bluuebunny/crossref_metadata_2025 huggingface dataset:
IDENTIFICATION OF KINETIC PARAMETERS IN MULTIDIMENSIONAL CRYSTALLIZATION PROCESSES
Authors: GUNAWAN RUDIYANTO , MA DAVID L. , FUJIWARA MITSUKO , BRAATZ RICHARD D.
Published: July 2002

Advances in sensor technology and increased competition in the pharmaceutical industry have generated significant interest in the identification of models for the solution formation of crystals with multiple characteristic dimensions. A procedure is proposed that uses a small number of batch experiments to identify the kinetic parameters for multidimensional crystallization processes. The parameters are estimated simultaneously from the on-line measurement of infrared spectra and from cross-moments of the crystal size distribution. The identification procedure maximizes the informativeness of the data produced by each experiment, produces an estimate of the accuracy of the kinetic parameters, and allows the consideration of competing hypotheses for characterizing the crystallization kinetics. The parameter identification strategy is applied to the batch crystallization of potassium dihydrogen phosphate, which forms two-dimensional crystal from solution. To the best of the author's knowledge, this is the first time that the kinetic parameters for a multidimensional crystallization process are identified from a small number of batch experiments.
EFFECT OF SURFACE PROPERTIES ON THE WETTABILITY OF IRON CONTAINING AMORPHOUS CARBON FILMS
Authors: CHEN J. S. , LAU S. P. , SUN Z. , CHEN G. Y. , LI Y. J. , TAY B. K. , CHAI J. W.
Published: July 2002

Ta-C and iron containing amorphous carbon (a-C:Fe) films were deposited by filtered cathodic vacuum arc technique. The influences of Fe contents on the wettability of the films were investigated in terms of surface energy. The surface energy of a-C:Fe films was determined by the contact angle measurement. Atomic force microscopy (AFM), Raman spectroscopy and X-ray induced photoelectron spectroscopy (XPS) were employed to analyze the origin of the variation of surface energy with various Fe content. It is found that the contact angle for water increases significantly after incorporating Fe into the films and the films become hydrophobic. The roughness of these films has a little effect on the contact angle. The surface energy is reduced after incorporating Fe into the a-C film which is due to the reduction of both dispersive and polar component. The reduction in dispersive component is ascribed to the decrease of atomic density of the a-C:Fe films due to the increase in sp2 bonded carbon. The absorption of oxygen on the surface play an important role in the reduction of polar component for the a-C:Fe films. It is proposed that such network as (Ca-O-Fe)-O-(Fe-O-Ca) may be formed and responsible for the reduction of polar component.
AMORPHOUS CARBON NITRIDE THIN FILM AS A BARRIER AGAINST COPPER DIFFUSION
Authors: NING JIANG , XU S. , CHAI J. W. , CHEN L. K. , SEE ALEX , AHN J.
Published: July 2002

The application of carbon nitride as a barrier against copper diffusion was investigated. Amorphous carbon nitride (a-CN) thin films were prepared on Si(100) substrates by rf magnetron sputtering of graphite target in N2 plasma. A thin Cu layer was then deposited in-situ atop of the a-CN film. Annealing process was carried out in nitrogen (N2) ambient at the temperature of 400°C and 600°C respectively. The as-deposited and annealed films were characterized by x-ray photoelectron spectroscopy (XPS). The measurements show that both sp2C-N and sp3-N bonds were formed in the as-deposited carbon nitride films. The compositional analyses indicate that the deposited a-CN thin film is able to act as an effective diffusion barrier against copper at annealing temperature up to 400°C.
CHARGE AND ORBITAL ORDER IN THE ELECTRON DOPED MAGNANITE (Bi,Ca)MnO3
Authors: HATTON P. D. , WILKINS S. B. , SPENCER P. D. , MANNIX D. , BROWN S. D. , D'ALMEIDAHATTON T. , CHEONG S.-W.
Published: July 2002

The interplay between charge, spin and orbital degrees of freedom in transition metal oxides has been a matter of much interest in recent years. In this paper we present X-ray scattering results of charge and orbital ordering in the electron doped manganite Bi 0.24 Ca 0.76 MnO 3. Using High Energy X-ray Scattering (HEXS) the charge ordering, structural modulation due to the Jahn–Teller ordering and the harmonic of the structural modulation have been measured. The superlattice reflections due to the Jahn–Teller ordering are found to maximise in intensity at the Neél point. We have confirmed using resonant X-ray scattering at the K-edge of manganese and the Anisotropic Tensor of Susceptibility technique (ATS) that superlattice reflections occurring at a modulation wavevector of (0.5, 0, 0) are due to charge ordering in a Mn 3+/ Mn 4+ ordering pattern. In addition superlattice reflections corresponding to the orbital order were measured at a modulation wavevector of (0.25, 0, 0). The temperature dependence of both the Jahn–Teller structural distortion peak (1.75, 2, 0) and the charge ordering peak (3 0 0) were observed to behave identically, gradually increasing with decreasing temperature.
A NOVEL BUFFER LAYER FOR GROWING ULTRATHIN FILMS OF YBa2Cu3Oy ON YSZ SUBSTRATES
Authors: Gao J. , Tang W. H. , Chui T. C.
Published: July 2002

