bluuebunny/crossref_metadata_2025 huggingface dataset:
SCALABLE ALGORITHMS FOR BICHROMATIC LINE SEGMENT INTERSECTION PROBLEMS ON COARSE GRAINED MULTICOMPUTERS
Authors: FABRI ANDREAS , DEVILLERS OLIVIER
Published: September 2004

We present output-sensitive scalable parallel algorithms for bichromatic line segment intersection problems for the coarse grained multicomputer model. Under the assumption that n≥p2, where n is the number of line segments and p the number of processors, we obtain an intersection counting algorithm with a time complexity of [Formula: see text], where Ts(m, p) is the time used to sort m items on a p processor machine. The first term captures the time spent in sequential computation performed locally by each processor. The second term captures the interprocessor communication time. An additional [Formula: see text] time in sequential computation is spent on the reporting of the k intersections. As the sequential time complexity is O(n log n) for counting and an additional time O(k) for reporting, we obtain a speedup of [Formula: see text] in the sequential part of the algorithm. The speedup in the communication part obviously depends on the underlying architecture. For example for a hypercube it ranges between [Formula: see text] and [Formula: see text] depending on the ratio of n and p. As the reporting does not involve more interprocessor communication than the counting, the algorithm achieves a full speedup of p for k≥ O( max (n log n log p, n log 3 p)) even on a hypercube.
COMPUTATIONAL GEOMETRY COLUMN 29
Authors: O’ROURKE JOSEPH
Published: September 2004

Past accomplishments of Computational Geometry are reviewed and future directions adumbrated.
BEHAVIOR OF SMALL FINITE ELEMENT STRUCTURES FOR THE NAVIER–STOKES EQUATIONS
Authors: GOUBET OLIVIER
Published: September 2004

This article deals with the long-time behavior of the solution of the two-dimensional Navier–Stokes equations. At each time step, we use finite elements to split the solution into a large-scale component and a small-scale component, and we follow both components in time. Next, considering a mixed finite element approximation of the equations, we prove that many properties that hold for the exact solution extend to the discrete solution as well, uniformly in the discretization parameter.
A POSTERIORI ERROR ESTIMATORS VIA BUBBLE FUNCTIONS
Authors: RUSSO ALESSANDRO
Published: September 2004

In this paper we discuss a way to recover a classical residual-based error estimator for elliptic problems by using a finite element space enriched with bubble functions. The advection-dominated case is also discussed.
INEXACT NEWTON METHODS FOR THE STEADY STATE ANALYSIS OF NONLINEAR CIRCUITS
Authors: GUGLIELMI NICOLA
Published: September 2004

In this paper numerical problems arising from steady state analysis of nonlinear circuits with quasiperiodic excitation are discussed. The approach we consider is based on the piecewise harmonic balance techniques8,9 (HB), a methodology which has its theoretical foundations in Galerkin's procedure (see the paper by Urabe12).

The original problem, which can be expressed in the form of a system of integro-differential equations in the time domain, is changed into a nonlinear algebraic system through a natural projection technique. Thus, one of the main issues we have investigated consists in the numerical solution of the specific nonlinear algebraic problem.
EXISTENCE OF A GLOBAL ATTRACTOR FOR THE SLIGHTLY COMPRESSIBLE 2-D NAVIER–STOKES EQUATIONS IN THE CASE OF A THERMOHYDRAULIC PROBLEM
Authors: NJAMKEPO SERGE
Published: September 2004

A theorem by J. M. Ghidaglia and R. Temam shows the existence and finitness of attractors for 2-D Navier–Stokes equations for a sligthly compressible fluid. In this paper we extend their result to the equations of thermohydraulic for the same fluid.
RKH SPACE METHODS FOR LOW LEVEL MONITORING AND CONTROL OF NONLINEAR SYSTEMS
Authors: COVER ALAN , RENEKE JAMES , FRYER MICHAEL , LENHART SUZANNE , PROTOPOPESCU VLADIMIR
Published: September 2004

A monitor or controller is smart provided that the device is equipped with local computational resources for analyzing data, detecting changes, and making decisions. The problem for the monitoring function is to design algorithms to flag model shifts for dynamic systems in a context requiring many interacting system components and system reconfigurations. The problem for the control function is to improve system performance by updating control feedbacks after the model shift has been detected. Therefore it is desirable that smart monitors and controllers be adaptive and update with minimal intervention from a central director.

We present here an approach to designing smart monitoring and control devices based on a stochastic linearization of the system whose dynamics is noisy and unknown. This linearization is obtained by factoring the discrete system covariance matrix, estimated from observations, and applying reproducing kernel Hilbert space techniques. The method is nonparametric which allows the smart devices to operate with only a low level logic.
WEIGHTED Lq-SOLVABILITY OF THE STEADY STOKES SYSTEM IN DOMAINS WITH NONCOMPACT BOUNDARIES
Authors: PILECKAS K.
Published: September 2004

The stationary Stokes equations of a viscous incompressible fluid are considered in domains Ω with m > 1 exits to infinity, which have in some coordinate system the following form: [Formula: see text] where gi are functions satisfying the global Lipschitz condition and [Formula: see text] as xn→ ∞. The solvability of the Stokes system with prescribed fluxes is investigated in weighted Sobolev spaces, which are generated by different weighted L q norms.
SECOND-ORDER SCHEME FOR THE SPATIALLY HOMOGENEOUS BOLTZMANN EQUATION WITH MAXWELLIAN MOLECULES
Authors: STRUCKMEIER JENS , STEINER KONRAD
Published: September 2004

In the standard approach particle methods for the Boltzmann equation are obtained using an explicit time discretization of the spatially homogeneous Boltzmann equation. This kind of discretization leads to a restriction on the discretization parameter as well as on the differential cross-section in the case of the general Boltzmann equation. Recently, construction of an implicit particle scheme for the Boltzmann equation with Maxwellian molecules was shown.

