bluuebunny/crossref_metadata_2025 huggingface dataset:
APPLICATION OF ESR TO HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS II: ESR of Cu2+ AS A PROBE OF CRYSTAL GROWTH RATES OF Y2BaCuO5 IN THE MELTS OF Y1.8Ba2.4Cu3.4Ox
Authors: YAMAMOTO K. , KAWASHIMA S. , HOTTA K. , SUGAWARA K. , HIROSE H.
Published: July 2002

The effects of heat-treatment temperature (HTT) and heat-treatment period (HTP) on the growth rates of Y 2 BaCuO 5 in the melts with nominal composition of Y: Ba : Cu = 1.8 : 2.4 : 3.4 have been investigated. The ranges of HTT and HTP are 1000~1400° C and 1~120 minutes, respectively. The quantities of Cu 2+ in Y 2 BaCuO 5 have been obtained by ESR, and its growth rates in the aforementioned melts have been quantitatively measured as functions of HTT and HTP.
THE STRUCTURE OFBaTiO3ANDBaTiO3-YBa2Cu3O7-δTHIN FILMS STUDIED BY X-RAY TRIPLE-AXIS DIFFRACTION
Authors: YU W. X. , CUI S. F. , WU L. S. , MAI Z. H. , LI C. L. , CUI D. F. , CHEN Z. H.
Published: July 2002

The structures of BaTiO3thin films and BaTiO3/ YBa2Cu3O7-δbilayer films grown on SrTiO3and LaAlO3substrates, respectively by pulsed laser deposition, have been investigated by X-ray triple-axis diffraction. The orientation, the interface mismatch and strain status, and the in-plane and perpendicular lattice constants of the epilayers have been determined by reciprocal space map analysis. The results show that both the lattice constants and the structural imperfections of the BaTiO3layers are relevant to the oxygen partial pressure. The a⊥/a‖increases while the full width at half maximum (FWHM) of the rocking curves decreases with the decrease in the partial oxygen pressure.
UNSUPERVISED TEXTURE SEGMENTATION BY DETERMINING THE INTERIOR OF TEXTURE REGIONS BASED ON WAVELET TRANSFORM
Authors: LEE KUEN-LONG , CHEN LING-HWEI
Published: July 2002

Traditional approaches for texture segmentation via wavelet transform usually adopt textural features to achieve segmentation purposes. However, for a natural image, the characteristics of the pixels in a texture region are not similar everywhere from a global viewpoint, and over-segmentation often occurs. To deal with this issue, an unsupervised texture segmentation method based on determining the interior of texture regions is proposed. The key idea of the proposed method is that if the pixels of the input image can be classified into interior pixels (pixels within a texture region) and boundary ones, then the segmentation can be achieved by applying region growing on the interior pixels and reclassifying boundary pixels. Based on the fact that each pixel P within a texture region will have similar characteristics with its neighbors, after applying wavelet transform, pixel P will have similar response with its neighbors in each transformed subimage. Thus, by applying a multilevel thresholding technique to segment each subimage into several regions, pixel P and its neighbors will be assigned to the same region in most subimages. Based on these segmented results, an interior pixels finding algorithm is then provided to find all interior pixels of textural regions. The algorithm considers a pixel which is in the same region as its neighbors in most subimages as an interior pixel. The effectiveness of this method is proved by successfully segmenting natural texture images and comparing with other methods.
SUPER PERSISTENT CHAOTIC TRANSIENTS IN PHYSICAL SYSTEMS: EFFECT OF NOISE ON PHASE SYNCHRONIZATION OF COUPLED CHAOTIC OSCILLATORS
Authors: ANDRADE VICTOR , LAI YING-CHENG
Published: July 2002

A super persistent chaotic transient is typically induced by an unstable–unstable pair bifurcation in which two unstable periodic orbits of the same period coalesce and disappear as a system parameter is changed through a critical value. So far examples illustrating this type of transient chaos utilize discrete-time maps. We present a class of continuous-time dynamical systems that exhibit super persistent chaotic transients in parameter regimes of positive measure. In particular, we examine the effect of noise on phase synchronization of coupled chaotic oscillators. It is found that additive white noise can induce phase slips in integer multiples of 2π's in parameter regimes where phase synchronization is expected in the absence of noise. The average time durations of the temporal phase synchronization are in fact characteristic of those of super persistent chaotic transients. We provide heuristic arguments for the scaling law of the average transient lifetime and verify it using numerical examples from both the system of coupled Chua's circuits and that of coupled Rössler oscillators. Our work suggests a way to observe super persistent chaotic transients in physically realizable systems.
OUTPUT FEEDBACK ADAPTIVE VARIABLE STRUCTURE CONTROL OF CHAOS IN LORENZ SYSTEM
Authors: ARAUJO ALDAYR D. , SINGH SAHJENDRA N.
Published: July 2002

