bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPLEMENTARY SURFACE INVESTIGATION OF DIAMOND BY SCANNING THERMAL MICROSCOPY AND SCANNING NEAR-FIELD CATHODOLUMINESCENCE
Authors: ALTES A. , HEIDERHOFF R. , BALK L. J.
Published: July 2002

The interest in diamond windows for the application of high power radiation technology is increasing continuously due to its outstanding thermal and opto-electronic properties. In order to analyze the surface properties of very highly polished polycrystalline diamond in the sub-micrometer down to nanometer regime, two different near-field microscopy techniques have been employed.

By using a Scanning Thermal Microscope (SThM) it is possible to uncover the varying thermal conductivity of different diamond grains. Dissimilar thermal surface properties within diamond grains have been measured with a resolution in the nm regime. Beside the fact of determining a small surface thermal conductivity compared to the well known data of bulk material, the thermal conductivity of inferior and superior diamond quality is separated quantitatively. Additionally the opto-electronic properties of the polished diamond have been investigated by Scanning Near-Field Cathodoluminescence (NF-CL). This measurement technique allows the detection of the distribution of dislocations within diamond grains with a resolution of less than 100nm. The comparison of these results, obtained by SThM and NF-CL, demonstrates a fine alignment in representing crystal lattice imperfections.
SUSCEPTIBILITY AND VERTEX CORRECTIONS FOR A SQUARE FERMI SURFACE
Authors: DJAJAPUTRA DAVID , RUVALDS JOHN
Published: July 2002

We investigate the response of an electron system which exhibits ideal nesting features. Using the standard Matsubara formalism we derive analytic expressions for the imaginary and real parts of the bare particle–hole susceptibility. The imaginary part has sharp peaks whose maxima at the nesting momenta approximately scale with (ω/T). The peak lineshapes resemble neutron scattering data on chromium and some copper oxide superconductors. The real part of the bare susceptibility at the nesting vectors diverges logarithmically at low temperatures. Analytic formulas for the first vertex correction to the susceptibility are derived for a Hubbard interaction and its momentum and temperature variations are calculated numerically. This term detracts substantially from the ordinary RPA terms for intermediate values of the Coulomb repulsion. Exact cancellation of a certain class of diagrams at half filling is shown to result from particle–hole symmetry. We discuss the consequences of these results for spin fluctuation theories of high temperature superconductors and spin density wave instabilities.
INTERACTIONS AND MOLECULAR ORIENTATIONS IN SOLID C60
Authors: LAUNOIS P. , RAVY S. , MORET R.
Published: July 2002

In spite of recent progress, our present understanding of the intermolecular interactions in solid C 60 is still imperfect and no single model is able to describe correctly its whole physical properties. These interactions induce elaborate orientational properties which have motivated thorough investigations. In this review paper we concentrate on the orientational properties in the high temperature phase. It is shown how the preferred orientations and the orientational correlations could be accessed through the analysis of the Bragg and diffuse scattering intensity data. The results obtained using either mean-field treatments or molecular dynamics calculations have brought information on the existence of competing local orientational orders. The scattering data have also been exploited to discriminate between different models of intermolecular potential. Within the mean-field treatment, necessary conditions for any model to satisfy scattering results are put forward.
ESR STUDIES ON GMR RELATED MATERIALS II: ESR of Mn IN La0.97Ca0.03MnO3
Authors: ARAI N. , KOUZUKI A. , SUGAWARA K.
Published: July 2002

ESR measurements have been carried out for La 0.97 Ca 0.03 MnO 3 at temperatures from 4 K up to 760 K. below ≃243 K , two kinds of spectra, the high-field and low-field signals, are observed down to 96 and 4 K, respectively. They are assumed to be due to Mn 4+ and Mn 3+ ions, respectively. From the g-shifts of the high-field ( Mn 4+) signals, the magnetic interaction coefficient between Mn 4+ and Mn 3+ spins is estimated. Clear single ESR was observed above ≃255 K , and its linewidth and intensity are obtained as a function of temperature. The linewidth nearly follows exp (-550/T), and the intensity gradually deviates from Curie's law below ≃550 K , presumably due to the spin-cluster formation.
THE FINITE-SIZE PROPERTIES OF THE SQUARE LATTICE QUANTUM HEISENBERG ANTIFERROMAGNET
Authors: SONG YUN
Published: July 2002

We study the spin-1/2 square lattice Heisenberg antiferromagnets with finite size by the nonlinear spin-wave theory. At low temperatures, the effects of the lattice size (L×L) on the spin-wave velocity and the staggered magnetization are obtained, respectively. We find that the staggered magnetization is very sensitive to the lattice size, while the finite size effect on the spin-wave velocity is weak. Moreover, the temperature dependence of the correlation length is also discussed. The results we have obtained are in agreement with the results of experiments and numerical simulations.
PREPARATION OF ADHERENT MnSix FILMS
Authors: HOU Q. R. , WANG Z. M. , CHEN Y. B. , HE Y. J.
Published: July 2002