This paper combines both approaches using a linear combination of explicit and implicit discretizations. It is shown that the new method leads to a second-order particle method when using an equiweighting of explicit and implicit discretization.
ON THE CAUCHY PROBLEM FOR SOME PSEUDO-DIFFERENTIAL EQUATIONS OF SCHRÖDINGER TYPE
Authors: AGLIARDI R. , MARI D.
Published: September 2004

A fundamental solution of the Cauchy problem is constructed for a pseudo-differential equation generalizing some Schrödinger equations. Then well-posedness of the Cauchy problem is proved in some Gevrey spaces whose indices depend on the lower order term of the operator.
ASYMPTOTIC DECAY TOWARD THE PLANAR RAREFACTION WAVES OF SOLUTIONS FOR VISCOUS CONSERVATION LAWS IN SEVERAL SPACE DIMENSIONS
Authors: ITO KAZUO
Published: September 2004

This paper gives the asymptotic decay rate toward the planar rarefaction waves of the solutions for the scalar viscous conservation laws in two or more space dimensions. This is proved by a result on the decay rate of solutions for one-dimensional scalar viscous conservation laws and by using an L2-energy method with a weight of time.
ON THE CONVERGENCE OF A TRIANGULAR MIXED FINITE ELEMENT METHOD FOR REISSNER–MINDLIN PLATES
Authors: DURÁN RICARDO G. , LIBERMAN ELSA
Published: September 2004

We analyze the convergence of a mixed finite element method introduced by Zienkiewicz, Taylor, Papadopoulos and Oñate for the Reissner–Mindlin plate model. In order to do this, we compare it with a method which is known to be convergent with optimal order uniformly in the plate thickness. We show that the difference between the solutions of both methods is of higher order than the error. In particular the method does not present locking and is optimal order convergent. We also present several numerical experiments which confirm the similar behavior of both methods.
ON NEW ADDITIVE DIFFERENCE METHOD FOR PARABOLIC EQUATIONS
Authors: KARAMZIN YU. N. , ZAKHAROVA I. G.
Published: September 2004

A new approach is suggested to the construction of conservative difference schemes for multidimensional second-order parabolic equations containing divergent first-order differential forms. These schemes hold the property of having fixed sign for non-negative solutions. The convergence of schemes is proved in the grid norm L2 at the rate O(τ + h2).
ON THE STABILITY OF A STELLAR STRUCTURE IN ONE DIMENSION
Authors: DUCOMET B.
Published: September 2004

We describe in this paper the stability of the interface in a free-boundary problem for a self-gravitating gas in one space dimension, with an external pressure P, and a Fourier coefficient λ, for the thermal flux.

In the first part, we consider the pure gaseous limit (perfect gas), and we find different possible asymptotic behaviors: if λ > 0, the gas tends to collapse; if λ = 0, we show that, when P > 0, the solution converges, for large time to the isothermal solution of the corresponding stationary problem, while for P = 0, the system is unstable, and the gas tends to fill all the space.

In the second part, we consider the same problem for the pure radiative limit (photon gas), and we show that analogous asymptotics hold.
ENERGY STABILITY OF A STATIONARY CONDUCTING THERMOMICROPOLAR FLUID LAYER UNDER THE INFLUENCE OF A MAGNETIC FIELD
Authors: CALMELET-ELUHU COLETTE J.
Published: September 2004

The effect of an orthogonal applied magnetic field on an electrically conducting thermomicropolar fluid layer which is heated from below, is investigated. The linear stability and the nonlinear stability of the stationary state are considered when the fluid layer lies between two nonconducting rigid boundaries. The nonlinear stability study is performed for different cases of the Alfven No. A which depends on the strength of the magnetic field. A generalized energy is used for the general case A different from 1. From a variational and numerical analysis the nonlinear stability threshold is obtained and compared with the linear stability results and the nonconducting case. Both micro-rotation and magnetic field tend to stabilize the fluid layer.
THE ASYMPTOTICS OF COLLISION OPERATORS FOR TWO SPECIES OF PARTICLES OF DISPARATE MASSES
Authors: DEGOND PIERRE , LUCQUIN-DESREUX BRIGITTE
Published: September 2004

We analyze the dynamics of a disparate mass binary gas or of a plasma in the homogeneous case, at various time scales, in the framework of the Boltzmann or Fokker–Planck equation. We intend to provide a rigorous foundation to the epochal relaxation phenomenon first pointed out by Grad. From general basic physical hypotheses, we derive the scaling of the equations as a function of the mass ratio of the particles, and we expand the collision operators in powers of this mass ratio. Then, Hilbert or Chapman–Enskog type expansions of the distribution functions allow us to investigate the dynamics of the mixture at various time scales, and we verify that the behavior of the obtained models is coherent with Grad's hypothesis.
A DECOMPOSITION THEOREM FOR WAVE FUNCTIONS IN MOLECULAR QUANTUM CHEMISTRY
Authors: BOKANOWSKI O. , GREBERT B.
Published: September 2004

