bluuebunny/crossref_metadata_2025 huggingface dataset:
STOCHASTIC PUZZLE GRAMMARS
Authors: SIROMONEY RANI , HUQ ABDUL , CHANDRASEKARAN M. , SUBRAMANIAN K. G.
Published: November 2004

Nivat et al. proposed a class of grammars called puzzle grammars. Such models are suitable for describing and generating connected arrays consisting of unit cells. In this paper, we introduce the stochastic version of puzzle grammars. Conditions for their consistency are given. Although the simplest of puzzle grammars, called basic puzzle grammar, generates a larger class of pictures than regular array grammars, the additional generative power is restricted and it requires considerable effort to write grammars for even pictures whose complexity is not high. We propose a parallel version of the puzzle grammar model which lends itself naturally to the generation of pictures. Several examples are given to illustrate the power of this model. Its stochastic version is presented along with an application to the clustering of syntactic patterns.
A PARALLEL ALGORITHM FOR ANALYZING CONNECTED COMPONENTS IN BINARY IMAGES
Authors: CHIAVETTA FRANCO , DI GESÙ VITO , RENDA ROSALIA
Published: November 2004

In this paper, a parallel algorithm for analyzing connected components in binary images is described. It is based on the extension of the Cylindrical Algebraic Decomposition (CAD) to a two-dimensional (2D) discrete space. This extension allows us to find the number of connected components, to determine their connectivity degree, and to solve the visibility problem. The parallel implementation of the algorithm is outlined and its time/space complexity is given.
COMBINING IMAGE PROCESSING OPERATORS AND NEURAL NETWORKS IN A FACE RECOGNITION SYSTEM
Authors: FLOCCHINI PAOLA , GARDIN FRANCESCO , MAURI GIANCARLO , PENSINI MARIA PIA , STOFELLA PAOLO
Published: November 2004

This paper describes a system able to recognize human faces from different perspectives, and which have different expressions. It possibly presents some kind of noise in their representation.

The problem of face recognition has been approached using a complex architecture based on a hierarchy of neural networks, with a particular self-referencing structure. The system, in fact, is structured as a tree in which nodes correspond to neural networks, each one having different tasks. Each leaf is a recognition module composed by some networks with different characteristics depending on the different preprocessing operators used. These networks are coordinated by a supervisor in a self-referencing structure. During the training phase, the supervisor, called Meta-Net, observes the behaviour of recognition nets and learns which net is more able in which task, while during the test phase it decides, given an input image, which weights to assign to each network and modifies their output in order to obtain the final result.

This architecture shows a high generalization capability and allows the recognition of images with different kinds of noise better than what each single network can do, as confirmed by a preliminary experimental evaluation.
A FEEDFORWARD NEURAL NETWORK CLASSIFIER MODEL: MULTIPLE CLASSES, CONFIDENCE OUTPUT VALUES, AND IMPLEMENTATION
Authors: KOUTSOUGERAS CRIS , GEORGIOU GEORGE , PAPACHRISTOU CHRISTOS
Published: November 2004

The Athena model is a tree-like net for pattern classification. This paper presents the formalisms on which the model's internal representations and function are based. It also presents an adaptive algorithm to be used with this model. The adaptation is based on entropy optimization. The difficult problem of the optimization is handled by use of Fisher's multiple discriminants method. A method is also presented by which confidence values are produced for the overall classification decision. Finally, a data flow architecture using optical processing elements is considered for the model's implementation.
QUALITATIVE DESCRIPTION OF THREE-DIMENSIONAL SCENES
Authors: BISWAS PRABIR K. , MUKHERJEE JAYANTA , CHATTERJI B. N. , CHAKRABARTY P. P.
Published: November 2004

This paper describes a system which obtains a structural scene description of 3-D objects from range images. The system uses a hierarchical approach to obtain higher level primitives from lower level ones. Instead of a detailed mathematical approach, qualitative reasoning by rule based deduction is used to obtain the scene description. The rule bases are also hierarchical and several special control strategies like rule pruning, windowing (or zoning) and fact inhibition are used to considerably improve the speed of the system. Experimental results and performance of the system on actual range images are presented.
COMPUTING WITH CAUSAL THEORIES
Authors: TIN ERKAN , AKMAN VAROL
Published: November 2004

Formalizing commonsense knowledge for reasoning about time has long been a central issue in AI. It has been recognized that the existing formalisms do not provide satisfactory solutions to some fundamental problems, viz. the frame problem. Moreover, it has turned out that the inferences drawn do not always coincide with those one had intended when one wrote the axioms. These issues call for a well-defined formalism and useful computational utilities for reasoning about time and change. Yoav Shoham of Stanford University introduced in his 1986 Yale doctoral thesis an appealing temporal nonmonotonic logic and identified a class of theories, causal theories, which have computationally simple model-theoretic properties. This paper is a study towards building upon Shoham's work on causal theories. We concentrate on improving computational aspects of causal theories while preserving their model-theoretic properties.
ROBUST MORPHOLOGICALLY CONTINUOUS FOURIER DESCRIPTORS I: PROJECTION-GENERATED DESCRIPTORS
Authors: DOUGHERTY EDWARD R. , LOCE ROBERT P.
Published: November 2004

