bluuebunny/crossref_metadata_2025 huggingface dataset:
MEL'NIKOV'S APPROXIMATION DOMINANCE: SOME EXAMPLES
Authors: GALLAVOTTI G. , GENTILE G. , MASTROPIETRO V.
Published: July 2002

We continue a previous paper to show that Mel'nikov's first order formula for part of the separatrix splitting of a pendulum under fast quasi periodic forcing holds, in special examples, as an asymptotic formula in the forcing rapidity.
SIMULATION OF PERCOLATION ON MASSIVELY-PARALLEL COMPUTERS
Authors: TIGGEMANN DANIEL
Published: July 2002

A novel approach to parallelize the well-known Hoshen–Kopelman algorithm has been chosen, suitable for simulating huge lattices in high dimensions on massively-parallel computers with distributed memory and message passing. This method consists of domain decomposition of the simulated lattice into strips perpendicular to the hyperplane of investigation that is used in the Hoshen–Kopelman algorithm. Systems of world record sizes, up to L = 4 000 256 in two dimensions, L = 20 224 in three, and L = 1036 in four, gave precise estimates for the Fisher exponent τ, the corrections to scaling Δ1, and for the critical number density nc.
ON THE NONINTEGRABLE HIROTA–SATSUMA SYSTEM OF COUPLED KdV EQUATIONS IN FLUID DYNAMICS
Authors: GAO YI-TIAN , TIAN BO , WEI GUANG-MEI
Published: July 2002

The coupled Korteweg-de Vries (KdV) equations are important in many fields, such as nonlinear optics, fluid dynamics, supersymmetry and so on. In this paper, we modify the recently proposed variable-coefficient balancing-act algorithm, and thus obtain some exact analytic solutions for the nonintegrable Hirota–Satsuma system of coupled KdV equations, which in fluid dynamics describe interactions of two long waves with different dispersion relations.
MECHANISM FOR POWERLAWS WITHOUT SELF-ORGANIZATION
Authors: SORNETTE DIDIER
Published: July 2002

A recent claim has been made that there must be a self-regulation in the waiting times to see hospital consultants on the ground that the relative changes in the size of waiting lists follow a power law.4 In agreement with simulations of Frecketon and Sutherland, we explain the general nonself-regulating mechanism underlying this result and derive the exponent value -2 exactly. In addition, we provide links with related phenomena encountered in many other fields.
SPACE–TIME TORSION AND PARITY VIOLATION: A GAUGE-INVARIANT FORMULATION
Authors: MUKHOPADHYAYA BISWARUP , SENGUPTA SOUMITRA , SUR SAURABH
Published: July 2002

The possibility of parity violation through space–time torsion has been explored in a scenario containing fields with different spins. Taking the Kalb–Ramond (KR) field as the source of torsion, an explicitly parity violating U (1) EM gauge-invariant theory has been constructed by extending the KR field with a Chern–Simons term.
COHERENT STATES FOR GENERALIZED LAGUERRE FUNCTIONS
Authors: JELLAL AHMED
Published: July 2002

We explicitly construct a Hamiltonian whose exact eigenfunctions are the generalized Laguerre functions. Moreover, we present the related raising and lowering operators. We investigate the corresponding coherent states by adopting the Gazeau–Klauder approach, where resolution of unity and overlapping properties are examined. Coherent states are found to be similar to those found for a particle trapped in a Pöschl–Teller potential of the trigonometric type. Some comparisons with Barut–Girardello and Klauder–Perelomov methods are noted.
ANTI-DE SITTER SPACE, THERMAL PHASE TRANSITION AND CONFINEMENT IN GAUGE THEORIES
Authors: WITTEN EDWARD
Published: July 2002

The correspondence between supergravity (and string theory) on AdS space and boundary conformal field theory relates the thermodynamics of [Formula: see text] super-Yang–Mills theory in four dimensions to the thermodynamics of Schwarzschild black holes in anti-de Sitter space. In this description, quantum phenomena such as the spontaneous breaking of the center of the gauge group, magnetic confinement and the mass gap are coded in classical geometry. The correspondence makes it manifest that the entropy of a very large AdS Schwarzschild black hole must scale "holographically" with the volume of its horizon. By similar methods, one can also make a speculative proposal for the description of large N gauge theories in four dimensions without supersymmetry.
HYDROSTATIC AND UNIAXIAL PRESSURE EFFECT ON La1.85Sr0.15CuO4 SUPERCONDUCTOR
Authors: ARUMUGAM S. , MORI N. , OHASHI M. , TAKEISHITA N. , TAKASHIMA H. , NODA T. , EISAKI H. , UCHIDA S.
Published: July 2002

We report hydrostatic and uniaxial pressure dependence of Tc and HTT to LTO transition temperature (Td) for La 1.85 Sr 0.15 CuO 4 superconducting crystals. It was found that the Tc increases and Td decreases with pressure along a-axis and vice versa along c-axis. The Tc does not show any change for pressure along (110) axis. The Tc increases (dTc/dP=+1.54 K/GPa ) and Td decreases (dTd/dP=-44 K/GPa ) under hydrostatic pressure. These anisotropic effects are discussed based on the variations in the amplitude of the tilt angle of oxygen octahedra, which would affect the pinning of fluctuating stripe order.
LUMINESCENCE PROCESS IN ANATASE TiO2 STUDIED BY TIME-RESOLVED SPECTROSCOPY
Authors: WATANABE M. , HAYASHI T. , YAGASAKI H. , SASAKI S.
Published: July 2002