The adhesion of manganese silicide ( MnSi x) films on silicon and glass substrates is studied by using the micro-scratch method. The films were prepared by electron beam evaporation and thermal evaporation. To improve adhesion of the films, several techniques including ion bombardment, increasing substrate temperature, and insertion of a silicon intermediate layer were used. Finally, adherent MnSi x(x~1.7) films were prepared through solid phase reaction as well as reactive deposition. The hardness and modulus of the MnSi x(x~1.7) film were measured by a nano-indenter and the values are 8.8±1.0 GPa and 141±15 GPa, respectively.
Semiclassical Aspects of Quantum Mechanics by Classical Fluctuations
Authors: de Martino Salvatore , de Siena Silvio , Illuminati Fabrizio
Published: July 2002

Building on a model recently proposed by F. Calogero, we postulate the existence of a universal Keplerian tremor for any stable classical system. Deriving the characteristic unit of action α for each classical interaction, we obtain in all cases α≅h, the Planck action constant, suggesting that quantum corrections to classical dynamics can be simulated through a fluctuative hypothesis of purely classical origin.
A NOTE ON GENERALIZED SUPERPOSITION OF COHERENT STATES
Authors: RAGI R. , BAGNATO V. S. , BASEIA B.
Published: July 2002

In this comment we present an improvement of our recent proposal [Int. J. Mod. Phys.B12, 1495 (1998)] to generate a generalized superposition of two coherent states. The basic idea here is to use a dispersive atom-field interaction together with a single atom quantum state engineering.
TRACKING AND SURVEILLANCE IN WIDE-AREA SPATIAL ENVIRONMENTS USING THE ABSTRACT HIDDEN MARKOV MODEL
Authors: BUI HUNG H. , VENKATESH SVETHA , WEST GEOFF
Published: July 2002

In this paper, we consider the problem of tracking an object and predicting the object's future trajectory in a wide-area environment, with complex spatial layout and the use of multiple sensors/cameras. To solve this problem, there is a need for representing the dynamic and noisy data in the tracking tasks, and dealing with them at different levels of detail. We employ the Abstract Hidden Markov Models (AHMM), an extension of the well-known Hidden Markov Model (HMM) and a special type of Dynamic Probabilistic Network (DPN), as our underlying representation framework. The AHMM allows us to explicitly encode the hierarchy of connected spatial locations, making it scalable to the size of the environment being modeled. We describe an application for tracking human movement in an office-like spatial layout where the AHMM is used to track and predict the evolution of object trajectories at different levels of detail.
AN INTRODUCTION TO HIDDEN MARKOV MODELS AND BAYESIAN NETWORKS
Authors: GHAHRAMANI ZOUBIN
Published: July 2002

We provide a tutorial on learning and inference in hidden Markov models in the context of the recent literature on Bayesian networks. This perspective makes it possible to consider novel generalizations of hidden Markov models with multiple hidden state variables, multiscale representations, and mixed discrete and continuous variables. Although exact inference in these generalizations is usually intractable, one can use approximate inference algorithms such as Markov chain sampling and variational methods. We describe how such methods are applied to these generalized hidden Markov models. We conclude this review with a discussion of Bayesian methods for model selection in generalized HMMs.
AN OVERVIEW OF MORPHOLOGICAL SEGMENTATION
Authors: MEYER FERNAND
Published: July 2002

Mathematical morphology offers a rich framework for segmenting images and video sequences. We propose a unified presentation of these tools, expressed as a small number of distance transforms on graphs. The classical approach based on watershed and markers is reinterpreted in a multiscale framework and new results are presented, considerably enlarging the palette of available tools.
PALMPRINT IDENTIFICATION BY FOURIER TRANSFORM
Authors: LI WENXIN , ZHANG DAVID , XU ZHUOQUN
Published: July 2002

Palmprint identification refers to searching in a database for the palmprint template, which is from the same palm as a given palmprint input. The identification process involves preprocessing, feature extraction, feature matching and decision-making. As a key step in the process, in this paper, we propose a new feature extraction method by converting a palmprint image from a spatial domain to a frequency domain using Fourier Transform. The features extracted in the frequency domain are used as indexes to the palmprint templates in the database and the searching process for the best match is conducted by a layered fashion. The experimental results show that palmprint identification based on feature extraction in the frequency domain is effective in terms of accuracy and efficiency.
PARAMETRICALLY COUPLED SINE MAP NETWORKS
Authors: LEE GEEHYUK , FARHAT NABIL H.
Published: July 2002

