bluuebunny/crossref_metadata_2025 huggingface dataset:
SPINODAL NUCLEATION
Authors: MONETTE L.
Published: November 2004

The aim of this paper is to present the theoretical foundations of spinodal nucleation, by reviewing key theoretical and numerical work. The basic ideas of classical nucleation theory are first presented: the classical droplet model, and the Becker-Döring theory, as these concepts are important to the development of the field theoretical formulation of nucleation. The field theoretical framework for classical nucleation is exposed in some detail, followed by the presentation of a similar framework, extended to nucleation in the proximity of a spinodal (non-classical nucleation), in the presence of long-range Ising interactions. The non-classical nucleating droplet is found to be diffuse, hence to strongly depart from the classical prediction of a compact object with a well-defined surface.

The fact that the non-classical nucleating droplet is identified with a ramified object prompts the development of an appropriate cluster description. The basic principles of percolation theory are outlined, and some lattice percolation models introduced. The Kastaleyn-Fortuin mapping, which establishes a connection between a particular percolation model and a limit of the Potts model, is briefly described. This mapping is crucial to the development of a second mapping (Coniglio-Klein) of the Ising spinodal point into a percolation model, where the long-range Ising interactions are translated into a long-range connectivity in the appropriate percolation model. The final result consists of the most powerful tool available to identify precisely the non-classical nucleating droplet in numerical simulations of nucleation in proximity of a spinodal.

Numerical simulation results are presented, which support the field theoretical formulation of non-classical nucleation. As the numerical results seem to support the fact that the non-classical nucleating droplet is also a percolation cluster, its fractal structure is investigated by considering the mean-field regime of the percolation model, i.e. a percolation model with long-range connectivity. This leads to an apparent contradiction between the field theory and the mean-field percolation model predictions concerning the mass (or density) scaling of the nucleating droplet. This inconsistency is resolved by postulating that the mean-field percolation clusters cannot be non-classical nucleating droplets, and proposing that the non-classical nucleating droplet is in fact the result of a coalescence of many such clusters. Finally, the calculation of the static prefactor in the nucleation rate by assuming a Becker-Döring dynamics for the coalescence mechanism is outlined. The result is found to be consistent with the predictions of the field theory for the static prefactor. Numerical results are also presented in support of the hypothesized coalescence mechanism.
FREE VOLUME RELATED STRUCTURAL CHANGES IN THE EPOXY POLYMER TGDDM
Authors: RAVINDRACHARY V. , RAMANI R. , RANGANATHAIAH C. , GOPAL S.
Published: November 2004

Positron lifetime measurements have been carried out in an amine-cured epoxy polymer TGDDM/DDS/BFE as a function of annealing temperature. The measured spectra are best fitted to three component analysis. From the measured long lifetime component the average size of the free volume holes has been calculated following Nakanishi et al.’s treatment. Variation of lifetime parameters with temperature indicates the preferential trapping of positronium atoms in the regions of increased free volume hole sizes. On the other hand, positrons are being trapped at micro-voids in the ordered regions. The slow increase of free volume upto 170°C may be due to the thermal expansion and we measure 170° C as the Tg for this epoxy. Lifetime data are also used to calculate the trapping rates in the ordered and disordered regions of the epoxy based on Goldanskii’s kinetic relations.
ANOMALOUS ABSORPTION OF SHEAR PLATE MODES BY A THIN LAYER OF VISCOUS FLUID
Authors: GRAMOTNEV D.K. , VYUKOV M.L.
Published: November 2004

The anomalous absorption of shear plate modes by a thin fluid layer enclosed between a plate butt-end and an elastic halfspace, or between butt-ends of two different plates, is analyzed in the frictional contact approximation. General equations describing the anomalous absorption are derived for arbitrarily thick plates. Specific cases of thin plates, as compared to the wavelengths, are given particular attention. Typical fluid layer thicknesses corresponding to the absorptivity maximum which may be as good as unity, are obtained. The case when fluid does not fill the entire space between the butt-ends of plates, or between the plate butt-end and the halfspace, is also considered.
SOME REMARKS ON THE THEORY OF AN ELECTRON ON BINARY QUASIPERIODIC LATTICES
Authors: IGUCHI KAZUMOTO
Published: November 2004

Some remarks on the theory of an electron on binary quasiperiodic lattices are presented herein. We classify all the binary quasiperiodic lattices that are constructed by a class of scaling transformations: B→A, A→AnB, where n is an arbitrary positive integer at each stage of the scaling transformation, into three types by means of the scaling transformation itself. We give a simple approach to generate a Cantor-set type energy spectrum by the generic trace map on an invariant surface, I=x2+y2+z2−2xyz−1. The Cantor-set type energy spectrum is a result of the existence of the noncompact invariant surface of the invariant I>0. The energy bands correspond to the nonescaping points of the generic trace map on the invariant surface, which are identified with the Julia set of the generic trace map. The density of states and the wavefunction at the band center are discussed, and we are able to classify them into three types respectively by means of its exponents.
JOSEPHSON EFFECT AND ASSOCIATED PHENOMENA IN DOUBLE-LAYER QUANTUM HALL SYSTEMS
Authors: EZAWA Z.F. , IWAZAKI A.
Published: November 2004

