bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR-NQR Study of the Crossover from the Spin-Glass to the Superconducting Phase in La2-xSrxCuO4
Authors: Julien M.-H. , Carretta P. , Borsa F. , Rigamonti A.
Published: July 2002

139 La and 63 Cu NQR relaxation rates are used to obtain insights on the effects of itinerant holes on the magnetic in-plane correlation length, for x ≤ 0.04 in La 2-x Sr x CuO 4. For these concentrations, corresponding to spin-glass behavior at low temperature, evidence for the microsegregation of holes along stripes is presented. Preliminary relaxation results for an amount of Sr doping leading to superconductivity are also presented and discussed in terms of the crossover from the spin-glass to the underdoped superconducting regime: for x = 0.06 a slowing down of spin fluctuations is evidenced and superconductivity is found to coexist with spin-freezing.
CuK-EDGE STUDIES OF THE CHARGE CARRIES IN Th-DOPED CUPRATE SYSTEM R2-xThxCuO4-δ (R=Nd, Sm AND Gd)
Authors: LIANG G. , YI Y. , JARDIM R. F. , WANG L. V.
Published: July 2002

To further study the charge carrier concentration in electron doped cuprate superconductors. a systematic x-ray absorption near edge structure (XANES) measurement has been carried out on Th-doped superconductor system R 2-x Th x CuO 4-δ (R=Nd, Sm, and Gd). The XANES results show that, similar to the Ce-doped compounds, while the intensity of the Cu 1+4pπ feature increase with the increase of the Th doping level x, the intensities of the Cu 2+4pπ and 4pσ features decreases. This clearly indicates that the electrons doped by the Th atoms are injected into the local Cu 3d-orbitals. The normalized Cu 1+4pπ intensity data show that the Cu 1+ concentration in the Th-doped compound series with different R-elements is linearly proportional to the Th doping-level x. The data suggest that both Ce and Th donate the same fraction of electrons into the Cu sites.
MAGNETIC SCATTERING EFFECTS IN A QUASI-TWO-DIMENSIONAL DISORDERED ELECTRON SYSTEM
Authors: YANG Y. H.
Published: July 2002

The weak-localization correction to the conductivity for a quasi-two-dimensional disordered electron system is calculated in the presence of magnetic impurity scatterings. The analytical result is obtained as a function of the magnetic scattering time, and the interesting magnetic-scattering-dependent crossover behavior from 3D to 2D is discussed.
QUASI-PROBABILITY DISTRIBUTION FOR LAUGHLIN STATE VECTORS
Authors: FAN HONGYI , LIN JINGXIAN
Published: July 2002

Based on the gauge-invariant Wigner operator in <λ| representation (see Ref. 10), where the state |λ> can conveniently describe the motion of an electron in a uniform magnetic field, we provide an approach for identifying the corresponding state vector for Laughlin wave function and deriving the Wigner function (quasi-probability distribution) for the Laughlin state vector. The angular momentum-excited Laughlin state vectors are also obtained via <λ| representation.
Static and Dynamic Properties of a Two-Dimensional Charged Bose Fluid
Authors: Strepparola E. , Tosi M. P.
Published: July 2002

A complete solution of the Singwi–Tosi–Land–Sjölander approximation is given for the ground state and the elementary excitations of a fluid of charged bosons interacting via the two-dimensional ln (r) Coulomb potential at arbitrarily large coupling strength r s . The results are used to discuss the limitations of a static-mean-field approach in such a strongly correlated system.
PHASE TRANSITION INVESTIGATIONS IN POLYMER/LIQUID CRYSTAL COMPOSITE MATERIALS
Authors: MANAILA-MAXIMEAN DOINA , FURLANI MAURIZIO , BENA RODICA , MELLANDER BENGT-ERIK , ROSU CONSTANTIN , POP TATIANA , MOTOC CORNELIA
Published: July 2002

We prepared polymer dispersed liquid crystal (PDLC) composite films using polymethyl methacrylate (PMMA) and the ferroelectric liquid crystal (LC) Felix 015/000 (Hoechst) by the solvent-induced phase separation method. We studied the phase transitions by the thermally stimulated depolarization currents (TSDC) method and by differential scanning calorimetry (DSC), for the composite film and the corresponding liquid crystal. Polarized microscopy was also used to characterize the phase transitions. When the LC is mixed with the PMMA, its characteristic transition temperatures are shifted down a few degrees and the current peaks revealed by the TSDC method are broadened due to the dispersion of microdroplets and the consequential presence of a large interface between the LC and the polymer matrix.
A SEMANTIC INTERPRETER AND A COOPERATIVE RESPONSE GENERATOR FOR A ROBUST SPOKEN DIALOGUE SYSTEM
Authors: NAKAGAWA SEIICHI , KOGURE SATORU , ITOH TOSHIHIKO
Published: July 2002

In this paper, we describe a semantic interpreter and a cooperative response generator for a multimodal dialogue system which consists of speech input, touch screen input, speech output and graphical output. The dialogue system understands spontaneous speech which has many ambiguous phenomena such as interjections, ellipses, inversions, repairs, unknown words and so on, and responses to user for the utterance. But some utterances fail to be analyzed. This is caused due to "misrecognition" with the speech recognizer, "incompleteness" with the semantic interpreter and "lack of database" with the response generator. Therefore, we improved the semantic interpreter to build a more robust one. If a user's query does not have enough conditions/information to answer the question with the system, the dialogue manager should query the user to get the necessary conditions or to select the candidate. Further, if the system cannot retrieve any information related to the user's question, the generator should propose an alternative plan. Based on these considerations, we developed a cooperative response generator in the dialogue system. We report the evaluation results of the semantic interpreter and cooperative response generator in our dialogue system.
A 2-D HMM METHOD FOR OFFLINE HANDWRITTEN CHARACTER RECOGNITION
Authors: PARK HEE-SEON , SIN BONG-KEE , MOON JONGSUB , LEE SEONG-WHAN
Published: July 2002