A new buffer material Nd 2 CuO 4 has been used to improve the initial epitaxy of YBa 2 Cu 3 O y, on yttrium stabilized ZrO 2. By using Nd 2 CuO 4 as a buffer layer, the epitaxy and crystallinity of the grown YBa 2 Cu 3 O y, have been significantly enhanced. High quality superconducting thin and ultrathin films with a thickness down to two unit cells have been obtained.
LUMINESCENCE STUDIES IN THERMAL OXIDE FILMS WITH Si IMPLANTATION
Authors: GRACIA F. FLORES , CARRILLO J. , ACEVES M. , CALLEJA W. , DOMÍNGUEZ C. , FALCONY C.
Published: July 2002

The objective of this work is to investigate the origin of the emission bands of Photo and Cathodo - luminescence (PL, CL) in thermal silicon dioxide films implanted with Silicon. The films were obtained by 150 KeV Si implantation into thennal oxide, with doses of 1×1016 cm-2 and 1×1017 cm-2. Thermal treatments of 0, 30, 60 and 180 minutes in nitrogen at 1100°C were applied. We found light emission in the visible range, the bands change with the ion implantation conditions and thermal treatments. The as implanted samples present photoluminescence bands around 1.95 eV and 2.4 eV for both doses, and they disappear width thermal treatments. After annealing, the low dose samples has a photoluminescence band at 2.6 eV, while those of dose of 1×1017 cm-2 has a band centered at 1.7 eV. The intensity of the bands changes with thermal treatment. The cathodoluminescence bands are at 2.7 eV for both implantation doses in samples with and without theermal treatments. A discussion of the results and conclusions that contribute to better understand this nowadays controversial subject is presented.
CHARACTERIZATION OF DOPED SILLENITES BY ELECTROOPTIC AND SPECTRAL METHODS
Authors: ILINSKII A. , PRUTSKIJ T. , SILVA-ANDRADE F. , CHÁVEZ F. , SHADRIN E. , KHRUSTALKOVA L.
Published: July 2002

The main result of this paper was the high accurate characterization of the investigated samples. We were able to measure the Maxwell relaxation time for doped (Al, Cr, Mn, Ti, Nd) and undoped sillenite crystals was determined. The obtained values are as large as 103s. Also, the correlation between spectroscopic, electrical and electrooptical properties of doped sillenite crystals was established.
MAGNETIC FIELD INDUCED GAP AND KINK BEHAVIOR OF THERMAL CONDUCTIVITY
Authors: FERRER E. J. , GUSYNIN V. P. , DE LA INCERA V.
Published: July 2002

The thermal conductivity of a quasiparticle (QP) system described by a relativistic four-fermion interaction model in the presence of an external magnetic field is calculated. It is shown that, for narrow widths of quasiparticles, the thermal conductivity, as a function of the applied magnetic field, exhibits a kink behavior at a critical field B c ~ T2. The kink is due to the opening of a gap in the QP spectrum at a critical magnetic field B c and to the enhancement of the transitions between the zeroth and first Landau levels. Possible applications of the results are discussed.
INCORPORATING PRIMARY SOURCE MATERIAL INTO THE UNDERGRADUATE COMPUTER VISION CURRICULUM
Authors: NOVINS KEVIN , MCCANE BRENDAN
Published: July 2002

Computer vision is a very broad and rapidly changing field. A major challenge for teachers of this subject is to cover a large body of basic theory while at the same time giving a good sense of state-of-the-art research. Traditionally our fourth year undergraduate course in computer vision was taught using lectures and textbooks. We report on the results of two different alterations of the course, both of which focus on our students' own research into recent primary source literature. In the first alteration we used a seminar-based format. It was a qualified success. The students found the course interesting, gained a high-level understanding of the state-of-the-art in computer vision, and developed critical analysis skills. However, despite the fact that they worked hard, student learning of details of the techniques suffered. They were able to complete the course without a good understanding of the theoretical and mathematical foundations of computer vision. In response to this, our second alteration was to base the course around six problem-based learning units. The students benefitted from the reduced set of topics and higher level of practical work.
IMPROVING STABILITY OF DECISION TREES
Authors: LAST MARK , MAIMON ODED , MINKOV EINAT
Published: July 2002

Decision-tree algorithms are known to be unstable: small variations in the training set can result in different trees and different predictions for the same validation examples. Both accuracy and stability can be improved by learning multiple models from bootstrap samples of training data, but the "meta-learner" approach makes the extracted knowledge hardly interpretable. In the following paper, we present the Info-Fuzzy Network (IFN), a novel information-theoretic method for building stable and comprehensible decision-tree models. The stability of the IFN algorithm is ensured by restricting the tree structure to using the same feature for all nodes of the same tree level and by the built-in statistical significance tests. The IFN method is shown empirically to produce more compact and stable models than the "meta-learner" techniques, while preserving a reasonable level of predictive accuracy.
CHAOS SYNCHRONIZATION VIA CONTROLLING PARTIAL STATE OF CHAOTIC SYSTEMS
Authors: YU XINGHUO , SONG YANXING
Published: July 2002

An invariant manifold based chaos synchronization approach is proposed in this letter. A novel idea of using only a partial state of chaotic systems to synchronize the coupled chaotic systems is presented by taking into account the inherent dynamic properties of the chaotic systems. The effectiveness of the approach and idea is tested on the Lorenz system and the fourth-order Rossler system.
DISPERSIVE KINETICS: A HOST OF CHALLENGES FOR CHAOTIC DYNAMICS
Authors: PLONKA ANDRZEJ
Published: July 2002