A general way to decompose an antisymmetric wave function into its density function and a wave function of a given density is proposed. Its usefulness for molecular quantum chemistry is discussed, in particular in the context of density functional theory.
A SLIP CONDITION BASED ON MINIMAL ENERGY DISSIPATION
Authors: KITRON-BELINKOV MYRA , NOVICK-COHEN AMY , LIRON NADAV
Published: September 2004

An intrinsic difficulty arises when solving Stokes equations in Ω ⊂ ℝ2 when the boundary conditions on the velocity are discontinuous: the solution is physically unacceptable since the force exerted by the fluid on the boundary is logarithmically singular. To illustrate this phenomena, we present an explicit solution in which the logarithmic singularity appears in a particularly simple form. A common method of avoiding the appearance of these singular forces is via an alteration of the boundary velocity profile in the vicinity of the discontinuity. However, there is no obvious physical criterion according to which the velocity profile along the boundary should be chosen. We consider a possible physically motivated criterion based on minimal energy dissipation. We prove the existence of a unique minimizing profile and demonstrate that the resultant velocity field does indeed exert a finite force along the boundary. Lastly, the minimizing profile is calculated numerically and the effect of free parameters is considered.
ABSORBING BOUNDARY CONDITIONS IN BLOCK GAUSS–SEIDEL METHODS FOR CONVECTION PROBLEMS
Authors: NATAF FREDERIC
Published: September 2004

In the context of convection-diffusion equation, the use of absorbing boundary conditions (also called radiation boundary conditions) is considered in block Gauss–Seidel algorithms. Theoretical results and numerical tests show that the convergence is thus accelerated.
LIMIT THEOREMS FOR DETERMINISTIC KNUDSEN FLOWS BETWEEN TWO PLATES
Authors: BABOVSKY HANS
Published: September 2004

We investigate the model dynamics of a test particle which moves between two parallel plates and is reflected at the walls according to some deterministic periodic reflection law. For a particular continuous velocity model, a diffusion limit is derived using the Markov partition approach. It is shown that at least for a large class of discrete velocity models such a limit is not possible. Numerical aspects are discussed.
WELL-POSEDNESS OF A MIXED INITIAL–BOUNDARY VALUE PROBLEM FOR VIBRATING ELASTIC SYSTEMS
Authors: YU WENHUAN
Published: September 2004

In this letter we consider the well-posedness of a mixed initial–boundary value problem for a vibrating elastic system, which describes the dynamics of a kind of flexible robot with an elastic link, a rigid link, and three rotation axes. The governing equations consist of two nonlinear partial differential equations of order four and three nonlinear integro-differential equations. Using the semigroup theory, we prove that the above-mentioned problem is well-posed, i.e. there is a unique classical solution that continuously depends on the initial data.
ACCURATE PARALLEL INTEGRATION OF LARGE SPARSE SYSTEMS OF DIFFERENTIAL EQUATIONS
Authors: ESTEP DONALD J. , WILLIAMS ROY D.
Published: September 2004

We describe a MIMD parallel code to solve a general class of ordinary differential equations, with particular emphasis on the large, sparse systems arising from space discretization of systems of parabolic partial differential equations. The main goals of this work are sharp bounds on the accuracy of the computed solution and flexibility of the software.

We discuss the sources of error in solving differential equations, and the resulting constraints on time steps. We also discuss the theory of a posteriori error analysis for the Galerkin finite element methods, and its implementation in error control and estimation.

The software is designed in a matrix-free fashion, which enables the solver to effectively tackle large sparse systems with minimal memory consumption and an easy and natural transition to MIMD (distributed memory) parallelism. In addition, there is no need for the choice of a particular representation of a sparse matrix. All memory is dynamically allocated, with a new expandable array object used for archiving results.

The implicit solution of the discrete equations is carried out by replaceable modules: the nonlinear solver module may be a full Newton scheme or a quasi-Newton; these in turn are implemented with a linear solver, for which we have used both a direct solver and QMR, an iterative (Krylov space) method.

Three computations are presented: the Lorenz system, which has dimension three and the discretized versions of the (partial-differential) bistable equation in one and two dimensions. The Lorenz system demonstrates the quality of the error estimation. The discretized bistable examples provide large sparse systems, and our precise error estimation shows, contrary to standard error estimates, that reliable computation is possible for large times.
GEOMETRIC SINGULARITY ON THE LATERAL EDGE OF A BENDING PLATE
Authors: TITEUX I.
Published: September 2004

The aim of this paper is to improve the description of the stress field near a geometric perturbation of the lateral edge of a laminated plate. The main results concerning the bending of laminated plates and the two-dimensional problem are obtained by the asymptotic expansion theory. We then recall the boundary layer theory which allows us to improve the stress field close to a classical edge. After these preliminaries, we show how to modify the classical boundary layer theory to prove the existence and uniqueness of a corrective stress field.
ERRORS OF FINITE ELEMENT METHOD FOR PERFECTLY ELASTO-PLASTIC PROBLEMS
Authors: REPIN SERGEY I.
Published: September 2004