By generating Fourier descriptors based upon the waveform induced by a pattern's geometric projection, a number of classic difficulties with the Fourier-descriptor methodology are mitigated. Not only are the descriptors invariant with respect to scale, translation, and rotation (as is usually the case), they are also continuous in the Hausdorff metric and robust with respect to both point noise and occlusion. An additional advantage is that they can be computed relative to a thresholded image without first finding an edge, thereby avoiding the difficulties typically present in thinning and orientation determination. The present paper discusses the method of projection-generated Fourier descriptors, as well as a study of the sensitivity to point noise. A companion paper will present the morphological properties and the effect of pattern occlusion.
AN EFFICIENT TEST PROCEDURE FOR FUNCTIONAL FAULTS IN SEMICONDUCTOR RANDOM ACCESS MEMORIES
Authors: KIM YUN-HONG , HONG IN-SIK , JUNG JUN-MO , KIM YOUNG-OO , LIM IN-CHIL
Published: November 2004

This paper proposes a new procedure for testing semiconductor random access memories (RAMs). The test procedure detects simultaneously present functional faults such as stuck-at faults, transition faults and coupling faults and requires 19N operations, which is an improvement over conventional procedures. Thus testing time is reduced by the smaller number of operations of the test procedure, test generation and applications are simplified by the linear address marching.
INTERVAL LOGIC FOR PROCESS CONTROL SYSTEM SPECIFICATION
Authors: CHIU PETER P.K. , CHEUNG Y.S.
Published: November 2004

A new methodology for the specification of process control systems involving time interval information and verification of their design is proposed. The specification is based on interval logic and a time-interval operator is defined. By means of this operator, time interval information is incorporated in the specification. Thus properties that involve time intervals can be verified. Moreover, combinational and sequential processes can be specified. An application example for a process control system is demonstrated.
COMPUTER-AIDED ANALYSIS OF CYCLICALLY SWITCHING CIRCUITS WITH IMPLICIT CONTROLLED TRANSITION TIMES
Authors: IOINOVICI ADRIAN , COSTINER SORIN
Published: November 2004

The power electronics circuits can be seen as a subset of periodically switched networks. Their distinctive feature is the variable duration of the switching stages, dependent on implicit, threshold conditions. The paper presents a new computer-oriented approach for transient and steady-state analysis of this class of electronic circuits. The switching elements are extracted in a linear time-variable two-port, which is defined by its nodal equations. A set of modified nodal equations is obtained for describing the overall transient of the circuit. No small-signal approximations are required. The analytical expressions of the network waveforms are found accurately for each switching stage. The transient computation is based on the cyclical use of these expressions together with the threshold conditions. The general method is then applied to simulation of current-mode quasi-resonant converters. Transients due to large-signal changes in the line voltage and load are studied. The influence of the load value on transient peaks is pointed out. The voltage conversion ratio versus switching frequency is studied for both the half- and full-wave mode operation. A computer program for time-domain simulation of power quasi-resonant converters is developed based on this approach.
DESIGN AND IMPLEMENTATION OF A LOW-COST SYSTOLIC ARRAY SYSTEM
Authors: ANDERSON DAVID M. , SOBELMAN GERALD E. , SMITH ROSS A.W.
Published: November 2004

Actual implementations of systolic arrays are currently thought of as being large, complex and expensive. However, by taking advantage of commercially available multiplier/accumulator chips, a systolic array can be assembled as a low-cost, compact board-level system. We describe one such practical design which uses the NCR45CM16 CMOS multiplier/accumulator together with a specially-designed controller/router chip which handles the intracell and intercell communications functions. A demonstration four-cell linear systolic array has been constructed and tested using a PC/XT host computer. An assembler program, which also runs on the host, translates an assembler code representation of a systolic algorithm into object code. The object code is then transferred from the host to the systolic array for execution. Sample matrix computations demonstrate that the systolic array is functioning properly.
METHODOLOGY FOR FORMULATION OF CIRCUIT EQUATIONS FOR SPECTRAL ANALYSIS
Authors: BAUMGARTNER C. , PALUSINSKI O.A.
Published: November 2004

While analog simulation of integrated circuits is a very powerful design tool, the maximum size of the investigated circuits is limited by the necessary CPU times. Using spectral technique with respect to Chebyshev polynomials and in conjunction with waveform relaxation was shown to considerably reduce the computational effort for transient simulation. After a brief introduction of this novel simulation technique, equation formulation will be described in detail. Also discussed is how the choice of circuit variables used for formulation affects theoretical and numerical properties of the method. Element “stamps” are given which can be used for the construction and solution of the linear equation system.
DESIGN OF TWO-LEVEL PIPELINED SYSTOLIC ARRAY AND ITS APPLICATION TO IMAGE
Authors: JEN CHEIN-WEI , LIU CHI-MIN
Published: November 2004

Two-level pipelined systolic array can attain parallelism down to lower levels and provide much higher throughput and computational speed than conventional ones. This paper presents a design procedure starting from an algorithm representation, called Dependence Graph (DG). Arrays with different performances can be obtained by applying the various linear transformation matrices on DG.

Image resampling is a process for image construction and display. It has important applications in image processing or in digital TV. In this paper, two design considerations are applied to build high-performance VLSI image resampler. First, two-level pipelined systolic array is designed to maximize parallelism and also make VLSI implementation highly feasible. Second, a modified two-pass resampling scheme is devised to reduce the amount of required storage and increase the concurrency between two passes of resampling. This image resampler can get a throughput of one pixel per clock period being smaller than the latency of an adder. The requirement for storage is only several line buffers.
VLSI ARCHITECTURES FOR ITERATIVE IMAGE RESTORATION
Authors: KATSAGGELOS A.K. , KUMAR S.P.R. , SARRAFZADEH M.
Published: November 2004

In this paper mesh, pyramid, and mesh of pyramids implementations of an iterative image restoration algorithm are proposed. These implementations are based on a single step regularized iterative restoration algorithm. Area-time bounds on the proposed implementations are established. The efficiency of the proposed VLSI algorithms is evaluated by comparing the established bounds against lower bounds on AT2, where A is the area of the VLSI chip and T is its computation time.
GLOBAL BIFURCATION ANALYSIS OF THE DOUBLE SCROLL CIRCUIT
Authors: KOMURO M. , TOKUNAGA R. , MATSUMOTO T. , CHUA L. O. , HOTTA A.
Published: November 2004

An in-depth analysis is made of the global 2-parameter bifurcation structures of the double scroll circuit in terms of their homoclinic, heteroclinic, and periodic orbits. Many fine details are uncovered via a 3-dimensional "unfolding" of the 2-parameter bifurcation structures.