Due to an inversion symmetry and a bimodal nature, the sine map, defined in R, exhibits bistability which is subject to an attractor-merging crisis. Such dynamical characteristics of the sine map suggest that it would be a promising candidate as a building block of an artificial neural network that can produce a binary associative memory. To test this idea, we designed and studied two types of Parametrically Coupled Sine Map Network. In the PCSMN-1, the amplitude of the sine function is used to control the bistability, whereas, in the PCSMN-2, an offset parameter that is added to the sine function is used to control the bistability. In both networks, the weight matrix is determined by the Hebbian rule, and coupling between the maps is accomplished via their control or bifurcation parameters; the control parameter of each sine map is continuously updated by the weighted sum of the state variables of all maps connecting to it. In the numerical study of their associative dynamics, the networks exhibited unique, desirable dynamical features that are missing in fixed-point based networks such as the Hopfield network. In addition to the potential advantage of such dynamical features in computational applications, they bring to mind some recent experimental findings concerning the neuronal activities in the brain.
PARTIAL SYNCHRONIZATION OF NONIDENTICAL CHAOTIC SYSTEMS VIA ADAPTIVE CONTROL, WITH APPLICATIONS TO MODELING COUPLED NONLINEAR SYSTEMS
Authors: WAGG DAVID J.
Published: July 2002

We consider the coupling of two nonidentical dynamical systems using an adaptive feedback linearization controller to achieve partial synchronization between the two systems. In addition we consider the case where an additional feedback signal exists between the two systems, which leads to bidirectional coupling. We demonstrate the stability of the adaptive controller, and use the example of coupling a Chua system with a Lorenz system, both exhibiting chaotic motion, as an example of the coupling technique. A feedback linearization controller is used to show the difference between unidirectional and bidirectional coupling. We observe that the adaptive controller converges to the feedback linearization controller in the steady state for the Chua–Lorenz example. Finally we comment on how this type of partial synchronization technique can be applied to modeling systems of coupled nonlinear subsystems. We show how such modeling can be achieved where the dynamics of one system is known only via experimental time series measurements.
CHAOS AND HYPERCHAOS IN SHAPE MEMORY SYSTEMS
Authors: SAVI M. A. , PACHECO P. M. C. L.
Published: July 2002

Shape memory and pseudoelastic effects are thermomechanical phenomena associated with martensitic phase transformations, presented by shape memory alloys. The dynamical analysis of intelligent systems that use shape memory actuators involves a multi-degree of freedom system. This contribution concerns with the chaotic response of shape memory systems. Two different systems are considered: a single and a two-degree of freedom oscillator. Equations of motion are formulated assuming a polynomial constitutive model to describe the restitution force of oscillators. Since equations of motion of the two-degree of freedom oscillator are associated with a five-dimensional system, the analysis is performed considering two oscillators, both with single-degree of freedom, connected by a spring-dashpot system. With this assumption, it is possible to analyze the transmissibility of motion between two oscillators. Results show some relation between the transmissibility of order, chaos and hyperchaos with temperature.
AN ITERATION METHOD FOR CHAOTIFYING AND CONTROLLING DYNAMICAL SYSTEMS
Authors: CHEN MAOYIN , HAN ZHENGZHI
Published: July 2002

This paper proposes a new iteration method for chaotifying and controlling dynamical systems. By applying this iteration method, the dimension of the given dynamical system can be reduced from to n to n-1. Moreover, the chaotified system is not necessarily Hurwitz stable originally. The iteration method is applied to three-dimensional systems for demonstration, for which a sufficient condition is obtained for chaotification. In addition, the iteration method can be used to control a class of chaotic systems. These results are illustrated via simulations on the Duffing oscillator and the Chen system.
THE FORCED CHAOTIC AND IRREGULAR OSCILLATIONS OF THE NONLINEAR TWO DEGREES OF FREEDOM (2DOF) SYSTEM
Authors: PŮST LADISLAV , SZÖLLÖS ONDŘEJ
Published: July 2002

The behavior of a 2DOF nonlinear mechanical system excited by a pure harmonic force is studied by the first approximation (averaging and asymptotic) method and by numerical simulations.

The response curves, instability domains, displacement versus time dependencies and phase plane portraits are determined. By means of the first approximation solution we find three instability domains, where jumps occur, or in which the beats, irregular and chaotic motions emerge.

The numerical simulations confirm these properties, but show that there exist several new bifurcations and instability domains, in which the response on the pure harmonic excitation is chaotic. The response curve of the low damped system has in the first resonance the multifold solution. The corresponding oscillations depend on the history, i.e. on the way and the speed of the very slow exciting frequency variation, at which the system comes into the current state. The responses at increasing or decreasing frequencies differ, the hysteresis loops exist.
PREDICTING FAULT-PRONE MODULES IN EMBEDDED SYSTEMS USING ANALOGY-BASED CLASSIFICATION MODELS
Authors: KHOSHGOFTAAR TAGHI M. , CUKIC BOJAN , SELIYA NAEEM
Published: July 2002

Embedded systems have become ubiquitous and essential entities in our ever growing high-tech world. The backbone of today's information-highway infrastructure are embedded systems such as telecommunication systems. They demand high reliability, so as to prevent severe consequences of failures including costly repairs at remote sites. Technology changes mandate that embedded systems evolve, resulting in a demand for techniques for improving reliability of their future system releases. Reliability models based on software metrics can be effective tools for software engineering of embedded systems, because quality improvements are so resource-consuming that it is not feasible to apply them to all modules. Identification of the likely fault-prone modules before system testing, can be effective in reducing the likelihood of faults discovered during operations.

