bluuebunny/crossref_metadata_2025 huggingface dataset:
ER Suspensions with ER Active Matrix Liquids
Authors: Quist G. P. , Filisko Frank. E.
Published: July 2002

Solutions of polyhexyl isocyanate in xylene, a well known lyotropic liquid crystalline system, are shown to be ER active at concentrations well below those for the onset of a mesophase. This correlates with a field dependent birefringence or orientation induced in the isotropic phase. ER fluids made using these solutions as the liquid phase show an ER activity much greater than just the sum of ER properties of the solutions and the particles in inert fluids, i.e., the effects are synergistic. A greatly enhanced birefringence between the particles is observed under electric field. The effects are explained as due to both a much greater orientation of and increased concentration of polymer between the particles. These effects are not observed for solutions of polystyrene.
The Role of Interfacial Polarization in the Electrorheological Effects
Authors: Hao Tian , Kawai Akiko , Ikazaki Fumikazu
Published: July 2002

The conductive, dielectric and surface properties of severl water-free polymer or inorganic material based ER fluids, as well as their response times, are investigated to elucidate the physical ground of the electrorheological effect. It is found that the slow polarization, especially the interfacial polarization rather than the Debye polarization, should be responsible for the observed phenomena. Combining with the recent achievements (both theoretical and experimental) in the electrorheological field, we argue that is the interfacial polarization that does play a central role in electrorheological response. The particle re-orientation process is actually resulted from the large interfacial polarization.
Microgravity Experiment and Linear and Nonlinear Analyses of the Dissipative Structure of Thermomagnetic Convection
Authors: Morimoto Hisao , Kobayashi Takayuki , Maekawa Toru
Published: July 2002

We investigated the dissipative structure of thermomagnetic convection by microgravity experiments and linear and nonlinear numerical simulations. We carried out microgravity experiments of thermomagnetic convection using a dropshaft facility and investigated the effect of the aspect ratio of the magnetic fluid layer on the pattern formations. We also analysed the onset of convection by the linear stability theory. The nonlinear governing equations are introduced and linearised. The critical magnetic Rayleigh number and the critical wave number are obtained solving the eigenvalue equations by harmonic analysis and the finite difference method. The number of rolls obtained by the linear stability theory agreed with that obtained by the microgravity experiments. Furthermore, we carried out nonlinear analysis of pattern formations induced by thermomagnetic convection. The nonlinear equations were solved by the control volume finite difference method. The flow patterns obtained by the nonlinear calculation coincided with those obtained by the microgravity experiments. The relation between the initial wave numbers of perturbations and the final patterns is investigated and a bifurcation diagram is produced. The critical magnetic Rayleigh number obtained by the nonlinear analysis agreed with that obtained by the linear stability analysis and the bifurcations from one pattern to another are clearly demonstrated as a problem of probability.
POLARON AND SPIN-POLARON EFFECTS IN THE COLOSSAL MAGNETORESISTANCE
Authors: MALOZOVSKY Y. M. , FAN J. D.
Published: July 2002

The polaron formation due to the strong interaction of electrons with the optical phonons in a layered manganese oxides is considered. The diffusion of nearly localized polarons in the presence of the spin-dependent and multiple scattering on the randomly oriented and/or distributed magnetic moments of atoms is considered. The spin diffusion coefficient in the case of the exchange interaction between the diffusive but nearly localized polarons is evaluated. It is shown that the polaron localization leads to the vanishing of the spin diffusion and hence the ferromagnetic phase transition. The spin-polaron effect caused by the interaction of polarons with the spin fluctuations further significantly reduces conductivity near the temperature of the ferromagnetic phase transition as shown.
POLY-SILICON THIN FILMS PREPARED BY LOW TEMPERATURE ALUMINUM-INDUCED CRYSTALLIZATION
Authors: MATSUMOTO YASUHIRO , TAMURA MASAO , ASOMOZA RENE , YU ZHENRUI
Published: July 2002

P-type poly-Si thin films prepared by low temperature Aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thicknessess were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550°C. XRD, SIMS, TEM and Hall effect measurements were carried out to characterize the annealed films. Results show that a-Si:H contacted with adequate Al could be crystallized at temperature as low as 300°C after annealing for 60 minutes. This material has high carrier concentration as well as high Hall mobility can be used as a p-layer or seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process.
ELECTRON SHELVING INDUCED SQUEEZING IN FLUORESCENT LIGHT EMITTED BY COLD 4He ATOMS IN AN OPTICAL LATTICE: COHERENT CONTROL BY A WEAK AXIAL MAGNETIC FIELD
Authors: BHATTACHERJEE ARANYABHUTI
Published: July 2002

We report theoretical calculations on the effect of polarization gradient, atomic motion and an axial magnetic field on quantum noise reduction in the resonant fluorescence emitted by a cloud of cold Helium atoms in an optical lattice. The polarization gradient induces squeezing of the electromagnetic field at selected points on the optical lattice, together with a dark resonance in the emitted fluorescence, the origin of which is traced back to electron shelving. We find that the localization of the atoms in the optical lattice destroys squeezing, but can be recovered in the presence of an axial magnetic field.
PENETRATION DEPTH CALCULATION IN THE FRAMEWORK OF THE TWO-BANDS ELIASHBERG MODEL IN MgB2
Authors: MOCA CĂTĂLIN PAŞCU
Published: July 2002