In certain double-layer quantum Hall systems we show the existence of Josephson phenomena such as the Josephson effect, the Meissner effect and the Anderson plasmon excitation. The distinctive feature is that the unit of the charge associated with the Josephson tunneling is e of the single electron and not 2e of the Cooper pair. We develop a theory of these Josephson phenomena by using the Chern-Simons formulation of the planar electrons. We explain our results by using the pseudospin language. Furthermore, we point out that Anderson plasmon excitations may already have been observed by a recent experiment on a double-layer quantum Hall system. A microwave experiment without attaching external leads is proposed for a direct observation of plasmon excitations.
FABRICATION TECHNIQUES FOR SELF-ALIGNED GaAs-BASED HBTs AND SUBMICRON GATE LENGTH FETs
Authors: REN F.
Published: November 2004

Process technologies for self-aligned AlGaAs/GaAs and InGaP/GaAs heterojunction bipolar transistors (HBTs) as well as gate definition and dry etching fabrication schemes for submicron gate length AlGaAs/GaAs-based field effect transistors (FETs) are presented. Multiple energy F + and H + ions were used to isolate the active devices for HBTs. The resistance of test wafers at 200° C showed no change over periods of more than 50 days. Highly selective dry and wet etch techniques for InGaP/GaAs and AlGaAs/GaAs material systems were used to uniformly expose heterojunctions. Reliability of the alloyed ohmic contact and feasibility of the nonalloyed ohmic contact metallizations for both p and n type GaAs layers will be discussed. The reproducible gate recess etching is one of the critical steps for AlGaAs/GaAs-based FETs. The etching selectivity, damage, pre- and post-clean procedures were studied in terms of device performance. A simple low temperature SiN x deposition and an etch-back process with optical stepper were used to demonstrate 0.1 µm Y-shape gate feature.
STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Bi2Sr2Ca1−xPrxCu2Oy
Authors: RAMA SITA D. , SINGH R.
Published: November 2004

Solid solutions of Bi 2 Sr 2 Ca 1−x Pr x Cu 2 O y (0 ≤ x ≤ 0.6) have been synthesized. The crystal structure and superconducting properties of the samples were examined by XRD and dc electrical resistivity measurements. Linear increase in normal state resistivity is observed with increasing Pr-content (x) for 0 ≤ x ≤ 0.55. Decrease in T c is observed with increasing x and metal–insulator transition is observed around x = 0.55. Although increase in normal state resistivity leads to decrease in T c value, we do not find any definite correlation between these parameters. The conduction mechanism in the semi-conducting sample is found to be Variable Range Hopping. From the decrease of c lattice parameter the possibility of existence of Pr ions in +4 state besides +3 state is inferred.
FIELD-INDUCED STRUCTURE OF CONFINED FERROFLUID EMULSION
Authors: LAWRENCE ERIC M. , IVEY MARK L. , FLORES GEORGE A. , LIU JING , BIBETTE J. , RICHARD J.
Published: November 2004

Field-induced phase behavior of a confined monodisperse ferrofluid emulsion was studied using optical microscopy, light transmission, and static light scattering techniques. Upon application of magnetic field, randomly-dispersed magnetic emulsion droplets form solid structures at λ = 1.5, where λ is defined as the ratio of the dipole–dipole interaction energy to the thermal energy at room temperature. The new solid phase consists of either single droplet chains, columns, or worm-like clusters, depending on the volume fraction, cell thickness and rate of field application. For the column phase, an equilibrium structure of equally-sized and spaced columns was observed. Our measurements taken for cell thickness 5µ m ≤ L ≤ 500µ m and volume fraction 0.04 show the column spacing to be reasonably described by d = 1.49L0.34.
ELECTROSTATIC INTERACTIONS FOR PARTICLE ARRAYS IN ELECTRORHEOLOGICAL FLUIDS I: CALCULATIONS
Authors: SHIH YUNG-HUI , SPRECHER A. F. , CONRAD H.
Published: November 2004

A simple effective charge method and the principle of superposition were used to calculate the total system interaction energy of two-dimensional rectangular and hexagonal arrays of particles in electrorheological suspensions. The calculations gave for static conditions (no shear) that a close-packed hexagonal array of particles was energetically favored over a rectangular array and that for very dilute suspensions a structure consisting of separated single chains was favored over one consisting of clusters. For shearing and assuming that no rotation of the polarization vector takes place, no difference in the maximum force per chain occurred for a two-chain system compared to a single-chain system in either the rectangular or close-packed hexagonal array. This was also the case with rotation of the polarization vector in the rectangular array, although the force was less with rotation compared to without rotation for this array. However, in the case of the dose-packed hexagonal array with rotation of the polarization vector there occurred an order of magnitude enhancement of the maximum force for the two-chain system compared to the single-chain system. This enhancement is comparable to the ratio of the measured strength of ER fluids to that predicted for the structure consisting of separated single chains.
ELECTROSTATIC INTERACTIONS FOR PARTICLE ARRAYS IN ELECTRORHEOLOGICAL FLUIDS II: MEASUREMENTS
Authors: CHEN YING , CONRAD H.
Published: November 2004

The force required to shear one-, two- and three-chain clusters of 230 µm dia. glass beads in silicone oil was measured. In each case the shear force was proportional to the shear strain, the proportionality constant increasing with electric field and number n of chains in the cluster. The derived shear modulus G also increased with n. An extrapolation of the present results suggests that a cluster of 4–5 chains would give the stress enhancement factor of 10–20 observed for real ER fluids.
HEAT TRANSFER MODELLING OF A CYLINDRICAL ER CATCH
Authors: SMYTH R. , TAN K. H. , BULLOUGH W. A.
Published: November 2004

In electro-rheological (ER) devices the control of temperature is often of paramount importance. For a device through which the ER fluid is not able to flow continuously to and from a reservoir, where it may be cooled, this can be a problem. Such a situation occurs in the ER catch. The heat generated there will predominantly be dissipated from the outer surface of the drive/input. The rate of heat transfer is thus principally a function of the speed and area of that surface and the temperatures of the ER fluid and atmosphere. Since these factors reflect on the levels of electro-stress, current requirement and viscosity of the ER fluid, an opportunity exists for optimisation of catch performance.