Based on the variable structure model reference adaptive control (VS-MRAC) theory, a new control system for the control of chaos in Lorenz system, using only the measured output variable, is designed. For the derivation of the control law, it is assumed that the parameters of the model are unknown. Moreover, it is assumed that a disturbance input is present in the system. It is shown that in the closed-loop system, the output variable tracks a given reference trajectory, and the state vector converges to the equilibrium state. Digital simulation results show that the closed-loop system has good transient behavior and robustness to the uncertainties and disturbance input.
INVARIANT CURVES OF THE GENERALIZED LYNESS EQUATIONS
Authors: JIBIN LI , ZHENGRONG LIU
Published: July 2002

In this Letter, invariant curves and oscillatory character of the generalized Lyness equation are investigated. For this equation, six different types of invariant regions are found. Some results of [Feuer et al., 1997] are corrected.
ON DYNAMICAL MODEL OF DRILLING WELLS
Authors: CHAKVETADZE G. , STEPIN A.
Published: July 2002

A family of one-dimensional mappings and their stochastic perturbations, related to the determining of cogged bits efficiency, is studied. A sufficient condition for the existence of absolutely continuous invariant probability measure is given, and the weak mixing property of this measure is established. We formulate and discuss the results concerning the stochastic stability of the invariant measure and its continuous dependence on the dimensionless parameter of the model. Some new problems are also outlined.
ON DEHN FUNCTIONS OF AMALGAMATIONS AND STRONGLY UNDISTORTED SUBGROUPS
Authors: BRICK STEPHEN G. , CORSON JON M.
Published: July 2002

We study the Dehn functions of amalgamations, introducing the notion of strongly undistorted subgroups. Using this, we give conditions under which taking an amalgamation does not increase the Dehn function, generalizing one aspect of the combination theorem of Bestvina and Feighn.

To obtain examples of strongly undistorted subgroups, we define and study the relative Dehn function of pairs of groups. As a result we obtain a new method of constructing examples of pairs of groups that are relatively hyperbolic in the sense of Farb.
ON THE CONTEXT-FREENESS OF THE θ-EXPANSIONS OF THE INTEGERS
Authors: FROUGNY CHRISTIANE , SOLOMYAK BORIS
Published: July 2002

Let θ>1 be a nonintegral real number such that the θ-expansion of every positive integer is finite. If the set of θ-expansions of all the positive integers is a context-free language, then θ must be a quadratic Pisot unit.

Résumé: Soit θ>1 un nombre réel non entier tel que le θ-développement de tout entier positif soit fini. Si l'on suppose que l'enslembe des θ-développements des entiers positifs forme un langage algébrique, alors θ doit être un nombre de Pisot quadratique unitaire.
ASYMPTOTIC ANALYSIS AND PARTIAL ASYMPTOTIC DECOMPOSITION OF DOMAIN FOR STOKES EQUATION IN TUBE STRUCTURE
Authors: BLANC F. , GIPOULOUX O. , PANASENKO G. , ZINE A. M.
Published: July 2002

The Stokes problem posed in tube structures (or finite rod structures (see Panasenko10)), i.e. in connected finite unions of the thin cylinders with the ratio of the diameter to the height of the order [Formula: see text], is considered. The asymptotic expansion of the solution is built and justified. Boundary layers are studied. Earlier the Navier–Stokes problem in one thin domain was considered by Nazarov.8 The method of asymptotic partial decomposition of the domain (MAPDD) (see Panasenko11) is applied and justified for the Stokes problem posed in a tube structures. This method reduces the initial Stokes problem to the Stokes problem in some small parts of the domain (where the boundary layers are "concentrated".)
AN ALGORITHM FOR CANCER RECOGNITION OF ULTRASOUND IMAGES
Authors: YFANTIS E. A. , LAZARAKIS T. , BEBIS G. , GALLITANO G. M.
Published: July 2002

An algorithm of cancer recognition of ultrasound images is developed in this paper. As we pointed out in our previous work, in order for cancer to survive it develops its own blood supply system, which is different than the supply system of normal tissue. The velocity of the blood flowing through the cancerous blood vessels is different than the velocity of the blood flowing through blood vessels of normal tissue. Due to this fact the ultrasound signal is absorbed differently in the cancerous areas than in the normal tissue areas. The energy of the signal, the continuity of the signal, the autocorrelation function and frequency domain properties are different in the normal tissue than in cancerous tissue. All of these indicators are weighted here for the purpose of classifying the image of the tissue as being cancerous or non cancerous. Preliminary results based on limited number of ultrasound images show that our method has the ability to recognize cancer in ultrasound images.
QUANTUM MEASUREMENTS AND PAUL TRAPS IN GRAVITATIONAL BACKGROUNDS
Authors: CAMACHO A.
Published: July 2002

In the present work we solve the motion equations of a particle in a Paul trap embedded in the gravitational field of a spherically symmetric mass. One of the ideas behind this work concerns the analysis of the effects that the gravity-induced quantum noise, stemming from the bodies in the neighborhood of the Paul trap, could have upon the enhancement of the quantum behavior of this system. This will be done considering a series expansion for the gravitational field of the source, and including in the Hamiltonian of the Paul trap only the first two terms. Higher-order contributions will be introduced as part of the environment of the system, and in consequence will not appear in the Hamiltonian. In other words, we put forward an argument that allows us to differentiate those gravitational degrees of freedom that will appear as an uncontrollable influence on the Paul trap. Along the ideas of the so-called restricted path integral formalism, we take into account the continuous monitoring of the position of our particle, and in consequence the corresponding propagators and probabilities, associated with the different measurements outputs, are obtained. Afterwards, the differential equation related to a quantum nondemolition variable is posed and solved, i.e., a family of quantum nondemolition parameters is obtained. Finally, a qualitative analysis of the effects on the system, of the gravity-induced environment, will be done.
A GRAVITOMAGNETIC EFFECT ON THE ORBIT OF A TEST BODY DUE TO THE EARTH'S VARIABLE ANGULAR MOMENTUM
Authors: IORIO LORENZO
Published: July 2002