The specific reaction rate [Formula: see text], [Formula: see text], is used in numerous areas of condensed phase chemistry to account for the dispersion of reactant reactivity seen at time scales shorter than or comparable to the time scale of structural relaxations of systems. So far, the use of k(t), which introduces the fractal-time into the chemical kinetics, was rationalized by random-walk modeling, incorporating the long-tailed (Lévy) distribution Ψ(t)~t-â-1 of times between the events that limit the motion of reactants. Now, new perspectives for developments in kinetics are seen as the once abstract notion of fractal space and time now appear naturally and are inevitable in chaotic dynamical systems.
ON DIFFUSION DRIVEN OSCILLATIONS IN COUPLED DYNAMICAL SYSTEMS
Authors: POGROMSKY ALEXANDER , GLAD TORKEL , NIJMEIJER HENK
Published: July 2002

The paper deals with the problem of destabilization of diffusively coupled identical systems. Following a question of Smale [1976], it is shown that globally asymptotically stable systems being diffusively coupled, may exhibit oscillatory behavior. It is shown that if the diffusive medium consists of hyperbolically nonminimum phase systems and the diffusive factors exceed some threshold value, the origin of the overall system undergoes a Poincaré–Andronov–Hopf bifurcation resulting in oscillatory behavior.
CHAOTIC COMMUNICATION USING TIME-DELAYED OPTICAL SYSTEMS
Authors: VANWIGGEREN GREGORY D. , ROY RAJARSHI
Published: July 2002

We discuss experimental demonstrations of chaotic communication in several optical systems. In each, an erbium-doped fiber ring laser (EDFRL) produces chaotic fluctuations of light intensity onto which is modulated a message consisting of a sequence of pseudorandom digital bits. This combination of chaos and message propagates at a wavelength of ~ 1.5 microns through standard single-mode optical fiber from the transmitter to a receiver, where the message is recovered from the chaos. We present evidence of the high-dimensional nature of the chaotic waveforms and demonstrate chaotic communications through 35 km of single-mode optical fiber at up to 250 Mbit/s, a rate that is, at present, limited only by the speed of our detector electronics.
DYNAMICS OF ELASTIC EXCITABLE MEDIA
Authors: CARTWRIGHT JULYAN H. E. , EGUÍLUZ VÍCTOR M. , HERNÁNDEZ-GARCÍA EMILIO , PIRO ORESTE
Published: July 2002

The Burridge–Knopoff model of earthquake faults with viscous friction is equivalent to a van der Pol–FitzHugh–Nagumo model for excitable media with elastic coupling. The lubricated creep–slip friction law we use in Burridge–Knopoff model describes the frictional sliding dynamics of a range of real materials. Low-dimensional structures including synchronous oscillations and propagating fronts are dominant, in agreement with the results of laboratory friction experiments. Here we explore the dynamics of fronts in elastic excitable media.
THE CHINESE MONOID
Authors: CASSAIGNE JULIEN , ESPIE MARC , KROB DANIEL , NOVELLI JEAN-CHRISTOPHE , HIVERT FLORENT
Published: July 2002

Résumé: Cet article présente une étude combinatoire du monoïde Chinois, un monoïde ternaire proche du monoïde plaxique, fondé sur le schéma cba≡bca≡cab. Un algorithme proche de l'algorithme de Schensted nous permet de caractériser les classes d'équivalence et d'exhiber une section du monoïde. Nous énonçons également une correspondance de Robinson–Schensted pour le monoïde Chinois avant de nous intéresser au calcul du cardinal de certaines classes. Ce travail a permis de développer de nouveaux outils combinatoires. Entre autres, nous avons trouvé un plongement de chacune des classes d'équivalence dans la plus grande classe. Quant à la dernière partie de cet article, elle présente l'étude des relations de conjugaison.

This paper presents a combinatorial study of the Chinese monoid, a ternary monoid related to the plactic monoid and based on the relation scheme cba≡bca≡cab. An algorithm similar to Schensted's algorithm yields a characterization of the equivalence classes and a cross-section theorem. We also establish a Robinson–Schensted correspondence for the Chinese monoid before computing the order of specific Chinese classes. For this work, we had to develop some new combinatorial tools. Among other things we discovered an embedding of every equivalence class in the largest one. Finally, the end of this paper is devoted to the study of conjugacy classes.
SOLUTION TO A PROBLEM OF KUBLANOVSKY AND SAPIR
Authors: DELIĆ DEJAN
Published: July 2002

We construct a finitely based congruence-distributive variety of algebras in a finite language whose set of subalgebras of finite simple algebras is non-recursive.
TIME-DEPENDENT RESCALINGS AND LYAPUNOV FUNCTIONALS FOR THE VLASOV–POISSON AND EULER–POISSON SYSTEMS, AND FOR RELATED MODELS OF KINETIC EQUATIONS, FLUID DYNAMICS AND QUANTUM PHYSICS
Authors: DOLBEAULT J. , REIN G.
Published: July 2002