We investigate the temperature dependence of the penetration depth λ(T) in MgB2 in the framework of the two-bands model using the Eliashberg formalism. We also study the influence of the impurities lifetime on the temperature dependence of λ(T). By direct comparison of the experimental data with theoretical results, a practical method to determine the orientation of the crystal is proposed.
A POSSIBLE CLASS OF TWO-MODE PHOTON STATES AND THEIR PROPERTIES
Authors: YU ZURONG
Published: July 2002

In this paper, a new class of two-mode optical field states is given. The quasi-spin coherent state is their lowest state. Their non-classical properties are discussed in detail.
ANNEALING EFFECT ON COERCIVITY AND MICROHARDNESS IN SINTERED (Nd, Tb)15(Fe, Co, Al)78B7 MAGNETS
Authors: LUKIN A. A. , SZYMURA S. , ZHURAVLYEV A. A. , MARGARYAN M. C. , NOWY-WIECHUŁA W.
Published: July 2002

The variation of the coercivity and microhardness with annealing (475–1150°C/3.6 ks) of sintered (Nd, Tb) 15 (Fe, Co, Al) 78 B 7 permanent magnet have been investigated. The data indicate that the coercivity reaches the mininum and the maximum at 600°C and 775°C, respectively. Optical and scanning electron microscopy and magnetic domain structure observations give no hints to any change in microstructure. Fitting of the Mössbauer spectra of permanent magnets for different coercivity ( i H c ) values revealed that magnetic hyperfine fields (B Hf ) on all Fe sites are reduced with the increase in i H c value and the higher value of the i H c corresponds to the higher value of the Mössbauer line width. The microhardness changes in the matrix Nd 2 Fe 14 B phase have been correlated with changes in the coercivity.
FAST AND SIMPLE DISCRETE APPROACH FOR ACTIVE CONTOURS FOR BIOMEDICAL APPLICATIONS
Authors: ELMOATAZ ABDERRAHIM , SCHÜPP SOPHIE , BLOYET DANIEL
Published: July 2002

In this paper, we present a fast and simple discrete approach for active contours. It is based on discrete contour evolution, which operates on the boundary of digital shape, by iterative growth processes on the boundary of the shape. We consider a curve to be the boundary of a discrete shape. We attach at each point of the boundary a cost function and deform this shape according to that cost function. The method presents some advantages. It is a discrete method, which takes an implicit representation and uses discrete algorithm with a simple data structure.
LANGUAGE AND COHERENT NEURAL AMPLIFICATION IN HIERARCHICAL SYSTEMS: RENORMALIZATION AND THE DUAL INFORMATION SOURCE OF A GENERALIZED SPATIOTEMPORAL STOCHASTIC RESONANCE
Authors: WALLACE RODRICK
Published: July 2002

A growing body of work suggests an important unifying perspective in the study of stochastic resonance: Examining the "prehistory probability density" of the ensemble of pathways by which a system approaches the trigger of the nonlinear oscillator. This view, in the context of the Shannon–McMillan Theorem of information theory, leads to a draconian simplification of the complex of "signal," "noise" and oscillator in terms of a single object, an ergodic information source dual to a certain class of resonances.

For "spatial" stochastic resonator arrays, in the most general sense, the Shannon–McMillan Theorem further provides an analogy between the Shannon uncertainty of the dual information source and the free energy density of a physical system which allows imposition of real-space renormalization to give essential results in a straightforward manner. We find in particular threshold behavior in the onset of an epileptiform spatiotemporal coherence, and a likely usefulness of tuned spatial arrays for the detection of very subtle pattern.

These simplifications may provide, in addition, a natural context for discussing hierarchical structure in neural systems.

In sum, we attempt to bring stochastic resonance into the contemporary framework of applied mathematics which has begun to unify the study of fluctuations, statistical mechanics and information theory. Our critical generalization lies in the transfer of renormalization methods from statistical mechanics to information theory, via a parametization of source uncertainty.
PHASE RESETTING, CLUSTERS, AND WAVES IN A LATTICE OF COUPLED OSCILLATORY UNITS
Authors: MAKAROV V. A. , NEKORKIN V. I. , VELARDE M. G.
Published: July 2002

A one-dimensional chain consisting of many locally coupled oscillatory units is considered when both diffusive (linear) and nonlinear interactions exist. The dynamics of units may also be altered by a weak white Gaussian noise. Two different collective evolutionary paths have been identified in the chain: (i) the onset of temporal phase clusters and their subsequent breakdown or reconstruction through phase resetting, and (ii) the formation of a phase wave during a process of selforganization. Such a wave may originate from an initially disordered pattern after appropriate reorganization of phases and amplitudes occurring on a time lapse that can be very long.
A SIMPLE APPROACH TO CALCULATION AND CONTROL OF UNSTABLE PERIODIC ORBITS IN CHAOTIC PIECEWISE-LINEAR SYSTEMS
Authors: UETA TETSUSHI , CHEN GUANRONG , KAWABE TOHRU
Published: July 2002