The well known general relativistic Lense–Thirring drag of the orbit of a test particle in the stationary field of a central slowly rotating body is generated, in the weak-field and slow-motion approximation of General Relativity, by a gravitomagnetic Lorentz-like acceleration in the equations of motion of the test particle. In it the gravitomagnetic field is due to the central body's angular momentum supposed to be constant. In the context of the gravitational analogue of the Larmor theorem, such acceleration looks like a Coriolis inertial term in an accelerated frame. In this paper the effect of the variation in time of the central body's angular momentum on the orbit of a test mass is considered. It can be shown that it is analogue to the inertial acceleration due to the time derivative of the angular velocity vector of an accelerated frame. The possibility of detecting such effect in the gravitational field of the Earth with LAGEOS-like satellites is investigated. It turns out that the orbital effects are far too small to be measured.
WORMHOLE EFFECTIVE INTERACTIONS IN ANTI-DE SITTER SPACETIME
Authors: BARCELÓ CARLOS , GARAY LUIS J.
Published: July 2002

The effects of asymptotically anti-de Sitter wormholes in low-energy field theory are calculated in full detail for three different matter contents: a conformal scalar field, an electromagnetic field and gravitons. There exists a close relation between the choice of vacuum for the matter fields and the selection of a basis of the Hilbert space of anti-de Sitter wormholes. In the presence of conformal matter (i.e., conformal scalar or electromagnetic fields), this relation allows us to interpret the elements of these bases as wormhole states containing a given number of particles. This interpretation is subject to the same kind of ambiguity in the definition of particle as that arising from quantum field theory in curved spacetime. In the case of gravitons, owing to the nonconformal coupling, it is not possible to describe wormhole states in terms of their particle content.
TIME IN COSMOLOGY
Authors: BROUT R. , PARENTANI R.
Published: July 2002

The notion of time in cosmology is revealed through an examination of transition matrix elements of radiative processes occurring in the cosmos. To begin with, the very concept of time is delineated in classical physics in terms of correlations between the succession of configurations which describe a process and a standard trajectory called the clock. The total is an isolated system of fixed energy. This is relevant for cosmology in that the universe is an isolated system which we take to be homogeneous and isotropic. Furthermore, in virtue of the constraint which arises from reparametrization invariance of time, it has zero total energy. Therefore the momentum of the scale factor is determined from the energy of matter. In the quantum theory this is exploited through the use of WKB approximation for the wave function of the scale factor, justified for a large universe. The formalism then gives rise to matrix elements describing matter processes. These are shown to take on the form of usual time dependent quantum amplitudes wherein the temporal dependence is given by a background which is once more fixed by the total energy of matter.
PROSPECTS FOR MEDIUM-SCALE DIFFRACTION TOMOGRAPHY ON THE SHELF
Authors: SMIRNOV I. P. , KHILKO A. I. , CARUTHERS J. W.
Published: July 2002

Acoustical tomographical reconstruction of the location and sizes of spatially localized, random perturbation in a shallow-water oceanic waveguides is developed for mid-range distances. As examples of such perturbations, clouds of bubbles arising due to breaking wind waves and shoals of fishes are discussed. The ray approximation is used for the acoustical field description. The oceanic environment is presented as a medium with a background of uniformly distributed volume and surface random inhomogeneous fluctuations. Complex acoustical repetitive pulses are used as the probing signal. The receiving system consists of an array of spatially distributed hydrophones. The signals received from all hydrophones are processed on the basis of a tomographic algorithm including matched-filter processing in the spatial and frequency domains for reconstruction of the random time-delay statistical moments (average value and dispersion), which are descriptors of the observed random spatially localized inhomogeneity. As a specific model of random perturbation, a three-dimensional Gaussian cloud of fluctuations associated with parameters of a fish shoal is investigated. A vertically distributed array of receivers and a directed source of LFM-pulses are tested as the prototype of the tomographical system in a shallow waveguide with typical hydrology. Computer simulations of the tomographical reconstructions are conducted taking into account investigation of the influence of the level of additive noise on the accuracy of the reconstructed parameters.
FORMATION OF ORDERED MOLECULAR OVERLAYERS BY A TEMPERATURE-INDUCED SURFACE REACTION: HEXABUTYLOXYTRIPHENYLENE ON Cu(111)
Authors: WEGNER H. , WEISS K. , WÖLL CH.
Published: July 2002