This paper discusses convergence of the finite element method for variational problems of the Hencky plasticity theory. To obtain a priori convergence estimates we use the method of “double approximation”. In the framework of this approach perfectly elastoplastic problem is approximated by some regularized problem. Hence, finite element solutions of the regularized problem depend on the regularization parameter δ and the mesh parameter h. For these solutions we obtain a projection type error estimate. This estimate is a sum of the two parts which represent the errors of regularization and discretization, respectively. Then we prove that under some assumptions on the external data the minimizer of the regularized problem and the maximizer of its dual problem possess additional differentiability properties and deduce the corresponding estimates which explicitly depend on the parameter δ. This makes it possible to prove that there is a dependence between δ and h such that piecewise-affine continuous approximations of the regularized problems generate a sequence of tensor valued functions which converges to the exact solution of the Hencky plasticity problem.
A MINIMIZATION ALGORITHM FOR A RELAXED ENERGY CONNECTED WITH THE THEORY OF LIQUID CRYSTALS
Authors: QUIVY L.
Published: September 2004

Bethuel, Brezis and Coron have recently proposed a modified energy (the so-called relaxed energy) in order to address the gap phenomenon discovered by Hardt and Lin. In this paper, our goal is to investigate from the numerical point of view the behavior of this energy for which the question of regularity is open. Results presented supports the conjecture that minimizers are indeed regular.
ELECTRODIFFUSIONAL FREE BOUNDARY PROBLEM IN CONCENTRATION POLARIZATION IN ELECTRODIALYSIS
Authors: RUBINSTEIN I. , ZALTZMAN B.
Published: September 2004

A singular perturbation problem, modeling one-dimensional time-dependent electrodiffusion in an electrolyte layer flanked by charge-selective walls (electrodes, ion-exchange membranes), is analyzed for galvanostatic (fixed electric current) conditions. It is shown that, as the perturbation parameter tends to zero, the solution of the perturbed problem tends to the solution of a certain limiting problem which is, depending on the input data, either a conventional diffusion problem or a diffusional free boundary problem equivalent to the one-phase Stefan problem with superheating. Spatial boundary layers in the perturbed problem are analyzed in both cases, together with the extended space charge zone which develops for electric currents above a certain critical (“limiting”) value. In this framework, the relaxational, vanishing at steady state, components of the ionic fluxes are being introduced and evaluated along with the respective parts of the electrochemical potentials of the ions. The analysis is constructive and yields, in particular, the explicit ionic concentration and electric potential profiles in the typical regions in the system.
BESOV NORMS IN TERMS OF THE CONTINUOUS WAVELET TRANSFORM. APPLICATION TO STRUCTURE FUNCTIONS
Authors: PERRIER VALÉRIE , BASDEVANT CLAUDE
Published: September 2004

The continuous wavelet transform is extended to Lp spaces and an inversion formula is demonstrated. From this the Besov spaces can be characterized by the behavior at small scales of the wavelet coefficients. These results apply to the measurement of structure functions.
OPTIMAL CONTROL OF THE BLOWUP TIME OF A DIFFUSION
Authors: BARRON E.N. , JENSEN R. , LIU W.
Published: September 2004

If we have a controlled Markov diffusion which may explode in finite time, the problem arises regarding using the control in order to maximize the mean time to explosion, i.e. the blowup time. The maximal mean blowup time, u(x), as a function of the initial position x∈ℝn is characterized as the unique continuous viscosity solution of a Bellman equation, satisfying the boundary condition that u vanishes at infinity. Then we consider the problem of convergence of the maximal mean blowup time uε(x) corresponding to a diffusion matrix [Formula: see text], as ε → 0. We establish that, in general, the stochastic mean blowup time does not converge to the deterministic blowup time. However, the certainty equivalent blowup time does converge to the deterministic blowup time.
ERROR ESTIMATES AND ADAPTIVE FINITE ELEMENTS FOR NONLINEAR DIFFUSION-CONVECTION PROBLEMS
Authors: MEDINA JULIO , PICASSO MARCO , RAPPAZ JACQUES
Published: September 2004

A priori and a posteriori error estimates are presented for nonlinear diffusion-convection problems when using the classical Streamline Upwind Petrov-Galerkin (SUPG) scheme and numerical integration. For this purpose, an abstract framework is developed. A priori estimates are derived in the H1 and L2 norms and the error is bounded above and below by an estimator based on the equation residual. An adaptive algorithm requiring the generation of successive Delaunay triangulations is proposed and numerical results confirm the efficiency of our approach.
ON THE MAXIMUM MODULUS THEOREM IN LINEAR ELASTOSTATICS FOR EXTERIOR DOMAINS
Authors: STARITA GIULIO
Published: September 2004

This paper deals with the system of linear elastostatics in exterior three-dimensional domains. We prove that the modulus of every solution with finite energy of such a system may be majorized by a positive constant times the maximum value of the modulus of the Dirichlet data at the boundary (maximum modulus theorem).
MATHEMATICAL ANALYSIS FOR COMPRESSIBLE MISCIBLE DISPLACEMENT MODELS IN POROUS MEDIA
Authors: AMIRAT Y. , HAMDACHE K. , ZIANI A.
Published: September 2004

We discuss a three-dimensional displacement model of one miscible compressible fluid by another in a porous medium. The motion is modeled by a nonlinear system of parabolic type coupling the pressure and the concentration. We give an existence result of weak solutions for a model with diffusion and dispersion, using the Schauder fixed point theorem. We also study a model in the absence of diffusion and dispersion. The system becomes of parabolic-hyperbolic type, the existence of global weak solutions is then obtained through a compensated compactness argument.
BIORTHOGONAL SPLINE WAVELETS ON THE INTERVAL FOR THE RESOLUTION OF BOUNDARY PROBLEMS
Authors: MASSON ROLAND
Published: September 2004