Major findings are:

(i) The parameter sets which give rise to the homoclinic and heteroclinic orbits (homoclinic and heteroclinic bifurcation sets) studied in this paper are found to be all connected to each other via only one family of periodic orbits.

(ii) Moreover, the structure of the windows of this family essentially determines the global structure of the periodic windows of the double scroll circuit.

These bifurcation analyses are accomplished by deriving first the relevant bifurcation equations in exact analytic form and then solving these nonlinear equations by iterations. No numerical integration formula for differential equations are used.
"CROSSROAD AREA–SPRING AREA" TRANSITION (I) PARAMETER PLANE REPRESENTATION
Authors: CARCASSES J. P. , MIRA C. , BOSCH M. , SIMÓ C. , TATJER J. C.
Published: November 2004

This paper is devoted to the bifurcation structure of a parameter plane related to one- and two-dimensional maps. Crossroad area and spring area correspond to a characteristic organization of fold and flip bifurcation curves of the parameter plane, involving the existence of cusp points (fold codimension-two bifurcation) and flip codimension-two bifurcation points. A transition "mechanism" (among others) from one area type to another one is given from a typical one-dimensional map.
HORSESHOES IN THE TWIST-AND-FLIP MAP
Authors: BROWN RAY , CHUA LEON
Published: November 2004

We derive an analytical relationship between the parameters of a square-wave forced, nonlinear, two-dimensional ordinary differential equation which determines conditions under which the Poincaré map has a horseshoe. This provides an analytical test for chaos for this equation.

In doing this we show that the Poincaré map has a closed-form expression as a transformation of R2 of the form FTFT, where F is a flip, i.e., a 180-degree rotation about the origin and T is a twist centered at (a, 0) for a > 0. We show that this derivation is quite general.

We aiso show how to relate our results to ODEs with continuous periodic forcing (e.g., the sinusoidal-forced Duffing equation).

Finally, we provide a conjecture as to a sufficient condition for chaos in square-wave forced, nonlinear ODEs.
THE NUMERICAL SOLUTION OF NONLINEAR STOCHASTIC DYNAMICAL SYSTEMS: A BRIEF INTRODUCTION
Authors: KLOEDEN P. E. , PLATEN E. , SCHURZ H.
Published: November 2004

The numerical analysis of stochastic differential equations, currently undergoing rapid development, differs significantly from its deterministic counterpart due to the peculiarities of stochastic calculus. This article presents a brief, pedagogical introduction to the subject from the perspective of stochastic dynamical systems. The key tool is the stochastic Taylor expansion. Strong, pathwise approximations are distinguished from weak, functional approximations, and their role in stability with Lyapunov exponents and stiffness is discussed.
PERIODIC INHIBITION OF LIVING PACEMAKER NEURONS (I): LOCKED, INTERMITTENT, MESSY, AND HOPPING BEHAVIORS
Authors: SEGUNDO J. P. , ALTSHULER E. , STIBER M. , GARFINKEL A.
Published: November 2004

This communication is concerned with an embodiment of periodic nonlinear oscillator driving, the synaptic inhibition of one spike-producing pacemaker neuron by another. Data came from a prototypical living synapse. Analyses centered on a prolonged condition between the transients following the onset and cessation of inhibition. Evaluations were guided by point process mathematics and nonlinear dynamics.

A rich and exhaustive list of discharge forms, described precisely and canonically, was observed across different inhibitory rates. Previously unrecognized at synapses, most forms were identified with several well known types from nonlinear dynamics. Ordered by decreasing regularities, they were locked, intermittent (including walk-throughs), messy (including erratic and stammerings) and hopping. Each is discussed within physiological and formal contexts. It is conjectured that (i) locked, intermittent and messy forms reflect limit cycles on 2-tori, quasiperiodic orbits and strange attractors, (ii) noise in neurons hovering around threshold contributes to certain intermittent and stammering behaviors, and (iii) hopping either reflects an attractor with several portions or is nonstationary and noise-induced.
HOW TWO COMPETING CHARACTERISTIC EXPONENTS GENERATE DIFFERENT CLASSES OF FRACTAL BOUNDARIES
Authors: PEINKE JOACHIM , KLEIN MICHAEL , KITTEL ACHIM , KAHLERT CLAUS , STOOP RUEDI , PARISI JÜRGEN , RÖSSLER OTTO E.
Published: November 2004

We present support to the conjecture, proposed recently, that two characteristic exponents within a dynamical system decide whether a fractal boundary separating two basins of attraction is nowhere differentiable, self-similar, or self-affine, respectively.
THE ACCURACY OF COMPUTER ALGORITHMS IN DYNAMICAL SYSTEMS
Authors: DURKIN MARILYN B.
Published: November 2004