Molecular monolayers obtained by the adsorption of hexabutyloxytriphenylene (HBT) on Cu (111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and thermal desorption spectroscopy (TDS). Adsorption at room temperature results in the formation of a disordered layer of physisorbed molecules. Annealing at temperatures of 600 K is found to induce a chemical reaction of the molecule with the substrate, leading to a desorption of the butyl fragments. This chemical reaction is accompanied by the formation of a highly ordered, well-defined oxytriphenylene layer which is stable for temperatures of up to 600 K.
CORRELATIONS BETWEEN STRUCTURE AND MAGNETISM IN THIN FILMS AND NANOSTRUCTURES
Authors: LE FÈVRE P. , MAGNAN H. , MIDOIR A. , CHANDESRIS D. , JAFFRÈS H. , FERT A. R. , PEYRADE J. P.
Published: July 2002

The bidimensionnal character of thin magnetic films deposited on single-crystal substrates, together with the occurrence of singular crystallographic structures, often confer on these systems electronic properties that cannot be found in bulk solids. For example, thin Ni layers deposited on Cu(001) present a perpendicular magnetic anisotropy in a very wide thickness range. We will show that this can be explained by a distorted structure of Ni, originating from the strain induced by the epitaxy on the Cu substrate. In this field of 2D magnetism, nanostructures are now investigated. Thin Fe layers on MgO(001) were cut into stripes by the "atomic saw" method: a compression of the substrate induces a dislocation slipping which saws both the substrate and the Fe film in regular and separated ribbons. The observed perpendicular to the stripes magnetization easy axis will be explained by a structural relaxation occurring during the structuration process. In these two studies, a precise structural characterization and simple magnetoelastic models allow one to describe the magnetic behaviors of these systems.
MAXIMIZING THE PROBABILITY OF ACHIEVING A GOAL IN THE CASE OF A PARTIALLY OBSERVED DRIFT PROCESS
Authors: ZOHAR GADY
Published: July 2002

We consider an investor with initial wealth X0<1, who wishes to maximize the probability of achieving a goal, XT = 1, when the stock's drift — modeled as a linear mean-reverting diffusion — is not observed directly but only via the measurement process. Adopting a martingale approach, a generalized Cameron–Martin (1945) formula then enables explicit computation of the value of the problem as well as the wealth process. The dynamic optimal allocation can then be determined using Clark's formula.
THE DYNAMICS OF COOPERATION
Authors: EL OUARDIGHI FOUAD
Published: July 2002

In this paper, the problem of cooperation is formulated in a dynamic framework. The proposed model interrelates the process of a joint production activity involving two partners and the dynamics of a common monitoring activity of their respective contributions. Analysis of the existence of a stationary equilibrium leads to a set of predictions on the long run issue of cooperation from given initial conditions.
FULL-VIEW: A VISUAL DATA-MINING ENVIRONMENT
Authors: POULET FRANÇOIS
Published: July 2002

This paper presents a 3D user-centered interactive graphical environment dedicated to data mining. The aims of this environment are to involve the user in the data mining process (to use domain knowledge during the process), to improve comprehensibility (of both the data and the results of data mining algorithms), to improve interactivity and to use algorithms from various research areas: statistics, data analysis, visualization and machine learning. The environment is made of a set of bulletin boards where the graphical tools will be mapped; bulletin boards are predefined or can be user-defined. Several different visualization tools might be used in a single display, these tools are linked together to improve data comprehensibility. The tools available in the environment are both graphical and non-graphical tools, they can be used alone or in a cooperative way. One of these tools is more detailed: CIAD, a new graphical interactive decision tree construction algorithm that allows bivariate splits and so gives smaller trees (improving result comprehensibility). Its results are compared to existing decision tree algorithms. This environment can be used on any personal computer (it is based on open-source software and so, is platform independent) as well as on high performance graphical systems like reality centers.
NOETHER SETTINGS FOR CENTRAL EXTENSIONS OF GROUPS WITH ZERO SCHUR MULTIPLIER
Authors: BENEISH ESTHER
Published: July 2002

Let G be a finite group, and let F be an algebraically closed field. The rational extension of F, F(G) = F(xg : g ∈ G) with G action given by hxg = xhg for g, h ∈ G, is referred to as the Noether setting for G. We show that if G is a group with zero Schur multiplier, then for any central extension G′ of G, F(G′)G′ and F(G)G are stably equivalent over F. That is, F(G)G is stably rational over F if and only if F(G′)G′ is stably rational over F. In particular, if G is a cyclic group or an abelian group with zero Schur multiplier, then F(G′) is stably rational over F.
CO-EVOLUTION IN ITERATED PRISONER'S DILEMMA WITH INTERMEDIATE LEVELS OF COOPERATION: APPLICATION TO MISSILE DEFENSE
Authors: DARWEN PAUL J. , YAO XIN
Published: July 2002

There is a widespread perception that in conflict situations, more intermediate choices between full peace and total war makes full peace less likely. This view is a motivation for opposing the proposed National Missile Defense. This perception is partly due to research in the abstract game of Iterated Prisoner's Dilemma. This paper critically evaluates this perception.
A note on estimating the cardinality of the projection of a database relation
Authors: Mukkamala Ravi , Jajodia Sushil
Published: July 2002