We construct biorthogonal spline wavelets on the interval for different spline orders. We then discuss the accuracy of the construction and test the wavelet transform. Building the corresponding wavelet basis for [Formula: see text] boundary conditions we use it for the resolution of elliptic boundary problems both with pure Galerkin and Petrov-Galerkin schemes. The results are compared from stability and convergence points of view. The main conclusion is that using the biorthogonal counterpart of spline functions as trial spaces for low order splines provides much more advantages than using spline functions themselves as trial spaces for high order splines.
NUMERICAL EVIDENCE OF FATTENING FOR THE MEAN CURVATURE FLOW
Authors: FIERRO FRANCESCA , PAOLINI MAURIZIO
Published: September 2004

In this paper we describe some numerical simulations in the context of mean curvature flow. We recover a few different approaches in modeling the evolution of an interface Σ which evolves according to the law: V=κ+g where V is the velocity in the inward normal direction, κ is the sum of the principal curvatures and g is a given forcing term. We will discuss about the phenomenon of fattening or nonuniqueness of the solution, recalling what is known about this subject. Finally we show some interesting numerical simulations that suggest evidence of fattening starting from different initial interfaces. Of particular interest is the result obtained for a torus in ℝ4 which would be a first example of a regular and compact surface showing evidence of fattening in the case of pure motion by mean curvature (no forcing term).
TWO-PHASE BINARY FLUIDS AND IMMISCIBLE FLUIDS DESCRIBED BY AN ORDER PARAMETER
Authors: GURTIN MORTON E. , POLIGNONE DEBRA , VIÑALS JORGE
Published: September 2004

A unified framework for coupled Navier-Stokes/Cahn-Hilliard equations is developed using, as a basis, a balance law for microforces in conjunction with constitutive equations consistent with a mechanical version of the second law. As a numerical application of the theory, we consider the kinetics of coarsening for a binary fluid in two space dimensions.
THE MATHEMATICS OF PRINCIPAL VALUE INTEGRALS AND APPLICATIONS TO NUCLEAR PHYSICS, TRANSPORT THEORY, AND CONDENSED MATTER PHYSICS
Authors: DAVIES K.T.R. , GLASSER M.L. , PROTOPOPESCU V. , TABAKIN FRANK
Published: September 2004

A review of developments in the mathematics and methods for principal value (PV) integrals is presented. These topics include single-pole formulas for simple and higher-order PVs, simple and higher-order poles in double integrals, and products of simple poles in general multiple integrals. Two generalizations of the famous Poincaré-Bertrand (PB) theorem are studied. We then review the following topics: dispersion relations for the advanced, retarded, and causal Green’s functions; Titchmarsh’s theorem; applications of the PB theorem to two- and three-particle loop integrals; and the R and T matrix formalism. Also, various applications of the PV methods to nuclear physics, transport theory, and condensed matter physics are studied. In the appendices several methods for evaluating PV integrals, including the Haftel-Tabakin procedure for calculating the R and T matrices, are reviewed.
STUDY OF AN APPROXIMATION MODEL ISSUED FROM PLASMA PHYSICS AND QUASINEUTRALITY
Authors: FABRE SYLVIE
Published: September 2004

In this paper, we study the existence and uniqueness in ℝN of Poisson’s equation coupled with Boltzmann’s relation which gives a particular expression of the electron’s density. We also consider the case where the ionic density vanishes. At last, an asymptotic analysis yields a proof of the quasineutrality hypothesis of this model where the Debye length can be neglected in comparison with the size of the system.
SOME CASES OF HOMOGENIZATION OF LINEARLY COERCIVE GRADIENT CONSTRAINED VARIATIONAL PROBLEMS
Authors: ARCANGELIS RICCARDO DE , GAUDIELLO ANTONIO , PADERNI GABRIELLA
Published: September 2004

A homogenization problem for integral functionals defined on Lipschitz functions verifying pointwise oscillating constraints on the gradient is studied in the case in which the constraint takes only the values 0 and +∞. Such situation is of interest in some problems in electrostatics and elastic-plastic torsion theory. An integral representation result on BV-spaces for the “homogenized functional”, and convergence results for minimum values and solutions of Dirichlet and Neumann problems, are proved without assuming any geometrical condition on the set of the zeroes of the constraint and under mild assumptions on the integrands. An application to a concrete problem in electrostatics is also given.
HOMOGENIZATION AND TWO-SCALE CONVERGENCE FOR A STOKES OR NAVIER-STOKES FLOW IN AN ELASTIC THIN POROUS MEDIUM
Authors: ENE IOANA-ANDREEA , PAULIN JEANNINE SAINT JEAN
Published: September 2004

In the general framework of the homogenization method we study the behavior of a thin elastic periodic structure immersed in a viscous fluid. After the proof of the convergence of the homogenization process by using the two-scale convergence method it is possible to take the limit as δ→0, the small parameter which represents the thickness of the solid part. We obtain a viscoelastic medium with fading memory. We consider two cases: the one in which we have a Stokes flow in the fluid part and the other one when we have a Navier-Stokes flow in the fluid part.
NUMERICAL METHODS FOR MINIMIZERS AND MICROSTRUCTURES IN NONLINEAR ELASTICITY
Authors: LI ZHIPING
Published: September 2004

