bluuebunny/crossref_metadata_2025 huggingface dataset:
CAN POSITRON 2D–ACAR RESOLVE THE ELECTRONIC STRUCTURE OF HIGH-Tc SUPERCONDUCTORS?
Authors: CHAN L. P. , LYNN K. G. , HARSHMAN D. R.
Published: November 2004

We examine the ability of the positron Two-Dimensional Angular Correlation Annihilation Radiation (2D-ACAR) technique to resolve the electronic structures of high-T c cuprate superconductors. Following a short description of the technique, discussions of the theoretical assumptions, data analysis and experimental considerations, in relation to the high-T c superconductors, are given. We briefly review recent 2D-ACAR experiments on YBa 2 Cu 3 O 7−x, Bi 2 Sr 2 CaCuO 8+δ and La 2−x Sr x CuO 4. The 2D-ACAR technique is useful in resolving the band crossings associated with the layers of the superconductors that are preferentially sampled by the positrons. Together with other Fermi surface measurements (namely angle-resolved photoemission), 2D-ACAR can resolve some of the electronic structures of high-T c cuprate superconductors. In addition, 2D-ACAR measurements of YBa 2 Cu 3 O 7−x and Bi 2 Sr 2 CaCuO 8+δ also reveal an interesting temperature dependence in the fine structures, and a change in the positron lifetime in the former.
SUPERINTENSE FIELD IONISATION SUPPRESSION IN THE HIGH FREQUENCY REGIME
Authors: REED VALERIE C.
Published: November 2004

We present a brief review of the subject of ionisation suppression, or atomic stabilisation, in intense laser fields. As a preliminary, we outline the general non-linear response of an atom to a strong laser field, describing multiphoton ionisation and harmonic generation. We then discuss methods of suppressing the ionisation rate from an atom, considering two broad regimes: strong field ionisation (I < 1016 W/cm 2), in which the suppression mechanism in generally interpreted in terms of quantum interference; and superintense field ionisation (I > 1016 W/cm 2), in which the Kramers-Henneberger frame is used to interpret why atomic stabilisation can occur.
TIME-RESOLVED RAMAN STUDIES OF NON-EQUILIBRIUM EXCITATIONS IN GaAs-AlAs AND GaAs-AlxGa1−xAs MULTIPLE QUANTUM WELL STRUCTURES
Authors: TSEN K. T.
Published: November 2004

Recent experimental results obtained from time-resolved Raman studies in GaAs-AlAs and GaAs-Al x Ga 1−x As multiple quantum well structures are reviewed. Particular emphasis is made on (1) electron-phonon and phonon-phonon interactions and their association with the hot-phonon effects in the hot-carrier dynamics of multiple quantum well structures; and (2) the transport properties of photoexcited electron-hole plasma and excitons in semiconductor multiple quantum well structures.
DERIVATION OF LAUGHLIN'S WAVEFUNCTION IN ANYON SYSTEM
Authors: EZAWA Z. F. , IWAZAKI A.
Published: November 2004

In a semiclassical approximation we derive the ground-state wavefunction of the system of anyons in an external magnetic field, where anyons are interacting via the Coulomb interaction. The statistical interactions are treated in perturbation around the boson limit. The wavefunction coincides with the Laughlin wavefunction except for small corrections due to the Coulomb interaction. We also calculate the ground-state energy and the excitation spectrum.
THE SUPER COLLIDER REVISITED
Authors: HUSSEIN M. S. , PATO M. P.
Published: November 2004

We suggest a revised version of the Superconducting Super Collider (SSC) that employs the planned SSC first stage machine as an injector of 0.5 TeV protons into a power laser accelerator. The recently developed Non-linear Amplification of Inverse Bremsstrahlung Acceleration (NAIBA) concept dictates the scenario of the next stage of acceleration. Poet "Star Wars" lasers, available at several laboratories, can be used for the purpose. The 40 TeV CM energy, a target of the SSC, can be obtained with a new machine which can be 20 times smaller than the planned SSC.
OPTICAL DIFFRACTIONS AS PROBES TO SURFACE DIFFUSION OF ADSORBATES
Authors: ZHU X. D.
Published: November 2004

I review some of the general aspects of using optical diffractions from laser-induced surface density gratings to probe diffusion of adsorbates. Among examples, the recent progress in the study of quantum tunneling diffusions is emphasized.
EXACT SOLUTIONS OF SCHRODINGER'S EQUATION FOR SPIN SYSTEMS IN A CLASS OF TIME DEPENDENT MAGNETIC FIELDS: II
Authors: TAHMASEBI M. J. , SOBOUTI Y.
Published: November 2004

The case of a quantum two-level system coupled to a time variable magnetic field is investigated. The Schrodinger equation pertaining to the system is reduced to a second order linear equation in time and its solutions are sought by an integrating factor technique. A differential equation for the integrating factor and, therefrom, a criterion for fields leading to exact solutions are derived. The formalism is capable of giving a wide variety of closed form radio frequency (RF) wave forms for which Schrodinger's equation is exactly solvable.
FERMION THRESHOLD ENERGY STATES
Authors: ZHU CHANGHONG
Published: November 2004

We show that for a three-dimensional non-relativistic spinor confined on a plane, the spin-up component obeys the same equation of motion as a two-dimensional spinor. Threshold energy solution is investigated when the electron is moving in the vortex field. It can be proved from the index theorem that the existence of the threshold states depends on the magnetic flux only, not on the magnetic field configuration.
DYNAMICAL SYMMETRY OF A DIMER CLIFFORD MEAN-FIELD EXTENDED FALICOV-KIMBALL MODEL
Authors: DANANI ANDREA , RASETTI MARIO
Published: November 2004

