bluuebunny/crossref_metadata_2025 huggingface dataset:
ELECTRON–PHONON PAIRING IN THE HUBBARD MODEL
Authors: PLAKIDA N. M. , UDOVENKO V. S.
Published: November 2004

A system of electrons with strong correlations is considered within the framework of a single-band Hubbard model with a strong anharmonic electron-phonon interaction. The dependence of superconducting transition temperature T c on carrier concentration n is obtained using the Green function technique. It is shown that, due to the nonlocal character of electron–phonon coupling in the model, T c (n) strongly depends on the symmetry of the gap.
SYNTHESIS AND ELECTRICAL RESISTIVITY OF NICKEL POLYMETHACRYLATE
Authors: CHOHAN M. H. , KHALID A. H. , ZULFIQAR M. , BUTT P. K. , KHAN FARAH , HUSSAIN RIZWAN
Published: November 2004

Synthesis of nickel polymethacrylate was carried out using methanolic solutions of sodium hydroxide and polymethacrylic acid. The electrical resistivity of the pellets made from Ni-polymethacrylate was measured at different voltages and temperatures. Results showed that the electrical resistivity of Ni-polymethacrylate decreases significantly with voltage in high temperature regions but the decrease is insignificant at temperatures nearing room temperature. The activation energy at low temperatures is approximately 0.8 eV whereas at high temperature it is in the range 0.21–0.27 eV.
TRANSPORT CRITICAL CURRENT DENSITY IN FLUX CREEP MODEL
Authors: WANG J. , YUE Y. , TAYLOR K. N. R. , RUSSELL G. J. , DOU S. X.
Published: November 2004

The magnetic flux creep model has been used to derive the temperature dependence of the critical current density in high temperature superconductors. The generally positive curvature of the J c - T diagram is predicted in terms of two interdependent dimensionless fitting parameters. The results are compared with both SIS and SNS junction models of these granular materials, neither of which provides a satisfactory prediction of the experimental data. A hybrid model combining the flux creep and SNS mechanisms is shown to be able to account for the linear regions of the J c - T behaviour which are observed in some materials.
SUPERCONDUCTIVITY IN YBa2Cu3O7−δCOPPER OXIDE CERAMIC
Authors: SHARMA A.C. , KULSHRESTHA INA
Published: November 2004

A simple model calculation of Tc, based on the strong coupling theory of superconducti vity, has been performed for YBa2Cu3O7−δ, which is modelled to be a periodic array of conducting two-dimensional copper oxide planes embedded in a dielectric host. The pairing of charge carriers is assumed to take place via exchange of long wavelength bosons. To calculate Tc, we performed a simple model calculation of the carrier density of states (No), effective Coulomb interaction (μ*) and coupling parameter (λ). Our computed Tc as a function of δ is then compared with the experimental data.
FIELD ION MICROSCOPE STUDY OF HIGH-TEMPERATURE SUPERCONDUCTOR Nd1.85Ce0.15CuO4
Authors: TALANTSEV E. F. , IVCHENKO V. A. , KOZHEVNIKOV V. L. , FLIATAU E. E.
Published: November 2004

The field ion microscopy (FIM) technique has been used to investigate the atomic structure of a metal-oxide superconductor Nd 1.85 Ce 0.15 CuO 4. It is shown that predominantly copper atoms are imaged in the field ion micrographs. The study of the atomic structure in the bulk of the material by field evaporation of the superconductor surface atoms at cryogenic temperatures has shown that in the actual structure of Nd 1.85 Ce 0.15 CuO 4 a small number of O(2) sites are occupied by metal atoms (cerium or copper) with equal statistical probability.
MAGNETIC PROPERTIES OF SINTERED Nd-Fe-B TYPE MAGNETS CONTAINING CALCIUM, CHLORINE AND CARBON
Authors: SZYMURA S. , BALA H. , RABINOVICH YU. M. , WYSLOCKI J. J.
Published: November 2004

The microstructure and magnetic properties of Nd 16-x X x Fe 70.5 Co 5 AlB 7.5 and Nd 14-x Dy 2 X x Fe 71 Co 5 B 8 ( X = Ca , Cl and C ) magnets with various x were examined. In magnets after sintering and heat treatment carbon-rich areas were produced within the non-magnets Nd -rich phase. However chlorine-rich and calcium-rich areas were present in both non-magnetic Nd -rich and B -rich phases. The contribution of C ≤0.35 at%, Cl ≤0.013 at% and Ca ≤0.09 at% had no influence on the magnetic properties (B r and i H c ), but higher concentration of these elements caused decrease in these properties. Abnormal grain growth was found in magnets containing Cl .
BRINGING THE GRANDMOTHER BACK INTO THE PICTURE: A MEMORY-BASED VIEW OF OBJECT RECOGNITION
Authors: EDELMAN SHIMON , POGGIO TOMASO
Published: November 2004

We describe experiments with a versatile pictorial prototype-based learning scheme for 3-D object recognition. The Generalized Radial Basis Function (GRBF) scheme seems to be amenable to realization in biophysical hardware because the only kind of computation it involves can be effectively carried out by combining receptive fields. Furthermore, the scheme is computationally attractive because it brings together the old notion of a "grandmother" cell and the rigorous approximation methods of regularization and splines.
NEURAL NETWORKS FOR COLLECTIVE TRANSLATIONAL INVARIANT OBJECT RECOGNITION
Authors: CHAN LAI-WAN
Published: November 2004

A novel method using neural networks for translational invariant object recognition is described in this paper. The objective is to enable the recognition of objects in any shifted position when the objects are presented to the network in only one standard location during the training procedure. With the presence of multiple or overlapped objects in the scene, translational invariant object recognition is a very difficult task. Noise corruption of the image creates another difficulty.