We have studied time response of self-trapped exciton (STE) luminescence in anatase phase of TiO 2 as functions of excitation photon energy and temperature. The decay curves, which consist of two components obeying exponential and power-law decay, are found to depend significantly on the two parameters. The exponential component is stimulated efficiently under excitation near the absorption edge. This fact suggests that under such an excitation condition, photogenerated electron-hole pairs directly form STE's. It is found from temperature dependence of the decay curves that the exponential component is thermally unstable compared with the power-law one. It is inferred that the electron-hole pairs are thermally separated, and thus the direct formation of STE's is prevented.
CRITICAL BEHAVIOUR OF FERROELECTRIC THIN FILMS
Authors: WESSELINOWA JULIA M. , TRIMPER STEFFEN
Published: July 2002

Based on an Ising model in a transverse field (TIM) and using a Green's function formalism the critical exponents of the polarization β and of the longitudinal susceptibility γ are calculated for a ferroelectric thin film consisting of N layers. The exponents depends on the number of layers in a significant manner. Whereas for N=3 layers the exponents are β=0.131 and γ=1.739 there is a change over to β=0.315 and γ=1.239 in case of N=30. The datas are in a good agreement with predictions for 2D and 3D Ising systems. Using scaling laws other exponents like α, δ, η and ν are obtained, too.
INTRINSIC SURFACE AND INTERFACE STRESS OF LOW-DIMENSIONAL CRYSTALS
Authors: JIANG Q. , ZHAO D. S. , ZHAO M.
Published: July 2002

Based on the theoretical consideration on the size-dependence of solid-liquid interface energy, a model for the intrinsic interface stress of metallic, ionic and semiconductor nanosolid has been developed, free from adjustable parameters. Modeling predictions agree well with experimental observations and other theoretical results.
MICROMAGNETISM IN URu2Si2 AND HIGH TEMPERATURE SUPERCONDUCTORS
Authors: VIROSZTEK ATTILA , MAKI KAZUMI , DÓRA BALÁZS
Published: July 2002

It has been proposed, that unconventional density waves (UDW) are possible candidates for systems with hidden order parameter. Unlike in conventional density waves, no periodic modulation of either the charge-, or the spin-density is present in UDW, in spite of a clear thermodynamic signal. Although the unconventional spin density wave (USDW) has been suggested for the "antiferromagnetic" phase of URu2Si2 , the micromagnetism seen by neutron scattering has not been understood. We present here the calculation of the local spin density due to impurities in USDW, which describes quantitatively the neutron scattering data by Amitsuka et al. Further, we propose that the pseudogap phase in high temperature superconductors (HTSC) should also be USDW. Strong evidence for this are the micromagnetism seen by Sidis et al., and the optical dichroism seen by Campuzano et al.
NEURAL NETWORKS AS SOURCES OF CHAOTIC MOTOR ACTIVITY IN ANTS AND HOW COMPLEXITY DEVELOPS AT THE SOCIAL SCALE
Authors: MIRAMONTES OCTAVIO , SOLE RICARD V. , GOODWIN B. C.
Published: July 2002

We discuss a Neural Network model generating activation signals for locomotion in ants. The signals are chaotic and so are the temporal patterns of spontaneous activations in single ants. Active ants are able to move and interact with other nest mates. This process of movement-interaction generates periodic pulses of activity once the number of individuals reaches a certain density value. An algorithmic complexity measure is used for identifying accurately the transition from chaos into order. Finally, an Iterated Function System analysis reveals the richness of dynamical behavior that emerges when ant colonies are self-poised near such a transition.
TESTING CHAOS OF TIME SERIES: PORTMANTEAU STATISTICS UNDER AN ORDER TRANSFORMATION
Authors: LAI DEJIAN
Published: July 2002

This paper studies several portmanteau test statistics with a nonparametric order transformation for distinguishing independent and identically distributed (i.i.d.) random processes from noisy chaotic time series. These portmanteau test statistics are asymptotically distributed as a chi-square random variable under the null hypothesis of i.i.d. Gaussian series. In this Letter, we show that the asymptotic distributions of these portmanteau test statistics on the transformed series are still chi-square under the null hypothesis. The simulations indicate that direct use of these portmanteau test statistics yields low power in identifying chaos. However, with the proposed order transformation, the simulations show that these test statistics are still effective for identifying noisy low dimensional chaos in some cases.
TUNNELING PHASE LOGIC CELLULAR NONLINEAR NETWORKS
Authors: YANG TAO , KIEHL RICHARD A. , CHUA LEON O.
Published: July 2002