In this letter, resorting to the Fermi-linearization technique, implemented for a two-site (dimer) cluster, we study the structure of dynamical symmetry which the use of Grassmann-Clifford mean-fields leads to, in the case of an extended Falicov-Kimball model. The resulting scheme to diagonalize the Hamiltonian is also discussed.
CONDUCTIVITIES OF POLY(2-VINYLPYRIDINE) MATRIX COMPOSITES
Authors: CHOHAN M.H. , ASGHAR M. , MAZHAR M. , RAFIQUE U.
Published: November 2004

Poly(2-Vinylpyridine) and composites (with Zn and Hg as conductive components and Poly(2-Vinylpyridine) as a matrix polymer) have been synthesized to study the electrical behaviour of these materials. The current values have been monitored at different voltages and temperatures. On the basis of different current-voltage and current-temperature curves, it is suggested that the conduction mechanism in these materials is of Poole-Frenkel type. The activation energy value determined from the slope of ln I versus (kT)−1 is approximately 0.65 eV.
THE INFLUENCE OF TRANSPORT CURRENT ON THE MAGNETIZATION OF TYPE II SUPERCONDUCTORS
Authors: WANG J. , YUE Y. , TAYLOR K.N.R. , RUSSELL G.J. , LIU H.K. , DOU S.X. , SORRELL C.C.
Published: November 2004

The critical state model has been used to study the influence of transport current on the measured magnetization of type II superconductors. For the flux-pinned condition, it is shown that the field distribution within the sample can be described in terms of a number of regions in H−1 space. The boundaries of these regions have been established and the corresponding dependence of the magnetization on field (at fixed finite current) and current (at fixed applied field) has been calculated.
AXIAL CHROMATIC ABERRATION OF SINGLE-POLE LENS
Authors: ALAMIR A.S.A.
Published: November 2004

The axial chromatic aberration coefficient of single-pole lens is studied. Using the paraxial ray equation the axial chromatic aberration of exponential field model, which represented as a first approximation the field of single-pole lens, was analytically expressed.
A SELF-ENERGY FUNCTIONAL FOR THE INFINITE-DIMENSIONAL HUBBARD MODEL
Authors: LI Y.M. , d’AMBRUMENIL N.
Published: November 2004

We present an approximate self-energy functional for the infinite-dimensional Hubbard model. This functional is a natural extension of the exact solution of the Falicov-Kimball model to the spin-symmetric case, and is exact in the uncorrelated and atomic limits. Using the functional we calculate the susceptibility and the specific heat for the Lorentzian density of states. We find that the susceptibility crosses over smoothly from that expected for an uncorrelated state with antiferromagnetic fluctuations to a Fermi liquid state at low temperature via a Kondo-type anomaly. The specific heat shows a peak at the corresponding Kondo temperature.
FROM "SOCCER-BALL" AND "RUGBY-BALL" TO GIANT FULLERENE MOLECULES: A SCANNING TUNNELING MICROSCOPY AND SPECTROSCOPY STUDY
Authors: CHEN TING , SARID DROR
Published: November 2004

Thin films of carbon fullerene molecules, Cn, prepared on metallic substrates are studied by scanning tunneling microscopy (STM) and atomic force microscopy (AFM) under both ambient and ultrahigh vacuum conditions. The STM and AFM images provide real-space atomic-resolution views of these fascinating molecules and their monolayer growth on metal surfaces which reflect both the intermolecular interactions and interactions with the underlying substrates.
ANOMALOUS DIFFUSION NEAR STRUCTURAL PHASE TRANSITIONS
Authors: HAN W. K. , YING S. C. , ALA-NISSILA T.
Published: November 2004

Using a recently developed microscopic theory of diffusion for a particle coupled to an inhomogeneous medium, it has been shown that in the case of a structural phase transition with a diverging central peak, a diffusion anomaly occurs. We review results of model calculations demonstrating this anomaly on the W(100) surface, as well as discuss other physical systems where analogous phenomena may be observed.
TWO TOPICS CONCERNING TWO-DIMENSIONAL AUTOMATA OPERATING IN PARALLEL
Authors: INOUE KATSUSHI , SAKURAMOTO ITSUO , SAKAMOTO MAKOTO , TAKANAMI ITSUO
Published: November 2004

This paper deals with two topics concerning two-dimensional automata operating in parallel. We first investigate a relationship between the accepting powers of two-dimensional alternating finite automata (2-AFAs) and nondeterministic bottom-up pyramid cellular acceptors (NUPCAs), and show that Ω ( diameter × log diameter ) time is necessary for NUPCAs to simulate 2-AFAs. We then investigate space complexity of two-dimensional alternating Turing machines (2-ATMs) operating in small space, and show that if L (n) is a two-dimensionally space-constructible function such that lim n → ∞ L (n)/ loglog n > 1 and L (n) ≤ log n, and L′ (n) is a function satisfying L′ (n) =o (L(n)), then there exists a set accepted by some strongly L (n) space-bounded two-dimensional deterministic Turing machine, but not accepted by any weakly L′ (n) space-bounded 2-ATM, and thus there exists a rich space hierarchy for weakly S (n) space-bounded 2-ATMs with loglog n ≤ S (n) ≤ log n.
RECOGNIZABLE PICTURE LANGUAGES
Authors: GIAMMARRESI DORA , RESTIVO ANTONIO
Published: November 2004