In this paper, a novel approach is proposed to tackle this problem, using neural networks with the consideration of multiple objects and the presence of noise. This method utilizes the secondary responses activated by the backpropagation network. A confirmative network is used to obtain the object identification and location, based on these secondary responses. Experimental results were used to demonstrate the ability of this approach.
ON IMPROVING THE ACCURACY OF LINE EXTRACTION IN HOUGH SPACE
Authors: TONG FRANK , LI ZE-NIAN
Published: November 2004

This paper presents an accurate line extraction technique — the Hierarchical Peak Compaction Hough Transform (HPCHT). Vote scattering in the parameter space is a problem when the Hough transform is used for line extraction. This paper investigates the effects of image size and edge data errors on the severity of vote scattering. The HPCHT uses the Hough procedure on small subimages initially, and a recursive Hough merging scheme on the extracted line segments afterwards. A bound on vote scattering has been derived which guides the image subdivision and the adaptive quantization of the parameter space. As a result, an accurate Hough transform of low ρ-scattering and high θ-precision has been achieved. The HPCHT is suitable for fast parallel implementation on pyramid computers.
A PARALLEL ALGORITHM FOR SINGLE ROW ROUTING PROBLEMS
Authors: ROY ARNOB , DEOGUN JITENDER , SHERWANI NAVEED A.
Published: November 2004

Single Row Routing problem is one of the important subproblems in the layout design of multilayer printed circuit boards. This routing technique has also been applied to routing of microwave citcuits and other routing problems. The single row routing problem has been extensively studied and several sequential algorithms have been proposed.

In this paper, we present a parallel hypercube algorithm for the single row routing problem. The basis of this parallel algorithm is a new O(n2 log n) sequential algorithm based on the concept of modified cut numbers and a graph decomposition scheme. The sequential algorithm is based on generalizing the concepts underlying two existing sequential algorithms. A parallel algorithm for the hypercube architecture with N processors is then developed by combining the nice features of the sequential algorithm with an efficient allocation scheme. This results in a parallel algorithm of [Formula: see text] complexity. The experimental results show that our algorithm achieves a speed up factor that is quite close to the theoretical bound while maintaining the quality of the solutions, as compared to any existing sequential algorithm. Moreover, the algorithm produces 28% better results than any existing results.
SIMULATED ANNEALING AND TABU SEARCH ALGORITHMS FOR MULTIWAY GRAPH PARTITION
Authors: TAO L. , ZHAO Y.C. , THULASIRAMAN K. , SWAMY M.N.S.
Published: November 2004

For a given graph G with vertex and edge weights, we partition the vertices into subsets to minimize the total weights for edges crossing the subsets (weighted cut size) under the constraint that the vertex weights are evenly distributed among the subsets. We propose two new effective graph partition algorithms based on simulated annealing and tabu search, and compare their performance with that of the LPK algorithm reported in Ref. 12. Extensive experimental study shows that both of our new algorithms produce significantly better solutions than the LPK algorithm (maximal and minimal improvements on average weighted cut size are roughly 51.8% and 10.5% respectively) with longer running time, and this advantage in solution quality would not change even if we run the LPK algorithm repeatedly with random initial solutions in the same time frame as required by our algorithms.
LOW FREQUENCY FALSE-LOCK PHENOMENON IN SAMPLED COSTAS-LOOPS
Authors: PAP L.
Published: November 2004

The effect of the low frequency false-lock phenomenon has been considered in sampled decision feedback Costas-loops used in BPSK direct sequence spread spectrum (DS SS) systems. This new physical phenomenon can occur in each arm-filtered nonlinear sampled PLL applying digital signal processing algorithms for phase detector implementations. This contribution provides details of calculation of false-locking phase detector characteristics of the sampled Costas-loops without and with hard-limited in-phase channel (the latter system will be referred to as sampled decision feedback loop) and analyzes different methods of filterless subharmonic false-lock detection. Besides in the case of white Gaussian noisy environment the phase detector characteristics at the false-lock frequencies, and the false alarm and false detection probabilities of the filterless subharmonic false-lock detectors are derived based on the new circuit models. The theoretical results have been checked by experimental implementations.
THE DYNAMICS OF COUPLED CURRENT-BIASED JOSEPHSON JUNCTIONS — PART II
Authors: ARONSON D. G. , DOEDEL E. J. , OTHMER H. G.
Published: November 2004

A numerical analysis of the dynamics of two coupled current-biased Josephson junctions is presented. The mathematical model of two coupled nonlinear ordinary differential equations can also be interpreted in terms of coupled rotating pendula. We describe the solution manifolds of these equations, particularly the manifolds of rotations of phase gain 4π per period. A variety of homoclinic orbits and heteroclinic cycles is shown to exist when the coupling strength is small. We also discuss the relation between the solution structure of the damped system and the solution structure of the undamped system.
ez: DYNAMICS AND BIFURCATIONS
Authors: DEVANEY ROBERT L.
Published: November 2004