We study the mathematical accuracy of computer algorithms used to produce pictures of Julia sets by analyzing two representatives cases of the complex exponential function. We first define the Julia set and give the simple algorithm used for the exponential function. We then define what it means for a picture to be "right" and consider the two totally different Julia sets of E0.3(z) = 0.3ez and E(z) = ez. We use a simple expansion argument together with the properties of the exponential function to show that each of these pictures is correct.
CHAOTIC SCATTERING IN TIME-DEPENDENT HAMILTONIAN SYSTEMS
Authors: LAI YING-CHENG , GREBOGI CELSO
Published: November 2004

We consider the classical scattering of particles in a one-degree-of-freedom, time-dependent Hamiltonian system. We demonstrate that chaotic scattering can be induced by periodic oscillations in the position of the potential. We study the invariant sets on a surface of section for different amplitudes of the oscillating potential. It is found that for small amplitudes, the phase space consists of nonescaping KAM islands and an escaping set. The escaping set is made up of a nonhyperbolic set that gives rise to chaotic scattering and remains of KAM islands. For large amplitudes, the phase space contains a Lebesgue measure zero invariant set that gives rise to chaotic scattering. In this regime, we also discuss the physical origin of the Cantor set responsible for the chaotic scattering and calculate its fractal dimension.
SINGULAR POINTS OF PLANE CURVES GENERATED BY PERIOD DOUBLING BIFURCATION POINTS AND A METHOD FOR COMPUTING THEM
Authors: YAMAMOTO NORIO
Published: November 2004

This paper is concerned with nodal points, isolated points and cusp points (PD) appearing on a locus of period-doubling bifurcation points and the accurate location of them. Such points can be observed in periodic differential systems (e.g., Duffing's equation) in nonlinear oscillations. In a suitable two-dimensional parameter-plane, such points can be formulated as double (singular) points of plane curves defined by a bifurcation equation, and a method for computing them is proposed.
MODELING OF AN OBSERVED TURING STRUCTURE IN THE ${\rm CLO}_2^- -{\rm I}^-$–MALONIC ACID SYSTEM
Authors: GUSLANDER JOHN , FIELD RICHARD J.
Published: November 2004

The two-dimensional stationary concentration pattern (Turing structure) recently observed by Castets, Dulos, Boissonade and De Kepper in the [Formula: see text]–Malonic Acid (CIM) reaction has been qualitatively simulated on the basis of a realistic chemical mechanism.
SCALING UP RULE-BASED SOFTWARE DEVELOPMENT ENVIRONMENTS
Authors: BARGHOUTI NASER S. , KAISER GAIL E.
Published: November 2004

Rule-based software development environments (RBDEs) model the software development process in terms of rules that encapsulate development activities, and assist in executing the process via forward and backward chaining over the rule base. We investigate the scaling up of RBDEs to support (1) multiple views of the rule base for multiple users and (2) evolution of the rule base over the lifetime of a project. Our approach is based on clarifying two distinct functions of rules and chaining: maintaining consistency and automation. By definition, consistency is mandatory whereas automation is not. Distinguishing the consistency and automation aspects of RBDE assistance mechanisms makes it possible to formalize the range of compatible views and the scope of mechanizable evolution steps. Throughout the paper, we use the MARVEL RBDE as an example application.
PROJECT MANAGEMENT UTILIZING AN ADVANCED CASE ENVIRONMENT
Authors: BAKER JOHN M.
Published: November 2004

An advanced CASE environment would dramatically improve the analytic activities of a project manager. Management by exception will become more effective as the CASE environment generates warnings of abnormal situations. Participatory management will become more effective because, while team members will be able to create there own work tasks, the manager will be able to more accurately review the activities against plan.
THE EVOLUTION FROM SOFTWARE COMPONENTS TO DOMAIN ANALYSIS
Authors: NEIGHBORS JAMES M.
Published: November 2004

More than twenty years ago the idea of producing software systems from reusable software components was proposed. Since that time many changes have taken place in Computer Science and Software Engineering, but software systems are still built as one-of-a-kind craftsman efforts. A method for software construction using components is rationalized using experience from software components, program transformations, system architecture, industrial large systems, automatic programming and program generation. Experience with the method is discussed. The limiting factors of the method that prevent the widespread use of reusable software components are identified.
A RANDOMIZED ALGORITHM FOR SLOPE SELECTION
Authors: DILLENCOURT MICHAEL B. , MOUNT DAVID M. , NETANYAHU NATHAN S.
Published: November 2004

A set of n distinct points in the plane defines [Formula: see text] lines by joining each pair of distinct points. The median slope of these O(n2) lines was proposed by Theil as a robust estimator for the slope of the line of best fit for the points. We present a randomized algorithm for selecting the k-th smallest slope of such a set of lines which runs in expected O(n log n) time. An efficient implementation of the algorithm and practical experience with the algorithm are discussed.
VORONOI DIAGRAMS IN A RIVER
Authors: SUGIHARA KOKICHI
Published: November 2004

A new generalized Voronoi diagram is defined on the surface of a river with uniform flow; a point belongs to the territory of a site if and only if a boat starting from the site can reach the point faster than a boat starting from any other site. If the river runs slower than the boat, the Voronoi diagram has the same topological structure as the ordinary Voronoi diagram, and hence can be constructed from the ordinary Voronoi diagram by a certain transformation. If the river runs faster than the boat, on the other hand, the topological structure of the diagram becomes different from the ordinary one, but it can be constructed by the plane sweep technique. Moreover, Fortune’s plane sweep algorithm for constructing the ordinary Voronoi diagram can be interpreted as the algorithm for constructing the Voronoi diagram in a river in which the water flows at the same speed as the boat.
POLYNOMIAL-SIZE NONOBTUSE TRIANGULATION OF POLYGONS
Authors: BERN MARSHALL , EPPSTEIN DAVID
Published: November 2004