This paper describes a simple method for calculating unstable periodic orbits (UPOs) and their control in piecewise-linear autonomous systems. The algorithm can be used to obtain any desired UPO embedded in a chaotic attractor, and the UPO can be stabilized by a simple state feedback control. A brief stability analysis of the controlled system is also given.
DYNAMICS OF A LARGE ARRAY OF GLOBALLY COUPLED LASERS WITH DISTRIBUTED FREQUENCIES
Authors: OLIVA RICARDO A. , STROGATZ STEVEN H.
Published: July 2002

We analyze a mean-field model for a large array of coupled solid-state lasers with randomly distributed natural frequencies. Using techniques developed previously for coupled nonlinear oscillators, we derive exact formulas for the stability boundaries of the phase locked, incoherent, and off states, as functions of the coupling and pump strength and the spread of natural frequencies. For parameters in the intermediate regime between total incoherence and perfect phase locking, numerical simulations reveal a variety of unsteady collective states in which all the lasers' intensities vary periodically, quasiperiodically, or chaotically.
BIFURCATION AND CHAOS IN THE SECOND OSCILLATORY WINDOW OF THE CLASSICAL PIERCE DIODE
Authors: BARROSO J. J. , TERRA M. O. , MACAU E. E. N.
Published: July 2002

The second oscillatory window of the classical Pierce diode is explored by a particle-in-cell simulation, and for the first time, results that support the existence of another chaotic region are presented. The classical Pierce model consists of a one-dimensional plasma-filled diode into which a monoenergetic electron beam is injected. This system presents a rich dynamical behavior as a function of a single control parameter α (the electron transit angle) and has four different operating regimes: stable, oscillatory, chaotic and unstable oscillatory with virtual cathode formation. The second oscillatory region, revealed by linear approximation analysis, presents a similar dynamical behavior to the first one, studied by many works and located below α = 3π. By gradually diminishing α from 5π, we report here, through numerical experiments, the existence of a sequence of subharmonic bifurcations leading to chaos, periodic windows, and a crisis from which just unstable oscillations with virtual cathode can be observed.
PHASE CLUSTERS IN 2D ARRAYS OF NONIDENTICAL OSCILLATORS
Authors: LIU ZONGHUA , HU BAMBI
Published: July 2002

We study the collective behavior of a 2D network of nonidentical oscillators in the chaotic regime and find that ordered phase can emerge in the collective behavior, due to mutual coupling. The resulting phase cluster is a frequency-locking. The configuration of pattern depends on time and can be divided into several phase clusters when coupling is over some threshold. The frequency-locked spatiotemporal patterns are determined by the mismatched parameter and the coupling strength, and its regularity can be measured by an average nearest-neighbor distance.
PLANE MAPS WITH DENOMINATOR I: SOME GENERIC PROPERTIES
Authors: BISCHI GIAN-ITALO , GARDINI LAURA , MIRA CHRISTIAN
Published: July 2002

This paper is devoted to the study of some global dynamical properties and bifurcations of two-dimensional maps related to the presence, in the map or in one of its inverses, of a vanishing denominator. The new concepts of focal points and of prefocal curves are introduced in order to characterize some new kinds of contact bifurcations specific to maps with denominator. The occurrence of such bifurcations gives rise to new dynamic phenomena, and new structures of basin boundaries and invariant sets, whose presence can only be observed if a map (or some of its inverses) has a vanishing denominator.
EMERGENCE OF UNICELLULAR ORGANISMS FROM A SIMPLE GENERALIZED CELLULAR AUTOMATA
Authors: DOGARU RADU , CHUA LEON O.
Published: July 2002

The goal of this letter is to report a novel class of dynamical behaviors observed from a generalized cellular automata CNN [Chua, 1998] with piecewise-linear (PWL) cells. Starting from an almost homogeneous initial condition, self-making (autopoietic in the sense of [Varela et al., 1974]) patterns, reminiscent of simple living systems, emerge as a result of the nonlinear coupling among cells. Similar to patterns of organization characterizing living systems, our patterns display features such as growth, maturity and death. The discovery of such patterns was made possible via mutations in several piecewise-linear CNN cell realizations of the "Game of Life" [Conway, 1982].
FAST NONLINEAR PROJECTIVE FILTERING IN A DATA STREAM
Authors: SCHREIBER THOMAS , RICHTER MARCUS
Published: July 2002

We introduce a modified algorithm to perform nonlinear filtering of a time series by locally linear phase space projections. Unlike previous implementations, the algorithm can be used not only for a posteriori processing but also includes the possibility to perform real-time filtering in a data stream. Apart from making the filter causal by restricting neighbor searches to the past, the data base that represents the phase space structure generated by the data is updated dynamically. This also allows filtering of nonstationary signals and dynamic parameter adjustment. We discuss exemplary applications, including the real-time extraction of the fetal electrocardiogram from abdominal recordings.
DEVELOPMENT OF WIRELESS EMBEDDED SYSTEMS USING COMPONENT BASED SOFTWARE
Authors: YANG STEPHEN J. H. , TSAI JEFFREY J. P. , CHEN IRENE
Published: July 2002

Many mobile and wireless devices are connecting to the Internet nowadays, among them, mobile phones and PDAs are the most popular ones. Thus, in this paper, we will focus on how to develop embedded software running on the two devices by using design patterns and Java based software components. Notably, some components may be used directly in an embedded software system, whereas most components must be specialized prior to reuse. Developers have to identify the variation points on these components. In order to develop a reusable embedded software system, we will identify several variation points with some variants, and introduce some useful design patterns for implementing variation points. Consequently, we can customize an embedded software system just through attaching variants on corresponding variation point in our system.