The paper shows the results of an investigation into the effects on the cooling/heating problem of varying the radii of the clutch rotors, their relative rotational speed and inter-electrode spacing. Equilibrium fluid temperatures are confirmed by experimental evidence. The effects of heat generation in run up to speed and clutch locked periods, (through electro viscous drag and dielectric loading respectively) are quantified and compared with the case of a contemporary ER fluid in a cylindrical catch on zero volts idling. At any given operating condition, uniform temperature, viscosity and constant electro stress are assumed throughout the fluid.
A DOMAIN MODEL OF CUPRATES
Authors: DALLACASA V.
Published: November 2004

We have investigated the occurrence of superconductivity in a Fermi liquid of finite volume, under the assumption of a sharp surface, by solving numerically (at arbitrary length) and analytically (at the smallest lengths) the Cooper–BCS model. We find that this model can predict enhanced superconductivity with respect to the bulk BCS model when the system length L ≪ L0, in which L0 is a characteristic length. Under the same conditions the normal state is found to behave anomalously with respect to the conventional Fermi liquid, with a linear temperature dependence of the resistivity and marginal Fermi liquid properties. The results are used to implement a domain model of high T c superconductors.
BULK PROPERTIES OF CHERN–SIMONS SUPERCONDUCTIVITY AT FINITE TEMPERATURES
Authors: MANDAL S. S. , RAMASWAMY S. , RAVISHANKAR V.
Published: November 2004

We study Chern–Simons (CS) superconductivity at finite temperatures for a system of two dimensional 'spin-1/2' fermions which are minimally coupled to both the CS and Maxwell gauge fields. We evaluate the electromagnetic response of the system as well as its thermodynamic properties within the mean field formalism. Our results for magnetic susceptibility, conductivity and dielectric constant show a sharp transition to the normal state over a narrow range of temperatures. The vanishing of the off-diagonal conductivity due to a corresponding fall in parity and time reversal [Formula: see text] violating correlation factor may be interpreted to be an effective restoration of [Formula: see text] symmetries in the macroscopic state. We find that the spin correlation function has a negligibly small numerical value at all temperatures, which implies that the thermal fluctuations dominate over the quantum fluctuations in the spin state. To explore the validity of mean field theory at high temperatures (HT), we compare the responses as well as the form factors for both mean field and free field (perturbative) formalism and find that they are essentially equivalent at HT. Finally, we present a coarse criterion for the validity of the mean field ansatz by regulating the CS Lagrangian with a Maxwell term.
GREEN FUNCTIONS IN t-J MODEL OF HIGH-Tc SUPERCONDUCTIVITY
Authors: NGUYEN VAN HIEU
Published: November 2004

The explicit expressions of the imaginary time normal and anomalous two–point Green functions in the t-J model of high-T c superconductivity without the single occupation constraint as well as those of the real time ones at a finite temperature are derived in the mean field approximation. The possible applications of these results are outlined.
CRITICAL BEHAVIOR OF NONEQUILIBRIUM MODELS WITH INFINITELY MANY ABSORBING STATES
Authors: JENSEN IWAN
Published: November 2004

I study the critical behavior of a two-dimensional dimer-trimer lattice model, introduced by Köhler and ben-Avraham,17a for heterogeneous catalysis of the reaction ½A2 + ⅓B3 → AB. The model possesses infinitely many absorbing states in which the lattice is saturated by adsorbed particles and reactions cease because only isolated vacancies are left. Results for various critical exponents show that the model exhibits the same critical behavior as directed percolation, contrary to earlier findings by Köhler and ben-Avraham. Together with several other studies, reviewed briefly in this article, this confirms that directed percolation is the generic universality class for models with infinitely many absorbing states.
RANDOM POTENTIAL INFLUENCE ON PHONON RAMAN SCATTERING IN HIGH-TEMPERATURE SUPERCONDUCTORS
Authors: MISOCHKO O.V. , SHERMAN E.YA.
Published: November 2004

Raman scattering in high-temperature superconductors is considered, assuming the presence of a random potential caused by either crystal non-stoichiometry or oxygen disorder. The renormalization of the electron-phonon interaction by impurity scattering for phonons of different symmetry has been analyzed. The analysis has been extended so as to take into consideration the finite wavevector phonons. On the basis of the theory developed, unusual properties of phonon Raman scattering in the high-temperature superconductors are qualitatively considered. They include the phonon line-shape and its dependence on the scattering polarizations and resonant conditions, and non-Bose temperature dependence of a number of Raman active phonons.
THE EFFECT OF PREMELTING: STUDY FOR SEMI-INFINITE CRYSTALS AND NANO-SYSTEMS
Authors: SCHOMMERS W.
Published: November 2004

The effect of premelting is of particular interest in connection with the theory of melting. In this paper, we discuss the structural and dynamical properties of the surfaces of semi-infinite crystals as well as of nano-clusters, which show the effect of premelting. The investigations are based on molecular-dynamics calculations: different models are used for the systematic study of the effect of premelting. In particular, the behaviour of the following functions have been studied: pair correlation function, generalized phonon density of states, and the mean-square displacement as a function of time. The calculations have been done for krypton since for this substance a reliable interaction potential is available.
SCHRÖDINGER INVARIANCE IN DISCRETE STOCHASTIC SYSTEMS
Authors: HENKEL MALTE , SCHÜTZ GUNTER
Published: November 2004