We investigate rescaling transformations for the Vlasov–Poisson and Euler–Poisson systems and derive in the plasma physics case Lyapunov functionals which can be used to analyze dispersion effects. The method is also used for studying the long time behavior of the solutions and can be applied to other models in kinetic theory (two-dimensional symmetric Vlasov–Poisson system with an external magnetic field), in fluid dynamics (Euler system for gases) and in quantum physics (Schrödinger–Poisson system, nonlinear Schrödinger equation).
A MIXED NONCONFORMING FINITE ELEMENT FOR THE ELASTICITY AND STOKES PROBLEMS
Authors: FARHLOUL M. , FORTIN M.
Published: July 2002

A mixed-hybrid formulation of the elasticity problem with a nonconforming symmetric approximation of the stress–tensor is considered. Based on such a formulation, a new finite element of low order with minimal number of degrees of freedom is constructed. Optimal error estimates are derived. Moreover all estimates are valid uniformly with respect to compressibility and apply for the Stokes problem. Finally, an equivalence between this finite element and the piecewise quadratic nonconforming approximation of the elasticity problem is established.
The fourth Skein Module and the Montesinos-Nakanishi Conjecture for 3-algebraic links
Authors: Przytycki Józef H. , Tsukamoto Tatsuya
Published: July 2002

We study the fourth skein module of 3-manifolds, based on the skein relation b0L0 + b1L1 + b2L2 + b3L3 = 0 and a framing relation L(1) = aL (a, b0, b3 invertible). We give necessary conditions for trivial links to be linearly independent in the module. We show how elements of the skein module behave under the n-move and we compute the values for (2, n)-torus links and twist knots as elements of the skein module. Using mutants and rotors, we find different links which represent the same element in the skein module. We also show that algebraic links (in the sense of Conway) and closed 3-braids are linear combinations of trivial links. We introduce the concept of n-algebraic tangles (and links) and analyze the skein module for 3-algebraic links. As a by product we prove the Montesinos-Nakanishi 3-moves conjecture for 3-algebraic links (including 3-bridge links). For links in S3, the structure of our skein module suggests the existence of three new polynomial invariants of unoriented framed (or unframed) links. One of them would generalize the Kauffman polynomial of links and another one could be used to analyze amphicheirality of links (and may work better than the Kauffman polynomial). In the conclusion, we speculate that our new knot invariants are related to a deformation of the symplectic quotient of braid groups.
ON THE ELECTRON EXPULSION IN HEAVY ION NATURAL RADIOACTIVITY AND NUCLEAR FRAGMENTATION
Authors: STRATAN G. , SCHEID W.
Published: July 2002

An estimation of the relative probability of electron expulsion from inner shells of atoms following heavy cluster decay or nuclear spontaneous fission is performed. The calculation takes into account the recoil of the daughter nucleus, both in the case of dipole and quadrupole terms. The results show an enhancement of the electron emission probability in comparison with the case of α-decay.
OPTIMAL MODEL FOR THE DIFFRACTION EFFECT IN THE ULTRASONIC FIELD OF PISTON TRANSDUCERS
Authors: TEMSAMANI ABDELLATIF BEY , VANDENPLAS STEVE , VAN BIESEN LEO
Published: July 2002

In this work, the analytical and experimental examination of the problem of diffraction effect is treated. In the laboratory, the diffraction phenomena have been mainly due to the beam spread of the ultrasonic plane wave propagating through a viscoelastic material. In fact, this effect has been found to be related, essentially to the attenuation and dispersion losses on a viscoelastic material. In this work, a frequency domain system identification approach is applied to determine an optimal function correcting the beam spread effect in both the normal and oblique incidences for a large frequency band (300 kHz–3 MHz). The Maximum Likelihood Estimator is applied to the magnitude and phase of the measured beam patterns of the used transducers in order to determine the model parameters. The calibration procedure is also discussed. Once the proposed model is established, the propagation through a viscoelastic plate is described and a comparison with measurements is done to validate the investigated model. The obtained longitudinal and shear attenuation and dispersion of the ultrasound in the viscoelastic plate are compared with those obtained by applying the complex harmonic plane waves combination model.
A SIMILARITY-BASED GENERALIZATION OF FUZZY ORDERINGS PRESERVING THE CLASSICAL AXIOMS
Authors: BODENHOFER ULRICH
Published: July 2002

Equivalence relations and orderings are key concepts of mathematics. For both types of relations, formulations within the framework of fuzzy relations have been proposed already in the early days of fuzzy set theory. While similarity (indistinguishability) relations have turned out to be very useful tools, e.g. for the interpretation of fuzzy partitions and fuzzy controllers, the utilization of fuzzy orderings is still lagging far behind, although there are a lot of possible applications, for instance, in fuzzy preference modeling and fuzzy control. The present paper is devoted to this missing link. After a brief motivation, we will critically analyze the existing approach to fuzzy orderings. In the main part, an alternative approach to fuzzy orderings, which also takes the strong connection to gradual similarity into account, is proposed and studied in detail, including several constructions and representation results.
THE ENERGY AND ANGULAR DISTRIBUTIONS OF LOW-ENERGY He+ SCATTERED FROM Al(111)
Authors: BASTASZ R. , WHALEY J. A. , ELLIS W. P.
Published: July 2002