The paper by Ahad et al. [1] derives an analytical expression to estimate the cardinality of the projection of a database relation. In this note, we propose to show that this expression is in error even when all the parameters are assumed to be constant. We derive the correct formula for this expression.
Collaborative computing: collaboration first, computing second
Authors: Norman Donald A.
Published: July 2002

These articles on Collaborative Computing will seem out of place to a number of readers from the computer science community. Interesting articles perhaps, but what do they have to do with computers? Where is the science—that is, where is the mathematics, or the code? What have these issues to do with everyday practice?
A modified Adams method for nonstiff and mildly stiff initial value problems
Authors: Cash J. R. , Semnani S.
Published: July 2002

Adams predictor-corrector methods, and explicit Runge–Kutta formulas, have been widely used for the numerical solution of nonstiff initial value problems. Both of these classes of methods have certain drawbacks, however, and it has long been the aim of numerical analysts to derive a class of formulas that has the advantages of both Adams and Runge–Kutta methods and the disadvantages of neither! In this paper we derive a class of modified Adams formulas that attempts to achieve this aim. When used in a certain precisely defined predictor-corrector mode, these new formulas require three function evaluations per step, but have much better stability than Adams formulas. This improved stability makes the modified Adams formulas particularly effective for mildly stiff problems, and some numerical evidence of this is given. We also consider the performance of the new class of methods on the well-known DETEST test set to show their potential on general nonstiff initial value problems.
Algorithm 742: L2CXFT
Authors: Demetriou I. C.
Published: July 2002

A Fortran subroutine applies the method of Demetriou and Powell [1991] to restore convexity in n measurements of a convex function contaminated by random errors. The method minimizes the sum of the squares of the errors, subject to nonnegativity of second divided differences, in two phases. First, an approximation close to the optimum is derived in
O(n)
operations. Then, this approximation is used as the starting point of a dual-feasible quadratic programming algorithm that completes the calculation of the optimum. The constraints allow B-splines to be used, which reduce the problem to an equivalent one with fewer variables where the knots of the splines are determined automatically from the data points due to the constraint equations. The subroutine benefits from this reduction, since common submatrices that occur during the calculation are updated suitably. Iterative refinement improves the accuracy of some calculations when round-off errors accumulate. The subroutine has been applied to a variety of data having substantial differences and has performed fast and stably even for small data spacing, large
n
, and single-precision arithmetic. Driver programs and examples with output are provided to demonstrate the use of the subroutine.
University of Michigan Digital Library Project
Authors: Crum Laurie
Published: July 2002

The University of Michigan Digital Library Project (NSF-UMDL) is a multidisciplinary collaboration among faculty and staff throughout the University of Michigan. Initial use and evaluation of the NSF-UMDL will take place in science classes in Ann Arbor, Mich. high schools and the Stuyvesant High School in New York City, as well as instruction and research at the university. Access will also be available through Ann Arbor and New York City public libraries. External partners to the project include: IBM, Elsevier Science, Apple Computer, Bellcore, UMI International, McGraw-Hall, Encyclopaedia Britannica Educational Corporation, and Kodak.
Radiosity and hybrid methods
Authors: Neumann László , Neumann Attila
Published: July 2002

We examine various solutions to the global illumination problem, based on an exact mathematical analysis of the rendering equation. In addition to introducing efficient radiosity algorithms, we present a uniform approach to reformulate all of the basic radiosity equations used so far. Using hybrid methods we are able to analyze possible combinations of the view-dependent ray-tracing method and of the low-resolution radiosity-based method, and to offer new algorithms.
Superfast parallel discrete event simulations
Authors: Greenberg Albert G. , Lubachevsky Boris D. , Mitrani Isi
Published: July 2002

Nonconventional parallel simulations methods are presented, wherein speed-ups are not limited by the number of simulated components. The methods capitalize on Chandy and Sherman's space-time relaxation paradigm, and incorporate fast algorithms for solving recurrences. Special attention is paid to implementing these algorithms on currently available massively parallel SIMD computers. As examples, “superfast” simulations for open and closed queuing networks and for the slotted ALOHA communication protocol are discussed. Several of the simulations are implemented and show impressive computational speeds. This paper summarizes previous results of the authors and presents some new experiments and simulations.
Fixpoint logics, relational machines, and computational complexity
Authors: Abiteboul Serge , Vardi Moshe Y. , Vianu Victor
Published: July 2002

We establish a general connection between fixpoint logic and complexity. On one side, we have fixpoint logic, parameterized by the choices of 1st-order operators (inflationary or noninflationary) and iteration constructs (deterministic, nondeterministic, or alternating). On the other side, we have the complexity classes between P and EXPTIME. Our parameterized fixpoint logics capture the complexity classes P, NP, PSPACE, and EXPTIME, but equally is achieved only over ordered structures.