In this paper we consider a hidden Markov mesh random field (HMMRF) for character recognition. The model consists of a "hidden" Markov mesh random field (MMRF) and an overlying probabilistic observation function of the MMRF. Just like the 1-D HMM, the hidden layer is characterized by the initial and the transition probability distributions, and the observation layer is defined by distribution functions for vector-quantized (VQ) observations.

The HMMRF-based method consists of two phases: decoding and training. The decoding and the training algorithms are developed using dynamic programming and maximum likelihood estimation methods. To accelerate the computation in both phases, we employed a look-ahead scheme based on maximum marginal it a posteriori probability criterion for third-order HMMRF. Tested on a larget-set handwritten Korean Hangul character database, the model showed a promising result: up to 87.2% recognition rate with 8 state HMMRF and 128 VQ levels.
HIERARCHICAL SHAPE DESCRIPTION AND SIMILARITY-INVARIANT RECOGNITION USING GRADIENT PROPAGATION
Authors: BEN-ARIE JEZEKIEL , WANG ZHIQIAN
Published: July 2002

This paper presents a novel hierarchical shape description scheme based on propagating the image gradient radially. This radial propagation is equivalent to a vectorial convolution with sector elements. The propagated gradient field collides at centers of convex/concave shape components, which can be detected as points of high directional disparity. A novel vectorial disparity measure called Cancellation Energy is used to measure this collision of the gradient field, and local maxima of this measure yield feature tokens. These feature tokens form a compact description of shapes and their components and indicate their central locations and sizes. In addition, a Gradient Signature is formed by the gradient field that collides at each center, which is itself a robust and size-independent description of the corresponding shape component. Experimental results demonstrate that the shape description is robust to distortion, noise and clutter. An important advantage of this scheme is that the feature tokens are obtained pre-attentively, without prior understanding of the image. The hierarchical description is also successfully used for similarity-invariant recognition of 2D shapes with a multi-dimensional indexing scheme based on the Gradient Signature.
SUBCRITICAL TRANSITION TOWARDS SPACE-TIME CHAOS
Authors: PASTUR L. , RIBOTTA R.
Published: July 2002

The subcritical transition towards space-time chaos of a nonlinear localized state (defined by well-defined fronts) is studied along the bifurcated hysteretic branch of the bifurcation. The experimental model system is the one-dimensional electroconvection of a nematic liquid crystal. The transition reveals an original cascade of bifurcations between front regimes, as well as a width-selection mechanism for the domains. A fifth-order Ginzburg–Landau equation reproduces most of the experimental observations.
DRIVING SYNCHRONIZATION OF SPATIOTEMPORAL CHAOS AND ITS APPLICATIONS IN CDMA COMMUNICATIONS
Authors: YONG REN , XIA YONGXIANG , SHAN XIUMING , JIAN YUAN
Published: July 2002

This paper investigates the driving synchronization of spatiotemporal chaos. Using this method, synchronization could be achieved efficiently. By improving the driving sequence generation method, the spatial periodicity in the original system is overcome. Large quantities of chaotic sequences are available, which possess the excellent properties expected in Code Division Multiple Access (CDMA) communications. These chaotic sequences can be used as the spreading sequences in place of the traditional pseudo-noise sequences. We also evaluate the performance of the chaotic CDMA communication systems and compute the average bit error rate caused by the multi-user interference and the noise in the channel. The theoretical and simulation results show the excellent performance of the scheme.
COMPLEXITY ANALYSIS AND CONTROL STRATEGY FOR BEAM HALO-CHAOS IN ADS
Authors: FANG JIN-QING , CHEN GUANRONG , LUO XIAO-SHU
Published: July 2002

Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry, medicine, and national defense. This article reviews the complexity of accelerator driven clean nuclear power system (ADS) as well as the associate physical mechanism for beam halo-chaos formation in high-intensity proton linear accelerator. Notably, some general engineering methods for chaos control have been developed in recent years, but they are generally unsuccessful for beam halo-chaos suppression due to many technical constraints. In this article, some of these technical problems are addressed. Particles-in-Cell (PIC) simulations are described, for exploring the nature of beam halo-chaos formation. Some efficient nonlinear control methods, including wavelet function feedback control, are reported for beam halo-chaos suppression. PIC simulations show that after control is applied to the initial proton beam with water bag or full Gauss distributions, the beam halo strength factor is quickly reduced to zero, and other statistical physical quantities of beam halo-chaos are also doubly reduced. These performed PIC simulation results demonstrate that the developed methods are very effective for halo-chaos suppression. Potential applications of the beam halo-chaos control methods are finally discussed.
BIFURCATION ANALYSIS OF A 2-DOF ROBOT MANIPULATOR DRIVEN BY CONSTANT TORQUES
Authors: VERDUZCO FERNANDO , ALVAREZ JOAQUÍN
Published: July 2002

