bluuebunny/crossref_metadata_2025 huggingface dataset:
SIMULTANEOUS DETERMINATIONS OF TRACE ELEMENTS IN SERA OF PATIENTS WITH ACUTE MYOCARDIAL INFARCTION BY PIXE
Authors: MIURA Y. , ITOH C. , MIYAKAWA T. , NAKAI K. , HIRAMORI K. , SERA K. , FUTATSUGAWA S.
Published: November 2004

Using PIXE we determined concentrations of iron, nickel, copper, zinc, selenium, and rubidium in sera of 24 patients with acute myocardial infarction and 12 healthy controls. Rubidium*, selenium*, zinc**, nickel** and iron** concentrations are significantly (P<0.001*, P<0.01**) lower for patients than for control subjects. No significant difference is observed in the copper content. However, there is a slight increase in copper content in the patients so that the ratios Cu/Rb, Cu/Se, Cu/Zn, Cu/Ni, Cu/Fe are significantly higher for the patients than for the control subjects (P<0.01).
THE 267 MHz HIGH POWER CW KLYSTRODE® AMPLIFIER
Authors: SHRADER M. B. , PREIST D. H. , TORNOE R. N.
Published: November 2004

A 250 kW CW 267 MHz Klystrode has been designed and built as part of a major program in conjunction with the Chalk River National Labs., Chalk River, Ontario, Canada. The high CW power design has evolved from previous work for UHF television and the SDI program. A major step was taken on this program to simplify and reduce the complexity of the RF input circuit. CW power in excess of 250kW and efficiencies in excess of 70% were readily obtained with power gain in excess of 21 dB. Three tubes and associated circuitry were tested and delivered as part of the effort.
THE UBITRON REVISITED
Authors: PHILLIPS ROBERT M.
Published: November 2004

Whatever became of the ubitron? Old timers in the microwave tube field remember it vaguely as the original fast wave, super power amplifier. Cloaked in military secrecy, it surfaced from time to time with new records for frequency and power, only to drop from sight in the early 1960's. The author, who was the inventor and developer of the ubitron, relates the story of its rise and fall, and its relationship to its now famous and successful descendent, the free electron laser.
ENTROPY OF SOME INNER AUTOMORPHISMS OF THE HYPERFINITE II1-FACTOR
Authors: STØRMER ERLING
Published: November 2004

It is shown that the entropy of an inner automorphism Ad u of the hyperfinite II1-factor is zero if the unitary operator u belongs to a Cartan subalgebra.
NIRENBERG'S PROBLEM ON THE 2-DIMENSIONAL HEMI-SPHERE
Authors: LIU JIA-QUAN , LI PING-LI
Published: November 2004

In this paper, Morse theory under general boundary conditions is used to study the Nirenberg's problem on hemi-sphere [Formula: see text]: Given a smooth function K on hemi-sphere [Formula: see text], with the standard metric, whether a conformal metric can be found, so that the Gaussian curvature equals to K and the boundary is again a geodesic curve.

It turns out that if deg (Ω, ∂θK, 0) ≠ 1, where [Formula: see text], ∂nK is the exterior normal derivative and ∂θK is the tangential derivative, then the Nirenberg's problem has a solution.
KERNEL CONTROL OF COMPLEX LANGEVIN SIMULATION
Authors: SCHÜLKE LOTHAR , ZHENG BO
Published: November 2004

Kernel control of the complex Langevin simulation is discussed in detail in a simple model with one degree of freedom. Some comments are made on the so-called segregation phenomenon. We report about results obtained in close collaboration with K. Okano (Univ. of Tokuyama).
SOLITON ANTISOLITON SCATTERING IN (2+1) DIMENSIONS
Authors: PIETTE BERNARD , SUTCLIFFE PAUL M. , ZAKRZEWSKI WOJCIECH J.
Published: November 2004

We consider the scattering of solitons and antisolitons in a class of models in (2+1) dimensions. We point out that although in general the interaction forces between solitons and antisolitons are attractive, in some σ models they depend on the relative orientation between the solitons and antisolitons in their internal space. We discuss the scattering properties of such solitons and antisolitons.
THE ELECTROWEAK PHASE TRANSITION
Authors: GLEISER MARCELO , KOLB EDWARD W.
Published: November 2004

The phase transition associated with the standard electroweak model is very weakly first order. The weakness of the transition means that around the critical temperature the finite-temperature Higgs mass is much less than the critical temperature. This leads to infrared problems in the calculation of the parameters of the potential. Therefore, theories of electroweak baryogenesis, which depend on the details of the transition, must be calculated with care.
A NOTE ON INTERFACES WITH PERIODIC BOUNDARIES
Authors: BUNK B.
Published: November 2004

The partition funtion of a fluctuating interface is argued to approach a universal form at large area, including the numerical coefficient, provided that the interface has periodic boundary conditions und continuum behavior. This is demonstrated by explicit calculations, using effective actions with different regularisations. The result is applied to an analysis of the vortex free energy in SU(2) lattice gauge theory.
THE SPECTRUM OF THE $\mathcal{T}$-MATRIX AND THE SURFACE TENSION IN THE SU(3) GAUGE THEORY
Authors: TRAPPENBERG T.
Published: November 2004

The transfer matrix method to describe finite size effects due to tunneling are worked out for Z(2)- and Z(3)-symmetric models. We used this method to extract the surface tension σ in the SU(3) gauge theory at the finite temperature phase transition on lattices with an extent T=2 in the euclidean time direction. We also discuss if the confined phase completely wets the deconfined phase at this first order phase transition.
DAPHNE: DATA PARALLELISM NEURAL NETWORK SIMULATOR
Authors: FRASCONI PAOLO , GORI MARCO , SODA GIOVANNI
Published: November 2004

In this paper we describe the guideline of Daphne, a parallel simulator for supervised recurrent neural networks trained by Backpropagation through time. The simulator has a modular structure, based on a parallel training kernel running on the CM-2 Connection Machine. The training kernel is written in CM Fortran in order to exploit some advantages of the slicewise execution model. The other modules are written in serial C code. They are used for designing and testing the network, and for interfacing with the training data. A dedicated language is available for defining the network architecture, which allows the use of linked modules.