Based on a simple circuit model of a tunneling phase logic (TPL) element that is driven by a sinusoidal voltage source and biased by a DC voltage source, we present simulations of operations in cellular nonlinear networks (CNN) that could potentially be used to perform general computations in 2D arrays of simple, locally connected nanoscale devices. Some examples are presented to demonstrate the image computation capability of TPL–CNN. In particular, we use a simple 2D TPL–CNN structure to perform edge detection, image enhancement and image segmentation. Some cellular automata (CA)-like behaviors of our 2D TPL-CNN are also presented.
NONISOTROPIC SPATIOTEMPORAL CHAOTIC VIBRATION OF THE WAVE EQUATION DUE TO MIXING ENERGY TRANSPORT AND A VAN DER POL BOUNDARY CONDITION
Authors: CHEN GOONG , HSU SZE-BI , ZHOU JIANXIN
Published: July 2002

The imbalance of the boundary energy flow due to energy injection at one end and a nonlinear van der Pol boundary condition at the other end of the spatial one-dimensional interval can cause chaotic vibration of the linear wave equation [Chen et al., 1998b, 1998c]. However, such chaotic vibration is isotropic with respect to space and time because the two associated families of characteristics both propagate with the same speed and, thus, the "strength of chaos" is the same along both x and t directions. In this paper, we show that by including a mixed partial derivative linear energy transport term in the wave equation, nonlinearity in the van der Pol boundary condition can also cause chaotic vibration (without energy injection from the other end). Two new families of characteristics now travel with different speeds, leading to strong mixing of waves and nonisotropic spatiotemporal chaos. Parameter range for the route to chaos, including period-doubling, homoclinic orbits and Cantor-like invariant sets is classified. Numerical simulations of chaotic space-time profiles are also illustrated.
VIBRATION OF EXTERNALLY-FORCED FROUDE PENDULUM
Authors: LITAK GRZEGORZ , SPUZ-SZPOS GRZEGORZ , SZABELSKI KAZIMIERZ , WARMIŃSKI JERZY
Published: July 2002

Motion of self-excited Froude pendulum under external forcing were analyzed. Differential equation of motion includes the nonlinear damping term of Rayleigh's type. Using multiple time scale method and Lyapunov theory, vibrations, synchronization and stability of the system were examined. Chaotic motion was analyzed here by means of Lyapunov exponent and Melnikov approach.
CORRELATION FUNCTIONS OF CMB ANISOTROPY AND POLARIZATION
Authors: NG KIN-WANG , LIU GUO-CHIN
Published: July 2002

We give a full analysis of the auto- and cross-correlations between the Stokes parameters of the cosmic microwave background. In particular, we derive the windowing function for an antenna with Gaussian response in polarization experiment, and construct correlation function estimators corrected for instrumental noise. They are applied to calculate the signal to noise ratios for future anisotropy and polarization measurements. While the small-angular-scale anisotropy-polarization correlation would be likely detected by the MAP satellite, the detection of electric and magnetic polarization would require higher experimental sensitivity. For large-angular-scale measurements such as the being planned SPOrt/ISS, the expected signal to noise ratio for polarization is greater than one only for reionized models with high reionization redshifts, and the ratio is less for anisotropy-polarization correlation. Correlation and covariance matrices for likelihood analyses of ground-based and satellite data are also given.
MESON DECAY IN AN INDEPENDENT QUARK MODEL
Authors: CİFTCİ HAKAN , KORU HÜSEYIN
Published: July 2002

Leptonic decay widths and leptonic decay constants of light vector mesons and weak leptonic decay widths and weak decay constants of light and heavy pseudoscalar mesons have been studied in a field-theoretic framework based on the independent quark model with a scalar-vector power-law potential. The results are in very good agreement with the experimental data.
DETERMINATION OF MULTILAYER RELAXATIONS OF THE Cu(210) STEPPED SURFACE BY CALCULATION OF LEED INTENSITIES
Authors: GUO Y. P. , TAN K. C. , WEE A. T. S. , HUAN C. H. A.
Published: July 2002

In this report, we investigate the surface multilayer relaxation of clean Cu(210) by the Barbieri/Van Hove symmetrized automated tensor LEED calculation, based upon the multiple scattering theory. We have examined the change of Pendry R factor as a function of the structural and nonstructural variables in the calculation. The results show that a Rp factor of 0.20 can be achieved when the top 10 interlayer spacings of clean Cu(210) were optimized to experimental data using a muffin-tin radius of 1.217 Å and a muffin-tin zero of 8 eV. The first three interlayer spacings are d12=0.761± 0.04 Å, d23=0.759± 0.04 Å and d34=0.862± 0.03 Å, respectively (versus the bulk value of 0.807 Å). It therefore appears that the Cu(210) surface contracts to some extent, decreasing the surface roughness. The strain-induced multilayer relaxation of Cu(210) surface is discussed.
KINEMATICS OF THE ROTATIONAL SHIFT OF THE PROXIMAL CARPAL ROW
Authors: Gupta Ajay
Published: July 2002

The biomechanics of the wrist, particularly pertaining to its rotational shift, is ill understood and remains controversial. The rotational shift of the proximal carpal row comprises three components: the ulnar or the radial translation, volar or dorsal rotation and the supination, pronation. Newer mechanisms governing the rotational shift have been suggested, operating through either the radioulnar translation of the obliquely placed scaphoid or through an inherent mechanism in the lunate itself.