A software quality classification model is calibrated using software metrics from a past release, and is then applied to modules currently under development to estimate which modules are likely to be fault-prone. This paper presents and demonstrates an effective case-based reasoning approach for calibrating such classification models. It is attractive for software engineering of embedded systems, because it can be used to develop software reliability models using a faster, cheaper, and easier method. We illustrate our approach with two large-scale case studies obtained from embedded systems. They involve data collected from telecommunication systems including wireless systems. It is indicated that the level of classification accuracy observed in both case studies would be beneficial in achieving high software reliability of subsequent releases of the embedded systems.
A MATHEMATICAL JUSTIFICATION OF THE LOW-FREQUENCY HETEROGENEOUS TIME-HARMONIC MAXWELL EQUATIONS
Authors: ALONSO ANA
Published: July 2002

This paper deals with the low-frequency model for the time-harmonic Maxwell equations in a heterogeneous medium which behaves like a conductor in one part and a perfect insulator in the other. The model is justified comparing the solution with the one given by the high-frequency heterogeneous model. A bound for the norm of the difference in terms of the frequency is given. It is also proven that the solution of the heterogeneous problem is the limit of the solutions of problems in a conductor with conductivity that tends to zero in a part of the medium.
COGNITIVE MODELING OF SPATIAL REFERENCE FOR HUMAN-ROBOT INTERACTION
Authors: MORATZ REINHARD , FISCHER KERSTIN , TENBRINK THORA
Published: July 2002

The question addressed in this paper is which types of spatial reference human users employ in the interaction with a robot and how a cognitively adequate model of these strategies can be implemented. In experiments we explored how human users approach an artificial communication partner, which was designed to mimic spatial reference among humans. Our findings show that spatial reference in human-robot interaction differs from natural situations in human-human interaction in seveal respects. For instance, many users unexpectedly employed fine-grained, path-based, instructions rather than specifying the intended goal object of the action directly. If instructions were not successful, participants created less and less complex descriptions. Those users who did specify the goal object were found to employ those kinds of spatial reference strategies implemented in our computational model. In particular, they exploited the presence of several similar objects by perceiving and referring to them linguistically as a group.
FROM PLANAR GRAPHS TO EMBEDDED GRAPHS - A NEW APPROACH TO KAUFFMAN AND VOGEL'S POLYNOMIAL
Authors: CARPENTIER RUI PEDRO
Published: July 2002

In [4] Kauffman and Vogel constructed a rigid vertex regular isotopy invariant for unoriented four-valent graphs embedded in three dimensional space. It assigns to each embedded graph G a polynomial, denoted [G], in three variables, A, B and a, satisfying the skein relations: [Formula: see text] and is defined in terms of a state-sum and the Dubrovnik polynomial for links. Using the graphical calculus of [4] it is shown that the polynomial of a planar graph can be calculated recursively from that of planar graphs with less vertices, which also allows the polynomial of an embedded graph to be calculated without resorting to links. The same approach is used to give a direct proof of uniqueness of the (normalized) polynomial restricted to planar graphs. In the case B=A-1 and a=A, it is proved that for a planar graph G we have [G]=2c-1(-A-A-1)v, where c is the number of connected components of G and v is the number of vertices of G. As a corollary, a necessary, but not sufficient, condition is obtained for an embedded graph to be ambient isotopic to a planar graph. In an appendix it is shown that, given a polynomial for planar graphs satisfying the graphical calculus, and imposing the first skein relation above, the polynomial extends to a rigid vertex regular isotopy invariant for embedded graphs, satisfying the remaining skein relations. Thus, when existence of the planar polynomial is guaranteed, this provides a direct way, not depending on results for the Dubrovnik polynomial, to show consistency of the polynomial for embedded graphs.
ON HOMOLOGY OF VIRTUAL BRAIDS AND BURAU REPRESENTATION
Authors: VERSHININ VLADIMIR V.
Published: July 2002

Virtual knots arise in the study of Gauss diagrams and Vassiliev invariants of usual knots. The group of virtual braids on n strings VBn and its Burau representation to GLnℤ[t,t-1] also can be considered. The homological properties of the series of groups VBn and its Burau representation are studied. The following splitting of infinite loop spaces is proved for the plus-construction of the classifying space of the virtual braid group on the infinite number of strings: [Formula: see text] where Y is an infinite loop space. Connections with K*ℤ are discussed.
QUINTESSENCE VERSUS DUALITY
Authors: DE RITIS R. , MARINO A. A. , RUBANO C. , SCUDELLARO P.
Published: July 2002

We compare some features of quintessence cosmological scenarios with the duality symmetry existing in string dilaton cosmologies. Actually, we consider the tracker potential type V = V0/φα and show that duality is only established if α = -2.
PROBING QUANTUM GENERAL RELATIVITY THROUGH EXACTLY SOLUBLE MIDI-SUPERSPACES II: POLARIZED GOWDY MODELS
Authors: PIERRI M.
Published: July 2002