The implementation of the learning procedures is based on training example parallelism. This dimension of parallelism has been found to be effective for learning static patterns using feedforward networks. We extend training example parallelism for learning sequences with full recurrent networks. Daphne is mainly conceived for applications in the field of Automatic Speech Recognition, though it can also serve for simulating feedforward networks.
STEADY STATES IN NONEQUILIBRIUM LATTICE SYSTEMS
Authors: MARRO J.
Published: November 2004

Nonequilibrium Ising-like systems may be implemented efficiently in the computer. They may represent some natural situations, and may be relevant towards the development of theory. Three models in which either driving dissipative fields or competing kinetics impede the condition of detailed balance are described, and some related Monte Carlo results are reviewed. The models exhibit rich and interesting novel behavior.
A REVIEW OF THE LATTICE BOLTZMANN METHOD
Authors: SUCCI S. , BENZI R. , MASSAIOLI F.
Published: November 2004

In this paper, the basic elements of the theory of the Lattice Boltzmann equation are reviewed. Representative applications, such as turbulent flows and low-Reynolds flows in porous media are presented, along with a qualitative discussion on the most recent advances of this recent tool for computational fluid dynamics.
ON THE EFFICIENT SUMMATION OF N NUMBERS ON AN N-PROCESSOR RECONFIGURABLE MESH
Authors: FRAGOPOULOU PARASKEVI
Published: November 2004

A reconfigurable mesh is a two-dimensional processor array equipped with a reconfigurable bus system that can be changed dynamically to suit different computational needs. In this paper we present a parallel algorithm for the summation of N numbers each in the range [0, 2b). The algorithm runs in O(b+ log log N) time on [Formula: see text] reconfigurable mesh. This is an improvement over the best previously known algorithm that solves the same problem in O(b log log N) time. The algorithm is finally extended to compute the prefix sums of the given numbers in the same time.
TIME LOWER BOUNDS FOR PERMUTATION ROUTING ON MULTI-DIMENSIONAL BUSED MESHES
Authors: CHEUNG STEVEN , LAU FRANCIS C.M.
Published: November 2004

We present time lower bounds for the permutation routing problem on three- and higher-dimensional n x…x n meshes with buses. We prove an (r–1)n/r lower bound for the general case of an r-dimensional bused mesh, r≥2, which is not as strong for low-dimensional as for higher-dimensional cases. We then use a different approach to construct a 0.705n lower bound for the three-dimensional case.
SELF-REPAIRING NETWORKS
Authors: FARLEY ARTHUR M. , PROSKUROWSKI ANDRZEJ
Published: November 2004

In this paper, we provide a specification for a class of communication networks that are immune to single site failures, not only maintaining the ability to transfer messages between operable sites but doing so with no additional delay (i.e. no increase in length of communication path). We call these networks self-repairing and refer to their underlying topologies as self-repairing graphs. Our specification includes a constructive characterization of a class of minimal self-repairing graphs and an algorithmic determination of associated routing tables that can be used by a simple message transfer procedure to realize the desired immune behavior.
THE MINIMAL LENGTH AND LARGE EXTRA DIMENSIONS
Authors: HOSSENFELDER SABINE
Published: November 2004

Planck scale physics represents a future challenge, located between particle physics and general relativity. The Planck scale marks a threshold beyond which the old description of spacetime breaks down and conceptually new phenomena must appear. Little is known about the fundamental theory valid at Planckian energies, except that it necessarily seems to imply the occurrence of a minimal length scale, providing a natural ultraviolet cutoff and a limit to the possible resolution of spacetime.

Motivated by String Theory, the models of large extra dimensions lower the Planck scale to values soon accessible. These models predict a vast number of quantum gravity effects at the lowered Planck scale, among them the production of TeV-mass black holes and gravitons. Within the extra dimensional scenario, the minimal length also comes into the reach of experiment and sets a fundamental limit to short distance physics.