The design patterns we are using are property container, strategy, decorator, and model-view-controller. The component technology we are using is J2ME. J2ME is a specification focused on the development of mobile applications. It provides a similar environment as standard Java environment. J2ME's components programming includes the Spotlet programming for PDA, and the MIDlet programming for Java phone. In addition, along with the XML, J2ME can also provide the XMIDlet programming for dynamic downloading and execution of XML-based applications for PDA and Java phones.
AN OPTIMAL CONTROL APPROACH TO SEMICONDUCTOR DESIGN
Authors: HINZE MICHAEL , PINNAU RENÉ
Published: July 2002

The design problem for semiconductor devices is studied via an optimal control approach for the standard drift–diffusion model. The solvability of the minimization problem is proved. The first-order optimality system is derived and the existence of Lagrange-multipliers is established. Further, estimates on the sensitivities are given. Numerical results concerning a symmetric n–p-diode are presented.
EXISTENCE AND WEAK STABILITY FOR A PRESSURELESS MODEL WITH UNILATERAL CONSTRAINT
Authors: BERTHELIN F.
Published: July 2002

We consider a two-phase model described by a pressureless gas system with unilateral constraint. We prove weak stability and the existence of weak solutions by passing to the limit in the sticky-blocks dynamics. We obtain the maximum principle on the velocity, the Oleinik entropy condition and local entropy inequalities. Initial data are taken in a very weak sense since the solution can jump initially in time.
EFFECT OF SHORT-RANGE NUCLEAR CORRELATIONS ON THE (γ,p) CROSS SECTIONS FOR 208Pb IN A PARTICLE-HOLE MODEL
Authors: RITZ THORSTEN , SCHEID WERNER
Published: July 2002

One-proton photodissociation cross sections are studied for the reaction 208 Pb (γ,p)207 Tl at photon energies between 20 and 80 MeV. The transition into the 1g7/2 state of 207Tl is calculated in a particle-hole model with short-range correlations and compared with estimated cross sections based on experimental differential cross sections of Bobeldijk (1995). The short-range correlations are described by Jastrow factors. The correlation factors increase the total cross section. This result is in better agreement with experimental data than calculations without short-range correlations.
BIFURCATION ANALYSIS OF CALCIUM OSCILLATIONS: TIME-SCALE SEPARATION, CANARDS, AND FREQUENCY LOWERING
Authors: SCHUSTER STEFAN , MARHL MARKO
Published: July 2002

The behavior of calcium oscillations near bifurcations is analyzed for three different models. For the model developed by Somogyi and Stucki [42], it is shown that the range of oscillations is bounded by supercritical and subcritical Hopf bifurcations. Near the latter, canard orbits arise, that is, quasi-harmonic oscillations with a very small amplitude grow very fast to become pulsed oscillations. The potential biological significance of this behavior is discussed. A time-scale analysis of this model is performed and an approximation formula for the oscillation period is derived. For two models that we presented earlier [30, 31], it is shown that a homoclinic bifurcation and an infinite period bifurcation, respectively, occur. These imply that the oscillation period can reach arbitrarily high values. This behavior is discussed in the light of frequency encoding, and the scaling laws of the oscillation period are given.
BAYESIAN SINGLE-LEVEL BINOMIAL AND EXPONENTIAL RELIABILITY DEMONSTRATION TEST PLANS
Authors: FITZGERALD MARK , MARTZ HARRY F. , PARKER ROBERT L.
Published: July 2002

Bayesian reliability demonstration test plans are developed for binomial and exponential sampling distributions using mixtures of beta and inverse gamma prior distributions, respectively. Both types of plans consider a single specified target reliability and rectify an important drawback of an existing well-known classical single-level test planning procedure. The plans are developed in such a way that they attain a specified probability of passing the test when the target reliability has been met as well as provide desired confidence that the target reliability has been met given that the test has been passed.
ENERGETICS OF BORON IN THE Si(111)- $(\sqrt{3}\times
\sqrt{3})$-B SURFACE PHASE AND IN SUBSURFACE SILICON LAYERS
Authors: ZAVODINSKY V. G. , CHUKUROV E. N. , KUYANOV I. A.
Published: July 2002

The energetics of the boron substitution in the B/Si(111)-[Formula: see text] surface phase and in subsurface silicon layers has been studied using the semiempirical cluster method AM1. It has been found that the boron energy in the second layer (the B-S 5 site) is about 1 eV lower than in the adatom position (the B-T 4 site) and about 2 eV lower than in the fourth bulklike layer. The latter value may be interpreted as the surface segregation energy (enthalpy). The barrier height for the B-T 4– B-S 5 transfer has been found to be about 0.7 eV.
Scapho-Trapezio-Trapezoid Arthrodesis.
Authors: Kaines Andrew , Chissell Hugh , Hayes Michael , Saies Andrew
Published: July 2002

Scapho-trapezio-trapezoid (STT) arthrodesis is a relatively common procedure performed for severe STT arthritis, scapholunate instability and Kienböck's disease. Twenty-eight of 31 patients who had undergone this procedure were reviewed at a mean of 65 months following surgery (range 24 to 97 months). Four patients underwent wrist arthrodesis; two for failed STT fusion; and two for uncontrolled pain related to pre-existing carpal osteoarthritis.