The purpose of this paper is to propose a new notion of recognizability for picture (two-dimensional) languages extending the characterization of one-dimensional recognizable languages in terms of local languages and alphabetic mappings. We first introduce the family of local picture languages (denoted by LOC) and, in particular, prove the undecidability of the emptiness problem. Then we define the new family of recognizable picture languages (denoted by REC). We study some combinatorial and language theoretic properties of REC such as ambiguity, closure properties or undecidability results. Finally we compare the family REC with the classical families of languages recognized by four-way automata.
OBJECT BACKGROUND CLASSIFICATION USING HOPFIELD TYPE NEURAL NETWORK
Authors: GHOSH ASHISH , PAL NIKHIL R. , PAL SANKAR K.
Published: November 2004

Object extraction algorithms with a Neural Network (NN) are described. The objective function to be minimized for object extraction from a scene is shown to be similar to the expression of energy of a neural network. A modified version of Hopfield's Neural Network model is used here. The weights and input biases are given in such a way that the network self-organizes to form compact clusters. Both the discrete and the continuous dynamics of the network have been used for this purpose. Performance of the proposed methods has been compared with that of the relaxation technique.
AVOIDANCE OF NEGATIVE DELAYS
Authors: MHEIR-EL-SAADI FARID , KAMINSKA BOZENA
Published: November 2004

Computing propagation delays from analog signals using a fixed threshold voltage value sometimes yields negative values. When these delay results are used to compute the effective channel resistance of transistors or to make timing specifications of library modules, negative values are unacceptable and must be avoided. We introduce a delay computation definition with variable threshold that is guaranteed to return a positive delay value. This delay computation procedure has been used successfully for all timing requirements of PREDICT, our hierarchical delay analysis tool.
CONFINORS AND BOUNDED-TIME PATTERNS IN CHUA'S CIRCUIT AND THE DOUBLE SCROLL FAMILY
Authors: LOZI RENÉ , USHIKI SHIGEHIRO
Published: November 2004

We study the patterns in the time waveforms of the spiral attractors of the double scroll equations for the theoretical Chua's parameters. We introduce several mathematical tools linked to these equations (half-Poincaré maps, isochronic lines, selecting curves and antiselecting curves, spirals and antispirals, theorems of the turnstile, patterns and confinors). We prove that for given values of the parameters, only patterns in the time waveforms which are bounded in time can exist.
SATURATED OUTPUTS FOR HIGH-GAIN, SELF-EXCITING NETWORKS
Authors: HIRSCH MORRIS W.
Published: November 2004

We consider a broad class of continuous time dynamical systems modeling a collection of processing units sending signals to each other. Each unit has an internal state variable xi and an output variable yi which is a nondecreasing function gi (xi). Certain outputs, called "forced", are of the form σj (Kxj) where σj is a sigmoid and K > 0 is a parameter called "gain". The dynamics is given by a system of differential equations of the form dx/dt = H (x, y, t). The system is self-exciting: ∂Hi/∂yi ≥ 0, and > 0 for the forced outputs. We show that for sufficiently high gain, the forced outputs are close to the asymptotic limiting values of the sigmoids along any stable solution x (t) defined on a finite interval J, for a proportion of t ∈ J that approaches 1 as K → ∞. This generalizes Hopfield's Saturation Theorem about additive neural networks with symmetric weight matrices.
A SURVEY OF SPIRAL-WAVE BEHAVIORS IN THE OREGONATOR MODEL
Authors: JAHNKE WOLFGANG , WINFREE ARTHUR T.
Published: November 2004

We carried out a numerical exploration of spiral waves in a typical excitable medium, emphasizing the variety of behaviors encountered while changing two parameters of local excitability: the threshold for starting an excitation and the excitation rate at the wavefront. Within this parameter plane we found domains in which: 1) propagation is impossible, 2) propagation succeeds but there are no spiral waves, 3) spiral waves are stable and strictly periodic, 4) spiral waves exhibit two-period quasiperiodicity, and 5) spiral waves exhibit complex behavior that might be associated with the well-known instability of three-period flows on the three-torus. The boundary curves (bifurcation loci) separating these domains run parallel to the propagation boundary over much of their extent.
BERNOULLI PARTITION-EQUIVALENCE OF INTERMITTENT NEURONAL DISCHARGE PATTERNS
Authors: SELZ KAREN A. , MANDELL ARNOLD J.
Published: November 2004

The binary partition of the range of values for a series of interspike intervals necessary to generate the growth rate of the longest run equivalent to that observed in a Bernoulli, fair coin sequence was found to discriminate three classes of intermittently firing brain stem neurons more clearly than either the higher statistical moments or the leading Lyapunov exponent.
A PHYSICAL INTERPRETATION OF MELNIKOV’S METHOD
Authors: KETEMA YOHANNES
Published: November 2004

This paper is concerned with analyzing Melnikov’s method in terms of the flow generated by a vector field in contrast to the approach based on the Poincare map and giving a physical interpretation of the method. It is shown that the direct implication of a transverse crossing between the stable and unstable manifolds to a saddle point of the Poincare map is the existence of two distinct preserved homoclinic orbits of the continuous time system. The stability of these orbits and their role in the phenomenon of sensitive dependence on initial conditions is discussed and a physical example is given.
IDEAL TURBULENCE: ATTRACTORS OF DETERMINISTIC SYSTEMS MAY LIE IN THE SPACE OF RANDOM FIELDS
Authors: SHARKOVSKY A.N. , ROMANENKO E. YU.
Published: November 2004