In this paper we describe some of the dynamical behavior of the complex exponential λ exp z. For various values of λ, this family exhibits chaotic behavior on the entire complex plane. For other values, the dynamics are relatively tame. We show how to analyze this behavior via symbolic dynamics and investigate the structural instability at various parameter values. Finally, we describe the relationship between the parameter space for the exponential family and the related families of polynomials given by [Formula: see text].
THE HAUSDORFF DIMENSION OF ATTRACTORS APPEARING BY SADDLE-NODE BIFURCATIONS
Authors: AFRAIMOVICH V. S. , SHERESHEVSKY M. A.
Published: November 2004

We consider the strange attractors which appear as a result of saddle-node vanishing bifurcations in two-dimensional, smooth dynamical systems. Some estimates and asymptotic formulas for the Hausdorff dimension of such attractors are obtained. The estimates demonstrate a dependence of the dimension growth rate after the bifurcation upon the "pre-bifurcational" picture.
"CROSSROAD AREA–SPRING AREA" TRANSITION (II) FOLIATED PARAMETRIC REPRESENTATION
Authors: MIRA C. , CARCASSÈS J. P. , BOSCH M. , SIMÓ C. , TATJER J. C.
Published: November 2004

The areas considered are related to two different configurations of fold and flip bifurcation curves of maps, centred at a cusp point of a fold curve. This paper is a continuation of an earlier one devoted to parameter plane representation. Now the transition is studied in a thee-dimensional representation by introducing a norm associated with fixed or periodic points. This gives rise to complete information on the map bifurcation structure.
AN OSCILLATOR WITH CUBIC AND PIECEWISE-LINEAR SPRINGS
Authors: KETEMA YOHANNES
Published: November 2004

A system consisting of a mass attached to a nonlinear spring with negative linear stiffness and cubic nonlinearity, (i.e., a spring obeying Duffing's equation with negative linear stiffness) and a linear spring at a certain offset distance is studied. Melnikov's method is applied to determine the existence of homoclinic points for the Poincare map, and preserved resonant orbits and boundaries for these are given in the parameter space. This system is then compared to the system consisting of only the nonlinear spring with regard to the existence of parameter regimes where chaotic motion is possible. It is shown that if the linear spring is of appropriate stiffness the chaotic motion for a given set of parameter values occurring for the system consisting of only the nonlinear spring is replaced by periodic motion and the mechanism of this phenomenon is explained.
BIFURCATION STRUCTURE OF A DRIVEN MULTI-LIMIT-CYCLE VAN DER POL OSCILLATOR (II): SYMMETRY-BREAKING CRISIS AND INTERMITTENCY
Authors: EICHWALD C. , KAISER F.
Published: November 2004

Bifurcations in the superharmonic region of a generalized version of the van der Pol oscillator which exhibits three limit cycles are investigated. An external force causes the subsequent breakdown of the self-sustained oscillations. Beyond these series of bifurcations chaotic solutions also exist. They display a symmetry-breaking crisis followed by a type III intermittency transition. The bifurcations are discussed with respect to the symmetry properties of chaotic attractors. The critical exponents connected with the bifurcations offer a scaling which partially contradicts that known from literature. An explanation for this behavior is given.
DYNAMICAL SYSTEMS AND TESSELATIONS: DETECTING DETERMINISM IN DATA
Authors: MEES ALISTAIR I.
Published: November 2004

Data measurements from a dynamical system may be used to build triangulations and tesselations which can — at least when the system has relatively low-dimensional attractors or invariant manifolds — give topological, geometric and dynamical information about the system. The data may consist of a time series, possibly reconstructed by embedding, or of several such series; transients can be put to good use. The topological information which can be found includes dimension and genus of a manifold containing the state space. Geometric information includes information about folds, branches and other chaos generators. Dynamical information is obtained by using the tesselation to construct a map with stated smoothness properties and having the same dynamics as the data; the resulting dynamical model may be tested in the way that any scientific theory may be tested, by making falsifiable predictions.
MIXING DISTRIBUTIONS PRODUCED BY MULTIPLICATIVE STRETCHING IN CHAOTIC FLOWS
Authors: MUZZIO F.J. , SWANSON P.D. , OTTINO J.M.
Published: November 2004

Chaotically advected fluids are both a visual demonstration of stretching and folding leading to chaos and a prototypical example of a multiplicative process with weakly correlated steps. Complementary aspects of the process are studied by means of stretching calculations for different flows under both globally and partially chaotic conditions. Stretching is examined in two different ways: (i) as stretching plots, focusing primarily on stretching at small scales and on the comparison of the spatial distribution of stretching with dye structures and with unstable manifolds, and (ii) as time evolving probability density functions, analyzed using scaling techniques that renormalize the distributions by means of their moments. The first approach leads to the conclusion that the manifold structure generates the striation pattern observed in dye deformation experiments, and that both manifolds and dye patterns agree with stretching plots even at small scales. The second approach demonstrates that the multiplicative nature of stretching generates universal statistics which are reflected in self-similar scaling distributions.
BIFURCATION PHENOMENA IN THE 1:1 RESONANT HORN FOR THE FORCED VAN DER POL—DUFFING EQUATION
Authors: DMITRIEV A.S. , KOMLEV U.A. , TURAEV D.V.
Published: November 2004

This paper presents the 1:1 resonant horn bifurcation phenomena for the forced van der Pol—Duffing equation. It is shown that the transition to chaos in the case of small dissipation evolves in two parallel processes: a sequence of period-doubling bifurcations and the birth, growth and merging of homoclinic structures.
DENSITIES AND DYNAMICS
Authors: NOAKES LYLE
Published: November 2004