The bifurcations of a two-degree-of-freedom (2-DOF) robot manipulator with linear viscous damping and constant torques at joints are analyzed at three equilibrium points. We show that, provided some conditions on the parameters are satisfied, two of these equilibria have a Jacobian matrix with a double zero eigenvalue and a pair of pure imaginary eigenvalues, while the other one has a quadruple zero eigenvalue. We use the center manifold theorem and the normal form theory to show the presence of different kinds of local bifurcations, ranging from codimension one (Hopf and fold), three (cusp and degenerate zero-Hopf), and higher (double zero, double zero-Hopf, triple zero, quadruple zero and Hopf–Hopf).
WINNING ENTRY OF THE K. U. LEUVEN TIME-SERIES PREDICTION COMPETITION
Authors: McNAMES J. , SUYKENS J. A. K. , VANDEWALLE J.
Published: July 2002

In this paper we describe the winning entry of the time-series prediction competition which was part of the International Workshop on Advanced Black-Box Techniques for Nonlinear Modeling, held at K. U. Leuven, Belgium on July 8–10, 1998. We also describe the source of the data set, a nonlinear transform of a 5-scroll generalized Chua's circuit. Participants were given 2000 data points and were asked to predict the next 200 points in the series.

The winning entry exploited symmetry that was discovered during exploratory data analysis and a method of local modeling designed specifically for the prediction of chaotic time-series. This method includes an exponentially weighted metric, a nearest trajectory algorithm, integrated local averaging, and a novel multistep ahead cross-validation estimation of model error for the purpose of parameter optimization.
STABILITY OF EQUILIBRIA OF NEURAL NETWORKS
Authors: CURRAN P. F. , CHUA L. O.
Published: July 2002

Sufficient conditions for local and global asymptotic stability of equilibria of some general classes of neural networks are presented. In the event that the interconnection matrix is block diagonally stable it is shown that the equilibrium is globally asymptotically stable if the cells are dissipative at the equilibrium. For a special class of networks the conditions of dissipativity are reduced to more readily-tested conditions of passivity. Equilibria are shown to be asymptotically stable essentially if the cells are locally passive.
SELF-ORGANIZED CRITICALITY MODEL FOR EARTHQUAKES: QUIESCENCE, FORESHOCKS AND AFTERSHOCKS
Authors: HAINZL S. , ZÖLLER G. , KURTHS J.
Published: July 2002

We introduce a crust relaxation process in a continuous cellular automaton version of the Burridge–Knopoff model. Analogously to the original model, our model displays a robust power law distribution of event sizes (Gutenberg–Richter law). The principal new result obtained with our model is the spatiotemporal clustering of events exhibiting several characteristics of earthquakes in nature. Large events are accompanied by a precursory quiescence and by localized fore- and aftershocks. The increase of foreshock activity as well as the decrease of aftershock activity follows a power law (Omori law) with similar exponents p and q. All empirically observed power law exponents, the Richter B-value, p and q and their variability can be reproduced simultaneously by our model, which depends mainly on the level of conservation and the relaxation time.
FORMALIZATION OF OBJECT BEHAVIOR AND INTERACTIONS FROM UML MODELS
Authors: SALDHANA JOHN ANIL , SHATZ SOL M. , HU ZHAOXIA
Published: July 2002

UML, being the industry standard as a common OO modeling language, needs a well-defined semantic base for its notation. Formalization of the graphical notation enables automated processing and analysis tasks. This paper describes a methodology for synthesis of a Petri net model from UML diagrams. The approach is based on deriving Object Net Models from UML statechart diagrams and connecting these object models based on UML collaboration diagram information. The resulting system-level Petri net model can be used as a foundation for formal Petri net analysis and simulation techniques. The methodology is illustrated on some small examples and a larger case study. The case study reveals some unexpected invalid system-state situations.
RESULTS CONCERNING THINNESS OF D0L LANGUAGES
Authors: HONKALA JUHA
Published: July 2002

A language L is called thin if there exists an integer n0such that for all n≥n0L contains at most one word of length n. We show that thinness is decidable for exponential D0L languages. We show also that Siegel's result concerning integral points on algebraic curves of positive genus can often be used to prove that a polynomially bounded HD0L language is thin.
ON THE UNDECIDABILITY OF FREENESS OF MATRIX SEMIGROUPS
Authors: CASSAIGNE JULIEN , HARJU TERO , KARHUMÄKI JUHANI
Published: July 2002

We slightly improve the result of Klarner, Birget and Satterfield, showing that the freeness of finitely presented multiplicative semigroups of 3×3 matrices over ℕ is undecidable even for triangular matrices. This is achieved by proving a new variant of Post correspondence problem. We also consider the freeness problem for 2×2 matrices. On the one hand, we show that it cannot be proved undecidable using the above methods which work in higher dimensions, and, on the other hand, we give some evidence that its decidability, if so, is also a challenging problem.
THE TOPOLOGICAL IHX RELATION
Authors: HABEGGER NATHAN
Published: July 2002

We give an exposition of the classification of finite type invariants of homology 3-spheres. A new conceptually-based proof of the topological IHX relation, needed to show the well-definedness of diagrams to manifolds, is given
CONSTRUCTING TQFTS FROM MODULAR FUNCTORS
Authors: GROVE JAKOB
Published: July 2002