Local scale invariance for lattice models is studied using new realizations of the Schrödinger algebra. The two-point function is calculated and it turns out that the result can be reproduced from exact two-point correlation functions evaluated in the stationary state of several simple stochastic models.
INFINITE FAMILIES OF GAUGE-EQUIVALENT R-MATRICES AND GRADATIONS OF QUANTIZED AFFINE ALGEBRAS
Authors: BRACKEN ANTHONY J. , GOULD MARK D. , ZHANG YAO-ZHONG , DELIUS GUSTAV W.
Published: November 2004

Associated with the fundamental representation of a quantum algebra such as Uq(A1) or Uq(A2), there exist infinitely many gauge-equivalent R-matrices with different spectralparameter dependences. It is shown how these can be obtained by examining the infinitely many possible gradations of the corresponding quantum affine algebras, such as [Formula: see text] and [Formula: see text], and explicit formulae are obtained for those two cases. Spectral-dependent similarity (gauge) transformations relate the R-matrices in different gradations, Nevertheless, the choice of gradation can be physically significant, as is illustrated in the case of quantum affine Toda field theories.
SIGMA MODELS WITH (2, 2) WORLD SHEET SUPERSYMMETRY
Authors: DELDUC F. , SOKATCHEV E.
Published: November 2004

We propose a new mechanism for constructing (2, 2) superspace actions for WZWN sigma models. We use the already known semi-chiral superfields, but we choose the Lagrangian in a special way, so that it has a gauge invariance capable of eliminating half of the initially propagating degrees of freedom. Thus we avoid the doubling of the target space dimension. The nonlinear differential conditions on the Lagrangian are derived and it is shown that this type of action corresponds to the general (2, 2) sigma model.
NON-EQUILIBRIUM COHERENT VORTEX STATES AND SUBHARMONIC GIANT SHAPIRO STEPS IN JOSEPHSON JUNCTION ARRAYS
Authors: DOMÍNGUEZ DANIEL , JOSÉ JORGE V.
Published: November 2004

This is a review of recent work on the dynamic response of Josephson junction arrays driven by dc and ac currents. The arrays are modelled by the resistively shunted Josephson junction model, appropriate for proximity effect junctions, including self-induced magnetic fields as well as disorder. The relevance of the self-induced fields is measured as a function of a parameter κ=λL/a, with λL the London penetration depth of the arrays, and a the lattice spacing. The transition from Type II (κ>1) to Type I (κ<1) behavior is studied in detail. We compare the results for models with self, self+nearest-neighbor, and full inductance matrices. In the κ=∞ limit, we find that when the initial state has at least one vortex-antivortex pair, after a characteristic transient time these vortices unbind and radiate other vortices. These radiated vortices settle into a parity-broken, time-periodic, axisymmetric coherent vortex state (ACVS), characterized by alternate rows of positive and negative vortices lying along a tilted axis. The ACVS produces subharmonic steps in the current voltage (IV) characteristics, typical of giant Shapiro steps. For finite κ we find that the IV’s show subharmonic giant Shapiro steps, even at zero external magnetic field. We find that these subharmonic steps are produced by a whole family of coherent vortex oscillating patterns, with their structure changing as a function of κ. In general, we find that these patterns are due to a breakdown of translational invariance produced, for example, by disorder or antisymmetric edge-fields. The zero field case results are in good qualitative agreement with experiments in Nb-Au-Nb arrays.
NON-GAUSSIAN DISTRIBUTION IN RANDOM TRANSPORT DYNAMICS
Authors: TAKAYASU MISAKO , TAKAYASU HIDEKI , TAGUCHI Y-H.
Published: November 2004

Statistical properties of random transport models defined on discrete space-time are investigated both numerically and analytically. As an extreme limit we first consider aggregation limit of massive particles. With the presence of permanent injection we have a nontrivial steady state where the mass distribution follows a power law. It is shown that the steady state is universal and very robust. Next, we analyze the cases of imperfect aggregation that a finite portion is transported at a time. We have a Gaussian fluctuation governed by the ordinary diffusion equation in the nonaggregation limit, while the system converges to the power law steady state in the aggregation limit even without injection. In the intermediate cases the fluctuations are always between Gaussian and the power law. Underlying relations to the exponential-like distributions in fluid turbulence are also discussed.
PRECISION OF A QUANTUM CHARGE PUMP NEAR THE ADIABATIC REGIME
Authors: LIU CHIU , NIU QIAN
Published: November 2004

The precision of a quantum charge pump is studied through an exact solution of a time-dependent Schrödinger equation, and the noninteracting Anderson impurity model. An approximate solution to the interacting Anderson model in the strong Coulomb blockade limit is also presented. Near the adiabatic regime, the precision is rigorously found to depend exponentially on the operating frequency of the charge pump. The semiclassical rate equation is rederived when the temperature is higher than the energy quantum of the pumping frequency. Nonadiabatic heating to the leads is also discussed.
FLUX FLOW, PHASE SLIP AND HYSTERESIS IN DC RESISTIVITY OF INTER- AND INTRA-GRAIN REGIONS
Authors: HASANAIN S.K. , ASIM M.M.
Published: November 2004