We suggest a mathematical concept of self-stochasticity that may underlie a possible scenario of spacetime chaos in ideal medium (e.g. ideal turbulence). The self-stochasticity implies that the deterministic system which describes evolution of deterministic vector fields has trajectories whose ω-limit sets lie in the space of random vector fields. We consider a class of systems where almost all trajectories exhibit this property and, hence, the attractor consists of random fields.
CHAOTIC BEHAVIOR OF FRICTION FORCE
Authors: WOJEWODA JERZY , BARRON RONALD , KAPITANIAK TOMASZ
Published: November 2004

Experimental results of friction in a mechanical system are reported. Strange properties of the friction force-velocity dependence are shown, where this relationship does not follow the typical assumption of the force proportional to the sign of the relative velocity.
WHAT CAN COMPLEX TIME TELL US ABOUT REAL TIME DYNAMICS?
Authors: BOUNTIS TASSOS C.
Published: November 2004

In this tutorial we will review the successes and limitations of singularity analysis of dynamical systems, the progress made to date and the prospects for future research. By singularity analysis we mean the identification of the nature of all movable (i.e., initial condition dependent) singularities of a dynamical system in the complex time plane, and the study of the (generally complex) solutions of the system, in the vicinity of these singularities. The emphasis will be on the main ideas, methods and techniques, and the presentation will focus on examples and applications. However, a description of the most important theoretical developments and an outline of the main rigorous results will also be given. Our central theme throughout this review will be the connection between complex time singularities and the properties of the solutions of a dynamical system in real time.
SELF-ORGANIZATION IN BIOLOGICAL TISSUES: ANALYSIS OF ASYNCHRONOUS AND SYNCHRONOUS PERIODICITY, TURBULENCE AND SYNCHRONOUS CHAOS EMERGENT IN COUPLED CHAOTIC ARRAYS
Authors: KLEVECZ ROBERT R. , BOLEN JAMES , DURÁN OSCAR
Published: November 2004

Large discrete arrays of chaotic attractors, coupled by diffusion, organize into asynchronous periodic spiral waves, synchronous periodic bands, turbulent fields or synchronous chaos as a function of coupling strength and array size. Self-organization of periodic spirals in both two and three dimensional arrays of nonexcitable systems appears to require the early establishment of an antipodal phase relationship between the few cells that will form the vortex. Cells within or close to the vortex maintain low z amplitude, near limit cycle trajectories, with stable, well-defined phase relationships. In periodic banding structures, initial antipodal phase seeds evolve to isochrons that form nested periodic trajectories. The likelihood that biological systems are fundamentally oscillatory and chaotic is discussed.
NEW PROPERTIES OF QUASIPERIODIC SOLUTIONS OF THE COMPLEX GINZBURG-LANDAU EQUATION
Authors: AKHROMEYEVA TATIANA S. , MALINETSKII GEORGE G. , POTAPOV ALEXEY B. , TSERTSVADZE GEORGE Z.
Published: November 2004

By using analytical and numerical methods the authors study one of the basic models of mathematical physics—the so-called complex Ginzburg-Landau equation [Formula: see text] with the provision that no fluxes exist at the segment boundaries. A new class of solutions is found for this equation. It is shown that among its solutions there are analogs of limiting cycles of the second kind. A value describing these analogs is introduced, and a scenario of its variation depending on the parameters of the problem is given. A new type of spontaneous appearance of symmetry is shown when we go from initial data in the general form to spatially symmetrical solutions describing quasiperiodic regimes.
SIGNAL AMPLIFICATION VIA CHAOS: EXPERIMENTAL EVIDENCE
Authors: HALLE K.S. , CHUA L.O. , ANISHCHENKO V.S. , SAFONOVA M.A.
Published: November 2004

Experimental evidence showing the existence of signal amplification via perturbation of periodic and chaotic orbits in an electronic circuit is presented.
EFFECTS DUE TO LOW VELOCITY IMPACT IN MECHANICAL OSCILLATORS
Authors: NORDMARK A. B.
Published: November 2004

Phenomena caused by low velocity impacts in a class of forced impact oscillators are studied. It is shown that such impacts play an important role in the dynamics of general impacting systems. Features observed in numerical simulations of different oscillator models are associated with previous theoretical work on grazing impact. The Poincaré mapping geometry near points leading to low velocity impacts is shown, as well as bifurcations of types not found in nonimpacting systems. The consequences of not having a completely rigid constraint and the connection with the limiting case of a pure constraint are examined. In addition, low velocity impact in a Hamiltonian system is shown to have considerable effect on the break up of invariant tori.
GLOBAL CONTACT DYNAMICS OF AN ICE-STRUCTURE INTERACTION MODEL
Authors: TROESCH ARMIN W. , KARR DALE G. , BEIER KLAUS-PETER
Published: November 2004