We prove in this paper that any 2 dimensional modular functor satisfying that S1,1≠0 induces a family of 2+1 dimensionally topological quantum field theories. We do this for two kinds of modular functors namely a modular functor on the category of extended surfaces and a modular functor on the category of extended surfaces with marked points and directions. We follow the ideas of M. Kontsevich, [21], and K. Walker, [32] but we give proofs and provide details left out in [21] and [32]. Careful study also shows that more choices are needed to define the TQFT than it is revealed in [21] and [32]. On the other hand, relations found in [32] turns out not to be needed here.
A New Point of View in the Theory of Knot and Link Invariants
Authors: Labastida José M. F. , Mariño Marcos
Published: July 2002

Recent progress in string theory has led to a reformulation of quantum-group polynomial invariants for knots and links into new polynomial invariants whose coefficients can be understood in topological terms. We describe in detail how to construct the new polynomials and we conjecture their general structure. This leads to new conjectures on the algebraic structure of the quantum-group polynomial invariants. We also describe the geometrical meaning of the coefficients in terms of the enumerative geometry of Riemann surfaces with boundaries in a certain Calabi-Yau threefold.
RELATIVITY IN SPACETIMES WITH SHORT-DISTANCE STRUCTURE GOVERNED BY AN OBSERVER-INDEPENDENT (PLANCKIAN) LENGTH SCALE
Authors: AMELINO-CAMELIA GIOVANNI
Published: July 2002

I show that it is possible to formulate the Relativity postulates in a way that does not lead to inconsistencies in the case of spacetimes whose short-distance structure is governed by an observer-independent length scale. The consistency of these postulates proves incorrect the expectation that modifications of the rules of kinematics involving the Planck length would necessarily require the introduction of a preferred class of inertial observers. In particular, it is possible for every inertial observer to agree on physical laws supporting deformed dispersion relations of the type E2-c2 p2-c4m2 + f(E, p, m; L p ) =0, at least for certain types of f.
CURVATURE QUINTESSENCE
Authors: CAPOZZIELLO SALVATORE
Published: July 2002

The issues of quintessence and cosmic acceleration can be discussed in the framework of higher order theories of gravity. We can define effective pressure and energy density directly connected to the Ricci scalar of curvature of a generic fourth order theory and then ask for the conditions to get an accelerated expansion. Exact accelerated expanding solutions can be achieved for several fourth order theories so that we get an alternative scheme to the standard quintessence scalar field, minimally coupled to gravity, usually adopted. We discuss also conformal transformations in order to see the links of quintessence between the Jordan and Einstein frames.
EVALUATION OF SYSTEM PERFORMANCE THROUGH OPTIMIZING ASCENDENCY IN AN AQUATIC ECOSYSTEM MODEL
Authors: RAY SANTANU , BEREC LUDĚK , STRAŠKRABA MILAN , ULANOWICZ ROBERT E.
Published: July 2002

We develop a six-compartment model consisting of phosphorus, detritus, phytoplankton, zooplankton, planktonivorous fish and pisciphagous fish. In this model, we study the implications that the body sizes of phytoplankton and zooplankton have on the system dynamics. We use ascendency as a goal function or indicator of system performance. Ascendency quantifies growth and development of an ecosystem as a product of total system throughflow and the mutual information inherent in the pattern of internal system flows. Different physiological rate parameters of phytoplankton and zooplankton are assessed by means of allometric relationships applied to their body sizes. We let the phytoplankton body size range from 10 μm3to 107μm3and the zooplankton body size range from 10 μm3to 104μm3in volume. We also investigate the effects of phosphorus input conditions, corresponding to oligotrophic, mesotrophic and eutrophic systems on system dynamics. Ascendency (to be maximized over phytoplankton and zooplankton sizes) was computed after the system had reached a steady state. Since it always was a seasonal cycle, and the ascendency followed this behavior, we averaged the ascendency over 365 successive days (duration of one year) in the oscillatory phase. Under all types of nutrient conditions, the smallest phytoplankton size yielded the maximal values of the ascendency, while the corresponding zooplankton size varied. Under oligotrophic conditions, a phytoplankton size of 10 μm3combined with a zooplankton size of 101.25μm3to give the maximum value of the ascendency. Under mesotrophic and eutrophic conditions, maxima were obtained for zooplankton sizes 102.26μm3and 103.20μm3, respectively.
A PROBABILITY ANALYSIS OF HEART RATE VARIABILITY FOR HEART TRANSPLANT AND MYOCARDIAL INFARCTION PATIENTS AND FOR HEALTHY SUBJECTS
Authors: SAERMARK K. , LEWKOWICZ M. , LEVITAN J. , MOELGAARD H. , BOBERG B. , PEHRSSON S. , THOMSEN P. E. BLOCH
Published: July 2002

We present a probability analysis of RR interval series. The analysis is based on a subdivision of the RR interval series into segments — here called m-segments — ranging from one local RR maximum value to the consecutively following local RR maximum value; such segments represent full cycles of acceleration followed by deceleration of the heart rate. We analyze the properties of m-segments in terms of the probability of observing j RR values in the segment and in terms of the probability of observing a change of Δj in going from one m-segment to the following m-segment. We also calculate the rms-values, σm, of the m-segments and introduce an entropy measure to characterize the RR interval series. Further, we present a simple model for phase-space-trajectory plots for RR interval series and an estimate of the spectral properties in terms of the parameters j and σm. The results are based on 24-hour RR interval series for ten heart transplant patients, with a total of 23 recordings, for 326 myocardial infarction patients and 104 healthy subjects. The results obtained show characteristic differences between the behavior of the three groups, but no attempt at a clinical interpretation is made.
COMPUTATION OF NOISE DIRECTIONALITY, COHERENCE AND ARRAY RESPONSE IN RANGE DEPENDENT MEDIA WITH CANARY
Authors: HARRISON C. H. , BRIND R. , COWLEY A.
Published: July 2002