The wrist joint is made up of the distal carpal row and the radioulnar articulation, with the proximal carpal row as the intercalated segment to maintain the intervening gap between the two articular surfaces. The rotational shift has been suggested to be the crux providing great versatility to the intercalated segment, in order to conform to the changing dimensions of the gap between the distal radius and the distal carpal row during the movements of the wrist.
INFORMATION SERVICES FOR THE WEB: BUILDING AND MAINTAINING DOMAIN MODELS
Authors: GAL AVIGDOR , KERR SCOTT , MYLOPOULOS JOHN
Published: July 2002

The World Wide Web serves as a leading vehicle for information dissemination by offering information services, such as product information, group interactions, or sales transactions. Three major factors affect the performance and reliability of information services for the Web, namely the distribution of information which has resulted from the globalization of information systems, the heterogeneity of information sources, and the sources' instability caused by autonomous evolution. This paper focuses on integrating existing information sources, available via the Web, in the delivery of information services. The primary objective of the paper is to provide mechanisms for structuring and maintaining domain models for Web applications. These mechanisms are based on conceptual modeling techniques, where concepts are being defined and refined within a metadata repository through the use of instantiation, specialization and attribution. Also, active databases techniques are exploited to provide robust mechanisms for maintaining a consistent domain model in a rapidly evolving environment, such as the Web. Therefore, the main contribution of the paper lies in the provision of an architecture for semi-automatic generation and maintenance of user-oriented, semantic-based domain models that describe distributed heterogeneous information sources.
RECURRENCE PLOTS AND HURST EXPONENTS FOR FINANCIAL MARKETS AND FOREIGN-EXCHANGE DATA
Authors: HOŁYST J. A. , ŻEBROWSKA M.
Published: July 2002

Selected data from Polish and USA stock and bond markets as well as foreign-exchange data have been analysed by the use of recurrence plots and the Hurst method. It has been found that there exist significant correlations in some of analysed data chains. Values of recurrence ratios and ratios of determinism calculated from recurrence diagrams decrease significantly if one shuffles the data. The corresponding values of Hurst exponents are in the range 0.56–0.74 and they also decrease after shuffling. The lowest values of the Hurst exponent have been found for single shares at Polish stock market while the highest values are related to foreign-exchange data. The mean length of the cycle calculated from the behaviour of the Hurst exponent for Dow Jones index and S&P500 index is about 5 years while the Warsaw Stock Index WIG possesses the corresponding cycle of order of 11 months. The performed analysis shows that in the economical dynamics the main role is played by stochastic behaviour but traces of deterministic origin can be also seen.
A NOTE ON PORTFOLIO MANAGEMENT UNDER NON-GAUSSIAN LOGRETURNS
Authors: BENTH FRED ESPEN , KARLSEN KENNETH HVISTENDAHL , REIKVAM KRISTIN
Published: July 2002

We calculate numerically the optimal allocation and consumption strategies for Merton's optimal portfolio management problem when the risky asset is modelled by a geometric normal inverse Gaussian Lévy process. We compare the computed strategies to the ones given by the standard asset model of geometric Brownian motion. To have realistic parameters in our studies, we choose Norsk Hydro quoted on the New York Stock Exchange as the risky asset. We find that an investor believing in the normal inverse Gaussian model puts a greater fraction of wealth into the risky asset. We also investigate the limiting investment rate when the volatility increases. We observe different behaviour in the two models depending on which parameters we vary in the normal inverse Gaussian distribution.
The Performance of Growth Stocks and Value Stocks in the Pacific Basin
Authors: Bauman W. Scott , Conover C. Mitchell , Miller Robert E.
Published: July 2002

Many studies show that value stock strategies outperform growth stock strategies in U.S. markets and in international markets. However, the evidence is not clear as growth stocks have had higher returns in a few countries. Because the behavior of stock markets vary between different geographic regions, it is possible that the performance of these strategies may differ in the Pacific Rim region. We examine the performance of value stocks and growth stocks, defined on the basis of market price to book value per share, over the 10-year period 1986-1996, for six Pacific Rim countries. Based on over 11,900 annual stock returns, value stocks generally outperformed growth stocks over the 10-year period, and in the various Pacific Rim country stock markets. In addition, smaller cap stocks outperformed large cap stocks. Regardless of cap size, however, value stocks, on the whole, outperformed growth stocks. When growth stocks occasionally outperformed value stocks, the margin of difference tended to be small.
Deriving protocol specifications from service specifications including parameters
Authors: Gotzhein Reinhard , von Bochmann Gregor
Published: July 2002