We describe methods for triangulating polygonal regions of the plane so that no triangle has a large angle. Our main result is that a polygon with n sides can be triangulated with O(n2) nonobtuse triangles. We also show that any triangulation (without Steiner points) of a simple polygon has a refinement with O(n4) nonobtuse triangles. Finally we show that a triangulation whose dual is a path has a refinement with only O(n2) nonobtuse triangles.
THE SOLUTION TO THE WORD PROBLEM FOR THE RELATIVELY FREE SEMIGROUPS SATISFYING Ta = Ta+b WITH a ≥ 6
Authors: McCAMMOND J.
Published: November 2004

In this article the word problem for certain Burnside semigroups is shown to be decidable. For each word W ∈ A* a nondeterministic, finite-state automaton is constructed. This automaton accepts a word iff it is equivalent to W under the relations Ta = Ta+b, where a and b are fixed positive integers and T is an arbitrary word in A*. The method decides the word problem for those cases where a ≥ 6. The maximal subgroups are shown to be cyclic groups of order b.
MONOID GROWTH FUNCTIONS FOR BRAID GROUPS
Authors: BRAZIL MARCUS
Published: November 2004

It is shown that for all n, the braid group on n strings, Bn, has rational growth with respect to a certain set of elements of the group which generate it as a monoid. In particular, the precise growth function for B4 is calculated.
COMBINATORIAL PROPERTIES OF UNIFORMLY RECURRENT WORDS AND AN APPLICATION TO SEMIGROUPS
Authors: DE LUCA ALDO , VARRICCHIO STEFANO
Published: November 2004

We prove some combinatorial properties of uniformly recurrent infinite words which can be expressed in terms of bi-ideal and n-divided sequences. A consequence of these results is an improvement of a theorem of Shirshov [13] and a new finiteness condition for finitely generated semigroups which generalizes both a theorem of Restivo and Reutenauer [12] and a theorem of de Luca and Restivo [4].
SEMIGROUPS WITH IDEMPOTENT STABILIZERS AND APPLICATIONS TO AUTOMATA THEORY
Authors: LE SAEC BERTRAND , PIN JEAN-ERIC , WEIL PASCAL
Published: November 2004

Nous prouvons que tout semigroupe fini est quotient d'un semigroupe fini dans lequel les stabilisateurs droits satisfont les identités x = x2 et xy = xyx. Ce resultat a plusieurs consé-quences. Tout d'abord, nous l'utilisons, en même temps qu'un résultat de I. Simon sur les congruences de chemins, pour obtenir une preuve purement algébrique d'un théorème profond de McNaughton sur les mots infinis. Puis, nous donnons une preuve algébrique d'un théorème de Brown sur des conditions de finitude pour les semigroupes.

We show that every finite semigroup is a quotient of a finite semigroup in which every right stabilizer satisfies the identities x = x2 and xy = xyx. This result has several consequences. We first use it together with a result of I. Simon on congruences on paths to obtain a purely algebraic proof of a deep theorem of McNaughton on infinite words. Next, we give an algebraic proof of a theorem of Brown on a finiteness condition for semigroups.
BINARY PATTERNS IN BINARY WORDS
Authors: GORALCIK PAVEL , VANICEK TOMAS
Published: November 2004

We strengthen the description of the 2-avoidable binary patterns given in J. Cassaigne [3], P. Roth [7], and Vanicek [8], by showing that every 2-avoidable binary pattern [t] can be avoided by an infinite independent set of binary words, and, the number of binary words avoiding [t] grows exponentially with their length.
MUTUALLY AVOIDING TERNARY WORDS OF SMALL EXPONENT
Authors: CROCHEMORE M. , GORALCIK P.
Published: November 2004

We construct, for every ε > 0, an infinite set Sε of words over a three letter alphabet such that every factor of a word in Sε has its exponent between 7/4 and 7/4 + ε, and, no word of Sε has for factor a homomorphic image of another word of Sε.
ASH'S TYPE II THEOREM, PROFINITE TOPOLOGY AND MALCEV PRODUCTS: PART I
Authors: HENCKELL KARSTEN , MARGOLIS STUART W. , PIN JEAN-ERIC , RHODES JOHN
Published: November 2004

This paper is concerned with the many deep and far reaching consequences of Ash's positive solution of the type II conjecture for finite monoids. After reviewing the statement and history of the problem, we show how it can be used to decide if a finite monoid is in the variety generated by the Malcev product of a given variety and the variety of groups. Many interesting varieties of finite monoids have such a description including the variety generated by inverse monoids, orthodox monoids and solid monoids. A fascinating case is that of block groups. A block group is a monoid such that every element has at most one semigroup inverse. As a consequence of the cover conjecture — also verified by Ash — it follows that block groups are precisely the divisors of power monoids of finite groups. The proof of this last fact uses earlier results of the authors and the deepest tools and results from global semigroup theory. We next give connections with the profinite group topologies on finitely generated free monoids and free groups. In particular, we show that the type II conjecture is equivalent with two other conjectures on the structure of closed sets (one conjecture for the free monoid and another one for the free group). Now Ash's theorem implies that the two topological conjectures are true and independently, a direct proof of the topological conjecture for the free group has been recently obtained by Ribes and Zalesskii. An important consequence is that a rational subset of a finitely generated free group G is closed in the profinite topology if and only if it is a finite union of sets of the form gH1H2…Hn, where g ∈ G and each Hi is a finitely generated subgroup of G. This significantly extends classical results of M. Hall. Finally, we return to the roots of this problem and give connections with the complexity theory of finite semigroups. We show that the largest local complexity function in the sense of Rhodes and Tilson is computable.
DETERMINISTIC AND NON-DETERMINISTIC ASYNCHRONOUS AUTOMATIC STRUCTURES
Authors: SHAPIRO MICHAEL
Published: November 2004