Let M be a closed surface without boundary, possibly a sphere or a torus. A repetitive process determines a large number of points xn distributed more or less uniformly over M. We cannot observe these points, nor do we know what M is. There is a smooth function f:M→R (not given) and we measure the numbers yn≡f(xn). The problem is to say something about the geometry of M from the limited information that we have. We consider also a question concerning the existence of smooth densities of continuous random variables, and then the original problem reduces to a nonstandard problem in density estimation. This is by way of a mathematical result whose proof is given in Secs. 4, 5, and 6, but very little mathematical expertise is required to apply the method in practice. The method is described in Sec. 3 where we also give some examples.
DETERMINATION OF CRISIS PARAMETER VALUES BY DIRECT OBSERVATION OF MANIFOLD TANGENCIES
Authors: SOMMERER JOHN C. , GREBOGI CELSO
Published: November 2004

We discuss an algorithm to find the parameter value at which a nonlinear, dissipative, chaotic system undergoes crisis. The algorithm is based on the observation that, at crisis, the unstable manifold of an unstable periodic point becomes tangent to the stable manifold of the same or another, related unstable periodic point. This geometric algorithm uses much less computation (or data) than estimating the critical parameter value by using the scaling relation for chaotic transients, τ~(p−pc)−γ. We demonstrate the algorithm in both numerical and experimental contexts.
PROPAGATION FAILURE IN LINEAR ARRAYS OF CHUA’S CIRCUITS
Authors: PEREZ-MUNUZURI V. , PEREZ-VILLAR V. , CHUA L.O.
Published: November 2004

Traveling wave fronts are considered for a one-dimensional array of Chua’s circuits. For diffusion coefficients less than some nonzero critical value it has been observed numerically that the traveling fronts fail to propagate. Propagation failure is compared with similar phenomena occurring in pulse propagation in nerves, and in coupled continuously-stirred tank reactors.
SELF-OSCILLATIONS OF AN OPTICALLY BISTABLE ELEMENT WITH VERY BROAD HYSTERESIS IN A HYBRID RING CAVITY
Authors: GROHS J. , ZHOU F. , IßLER H. , KLINGSHIRN C.
Published: November 2004

We investigate thermally induced optical nonlinearity of a glass doped with semiconductor quantum dots. With the feedback of a Fabry-Perot resonator this glass shows dispersive optical bistability. The reflected light signal is coupled to a hybrid ring cavity with a round trip time much longer than that of the Fabry-Perot resonator and even longer than the thermal relaxation time of the glass. The self-oscillations occurring for certain input parameters are regular and the appearance of different modes as a function of the light intensity coupled to the resonator is observed. Due to the broad hysteresis and the high inclination of both branches of the bistable loop we observe large numbers of ascending and descending steps in the output intensity, i.e., long oscillation periods. A simple model of adiabatic simulations by an iterated map shows that the mode structure follows a Farey-tree construction.
PHASE TRANSITIONS IN THE HUMAN BRAIN: SPATIAL MODE DYNAMICS
Authors: FUCHS ARMIN , KELSO J.A. SCOTT , HAKEN HERMANN
Published: November 2004

Pattern formation and switching between self-organized states are often associated with instabilities in open, nonequilibrium systems. We describe an experiment which shows that systematically changing a control parameter induces qualitative changes in sensorimotor coordination and brain activity, as registered by a 37-SQUID (Superconducting Quantum Interference Device) array. Near the instability point, predicted features of nonequilibrium phase transitions (critical slowing down, fluctuation enhancement) are observed in both the psychophysical data and the brain signals obtained from single SQUID sensors. Further analysis reveals that activity from the entire array displays spatial patterns evolving in time. Such spatiotemporal patterns are characterized by the dynamics of only a few coherent spatial modes.
BIFURCATIONAL ANALYSIS OF BISTABLE SYSTEM EXCITED BY COLORED NOISE
Authors: ANISHCHENKO V.S. , NEIMAN A.B.
Published: November 2004

The appearance of a hole in the two-dimensional probability density of a bistable system excited by colored noise is investigated. To analyze the phenomenon, a cumulant analysis is used. In the Gaussian approximation, it was shown that the hole formation corresponded to the bifurcation “saddle-node-repeller” of the state of equilibrium in the system of cumulant equations.
PREDICTION OF CHAOTIC TIME SERIES WITH NEURAL NETWORKS AND THE ISSUE OF DYNAMIC MODELING
Authors: PRINCIPE JOSE C. , RATHIE ALOK , KUO JYH-MING
Published: November 2004

This paper deals with the role of neural-network based prediction for the modeling of nonlinear dynamical systems. We show experimentally that the backpropagation learning rule to train neural networks and the prediction error, so widely utilized in teaching and comparing nonlinear predictors, do not consistently indicate that the neural network based model has indeed captured the dynamics of the system that produced the time series. Frequently, but not always, the neural network when used as an autonomous system in a feedback configuration was able to generate a time series that has dynamical invariants similar to the original time series. We show that the estimation of the dynamical invariants (correlation dimension, largest Lyapunov exponent) of the predicted and original time series are an appropriate tool to validate the predictive model.
MUTUAL SYNCHRONIZATION OF CHAOTIC SELF-OSCILLATORS WITH DISSIPATIVE COUPLING
Authors: RUL'KOV N. F. , VOLKOSKII A. R. , RODRÍGUEZ-LOZANO A. , DEL RÍO E. , VELARDE M. G.
Published: November 2004