Ninety-two percent of patients who had a successful STT arthrodesis achieved good or excellent pain relief and 79% were satisfied with the results of surgery. Pain relief was best in patients with a pre-operative diagnosis of STT arthritis. Wrist range of motion and strength were well preserved. No patients developed isolated arthrosis in the radiocarpal, intercarpal or adjacent joints.

STT provides excellent pain relief with an acceptable reduction in grip strength and range of motion. However, the benefits of this procedure must be balanced against the potentially serious postoperative complications and the possibility of arthrosis.
EXACT SOLUTION OF A MODEL FOR CROWDING AND INFORMATION TRANSMISSION IN FINANCIAL MARKETS
Authors: D'HULST R. , RODGERS G. J.
Published: July 2002

An exact solution is presented to a model that mimics the crowding effect in financial markets which arises when groups of agents share information. We show that the size distribution of groups of agents has a power law tail with an exponential cut-off. As the size of these groups determines the supply and demand balance, this implies heavy tails in the distribution of price variation. The moments of the distribution are calculated, as well as the kurtosis. We find that the kurtosis is large for all model parameter values and that the model is not self-organizing.
PRICING BARRIER OPTIONS WITH SQUARE ROOT PROCESS
Authors: LO C. F. , YUEN P. H. , HUI C. H.
Published: July 2002

The square root constant elasticity of variance (CEV) process has been paid little attention in previous research on valuation of barrier options. In this paper we derive analytical option pricing formulae of up-and-out options with this process using the eigenfunction expansion technique. We develop an efficient algorithm to compute the eigenvalues where the basis functions in the formulae are the confluent hypergeometric functions. The numerical results obtained from the formulae are compared with the corresponding model prices under the Black–Scholes model. We find that the differences in the model prices between the square root CEV model and the Black–Scholes model can be significant as the time to maturity and volatility increases.
SURFACE GRANULAR FLOWS: TWO RELATED EXAMPLES
Authors: KHAKHAR D. V. , ORPE ASHISH V. , OTTINO J. M.
Published: July 2002

Granular surface flows are common in industrial practice and natural systems, however, theoretical description of such flows is at present incomplete. Two prototype systems involving surface flow are compared: heap formation by pouring at a point and rotating cylinders. Continuum models for analysis of these flows are reviewed, and experimental results for quasi-2D systems are presented. Experimental results in both systems are well described by continuum models.
PRODUCT DEVELOPMENT IN JAPANESE TV GAME SOFTWARE: THE CASE OF AN INNOVATIVE GAME
Authors: BABA YASUNORI , TSCHANG F. TED
Published: July 2002

This paper addresses the issue of developing innovative software with a case study of the emerging prototyping methods used in an innovative game in the Japanese game software industry. Software has traditionally been seen as an efficiency-driven process. But in innovative software, there are other important issues, such as the need to allow for radical redesign in development cycles, and the need to resolve tensions between creative and controlling processes. The paper addresses the broader design issue by documenting the emerging prototyping practices in design-driven and originality-oriented product development. We term this an "outward spiral" software development model, in which the completion of an initial prototyping cycle may lead to significant revisions in design and code, and the possible scrapping of large chunks of code. This model is compared with the development processes used for other types of software and in creative industries like the music industry.
Algorithm 702: TNPACK–a truncated Newton minimization package for large-scale problems
Authors: Schlick Tamar , Fogelson Aaron
Published: July 2002

We present a FORTRAN package of subprograms for minimizing multivariate functions without constraints by a truncated Newton algorithm. The algorithm is especially suited for problems involving a large number of variables. Truncated Newton methods allow approximate, rather than exact, solutions to the Newton equations. Truncation is accomplished in the present version by using the preconditioned Conjugate Gradient algorithm (PCG) to solve approximately the Newton equations. The preconditioner
M
is factored in PCG using a sparse modified Cholesky factorization based on the Yale Sparse Matrix Package. In this paper we briefly describe the method and provide details for program usage.
Termination, deadlock, and divergence
Authors: Aceto L. , Hennessy M.
Published: July 2002

In this paper, a process algebra that incorporates explicit representations of successful termination, deadlock, and divergence is introduced and its semantic theory is analyzed. Both an operational and a denotational semantics for the language is given and it is shown that they agree. The operational theory is based upon a suitable adaptation of the notion of bisimulation preorder. The denotational semantics for the language is given in terms of the initial continuous algebra that satisfies a set of equations
E
,