The ambient noise model CANARY calculates noise coherence and array noise response by treating the noise sources as surface distributions rather than points. This assumption leads to simplification of the propagation, even in range-dependent environments, and by allowing variations in the source density one can represent distant storms or groups of ships. Included is a description of the numerical algorithms used to calculate coherence. Some recently developed analytical solutions for uniform source distributions and uniformly sloping seabed3 are used as test cases for CANARY. Some additional examples demonstrate CANARY's performance in more realistic environments and conditions including wind and shipping sources, and comparisons are made with the noise model RANDI.
A SIMPLE REGULARIZATION METHOD FOR SOLVING ACOUSTICAL INVERSE SCATTERING PROBLEMS
Authors: PIANA MICHELE
Published: July 2002

The problem of determining the shape of an object from far-field data is considered. We present a method, originally formulated in Ref. 1 and furtherly modified in Ref. 3, for the solution of this ill-posed nonlinear inverse problem whose main features are:

• the method is exact, that is no low- or high-frequency approximation is considered;

• it is not necessary to know the number of scatterers and whether or not the scatterers are penetrable by the waves;

• if the medium is not penetrable, it is not necessary to know whether the obstacle is sound-hard or sound-soft;

• in the case of an inhomogeneous scatterer, the method provides the shape of the inhomogeneity.

The method is particularly simple since it requires only the solution of a linear Fredholm integral equation of the first kind whose integral kernel is the far-field pattern. The numerical instability due to ill-conditioning can be reduced by using regularization algorithms such as Tikhonov method where the regularization parameter is chosen by using Morozov's discrepancy principle generalized to the case where the noise affects the kernel of the integral operator.
A WIDE-ANGLE PARABOLIC EQUATION FOR ACOUSTIC WAVES IN INHOMOGENEOUS MOVING MEDIA: APPLICATIONS TO ATMOSPHERIC SOUND PROPAGATION
Authors: DALLOIS LAURENT , BLANC-BENON PHILIPPE , JUVÉ DANIEL
Published: July 2002

Two new derivations of "vector" parabolic equations (PE) for use in acoustic propagation have recently been published. In these cases, PEs have been derived from first principles and incorporate velocity fluctuations of the medium as two additional vector terms. In the simpler case, large spatial-scale velocity fluctuations can be accommodated. In the more general case, multi-scale velocity fluctuations can be accommodated.

In this paper we report on a series of two-dimensional numerical experiments which compares sound propagation predicted from traditional PEs with sound propagation predicted from these two "vector" PEs. Two types of velocity fields are simulated. One, suitable for approximating an atmospheric boundary layer, is a field in which velocity has only a horizontal component, but whose magnitude can depend on height, i.e., v=vx(z). The other is a field having random spatial fluctuations over a range of length scales and could be suggestive of atmospheric turbulence. In both cases celerity inhomogeneities are also included.

Results suggest that at least, in two dimension, the standard PE using an effective index of refraction is not accurate to describe the effects of the mean and turbulent velocity on sound propagation near the ground. We suspect that in three-dimensional problems, the added terms in the "vector" PEs will significantly increase in importance.
ASSESSMENT OF 3-D EFFECTS IN THE KEY WEST LWAD EXPERIMENT
Authors: PORTER MICHAEL B. , TATTERSALL MATT , IANNIELLO J. P.
Published: July 2002

The role of 3-D effects has long been debated in the ocean acoustics community. Typically, 3-D problems are handled in an approximation that uses a fan of bearing lines to build up a 3-D image of the acoustic field with many 2-D slices. This is the so-called N by 2-D approach and it is probably safe to say it is adequate for simple calculations of the SONAR range-of-the-day. On the other hand, acoustic models are now finding an important role in matched-field processing (MFP) where they are integrated with the signal processing to correct for the channel effects. These applications demand much more from the models but, somewhat surprisingly, recent broadband experiments have revealed that the models are up to the task. The main features of the echo patterns are well-predicted by such models and can be reliably exploited, at least in areas where the ocean bottom is fairly flat. The challenge now is to push MFP to more realistic scenarios with complicated topography and potential 3-D effects. One phase of the December 1997 Key West LWAD (Littoral Warfare Advance Development) experiment was designed to address exactly this issue. We use this Key West scenario as a backdrop to discuss modeling approaches combining beams and modes and the impact of the resulting 3-D variation on MFP for towed arrays.
SIX BOUNDARY ELEMENTS PER WAVELENGTH: IS THAT ENOUGH?
Authors: MARBURG STEFFEN
Published: July 2002

The commonly applied rule of thumb to use six (linear) elements per wavelength in linear time-harmonic acoustics is discussed in this paper. In a survey of related work, rules of element design in computational acoustics are collected. This is followed by a brief review of the boundary element method and a more detailed presentation of boundary element interpolation functions. Constant, bilinear and biquadratic interpolation polynomials are used on triangular and quadrilateral elements. In the investigation of a long duct, the numeric solution of the three dimensional problem is compared with the analytic solution. The performance of triangular and quadrilateral, constant, bilinear and biquadratic elements is compared. The error of the numeric solution is calculated in the maximum norm and the Euclidean norm on the surface and at internal points. It is estimated how many elements per wavelength are required to remain below certain error bounds of the sound pressure magnitude. Finally, a sedan cabin compartment is analyzed using different meshes. Again, performance of constant, bilinear and biquadratic elements is discussed.
AN APPROACH FOR COMBINING LINGUISTIC AND NUMERICAL INFORMATION BASED ON THE 2-TUPLE FUZZY LINGUISTIC REPRESENTATION MODEL IN DECISION-MAKING
Authors: HERRERA F. , MARTINEZ L.
Published: July 2002