The effects of flux flow, phase slip and flux redistribution between inter- and intra-grain regions are investigated via dc resistivity of a zerofield cooled granular superconductor. Differences between the low H (HHc1) behavior are explained in terms of differing pinning strengths of inter- and intra-grain regions. A minimum in ρ(θ) (θ: angle between H and J) and hysteresis effects are observed and explained via flux redistribution between grains and intergrain regions.
PHOTOCONDUCTIVE RESPONSE IN 9,10-ANTHRAQUINONE SINGLE CRYSTALS
Authors: RANA ANWAR MANZOOR , BILAL M. SHAKEEL , CHAUDHRY M. ASHRAF , SALEH M. , ALTAF M.
Published: November 2004

The photoconductive response of ‘home-grown’ 9,10-anthraquinone single crystals has been studied using two types of cells — sandwich and surface types. The existence of true bulk conductivity as well as surface conductivity has been established in such crystals. The photocarrier mobility on the surface is much higher than in the bulk of the crystal specimens. The photocurrent dependence on wavelength in the range 380–550 nm and applied bias field up to 9 kV/cm has been examined in these crystals. The field dependence of photocurrent at constant wavelength shows a nonohmic behavior. The effect of making front-illuminated electrode positive or negative with respect to the back electrode is also examined and the photocurrent is found to be electronic in nature.
ANTIFERROMAGNETISM AND HOLE CONCENTRATION IN THE LINEAR SPIN WAVE APPROXIMATION OF THE t-J MODEL
Authors: BELKASRI A. , RICHARD J.L.
Published: November 2004

The interplay between antiferromagnetic state and low doping regime is studied within the framework of the t-J model. The staggered magnetization is calculated in the mean field approximation by separating spin and charge degrees of freedom. We have obtained that this order parameter decreases with increasing doping and vanishes for some critical hole concentration.
AC MEASUREMENTS ON COEVAPORATED GeO2/BaO THIN FILMS
Authors: NADEEM M.Y.
Published: November 2004

The frequency and temperature dependence of the ac conductance and the capacitance are studied in the frequency range of 1 to 20 kHz for the coevaporated GeO 2/ BaO thin layers sandwiched between Al metallic electrodes. The measurements are undertaken to establish the low temperature conduction in these diode structures as the electronic hopping conduction. The activation energy involved in this mechanism is evaluated.
SOFT AND REPULSIVE: RELATIONSHIP BETWEEN LIPID MEMBRANE IN-PLANE FLUCTUATIONS, BENDING RIGIDITY, AND REPULSIVE UNDULATION FORCES
Authors: LEMMICH JESPER , IPSEN JOHN HJORT , HØNGER THOMAS , JØRGENSEN KENT , MOURITSEN OLE G. , MORTENSEN KELL , BAUER ROGERT
Published: November 2004

Lipid membranes are soft and flexible bilayer surfaces that exhibit a substantial degree of in-plane fluctuations which become very strong near lipid phase transitions and in phase separation regions. The fluctuations couple to the out-of-plane motions as well as the large-scale mechanical modulii of the membrane leading to a thermal renormalization of, e.g., the bending rigidity. For multilamellar arrays of membranes, changes in the bending rigidity in turn lead to changes in the entropic repulsive undulation forces that act between the lamellae and which determine their swelling behavior. We briefly review recent results obtained from theoretical and experimental studies of phospholipid bilayers that clarify the relationship between lipid bilayer in-plane fluctuations (in density and composition), bending rigidity, and repulsive undulation forces. The results discussed derive from computer simulation calculations, field theory, as well as small angle neutron scattering.
INTRINSIC FLUCTUATION OF CHUA SYSTEM
Authors: LI QIAN SHU , LEI AI ZHONG
Published: November 2004

Intrinsic fluctuation of Chua system is studied with master equation method. Our results have shown that the intrinsic noise indeed exerted considerable influence on Chua system. In contrast to that of deterministic equation the patterns of time evolution and attractor have been greatly altered under the influence of intrinsic noise.
BIFURCATIONS IN APPROXIMATE SOLUTIONS OF STOCHASTIC DELAY DIFFERENTIAL EQUATIONS
Authors: BAKER CHRISTOPHER T. H. , FORD JUDITH M. , FORD NEVILLE J.
Published: November 2004

We consider stochastic delay differential equations of the form [Formula: see text] interpreted in the Itô sense, with Y(t)=Φ(t) for t∈[t0-τ,t0] (here, W(t) is a standard Wiener process and τ>0 is the constant "lag", or "time-lag"). We are interested in bifurcations (that is, changes in the qualitative behavior of solutions of these equations) and we draw on insights from the related deterministic delay differential equation, for which there is a substantial body of known theory, and numerical results that enable us to discuss where changes occur in the behavior of the (exact and approximate) solutions of the equation.

Rather diverse components of mathematical background are necessary to understand the questions of interest. In this paper we first review some deterministic results and some basic elements of the stochastic analysis that (i) suggests lines of investigation for the stochastic case and (ii) are expected to facilitate the theoretical investigation of the stochastic problem. We then present the results of numerical experiments that illustrate some of the complexities that arise when considering bifurcations in stochastic delay differential equations. They give prima facie evidence for certain convergence properties of the bifurcation points estimated using the Euler–Maruyama method for the equations considered. We conclude by drawing attention to a number of open questions in the field.
ATTRACTOR AND BASIN PORTRAITS OF A DOUBLE SWING POWER SYSTEM
Authors: UEDA YOSHISUKE , HIRANO MAKOTO , OHTA HIROFUMI , ABRAHAM RALPH H.
Published: November 2004