The interaction between a moving ice sheet and an elastic structure is studied using the analogue model of Matlock, et al. [1969]. The ice sheet is represented by a series of teeth with bilinear, discontinuous stiffness. A global analysis of the resulting dynamical system is performed. Using a combination of analytical and numerical techniques, periodic solutions are determined and basin boundaries of the Poincaré map identified. While the total system dynamics are quite complex, two types of threshold solutions are found, each necessary but not sufficient in defining local separatrices.
UNIVERSAL MULTIFRACTAL CHARACTERIZATION AND SIMULATION OF SPEECH
Authors: LARNDER CHRIS , DESAULNIERS-SOUCY NICOLAS , LOVEJOY SHAUN , SCHERTZER DANIEL , BRAUN CLAUDE , LAVALLEE D.
Published: November 2004

In the 1970's it was found that; for low frequencies (<10 Hz), speech is scaling: it has no characteristic time scale. Now such scale invariance is associated with multiscaling statistics, and multifractal structures. Just as Gaussian noises frequently arise because they are generically produced by sums of many independent noise processes, scaling noises have an analogous universal behavior arising from nonlinear mixing of processes. We show that low frequency speech is consistent with these ideas, and use the measured parameters to produce stochastic speech simulations which are strikingly similar to real speech.
INTEGRATING USER INTERFACE DEVELOPMENT AND MODERN SOFTWARE DEVELOPMENT
Authors: DAVID HURLEY W.
Published: November 2004

A long-term goal for software engineers is integrating the separate processes of user interface development and modern software development. With emergent CASE technology, software engineers can begin to explore ways to achieve this integration. Exploration involves investigating candidate methodologies that let developers apply different development strategies to different parts of an interactive system. Disciplined long-term investigation requires that the fundamental principles governing each process be fixed and that evolving development methods comprising each process be accommodated. This paper proposes a computer-based process model that fixes the principles and accommodates evolving methods. Model features include a collection of software engineering and knowledge engineering techniques that supports a development organization of human and computer-based agents, a coordination activity that supports opportunistic behavior of developers, a unifying representation that leads to mutually consistent results from developers, and an extendable topology that enhances collaboration among developers while reducing their communications burden.
OBJECT-ORIENTED ANALYSIS AS DESIGN: A CASE STUDY
Authors: ZUALKERNAN I. A. , TSAI W. T. , JEMIE A. , WEN I. C. , DRAKE J. M.
Published: November 2004

Object-oriented analysis is the activity of understanding a problem domain and developing a specification for it within an object-oriented paradigm. In this paper we propose object-oriented analysis can be viewed as a design task that consists of analysis, synthesis and internal and external completeness and consistency checking. We postulate a blackboard based design framework and propose several alternative theories within this framework. Data from an expert analyst is collected and analyzed for relative explanatory power of the alternative theories. Basic findings are that viewed as a design activity, object-oriented analysis is neither top-down nor completely opportunistic in nature, Rather, (1) analysis (the process of finding objects and processes) and synthesis (constructing the object model and state-transition diagrams) are complementary activities while internal completeness and consistency checking is coupled with synthesis and (2) construction of objects and processes are cyclic and complementary processes. The findings are compared with both descriptive and normative research in automated software design.
ALMOST EVERY GROUP IS HYPERBOLIC
Authors: OL’SHANSKII A. YU.
Published: November 2004

The author gives a confirmation of M. Gromov’s claim that, in a definite statistical meaning, almost every group is hyperbolic.
THE COMPLEXITY OF DECIDING CODE AND MONOID PROPERTIES FOR REGULAR SETS
Authors: HUYNH DUNG T.
Published: November 2004

In this paper, we study the complexity of deciding code and monoid properties for regular sets specified by deterministic or nondeterministic finite automata. The results are as follows. The code problem for regular sets specified by deterministic or nondeterministic finite automata is NL-complete under NC(1) reducibilities. The problems of determining whether a regular set given by a deterministic finite automaton is a monoid or a free monoid or a finitely generated monoid are all NL-complete under NC(1) reducibilities. These monoid problems become PSPACE-complete if the regular sets are specified by nondeterministic finite automata instead. The maximal code problem for deterministic finite automata is shown to be in DET and NL-hard, while a PSPACE upper bound and NP-hardness lower bound hold for the case of nondeterministic finite automata.
ON THE IDENTITIES OF REPRESENTATIONS OF FINITE GROUPS OVER COMMUTATIVE RINGS
Authors: VOVSI SAMUEL M.
Published: November 2004

Let K be a commutative noetherian ring. It is proved that a representation of a finite group on a K-module of finite length or on a K-module of finite exponent has a finite basis for its identities. In particular, this implies an earlier result of Nguyen Hung Shon and the author stating that every representation of a finite group over a field is finitely based. The problem whether every representation of a finite group over a commutative noetherian ring is finitely based still remains open.
SMALL MODELS OF THE HIGH SCHOOL IDENTITIES
Authors: BURRIS STANLEY , LEE SIMON
Published: November 2004

First we look at some easy ways to construct small models of the High School Identities. And then we prove that any model which rejects the Wilkie identity must have at least seven elements; and we show that we have such a model with fifteen elements.
LARGE, WEAKLY SATURATING THIRD-ORDER NONLINEAR SUSCEPTIBILITIES IN SEMIMETALS AND NARROW-GAP SEMICONDUCTORS
Authors: YOUNGDALE E.R. , MEYER J.R. , BARTOLI F.J. , HOFFMAN C.A.
Published: November 2004