Measurements of 500 eV 4 He + scattered from Al(111) surfaces provide detailed information about the scattering process and surface crystallography. We report various observations concerning collision inelasticity, multiple scattering, and shadow-cone focusing effects. A large inelastic energy loss of the scattered He + is observed, which causes multiple-scattering events at oblique incidence angles to have energies below the elastic single-scattering energy. Inelastic He + scattering from clean, ordered Al(111) shows interesting intensity variations as a function of azimuthal orientation and incidence angle. At a critical incidence angle, where the top edge of a shadow cone intersects a nearest-neighbor Al surface atom, the scattered ion intensity exhibits 60° azimuthal periodicity. At a more glancing angle of incidence, a double-peaked structure appears. The scattered He + intensity varies as a function of incidence angle, as expected from classical shadow cone calculations.
MoS2 AND WS2 NANOTUBES ALLOYED WITH GOLD AND SILVER
Authors: REMSKAR M. , SKRABA Z. , SANJINÉS R. , LÉVY F.
Published: July 2002

We report on the existence of MoS 2 and WS 2 micro- and nanotubes alloyed with gold and silver. The tubes have been grown by chemical transport reaction with iodine as a transport agent. While the undoped inorganic tubes grow by spiral rolling of the molecular layers, the presence of noble metals can partially or completely remove the chirality. The molecular layers grow in the form of coaxial cylinders. The noble metal is situated inside the walls of the tubes. It influences the longitudinal terminations of the tubes and increases the wall thickness. Distortion of every second van der Waals gap reveals that staging is present. Stop of chirality in alloyed inorganic tubes appears to be strongly coupled with the expansion of VdW gaps.

The existence of M x MoS 2 and M x WS 2; (M: Au, Ag) ternary compounds, which are not known in the usual plane layered structures, gives evidence that the cylindrical geometry of crystals can stabilize new compounds and changes the chemistry as well as the physical properties of the materials.
EFFECT OF A NEW REPAIR TECHNIQUE ON BIOMECHANICAL PROPERTIES OF CANINE FLEXOR TENDONS — IN VITRO STUDY
Authors: Kubota Hideaki , Miyanishi Keita , Hoshino Shushi , Hatanaka Hitoshi , Iwamoto Yukihide
Published: July 2002

A new repair technique that was easy to perform yet offered adequate strength was developed. The purpose of this study was to evaluate the mechanical properties of flexor tendon repairs undertaken with this technique. Thirty-two canine cadaver flexor digitorum profundus tendons in Zone 2 were lacerated and repaired with the technique, which consisted of a four-strand core suture using the double-modified Kessler method in combination with a cross-stitch circumferential suture. A 5–0 coated braided polyester suture and a 5–0 ultra-high molecular weight polyethylene suture were used as the core suture, and a 6–0 polypropylene monofilament was used as the circumferential suture. Tendons repaired with the 5–0 braided polyester suture had gap strengths (2.07 ± 0.46 kgf) and breaking strengths (6.03 ± 0.55 kgf), which were sufficient to withstand an early active mobilization protocol. There were no significant differences regarding mechanical properties between the two suture materials. This combined suture technique has the potential to be utilized in in vivo cases.
VOLATILITY CLUSTERING IN FINANCIAL MARKETS: A MICROSIMULATION OF INTERACTING AGENTS
Authors: LUX THOMAS , MARCHESI MICHELE
Published: July 2002

The finding of clustered volatility and ARCH effects is ubiquitous in financial data. This paper presents a possible explanation for this phenomenon within a multi-agent framework of speculative activity. In the model, both chartist and fundamentalist strategies are considered with agents switching between both behavioural variants according to observed differences in pay-offs. Price changes are brought about by a market maker reacting to imbalances between demand and supply. Most of the time, a stable and efficient market results. However, its usual tranquil performance is interspersed by sudden transient phases of destabilisation. An outbreak of volatility occurs if the fraction of agents using chartist techniques surpasses a certain threshold value, but such phases are quickly brought to an end by stabilising tendencies. Formally, this pattern can be understood as an example of a new type of dynamic behaviour known as "on-off intermittency" in physics literature. Statistical analysis of simulated time series shows that the main stylised facts (unit roots in levels together with heteroscedasticity and leptokurtosis of returns) can be found in this "artificial" market.
CAN HERDING EXPLAIN CYCLIC CO-MOVEMENT?
Authors: SÜSSMUTH BERND
Published: July 2002

Recently, co-movement and the synchronised pattern of business cycles on various scales (sectoral, national, etc.) attract growing attention among macroeconomists. This paper integrates qualitative implications of a simple endogenously-timed herding model's logic into an investment cycle model. It is shown that this integrated argumentation is generally applicable for models that generate endogenous cyclic dynamics to explain the coupling of frequencies. Informational externalities induced by herding on the micro-level therefore seem to be an adequate argumentation behind business cycle models that capture co-movement by means of the so-called "mode-locking" mechanism.
AXISYMMETRIC VIBRATIONS OF CIRCULAR AND ANNULAR PLATES WITH VARIABLE THICKNESS
Authors: EISENBERGER M. , JABAREEN M.
Published: July 2002

In this work the exact axisymmetric vibration frequencies of circular and annular variable thickness plates are found. The solution is obtained using the exact element method developed earlier. It allows for the exact solution of problems with general polynomial variation in thickness using infinite power series. The solution is exact up to the accuracy of the computer. The natural frequencies of vibration are found as the solutions of the frequency equation. Normalized values for the natural frequencies are given for linear, parabolic and cubic variations of the plate thickness, for circular and annular plates, with four types of boundary conditions on the inner and outer boundaries.
APPLICATION OF CFD IN THE DESIGNING OF A MEMBRANE OXYGENATOR
Authors: WANG JONG H.
Published: July 2002