We review the status of Planck scale physics in these effective models.
A HADRON–QUARK VERTEX FUNCTION: INTERCONNECTION BETWEEN 3D AND 4D WAVE FUNCTIONS
Authors: MITRA A. N. , BHATNAGAR S.
Published: November 2004

The interrelation between the 4D and 3D forms of the Bethe–Salpeter equation (BSE) with a kernel [Formula: see text] which depends on the relative four-momenta, [Formula: see text] orthogonal to Pμ is exploited to obtain a hadron–quark vertex function of the Lorentz-invariant form [Formula: see text]. The denominator function [Formula: see text] is universal and controls the 3D BSE, which provides the mass spectra with the eigenfunctions [Formula: see text]. The vertex function, directly related to the 4D wave function Ψ which satisfies a corresponding BSE, defines a natural off-shell extension over the whole of four-momentum space, and provides the basis for the evaluation of transition amplitudes via appropriate quark-loop digrams. The key role of the quantity [Formula: see text] in this formalism is clarified in relation to earlier approaches, in which the applications of this quantity had mostly been limited to the mass shell (q · P = 0). Two applications (fP values for [Formula: see text] and Fπ for π0 → γγ) are sketched as illustrations of this formalism, and attention is drawn to the problem of complex amplitudes for bigger quark loops with more hadrons, together with the role of the [Formula: see text] function in overcoming this problem.
INTEGRABLE LATTICE MODELS, GRAPHS AND MODULAR INVARIANT CONFORMAL FIELD THEORIES
Authors: DI FRANCESCO P.
Published: November 2004

We review the construction of integrable height models attached to graphs, in connection with compact Lie groups. The continuum limit of these models yields conformally invariant field theories. A direct relation between graphs and (Kac–Moody or coset) modular invariants is proposed.
SECOND QUANTIZATION OF THE ANTISYMMETRIC POTENTIAL IN THE SPACE OF ABELIAN SURFACES
Authors: ARIAS PÍO J. , DI BARTOLO CAYETANO , FUSTERO XAVIER , GAMBINI RODOLFO , TRIAS ANTONI
Published: November 2004

We use the group of Abelian surfaces to develop a gauge-independent quantization for the two-index antisymmetric potential. An exact solution is found for the vacuum and the photon state, and a regularization scheme is proposed.
O(2) CHERN–SIMONS GAUGE THEORY AND Z2 ORBIFOLDS
Authors: AMANO KAORU , SHIROKURA HIROSHI
Published: November 2004

We quantize the three-dimensional O(2) pure Chern–Simons gauge field theory in a functional coherent-state representation. Both trivial and nontrivial flat O(2) bundles admit physical states. An explicit calculation relates the state functionals to the rational Z2-orbifold models.
BRST FIELD THEORIES FOR A QUANTUM LORENTZ PARTICLE
Authors: HATSUDA MACHIKO
Published: November 2004

From the study of string field theory, first quantized BRST symmetry is known to be a guiding principle in constructing field theories. We construct the first quantized BRST charge QB for a quantum Lorentz particle which is characterized by the constraints which are expressed in terms of (inhomogeneous) Lorentz generators. It is shown that the BRST cohomology of this system includes only the field strengths and not the fundamental gauge fields with nontrivial norms. By using this BRST charge, we obtain the field theory Lagrangian via the ∫ΨQBΨ construction, which leads to field equations for fields with arbitrary spin. However, this action cannot be used to derive a second quantized theory except for Dirac fields. For antisymmetric tensor fields, we can get the correct second quantized theories if we introduce extra conditions.
EQUIVALENCE OF STOCHASTIC, KLAUDER AND GEOMETRIC QUANTIZATION
Authors: HAJRA K. , BANDYOPADHYAY P.
Published: November 2004

The relativistic generalization of stochastic quantization helps us to introduce a stochastic-phase-space formulation when a relativistic quantum particle appears as a stochastically extended one. The nonrelativistic quantum mechanics is obtained in the sharp point limit. This also helps us to introduce a gauge-theoretical extension of a relativistic quantum particle when for a fermion the group structure of the gauge field is SU(2). The sharp point limit is obtained when we have a minimal contribution of the residual gauge field retained in the limiting procedure. This is shown to be equivalent to the geometrical approach to the phase-space quantization introduced by Klauder if it is interpreted in terms of a universal magnetic field acting on a free particle moving in a higher-dimensional configuration space when quantization corresponds to freezing the particle to its first Landau level. The geometric quantization then appears as a natural consequence of these two formalisms, since the Hermitian line bundle introduced there finds a physical meaning in terms of the inherent gauge field in stochastic-phase-space formulation or in the interaction with the magnetic field in Klauder quantization.
MOLECULES AS QUANTUM SHAPES AND HOW THEY VIOLATE P AND T
Authors: BALACHANDRAN A.P. , SIMONI A. , WITT D.M.
Published: November 2004

A geometric shape is a rigid shape in n-dimensional Euclidean space. These shapes commonly occur in the Born-Oppenheimer approximation in molecular physics, and collective models of nuclei. Abelian and non-Abelian generalizations of the vacuum angle of gauge theories are realized in the quantum theory of shapes. In this paper, such generalizations are presented in the language of modern quantum physics and it is shown that parity, [Formula: see text], and time reversal, [Formula: see text], are violated in certain of these quantum theories. However, the combined symmetry [Formula: see text] of parity composed with time reversal generally remains a good symmetry, just as in gauge theories. The exceptions are the quantum theories of staggered conformations which can violate only [Formula: see text]. The mechanism responsible for the loss of these symmetries is a generalization of the vacuum angle mechanism for the same effect. An important result of the present analysis is the demonstration that geometric shapes, molecules in the Born-Oppenheimer approximation, and nuclei in the collective model description furnish concrete systems which upon quantization discriminate between left- and right-handed coordinates even though this distinction is entirely absent in their classical descriptions.
METHODS FOR STUDYING 3 + 1 LOCALIZED STRUCTURES: THE SKYRMION AS THE ABSOLUTE MINIMIZER OF ENERGY
Authors: RYBAKOV YU. P. , SANYUK V. I.
Published: November 2004