CI
E

. It is shown that

CI
E

is fully abstract with respect to our choice of behavioral preorder. Several results of independent interest are obtained; namely, the finite approximability of the behavioral preorder and a partial completeness result for the set of equations
E
with respect to the preorder.
HDM—a model-based approach to hypertext application design
Authors: Garzotto Franca , Paolini Paolo , Schwabe Daniel
Published: July 2002

Hypertext development should benefit from a systematic, structured development, especially in the case of large and complex applications. A structured approach to hypertext development suggests the notion of
authoring-in-the-large
. Authoring-in-the-large allows the description of overall classes of information elements and navigational structures of complex applications without much concern with implementation details, and in a system-independent manner. The paper presents HDM (Hypertext Design Model), a first step towards defining a general purpose model for authoring-in-the-large. Some of the most innovative features of HDM are: the notion of
perspective
; the identification of different
categories of links
(structural links, application links, and perspective links) with different representational roles; the distinction between
hyperbase
and
access structures
; and the possibility of easily integrating the structure of a hypertext application with its browsing semantics. HDM can be used in different manners: as a modeling device or as an implementation device. As a modeling device, it supports producing high level specifications of existing or to-be-developed applications. As an implementation device, it is the basis for designing tools that directly support application development. One of the central advantages of HDM in the design and practical construction of hypertext applications is that the definition of a significant number of links can be derived automatically from a conceptual-design level description. Examples of usage of HDM are also included.
The logical data model
Authors: Kuper Gabriel M. , Vardi Moshe Y.
Published: July 2002

We propose an object-oriented data model that generalizes the relational, hierarchical, and network models. A database scheme in this model is a directed graph, whose leaves represent data and whose internal nodes represent connections among the data. Instances are constructed from objects, which have separate names and values. We define a logic for the model, and describe a nonprocedural query language that is based on the logic. We also describe an algebraic query language and show that it is equivalent to the logical language.
Algorithm 720: An algorithm for adaptive cubature over a collection of 3-dimensional simplices
Authors: Berntsen Jarle , Cools Ronald , Espelid Terje O.
Published: July 2002

An adaptive algorithm for computing an approximation to the integral of each element in a vector of functions over a 3-dimensional region covered by simplices is presented. The algorithm is encoded in FORTRAN 77.

Locally, a cubature formula of degree 8 with 43 points is used to approximate an integral. The local error estimate is based on the same evaluation points. The error estimation procedure tries to decide whether the approximation for each function has asymptotic behavior, and different actions are taken depending on that decision.

The simplex with the largest error is subdivided into 8 simplices. The local procedure is then applied to each new region. This procedure is repeated until convergence.
Copyright and digital libraries
Authors: Samuelson Pamela
Published: July 2002

This issue of
Communications
highlights some of the many projects underway for the creation or enhancement of digital libraries. At the moment, no one seems to think there will be only one gargantuan digital library to sate the public's appetite for information. Rather, the expectation is that there will be many digital libraries, most of which will have specialized collections and will be internetworked together in a way loosely resembling today's Internet. Most digital library project planners are aware there are intellectual property issues that must be resolved in order to successfully deploy their libraries. Some proposals for digital library projects express an intent to resolve intellectual property issues as part of the overall plan for the library, albeit without much specificity about how this would be achieved in their systems [2, 4].
Job and health implications of VDT use
Authors: Sauter Steven L. , Gottlieb Mark S. , Jones Karen C. , Dodson Vernon N. , Rohrer Kathryn M.
Published: July 2002

Magnitudes and correlates of stress were investigated among 248 office workplace VDT users and 85 nonuser counterparts using field survey and objective physical measurement techniques. Other than a tenuous indication of increased eyestrain and reduced psychological disturbances among users, the two groups were largely undifferentiated on job-attitudinal, affective, and somatic manifestations of stress. However, aspects of working conditions were judged less favorably by VDT users. Stress mechanisms were much the same for both groups, involving psychosocial as well as physical environmental job attributes. For VDT users, the chair and workstation configuration were particularly important predictors of musculo-skeletal disturbances, as were corrective eyewear use and ambient lighting for visuo-ocular disturbances.
Global illumination of glossy environments using wavelets and importance
Authors: Christensen Per H. , Stollnitz Eric J. , Salesin David H. , DeRose Tony D.
Published: July 2002

We show how importance-driven refinement and a wavelet basis can be combined to provide an efficient solution to the global illumination problem with glossy and diffuse reflections. Importance is used to focus the computation on the interactions having the greatest impact on the visible solution. Wavelets are used to provide an efficient representation of radiance, importance, and the transport operator. We discuss a number of choices that must be made when constructing a finite element algorithm for glossy global illumination. Our algorithm is based on the standard wavelet decomposition of the transport operator and makes use of a four-dimensional wavelet representation for spatially and angularly varying radiance distributions. We use a final gathering step to improve the visual quality of the solution. Features of our implementation include support for curved surfaces as well as texture-mapped anisotropic emission and reflection functions.
Sorting on a parallel pointer machine with applications to set expression evaluation
Authors: Goodrich Michael T. , Kosaraju S. Rao
Published: July 2002