The service specification concept has acquired an increasing level of recognition by protocol designers. This architectural concept influences the methodology applied to service and protocol definition. Since the protocol is seen as the logical implementation of the service, one can ask whether it is possible to formally derive the specification of a protocol providing a given service. This paper addresses this question and presents an algorithm for deriving a protocol specification from a given service specification. It is assumed that services are described by expressions, where names identifying both service primitives and previously defined services are composed using operators for sequence, parallelism and alternative. Services and service primitives may have input and output parameters. Composition of services from predefined services and service primitives is also permitted. The expression defining the service is the basis for the protocol derivation process. The algorithm presented fully automates the derivation process. Future work will focus on the optimization of traffic between protocol entities and on applications.
High-level language debugging for concurrent programs
Authors: Goldszmidt German S. , Yemini Shaula , Katz Shmuel
Published: July 2002

An integrated system design for debugging distributed programs written in concurrent high-level languages is described. A variety of user-interface, monitoring, and analysis tools integrated around a uniform process model are provided. Because the tools are language-based, the user does not have to deal with low-level implementation details of distribution and concurrency, and instead can focus on the logic of the program in terms of language-level objects and constructs. The tools provide facilities for experimentation with process scheduling, environment simulation, and nondeterministic selections. Presentation and analysis of the program's behavior are supported by history replay, state queries, and assertion checking. Assertions are formulated in linear time temporal logic, which is a logic particularly well suited to specify the behavior of distributed programs.

The tools are separated into two sets. The language-specific tools are those that directly interact with programs for monitoring of and on-line experimenting with distributed programs. The language-independent tools are those that support off-line presentation and analysis of the monitored information. This separation makes the system applicable to a wide range of programming languages. In addition, the separation of interactive experimentation from off-line analysis provides for efficient exploitation of both user time and machine resources. The implementation of a debugging facility for OCCAM is described.
Network locality at the scale of processes
Authors: Mogul Jeffrey C.
Published: July 2002

Packets on a LAN can be viewed as a series of references to and from the objects they address. The amount of locality in this reference stream may be critical to the efficiency of network implementations, if the locality can be exploited through caching or scheduling mechanisms. Most previous studies have treated network locality with an addressing granularity of networks or individual hosts. This paper describes some experiments tracing locality at a finer grain, looking at references to individual processes, and with fine-grained time resolution. Observations of typical LANs show high per-process locality; that is, packets to a host usually arrive for the process that most recently sent a packet, and often with little intervening delay.
Performance evaluation of cautious waiting
Authors: Hsu Meichun , Zhang Bin
Published: July 2002

We study a deadlock-free locking-based concurrency control algorithm, called
cautious waiting
, which allows for a limited form of waiting. The algorithm is very simple to implement. We present an analytical solution to its performance evaluation based on the mean-value approach proposed by Tay et al. [18]. From the modeling point of view, we are able to do away with a major assumption used in Tay's previous work, and therefore capture more accurately both the restart and the blocking rates in the system. We show that to solve for this model we only need to solve for the root of a polynomial. The analytical tools developed enable us to see that the cautious waiting algorithm manages to achieve a
delicate
balance between restart and blocking, and therefore is superior (i.e., has higher throughput to
both
the no-waiting (i.e., immediate restart) and the general waiting algorithms under a wide range of system parameters. The study substantiates the argument that balancing restart and blocking is important in locking systems.
Lessons learned from SUIT, the simple user interface toolkit
Authors: Pausch Randy , Conway Matthew , Deline Robert
Published: July 2002

In recent years, the computer science community has realized the advantages of GUIs (Graphical User Interfaces). Because high-quality GUIs are difficult to build, support tools such as UIMSs, UI Toolkits, and Interface Builders have been developed. Although these tools are powerful, they typically make two assumptions: first, that the programmer has some familiarity with the GUI model, and second, that he is willing to invest several weeks becoming proficient with the tool. These tools typically operate only on specific platforms, such as DOS, the Macintosh, or UNIX/X-windows.

The existing tools are beyond the reach of most undergraduate computer science majors, or professional programmers who wish to quickly build GUIs without investing the time to become specialists in GUI design. For this class of users, we developed
SUIT
, the
S
imple
U
ser
I
interface
T
oolkit. SUIT is an attempt to distill the fundamental components of an interface builder and GUI toolkit, and to explain those concepts with the tool itself, all in a short period of time. We have measured that college juniors with no previous GUI programming experience can use SUIT productively after less than three hours. SUIT is a C subroutine library which provides an external control UIMS, an interactive layout editor, and a set of standard “widgets,” such as sliders, buttons, and check boxes. SUIT-based applications run transparently across the Macintosh, DOS, and UNIX/X platforms. SUIT has been exported to hundreds of external sites on the internet. This paper describes SUIT's architecture, the design decisions we made during its development, and the lessons we learned from extensive observations of over 120 users.
Sparse dynamic programming I
Authors: Eppstein David , Galil Zvi , Giancarlo Raffaele , Italiano Giuseppe F.
Published: July 2002

Dynamic programming solutions to a number of different recurrence equations for sequence comparison and for RNA secondary structure prediction are considered. These recurrences are defined over a number of points that is quadratic in the input size; however only a sparse set matters for the result. Efficient algorithms for these problems are given, when the weight functions used in the recurrences are taken to be linear. The time complexity of the algorithms depends almost linearly on the number of points that need to be considered; when the problems are sparse this results in a substantial speed-up over known algorithms.
Simulating reactive systems by deduction
Authors: Feldman Yishai A. , Schneider Haim
Published: July 2002

Debugging is one of the main uses of simulation. Localizing bugs or finding the reasons for unclear behavior involves going backwards in time, whereas simulation goes forward in time. Therefore, identifying causes with the aid of most existing simulation tools usually requires repeating the simulation several times, each time with reduced holes in the sieve. An alternative is simulation by deduction, a technique in which the steps in the dynamic behavior of the simulated model are deduced by a reasoning system. A simulation system that uses simulation by deduction can give direct answers to questions about the reasons for the simulation results. By recording the support for its deductions, such a system can answer “why” and “why not” questions about the scenario.