General methods in search of stable structures in (3 + 1)-dimensional models are presented. Using the Skyrme model as an example, we exhibit the methods and demonstrate their ability to pick out the minimal-energy configurations. In the class of fields with unit topological charge these are the well-known Skyrmions (the spherically symmetric configurations), which realize the absolute minimum of the energy. In the second and higher homotopy classes the minimal-energy configurations are, however, of the axisymmetric type. We argue that these methods provide a good guide and support to numerical analysis of multidimensional structures in essentially nonlinear models for liquid crystals, cosmology, ferromagnets, nonlinear elasticity, and so on.
FRACTIONAL SUPERSYMMETRY AND MINIMAL COSET MODELS IN CONFORMAL FIELD THEORY
Authors: CHUNG STEPHEN-WEI , LYMAN EDWIN , TYE S.-H. HENRY
Published: November 2004

Starting from fractional supersymmetry as an extended Virasoro algebra, we generalize Felder's BRST cohomology method to construct the characters and branching functions — in terms of string functions — of the SU(2) and SU(3) coset models, for both the unitary and nonunitary cases.
GENERALIZED TODA AND VOLTERRA MODELS
Authors: AVAN J.
Published: November 2004

The mean procedure of Faddeev-Reshetikhin with non-Abelian automorphism groups is applied to construct generalizations of the open Toda sl(n, C) chain. These models admit a consistent reduction to integrable generalized Volterra models. An example of such models is analyzed: it leads in the continuum limit to the [Formula: see text] Hirota differential system, associated with two-matrix models of discrete gravity. The continuum limit of the general Volterra models and their relation with discretized versions of Wn-algebra are analyzed.
CONFORMAL FIELDS: A CLASS OF REPRESENTATIONS OF Vect(N)
Authors: LARSSON T.A.
Published: November 2004

Vect (N), the algebra of vector fields in N dimensions, is studied. Some aspects of local differential geometry are formulated as Vect(N) representation theory. There is a new class of modules, conformal fields, whose restrictions to the subalgebra sl(N+1)⊂ Vect (N) are finite-dimensional sl (N+1) representations. In this regard they are simpler than tensor fields. Fock modules are also constructed. Infinities, which are unremovable even by normal ordering, arise unless bosonic and fermionic degrees of freedom match.
Kirillov-Kostant theory and Feynman path integrals on coadjoint orbits of SU(2) and SU(1,1)
Authors: HASHIMOTO Takashi , OGURA Kazunori , OKAMOTO Kiyosato , SAWAE Ryuichi
Published: November 2004

Path integrals with Hamiltonians on coadjoint orbits of SU(2) and SU(1,1) are explicitly calculated, taking the operator ordering into account. The path integral gives the kernel function of the unitary operator of the representation which is constructed by the method of Kirillov-Kostant theory.
slq(n) Quantum Algebra As a Limit of the Elliptic Case
Authors: Hou Bo-yu , Shi Kang-jie , Yang Zhong-xia
Published: November 2004

We study the limit of the algebra associated with the solution of Z n elliptic YBE. And we give its specific relation with the quantum algebra sl q (n) .
THE HARVARD BINOCULAR HEAD
Authors: FERRIER NICOLA J. , CLARK JAMES J.
Published: November 2004

The ability to dynamically control the imaging parameters such as camera position, focus, and aperture is satisfied through the use of special purpose hardware such as a robotic head. This paper presents the design and control aspects of the Harvard Head, a binocular image acquisition system. We present three applications of the head in vision tasks concentrating on the computation of depth from controlled camera motion.
CONTROL HEURISTICS FOR SCHEDULING IN A PARALLEL BLACKBOARD SYSTEM
Authors: DECKER KEITH , GARVEY ALAN , HUMPHREY MARTY , LESSER VICTOR
Published: November 2004

This paper investigates the effects of parallelism on blackboard system scheduling heuristics. A parallel blackboard system is described that allows multiple knowledge source instantiations (KSIs) to execute in parallel using a shared-memory blackboard approach. New classes of control knowledge are defined that order the agenda by using information about the relationships between the goals of the KSIs. This control knowledge is implemented and tested in the DVMT application on a Sequent multiprocessor using BB1-style control heuristics. The usefulness of the heuristics is examined by comparing the effectiveness of problem-solving with and without the heuristics (as a group and individually). Problem solving with the new control knowledge results in improved system performance.
OFF LINE RECOGNITION OF HANDWRITTEN POSTAL WORDS USING NEURAL NETWORKS
Authors: BURGES C.J.C. , BEN J.I. , DENKER J.S. , LECUN Y. , NOHL C.R.
Published: November 2004

We describe a method, “Shortest Path Segmentation” (SPS), which combines dynamic programming and a neural net recognizer for segmenting and recognizing character strings. We describe the application of this method to two problems: recognition of handwritten ZIP Codes, and recognition of handwritten words. For the ZIP Codes, we also used the method to automatically segment the images during training: the dynamic programming stage both performs the segmentation and provides inputs and desired outputs to the neural network. Results are reported for a test set of 2642 unsegmented handwritten 212 dpi binary ZIP Code (5- and 9-digit) images.

For handwritten word recognition, we combined SPS with a “Space Displacement Neural Network” approach, in which a single-character-recognition network is extended over the entire word image, and in which SPS techniques are then used to rank order a given lexicon. We report results on a test set of 3000 300 ppi gray scale word images, extracted from images of live mail pieces, for lexicons of size 10, 100, and 1000.