We review recent experimental and theoretical work on optical nonlinearities in semimetals and narrow-gap semiconductors. A strong nonlinear response due to optical modulation of the free carrier susceptibility is seen to be a common feature of these materials, with large third-order nonlinear susceptibilities being reported for Hg 1−x Cd x Te , Hg 1−x Mn x Te , Hg-based superlattices, α- Sn 1−x Ge x, Pb 1−x Sn x Se , and Bi 1−x Sb x. Effects of differences in the various band structures are discussed for nonlinearities due to nonparabolicity, thermal carrier generation, and nonequilibrium carrier generation. Mechanisms leading to either partial or severe saturation are also considered. Optimized nonlinearities for the various mechanisms and materials are critically compared, and promising future directions for the field are suggested.
THE EXPERIMENTAL STUDY OF SELF-PUMPED PHASE CONJUGATOR WITH RING CAVITY IN A PHOTOREFRACTIVE CRYSTAL
Authors: ZHANG H.Z. , TANG S.H. , HE X.H. , WANG W.L.
Published: November 2004

Two specially cut KNbO3: Fe crystals were used to study the self-pumped phase conjugation with external and internal ring cavities. The design and operation of these conjugators are described. The self-pumped phase conjugator with internal ring cavity can be used as a broadband phase conjugate mirror over a wide wavelength range with high reflectivities ranging from 60% at 488 nm to 63% at 514.5 nm to 40% at 633 nm. A maximum reflectivity of 74.8% at 514.5 nm was obtained. The product P.T, where T is the creation time of the phase conjugate wave and P is the input power, is almost a constant for a given wavelength. The phase conjugate nature of retroreflected beam has been further confirmed by a significant reduction in the specular reflectivity at the input surface of the crystal.
A TOOL SYSTEM FOR KNOWLEDGE-BASED ON-LINE DIAGNOSIS IN INDUSTRIAL AUTOMATION
Authors: BECK TH.
Published: November 2004

The use of knowledge-based techniques in real-time application is still a challenge. There are some special problems increasing in this kind of application: Handling of events to process new incoming data, the ability to perform several inferences in parallel, the ability to reason about time, etc.

We present a tool system which supports the development of expert systems to be used in the field of industrial automation. The methods provided by the tool system support

• the representation of temporal knowledge and reasoning about events in time,

• the handling of asynchronous events,

• the integration of knowledge-based components into conventional real-time software systems, and

• the reasoning under time constraints.

As a further part of the tool system, an expert system compiler with the ability to transform expert systems into a conventional procedural program (realized in C) is described. This method allows an efficient realization of knowledge-based components.
SEMANTIC NETWORK ARCHITECTURES: AN EVALUATION
Authors: DELGADO-FRIAS JOSE G. , VASSILIADIS STAMATIS , GOSHTASBI JAMSHID
Published: November 2004

Semantic networks as a means for knowledge representation and manipulation are used in many artificial intelligence applications. A number of computer architectures, that have been reported for semantic network processing, are presented in this paper. A novel set of evaluation criteria for such semantic network architectures has been developed. Semantic network processing as well as architectural issues are considered in such evaluation criteria. A study of how the reported architectures meet the requirements of each criterion is presented. This set of evaluation criteria is useful for future designs of machines for semantic networks because of its comprehensive range of issues on semantic networks and architectures.
KNOWLEDGE COMMUNICATION IN INTELLIGENT INFORMATION SYSTEMS
Authors: WOO CARSON C. , LOCHOVSKY FREDERICK H.
Published: November 2004

An intelligent information system may be composed of hundreds or thousands of entities each of which may possess some part of the overall knowledge of an organization. In such an environment there is a need for these entities to communicate in order to share knowledge and to cooperate in accomplishing organizational activities. In this paper we propose an architecture for modelling intelligent information systems and discuss how this architecture supports the communication of knowledge in such information systems.
SYMMETRY GROUPS OF HYPERBOLIC KNOTS AND LINKS
Authors: HENRY SHAWN R. , WEEKS JEFFREY R.
Published: November 2004

Canonical triangulations provide an algorithm to compute the symmetry groups of hyperbolic links and their complements, along with information on how each symmetry acts on the link components. The latter information determines the chirality and invertibility of the link. Symmetry groups of knots to ten crossings and multicomponent hyperbolic links to nine crossing are listed, with some exceptions. A Macintosh computer program, available free of charge, computes symmetry groups interactively.
STABLE EQUIVALENCE OF RIBBON PRESENTATIONS
Authors: MARUMOTO YOSHIHIKO
Published: November 2004

We introduce a ribbon presentation to describe a ribbon knot, and equivalences between them. Superspun knots of classical knots are well known to be ribbon knots, and we give a construction of ribbon presentations of the knots by means of classical knot diagrams. We can then extend the classical Reidemeister moves into higher dimensions, and we prove that the presentations of a superspun knot are stably equivalent by using these moves.
THE GENUS OF CLOSED 3-BRAIDS
Authors: XU PEIJUN
Published: November 2004

The problem of finding the genus of a given link type of braid index 3 is solved by constructive methods. The results depend upon a new solution to the conjugacy problem in B3. In this solution, conjugacy classes are represented by shortest words in terms of cyclically symmetric elementary braids which are used as generators in the new presentation of B3. By related results of Bennequin [2] and of Birman and Menasco [4], the minimal spanning surfaces are described by these shortest words. An effective algorithm is given to find these shortest words starting with an arbitrary 3-braid representative of the link. It is proved that up to an easily described family of exceptional cases, a link of braid index 3 has a unique isotopy class of minimal spanning surfaces. The growth functions of B3 and its conjugacy classes are also given here.
NEUTRINO OBSERVATIONS OF THE 1987 SUPERNOVA: A Long Time Ago in a Galaxy Far Away
Authors: LOSECCO J.M.
Published: November 2004