Another benefit of simulation by deduction is that it enables symbolic simulation, that is, simulating a scenario given only a partial description of the environment and the simulated model. This allows verifying properties of an evolving design at any stage of the design process, and thus checking the consequences of the design decisions made so far. In order to allow deducing as much as possible from partial information, the axiom system has to be minimalistic, i.e., axioms have to require the minimum amount of knowledge of simulation inputs.

These ideas were implemented in a system called SIP, which simulates the behavior of reactive systems. SIP is capable of answering “why,” “why not,” and “what if” questions. It also has a limited capability of dealing with partial knowledge. SIP is based on a reasoning system that is responsible for deducing the effects of the external inputs on the state of the simulated model, and recording the support for its deductions. The logical basis for the deduction of a step in SIP is provided by a minimalistic axiom system for statecharts.

Although SIP simulates reactive systems described as statecharts, the principle of simulation by deduction is applicable to other types of systems and descriptions, provided only that they have a well-defined formal semantics.
A meta-environment for generating programming environments
Authors: Klint P.
Published: July 2002

Over the last decade, considerable progress has been made in solving the problems of automatic generation of programming/development environments, given a formal definition of some programming or specification language. In most cases, research has focused on the functionality and efficiency of the generated environments, and, of course, these aspects will ultimately determine the acceptance of environment generators. However, only marginal attention has been paid to the development process of formal language definitions itself. Assuming that the quality of automatically generated environments will be satisfactory within a few years, the development costs of formal language definitions will then become the next limiting factor determining ultimate success and acceptance of environment generators.

In this paper we describe the design and implementation of a meta-environment (a development environment for formal language definitions) based on the formalism ASF + SDF. This meta-environment is currently being implemented as part of the Centaur system and is, at least partly, obtained by applying environment generation techniques to the language definition formalism itself. A central problem is providing fully interactive editing of modular language definitions such that modifications made to the language definition during editing can be translated immediately to modifications in the programming environment generated from the original language definition. Therefore, some of the issues addressed are the treatment of formalisms with user-definable syntax and incremental program generation techniques.
Knowledge, probability, and adversaries
Authors: Halpern Joseph Y. , Tuttle Mark R.
Published: July 2002

What should it mean for an agent to know or believe an assertion is true with probability 9.99? Different papers [2, 6, 15] give different answers, choosing to use quite different probability spaces when computing the probability that an agent assigns to an event. We show that each choice can be understood in terms of a betting game. This betting game itself can be understood in terms of three types of adversaries influencing three different aspects of the game. The first selects the outcome of all nondeterministic choices in the system; the second represents the knowledge of the agent's opponent in the betting game (this is the key place the papers mentioned above differ); and the third is needed in asynchronous systems to choose the time the bet is placed. We illustrate the need for considering all three types of adversaries with a number of examples. Given a class of adversaries, we show how to assign probability spaces to agents in a way most appropriate for that class, where “most appropriate” is made precise in terms of this betting game. We conclude by showing how different assignments of probability spaces (corresponding to different opponents) yield different levels of guarantees in probabilistic coordinated attack.
Sentinel scheduling
Authors: Mahlke Scott A. , Chen William Y. , Bringmann Roger A. , Hank Richard E. , Hwu Wen-Mei W. , Rau B. Ramakrishna , Schlansker Michael S.
Published: July 2002

Speculative execution is an important source of parallelism for VLIW and superscalar processors. A serious challenge with compiler-controlled speculative execution is to efficiently handle exceptions for speculative instructions. In this article, a set of architectural features and compile-time scheduling support collectively referred to assentinel schedulingis introduced. Sentinel scheduling provides an effective framework for both compiler-controlled speculative execution and exception handling. All program exceptions are accurately detected and reported in a timely manner with sentinel scheduling. Recovery from exceptions is also ensured with the model. Experimental results show the effectiveness of sentinel scheduling for exploiting instruction-level parallelism and overhead associated with exception handling.
Optimizing array bound checks using flow analysis
Authors: Gupta Rajiv
Published: July 2002

Bound checks are introduced in programs for the run-time detection of array bound violations. Compile-time optimizations are employed to reduce the execution-time overhead due to bound checks. The optimizations reduce the program execution time through
elimination
of checks and
propagation
of checks out of loops. An execution of the optimized program terminates with an array bound violation if and only if the same outcome would have resulted during the execution of the program containing all array bound checks. However, the point at which the array bound violation occurs may not be the same. Experimental results indicate that the number of bound checks performed during the execution of a program is greatly reduced using these techniques.
The
Rendezvous
architecture and language for constructing multiuser applications
Authors: Hill Ralph D. , Brinck Tom , Rohall Steven L. , Patterson John F. , Wilner Wayne
Published: July 2002