Representing the problem as a graph as proposed in this paper has advantages beyond the efficient finding of the final optimal segmentation, or the automatic segmentation of images during training. We can also easily extend the technique to generate K “runner up” answers (for example, by finding the K shortest paths). This paper will also describe applications of some of these ideas.
RECONSTRUCTABLE PARALLEL THINNING
Authors: JANG BEN K. , CHIN ROLAND T.
Published: November 2004

This paper describes a reconstructable thinning process which is based on one-pass parallel thinning and the morphological skeleton transformation. It reduces a binary digital pattern into a unit-width connected skeleton enabling perfect reconstruction of the original pattern. The process uses thinning templates to iteratively remove boundary pixels and structuring templates of the morphological skeleton transformation to retain critical feature pixels for reconstruction. The thinning templates together with the extracted feature pixels ensure skeletal connectivity, unit width, and reconstructability. These essential properties are guaranteed regardless of the chosen structuring templates used in the morphological skeleton transformation. The thinning process is analyzed and results are presented. A number of implementation issues, such as the choice of structuring templates, the computational model, noise filtering, and computational efficiency, are also addressed.
A SYSTEMATIC EVALUATION OF SKELETONIZATION ALGORITHMS
Authors: LEE SEONG-WHAN , LAM LOUISA , SUEN CHING Y.
Published: November 2004

As a result of its central role in the preprocessing of image patterns, or because of its intrinsic appeal, the design of skeletonization algorithms has been a very active research area. However, few attempts have been made to evaluate the performance of different skeletonization algorithms.

This paper presents the results of experiments to evaluate the performance of 20 skeletonization algorithms previously published in the literature. These algorithms have been implemented on the SUN 3/60 workstation in C and tested with a large variety of character patterns. A systematic comparison of these algorithms has been made based on the following criteria: reconstructibility, computation speed, similarity to the reference skeleton, quality of the skeleton, connectivity after skeletonization, and the degree of parallelism.
TRAVELING WAVE FRONT AND ITS FAILURE IN A ONE-DIMENSIONAL ARRAY 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. This solution is obtained analytically and analyzed for the "primary real bifurcation". For diffusion coefficients less than some nonzero critical value it has been observed numerically that the traveling fronts fail to propagate. This nonlinear phenomena is similar to that observed from pulse propagation in nerves, and in coupled continuously-stirred tank reactors.
DYNAMICS OF CHUA'S CIRCUIT IN A BANACH SPACE
Authors: BLÁZQUEZ C. M. , TUMA E.
Published: November 2004

In this paper we present generalized theorems of the Shil'nikov type for evolution equations in Banach spaces of infinite dimension, which describe the behaviour of subsystems of solutions in a neighborhood of a double homoclinic orbits to the same saddle-focus point.
INTERACTIVE GRAPHICAL EXPLORATION OF MULTIDIMENSIONAL NONLINEAR DYNAMICAL SYSTEMS
Authors: CHALLINGER JUDY
Published: November 2004

This paper discusses the application of an inherently three-dimensional graphical representation tool, isosurfaces, as a means to interactively explore and visualize the attractors of a nonlinear dynamical system with a fifteen-dimensional parameter space. A program has been written which allows the scientist to interactively select and visualize three-dimensional sub-spaces of the fifteen-dimensional parameter space. The dynamical system used to illustrate these concepts is a discrete-time, nonlinear, three-nation Richardson model with economic constraints. This dynamical system, which models the shifting alliances of nations in an arms race, maps an initial point in the unit cube to another point in the unit cube after multiple iterations of the model functions. Using an isosurface function on the resulting volumetric data set, surfaces indicating the changing alliances of nations are generated and rendered.
CANDYS/QA—A SOFTWARE SYSTEM FOR QUALITATIVE ANALYSIS OF NONLINEAR DYNAMICAL SYSTEMS
Authors: FEUDEL ULRIKE , JANSEN WOLFGANG
Published: November 2004

Numerical methods are often needed if bifurcation phenomena in nonlinear dynamical systems are studied. In this paper the software system CANDYS/QA for numerical qualitative analysis is presented. A wide class of problems is treated: computation of invariant sets (e.g., steady-states and periodic orbits), path-following (continuation) of such sets, and the related bifurcation phenomena. The following bifurcation situations are detected and the corresponding critical points are calculated during path-following: turning, bifurcation, Hopf bifurcation, period-doubling, torus bifurcation points (one-parameter problems) as well as cusp and Takens-Bogdanov points (two-parameter problems). A number of newly developed methods (e.g., for computation of the Poincaré map) as well as algorithms from the literature are described to demonstrate the whole procedure of a qualitative analysis by numerical means. An illustrative example analyzed by CANDYS/QA is included.
THE DYNAMICS OF RUNGE–KUTTA METHODS
Authors: CARTWRIGHT JULYAN H. E. , PIRO ORESTE
Published: November 2004

The first step in investigating the dynamics of a continuous-time system described by an ordinary differential equation is to integrate to obtain trajectories. In this paper, we attempt to elucidate the dynamics of the most commonly used family of numerical integration schemes, Runge–Kutta methods, by the application of the techniques of dynamical systems theory to the maps produced in the numerical analysis.
FOLLOWING PATHS OF SYMMETRY-BREAKING BIFURCATION POINTS
Authors: BOLSTAD JOHN H.
Published: November 2004