A standard finite element method and a finite element truncation method are applied to solve the boundary value problems of nonlinear elasticity with certain nonconvex stored energy functions such as those of St. Venant-Kirchhoff materials. Finite element solutions are proved to exist and of the form of minimizers in appropriate sets of admissible finite element functions for both methods. Convergence of the finite element solutions to a solution in the form of a minimizer or microstructure for the boundary value problem is established. It is also shown that in the presence of Lavrentiev phenomenon the finite element truncation method can overcome the difficulty and converges to the absolute minimum while the standard finite element method converges to a pseudominimum which is a minimum in a slightly smaller set of admissible functions.
CYLINDRICAL TM-MODES IN A HOMOGENEOUS SELF-FOCUSING DIELECTRIC
Authors: STUART C.A.
Published: September 2004

This paper deals with the mathematical analysis of self-trapped light beams in a homogeneous medium which has a self-focusing dielectric response. We consider modes where the electromagnetic fields have a cylindrical symmetry and the magnetic field is transverse to the direction of propagation. The main results establish a range of wavelengths for which such guided modes exist. The behavior of the power of the beam as the wavelength approaches its extreme values is also determined. The existence of self-trapped modes is established using a variational principle. Bounds on the wavelength and the power are obtained directly from the associated quasilinear eigenvalue problem.
INTERNAL CONSTRAINTS AND BIFURCATIONS IN PSEUDO-RIGID BODIES
Authors: FORTE S. , VIANELLO M.
Published: September 2004

The equilibrium problem for pseudo-rigid bodies with internal constraints and subject to small loads is discussed. No limitations are placed on the constraints, except for the definitional axiomatic assumptions. Equilibrium configurations are obtained as critical points for a potential defined on the constraint manifold, a Liapunov-Schmidt reduction is performed and a second-order expansion of the reduced potential is obtained. This result is similar to an expansion due to Pierce for unconstrained bodies, but here different mathematical techniques are required. Through a framework which is preserved from the unconstrained theory it is shown that for loads of type 0 the number and stability of solutions is not altered by the introduction of internal constraints. By contrast, differences arise when the body is subjected to loads of type 1.
FRACTIONAL STEP METHODS FOR SPECTRAL APPROXIMATION OF ADVECTION-DIFFUSION EQUATIONS
Authors: GERVASIO PAOLA
Published: September 2004

Several classical fractional step schemes are proposed for the spectral approximation of advection-diffusion equation in two-dimensional geometries. Suitable boundary conditions are studied in order to preserve the accuracy of the schemes at each step. An example is given for the application of the fractional step schemes to solve problems with large Péclet number.
AN EFFECTIVE ALGORITHM FOR INCOMPATIBILITY ABDUCTION PROBLEMS
Authors: AYEB B. EL. , WANG S.
Published: September 2004

In the last decade, abduction has been a very active research area. This results in a variety of models mechanizing abduction, namely within a probablistic or logical framework. Recently, a few abductive models have been proposed within a neural framework. Unfortunately, these neural-/probablistic-/logical-based models focus on the most simple class, called independent abduction problems. In this paper, we propose a neural-based model to deal with incompatibility abduction problems. To our knowledge, our model is the first one able to efficiently generate best explanations to the complex class of incompatibility abduction problems.
HIGH SPEED FUZZY LEARNING MACHINE WITH GUARANTEE OF GLOBAL MINIMUM AND ITS APPLICATION TO CHAOTIC SYSTEM IDENTIFICATION AND MEDICAL IMAGE PROCESSING
Authors: UCHINO EIJI , YAMAKAWA TAKESHI
Published: September 2004

This paper describes a generalized fuzzy learning machine, which is a generalized and modified type of the neo-fuzzy-neuron presented by the authors in 1992. This machine can well grasp the nonlinear correlation of each input. It has a very high nonlinear mapping ability compared with the conventional neural networks, and it guarantees the global minimum. Furthermore, the learning speed and its accuracy are improved drastically. It was successfully applied to the identification of the nonlinear dynamical system, e.g. two dimensional Lorenz chaotic model, and to the automatic detection of the landmark locations in the roentgenographic cephalogram for an orthodontic treatment. The results were promising.
AN EFFICIENT HARDWARE ARCHITECTURE TO SUPPORT COMPLEX FUZZY REASONING
Authors: ASCIA G. , CATANIA V.
Published: September 2004

The paper presents the design of a VLSI fuzzy processor which is capable of supporting complex fuzzy reasoning. The architecture of the processor is based on a appropriate computational model, whose main features are: capability to cope with rule chaining; pre-processing of inferences to reduce the number of rules to be processed; parallel computation of the degree of activation of the rules; optimized representation of membership function. The processor performance is in the order of 1.5 MFLIPS (256 rule, 8 Fuzzy inputs, 4 output).
STATISTICAL GENERALIZATION OF PERFORMANCE-RELATED HEURISTICS FOR KNOWLEDGE-LEAN APPLICATIONS
Authors: IEUMWANANONTHACHAI ARTHUR , WAH BENJAMIN W.
Published: September 2004