In a case of two dissipative coupled electronic circuits with possible chaotic dynamics, results of experimental, analytical and computer studies are provided concerning bifurcations on the boundaries of the synchronization regime of chaotic self-oscillations.
TEXPROS: AN INTELLIGENT DOCUMENT PROCESSING SYSTEM
Authors: WANG JASON T. L. , NG PETER A.
Published: November 2004

This paper presents the design of an intelligent document processing system, called TEXPROS. The system is a combination of filing and retrieval systems, which supports storing, extracting, classifying, categorizing, retrieving and browsing information from a variety of documents. TEXPROS is built based on object-oriented programming and rule-based specification techniques. In this paper, we describe main design goals of the system, its data model, logical file structure, and strategies for document classification and categorization. We also illustrate various retrieval methods and query processing techniques through examples. Finally applications of TEXPROS are presented, where we suggest ways in which the use of the system may alter the software process model.
EXPERT SYSTEMS IMPLEMENTATION: RULES ARE BAD, OBJECTS ARE GOOD
Authors: LI XIAOFENG
Published: November 2004

This paper summarizes the author's four-year research on examining rule-based programming (RBP) and object-oriented programming (OOP) for expert systems implementation. It reaches two conclusions. First, with a few exceptions, RBP is simply not working in practice. Second, many rule-based problems can be solved with OOP with improved system understandability and maintainability. This paper aims at (1) clarifying some of the confusion surrounding expert systems technology, and (2) providing a practical direction for expert systems implementation.
ON GOOD TRIANGULATIONS IN THREE DIMENSIONS
Authors: DEY TAMAL KRISHNA , BAJAJ CHANDERJIT L. , SUGIHARA KOKICHI
Published: November 2004

In this paper, we give an algorithm that triangulates the convex hull of a three dimensional point set with guaranteed quality tetrahedra. Good triangulations of convex polyhedra are a special case of this problem. We also give a bound on the number of additional points used to achieve these guarantees and report on the techniques we use to produce a robust implementation of this algorithm under finite precision arithmetic.
A PARALLEL ALGORITHM FOR ENCLOSED AND ENCLOSING TRIANGLES
Authors: CHANDRAN SHARAT , MOUNT DAVID M.
Published: November 2004

We consider the problems of computing the largest area triangle enclosed within a given n-sided convex polygon and the smallest area triangle which encloses a given convex polygon. We show that these problems are closely related by presenting a single sequential linear time algorithm which essentially solves both problems simultaneously. We also present a cost-optimal parallel algorithm that solves both of these problems in O( log log n) time using n/ log log n processors on a CRCW PRAM. In order to achieve these bounds we develop new techniques for the design of parallel algorithms for computational problems involving the rotating calipers method.
THE TWO GUARDS PROBLEM
Authors: ICKING CHRISTIAN , KLEIN ROLF
Published: November 2004

Given a simple polygon in the plane with two distinguished vertices, s and g, is it possible for two guards to simultaneously walk along the two boundary chains from s to g in such a way that they are always mutually visible? We decide this question in time O (n log n) and in linear space, where n is the number of edges of the polygon. Moreover, we compute a walk of minimum length within time O(n log n+k), where k is the size of the output, and we prove that this is optimal.
NEAREST NEIGHBOR PROBLEMS
Authors: WILFONG GORDON
Published: November 2004

Suppose E is a set of labeled points (examples) in some metric space. A subset C of E is said to be a consistent subset ofE if it has the property that for any example e∈E, the label of the closest example in C to e is the same as the label of e. We consider the problem of computing a minimum cardinality consistent subset. Consistent subsets have applications in pattern classification schemes that are based on the nearest neighbor rule. The idea is to replace the training set of examples with as small a consistent subset as possible so as to improve the efficiency of the system while not significantly affecting its accuracy.

The problem of finding a minimum size consistent subset of a set of examples is shown to be NP-complete. A special case is described and is shown to be equivalent to an optimal disc cover problem. A polynomial time algorithm for this optimal disc cover problem is then given.
SYNCHRONIZATION AND DECOMPOSABILITY FOR A FAMILY OF CODES
Authors: BRUYÈRE VÉRONIQUE , DE FELICE CLELIA
Published: November 2004

In the framework of two Schützenberger’s conjectures on codes, we characterize the degree of finite maximal codes over the alphabet {a, b} with at most 3 occurrences of the letter b in each word; it is strongly related to the number of factorizations of the code. We also describe all the indecomposable codes inside this family.
EQUIVALENT AUTOMATIC STRUCTURES AND THEIR BOUNDARIES
Authors: NEUMANN WALTER D. , SHAPIRO MICHAEL
Published: November 2004

Two (synchronous, asynchronous, or non-deterministic asynchronous) automatic structures on a group G are “equivalent” if their union is a non-deterministic asynchronous automatic structure. We discuss this relation, giving a classification of structures up to equivalence for abelian groups and partial results in some other cases. We also discuss a “boundary” of an asynchronous automatic structure. We show that it is an invariant of the equivalence class of the structure, and describe other properties. We describe a “rehabilitated boundary” which yields Sn−1 for any automatic structure on ℤn.
APPLICATIONS OF SUBMILLIMETER WAVEGUIDE TO LASER-MODE SELECTION AND NONLINEAR OPTICS
Authors: ZHOU J.Y. , LI Q.X. , WANG H.Z. , CAI Z.G. , HUANG X.G. , YU Z.X.
Published: November 2004