We propose a pseudo-arclength continuation algorithm for computing paths of Z 2-symmetry-breaking bifurcation points for two-parameter nonlinear elliptic problems. The algorithm consists of an Euler predictor step and a solution step composed of a sequence of Newton iterations. This work generalizes the algorithm of Werner and Spence for locating a one-parameter symmetry-breaking bifurcation point by using the approach of Keller and Fier for following a (two-parameter) path of limit points (a "fold"). By repeated use of the bordering algorithm, we solve linear systems whose matrix is the "symmetric" Jacobian or "antisymmetric" Jacobian, thus fully exploiting any (block tridiagonal) structures present. We give numerical results for the steady, axisymmetric flow between rotating coaxial cylinders (Taylor–Couette flow). For finite cylinders, we compute the fold curve and path of symmetry-breaking bifurcation points for small aspect ratios, and illustrate a new method to accurately locale the two Z 2-symmetric codimension one singularities. For infinite cylinders, we show the projections on the (aspect ratio, Reynolds number) plane of the folds and bifurcation point paths in the neighborhood of the two-cell/four-cell neutral curve crossing. We numerically verify a conjecture of Meyer–Spasche and Wagner concerning the connection of two neutral-curve crossings by a path of secondary subharmonic bifurcations.
ENHANCING THE SOFTWARE LIFE CYCLE OF KNOWLEDGE-BASED SYSTEMS USING A TASK-BASED SPECIFICATION METHODOLOGY
Authors: LEE JONATHAN , YEN JOHN
Published: November 2004

Several methodologies have been developed to enhance the software life cycle of knowledge-based systems by emphasizing on the use of both prototypes and specifications. However, these methodologies focus on the development phase of knowledge-based systems. The roles of prototypes and specifications in the maintenance phase has not been fully explored. Because a suitable problem specification for a knowledge-based system is often difficult to acquire, validating changes to non-executable solution specification during the maintenance phase can be a problem. To address this, we propose an alternative paradigm in which the prototype complements the specification throughout the life cycle. The traceability between them is facilitated by organizing both types of artifacts using a common functional decomposition structure. Based on our task-based specification methodology (TBSM), we have also developed a knowledge engineering tool (called TAME) to facilitate the acquisition and the organization of the specification and the prototype. The proposed methodology and the tool together can thus enhance the verification, validation, and the maintenance of knowledge-based systems through their life cycles.
SPECIFICATION OF REAL-TIME SYSTEMS
Authors: PATNAIK L.M. , MALL R.
Published: November 2004

Inspite of numerous research advancements made in recent years in the area of formal techniques, specification of real-time systems is still proving to be a very challenging and difficult problem. In this context, this paper critically examines state-of-the-art specification techniques for real-time systems and analyzes the emerging trends.
DELTA-PLAN-ES—THE INTERACTIVE SYSTEM OF NUMERICAL ANALYSIS OF IMPROPER LINEAR PROGRAMS
Authors: EREMIN I.I. , POPOV L.D.
Published: November 2004

A linear program is said to be improper if its feasible set is empty or its optimal value is infinite. Improper programs appear as a result of inaccuracy of information, of excessive simplification, of considering some restrictions as unchangeable, etc. Moreover, a contradictory model may fit the real contradictions adequately, and the ways of transforming it into a noncontradictory one (the ways of correcting it) may correspond to real procedures of solving these contradictions. The paper describes the DELTA-PLAN-ES interactive system for numerical analysis of improper linear programs. The system is designed for Rjad-2 ES computers.
CIRCULAR VISIBILITY FROM A POINT IN A SIMPLE POLYGON
Authors: AGARWAL PANKAJ K. , SHARIR MICHA
Published: November 2004

In this paper we define the notion of circular visibility, and present an O (n log n) time algorithm to compute the portion of a given simple polygon [Formula: see text] circularly visible from a fixed point lying inside [Formula: see text]. The second problem that we study is the circle shooting from a fixed-point, which can be formulated as follows: Given a simple polygon [Formula: see text] and a point s inside [Formula: see text], preprocess [Formula: see text] so that given a circle π passing through s, one can quickly compute the first point of [Formula: see text] intersected by π as we follow π from s in a clockwise direction. We show that [Formula: see text] can be preprocessed, in time O (n log n), into a data structure of linear size, so that a query can be answered in logarithmic time.
FACTORIAL LANGUAGES AND SOME COMBINATORIAL PROPERTIES OF SEMIGROUPS
Authors: JUSTIN JACQUES , PIRILLO GIUSEPPE
Published: November 2004

We give characterizations for the Rees quotients of free semigroups that have such or such combinatorial property: repetitivity, linear growth, permutation property or one of its variants.
THE BIDETERMINISTIC CONCATENATION PRODUCT
Authors: PIN JEAN-ERIC , THÉRIEN DENIS
Published: November 2004