When people have meetings or discussions, frequently they use
conversational props
: physical models, drawings, or other concrete representations of information used to enhance the exchange of information. If the participants are geographically separated, it is difficult to make effective use of props since each physical prop can only exist in one place. Computer applications that allow two or more users to simultaneously view and manipulate the same data can be used to augment human-to-human telecommunication. We have built the
Rendezvous
system is similar to many UIMSs or user interface toolkits in that it is intended to simplify the construction of graphical direct-manipulation interfaces. It goes beyond these systems by adding functionality to support the construction of multiuser applications. Based on experience with several large applications built with the
Rendezvous
system, we believe that it is useful for building conversational props and other computer-supported cooperative work (CSCW) applications. We present a list of required features of conversational props, some example applications built with the
Rendezvous
system, and a description of the
Rendezvous
system.
Integrating pointer variables into one-way constraint models
Authors: Vander Zanden Brad , Myers Brad A. , Giuse Dario A. , Szekely Pedro
Published: July 2002

Pointer variables have long been considered useful for constructing and manipulating data structures in traditional programming languages. This article discusses how pointer variables can be integrated into one-way constraint models and indicates how these constraints can be usefully employed in user interfaces. Pointer variables allow constraints to model a wide array of dynamic application behavior, simplify the implementation of structured objects and demonstrational systems, and improve the storage and efficiency of constraint-based applications. This article presents two incremental algorithms—one lazy and one eager— for solving constraints with pointer variables. Both algorithms are capable of handling (1) arbitrary systems of one-way constraints, including constraints that involve cycles, and (2) editing models that allow multiple changes between calls to the constraint solver. These algorithms are fault tolerant in that they can handle and recover gracefully from formulas that crash due to programmer error. Constraints that use pointer variables have been implemented in a comprehensive user interface toolkit, Garnet, and our experience with applications written in Garnet have proven the usefulness of pointer variable constraints. Many large-scale applications have been implemented using these constraints.
The TickerTAIP parallel RAID architecture
Authors: Cao Pei , Lin Swee Boon , Venkataraman Shivakumar , Wilkes John
Published: July 2002

Traditional disk arrays have a centralized architecture, with a single controller through which all requests flow. Such a controller is a single point of failure, and its performance limits the maximum number of disks to which the array can scale. We describe TickerTAIP, a parallel architecture for disk arrays that distributes the controller functions across several loosely coupled processors. The result is better scalability, fault tolerance, and flexibility.

This article presents the TickerTAIP architecture and an evaluation of its behavior. We demonstrate the feasibility by a working example, describe a family of distributed algorithms for calculating RAID parity, discuss techniques for establishing request atomicity, sequencing, and recovery, and evaluate the performance of the TickerTAIP design in both absolute terms and by comparison to a centralized RAID implementation. We also analyze the effects of including disk-level request-scheduling algorithms inside the array. We conclude that the Ticker TAIP architectural approach is feasible, useful, and effective.
An algorithm for concurrency control and recovery in replicated distributed databases
Authors: Bernstein Philip A. , Goodman Nathan
Published: July 2002

In a one-copy distributed database, each data item is stored at exactly one site. In a replicated database, some data items may be stored at multiple sites. The main motivation is improved reliability: by storing important data at multiple sites, the DBS can operate even though some sites have failed.

This paper describes an algorithm for handling replicated data, which allows users to operate on data so long as one copy is “available.” A copy is “available” when (i) its site is up, and (ii) the copy is not out-of-date because of an earlier crash.

The algorithm handles clean, detectable site failures, but not Byzantine failures or network partitions.
Debugging heterogeneous distributed systems using event-based models of behavior
Authors: Bates Peter C.
Published: July 2002

We describe a high-level debugging approach, Event-Based Behavioral Abstraction (EBBA), in which debugging is treated as a process of creating models of expected program behaviors and comparing these to the actual behaviors exhibited by the program. The use of EBBA techniques can enhance debugging-tool transparency, reduce latency and uncertainty for fundamental debugging activities, and accommodate diverse, heterogeneous architectures. Using events and behavior models as a basic mechanism provides a uniform view of heterogeneous systems and enables analysis to be performed in well-defined ways. Their use also enables EBBA users to extend and reuse knowledge gained in solving previous problems to new situations. We describe our behavior-modeling algorithm that matches actual behavior to models and automates many behavior analysis steps. The algorithm matches behavior in as many ways as possible and resolves these to return the best match to the user. It deals readily with partial behavior matches and incomplete information. In particular, we describe a tool set we have built. The tool set has been used to investigate the behavior of a wide range of programs. The tools are modular and can be distributed readily throughout a system.
Repository mirroring
Authors: Grosse Eric
Published: July 2002