Following the definition of asynchronous automatic structures in [3], we define non-deterministic asynchronous automatic structures and characterize these in terms of the asynchronous fellow traveller property. We show that any group with a non-deterministic asynchronous automatic structure has an asynchronous automatic structure. Non-deterministic asynchronous automatic structures are a labor saving method of showing that a group has an asynchronous automatic structure. They also allow one to define an equivalence relation on the class of non-deterministic asynchronous automatic structures which descends to the subclasses of deterministic asynchronous automatic structures and synchronous automatic structures.
CORONA-POLED NONLINEAR POLYMERIC FILMS: IN SITU ELECTRIC FIELD MEASUREMENT, CHARACTERIZATION AND ULTRASHORT-PULSE APPLICATIONS
Authors: KNOESEN A. , MOLAU N.E. , YANKELEVICH D.R. , MORTAZAVI M.A. , DIENES A.
Published: November 2004

Electric poling at field intensities approaching the dielectric strength of the film is possible with corona poling. Polymeric thin films with large second-order nonlinearities can be created with this poling technique. In this paper, the corona poling of nonlinear polymeric films at elevated temperatures, processing, characterization and possible ultrashort-pulse applications are reviewed. An experimental technique is presented to measure the electric field during poling of the nonlinear polymeric film. The characterization of orientational order in corona-poled nonlinear polymeric films and the effects associated with the large electric field during poling are discussed. Poled polymeric thin films are uniquely suited for second-order nonlinear optical applications of ultrashort pulses (< 50 fsec) since minimal pulse spreading occurs. The sum-frequency ultrashort-pulse application of nonlinear polymeric thin films and limitations of the thin polymeric films are discussed. Experimental results are presented of a side-chain nonlinear polymer that is ideally suited for ultrashort-pulse applications.
STUDY OF TIME-DELAY FOUR-WAVE MIXING WITH INCOHERENT LIGHT IN ABSORPTION BANDS I: Theory
Authors: YE PEIXIAN , ZHANG RUIHUA , MI XIN , ZHOU HAITIAN , JIANG QIAN
Published: November 2004

A multilevel model, including homogeneous and inhomogeneous broadening, is proposed for the study of time-delay four-wave mixing with incoherent light (TDFWM-IL) in absorption bands consisting of a series of vibrational transitions. A theory of TDFWM-IL is developed for this model, and a general formula for the delay-time dependence of the signal intensity Is(τ), considering both the homogeneous and inhomogeneous broadening of the transitions, is deduced. Special analyses are given to the homogeneous and inhomogeneous limits. The differences between Is(τ) derived from multilevel theory and from two-level theory, are pointed out. When the homogeneous broadening of individual transitions is much smaller than the frequency interval of adjacent transitions, Is(τ) in the multilevel theory is modulated periodically and the envelope is close to that in the two-level theory for both the homogeneous and inhomogeneous limits. When the individual transitions are homogeneously broadened enough so that an unresolved continuous band is formed, an effective two-level model can still be used approximately for the studies of TDFWM-IL in this continuous band, with both homogeneous and inhomogeneous broadening. However, the dephasing time [Formula: see text] in the formula of Is(τ) in this effective two-level model is not the real dephasing time of an individual transition of the band, but the effective one which reflects the behavior of the whole band.
CERENKOV-TYPE OPTICAL SECOND-HARMONIC GENERATION IN ORGANIC-CRYSTALLINE CHANNEL WAVEGUIDES
Authors: KONDO TAKASHI , HASHIZUME NAOKI , TSUDA KEIJI , MORITA RYUJI , ITO RYOICHI , OGASAWARA NAGAATSU , UMEGAKI SHINSUKE
Published: November 2004

Cerenkov-type optical second-harmonic generation (SHG) in organic-crystalline waveguides has been investgated. Various techniques for the fabrication of organic-crystalline waveguides are described. Planar and channel waveguides have been fabricated using an organic nonlinear optical crystal (−)2-(α-methylbenzylamino)-5-nitropyridine (MBANP). Visible blue light has been obtained in an MBANP rib waveguide using a laser-diode source. Theoretical analysis of Cerenkov-type SHG in planar waveguides is made, and a simple analytic expression for second-harmonic power is derived. Optimum conditions for attaining high conversion efficiency are discussed on the basis of the theoretical calculations.
SPATIAL SEPARATION OF POLARIZATION COMPONENTS BY NONLINEAR BEAM RESHAPING IN A J=1 TO J=0 MEDIUM
Authors: BALLAGH R.J. , McCORD A.W.
Published: November 2004

The diffractive reshaping that circularly polarized light beams undergo when coupled in a medium of homogenously broadened J=1→J=0 atoms is shown to be sensitively dependent on applied magnetic fields. In zero field, an elliptically polarized beam will retain its polarization everywhere in space, but a small longitudinal magnetic field can cause the beam to break up into spatially distinct regions of pure circular polarization. The beam behavior can be understood in terms of an encoding/diffraction sequence. An analytic solution for the atomic response function reveals the important roles played by transverse and longitudinal optical pumping.
SELF-CONSISTENT PUMP DEPLETION METHOD TO DESIGN OPTICAL TRANSMISSION SYSTEMS AMPLIFIED BY BIDIRECTIONAL RAMAN PUMPS
Authors: WEN SENFAR , WANG TSUN-YEE , CHI SIEN
Published: November 2004