This paper is devoted to the study of the bideterministic concatenation product, a variant of the concatenation product. We give an algebraic characterization of the varieties of languages closed under this product. More precisely, let V be a variety of monoids, [Formula: see text] the corresponding variety of languages and [Formula: see text] the smallest variety containing [Formula: see text] and the bideterministic products of two languages of [Formula: see text]. We give an algebraic description of the variety of monoids [Formula: see text] corresponding to [Formula: see text]. For instance, we compute [Formula: see text] when V is one of the following varieties: the variety of idempotent and commutative monoids, the variety of monoids which are semilattices of groups of a given variety of groups, the variety of ℛ-trivial and idemptotent monoids. In particular, we show that the smallest variety of languages closed under bideterministic product and containing the language {1}, corresponds to the variety of [Formula: see text]-trivial monoids with commuting idempotents. Similar results were known for the other variants of the concatenation product, but the corresponding algebraic operations on varieties of monoids were based on variants of the semidirect product and of the Malcev product. Here the operation [Formula: see text] makes use of a construction which associates to any finite monoid M an expansion [Formula: see text] with the following properties: (1) M is a quotient of [Formula: see text] (2) the morphism [Formula: see text] induces an isomorphism between the submonoids of [Formula: see text] and of M generated by the regular elements and (3) the inverse image under π of an idempotent of M is a 2-nilpotent semigroup.
AMPLIFICATION AND PHASE CONJUGATION OF WEAK SIGNALS
Authors: KULAGIN O.V. , PASMANIK G.A. , SHILOV A.A.
Published: November 2004

The results of the study on phase conjugation of weak optical signals with the energy of units of photons are considered. Basic concepts of a semi-classical theoretical approach to describe amplification and phase conjugation (PC) of such signals are presented. A review is given on the experimental investigations that allowed for reaching a limit (about 1 photon for a mode) sensitivity of optical systems with PC-mirrors for a large (~ 105) number of resolution elements. High-sensitivity PC-mirror optical systems are demonstrated for a variety of applications.
STIMULATED DIFFUSION BACKSCATTERING WITH PHASE CONJUGATION
Authors: KOROL’KOV S.A. , MAMAEV A.V. , SHKUNOV V.V.
Published: November 2004

The advantages and conditions to observe the phase conjugation in photorefractive crystals by degenerate stimulated backscattering via diffusion gratings are discussed. Different version of discrimination physics for self conjugation in selfstarting backscattering are demonstrated. Several possibilities to obtain self- and double-conjugation by means of four-wave mixing on reflecting gratings in photorefractive crystals as well as some related problems are pointed out.
PHASE CONJUGATION IN A HIGH POWER REGENERATIVE LASER AMPLIFIER SYSTEM
Authors: HACKEL L.A. , MILLER J.L. , DANE C.B.
Published: November 2004

We discuss the design and performance of a master oscillator/regenerative power amplifier laser system using a stimulated Brillouin scattering phase conjugator to control beam aberrations within the amplifier cavity. The master oscillator is a self-seeded Q- switched Nd:YLF laser which provides up to 40 mJ of single frequency light in a 10 ns to 15 ns pulse for amplification. The power amplifier uses a regenerative ring design with approximately 10 total passes and a phase conjugate mirror after the 5th pass. The conjugator is necessary to help produce a plane wavefront and thus a uniform intensity distribution within the ring, a requirement to avoid damage at the high intensities. The energy at the phase conjugate mirror exceeds 1 J/pulse and thus careful attention is paid to the tradeoff between input energy, conjugator reflectivity and near field spatial fidelity of the return. The laser output is in the range of 20 J/pulse, 2 GW peak with average power of 70 W. Measurements have been made at high power of the near field and far field beam quality.
AN INFERENCE BROWSER FOR VERIFYING THE KNOWLEDGE BASE IN KNOWLEDGE-BASED SYSTEMS
Authors: YOO SUK I. , PARK CHANG H.
Published: November 2004

In developing knowledge-based systems, the process of collecting the knowledge from the experts, representing it in certain formats, and verifying it is required. It is however not easy to verify the formulated knowledge base by checking if a desired conclusion is derived by a sequence of inferring steps. This paper suggests a model of inference browsers by which the knowledge engineers may easily consult a sequence of inferring steps and verify the knowledge base. The suggested inference browser provides the environment in which the knowledge engineers may observe a sequence of inferring steps displayed in the graphical form, access directly the contents of the rules and the facts on the sequence, and observed a newly generated sequence of inferring steps when some of the rules or the facts are changed. Further, based on the graphically displayed inferring sequence, the inference browser itself detects the erroneous inferring step if it exists, analyzes it, and corrects the associated errors in the knowledge base. Finally the suggested inference browser is compared to other similar tools in terms of the facilities they provide.
SNITCH: AUGMENTING HYPERTEXT DOCUMENTS WITH A SEMANTIC NET
Authors: MAYFIELD JAMES , NICHOLAS CHARLES
Published: November 2004

A new model of hypertext, in which text is augmented with a fine-grained semantic net representation of the text, solves several problems found in traditional hypertext models. In the new model, hypertext links are paths that originate in the text, move across to the semantic net, traverse a sub-path through the semantic net, then return to a different point in the text. Benefits of the model include a strong semantics for links, dynamic discovery of links, link reusability, and automatic creation of links. The SNITCH hypertext system, which is based on this model, allows a user to access data in ways never foreseen by the hypertext author.
A NEW VIEW ON THE PROBLEM OF ANISOTROPY OF THE COSMIC BACKGROUND RADIATION
Authors: GURZADYAN V.G. , KOCHARYAN A.A.
Published: November 2004

The anisotropy properties of the Cosmic Microwave Background Radiation (CMB) are considered within the framework of the photon beam mixing effect developed earlier. The existence of an observable characteristic of the CMB is shown, namely the geometrical shape of anisotropy spots and their degree of complexity, which can contain unique information on cosmological parameters and the life history of the Universe. If future experiments (COBE and others) indicate such features of anisotropy maps, then one can have serious evidence for the negative curvature of the Universe.
STRUCTURE IN A LOITERING UNIVERSE
Authors: FELDMAN HUME A. , EVRARD AUGUST E.
Published: November 2004