Canonical quantization of the polarized Gowdy midi-superspace with a 3-torus spatial topology is carried out. As in an earlier work on the Einstein–Rosen cylindrical waves, symmetry reduction is used to cast the original problem in four-dimensional spacetimes to a three-dimensional setting. To our knowledge, this is the first complete, systematic treatment of the Gowdy model in the geometrodynamical setting.
CODON DISTRIBUTIONS IN DNA SEQUENCE OF ESCHERICHIA COLI
Authors: NYEO SU-LONG , YANG I-CHING
Published: July 2002

The distributions of codons in the DNA sequence of Escherichia coli K-12 are studied by using several statistical methods of analysis. Codons corresponding to the amino acids leucine, alanine and isoleucine are considered. The pair distributions of the codons as a function of the pair separation are evaluated and are seen to decay exponentially. The exponential decay constants have a linear relation with the numbers of the codons, indicating that the codons are randomly distributed in the sequence. The pair correlation and power spectral methods also show similar statistical behavior of codons in the sequence, with the exception that there appear very small peaks about the frequency f=0.286 in the power spectra of the amino acids leucine, alanine and isoleucine. Such a frequency reflects a periodicity of about 3.5 amino acids and a general helical structure of the proteins of the bacterium.
AN ANALYSIS OF U.S. STOCK PRICE BEHAVIOR USING WAVELETS
Authors: RAMSEY JAMES B. , USIKOV DANIEL , ZASLAVSKY GEORGE M.
Published: July 2002

Using wavelets we re-examine the U.S. stock market price index for any evidence of self-similarity or order that might be revealed at different scales. The wavelet transform localized in time can be used to indicate how the power of the projection of the signal onto the kernel varies with the scale of observation. By comparing how the local power scales vary over time much information about the structure of the data can be obtained. Such evidence is not at all evident from standard analyses of untransformed data, including projections onto a Fourier basis. Wavelets can detect structures in data that are highly localized in time and therefore non-detectable by Fourier transforms.

The main conclusion is that while the data are clearly complex, there seems to be some evidence of non-randomness in the data. There is also some limited evidence of quasi-periodicity in the occurrence of large amplitude shocks to the system.
HISTOPATHOLOGICAL ANALYSIS OF LERI-WEILL DYSCHONDROSTEOSIS: DISORDERED GROWTH PLATE
Authors: Munns C. F. J. , Glass I. A. , LaBrom R. , Hayes M. , Flanagan S. , Berry M. , Hyland V. J. , Batch J. A. , Philips G. E. , Vickers D.
Published: July 2002

Leri-Weill syndrome (LWS) is a dominant (pseudoautosomal) skeletal dysplasia with mesomelic short stature and bilateral Madelung deformity, due to dyschondrosteosis of the distal radius. It results from the loss of one copy of the Short Stature Homeobox Gene (SHOX) from the tip of the short arm of the X or Y chromosome. SHOX molecular testing enabled us to evaluate the histopathology of the radial physis in LWS patients with a documented SHOX abnormality. A widespread disorganisation of physeal anatomy was revealed with disruption of the normal parallel columnar arrangement of chondrocytes. Tandem stacking of maturing chondrocytes within columns was replaced by a side-by-side arrangement. The presence of hypertrophic osteoid with micro-enchondromata in the radial metaphysis suggests abnormal endochondral ossification. The Vickers' ligament was confirmed to blend with the triangular fibrocartilage complex (TFCC). This histopathological study demonstrates that the zone of dyschondrosteosis in LWS is characterised by marked disruption of normal physeal chondrocyte processes and that a generalised physeal abnormality is present.
AN ACCURATE VALUATION OF ASIAN OPTIONS USING MOMENTS
Authors: FUSAI G. , TAGLIANI A.
Published: July 2002

We propose a new method for evaluating fixed strike Asian options using moments. In particular we show that the density of the logarithm of the arithmetic average is uniquely determined from its moments. Resorting to the maximum entropy density, we show that the first four moments are sufficient to recover with great accuracy the true density of the average. Then the Asian option price is estimated with high accuracy. We compare the proposed method with others based on the computation of moments.
Price Limits, Price Expectations, and Price Movements: Empirical Findings from Spectrum Analysis
Authors: Yen Gili , Yen Eva C.
Published: July 2002

The present study applies spectrum analysis to examine the impact of price limits on stock price movements. Based on spectrum analysis, the authors find that the imposition of price limits does alter the pattern of stock price movements in Taiwan. Yet, its efficacy erodes over time.
ISO Certification and Abnormal Return of Stock Price — The Study of the Taiwan Stock Market
Authors: Chen Jo-Hui
Published: July 2002

This paper extends ISO certification research by investigating whether a stock value is influenced by the announcement of its ISO registration with respect to the firm size, industry, and ISO standard series on the Taiwan Stock Exchange. The results show that receiving ISO registration influences abnormal returns. The market reacts favorably to both small and large firms but has no reaction to medium firms in terms of a firm's capital. We also observe significant positive market reaction for Plastics and Textiles. A beneficial implication is that investors may benefit more from their investment endeavors if they can properly examine the specific effects.
SEA MUST LEARN HOW POLICY MAKING WORKS
Authors: NITZ TRACEY , BROWN A. L.
Published: July 2002