A summary and comparison of neutrino observations of the 1987 supernova is presented. Attention is paid to comparing and contrasting the different observations and capabilities of the different detectors. Details of the timing, energy and angular distributions are discussed. Considerations for future detections are mentioned.
THE COSMOLOGICAL CONSTANT PROBLEM
Authors: NG Y. JACK
Published: November 2004

The cosmological constant is a macroscopic parameter which controls the large-scale structure of the Universe. All observations to date have shown that it is very small. However, our modern microscopic theory of particle physics and gravity suggests that the cosmological constant should be very large. This discrepancy between theoretical expectation and empirical observation constitutes the cosmological constant problem. After a review of the problem, some approaches to its solution are briefly discussed, and then a possible solution is proposed. In this approach, the cosmological constant appears as a constant of integration, unrelated to any parameters in the Lagrangian. The solution makes crucial use of quantum mechanics.
THE PHYSICS OF 2D STRINGY SPACETIMES
Authors: GIBBONS G.W. , PERRY MALCOLM J.
Published: November 2004

We examine the two-dimensional spacetimes that emerge from string theory. We find all of the solutions with no tachyons, and show that the only nontrivial solution is the black-hole spacetime. We examine the role of duality in this picture. We then explore the thermodynamics of these solutions which is complicated by the fact that only in two spacetime dimensions is it impossible to redefine the dilaton field in terms of a canonical scalar field. Finally, we extend our analysis to the heterotic string, and briefly comment on exact, as opposed to perturbative, solutions.
THE TWISTED EUCLIDEAN GREEN’S FUNCTION IN THE SPACETIME OF A COSMIC STRING
Authors: LINET B.
Published: November 2004

In a conical spacetime, we determine the twisted Euclidean Green’s function for a massive scalar field. In particular, we give a convenient form for studying the vacuum averages. We then derive an integral expression of the vacuum expectation value <Φ2(x)>. In the Minkowski spacetime, we express <Φ2(x)> in terms of elementary functions.
THE PHASE-SPACE VIEW OF INFLATION II: FOURTH-ORDER MODELS
Authors: CAPOZZIELLO SALVATORE , OCCHIONERO FRANCO , AMENDOLA LUCA
Published: November 2004

The phase space portrait of the cosmological models deduced from fourth-order gravity theories is discussed with the analytical and numerical methods of our previous paper. A comparison is carried out between models inferred from Lagrangian densities containing powers higher than two in the Ricci scalar of curvature, and the Starobinsky model. Some peculiar structures, such as attractors and singular points, emerging neatly from both theories, have a close physical affinity, in addition to the mathematical one. Trajectories of interest in both scenarios are those undergoing an inflationary expansion and then reaching a Friedmannian asymptotic stable phase. These features are moreover discussed through a potential U(R) in RN-models. Three kinds of potential regions are recognized. They are the allowed regions (a-regions), in which trajectories can reach the Friedmannian phase after possibly undergoing an inflationary period, the disconnected regions (d-regions), in which trajectories, although physical, never reach the Friedmannian stage and the forbidden regions (f-regions), in which there are no physical solutions. A general survey of the global phase space for Starobinsky and RN-models is given via Poincaré projections of suitable variables. a-, d-, and f-regions are represented.
ANALYTICAL FORMULATION OF THE ION–ION INTERACTION POTENTIAL INCLUDING SPIN DENSITY TERM IN ENERGY DENSITY FORMALISM
Authors: PURI RAJEEV K. , GUPTA RAJ K.
Published: November 2004

The heavy-ion interaction potentials are calculated in sudden approximation, using the Fermi density distribution in the proximity theorem treatment of the Skyrme interaction energy density formalism. The contribution of the spin density term is included and the effects of varying the Skyrme force parameters, Fermi density parameters and the strength of the surface correction to Thomas–Fermi kinetic energy density are studied in detail. The universality of the "universal function" of proximity potential is tested and analytical formulas are obtained for both the proximity potential and spin density dependent potentials. The analytical formula for spin density potential works only for colliding nuclei belonging to the same shell. Adding the Coulomb potential, the interaction barriers and their positions can now be calculated analytically which are required for the calculations of fusion cross-sections. Our calculations are made for both the closed and unclosed shell nuclei consisting of light spherical nuclei from 0d-1s and 0f 7/2 shells. In all, over 100 cases are studied and comparisons with other model calculations are presented.
ELECTROPRODUCTION OF LIGHT QUARK BARYONS
Authors: Burkert Volker D.
Published: November 2004

The status of electromagnetic excitation of light quark (u, d) baryon states is reviewed and confronted with results of calculations within the framework of microscopic models of the baryon structure and the photon — baryon coupling. Prospects for a qualitative improvement of our knowledge in this sector using photon and electron beams at the new, intermediate energy continuous wave (CW) electron machines are discussed.
Perturbative Quantum Chromodynamics in Inelastic and Elastic Processes
Authors: Carlson C. E.
Published: November 2004

Several topics under the heading of perturbative quantum chromodynamics (pQCD) are discussed.
INTRODUCTION TO COLOR TRANSPARENCY
Authors: MILLER GERALD A.
Published: November 2004