There is, however, an inherent mismatch between complexity and logic—while computational devices work on encodings of problems, logic is applied directly to the underlying mathematical structures. To overcome this mismatch, we use a theory of relational complexity, which bridges the gap between standard complexity and fixpoint logic. On one hand, we show that questions about containments among standard complexity classes can be translated to questions about containments among relational complexity classes. On the other hand, the expressive power of fixpoint logic can be precisely characterized in terms of relational complexity classes. This tight, three-way relationship among fixpoint logics, relational complexity and standard complexity yields in a uniform way logical analogs to all containments among the complexity classes P, NP, PSPACE, and EXPTIME. The logical formulation shows that some of the most tantalizing questions in complexity theory boil down to a single question: the relative power of inflationary vs. noninflationary 1st-order operators.
Algorithm 770: BVSPIS—a package for computing boundary-valued shape-preserving interpolating splines
Authors: Costantini P.
Published: July 2002

This article describes a software package for computing interpolating polynomial splines with arbitrary constraints on their shape and satisfying separable or nonseparable boundary conditions.
Remark on algorithm 706
Authors: Espelid Terje O.
Published: July 2002

We present corrections to Algorthm 706 (
ACM Trans. Math. Softw.
18, 3, Sept. 1992, pages 329–342; CALGO supplement 123).
The role graph model and conflict of interest
Authors: Nyanchama Matunda , Osborn Sylvia
Published: July 2002

We describe in more detail than before the reference model for role-based access control introduced by Nyanchama and Osborn, and the role-graph model with its accompanying algorithms, which is one way of implementing role-role relationships. An alternative role insertion algorithm is added, and it is shown how the role creation policies of Fernandez et al. correspond to role addition algorithms in our model. We then use our reference model to provide a taxonomy for kinds of conflict. We then go on to consider in some detail privilege-privilege and and role-role conflicts in conjunction with the role graph model. We show how role-role conflicts lead to a partitioning of the role graph into nonconflicting collections that can together be safely authorized to a given user. Finally, in an appendix, we present the role graph algorithms with additional logic to disallow roles that contain conflicting privileges.
Harp
Authors: Lim Ee-Peng , Lu Ying
Published: July 2002

The main purpose of a digital library is to facilitate users easy
access to enormous amount of globally networked information. Typically, this information includes preexisting public library catalog data, digitized document collections, and other databases. In this article, we describe the distributed query system of a digital library prototype system known as HARP. In the HARP project, we have designed and implemented a distributed query processor and its query front-end to support integrated queries to preexisting public library catalogs and structured databases. This article describes our experiences in the design of an extended Sequel (SQL) query language known as HarpSQL. It also presents the design and implementation of the distributed query system. Our experience in distributed query processor and user interface design and development will be highlighted. We believe that our prototyping effort will provide useful lessons to the development of a complete digital library infrastructure.
Client-server computing in mobile environments
Authors: Jing Jin , Helal Abdelsalam Sumi , Elmagarmid Ahmed
Published: July 2002

Recent advances in wireless data networking and portable information appliances have engendered a new paradigm of computing, called
mobile computing
, in which users carrying portable devices have access to data and information services regardless of their physical location or movement behavior. In the meantime, research addressing information access in mobile environments has proliferated. In this survey, we provide a concrete framework and categorization of the various ways of supporting mobile client-server computing for information access. We examine characteristics of mobility that distinguish mobile client-server computing from its traditional counterpart. We provide a comprehensive analysis of new paradigms and enabler concepts for mobile client-server computing, including mobile-aware adaptation, extended client-server model, and mobile data access. A comparative and detailed review of major research prototypes for mobile information access is also presented.
Finding circular attributes in attribute grammars
Authors: Rodeh Michael , Sagiv Mooly
Published: July 2002

The problem of finding the circular attributes in an grammar is considered. Two algorithms are proposed: the first is polynomial but yields conservative results while the second is exact but is potentially expontial. It is also shown that finding the circular attributes is harder than testing circularity.
Validation algorithms for pointer values in DBTG databases
Authors: Thomas D. A. , Pagurek B. , Buhr R. J.
Published: July 2002

This paper develops algorithms for verifying pointer values in DBTG (Data Base Task Group) type databases. To validate pointer implemented access paths and set structures, two algorithms are developed. The first procedure exploits the “typed pointer” concept employed in modern programming languages to diagnose abnormalities in directories and set instances. The second algorithm completes pointer validation by examining set instances to ensure that each DBTG set has a unique owner. Sequential processing is used by both algorithms, allowing a straightforward implementation which is efficient in both time and space. As presented, the algorithms are independent of implementation schema and physical structure.
An Algorithm for the Numerical Application of a Linear Operator
Authors: Jones Terence G.
Published: July 2002

The use of iterative procedures for interpolation is well-known. In this paper an iterative procedure, that may be used to compute values of derivatives and definite integrals, is derived. The procedure may also be used to compute the result of applying any linear operator to a function. The data used are a set of point values, at any reasonable set of abscissae. Within certain limitations, values of the derivatives may also be used. Worked examples are given to demonstrate the use of the procedure in three simple problems.
Algebraic Specification of Statistical Models for Analysis of Variance Computations
Authors: Hemmerle W. J.
Published: July 2002

A method for computing an analysis of variance from an algebraic specification of the statistical model is described. The model is written in a form consistent with usual statistical notation but also suitable for computer input and logical manipulation. Calculations necessary to obtain the analysis of variance are then determined by the model. An outline of the computational procedure is given.
Irreducible Topological Components of an Arbitrary Boolean Truth Function and Generation of Their Minimal Coverings
Authors: Natapoff Alan
Published: July 2002