In a normal power system, many generators are operating in synchrony. That is, they all have the same speed or frequency, the system frequency. In case some accident occurs, a situation might arise in which one or more generators are running at a different speed, much faster than the system frequency. They are said to be running away or stepping out, or in a state of accelerated stepping out. We have been engaged in a series of studies of this situation, and have found global attractor-basin portraits. In the course of this program, we have observed the phenomenon of decelerated stepping out, in which one or more generators deviate from the system frequency toward lower speeds. These kinds of behavior cannot be explained with the well-known model involving one generator operating on to an infinite bus. Rather, we require a model in which robust subsystems — for example, generator/motor combination, which we call swing pairs — are connected by interconnecting transmission lines. In this more general context, the deviant behaviors we are considering may be regarded as forms of desynchronization of subsystems. We therefore begin this paper with the derivation of a new mathematical model, in which there is no infinite bus nor fixed system frequency. In the simple case of two subsystems (each a swing pair) weakly coupled by an interconnecting transmission line, we develop a system of seven differential equations which include the variation of frequency in a fundamental way. We then go on to study the behavior of this model, using our usual methods of computer simulation to draw the attractor-basin portraits. We have succeeded in finding both accelerated and decelerated stepping out in this new model. In addition, we discovered an unexpected subharmonic swinging of the whole system.
AUTOMATIC GENERATION OF AESTHETIC PATTERNS ON APERIODIC TILINGS BY MEANS OF DYNAMICAL SYSTEMS
Authors: CHUNG K. W. , WANG B. N.
Published: November 2004

A new and fast algorithm is presented in this paper for the automatic generation of aesthetic patterns on aperiodic tilings by means of dynamical systems. The Penrose tilings are used as illustration of which invariant mappings are constructed for the creation of striking patterns. A modified convergence time scheme is described to enhance the artistic appeal of generated images. This algorithm can be used to create a great variety of exotic patterns with various aperiodicities.
BIFURCATIONS AND CHAOS IN TWO-CELL CELLULAR NEURAL NETWORKS WITH PERIODIC INPUTS
Authors: LIN SONG-SUN , LIN WEN-WEI , YANG TING-HUI
Published: November 2004

This study investigates bifurcations and chaos in two-cell Cellular Neural Networks (CNN) with periodic inputs. Without the inputs, the time periodic solutions are obtained for template A=[r,p,s] with p>1, r>p-1 and -s>p-1. The number of periodic solutions can be proven to be no more than two in exterior regions. The input is b sin 2πt/T with period T>0 and amplitude b>0. The typical trajectories Γ(b,T,A) and their ω-limit set ω(b,T,A) vary with b, T and A are also considered. The asymptotic limit cycles Λ∞(T,A) with period T of Γ(b,T,A) are obtained as b→∞. When [Formula: see text] (given in (67)), Λ∞and -Λ∞can be separated. The onset of chaos can be induced by crises of ω(b,T,A) and -ω(b,T,A) for suitable T and b. The ratio [Formula: see text], of largest amplitude a1(b) except for T-mode and amplitude of the T-mode of the Fast Fourier Transform (FFT) of Γ(b,T,A), can be used to compare the strength of sustained periodic cycle Λ0(A) and the inputs. When [Formula: see text], Λ0(A) dominates and the attractor ω(b,T,A) is either a quasi-periodic or a periodic. Moreover, the range b of the window of periodic cycles constitutes a devil's staircase. When [Formula: see text], finitely many chaotic regions and window regions exist and interweave with each other. In each window, the basic periodic cycle can be identified. A sequence of period-doubling is observed to the left of the basic periodic cycle and a quasi-periodic region is observed to the right of it. For large b, the input dominates, ω(b,T,A) becomes simpler, from quasi-periodic to periodic as b increases.
EFFECT OF HETEROGENEITY ON SPIRAL WAVE DYNAMICS IN SIMULATED CARDIAC TISSUE
Authors: CASSIA-MOURA R. , XIE FAGEN , CERDEIRA HILDA A.
Published: November 2004

There is considerable spatial heterogeneity in the electrical properties of the heart muscle and there are indications that anisotropic conduction may play an important role in the pathogenesis of clinical cardiac arrhythmias. Spiral waves of electrical activity are related to reentrant cardiac arrhythmias as ventricular tachycardia and ventricular fibrillation, and the generation of a wave breakup is hypothesized to underlie the transition from ventricular tachycardia to ventricular fibrillation — the leading cause of sudden cardiac death. Here we investigate the effect of heterogeneity on spiral wave reentry in a two-dimensional modified FitzHugh–Nagumo membrane model. Spiral wave breakup induced by the heterogeneity is found. The spiral wave dynamics is invariant under translational and rotational transformations in homogeneous tissue, but for heterogeneous tissue, this symmetry is broken due to the heterogeneity. The reentry dynamics depends on the degree of heterogeneity and the point where the reentry is initiated within the simulated tissue. This study may open potentially exciting new diagnostic and therapeutic possibilities in a clinical context.
A MODIFIED CHUA CIRCUIT SIMULATES 1/f-LIKE FLUCTUATION OF HEARTBEAT INTERVALS
Authors: OSAKA MOTOHISA , WATANABE MARI A.
Published: November 2004