The self-consistent pump depletion (SCPD) method is proposed to numerically solve the complete set of the coupled equations governing the signal and Raman pump powers in the unidirectional and bidirectional signal transmission systems. The maximum transmission lengths under the requirement of some minimum signal power for unidirectional and bidirectional signal transmission systems are studied. It is found that the maximum length decreases as the bit rate increases. With the same fiber loss of the signal wave, the optimum pump power and maximum transmission length for different fiber losses of the pump waves are shown for 1 Gbits/sec transmission system.
TUNABLE MID-INFRARED SOURCES USING SECOND-ORDER NONLINEARITIES
Authors: BARNES NORMAN P.
Published: November 2004

Tunable mid-infrared sources can be created using crystals having second-order non-linearities and solid-state lasers operating in the near infrared. Such devices have already demonstrated large tuning ranges and high efficiency. Performance of these devices as well as their potential for higher output energies and narrow spectral bandwidth operation are analyzed in terms of nonlinear crystal properties and solid-state laser requirements.
NONLINEAR OPTICAL ABSORPTION BY INTERACTION BETWEEN INTERBAND- AND INTRABAND-RESONANT LIGHTS IN n-DOPED QUANTUM WELL STRUCTURE
Authors: NODA SUSUMU , OKUDA TETSURO , YAMASHITA TAKAO , SASAKI AKIO
Published: November 2004

Nonlinear optical absorption for interband-resonant light by intraband-resonant light in n-doped quantum well structure is experimentally demonstrated. The nonlinearity is caused by the third-order interaction between interband- and intraband-resonant lights through a guided-wave structure. The amount of absorption for interband-resonant light is increased by 60% with the incidence of intraband-resonant light of 100–200 kW/cm2.
THE INFLUENCE OF A CUBIC DENSITY LAW ON PATTERNED GROUND FORMATION
Authors: McKAY G. , STRAUGHAN B.
Published: November 2004

A theoretical analysis is presented for the formation of polygonal ground which consists of stone borders forming regular hexagons with soil centers. The model is based on the onset of convection in a saturated soil below which is a cold permafrost layer. Darcy’s law is adopted with zero fluid inertia and the density is assumed constant except in the buoyancy term. In this term we take the equation of state proposed by Merker et al.,5 this being the one which assumes the density has a cubic dependence on temperature. Theoretical predictions of the model, particularly those for width to depth of the patterned ground cell are reported in detail.
DISPERSIVE GROUNDWATER FLOW AND POLLUTION
Authors: VAN HERWAARDEN ONNO A. , GRASMAN JOHAN
Published: November 2004

By solving asymptotically the Dirichlet problem for the backward Kolmogorov equation describing the random walk of a particle in a dispersive flow, it is computed at what rate contaminated particles cross the boundary of a protected zone. The method also yields an estimate of the expected arrival time.
THE ONE-DIMENSIONAL PERIODIC BLOCH-POISSON EQUATION
Authors: ARNOLD ANTON , MARKOWICH PETER A. , MAUSER NORBERT
Published: November 2004

We analyze the Bloch-Poisson model describing quantum steady states of electrons in thermodynamical equilibrium. The problem is set in a one-dimensional periodic geometry. The existence of a unique smooth solution for every positive temperature is proved, a convergent iterative procedure useful for the numerical simulation is obtained, and the classical limit is analyzed.
A NONLINEAR INVERSE PHASE TRANSITION PROBLEM FOR THE HEAT EQUATION
Authors: PREZIOSI L. , DE SOCIO L.M.
Published: November 2004

This paper proposes a method for the solution of two inverse problems which are governed by the nonlinear heat equation in one space dimension. In the first case phase transition occurs at the moving interface which divides two media. In the second one a random heat source is placed at a moving point. In both cases the temperature is assigned, as a function of time and within a random error, at a given fixed point. The solution procedure leads to quantitative results and is based on the Stochastic Adaptative Interpolation method.
UPPER BOUNDS AND APPROXIMATION FOR THE SOLUTION OF A NONLINEAR PARTICLE TRANSPORT PROBLEM WITH MAXWELL TYPE BOUNDARY CONDITIONS
Authors: TOTARO SILVIA
Published: November 2004

We consider a nonlinear particle transport problem in a slab of thickness 2a with Maxwell-type boundary conditions. The nonlinearity is due to the presence of a scattering term, which is a quadratic function of the (unknown) particle density u(t)=u(x, y; t).

We first prove that, under suitable assumptions, the integral version of the transport equation has a unique strongly continuous solution u=u(t)∈L1∩L∞, defined over an arbitrary fixed time interval [0, t0]. We also evaluate upper bounds for the norms ||u(t)|| and ||u(t)||∞, which are useful to understand the mathematical and the physical properties of the particle transport problem under consideration.

Finally, we discretize the angle variable y in the unknown function u(t)=u(x, y; t), (i.e., we use the “discrete ordinate method”) and we prove the convergence of the discretized solution to the exact solution by using a generalization of Trotter’s theory on sequences of Banach spaces approximating a given Banach space.
STATISTICAL SOLUTIONS OF NAVIER-STOKES EQUATIONS BY NONSTANDARD DENSITIES
Authors: CAPIŃSKI MAREK , CUTLAND NIGEL
Published: November 2004

We present a method of constructing nonstandard densities of measures living on infinite-dimensional spaces. This gives the existence of statistical solutions of Navier-Stokes equations as standard measures corresponding to the solution of a first order PDE for the nonstandard densities. For linear equations the method gives a simple proof of uniqueness of statistical solutions.
DOMAIN DECOMPOSITION APPROXIMATION TO A GENERALIZED STOKES PROBLEM BY SPECTRAL METHODS
Authors: CARLENZOLI CLAUDIO , ZANOLLI PAOLA
Published: November 2004

We consider here the approximation of a generalized Stokes problem by spectral methods in the collocation form. This problem is of particular interest when Navier-Stokes equations for viscous compressible flows are investigated.