The concept of strategic environmental assessment (SEA) has developed rapidly in recent years and has been extensively promoted by environmental assessment (EA) practitioners. SEA has been the focus of considerable dialogue, increasing regulatory attention and emerging evidence of application. This paper seeks to advance the potential for the adoption of SEA in policy making by focusing attention on policy making processes themselves, and on the need for SEA procedures to be moulded to these existing policy making activities. We argue that widespread adoption of SEA concepts is unlikely unless EA practitioners become much more cognisant of the policy making process. Too much of the literature on SEA to date is insular — EA practitioners communicating amongst themselves. Dialogue on SEA development must be between EA proponents and policy makers/theorists if SEA of policy is to fulfil its promise. In order to make SEA of policies effective, SEA must influence the decisions that are intrinsic in policy making. We provide a simplified policy making model and demonstrate that it is necessary, and possible, for SEA to provide environmental input throughout the stages of policy formulation and decision making. The policy making context must drive the form and process of the SEA. In effect, this is an extension of Brown & Hill's (1995) notion of decision scoping, originally developed to increase the efficiency and effectiveness of project-based EIA, to the environmental assessment of policies.
Surfaces from contours
Authors: Meyers David , Skinner Shelley , Sloan Kenneth
Published: July 2002

This paper is concerned with the problem of reconstructing the surfaces of three-dimensional objects, given a collection of planar contours representing cross-sections through the objects. This problem has important aplications in biomedical research and instruction, solid modeling, and industrial inspection.

The method we describe produces a triangulated mesh from the data points of the contours which is then used in conjunction with a piecewise parametric surface-fitting algorithm to produce a reconstructed surface.

The problem can be broken into four subproblems: the
correspondence problem
(which contours should be connected by the surface?), the
tiling problem
(how should the contours be connected?), the
branching problem
(what do we do when there are branches in the surface?), and the
surface-fitting problem
(what is the precise geometry of the reconstructed surface?) We describe our system for surface reconstruction from sets of contours with respect to each of these subproblems. Special attention is given to the correspondence and branching problems. We present a method that can handle sets of contours in which adjacent contours share a very contorted boundary, and we describe a new approach to solving the correspondence problem using a Minimum Spanning Tree generated from the contours.
Techniques for automatically correcting words in text
Authors: Kukich Karen
Published: July 2002

Research aimed at correcting words in text has focused on three progressively more difficult problems:(1) nonword error detection; (2) isolated-word error correction; and (3) context-dependent work correction. In response to the first problem, efficient pattern-matching and
n
-gram analysis techniques have been developed for detecting strings that do not appear in a given word list. In response to the second problem, a variety of general and application-specific spelling correction techniques have been developed. Some of them were based on detailed studies of spelling error patterns. In response to the third problem, a few experiments using natural-language-processing tools or statistical-language models have been carried out. This article surveys documented findings on spelling error patterns, provides descriptions of various nonword detection and isolated-word error correction techniques, reviews the state of the art of context-dependent word correction techniques, and discusses research issues related to all three areas of automatic error correction in text.
Recontamination does not help to search a graph
Authors: LaPaugh Andrea S.
Published: July 2002

This paper is concerned with a game on graphs called
graph searching
. The object of this game is to clear all edges of a contaminated graph. Clearing is achieved by moving searchers, a kind of token, along the edges of the graph according to clearing rules. Certain search strategies cause edges that have been cleared to become contaminated again. Megiddo et al. [9] conjectured that every graph can be searched using a minimum number of searchers without this recontamination occurring, that is, without clearing any edge twice. In this paper, this conjecture is proved. This places the graph-searching problem in NP, completing the proof by Megiddo et al. that the graph-searching problem is NP-complete. Furthermore, by eliminating the need to consider recontamination, this result simplifies the analysis of searcher requirements with respect to other properties of graphs.
Generalized algorithmic debugging and testing
Authors: Fritzson Peter , Shahmehri Nahid , Kamkar Mariam , Gyimothy Tibor
Published: July 2002

This paper presents a method for semi-automatic bug localization, generalized algorithmic debugging, which has been integrated with the category partition method for functional testing. In this way the efficiency of the algorithmic debugging method for bug localization can be improved by using test specifications and test results. The long-range goal of this work is a semi-automatic debugging and testing system which can be used during large-scale program development of nontrivial programs.

The method is generally applicable to procedural langua ges and is not dependent on any ad hoc assumptions regarding the subject program. The original form of algorithmic debugging, introduced by Shapiro, was however limited to small Prolog programs without side-effects, but has later been generalized to concurrent logic programming languages. Another drawback of the original method is the large number of interactions with the user during bug localization.

To our knowledge, this is the first method which uses category partition testing to improve the bug localization properties of algorithmic debugging. The method can avoid irrelevant questions to the programmer by categorizing input parameters and then match these against test cases in the test database. Additionally, we use program slicing, a data flow analysis technique, to dynamically compute which parts of the program are relevant for the search, thus further improving bug localization.