The low-frequency portion of the power spectrum of human heartbeat intervals exhibits a 1/f-like scaling behavior. Despite its clinical significance, the mechanism remains unknown. By recording heartbeat intervals, renal sympathetic nerve activity (SNA), and blood pressure (BP) in conscious rats with normal or high BP, we reported that the scaling slope of heartbeat intervals is steeper in the rats with high BP, and that SNA leads to heartbeat interval and BP changes, and also the dynamics of these three variables, heartbeat intervals, BP, and SNA, results from a low-dimensional chaos. This hemodynamics is modeled excellently by modification of a known chaotic electrical circuit, Chua circuit. Increasing the resistive element between SNA and BP in the circuit increases the scaling slope and abolishes the low-dimensional chaos. Therefore, sensitivity of BP to sympathetic control is likely to determine the scaling slopes of heartbeat intervals in health and disease.
A NOVEL FAST IMAGE ENCRYPTION SCHEME BASED ON 3D CHAOTIC BAKER MAPS
Authors: MAO YAOBIN , CHEN GUANRONG , LIAN SHIGUO
Published: November 2004

Symmetric block encryption schemes, designed on invertible two-dimensional chaotic maps on a torus or a square, prove feasible and secure for real-time image encryption according to the commonly used criteria given in the literature. In this paper, a typical map of this kind, namely, the baker map, is further extended to be three-dimensional and then used to speed up image encryption while retaining its high degree of security. The proposed algorithm is described in detail, along with its security analysis and implementation. Experimental results show that this three-dimensional baker map is 2–3 times faster than the two-dimensional one, showing its great potential in real-time image encryption applications.
PERFORMANCE ANALYSIS OF MULTIPLE ACCESS CHAOTIC-SEQUENCE SPREAD-SPECTRUM COMMUNICATION SYSTEMS USING PARALLEL INTERFERENCE CANCELLATION RECEIVERS
Authors: TAM WAI M. , LAU FRANCIS C. M. , TSE CHI K.
Published: November 2004

In this Letter, we apply combined linear detector/parallel interference cancellation (PIC) detectors to jointly decode symbols in a multiple access chaotic-sequence spread-spectrum communication system. In particular, three different types of linear detectors, namely single-user detector, decorrelating detector and minimum mean-square-error detector, are used to estimate the transmitted symbols at the first stage of the PIC detector. The technique for deriving the approximate bit error rate (BER) is described and computer simulations are performed to verify the analytical BERs.
DETERMINISTIC CHAOS IN AN INTERPHASE LAYER OF A LIQUID–VAPOR SYSTEM
Authors: BYSTRAI G. P. , IVANOVA S. I. , STUDENOK S. I.
Published: November 2004

A second-order nonlinear differential equation with an aftereffect for the density of a thin homogeneous layer on a liquid and vapor interface is considered. The acts of evaporation and condensation of molecules, which are regarded as periodic "impacts", excite the layer. The mentioned NDE is integrated over a finite time interval to find a 2D (two-dimensional) mapping whose numerical solution describes the chaotic dynamics of density and pressure in time. The algorithms of constructing bifurcation diagrams, Lyapunov's exponents and Kolmogorov's entropy for systems with first-order, second-order phase transitions and Van der Waals' systems were elaborated. This approach allows to associate such concepts as phase transition, deterministic chaos and nonlinear processes. It also allows to answer a question whether deterministic chaos occurs in systems with phase transitions and how fast the information about starting conditions is lost within them.
CHAOTIC ENCRYPTION WITH TRANSIENT DYNAMICS INDUCED BY PSEUDO-RANDOM SWITCHING KEYS
Authors: XU DAOLIN , CHEE CHIN YI
Published: November 2004

A chaotic encryption method is proposed for digital communication using a pseudo-random switching key in which parameters irregularly adjust to a rule related to chaotic variables. The scheme derived two features — pseudo-random false switching events are densely produced to mask up binary switching and the transmitted signal possesses a transient nature thus diffusing any deterministic characteristics used by interceptors. The robustness of synchronization is discussed when the mismatch of parameters or keys occurs under erratic switching events.
RANDOMNESS AND COMPLEXITY IN PURE MATHEMATICS
Authors: CHAITIN G.J.
Published: November 2004

One normally thinks that everything that is true is true for a reason. I’ve found mathematical truths that are true for no reason at all. These mathematical truths are beyond the power of mathematical reasoning because they are accidental and random.

Using software written in Mathematica that runs on an IBM RS/6000 workstation, I constructed a perverse 200-page algebraic equation with a parameter N and 17,000 unknowns: [Formula: see text] For each whole-number value of the parameter N, we ask whether this equation has a finite or an infinite number of whole number solutions. The answers escape the power of mathematical reason because they are completely random and accidental.

This work is an extension of the famous results of Gödel and Turing using ideas from a new field called algorithmic information theory.
A DOUBLE LOGISTIC MAP
Authors: GARDINI LAURA , ABRAHAM RALPH , RECORD RONALD J. , FOURNIER-PRUNARET DANIELE
Published: November 2004

Several endomorphisms of a plane have been constructed by coupling two logistic maps. Here we study the dynamics occurring in one of them, a twisted version due to J. Dorband, which (like the other models) is rich in global bifurcations. By use of critical curves, absorbing and invariant areas are determined, inside which global bifurcations of the attracting sets (fixed points, closed invariant curves, cycles or chaotic attractors) take place. The basins of attraction of the absorbing areas are determined together with their bifurcations.
PHYSIOLOGICAL SIGNIFICANCE OF THE SHIL’NIKOV PHENOMENON IN THE FOCAL ACCOMMODATION SYSTEM OF HUMAN EYES
Authors: SUMIDA TAKEO , TAHARA TAKASHI , IWANAGA HIROAKI
Published: November 2004