In this paper we shall develop a procedure for combining numerical and linguistic information without loss of information in the transformation processes between numerical and linguistic information, taking as base for representing the information the 2-tuple fuzzy linguistic representation model. We shall analyze the conditions to impose the linguistic term set in order to ensure that the combination procedure does not produce any loss of information. Afterwards the aggregation process will be applied to a decision procedure over a multi-attribute decision-making problem dealing with numerical and linguistic information, that is, with qualitative and quantitative attributes.
THE DIFFERENCE BETWEEN THE SURFACE RECONSTRUCTIONS OF AlAs(001) AND GaAs(001)
Authors: SHEN JIANHUA , JIANG PING , XIE XIDE
Published: July 2002

AlAs(001) is compared with GaAs(001) by ab initio pseudopotential total energy calculation. The results show that either similarities or differences in the stability of the surface reconstructions are obvious. On the Al-rich AlAs surface the reconstruction (2×1)/c (2×2) has an obvious energetic advantage. In this reconstruction the topmost Al atoms abnormally locate below the As atomic layer. Besides, on the As-rich GaAs surface a metastable reconstruction phase of γ(2×4) appears if the surface coverage of As atoms is less than 1, while on the AlAs surface it is fully dimerized (2×1) phase more stable. In addition the thermodynamical analysis also indicates that in the mid-temperature range of MBE growth (e.g. 600°C with As 2 pressure of 2 × 10-6 τ) this (2×1) phase is stable. Further calculations show that 0.2–1 monolayer of Ga atoms deposited on AlAs surface will result in γ(2×4) phase rather than (2×1) phase, while the deposited Ga atoms on the AlAs surface do not go below the topmost As atomic layer. The plausible conclusion is that formation of (2×1) phase on As-rich AlAs surface and the inner location of Al atoms on Al-rich (2×1)/c(2×2) reconstruction surface could be closely related to the obviously different modes of MBE growth on AlAs and GaAs surface, in the mid-temperature range.
MAGNETIC RESONANCE ANGIOGRAPHY OF THE FOREARM AND HAND IN CHILDREN
Authors: Kawabata Hidehiko , Matsui Yoshito , Kitano Motohiro
Published: July 2002

A two-dimensional time-of-flight magnetic resonance angiography was performed in 29 arms in 25 pediatric patients with congenital hand abnormalities, whose average age was three years and eight months. Venous structures were eliminated with presaturation technique and the remaining arterial system was evaluated. Magnetic resonance angiography demonstrated major arteries in the forearm well but not their branches. Even the biggest branch of the artery sometimes could not be detected. Magnetic resonance angiography and Allen test were consistent in determining patency of the palmar arch in 62% of the cases but the sensitivity was only 28%. Our experience showed that non-invasive, convenient, two-dimensional time-of-flight magnetic resonance angiography was useful for detecting continuity and spatial localisation of the major arteries in a child's forearm. However, it was not a complete alternative to conventional angiography and was unsatisfactory in delineating the vascular anatomy in the hand.
GENE THERAPY FOR RHEUMATOID ARTHRITIS
Authors: Gouze Jean-Noel , Ghivizzani Steven C. , Gouze Elvire , Palmer Glyn. D. , Betz Oliver B. , Robbins Paul D. , Evans Christopher H. , Herndon James H.
Published: July 2002

Advances in understanding the biology of rheumatoid arthritis (RA) have opened new therapeutic avenues. One of these, gene therapy, involves the delivery to patients of genes encoding anti-arthritic proteins. This approach has shown efficacy in animal models of RA, and the first human, phase I trial has just been successfully completed. Hand surgery featured prominently in this pioneering study, as a potentially anti-arthritic gene encoding the interleukin-1 receptor antagonist was transferred to the metacarpophalangeal joints of subjects with RA one week before total joint arthroplasty. This study has confirmed that it is possible to transfer genes safely to human joints. It should pave the way for additional application of gene therapy to arthritis and other orthopaedic conditions.
ANGIOLEIOMYOMA IN HAND — A CASE REPORT
Authors: Utukuri M. M. , Srinivasan M. S.
Published: July 2002

Angioleiomyomas are benign tumours arising from smooth muscle and composed of vascular tissue. They rarely occur in the hand. There are only about 100 such cases reported in English literature. This is because of the paucity of smooth muscle in the hand. The tumour is rarely diagnosed before surgery. The treatment is excision and ligation of feeder vessels.

A slow growing tumour in the right hand in a 73-year-old gentleman which turned out to be an angioleiomyoma is presented in this paper.
COMPUTERS AS TOOLS OR AS SOCIAL ACTORS? — THE USERS' PERSPECTIVE ON ANTHROPOMORPHIC AGENTS
Authors: SCHAUMBURG HEIKE
Published: July 2002

Surprising findings showing that many basic rules of social interaction among humans also apply to the interaction of humans with computers26 have encouraged interface researchers to proclaim a new paradigm in human computer interface design: the social interface. Reeves and Nass' findings have especially given a new impetus to research on anthropomorphic agents, suggesting that furnishing an agent with a human-like interface could be an effective way to enhance agent usability. Little research exists however, to verify this claim. This study seeks to illuminate user responses to an anthropomorphic agent if it is used on a daily basis. It examines the influence of traditional usability variables such as control, understanding, trust, and distraction on the acceptance of an anthropomorphic interface. Kaasinen8 as well as Wexelblat and Maes36 emphasize that the acceptance of agents (whether or not they have an anthropomorphic interface) strongly depends on these traditional usability variables.