An extension of the work initiated by Quine in reducing an arbitrary Boolean truth function to its minimal form is presented. Apart from the unique parts of the form, the entire class of nonunique forms is discussed. The portion of the truth table that is left uncovered by the unique parts of the solution is partitioned into topologically invariant components of which it is the direct sum. Each component may be covered independently of the others. The generation of the set of coverings of a component is developed around a central theorem: A union of cells, all basic to a particular vertex, contains no further cells basic to that vertex. A proof of the theorem is given. The components are components in the topological sense and are preserved under changes of representation. The discussion focuses on the general, unrefinable structure of a Boolean function, as opposed to practical means for calculating its minimal coverings.
Degrees of Unsolvability in Formal Grammars
Authors: Cudia Dennis F. , Singletary Wilson E.
Published: July 2002

The following theorem is a refinement of an unsolvability result due to E. Post:For any recursively enumerable degree D of recursive unsolvability there is a recursive class of sequences(of the same length)of nonempty words on an alphabet A such that the Post correspondence decision problem for that class is of degree D.

This theorem is proved and then applied to obtain degree analogues of the ambiguity problem and the common program problem for the class of context-free grammars.
Characteristic spectra of the curvature functional
Authors: Edwards John A.
Published: July 2002

A method is described for the eignevalues of piecewise smooth
C
2
extremum-energy curves. Typical interpolants are investigated within the framework of their eigensystems, and conclusions are presented concerning their natural modes of vibration, stability state, and limits of existence.

In the present discussion the word “spline” means exclusively an interpolating elastica.
Modeling layout tools to derive forward estimates of area and delay at the RTL level
Authors: Gelosh Donald S. , Steliff Dorothy E.
Published: July 2002

Forward estimates of area and delay facilitate effective decision-making when searching the solution space of digital designs. Current estimation techniques focus on modeling the layout result and fail to deliver timely or accurate estimates. This paper presents a novel approach to deriving these area and delay estimates at the RTL level by modeling the layout tool, rather than the layout result. This approach uses machine learning techniques to capture the relationships between general design features (i.e., topology, connectivity, common input, and common output) and layout concepts (i.e., relative placement). Experiments illustrate the formulation of the training set for machine learning in this domain, and also show how we can derive different tool models. Finally, they show how we can use the resultant model to derive forward estimates of area and delay in real-world designs.
Three-layer bubble-sorting-based nonManhattan channel routing
Authors: Yan Jin-Tai
Published: July 2002

It is well known that a nonManhattan channel router can use fewer routing tracks, and is never worse than a Manhattan router in a channel. To my knowledge, a three-layer bubble-sorting-based nonManhattan channel routing problem is always solved by the solution in a two-layer bubble-sorintg-based nonManhattan channel routing problem. Recently, an
O
(
kn
2
) heuristic algorithm [Chaudhary et al. 1991] and an
O
(
kn
2
) optimal algorithm [Chen et al. 1994] have been proposed, where
k
is the number of two-layer routing tracks and
n
is the number of terminals in a bubble-sorintg-based nonManhattan channel. In this paper we propose an optimal three-layer bubble-sorintg-based nonManhattan routing algorithm to minimize the number of three-layer routing tracks. Furthermore, the time complexity of theis optimal algorithm is proven to be in
O
(
hn
) time, where
h
is the number of three-layer routing tracks and
n
is the number of terminals in a bubble-sorting-based nonManhattan channel.
The expanding equilibrium algorithm
Authors: Schneider Michael H.
Published: July 2002

Spatial-equilibrium models are the primary framework for applied equilibrium modeling and policy analysis. An effective procedure for solving single commodity problems is described based on a variable dimension, complementary pivoting algorithm of Jones, Saigal, and Schneider. An implementation of this approach called
the expanding equilibrium algorithm
is described using network data structures and sparse graphs. The data structure that is used presorts the graph to avoid using linked lists while maintaining the flexibility to add arcs to the graph as the algorithm is executing. A computational experiment is developed showing the algorithm's ability to exploit the problem's underlying network and economic structure. Computational results are presented for a computer code written in C and tested on a large-scale, randomly generated problem.
Relative effects of central processor and input-output speeds upon throughput on the large computer
Authors: White Peter
Published: July 2002

Presented in this paper is a technique for determining the relative effects of the internal speed of the computer and the speed of the input-output units upon the overall speed of the system. Equations are derived which permit the determination of these effects from hardware usage measurements.
A tree convolution algorithm for the solution of queueing networks
Authors: Lam Simon S. , Lien Y. Luke
Published: July 2002

A new algorithm called the tree convolution algorithm, for the computation of normalization constants and performance measures of product-form queueing networks, is presented. Compared to existing algorithms, the algorithm is very efficient in the solution of networks with many service centers and many sparse routing chains. (A network is said to have sparse routing chains if the chains visit, on the average, only a small fraction of all centers in the network.) In such a network, substantial time and space savings can be achieved by exploiting the network's routing information. The time and space reductions are made possible by two features of the algorithm: (1) the sequence of array convolutions to compute a normalization constant is determined according to the traversal of a tree; (2) the convolutions are performed between arrays that are smaller than arrays used by existing algorithms. The routing information of a given network is used to configure the tree to reduce the algorithm's time and space requirements; some effective heuristics for optimization are described. An exact solution of a communication network model with 64 queues and 32 routing chains is illustrated.
Algorithms for the computation of all Mathieu functions of integer orders
Authors: Alhargan Fayez A.
Published: July 2002