We found the Shil’nikov phenomenon in the focal accommodation system of human eyes. The attractors changed form and the dynamics shifted to being periodic on stimulating the autonomic nervous system. This chaos potentially suggests that one can qualitatively grasp the state of the autonomic nervous system which innervates these systems.
THE MULTIFRACTAL FORMALISM REVISITED WITH WAVELETS
Authors: MUZY J.F. , BACRY E. , ARNEODO A.
Published: November 2004

The multifractal formalism originally introduced for singular measures is revisited using the wavelet transform. This new approach is based on the definition of partition functions from the wavelet transform modulus maxima. We demonstrate that the f(α) singularity spectrum can be readily determined from the scaling behavior of these partition functions. We show that this method provides a natural generalization of the classical box-counting techniques to fractal functions (the wavelets actually play the role of “generalized boxes”). We report on a systematic comparison between this alternative method and the structure function approach which is commonly used in the context of fully developed turbulence. We comment on the intrinsic limitations of the structure functions which possess fundamental drawbacks and do not provide a full characterization of the singularities of a signal in many cases. We show that our method based on the wavelet transform modulus maxima decomposition works in most situations and is likely to be the ground of a unified multifractal description of singular distributions. Our theoretical considerations are both illustrated on pedagogical examples, e.g., generalized devil staircases and fractional Brownian motions, and supported by numerical simulations. Recent applications of the wavelet transform modulus maxima method to experimental turbulent velocity signals at inertial range scales are compared to previous measurements based on the structure function approach. A similar analysis is carried out for the locally averaged dissipation and the validity of the Kolmogorov’s refined similarity hypothesis is discussed. To conclude, we elaborate on a wavelet based technique which goes further than a simple statistical characterization of the scaling properties of fractal objects and provides a very promising tool for solving the inverse fractal problem, i.e., for uncovering their construction rule in terms of a discrete dynamical system.
IDEAL TURBULENCE IN AN IDEALIZED TIME-DELAYED CHUA’S CIRCUIT
Authors: SHARKOVSKY A.N.
Published: November 2004

By replacing the parallel LC “resonator” in Chua’s circuit by a lossless transmission line, terminated by a short circuit, we obtain a “time-delayed Chua’s circuit” whose time evolution is described by a pair of linear partial differential equations with a nonlinear boundary condition. If we neglect the capacitance across the Chua’s diode, described by a nonsymmetric piecewiselinear vR–iR characteristic, the resulting idealized time-delayed Chua’s circuit is described exactly by a scalar nonlinear difference equation with continuous time, which makes it possible to characterize its associated nonlinear dynamics and spatial chaotic phenomena.

From a mathematical viewpoint, circuits described by ordinary differential equations can generate only temporal chaos, while the time-delayed Chua’s circuit can generate spatiotem poral chaos. Except for stepwise periodic oscillations, the typical solutions of the idealized time-delayed Chua’s circuit consist of either weak turbulence, or strong turbulence, which are examples of “ideal” (or “dry”) turbulence. In both cases, we can observe infinite processes of spatiotemporal coherent structure formations.

Under weak turbulence, the graphs of the solution tend to limit sets which are fractals with a Hausdorff dimension between 1 and 3, and is therefore larger than the topological dimension (of sets).

Under strong turbulence, the “limit” oscillations are oscillations whose amplitudes are random functions. This means that the attractor of the idealized time-delayed Chua’s circuit already contains random functions, and spatial self-stochasticity phenomenon can be observed.
ON THE STRUCTURE OF RESONANCE ZONES AND CHAOS IN NONLINEAR PARAMETRIC SYSTEMS
Authors: MOROZOV ALBERT D.
Published: November 2004

Periodic-in-time systems close to two-dimensional nonlinear Hamiltonian ones are analyzed in the case when a perturbation contains nonlinear parametric terms and it is nonconservative. The existence of new regimes in the resonance zone, regular two-frequency regimes and non-regular “quasi-attractors,” is determined. The problem of transition from a resonance case to a nonresonance one for a changing detuning is solved on the basis of the analysis of shortened auto-oscillatory systems that determine the topology of the resonance zones. The theoretical results of this investigation are illustrated on a computer for a specific example. In the quasi-conservative case the numerical and analytical results are in good agreement.
CHAOS IN A PIECEWISE LINEAR SYSTEM UNDER FREQUENCY SWITCHING
Authors: PANDE M.B. , SINGH RANJIT , GUPTA S. DUTTA
Published: November 2004

We investigate the dynamics of an oscillator with gain with switching between two cosinusoidal drives. The drive is assumed to be dependent on the state of the system and its prehistory. We show that frequency switching alone can lead to a chaotic response. Moreover, we demonstrate that resonance phenomena inhibit chaos and lead to unbounded motion. We also point out the crucial role played by the initial phases of the drives.
DESTRUCTION OF DOMINANT ARNOL’D TONGUES IN FORCED OSCILLATORS
Authors: OLESEN M.W. , KNUDSEN C.
Published: November 2004

A three-parameter numerical bifurcation analysis of the forced Brusselator model is performed. Keeping one parameter fixed the bifurcation structure in the frequency-amplitude parameter plane may, or may not, contain Arnol’d tongues. The bifurcation scenario that destroys the dominant Arnol’d tongues is described.
THE EXTENSION OF THE FEIGENBAUM-CVITANOVIĆ FUNCTION TO THE COMPLEX PLANE
Authors: WELLS A.L.J. , OVERILL R.E.
Published: November 2004

The well-known solution of the Feigenbaum-Cvitanović equation can be extended to the complex plane. The resulting analytic function has many interesting properties. Graphical representations of the function are presented, illustrating the complex fractal nature of the extended function.