As subject for this study, a commonly used anthropomorphic agent, the Microsoft Office Assistant, was selected. Using a questionnaire that was distributed through email and the World Wide Web as well as on paper, 105 users of the Microsoft Office Suite were asked about their use and acceptance of the Office Assistant. It turned out that the Office Assistant feature was rejected by the majority of the users. As a feature to troubleshoot problems, it was perceived as inefficient. Also, from a "social" perspective, it was rated as not particularly engaging or motivating. Multiple regression analysis revealed that variables influencing the use and the acceptance of the Office Assistant were distraction and trust. Only those users who felt distracted by the assistant and who did not trust in its capability to solve their problems rejected the Office Assistant. It is concluded that to ensure agent usability, its design should emphasize assistance with the user's task over social mimicry. If design efforts to furnish the agent with social traits interfere with the user's principal goal, it is likely that the agent will be rejected.
SELECTIVELY MATERIALIZING DATA IN MEDIATORS BY ANALYZING USER QUERIES
Authors: ASHISH NAVEEN , KNOBLOCK CRAIG , SHAHABI CYRUS
Published: July 2002

There is currently great interest in building information mediators that can integrate information from multiple data sources such as databases or Web sources. The query response time for such mediators is typically quite high, mainly due to the time spent in retrieving data from remote sources. We present an approach for optimizing the performance of information mediators by selectively materializing data. We first present our overall framework for materialization in a mediator environment. The data is materialized selectively. We outline the factors that are considered in selecting data to materialize. We present an algorithm for identifying classes of data to materialize by analyzing one of the factors which is the distribution of user queries. We present results with an implemented version of our optimization system for the Ariadne information mediator, which show the effectiveness of our algorithm in extracting patterns of frequently accessed classes from user queries. We also demonstrate the effectiveness of approach in optimizing mediator performance by materializing such classes.
CONSTANT ELASTICITY OF VARIANCE OPTION PRICING MODEL WITH TIME-DEPENDENT PARAMETERS
Authors: LO C. F. , YUEN P. H. , HUI C. H.
Published: July 2002

This paper provides a method for pricing options in the constant elasticity of variance (CEV) model environment using the Lie-algebraic technique when the model parameters are time-dependent. Analytical solutions for the option values incorporating time-dependent model parameters are obtained in various CEV processes with different elasticity factors. The numerical results indicate that option values are sensitive to volatility term structures. It is also possible to generate further results using various functional forms for interest rate and dividend term structures. Furthermore, the Lie-algebraic approach is very simple and can be easily extended to other option pricing models with well-defined algebraic structures.
EQUITY ALLOCATION AND PORTFOLIO SELECTION IN INSURANCE: A SIMPLIFIED PORTFOLIO MODEL
Authors: TAFLIN ERIK
Published: July 2002

A quadratic discrete time probabilistic model, for optimal portfolio selection, under risk constraint, is introduced in the context of (re-) insurance and finance. The portfolio is composed of contracts with arbitrary underwriting and maturity times. For positive values of underwriting levels, the expected value of the accumulated final result is optimized under constraints on its variance and on annual Returns On Equity. Existence of a unique solution is proved and a Lagrangian formalism is given. An effective method for solving the Euler-Lagrange equations is developed. The approximate determination of the multipliers is discussed. This basic model, which can include both assets and liabilities, is an important building block for more general models, with constraints also on non-solvency probabilities, market-shares, short-fall distributions and Values at Risk.
International Transmission of Stock Price Movements among Taiwan and Its Trading Partners: Hong Kong, Japan and the United States
Authors: Chang Tsangyao , Nieh Chien-Chung
Published: July 2002

This study uses a cointegration analysis and vector autoregressive models to investigate the transmission of stock price movements among Taiwan and its major trading partners, Hong Kong, Japan and the United States. The results of Johansen cointegration test indicate that four stock markets considered are cointegrated with one cointegrating vector, which violates the semi-strong form of the market efficiency hypothesis. The results from Granger-causality test based on error-correction models suggest the relative leading roles of the U.S. and Japanese markets in driving fluctuations in the other two markets. In order to capture the impacts of the economic shocks, two dummy variables are incorporated into the models taking into account the U.S. stock crash of October 1997 (D97) and the previous spreading Asian finance crises (Dac). The results indicate that D97 significantly affects the U.S. stock market, but shows no significant impact on the others. The Dac, however, shows significant impacts on both the Japanese and the U.S. markets. The robustness of the relative leading roles of the U.S. and Japanese markets are further supported by the variance decompositions and impulsive response functions indicators. The Taiwan and Hong Kong markets are somewhat affected more by regional countries such as Japan than by the U.S.
FAST, MINIMAL, AND OBLIVIOUS ROUTING ALGORITHMS ON THE MESH WITH BOUNDED QUEUES
Authors: LITMAN AMI , MORAN-SCHEIN SHIRI
Published: July 2002