A CFD (Computational Fluid Dynamics) model was developed to simulate flow in a membrane oxygenator. The hollow fiber bundles were treated as a porous medium. This study demonstrated that the numerical model could accurately predict the distributions of flow velocity, pressure, shear stresses, temperature, and oxygen concentration in the device. The numerical model is a powerful tool for the designing of a membrane oxygenator.
THE STEADY STATE OF THE TAPPED ISING MODEL
Authors: DEAN DAVID S. , LEFEVRE ALEXANDRE
Published: July 2002

We consider a tapping dynamics, analogous to that in experiments on granular media, on the simple one-dimensional ferromagnetic Ising model. When unperturbed, the system undergoes a single spin flip falling dynamics where only energy lowering moves occur. With this dynamics the system has an exponentially large number of metastable states and gets stuck in blocked or jammed configurations as do granular media. When stuck, the system is tapped, in order to make it evolve, by flipping in parallel each spin with probability p (corresponding to the strength of the tapping). Under this dynamics the system reaches a steady state regime characterized by an asymptotic energy per spin E(p), which is determined analytically. Within the steady state regime we compare certain time averaged quantities with the ensemble average of Edwards based on a canonical measure over metastable states of fixed average energy. The ensemble average yields results in excellent agreement with the dynamical measurements.
Application of Biological Learning Theories to Mobile Robot Avoidance and Approach Behaviors
Authors: Chang Carolina , Gaudiano Paolo
Published: July 2002

We present a neural network that learns to control approach and avoidance behaviors in a mobile robot based on a form of animal learning known as operant conditioning. Learning, which requires no supervision, takes place as the robot moves around an environment cluttered with obstacles and light sources. The neural network requires no knowledge of the geometry of the robot or of the quality, number, or configuration of the robot's sensors. In this article we provide a detailed presentation of the model, and show our results with the Khepera and Pioneer 1 mobile robots.
PREDICTING UNKNOWN MOTION FOR MODEL INDEPENDENT VISUAL SERVOING
Authors: WIRA PATRICE , URBAN JEAN-PHILIPPE
Published: July 2002

Prediction in real-time image sequences is a key-feature for visual servoing applications. It is used to compensate for the time-delay introduced by the image feature extraction process in the visual feedback loop. In order to track targets in a three-dimensional space in real-time with a robot arm, the target's movement and the robot end-effector's next position are predicted from the previous movements. A modular prediction architecture is presented, which is based on the Kalman filtering principle. The Kalman filter is an optimal stochastic estimation technique which needs an accurate system model and which is particularly sensitive to noise. The performances of this filter diminish with nonlinear systems and with time-varying environments. Therefore, we propose an adaptive Kalman filter using the modular framework of mixture of experts regulated by a gating network. The proposed filter has an adaptive state model to represent the system around its current state as close as possible. Different realizations of these state model adaptive Kalman filters are organized according to the divide-and-conquer principle: they all participate to the global estimation and a neural network mediates their different outputs in an unsupervised manner and tunes their parameters. The performances of the proposed approach are evaluated in terms of precision, capability to estimate and compensate abrupt changes in targets trajectories, as well as to adapt to time-variant parameters. The experiments prove that, without the use of models (e.g. the camera model, kinematic robot model, and system parameters) and without any prior knowledge about the targets movements, the predictions allow to compensate for the time-delay and to reduce the tracking error.
An algorithm for finding canonical sets of ground rewrite rules in polynomial time
Authors: Gallier Jean , Narendran Paliath , Plaisted David , Raatz Stan , Snyder Wayne
Published: July 2002

In this paper, it is shown that there is an algorithm that, given by finite set
E
of ground equations, produces a reduced canonical rewriting system
R
equivalent to
E
in polynomial time. This algorithm based on congruence closure performs simplification steps guided by a total simplification ordering on ground terms, and it runs in time

O(n
3
)

.
Modeling pigmented materials for realistic image synthesis
Authors: Haase Chet S. , Meyer Gary W.
Published: July 2002

This article discusses and applies the Kubelka-Munk theory of pigment mixing to computer graphics in order to facilitate improved image synthesis. The theories of additive and subtractive color mixing are discussed and are shown to be insufficient for pigmented materials. The Kubelka–Munk theory of pigment mixing is developed and the relevant equations are derived. Pigment mixing experiments are performed and the results are displayed on color television monitors. A paint program that uses Kubelka–Munk theory to mix real pigments is presented. Theories of color matching with pigments are extended to determine reflectances for use in realistic image synthesis.
A dynamic processor allocation policy for multiprogrammed shared-memory multiprocessors
Authors: McCann Cathy , Vaswani Raj , Zahorjan John
Published: July 2002

We propose and evaluate empirically the performance of a dynamic processor-scheduling policy for multiprogrammed shared-memory multiprocessors. The policy is dynamic in that it reallocates processors from one parallel job to another based on the currently realized parallelism of those jobs. The policy is suitable for implementation in production systems in that:

We have evaluated our scheduler and compared it to alternatives using a set of prototype implementations running on a Sequent Symmetry multiprocessor. Using a number of parallel applications with distinct qualitative behaviors, we have both evaluated the policies according to the major criterion of overall performance and examined a number of more general policy issues, including the advantage of “space sharing” over “time sharing” the processors of a multiprocessor, and the importance of cooperation between the kernel and the application in reallocating processors between jobs. We have also compared the policies according to other criteia important in real implementations, in particular, fairness and respone time to short, sequential requests. We conclude that a combination of performance and implementation considerations makes a compelling case for our dynamic scheduling policy.
Simulating synchronized clocks and common knowledge in distributed systems
Authors: Neiger Gil , Toueg Sam
Published: July 2002

Time and knowledge are studied in synchronous and asynchronous distributed systems. A large class of problems that can be solved using logical clocks as if they were perfectly synchronized clocks is formally characterized. For the same class of problems, a broadcast primitive that can be used as if it achieves common knowledge is also proposed. Thus, logical clocks and the broadcast primitive simplify the task of designing and verifying distributed algorithms: The designer can assume that processors have access to perfectly synchronized clocks and the ability to achieve common knowledge.
A characterization of the simple failure-biasing method for simulations of highly reliable Markovian Systems
Authors: Nakayama Marvin K.
Published: July 2002

Simple failure biasing is an importance-sampling technique used to reduce the variance of estimates of performance measures and their gradients in simulations of highly reliable Markovian systems. Although simple failure biasing yields bounded relative error for the performance measure estimate when the system is balanced, it may not provide bounded relative error when the system is unbalanced.

In this article, we provide a characterization of when the simple failure-biasing method produces estimators of a performance measure and its derivatives with bounded relative error. We derive a necessary and sufficient condition on the structure of the system for when the performance measure can be estimated with bounded relative error when using simple failure biasing.

Furthermore, a similar condition for the derivative estimators is established. One interesting aspect of the conditions is that it shows that to obtain bounded relative error, not only the most likely paths to system failure must be examined but also some secondary paths leading to failure as well. We also show by example that the necessary and sufficient conditions for a derivative estimator do not imply those for the performance measure estimator; i.e., it is possible to estimate a derivative more efficiently than the performance measure when using simple failure biasing.
Circumscription with homomorphisms
Authors: Rathmann Peter K. , Winslett Marianne , Manasse Mark
Published: July 2002

One important facet of common-sense reasoning is the ability to draw default conclusions about the state of the world, so that one can, for example, assume that a given bird flies in the absence of information to the contrary. A deficiency in the circumscriptive approach to common-sense reasoning has been its difficulties in producing default that Tweety ≠ Blutto using ordinary circumscription, or conclude by default that a particular bird flies, if some birds are known not to fly. In this paper, we introduce a new form of circumscription, based on homomorphisms between models, that remedies these two problems and still retains the major desirable properties of traditional forms of circumscription.
Control-theoretic techniques for stepsize selection in implicit Runge-Kutta methods
Authors: Gustafsson Kjell
Published: July 2002

The problem of stepsize selection in implicit Runge-Kutta schemes is analyzed from a feedback control point of view. This approach leads to a better understanding of the relation between stepsize and error. A new dynamical model describing this relation is derived. The model is used as a basis for a new stepsize selection rule. This rule achieves better error control at little extra expense. The properties of the new model and the improved performance of the new error control are demonstrated using both analysis and numerical examples.
Real values of the
W
-function
Authors: Barry D. A. , Culligan-Hensley P. J. , Barry S. J.
Published: July 2002

Approximations for real values of
W(x)
, where W is defined by solutions of
W
exp(
W
) =
x
, are presented. All of the approximations have maximum absolute (|
W
|>1) or relative (|
W
|<1) errors of
O
(10
−4
). With these approximations an efficient algorithm, consisting of a single iteration of a rapidly converging iteration scheme, gives estimates of
W(x)
accurate to at least 16 significant digits (15 digits if double precision is used). The Fortran code resulting from the algorithm is written to account for the different floating-point-number mantissa lengths on different computers, so that
W(x)
is computed to the floating-point precision available on the host machine.
The ACM electronic publishing plan
Authors: Denning Peter J. , Rous Bernard
Published: July 2002

For the past three years, the ACM Publications Board has been developing its vision for the future of publication in the electronic age and a program to achieve it. I am pleased to present that plan here. We envisage a diminishing role for print journals and exciting new programs around an ACM digital library. The plan raises important policy questions regarding the treatment of copyright. Our interim answers to these policy questions are discussed in two additional documents—the ACM Interim Copyright Policies and the ACM Author's Guide to the Interim Copyright Policies. Our overall intention is to move aggressively into electronic publishing and to preserve the traditional openness of ACM publications in the new media. Authors and readers should find these policies at least as hospitable as the traditional ones.
Relief from the audio interface blues
Authors: Resnick Paul , Virzi Robert A.
Published: July 2002

Menus, lists, and forms are the workhorse dialogue structures in telephone-based interactive voice response applications. Despite diversity in applications, there is a surprising homogeneity in the menu, list, and form styles commonly employed. There are, however, many alternatives, and no single style fits every prospective application and user population. A design space for each dialogue structure organizes the alternatives and provides a framework for analyzing their benefits and drawbacks. In addition to phone-based interactions, the design spaces apply to any limited-bandwidth, temporally constrained display devices, including small-screen devices such as personal digital assistants (PDAs) and screen phones.
Logical foundations of object-oriented and frame-based languages
Authors: Kifer Michael , Lausen Georg , Wu James
Published: July 2002