We present optimal algorithms for sorting on parallel CREW and EREW versions of the pointer machine model. Intuitively, one can view our methods as being based on a parallel mergesort using linked lists rather than arrays (the usual parallel data structure). We also show how to exploit the “locality” of our approach to solve the set expression evaluation problem, a problem with applications to database querying and logic-programming in
O
(log
n
) time using
O
(
n
) processors. Interestingly, this is an asymptotic improvement over what seems possible using previous techniques.
Quadrature prefiltering for high quality antialiasing
Authors: Guenter Brian , Tumblin Jack
Published: July 2002

This article introduces quadrature prefiltering, an accurate, efficient, and fairly simple algorithm for prefiltering polygons for scanline rendering. It renders very high quality images at reasonable cost, strongly suppressing aliasing artifacts. For equivalent RMS error, quadrature prefiltering is significantly faster than either uniform or jittered supersampling. Quadrature prefiltering is simple to implement and space-efficient; it needs only a small two-dimensional lookup table, even when computing nonradially symmetric filter kernels. Previous algorithms have required either three-dimensional tables or a restriction to radially symmetric filter kernels. Though only slightly more complicated to implement than the widely used box prefiltering method, quadrature prefiltering can generate images with much less visible aliasing artifacts.
Selection using a one-eyed cursor in a fish tank VR environment
Authors: Ware Colin , Lowther Kathy
Published: July 2002

This study investigates the use of a 2D cursor presented to one eye for target selection in Fish Tank VR and other stereo environments. It is argued that 2D selection of 3D objects should be less difficult than 3D selection. Vision research concerning binocular rivalry and the tendency we have to project images onto surfaces suggests that this mode of viewing will not seem particularly unnatural. A Fitt's Law experiment was done to directly compare target acquisition with a one-eyed 2D cursor and target acquisition using a 3D cursor. In both cases we used the same input device (Polhemus Fastrak) so that the device lag and gain parameters were exactly matched. The results show a large improvement in target acquisition time using the 2D cursor. The practical implications of this is that the 2D selection method using a one-eyed cursor in preferable to the 3D selection method. Theoretical implications relate to methods for extending Fitts' Law from the one-dimensional task for which it was designed to 2D and 3D tasks. We conclude that the existing approaches to this problem are not adequate.
V-Clip
Authors: Mirtich Brian
Published: July 2002

This article presents the Voronoi-clip, or V-Clip, collision detection alogrithm for polyhedral objects specified by a boundary representation. V-Clip tracks the closest pair of features between convex polyhedra, using an approach reminiscent of the Lin-Canny closest features algorithm. V-Clip is an improvement over the latter in several respects. Coding complexity is reduced, and robustness is significantly improved; the implementation has no numerical tolerances and does not exhibit cycling problems. The algorithm also handles penetrating polyhedra, and can therefore be used to detect collisions between nonvconvex polyhedra described as hierarchies of convex pieces. The article presents the theoretical principles of V-Clip, and gives a pseudocode description of the algorithm. It also documents various test that compare V-Clip, Lin-Canny, and the Enhanced GJK algorithm, a simplex-based algorithm that is widely used for the same application. The results show V-Clip to be a strong contender in this field, comparing favorably with the other algorithms in most of the tests, in term of both performance and robustness.
An
O
(
n
3
log
n
) deterministic and an
O
(
n
3
) Las Vegs isomorphism test for trivalent graphs
Authors: Galil Zvi , Hoffmann Christoph M. , Luks Eugene M. , Schnorr Claus P. , Weber Andreas
Published: July 2002

This paper describes an
O
(
n
3
log
n
) deterministic algorithm and an
O
(
n
3
) Las Vegas algorithm for testing whether two given trivalent graphs on
n
vertices are isomorphic. In fact, the algorithms construct the set of all isomorphisms between two such graphs, presenting, in particular, generators for the group of all automorphisms of a trivalent graph. The algorithms are based upon the original polynomial-time solution to these problems by Luks but they introduce numerous speedups. These include improved permutation-group algorithms that exploit the structure of the underlying 2-groups. A remarkable property of the Las Vegas algorithm is that it computes the set of all isomorphisms between two trivalent graphs for the cost of computing only those isomorphisms that map a specified edge to a specified edge.
Context interchange
Authors: Goh Cheng Hian , Bressan Stéphane , Madnick Stuart , Siegel Michael
Published: July 2002

TheContext Interchange strategypresents a novel perspective for mediated data access in which semantic conflicts among heterogeneous systems are not identified a priori, but are detected and reconciled by acontext mediatorthrough comparison ofcontexts axiomscorresponding to the systems engaged in data exchange. In this article, we show that queries formulated on shared views, export schema, and shared “ontologies” can be mediated in the same way using theContext Interchange framework. The proposed framework provides a logic-based object-oriented formalsim for representing and reasoning about data semantics in disparate systems, and has been validated in a prototype implementation providing mediated data access to both traditional and web-based information sources.
Boundary and Object Detection in Real World Images
Authors: Yakimovsky Yoram
Published: July 2002