In this paper, we present new results on the automated generalization of performance-related heuristics learned for knowledge-lean applications. By first applying genetics-based learning to learn new heuristics for some small subsets of test cases in a problem space, we study methods to generalize these heuristics to unlearned subdomains of test cases. Our method uses a new statistical metric called probability of win. By assessing the performance of heuristics in a range-independent and distribution-independent manner, we can compare heuristics across problem subdomains in a consistent manner. To illustrate our approach, we show experimental results on generalizing heuristics learned for sequential circuit testing, VLSI cell placement and routing, branch-and-bound search, and blind equalization. We show that generalization can lead to new and robust heuristics that perform better than the original heuristics across test cases of different characteristics.
NOISE HANDLING WITH EXTENSION MATRICES
Authors: WU XINDONG , KRISÁR JOHAN , MÅHLÉN PETTER
Published: September 2004

HCV is a heuristic attribute-based induction algorithm based on the newly-developed extension matrix approach. By dividing the positive examples (PE) of a specific class in a given example set into intersecting groups and adopting a set of strategies to find a heuristic conjunctive formula in each group which covers all the group’s positive examples and none of the negative examples (NE), it can find a covering formula in the form of variable-valued logic for PE against NE in low-order polynomial time. The original algorithm performs quite well with those data sets where noise and continuous data are not of major concern. However, its performance decreases when the data sets are noisy and contain continuous attributes. This paper presents noise handling techniques developed and implemented in HCV (Version 2.0), a noise tolerant version of the HCV algorithm, and provides a performance comparison of HCV with other inductive algorithms C4.5 and NewID in noisy and continuous domains.
GRG: KNOWLEDGE DISCOVERY USING INFORMATION GENERALIZATION, INFORMATION REDUCTION, AND RULE GENERATION
Authors: SHAN NING , HAMILTON HOWARD J. , CERCONE NICK
Published: September 2004

We present the three-step GRG approach for learning decision rules from large relational databases. In the first step, an attribute-oriented concept tree ascen sion technique is applied to generalize an information system. This step loses some information but substantially improves the efficiency of the following steps. In the second step, a reduction technique is applied to generate a minimalized information system called a reduct which contains a minimal subset of the generalized attributes and the smallest number of distinct tuples for those attributes. Finally, a set of maximally general rules are derived directly from the reduct. These rules can be used to interpret and understand the active mechanisms underlying the database.
TWO-WAY INDUCTION
Authors: DOMINGOS PEDRO
Published: September 2004

General-to-specific learners like ID3 and CN2 perform well when the target concept descriptions are general, but often have difficulties when they are specific or mixed. This problem can be alleviated by combining them with a specific-to-general learning component, resulting in a two-way induction system. In this paper one design for such a component is proposed, as well as two methods for combining the two components. Experiments on artificial domains show the combined learner to match or outperform “pure” versions of C4.5 and CN2 across the entire generality spectrum, with the advantage increasing for greater concept specificity. Experiments on 24 real-world domains from the UCI repository confirm the utility of two-way induction: the combined learner achieves higher accuracy than C4.5 in 17 domains (at the 5% significance level in 12), and similar results are obtained with CN2. Closer observation of the system’s behavior leads to a better understanding of its ability to correct overly-general rules with specific ones, and shows that there is still room for improvement.
PATH CONSISTENCY REVISITED
Authors: SINGH MONINDER
Published: September 2004

One of the main factors limiting the use of path consistency algorithms in real life applications is their high space complexity. Han and Lee proposed a path consistency algorithm, PC-4, with O(n3a3) space complexity, which makes it practicable only for small problems. I present a new path consistency algorithm, PC-5, which has an O(n3a2) space complexity while retaining the worst-case time complexity of PC-4. Moreover, the new algorithm exhibits a much better average-case time complexity. The new algorithm is based on the idea (due to Bessiere) that, at any time, only a minimal amount of support has to be found and recorded for a labeling to establish its viability; one has to look for a new support only if the current support is eliminated. I also show that PC-5 can be improved further to yield an algorithm, PC5++, with even better average-case performance and the same space complexity.
MONITORING PROGRESS WITH DYNAMIC PROGRAMMING ENVELOPES
Authors: AMANT ROBERT ST. , COHEN PAUL R. , KUWATA YOSHITAKA
Published: September 2004

Envelopes are a form of decision rule for monitoring plan execution. We describe one type, the DP envelope, that draws its decisions from a look-up table computed off-line by dynamic programming. Based on an abstract model of agent progress, DP envelopes let a developer approach execution monitoring as a problem independent of issues in agent design. We discuss the application of DP envelopes to a small transportation planning simulation, and discuss the issues that arise in an empirical analysis of the results.
METRICS-GUIDED REUSE
Authors: PAUL RAYMOND A.
Published: September 2004

This paper presents a discussion of significant issues in selection of a standardized set of the “best” software metrics to support a software reuse program. This discussion illustrates the difficulty in selection of a standardized set of reuse metrics because the “best” reuse metrics are determined by unique characteristics of each reuse application. An example of the selection of a single set of reuse metrics for a specific management situation is also presented.
A METHOD FOR REQUIREMENTS ANALYSIS AND KNOWLEDGE ELICITATION
Authors: LIU ALAN , TSAI JEFFREY J.P.
Published: September 2004