Use of submillimeter waveguide for laser transverse mode control, four-wave parametric frequency conversion, ultrafast broadband radiation generation and optical pulse shortening are presented. This paper begins with a general introduction to the applications of submillimeter waveguide to laser physics and nonlinear optics. Transverse mode selection by using an intracavity capillary is then described. Nonlinear optical frequency conversion in gas-filled hollow dielectric and hollow metallic waveguide structures is discussed. Applications of submillimeter liquid-core fiber to stimulated scattering, ultrafast broadband radiation generation and optical pulse shortening are presented, and transient stimulated Rayleigh-Kerr scattering is proposed to explain the observations of these nonlinear optical processes. It is shown that the unique characterization of high usable pump power and high power emission of submillimeter waveguides makes the waveguide structures ideal for high-power, high-energy laser physics and nonlinear optics.
PHOTOREFRACTIVE TECHNIQUES FOR DIODE LASER BEAM COMBINATION
Authors: MacCORMACK STUART , EASON ROBERT W.
Published: November 2004

Techniques for high-power laser array beam combination processes involving photo-refractive materials are reviewed. Details of an all semiconductor laser scheme for the amplification and subsequent photorefractive beam clean-up of a diffraction limited single-mode laser output is presented. Powers in excess of 100 mW (>220 mW accounting for Fresnel losses) are obtained in a diffraction limited signal beam, corresponding to an array to diffraction limited beam transfer efficiency of 33%. Details of a reflection geometry phase conjugate master oscillator-power amplifier scheme which offers the possibility of power scaling between a number of high-power semiconductor laser amplifiers are presented. Using this technique, a 13-dB amplification of a diffraction limited signal beam is obtained using a commercially available, 10-stripe gain-guided device with no special coatings.
RUNAWAY PARTICLES FOR A BOLTZMANN-LIKE TRANSPORT EQUATION
Authors: ARLOTTI LUISA , FROSALI GIOVANNI
Published: November 2004

In this paper we consider the linear Boltzmann equation which describes the evolution of one species of charged particles, electrons or ions, in a single component neutral gas. Collisions among charged particles are neglected and the acceleration field is dependent on time. We investigate a necessary condition on the behavior of both collision frequency and acceleration field so that the time-dependent solution relaxes towards a steady-state. Under suitable conditions on the acceleration field, an asymptotic behavior similar to a travelling wave in velocity space is pointed out. Various examples with different behaviors of the acceleration field for large times are given, in the simple context of the BGK model.
VISUALIZING LEARNING AND COMPUTATION IN ARTIFICIAL NEURAL NETWORKS
Authors: CRAVEN MARK W. , SHAVLIK JUDE W.
Published: November 2004

Scientific visualization is the process of using graphical images to form succinct and lucid representations of numerical data. Visualization has proven to be a useful method for understanding both learning and computation in artificial neural networks. While providing a powerful and general technique for inductive learning, artificial neural networks are difficult to comprehend because they form representations that are encoded by a large number of real-valued parameters. By viewing these parameters pictorially, a better understanding can be gained of how a network maps inputs into outputs. In this article, we survey a number of visualization techniques for understanding the learning and decision-making processes of neural networks. We also describe our work in knowledge-based neural networks and the visualization techniques we have used to understand these networks. In a knowledge-based neural network, the topology and initial weight values of the network are determined by an approximately-correct set of inference rules. Knowledge-based networks are easier to interpret than conventional networks because of the synergy between visualization methods and the relation of the networks to symbolic rules.
A DISTRIBUTED PROBLEM-SOLVING INFRASTRUCTURE FOR COMPUTER NETWORK MANAGEMENT
Authors: SO YOUNG-PA , DURFEE EDMUND H.
Published: November 2004

A distributed computer network management system consisting of cooperating autonomous computing agents allows network management to be more responsive due to information gathering and network recovery activities being performed in parallel. However, to perform these tasks, the network of agents requires a stable organizational infrastructure. In addition, to meet the needs of human network administrators, the distributed system must allow ultimate authority to be centralized at a single location. Distributed Big Brother (DBB) represents a pragmatic blending of diverse technologies from the field of distributed AI, such as contract formation, organizational structuring, election for role assignment, and hierarchical control. The result is an infrastructure for a network management system in which separate agents reconfigure themselves when hardware and software failures occur in order to assure the authority structure demanded by network operators. Our efforts illustrate how integrating existing distributed AI technologies can meet realistic needs, and highlight open problems that require the development of new technologies.
COMPOSITE KNOTS TRIVIALIZED BY TWISTING
Authors: TERAGAITO MASAKAZU
Published: November 2004

Some composite knots are known to be trivialized by twisting. However, the bridge index of the prime factors in known examples is two. In this note, for any integer n ≥ 1 we will construct composite knots which can be trivialized by twisting and which consist of two prime factors with bridge index greater than n.
THE ASHTEKAR FORMULATION FOR CANONICAL N=2 SUPERGRAVITY
Authors: KUNITOMO HIROSHI , SANO TAKASHI
Published: November 2004