This paper studies fast, deterministic permutation routing algorithms with bounded queues on the n×n mesh. Our main result is an O(n)-step, strongly-dimensional (and thus also source-oblivious and minimal) permutation routing algorithm. This algorithm works under a relaxed model in which nodes can freely send data to their neighbors. In a more prevalent model, the standard model, data may be sent only when accompanied by a packet. Under this model we present the following two algorithms: an O(n log n)-step strongly-dimensional algorithm and an O(n)-step oblivious and weakly-dimensional (and thus also minimal) algorithm. As said, all these algorithms store only O(1) packets in a node. Moreover, they use only O( log n) state bits in a node and transfer only O( log n) data bits on an edge in a step. All our routing algorithms are based on the following new technique of open-loop flow control. An algorithm is composed of two stages: setup and transportation. The setup stage computes certain values and stores them in the network. In particular, it computes a rational number α(e) for certain critical edges e. The transportation stage moves the packets to their destinations. It uses the computed values to slow the packets so that the traffic on each critical edge e is bounded byα(e); that is, at most ⌈α(e) · l⌉ packets traverse e during any l consecutive steps. This bounded on the burstiness of the traffic enables the algorithm to avoid hot spots and maintain bounded queues. The algorithm achieves this by an open-loop control; that is, during this stage no information is transferred in a direction opposite to that of the packets. An additional novelty of our algorithms is the application of a dynamic routing problem to solve a static one. The dynamic problem in question seems easy, as its networks is just a linear array. We show, however, that this problem is beyond the scope of the Adversarial Queuing Theory.
AUTOREGRESSIVE ANALYSIS FOR THE DETECTION OF EARTHQUAKES WITH A RING LASER GYROSCOPE
Authors: McLEOD DUNCAN P. , KING B. TOM , STEDMAN GEOFFREY E. , SCHREIBER K. ULRICH , WEBB TERRY H.
Published: July 2002

The second-order autoregressive AR(2) model is used to analyze rotational data for seismic events captured by a large ring laser gyroscope. Both the Sagnac frequency and linewidth estimates obtained from this model sense the rotational components of seismic waves. An event of magnitude ML= 6.5 at a distance of D = 5.4° from a large ring laser gyroscope operating at its quantum limit is used to compare the AR(2) model with the previous analytical phase angle method of analysis. The frequency, linewidth and analytic phase angle data each satisfactorily estimate the rotation magnitude. The direct detection of rotational motion in the P wave coda is observed, demonstrating the conversion to transverse S wave polarizations by the local geology.
LOCAL LIMIT THEOREMS FOR PARTIAL SUMS OF STATIONARY SEQUENCES GENERATED BY GIBBS–MARKOV MAPS
Authors: AARONSON JON , DENKER MANFRED
Published: July 2002

We introduce Gibbs–Markov maps T as maps with a (possibly countable) Markov partition and a certain type of bounded distortion property, and investigate its Frobenius–Perron operator P acting on (locally) Lipschitz continuous functions ϕ. If such a function ϕ belongs to the domain of attraction of a stable law of order in (0,2), we derive the expansion of the eigenvalue function t↦λ(t) of the characteristic function operators Ptf=Pf exp [i< t,ϕ> (perturbations of P) around 0. From this representation local and distributional limit theorems for partial sums ϕ+…+ϕ◦ Tn are easily obtained, provided ϕ is aperiodic. Applications to recurrence properties of group extensions are also given.
DYNAMICAL PROPERTIES OF LÉVY PROCESSES IN LIE GROUPS
Authors: LIAO MING
Published: July 2002

Let ϕt be a Lévy process in a semisimple Lie group G of noncompact type regarded as a stochastic flow on a homogeneous space of G, called a G-flow. We will determine the Lyapunov exponents and the stable manifolds of ϕt, and the stationary points of an associated vector field. As examples, SL (d,R)-flows and SO (1,d)-flows on SO (d) and Sd - 1 are discussed in details.
The generation of binary trees as a numerical problem
Authors: Sprugnoli Renzo
Published: July 2002

The problem of generating random, uniformly distributed, binary trees is considered. A closed formula that counts the number of trees having a left subtee with
k
-1 nodes (
k
=1,2,...,
n
) is found. By inverting the formula, random trees with
n
nodes are generated according to the appropriate probability distribution, determining the number of nodes in the left and right subtrees that can be generated recursively. The procedure is shown to run in time
O(n)
, occupying an extra space in the order of
O(√n)
A new approach to I/O performance evaluation
Authors: Chen Peter M. , Patterson David A.
Published: July 2002

Current I/O benchmarks suffer from several chronic problems: they quickly become obsolete; they do not stress the I/O system; and they do not help much in understanding I/O system performance. We propose a new approach to I/O performance analysis. First, we propose a self-scaling benchmark that dynamically adjusts aspects of its workload according to the performance characteristic of the system being measured. By doing so, the benchmark automatically scales across current and future systems. The evaluation aids in understanding system performance by reporting how performance varies according to each of five workload parameters. Second, we propose predicted performance, a technique for using the results from the self-scaling evaluation to estimate quickly the performance for workloads that have not been measured. We show that this technique yields reasonably accurate performance estimates and argue that this method gives a far more accurate comparative performance evaluation than traditional single-point benchmarks. We apply our new evaluation technique by measuring a SPARCstation 1+ with one SCSI disk, an HP 730 with one SCSI-II disk, a DECstation 5000/200 running the Sprite LFS operating system with a three-disk disk array, a Convex C240 minisupercomputer with a four-disk disk array, and a Solbourne 5E/905 fileserver with a two-disk disk array.