A computer solution to the problem of automatic location of objects in digital pictures is presented. A self-scaling local edge detector that can be applied in parallel on a picture is described. Clustering algorithms and sequential boundary following algorithms process the edge data to local images of objects and generate a data structure that represents the imaged objects.
GO Is Polynomial-Space Hard
Authors: Lichtenstein David , Sipser Michael
Published: July 2002

It is shown that, given an arbitrary GO position on an
n
×
n
board, the problem of determining the winner is Pspace hard. New techniques are exploited to overcome the difficulties arising from the planar nature of board games. In particular, it is proved that GO is Pspace hard by reducing a Pspace-complete set, TQBF, to a game called generalized geography, then to a planar version of that game, and finally to GO.
Comparing design options for allocating communication media in cooperative safety-critical contexts
Authors: Fields Robert , Paternò Fabio , Santoro Carmen , Tahmassebi Sophie
Published: July 2002

In this article we present a method for evaluating and comparing design options for allocating communication media. The method pays particular attention to how such options support cooperation in an interactive safety-critical system. The comparison is performed using three sets of criteria based on task performance, analysis of user deviations and consequent hazards, and coordination. The explicit emphasis on hazards and communication issues, using actual tasks to guide the evaluation, ensures that designers attention is focused on the interactions where problems are likely to occur. We describe an application of the method to the design of access to new communication technology in an air traffic control environment.
The SIFT information dissemination system
Authors: Yan Tak W. , Garcia-Molina Hector
Published: July 2002

Information dissemination is a powerful mechanism for finding information in wide-area environments. An information dissemination server accepts long-term user queries, collects new documents from information sources, matches the documents against the queries, and continuously updates the users with relevant information. This paper is a retrospective of the Stanford Information Filtering Service (SIFT), a system that as of April 1996 was processing over 40,000 worldwide subscriptions and over 80,000 daily documents. The paper describes some of the indexing mechanisms that were developed for SIFT, as well as the evaluations that were conducted to select a scheme to implement. It also describes the implementation of SIFT, and experimental results for the actual system. Finally, it also discusses and experimentally evaluates techniques for distributing a service such as SIFT for added performance and availability.
Automatic sampling with the ratio-of-uniforms method
Authors: Leydold Josef
Published: July 2002

Applying the ratio-of-uniforms method for generating random variates results in very efficient, fast, and easy-to-implement algorithms. However parameters for every particular type of density must be precalculated analytically. In this article we show, that the ratio-of-uniforms method is also useful for the design of a black-box algorithm suitable for a large class of distributions, including all with log-concave densities. Using polygonal envelopes and squeezes results in an algorithm that is extremely fast. In opposition to any other ratio-of-uniforms algorithm the expected number of uniform random numbers is less than two. Furthermore, we show that this method is in some sense equivalent to transformed density rejection.
System Deadlocks
Authors: Coffman E. G. , Elphick M. , Shoshani A.
Published: July 2002

A problem of increasing importance in the design of large multiprogramming systems is the, so-called, deadlock or deadly-embrace problem. In this article we survey the work that has been done on the treatment of deadlocks from both the theoretical and practical points of view.
Model-driven development of Web applications
Authors: Fraternali Piero , Paolini Paolo
Published: July 2002

This paper describes a methodology for the development of WWW applications and a tool environment specifically tailored for the methodology. The methodology and the development environment are based upon models and techniques already used in the hypermedia, information systems, and software engineering fields, adapted and blended in an original mix. The foundation of the proposal is the conceptual design of WWW applications, using HDM-lite, a notation for the specification of structure, navigation, and presentation semantics. The conceptual schema is then translated into a “traditional” database schema, which describes both the organization of the content and the desired navigation and presentation features. The WWW pages can therefore be dynamically generated from the database content, following the navigation requests of the user. A CASE environment, called Autoweb System, offers a set of software tools, which assist the design and the execution of a WWW application, in all its different aspects, Real-life experiences of the use of the methodology and of the AutoWeb System in both the industrial and academic context are reported.
Power, politics, and MIS implementation
Authors: Markus M. Lynne
Published: July 2002

Theories of resistance to management information systems
(MIS)
are important because they guide the implementation strategies and tactics chosen by implementors. Three basic theories of the causes of resistance underlie many prescriptions and rules for
MIS
implementation. Simply stated, people resist
MIS
because of their own internal factors, because of poor system design, and because of the interaction of specific system design features with aspects of the organizational context of system use. These theories differ in their basic assumptions about systems, organizations, and resistance; they also differ in predictions that can be derived from them and in their implications for the implementation process. These differences are described and the task of evaluating the theories on the bases of the differences is begun. Data from a case study are used to illustrate the theories and to demonstrate the superiority, for implementors, of the interaction theory.
The management of end user computing
Authors: Rockart John F. , Flannery Lauren S.
Published: July 2002

End users can be classified into six distinct types. Each of them needs differentiated education, support, and control from the Information Systems function. To support a large number of their applications a new computing environment, “the third environment” must be developed by Information Systems (I/S) management. Close attention must also be paid by I/S management to the need to involve “functional support personnel” (end users in each functional area who spend most of their time programming and aiding other end users) in the I/S end user management process.