The article presents methods for the computation of all Mathieu functions of integer order, which cover a large range of
n
and
h
; previous algorithms were limited to small values of
n
. The algorithms are given in sufficient detail to enable straightforward implementation. The algorithms can handle a large range of the order
n
(0-200) and the parameter
h
(0-4
n
).
A new integration algorithm for ordinary differential equations based on continued fraction approximations
Authors: Willers I. M.
Published: July 2002

A new integration algorithm is found, and an implementation is compared with other programmed algorithms. The new algorithm is a step-by-step procedure for solving the initial value problem in ordinary differential equations. It is designed to approximate poles of small integer order in the solutions of the differential equations by continued fractions obtained by manipulating the sums of truncated Taylor series expansions.

The new method is compared with the Gragg-Bulirsch-Stoer, and the Taylor series method. The Taylor series method and the new method are shown to be superior in speed and accuracy, while the new method is shown to be most superior when the solution is required near a singularity. The new method can finally be seen to pass automatically through singularities where all the other methods which are discussed will have failed.
Synchronizing processors with memory-content-generated interrupts
Authors: Hill J. Carver
Published: July 2002

Implementations of the “Lock-Unlock” method of synchronizing processors in a multiprocessor system usually require uninterruptable, memory-pause type instructions. An interlock scheme called read-interlock, which does not require memory-pause instructions, has been developed for a dual DEC PDP-10 system with real-time requirements. The read-interlock method does require a special “read-interlock” instruction in the repertoire of the processors and a special “read-interlock” cycle in the repertoire of the memory modules.

When a processor examines a “lock” (a memory location) with a read-interlock instruction, it will be interrupted if the lock was already set; examining a lock immediately sets it if it was not already set (this event sequence is a read-interlock cycle). Writing into a lock clears it.

Having the processor interrupted upon encountering a set lock instead of branching is advantageous if the branch would have resulted in an effective interrupt.
Interrupt driven programming
Authors: Zelkowitz Marvin
Published: July 2002

This note is an extension of the ideas expressed by Morgan [1]. He suggests a new form of interrupt which he proposes to use to control the execution of a program, in his case a file management system called DPL [2]. Simply stated, he has attached to every subroutine a Boolean expression which, if true, would cause that subroutine to be executed. Since his implementation is via software, a relatively time-consuming check must be made whenever some condition in the program changes (e.g. some variable has a value changed). A rather simple hardware addition to existing machines can easily implement this interrupt. The following is such a proposal.
Numerical Analysis: Quasilinearization and the estimation of differential operators from eigenvalues
Authors: Bellman R. E. , Kagiwada H. H. , Kalaba R. E. , Vasudevan R.
Published: July 2002

Given a linear ordinary differential operator containing several unknown constants and a number of its eigenvalues, the values of the unknown constants are estimated. A precise formulation is provided, and an effective numerical procedure for solution is indicated. The results of some computational experiments are given.
Panel discussion on computer appreciation
Authors: Organick Elliott I.
Published: July 2002

Session 19 of the ACM 20th Anniversary Conference on August 31, 1967, was entitled Education, Design Experiments, and Computer Appreciation. Its second half consisted of a panel discussion on computer appreciation, organized and chaired by Elliot I. Organick. The four panelists were Charles H. Davidson, Bernard A. Galler, Richard W. Hamming, and Alan J. Perlis. After making prepared statements, the panelist were joined in discussion by Andries van Dam and Arthur B. Kahn, who had presented papers in the first half.

This is a transcript of the panel discussion, condensed by Dr. Organick and edited him and the panelists. Some remarks referred to papers by van Dam and Kahn or to the discussion during the first half of the session. Pertinent papers are included in the references.
An improvement to iterative methods of polynomial factorization
Authors: Bingham John A. C.
Published: July 2002

Methods of polynomial factorization which find the zeros one at a time require the division of the polynomial by the accepted factor. It is shown how the accuracy of this division may be increased by dividing in order of both ascending and descending powers of the variable and choosing a crossover point which minimizes a very simply calculated error criterion.
A practical method for constructing LR (
k
) processors
Authors: Korenjak A. J.
Published: July 2002

A practical method for constructing LR(
k
) processors is developed. These processors are capable of recognizing and parsing an input during a single no-backup scan in a number of steps equal to the length of the input plus the number of steps in its derivation.

The technique presented here is based on the original method described by Knuth, but decreases both the effort required to construct the processor and the size of the processor produced. This procedure involves partitioning the given grammar into a number of smaller parts. If an LR(
k
) processor can be constructed for each part (using Knuth's algorithm) and if certain conditions relating these individual processors are satisfied, then an LR(
k
) processor for the entire grammar can be constructed for them. Using this procedure, an LR(1) parser for ALGOL has been obtained.