Distributed administration of network repositories demands a low-overhead procedure for cooperating repositories around the world to ensure they hold identical contents. Netlib has adopted some refinements on the widespread scheme of anonymous ftp and s-R. Checksum files and two small C programs give an easily maintained system that copes with communication breakdowns and subtle changes in repository contents. The packaging of these C programs inside a shell pipeline provides an explicit command stream that can readily be checked before execution. Protecting files, keeping logs, and so forth become effortless and reliable. The same tools, applied on a smaller scale, allow more people to participate in the editorial work of maintaining a high-quality repository, by eliminating the need for directly manipulating files at remote sites.
Algorithm 743: WAPR--a Fortran routine for calculating real values of the
W
-function
Authors: Barry D. A. , Barry S. J. , Culligan-Hensley P. J.
Published: July 2002

We implement
W
-function approximation scheme described by Barry et al. A range of tests of the approximations is included so that the code can be assessed on any given machine. Users can calculate
W(x)
by specifying
x
itself or by specifying an offset from −exp(−1), the latter option necessitated by rounding errors that can arise for
x
close to −exp(−1). Results of running the code on a
SUN
workstation are included.
The MG retrieval system
Authors: Bell Timothy C. , Moffat Alistair , Witten Ian H. , Zobel Justin
Published: July 2002

Recent advances in compression and indexing techniques have yielded a qualitative change in the feasibility of large-scale full-text retrieval.
The computation of optical flow
Authors: Beauchemin S. S. , Barron J. L.
Published: July 2002

Two-dimensional image motion is the projection of the three-dimensional motion of objects, relative to a visual sensor, onto its image plane. Sequences of time-orderedimages allow the estimation of projected two-dimensional image motion as either instantaneous image velocities or discrete image displacements. These are usually called theoptical flow fieldor theimage velocity field. Provided that optical flow is a reliable approximation to two-dimensional image motion, it may then be used to recover the three-dimensional motion of the visual sensor (to within a scale factor) and the three-dimensional surface structure (shape or relative depth) through assumptions concerning the structure of the optical flow field, the three-dimensional environment, and the motion of the sensor. Optical flow may also be used to perform motion detection, object segmentation, time-to-collision and focus of expansion calculations, motion compensated encoding, and stereo disparity measurement. We investigate the computation of optical flow in this survey: widely known methods for estimating optical flow are classified and examined by scrutinizing the hypothesis and assumptions they use. The survey concludes with a discussion of current research issues.
Sequential patterns in information systems development
Authors: Robey Daniel , Newman Michael
Published: July 2002

We trace the process of developing and implementing a materials management system in one company over a 15-year period. Using a process research model developed by Newman and Robey, we identify 44 events in the process and define them as either encounters or episodes. Encounters are concentrated events, such as meetings and announcements, that separate episodes, which are events of longer duration. By examining the sequence of events over the 15 years of the case, we identify a pattern of repeated failure, followed by success. Our discussion centers on the value of detecting and displaying such patterns and the need for theoretical interpretation of recurring sequences of events. Five alternative theoretical perspectives, originally proposed by Kling, are used to interpret the sequential patterns identified by the model. We conclude that the form of the process model allows researchers who operate from different perspectives to enrich their understanding of the process of system development.
Equilibrium states of Runge Kutta schemes
Authors: Hall George
Published: July 2002

Understanding the behavior of Runge-Kutta codes when stability considerations restrict the stepsize provides useful information for stiffness detection and other implementation details. Analysis of equilibrium states on test problems is presented which provides predictions and insights into this behavior. The implications for global error are also discussed.
Ethics and computer use
Authors: Conger Sue , Loch Karen D.
Published: July 2002

Over the past 50 years, computers have undergone transformation from monolithic number crunchers, to centralized repositories of management information systems, to distributed, networked, cyberspace support systems. During the same period, uses of computers have moved from computational problems to life support, from machine language to GUIs, from abstractions of work to virtual reality on the World-Wide Web. These transformations have brought with them situations that have ethical implications.
Values, personal information privacy, and regulatory approaches
Authors: Milberg Sandra J. , Burke Sandra J. , Smith H. Jeff , Kallman Ernest A.
Published: July 2002

The relationships among nationality, cultural values, personal information privacy concerns, and information privacy regulation are examined in this article.
Taking “computer literacy” literally
Authors: Van Dyke Carolynn
Published: July 2002

Computer literacy implies an analogy between computer-related skills and linguistic literacy that has not been seriously explored. Recent studies of linguistic literacy can illuminate the definition of computer literacy and can suggest new ways of teaching it.
A statistical technique for comparing heuristics: an example from capacity assignment strategies in computer network design
Authors: Nance Richard , Moose Robert , Foutz Robert
Published: July 2002

An analysis of variance (ANOVA) model is developed for determining the existence of significant differences among strategies employing heuristics. Use of the model is illustrated in an application involving capacity assignment for networks utilizing the dynamic hierarchy architecture, in which the apex node is reassigned in response to changing environments. The importance of the model lies in the structure provided to the evaluation of heuristics, a major need in the assessment of benefits of artificial-intelligence applications. A nested three-factor design with fixed and random effects provides a numerical example of the model.