveals a property of self-similarity.
GENERALIZED HOPF, SADDLE-NODE INFINITE PERIOD BIFURCATIONS AND EXCITABILITY DURING THE ELECTRODISSOLUTION AND PASSIVATION OF IRON IN A SULFURIC ACID SOLUTION
Authors: SAZOU DIMITRA , KARANTONIS ANTONIS , PAGITSAS MICHAEL
Published: November 2004

Periodic current oscillations of relaxation type are observed in a certain potential range during iron electrodissolution in sulfuric acid solutions when the iron electrode turns from the active to the passive state and vice versa. The system displays in the current-potential (I-E) plane a hysteresis loop consisting of the stable active and passive steady states and an unstable steady state which corresponds to an intermediate situation between active and passive states. In the present study, the dynamical characteristics of the I-E polarization curve were studied. It was shown that transition from the oscillatory to the active steady state goes via a generalized Hopf bifurcation, whereas transition from the oscillatory to the passive steady state goes via a saddle-node infinite-period (SNIPER) bifurcation. Single pulse and pulse series stimulation of the active and passive steady states proved that both steady states are excitable. The refractory periods and the thresholds of excitability were measured. Further perturbation experiments were carried out at the two steady states away from the bifurcation points, and it was shown that the active steady state is a stable focus and the passive one is a stable node.
CHAOTIC SYNCHRONIZATION OF A ONE-DIMENSIONAL ARRAY OF NONLINEAR ACTIVE SYSTEMS
Authors: PÉREZ-VILLAR V. , MUÑUZURI A. P. , PÉREZ-MUÑUZURI V. , CHUA L. O.
Published: November 2004

Linear stability analysis is used to study the synchronization of N coupled chaotic dynamical systems. It is found that the role of the coupling is always to stabilize the system, and then synchronize it. Computer simulations and experimental results of an array of Chua's circuits are carried out. Arrays of identical and slightly different oscillators are considered. In the first case, the oscillators synchronize and sync-phase, i.e., each one repeats exactly the same behavior as the rest of them. When the oscillators are not identical, they can also synchronize but not in phase with each other. The last situation is shown to form structures in the phase space of the dynamical variables. Due to the inevitable component tolerances (±5%), our experiments have so far confirmed our theoretical predictions only for an array of slightly different oscillators.
NONLINEAR PHENOMENA IN CIRCULAR PARTICLE ACCELERATORS I: SEXTUPOLAR NONLINEARITIES
Authors: DILÃO RUI
Published: November 2004

In this paper we relate the methods of the theory of dynamical systems to problems of accelerator design and optimization. It is written in review article style and any prior knowledge of accelerator physics is not required.

We derive the Poincaré map for the equation of horizontal transverse motion of a test particle in a circular accelerator in the presence of any number of sextupolar nonlinearities. This map is studied within the framework of nonlinear dynamics and we identify several optimization strategies for the design of an accelerator magnet lattice. The dynamic aperture problem is analysed and we obtain, for a beam line with two sextupoles, the dependence of the dynamic aperture on the line parameters. The mechanisms of aperture reduction near rational values of the tune, ν0 = p/q ≠ 1/3, are due to the creation of heteroclinic tangles and do not affect the stability of the design orbit. For a machine with an arbitrary number of localized sextupolar fields, we obtain the dependence of the nonlinear tune on the amplitude of the particles and the parameters of the accelerator. The predictions for the nonlinear tune agree with the numerical simulations within the maximum relative error of 6% at large amplitudes (~ dynamic aperture) and within the relative error range 1%–2% at intermediate amplitudes (~ half dynamic aperture).
ITERATIONS OF THE SAWTOOTH MAP AS A DYNAMICAL MODEL FOR CVD/CVI SiC POLYTYPE GROWTH
Authors: VIGNOLES GÉRARD L.
Published: November 2004

In order to describe silicon carbide polytype growth under CVD/CVI conditions, a dynamical model based on iterations of the sawtooth map has been studied. A two-parameter bifurcation diagram has been computed for a simple logistic-like family, and its structure has been studied in more detail by means of kneading theory and study of the skeleton. All the routes to chaos are shown to derive from the application of a central theorem involved in the construction of the skeleton. A comparison, under a combinatorial point of view, between this mathematical model and the reported data on known SiC polytypes is carried out and discussed. Indeed, the model is able to generate any periodic or chaotic polytypic sequence.