We believe that this is the first generalization of algorithmic debugging for programs with side-effects written in imperative languages such as Pascal. These improvements together makes it more feasible to debug larger programs. However, additional improvements are needed to make it handle pointer-related side-effects and concurrent Pascal programs.

A prototype generalized algorithmic debugger for a Pascal subset without pointer side-effects and a test case generator for application programs in Pascal, C, dBase, and LOTUS have been implemented.
Diversity-based inference of finite automata
Authors: Rivest Ronald L. , Schapire Robert E.
Published: July 2002

We present new procedures for inferring the structure of a finite-state automaton (FSA) from its input/output behavior, using access to the automaton to perform experiments.

Our procedures use a new representation for finite automata, based on the notion of equivalence betweentests. We call the number of such equivalence classes thediversityof the automaton; the diversity may be as small as the logarithm of the number of states of the automaton. For the special class ofpermutation automata, we describe an inference procedure that runs in time polynomial in the diversity and log(1/δ), where δ is a given upper bound on the probability that our procedure returns an incorrect result. (Since our procedure uses randomization to perform experiments, there is a certain controllable chance that it will return an erroneous result.) We also discuss techniques for handling more general automata.

We present evidence for the practical efficiency of our approach. For example, our procedure is able to infer the structure of an automaton based on Rubik's Cube (which has approximately 1019states) in about 2 minutes on a DEC MicroVax. This automaton is many orders of magnitude larger than possible with previous techniques, which would require time proportional at least to the number of global states. (Note that in this example, only a small fraction (10-14) of the global states were even visited.)

Finally, we present a new procedure for inferring automata of a special type in which the global state is composed of a vector of binary local state variables, all of which are observable (orvisible) to the experimenter. Our inference procedure runs provably in time polynomial in the size of this vector (which happens to be the diversity of the automaton), even though the global state space may be exponentially larger. The procedure plans and executes experiments on the unknown automaton; we show that the number of input symbols given to the automaton during this process is (to within a constant factor) the best possible.
Fully persistent lists with catenation
Authors: Driscoll James R. , Sleator Daniel D. K. , Tarjan Robert E.
Published: July 2002

This paper considers the problem of representing stacks with catenation so that any stack, old or new, is available for access or update operations. This problem arises in the implementation of list-based and functional programming languages. A solution is proposed requiring constant time and space for each stack operation except catenation, which requires O(log logk) time and space. Herekis the number of stack operations done before the catenation. All the resource bounds are amortized over the sequence of operations.
Technological frames
Authors: Orlikowski Wanda J. , Gash Debra C.
Published: July 2002

In this article, we build on and extend research into the cognitions and values of users and designers by proposing a systematic approach for examining the underlying assumptions, expectations, and knowledge that people have about technology. Such interpretations of technology (which we call technological frames) are central to understanding technological development, use, and change in organizations. We suggest that where the technological frames of key groups in organizations—such as managers, technologists, and users— are significantly different, difficulties and conflict around the development, use, and change of technology may result. We use the findings of an empirical study to illustrate how the nature, value, and use of a groupware technology were interpreted by various organizational stakeholders, resulting in outcomes that deviated from those expected. We argue that technological frames offer an interesting and useful analytic perspective for explaining an anticipating actions and meanings that are not easily obtained with other theoretical lenses.
An improved incomplete Cholesky factorization
Authors: Jones Mark T. , Plassmann Paul E.
Published: July 2002

Incomplete factorization has been shown to be a good preconditioner for the conjugate gradient method on a wide variety of problems. It is well known that allowing some fill-in during the incomplete factorization can significantly reduce the number of iterations needed for convergence. Allowing fill-in, however, increases the time for the factorization and for the triangular system solutions. Additionally, it is difficult to predict a priori how much fill-in to allow and how to allow it. The unpredictability of the required storage/work and the unknown benefits of the additional fill-in make such strategies impractical to use in many situations. In this article we motivate, and then present, two “black-box” strategies that significantly increase the effectiveness of incomplete Cholesky factorization as a preconditioner. These strategies require no parameters from the user and do not increase the cost of the triangular system solutions. Efficient implementations for these algorithms are described. These algorithms are shown to be successful for a variety of problems from the Harwell-Boeing sparse matrix collection.
Bayesian networks
Authors: Heckerman David , Wellman Michael P.
Published: July 2002

This brief tutorial on Bayesian networks serves to introduce readers to some of the concepts, terminology, and notation employed by articles in this special section. In a Bayesian network, a variable takes on values from a collection of mutually exclusive and collective exhaustive states. A variable may be discrete, having a finite or countable number of states, or it may be continuous. Often the choice of states itself presents an interesting modeling question. For example, in a system for troubleshooting a problem with printing, we may choose to model the variable “print output” with two states—“present” and “absent”—or we may want to model the variable with finer distinctions such as “absent,” “blurred ,” “cut off,” and “ok.”
Functionality and usability
Authors: Goodwin Nancy C.
Published: July 2002