Ashtekar’s formulation of canonical gravity is extended to N=2 supergravity. The action has a complex first-order chiral form and is invariant under two local supersymmetry transformations. Since we adopt the chiral formulation, left- and right-handed supersymmetries appear in an asymmetric way. The supersymmetry algebra is not closed on auxiliary fields, which is a peculiar result of the chiral formulation, where the right-handed supersymmetries are realized by constrained parameters. By means of the canonical formalism, simple polynomial constraints are derived and we can show that the Poisson brackets of supersymmetry currents are actually closed. This guarantees the consistency of our supersymmetry transformations, which is unclear at the level of the algebra on the fields.
PERTURBATIVE ANALYSIS OF TWO-DIMENSIONAL QUANTUM GRAVITY: RENORMALIZATION, GAUGE DEPENDENCE AND FINITENESS
Authors: ODINTSOV S.D. , SHAPIRO I.L.
Published: November 2004

We develop the perturbative analysis of two-dimensional quantum gravity with local action. The general renormalization structure of the theory is discussed. The one-loop divergences of the effective action in the covariant gauge of the general type are found. The technique for the calculation of the one-loop divergences for nonminimal operators in two dimensions is presented. The gauge dependence of the counterterms is discussed. It is also presumed that there are no one-loop divergences in some particular covariant gauge (finiteness.)

The renormalization group analysis is given. The addition of the cosmological constant and Liouville type term is considered.
RELATIVISTIC CHARGED PARTICLE SCATTERING WITH SPIN SPIN INTERACTIONS
Authors: DAREWYCH JURIJ W. , HORBATSCH MARKO , KONIUK ROMAN
Published: November 2004

We consider scattering solutions to relativistic wave equations derived within the framework of a Hamiltonian variational method for Quantum Electrodynamics. The wave equations contain the spin-dependent Breit interaction terms as the Fock-space Ansatz samples the transverse photon degrees of freedom. For the case of uncharged scalar particles exchanging massive bosons (scalar Yukawa model) reasonable agreement with a solution of the Bethe–Salpeter equation in ladder approximation is obtained. For the case of the pseudoscalar and scalar channels in QED, we determine the phase shifts as a function of energy.
A NEW LARGE AMPLITUDE COLLECTIVE MOTION IN NUCLEI: CLUSTERS AS SOLITONS ON THE NUCLEAR SURFACE
Authors: LUDU A. , SĂNDULESCU A. , GREINER W.
Published: November 2004

Based on the liquid drop model, by including nonlinear terms in the hydrodynamic equations, we show that stable solitons can exist on the nuclear surface of 208 Pb or dose to it, this being the most rigid double magic spherical nucleus. The shell effects related with this nucleus lead to a new minimum in the total potential energy. In order to connect this minimum with the cluster decays, which are spontaneous decays, we choose the corresponding energy to be degenerate with the ground state minimum. A new coexistence model consisting of the usual shell model and a cluster-like model describing a soliton moving on the nuclear surface is obtained. The corresponding amplitudes describe excellently the experimental spectroscopic factors for cluster decays.
PRODUCTION OF HEAVY ELEMENTS BY TRANSFER OF MASSIVE CLUSTERS
Authors: MAGDA M. T. , LEYBA J. D.
Published: November 2004

A review of various models of multinucleon transfer reactions leading to heavy elements is given. A mechanism is proposed to describe these reactions based on the assumption that massive clusters are separated from the projectile and captured as a whole by the target nucleus. The modification of the primary isotopic distribution by fission and neutron evaporation is considered. Calculated isotopic distributions and cross sections are in good agreement with experimental data for the production of Z = 96–103 elements. Predictions of the model are used to explore the possibilities of producing transfermium elements by transfer reactions.
MEASUREMENT AND ANALYSIS OF EXCITATION FUNCTIONS FOR ALPHA-INDUCED REACTIONS IN BISMUTH
Authors: SINGH B. P. , SANKARACHARYULU M. G. V. , ANSARI M. A. , PRASAD R. , BHARDWAJ H. D.
Published: November 2004

Excitation functions for 209 Bi (α, 3n), 209 Bi (α, 4n) and 209 Bi (α, 5n) reactions have been measured in the energy range threshold to ≈50 MeV using stacked foil technique. Excitation functions have also been theoretically calculated and as expected, inclusion of pre-equilibrium contribution based on exciton model calculations along with compound nucleus calculations using Hauser–Feshbach formalism reproduces well the measured excitation functions. Interesting trend in the ratio of pre-equilibrium to equilibrium component with projectile energy has been observed.
A MODEL OF THE ENTREPRENEURIAL OPPORTUNITY RECOGNITION PROCESS
Authors: ARDICHVILI ALEXANDER , CARDOZO RICHARD N.
Published: November 2004

The goal of this study is to propose a model of the entrepreneurial opportunity recognition process. A number of research propositions was generated based on the analysis of the available literature, and then validated by the analysis of in-depth cases of opportunity recognition that resulted in the creation of successful entrepreneurial ventures. The study indicates that entrepreneurial opportunities are discovered through recognition rather than purposeful search; prerequisites for successful opportunity discovery are a combination of entrepreneurial awareness, access to extended social networks, and prior knowledge of markets and customer problems; prior knowledge could exist due to work experience, personal, non-work related experiences and events, or due to relevant to these markets education. Further, opportunity recognition does not require an exceptional level of creativity, and is not likely to involve a prior knowledge of the ways to serve markets.
CREATING AN INTERNATIONAL HIGH TECHNOLOGY INCUBATOR: THE CASE OF THE UCLA VENTURE DEVELOPMENT PROGRAM
Authors: CARSRUD ALAN L. , SVENSON ELWIN , GILBERT LLOYD
Published: November 2004