We also analyze a coupling of a viscous model with an inviscid one; precisely, we split the computational domain in two parts and in one of them we eliminate the viscous coefficient from the Stokes equations. Such an approach can be worthwhile in the study of compressible fluids around rigid profiles with critical layers.

Finally we consider some numerical results with the aim of showing the excellent accuracy of the spectral approximations, as well as the efficiency of an iterative algorithm that we propose in order to alternate viscous and inviscid numerical solvers.
APPROXIMATING THE BROADWELL MODEL IN A STRIP
Authors: GABETTA ESTER , PARESCHI LORENZO
Published: November 2004

In this paper a discretization of the continuous reduced Broadwell model in a strip is proposed. The simulation is performed to investigate also numerically the large time behavior of the solution. The trend towards the uniform state is proven for our iterative scheme, and the approximation of the solution of the complete model to the solution of our discretization is stated.
THE APPLICATION OF COMPOUND MATRICES TO CONVECTION PROBLEMS IN MULTI-LAYERED CONTINUA
Authors: LINDSAY K.A.
Published: November 2004

This work describes how the Compound Matrix technique can be successfully extended to the solution of eigenvalue problems in multi-layered continua. The ideas are supported by applications to convection in regions which are laminated by either conducting barriers or porous barriers.
AN ACCURATE EVALUATION OF THE DISTRIBUTION FUNCTIONS OF NONLINEAR EXTENDED KINETIC THEORY
Authors: GANAPOL B.D. , SPIGA G. , ZANETTE D.H.
Published: November 2004

The solution to the nonlinear spatially independent Boltzmann equation of extended kinetic theory is numerically evaluated for Maxwellian background and constant collision frequencies. The method of continuous analytical continuation is shown to provide highly accurate numerical solutions.
EXPONENTIAL STABILITY OF STATIONARY SOLUTIONS TO THE DISCRETE BOLTZMANN EQUATION IN A BOUNDED DOMAIN
Authors: KAWASHIMA SHUICHI
Published: November 2004

Large-time behavior of solutions of the discrete Boltzmann equation in a bounded domain is studied. The boundary conditions considered are pure diffuse relection and general reflection.

Under suitable assumptions it is proved that a unique solution exists globally in time and converges to the corresponding unique stationary solution exponentially as time goes to infinity. The crucial point of the proof is in the derivation of desired boundary estimates of the solution subordinate to the general reflection.
SOME BOUNDS ON THE BULK CONDUCTIVITY OF A TWO-PHASE MEDIUM: A COMPARISON BETWEEN PERIODIC AND RANDOM STRUCTURE
Authors: GAVIOLI ANDREA
Published: November 2004

We prove that the effective conductivity of a three-dimensional medium with a periodic chessboard structure does not exceed [Formula: see text] where α and β are the values of the conductivity in the cells of the chessboard, and A is a positive constant; then we show how the corresponding “random” structure behaves in a quite different way, according to recent results in percolation theory.
JUSTIFICATION OF A REFINED SCALING OF STIFFNESSES OF REISSNER PLATES WITH FINE PERIODIC STRUCTURE
Authors: TELEGA JÓZEF JOACHIM
Published: November 2004

The aim of this paper is a rigorous justification of the model of linear elastic plates proposed in Ref. 19. Such a model is obtained by rescaling stiffnesses and performing homogenization of a Reissner plate exhibiting fine periodic structure. To prove convergence, when the periodicity parameter tends to zero, the epi-convergence method is applied; the proof of convergence essentially exploits duality arguments. The dual homogenization, based on the principle of the complementary energy, is also studied; the properties of the macroscopic potential are investigated and the dual homogenized (macroscopic) potential is derived.
POROUS PENETRATIVE CONVECTION WITH A SALT FIELD AND INTERNAL HEAT SOURCE
Authors: RICHARDSON LORNA
Published: November 2004

We investigate the stability of convection in a porous medium containing a heat source in which a destabilizing salt field and stabilizing temperature gradient are present. Both conditional and unconditional nonlinear stability thresholds are calculated and we note that RaE(conditional)>RaE(unconditional). The unconditional nonlinear analysis requires the use of a “weighted” energy.
PRODUCTION-GRAPH: A GRAPH THEORETICAL MODEL FOR CHECKING KNOWLEDGE BASE ANOMALIES
Authors: LIM ENG LIAN , McCALLUM JOHN , CHAN KWOK HUNG
Published: November 2004

Knowledge acquisition is tedious and error-prone. Consequently, a knowledge base may be inconsistent, and contains unreachable rules, redundant rules, and rules which may lead to deadends and infinite loops. There are three approaches for checking these anomalies: interactive, non-interactive pairwise and non-interactive pathwise. In this article, we will present a graph theoretical model called Production-graph for checking knowledge base anomalies along the non-interactive pathwise approach. Production-graph uses graph theoretical constructions to represent facts and rules, as well as relevant properties of the knowledge base that leads to anomalies. Distinctive features of Production-graph include: (i) Using Production-graph, we are able to check on groups of problem instances rather than on individual problem instances. This eliminates the problem of having infinitely many problem instances. (ii) Empirical knowledge is used to limit the problem instances to practically realizable problems. (iii) Effects of chaining both rules and facts are considered.