We study the formation of structure for a universe that undergoes a recent loitering phase. We compare the nonlinear mass distribution to that in a standard, matter dominated cosmology. The statistical aspects of the clustered matter are found to be robust to changes in the expansion law, an exception being that the peculiar velocities are lower by a factor of ~3 in the loitering model. Further, in the loitering scenario, nonlinear growth of perturbation occurs more recently (z~3–5) than in the matter dominated case. Differences in the high redshift appearances of the two models will result but observable consequences depend critically on the chosen form, onset and duration of the loitering phase.
A KINEMATIC DESCRIPTION OF THE EXPANSION OF THE UNIVERSE
Authors: SAVICKAS D.
Published: November 2004

A kinematic expression for the Hubble parameter H is derived which defines it directly in terms of the positions and velocities of all existing mass particles. The derivation is simply based on the concept that the numerical value of H at any instant of time is determined solely by particle positions and velocities that exist at that instant, and it is only indirectly affected by gravity through its actions on particles which change the positions and velocities. This definition of H does not depend on the motion of photons because the motion of a photon in a distant galaxy is determined by H as it moves with a constant velocity in the galaxy’s inertial system at rest in the Hubble drift. The kinematic definition of H is shown to be identical to the conventional expression H=Ṙ/R. Under general conditions it behaves in the usual manner. But in the case when all matter is located in a small volume of space, such as that which could have occurred at the time of origin of the universe, there exists for a brief time a kinematic repulsion which acts in addition to the usual gravitational attraction that is described in the standard solution of relativity. The repulsion could be strong enough to overcome gravitation and cause even a static universe to quickly evolve into an expanding one. In the case of an initially pure and static radiation universe that subsequently expands and creates all matter during the expansion, the kinematically defined H allows matter to be created in clusters at a very early time within a highly uniform background of radiation.
SUPERLUMINARY UNIVERSE: A POSSIBLE SOLUTION TO THE INITIAL VALUE PROBLEM IN COSMOLOGY
Authors: MOFFAT J.W.
Published: November 2004

The spontaneous breaking of local Lorentz invariance in the early Universe, associated with a first order phase transition at a critical time tc, generates a large increase in the speed of light and a superluminary communication of information occurs, allowing all regions in the Universe to be causally connected. This solves the horizon problem, leads to a mechanism of monopole suppression in cosmology and can resolve the flatness problem. After the critical time tc, local Lorentz (and diffeomorphism) invariance is restored and light travels at its presently measured speed. The kinematical and dynamical aspects of the generation of quantum fluctuations in the superluminary Universe are investigated. A scale invariant prediction for the fluctuation density amplitude is obtained.
GINGA OBSERVATIONS OF X0512–401 IN THE GLOBULAR CLUSTER NGC1851
Authors: ERCAN E.N. , CRUISE A.M. , KELLETT B.J.
Published: November 2004

We present here the first detailed spectral observations of the low-mass X-ray binary source X0512–401 located in the globular cluster NGC1851 obtained by Ginga. We have found that the Ginga LAC data of X0512–401 are best fitted by a “two-component” spectral model: power-law with exponential cut-off and a blackbody. The inclusion of a 6.7 KeV Fe emission line did not improve our best fit. In the light of the present observations and the previous studies concerning the importance of Comptonization, our model requires a scattering cloud surrounding the neutron star, with a Thomson optical depth of ~5. The detection of ~30–40 hr periodicity is hard to interpret in terms of the possible binary period of the system, since most of these systems have binary periods of a few hours or even less. It may either suggest that the accretion disk around the neutron star is precessing or there is a third body in the system.
SIMULATING THE INTERACTION BETWEEN A SOCIETY AND A RENEWABLE RESOURCE
Authors: BOUSQUET F. , CAMBIER C. , MULLON C. , MORAND P. , QUENSIERE J. , PAVÉ A.
Published: November 2004

Since a few years environmental studies have included human societies in the ecosystem in order to understand the interaction between the ecological and social dynamics and therefore there is a need to synthesize various scientific points of view. We have developed a simulator to represent both social, economic and ecological knowledge to contribute to a synthesis of the multidisciplinary knowledge of the Niger inland delta fishery.

In this paper we present the simulator, and, in order to give a general outline of its use we present different experimentations. The architecture of the simulator is based on Distributed Artificial Intelligence principle (multi-agents simulations, blackboard architecture, object oriented language). We simulate an aquatic ecosystem submitted to an increase of the fishing effort and compare the effect of different representation of fishing effort. As a result of the simulations, focus can be put on the relation between space sharing rules and the evolution of the ecological equilibrium. The simulator is considered as a discussion tool to lead to interdisciplinary meetings.
RANK-SIZE RELATION FOR A MULTI-SPECIES SYSTEM WITH AN EXCLUSIVE INTERFERENCE
Authors: SENO HIROMI
Published: November 2004

A rank-size relation for a stationary distribution of a multi-species diffusion system is considered. Each species in the community is characterized by the population size in an isolated region. It is easily able to be assigned the rank k(= 1, 2, …) of species from the largest to the smallest with respect to the population size. We discuss the rank-size relation of a stationary community, making use of a stationary solution for a multi-species system of diffusion equations with an exclusive interference among species.