Instead of limiting functionality, usability complements functionality. It affects how and with what effectiveness a system is used, and even whether or not it is used at all.
Applications of inductive logic programming
Authors: Bratko Ivan , Muggleton Stephen
Published: July 2002

Techniques of machine learning have been successfully applied to various problems [1, 12]. Most of these applications rely on attribute-based learning, exemplified by the induction of decision trees as in the program C4.5 [20]. Broadly speaking, attribute-based learning also includes such approaches to learning as neural networks and nearest neighbor techniques. The advantages of attribute-based learning are: relative simplicity, efficiency, and existence of effective techniques for handling noisy data. However, attribute-based learning is limited to non-relational descriptions of objects in the sense that the learned descriptions donotspecifyrelationsamong the objects' parts. Attribute-based learning thus has two strong limitations:

the background knowledge can be expressed in rather limited form, and

the lack of relations makes the concept description language inappropriate for some domains.
Smooth B-spline illumination maps for bidirectional ray tracing
Authors: Redner Richard A. , Lee Mark E. , Uselton Samuel P.
Published: July 2002

In this paper we introduce B-spline illumination maps and their generalizations and extensions for use in realistic image generation algorithms. The B-spline lighting functions (i.e., illumination maps) are defined as weighted probability density functions. The lighting functions can be estimated from random data and may be used in bidirectional distributed ray tracing programs as well as radiosity oriented algorithms. The use of these lighting functions in a bidirectional ray tracing system that can handle dispersion as well as the focusing of light through lenses is presented.
Unreliable failure detectors for reliable distributed systems
Authors: Chandra Tushar Deepak , Toueg Sam
Published: July 2002

We introduce the concept of unreliable failure detectors and study how they can be used to solve Consensus in asynchronous systems with crash failures. We characterise unreliable failure detectors in terms of two properties—completeness and accuracy. We show that Consensus can be solved even with unreliable failure detectors that make an infinite number of mistakes, and determine which ones can be used to solve Consensus despite any number of crashes, and which ones require a majority of correct processes. We prove that Consensus and Atomic Broadcast are reducible to each other in asynchronous systems with crash failures; thus, the above results also apply to Atomic Broadcast. A companion paper shows that one of the failure detectors introduced here is the weakest failure detector for solving Consensus [Chandra et al. 1992].
A mathematically focused curriculum for computer science
Authors: Berztiss Alfs
Published: July 2002

A curriculum that is flexible enough to suit all students studying computer science, and that reintegrates the theoretical aspects of the field along with more practical or vocational aspects, is proposed.
An empirical validation of software cost estimation models
Authors: Kemerer Chris F
Published: July 2002

Practitioners have expressed concern over their inability to accurately estimate costs associated with software development. This concern has become even more pressing as costs associated with development continue to increase. As a result, considerable research attention is now directed at gaining a better understanding of the software-development process as well as constructing and evaluating software cost estimating tools. This paper evaluates four of the most popular algorithmic models used to estimate software costs (SLIM, COCOMO,
Function Points, and
ESTIMACS). Data on 15 large completed business data-processing projects were collected and used to test the accuracy of the models' ex post effort estimation. One important result was that Albrecht's Function Points effort estimation model was validated by the independent data provided in this study [3]. The models not developed in business data-processing environments showed significant need for calibration. As models of the software-development process, all of the models tested failed to sufficiently reflect the underlying factors affecting productivity. Further research will be required to develop understanding in this area.
Extending object-oriented systems with roles
Authors: Gottlob Georg , Schrefl Michael , Röck Brigitte
Published: July 2002

In many class-based object-oriented systems the association between as instance and a class is exclusive and permanent. Therefore these systems have serious difficulties in representing objects taking on different roles over time. Such objects must be reclassified any time they evolve (e.g., if a person becomes a student and later an employee). Class hierarchies must be planned carefully and may grow exponentially if entities may take on serveral independent roles. The problem is even more servere for object-oriented databases than for common object-oriented programming. Databases store objects over longer periods, during which the represented entities evolve. This article shows how class-based object-oriented systems can be extended to handle evolving objects well. Class hierarchies are complemented by role hierarchies, whose nodes represent role types an object classified in the root may take on. At any point in time, an entity is represented by an instance of the root and an instance of every role type whose role it currently plays. In a natural way, the approach extends traditional object-oriented concepts, such as classification, object identity, specialization, inheritance, and polymorphism in a natural way. The practicability of the approach is demonstrated by an implementation in Smalltalk. Smalltalk was chosen because it is widely known, which is not true for any particular class-based object-oriented database programming language. Roles can be provided in Smalltalk by adding a few classes. There is no need to modify the semantics of Smalltalk itself. Role hierarchies are mapped transparently onto ordinary classes. The presented implementation can easily be ported to object-oriented database programming languages based on Smalltalk, such as Gemstone's OPAL hierarchies are complemented by role hierarchies, whose nodes represent role types an object classified in the root may take on. At any point in time, an entity is represented by an instance of the root and an instance of every role type whose role in currently plays.