Requirements analysis is a knowledge intensive task and it requires an expert to understand what the clients need. In this paper, we introduce a method which contains different artificial intelligence techniques to perform this task, and a prototype knowledge-based requirements analysis system, RAKES, is presented to explain our approach. In this approach, not only the ordinary functional requirements are collected, but also some non-traditional information, such as non-functional requirements like the quality of operations or the background information for constructing the requirements, is gathered through a knowledge-based support. Different kinds of information collected are stored and organized in a knowledge base and can be used as the source of the user input in the latter phases of software development. Algorithms and procedures have been developed for constructing the interface language, organizing the knowledge base, and applying the knowledge base to different tasks. RAKES is integrated to an on-going research, called the FRORL methodology, to offer a systematic way toward requirements analysis, specification production, prototype generation, specification debugging, and code transformation.
A FORMAL APPROACH TO THE ANALYSIS OF PRIORITIES OF IMPRECISE CONFLICTING REQUIREMENTS
Authors: YEN JOHN , LIU XIAOQING FRANK
Published: September 2004

Priority analysis is one of the most important issues in the trade-off analysis of imprecise conflicting requirements whose elasticity is captured using fuzzy logic. Requirement analysts need to know not only the relative ordering of requirements based on their importance but also how much a requirement is more important than another requirement in order to achieve an effective trade-off. This paper presents a formal approach for reasoning about the relative priority by analyzing the customer’s trade-off preference among imprecise conflicting requirements. A possibilistic reasoning framework for inferring the lower bound of relative priority from case analysis under uncertainty is also developed. Consistency and nonredundancy criteria are established to facilitate the conversion of a possibilistic statement on a lower bound of relative priority into a relative priority. Finally, relative priorities are transformed into weights of importance so that they can be used in the aggregation of conflicting requirements to resolve conflicts.
TACTICAL ROUTE PLANNING: NEW ALGORITHMS FOR DECOMPOSING THE MAP
Authors: BENTON J.R. , IYENGAR S.S. , DENG W. , BRENER N. , SUBRAHMANIAN V.S.
Published: September 2004

This paper defines a new approach and investigates a fundamental problem in route planners. This capability is important for robotic vehicles(Martian Rovers, etc.) and for planning off-road military maneuvers. The emphasis throughout this paper will be on the design and analysis and hieiaichical implementation of our route planner. This work was motivated by anticipation of the need to search a grid of a trillion points for optimum routes. This cannot be done simply by scaling upward from the algorithms used to search a grid of 10,000 points. Algorithms sufficient for the small grid are totally inadequate for the large grid. Soon, the challenge will be to compute off-road routes more than 100 km long and with a one or two-meter grid. Previous efforts are reviewed and the data structures, decomposition methods and search algorithms are analyzed and limitations are discussed. A detailed discussion of a hieraichical implementation is provided and the experimental results are analyzed.
CHIRICO - A FRAMEWORK FOR COMPUTERIZATION OF MEDICAL PRACTICE GUIDELINES
Authors: DAVIS CLIFTON , EICK CHRISTOPH , KRISHNAMURTHY BALASUBRAMANIAN , SHAH ASHISH , WANKE LEE
Published: September 2004

Methodologies based on an elaboration of the Knowledge Acquisition and Design Structuring (KADS) philosophy were developed and a suite of tools based on this methodology was implemented. The tools implement object oriented support at the domain-layer, Bayesian reasoning combined with a Bayesian compatible version of “fuzzy sets“ to support the inference-layer, and mechanisms for knowledge level task control to support both the task-level and strategic-level. These tools were built for the task of computerizing medical practice guidelines. The tools were successfully applied to two practice guidelines, one selected by symptom (Febrile Neutropenia) and the other by drug class (CSF).
CDM: AN APPROACH TO LEARNING IN TEXT CATEGORIZATION
Authors: GOLDBERG JEFFREY L.
Published: September 2004

The Category Discrimination Method (CDM) is a new machine learning algo rithm designed specifically for text categorization. The motivation is there are sta tistical problems associated with natural language text when it is applied as input to existing machine learning algorithms (too much noise, too many features, skewed distribution).

The bases of the CDM are research results about the way that humans learn categories and concepts vis-à-vis contrasting concepts. The essential formula is cue validity borrowed from cognitive psychology, and used to select from all possible single word-based features the best predictors of a, given category.

The, hypothesis that CDM’s performance. will exceed two non-domain specific al gorithms, Bayesian classification and decision tree learners, is empirically tested.
ELICITATION OF NETWORK SERVICE SPECIFICATIONS FROM NATURAL LANGUAGE DESCRIPTIONS AT VARIOUS VIEWPOINTS
Authors: KOBAYASHI YOSHIZUMI , ENOKI HIROSHI , ZHANG QIANREN , OHTA TADASHI , TERASHIMA NOBUYOSHI
Published: September 2004

In order to respond to the increasingly diverse requirements for network services, it would be best if the specifications could be defined by the users who actually have those requirements. If the users themselves are to define the specifications, the best case would be to have them use the natural languages that they are familiar and comfortable with. Since network services become visible to the users via their terminals, when users write specifications for network services, the specifications may be defined in a form including specifications for the terminals in addition to network services. In this paper, we propose a method of extracting network service specifications from natural-language descriptions made from various points of view. First we will organize the concepts of network services on the basis of a model for network services. Next we will extract a number of viewpoints from the relationships between the network service providers and the receivers, i.e. the terminals and users, and clarify the relationships between those viewpoints and the network-service concepts. On the basis of this, we will propose a method for describing network service specifications in a natural language and for understanding them.