I present a primer on color transparency. The essential elements of the input physics are shown to lead to an unadorned, but useful, model. The consequences of this model are analyzed with a view towards improving the precision of future calculations.
PARTICLE AND FRAGMENT EMISSION IN VIOLENT RELATIVISTIC HEAVY-ION COLLISIONS: THE 4π-DETECTOR AT GSI, A NEW FACILITY FOR THIS INVESTIGATION
Authors:   for the 4π-COLLABORATION, Presently the 4π-Collaboration at GSI comprises the following members and Institutes: R. Bock, Z. G. Fan, Z. Fodor, A. Gobbi, K. D. Hildenbrand, S. C. Jeong, M. Kramer, W. Reisdorf, D. Schüll, U. Sodan, K. M. Teh, J. Wessels (GSI Darmstadt); N. Herrmann, W. Jakel, R. Linke, D. Pelte, R. Schlesier, M. Trzaska, T. Wienold (Univ. of Heidelberg); T. Blaich (Univ. of Mainz); C. Cerruti, J. P. Coffin, P. Fintz, G. Guillaume, F. Jundt, A. Houari, C. Kuhn, C. F. Maguire, F. Rami, R. Tezkr, COFFIN J. P.
Published: November 2004

By the end of 1989 a new accelerator complex, SIS/ESR, comprising a synchrotron and a storage ring for heavy-ions, came into operation at GSI (Darmstadt). To serve this facility, the construction of a detection ensemble devoted to the measurement of π, K, p, complex particles (Z ≤ 2) and fragments (Z > 2) operating in a near 4π geometry has been undertaken. Charged particles and fragments only are dealt with in this contribution. The main motivations of Physics which justify such an enterprise are exposed, then the part (Phase I) of the detector designed for particle and fragment detection, is described in some detail while the Phase II, not yet operational, is only touched upon. Some first results obtained from measurements relative to Au (150 A MeV ) + Au central collisions are presented and discussed.
TOWARDS AN EVOLUTIONARY THEORY OF SMALL FIRM GROWTH
Authors: FREEL MARK S.
Published: November 2004

The ultimately unsuccessful predictive modelling literature has advanced our understanding of small firm growth processes no further than the descriptive and inflexible stage models approach achieved during the 1970s and 1980s. Consequently, this paper suggests an alternative theoretical starting point. Drawing upon the, predominantly aggregate level, contributions of evolutionary and institutional economists it is the intention of this paper to suggest more appropriate foundations for future firm level empirical analyses. With reference to four detailed case studies a preliminary model of small firm growth is posited and potential areas for future ethnographic and survey based research are signalled.
THE ENTREPRENEURIAL SELF-EFFICACY OF NASCENT ENTREPRENEURS: THE CASE OF TWO ECONOMIES IN TRANSITION
Authors: DRNOVSEK MATEJA , GLAS MIROSLAV
Published: November 2004

This research is concerned with entrepreneurial intentions of two specific groups of nascent entrepreneurs - innovators and graduate students in two transition economies – Slovenia and the Czech Republic. The analysis gives further contribution to previous research on predictions of entrepreneurial events using items inventory of entrepreneurial self-efficacy previously developed within the Anglo-Saxon cultural environment and now tested in a specific environment of post communist economist economies. Results show that there are relatively more nascent entrepreneurs among innovators than among graduate students of business. When average scores on self-efficacy are involved, innovators feel comfortable when dealing with innovation and risk, while graduate students express higher self-efficacy in the business-related aspects of a new venture – marketing and finance. We found a reasonable fit to our sample of the entrepreneurial self-efficacy construct as introduced by Chen et al (1998).
EAST ASIAN SMEs: LEARNING THE TECHNOLOGY
Authors: ZUTSHI RAVI K
Published: November 2004

The economic growth in East Asia has caught the attention of the world. But the ability of the East Asian entrepreneurial class to compete in the technology intensive industries and hence the sustainability of the East Asian growth has been questioned by many. This paper examines the growth of the Chinese entrepreneurial class in Singapore, Taiwan and Hong Kong. It is argued that the Chinese family businesses in East Asia are being transformed and a new technology oriented entrepreneurial class is fast emerging. These entrepreneurs are integrating the Confucian ethics and the traditional cultural patterns with a modern world view. With support from the government they are leveraging their networking abilities to form regional alliances for cost competitiveness. At the same time they are moving up the technology ladder by allying with the technology leaders. With this inside-out approach to technology learning East Asian entrepreneurs are reshaping the traditional technology development paradigm.
BUSINESS OWNERS'/MANAGERS' PERCEPTIONS OF THE INTERNET: AN AUSTRALIAN PERSPECTIVE
Authors: CALVERT CHERYL , O'CONNOR MIKE , BENTLEY JOHN
Published: November 2004

This paper details an Australian study, conducted by the Small Business Research Unit at Victoria University of Technology, of Internet usage by small business. The objectives of this study were to: explore the expectations of small businesses setting up webpages on the Internet; analyse the commercial impact of the Internet; determine any benefits from using the Internet; and to ascertain any problems associated with using the Internet. The methodology involved a questionnaire distributed either via electronic mail or the World Wide Web.

The main findings indicated that the average number of Internet sales inquiries per month appeared low compared to other countries such as the UK and USA. The majority of businesses received less than 20 sales inquiries per month via the Internet and only half of the respondent businesses indicated that sales had increased as a direct result of being on the Internet. Despite this, there existed optimism regarding business use of the Internet with the majority of business owners/managers claiming that the benefits of being on the Internet outweighed the costs, and that their expectations were met in using the Internet. Businesses involved in the computing industry had the highest level of optimism.