We propose a novel formalism, calledFrame Logic(abbr., F-logic), that accounts in a clean and declarative fashion for most of the structural aspects of object-oriented and frame-based languages. These features include object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. In a sense, F-logic stands in the same relationship to the object-oriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete resolution-based proof theory. A small number of fundamental concepts that come from object-oriented programming have direct representation in F-logic; other, secondary aspects of this paradigm are easily modeled as well. The paper also discusses semantic issues pertaining to programming with a deductive object-oriented language based on a subset of F-logic.
Sequential random sampling
Authors: Ahrens J. H. , Dieter U.
Published: July 2002

Fast algorithms for selecting a random set of exactly
k
records from a file of
n
records are constructed. Selection is sequential: the sample records are chosen in the same order in which they occur in the file. All procedures run in
O(k)
time. The “geometric” method has two versions: with or without
O(k)
auxiliary space. A further procedure uses hashing techniques and requires
O(k)
space.
Pairing heaps
Authors: Stasko John T. , Vitter Jeffrey Scott
Published: July 2002

The pairing heap has recently been introduced as a new data structure for priority queues. Pairing heaps are extremely simple to implement and seem to be very efficient in practice, but they are difficult to analyze theoretically, and open problems remain. It has been conjectured that they achieve the same amortized time bounds as Fibonacci heaps, namely,
O
(log
n
)
time for
delete
and
delete_min and O(1) for all other operations, where n is the size of the priority queue at the time of the operation. We provide empirical evidence that supports this conjecture. The most promising algorithm in our simulations is a new variant of the twopass method, called auxiliary twopass. We prove that, assuming no decrease_key operations are performed, it achieves the same amortized time bounds as Fibonacci heaps.
Graphical interactive simulation input modeling with bivariate Bézier distributions
Authors: Wagner Mary Ann Flanigan , Wilson James R.
Published: July 2002

A graphical interactive technique for modeling bivariate simulation inputs is based on a family of continuous univariate and bivariate probability distributions with bounded support that are described by Be´zier curves and surfaces, respectively. This family of distributions has a natural, extensible parameterization so that all parameters have a meaningful interpretation; and the complete family is capable of accurately representing an unlimited variety of shapes for marginal distributions together with many common types of bivariate stochastic dependence. This approach to simulation input modeling is implemented in a Windows-based software system called PRIME-PRobabilistic Input Modeling Environment. Several examples illustrate the application of PRIME to subjective and data-driven estimation of bivariate distributions representing simulation inputs.
An experimental investigation of the interactive effects of interface style, instructions, and task familiarity on user performance
Authors: Lim Kai H. , Benbasat Izak , Todd Peter A.
Published: July 2002

Norman proposed a model describing the sequence of user activities involved in human-computer interaction. Through this model, Norman provides a rationale for why direct-manipulation interfaces may be preferred to other design alternatives. Based on
action identification theory
we developed several hypotheses about the operations of Norman's model and tested them in a laboratory experiment. The results show that users of a direct-manipulation interface and a menu-based interface did not differ in the total amount of time used to perform a task. However, with the direct-manipulation interface, more time is devoted to performing
motor actions
, but this is offset by shorter
nonmotor time
. Furthermore, there are significant interactions between task familiarity, instructions, and the type of interface, indicating that Norman's model may not hold under all conditions.
Computation of the incomplete gamma function ratios and their inverse
Authors: DiDonato Armido R , Morris Alfred H
Published: July 2002

An algorithm is given for computing the incomplete gamma function ratios
P
(
a
,
x
) and
Q>
(
a
,
x
) for
a
⪈ 0,
x
⪈ 0,
a
+
x
≠ 0. Temme's uniform asymptotic expansions are used. The algorithm is robust; results accurate to 14 significant digits can be obtained. An' extensive set of coefficients for the Temme expansions is included.

An algorithm, employing third-order Schröder iteration supported by Newton-Raphson iteration, is provided for computing
x
when
a
,
P
(
a
,
x
), and
Q
(
a
,
x
) are given. Three iterations at most are required to obtain 10 significant digit accuracy for
x
.
Two FORTRAN packages for assessing initial value methods
Authors: Enright W. H. , Pryce J. D.
Published: July 2002

We present a discussion and description of a collection of FORTRAN routines designed to aid in the assessment of initial value methods for ordinary differential equations. Although the overall design characteristics are similar to those of earlier testing packages [2,6] that were used for the comparison of methods [5,7], the details and objectives of the current collection are quite different. Our principal objective is the development of testing tools that can be used to assess the efficiency and reliability of a standard numerical method without requiring significant modifications to the method and without the tools themselves affecting the performance of the method.
Low power realization of finite state machines—a decomposition approach
Authors: Chow Sue-Hong , Ho Yi-Cheng , Hwang TingTing , Liu C. L.
Published: July 2002

We present in this article a new approach to the synthesis problem for finite state machines with the reduction of power dissipation as a design objective. A finite state machine is decomposed into a number of
coupled
submachines. Most of the time, only one of the submachines will be activated which, consequently, could lead to substantial savings in power consumption. The key steps in our approach are: (1) decomposition of a finite state machine into submachines so that there is a high probability that state transitions will be confined to the smaller of the submachines most of the time, and (2) synthesis of the coupled submachines to optimize the logic circuits. Experimental results confirmed that our approach produced very good results (in particular, for finite state machines with a large number of states.)