This paper describes the development and growth of a virtual, internationally based, high technology business incubator in Australia, Chile, Finland and the United States. The UCLA Venture Development Program (UCLA-VDP) is a global educational program and "knowledge network" of strategic partners. The UCLA-VDP serves as the technology business incubator at UCLA and operates internationally through its Global Access Program (GAP) utilizing its strategic partnerships with business and technology groups abroad. The objective of the Program is to create new businesses and wealth out of the technological research conducted at UCLA, other universities, and laboratories world-wide using the entrepreneurial talents and networks of the Anderson School at UCLA.
THE IMPACT OF NATIONAL, CORPORATE AND PROFESSIONAL CULTURES ON INNOVATION: GERMAN AND DUTCH FIRMS COMPARED
Authors: ULIJN JAN , NAGEL ARIE , TAN WEE LIANG
Published: November 2004

Innovation literature advocates the transition from a technological orientation to market orientation on the part of innovator and entrepreneur. However, the transition requires a change in mindset on the part of these innovation agents, who may be affected by their national contexts. This paper reports a study is to example factors that account for a different transition from a Technological Orientation (TO) towards a Market Orientation (MO) and the impact of national cultures. To analyse possible intercultural differences, the study involved two independent samples from Germany and the Netherlands.

The study found that the orientation to versus MO of the Dutch engineer is not different from that of the German engineer, probably because of a common professional culture (PC), which is different from an MO. The transition from technological orientation towards market orientation occurred earlier for the Dutch engineers than for the German engineers. However German engineers demonstrated less MO than Dutch firms. A plausible reason for this is that the strong feminine values of Dutch national and corporate culture (NC and CC, Hofstede, 1980a and b and 1991) might lead more easily to a customer orientation (Market Pull) than the more masculine German values keeping a strong technological base. In sum, firms might consider carefully an optimal CC x PC interaction instead of NC-differences to reach effective technological innovation in the global market.
DOES THE SILICON VALLEY CONCEPT WORK IN THE CZECH REPUBLIC? POSSIBLE CULTURE REASONS FOR INNOVATION SUCCESS
Authors: PIVODA MIROSLAV
Published: November 2004

The case of an innovative Czech software company provoked broader research about the pro-innovative environment in a post-communist country. Creative potential and a drive for wealth are present in the nation as well as a few negative factors influencing the current business environment. Necessary changes have already been undertaken from the governmental level to upgrade the National, Corporate and Professional cultures and to foster innovation. However, a bottom-up initiative may be decisive for any future business success. Historical as well as current positive business cases may serve as useful role models.
A NORMATIVE FRAMEWORK FOR ENTREPRENEURSHIP AND INNOVATION IN HONG KONG TOURISM
Authors: GO FRANK M. , CHAN ANDREW
Published: November 2004

This study relates that the 'business-as-usual' scenario has come to an end and questions the general practice of the present ethnocentric-led institutional tourism development in the Far East within an analytical framework.

It asserts that global cities play a crucial role in the systematic search for innovation and its diffusion, amongst others, through the regionalization of the metropolitan economies in an hierarchy of central places. The study focuses on Hong Kong, which has the potential to perform the function of "incubator" for innovation and its transfer throughout the region.

However, the results indicate that whilst tourism organizations in Hong Kong are engaged in some type of innovation, they do not apply systematic processes to advance innovation. Furthermore, the results also reveal that local service enterprises are less inclined to develop new service offerings in overseas markets than international enterprises.
ENTREPRENEURIAL ORGANIZATIONS: WHAT THEY ARE, WHY THEY ARE IMPORTANT AND HOW TO BECOME ONE
Authors: CHURCHILL NEIL C. , DE KONING ALICE J. , MUZYKA DANIEL F.
Published: November 2004

Most enterprises in the developed, and developing world, are facing frequent, irregular and significant changes in their environment, which shorten the life span of both present products and future opportunities and increase the unpredictability of their nature. The enterprises which seem best able to deal with these changes are those that focus on opportunity recognition and capture. In other words, those that engage in the entrepreneurial process. This paper is based on an ongoing research study into entrepreneurial companies in America and Europe of different sizes and in different stages of development, from small (Martin Aviation, Controlonics, and D. L. Martin) to medium size (Mettler-Toledo and MHZ) and large (Johnson and Johnson, 3M, Rhone-Poulenc, and DEC). In this research we have observed common patterns of opportunity, focus and capture at all levels of the organization as well as the mechanisms which are needed to maintain direction and control of the organization as the company increases in scale and diversity in order to harvest broader and increased amounts of value. This paper describes both these characteristics and what is needed to transform a more traditional organization into an entrepreneurial one.
STRATEGIC AWARENESS AND THE PROCESS OF INNOVATION
Authors: ATHERTON ANDREW , HANNON PAUL
Published: November 2004

Inherent to enterprising behaviour is the exercise of strategic awareness, a process of understanding and learning from the environment in which the entrepreneur and the small business operate. This paper notes that a growing recognition of high levels of change and uncertainty in the environment infers a need to increase small business understanding of what is changing and why. Strategic awareness is an individual and organisational capability, tailored to contextual needs and contingencies, that describes processes for identifying, understanding, interpreting and acting on events and influences. It also contributes to the process of innovation. Research in the UK, and later in Western Australia, identified a customer needs-focused and outwardly-directed approach to innovation that relies on understanding the external environment. This paper concludes by stressing the relationship between strategic awareness and innovation, and suggests that the nature of these processes demands a rethink in how we support and research small businesses and entrepreneurs.