bluuebunny/crossref_metadata_2025 huggingface dataset:
PHASE TRANSITIONS IN THE TWO-DIMENSIONAL O(3) MODEL
Authors: BLÖTE HENK W. J. , GUO WENAN
Published: July 2002

We use Monte Carlo, transfer-matrix and finite-size scaling methods to investigate two-dimensional O (n) models with n > 2, in particular the case n = 3 which includes the classical Heisenberg model. Depending on the type of interaction and the lattice structure, two different types of phase transitions are present. One type resembles the hard-hexagon transition and occurs in the loop representation of the honeycomb O (n) model. The other type is a first-order transition which occurs for spin-spin interactions that are strongly nonlinear in the neighbor-spin products. When the nonlinearity is decreased, the first-order line ends in a critical point. The existence of the first-order line is in agreement with mean-field theory as well as with high- and low-temperature approximations.
THE THREE-STATE CHIRAL CLOCK MODEL
Authors: JIN BAI-QI , AU-YANG HELEN , PERK JACQUES H. H.
Published: July 2002

We give a brief summary of our recent works on the three-state chiral clock model. In these works, we use improved effective field theories with clusters being strips, infinite in the chiral direction and finite in the non-chiral direction. Hence, effective-field transfer matrix methods can be employed in these studies. The effective fields are determined by the Gibbs-Bogoliubov free energy variational principle, leading to Weiss or Bethe approximations in different studies respectively. By systematic improvement of these approximations, i.e. widening the strips, these studies point to the conclusion that there is no Lifshitz point existing at finite non-zero chirality.
Properties of ER Fluids Comprised of Liquid Crystalline Polymers
Authors: Inoue Akio , Ide Yoichiroh , Maniwa Shyunji , Yamada Hiroyuki , Oda Hiroji
Published: July 2002

Side-chain liquid crystalline polysiloxanes (LCS) diluted with solvents show a large increase in viscosity and a newtonian flow under an electric field.

Two types of solvent-diluted LCSs, A and B, are presented and their properties are described in this paper. Type A shows a large temperature-dependent ER effect a quick response of msec. order to an electric field and a dynamic behavior similar to that of a low molecular weight liquid crystal. Type B shows a stable ER effect throughout a wide range of temperatures up to 150°C, a two-step response of shear stress curve upon application of DC electric field and a micron-sized droplets structure which deforms with the electric field. The generation mechanisms of ER effect on the two types were discussed with the data of dynamic and morphological changes, referring those on a low molecular liquid crystal and a particle dispersion type ER fluid.
THE TRANSPORT BEHAVIOR NEAR THE JUNCTION INTERFACE IN RAMP JOSEPHSON JUNCTIONS WITH A GRADED BARRIER
Authors: Sun J. L. , Gao J.
Published: July 2002

The stationary properties of high- T c ramp type Josephson junctions with a graded Y 1-x Pr x Ba 2 Cu 3 O y barrier have been studied. In such a structure the composition of the Y 1-x Pr x Ba 2 Cu 3 O y barrier is continuely changed as x increasing from 0 to 1 at one side of the PrBCO barrier and vice verse at the other side. The critical current of these junctions showed a nearly linear dependence on the temperature. The experimental results were discussed in comparing with theoretical models.
THE RELAXATION THEORY OF ELECTROELASTICITY AND DIELECTRIC PROPERTIES OF IONIC LIQUIDS
Authors: ODINAEV S. , ODJIMAMADOV I.
Published: July 2002

An analytic dynamic coefficient of electroconductivity σ(ω) and electroelasticity modulus ε(ω) for ionic liquids is obtained from the kinetic equations for one- and two-particle distribution functions. These expressions include both structural and translational relaxation processes which proceed in the ionic liquids. An asymptotic behavior of σ(ω) and corresponding ∊(ω) at low and high frequencies is considered. It is shown that the obtained results for electroconductivity allow us to investigate dielectric properties of ionic liquids.
A NOTE ON THE AlB2 TYPE STRUCTURE
Authors: CHEN X. L. , TU Q. Y. , DAI L. , XU Y. P.
Published: July 2002

In this paper, the crystal structures of a series of diborides are analyzed based on the hard ball model. We show that the packing efficiency has a close relation with the lattice parameter ratio c/a and the closest packing is achieved at c/a = 1.074. For the compounds with c/a < 1.074, the packing is loose along the basal plane and the B–B bond is under compression while with c/a > 1.074 the packing is loose along the c-direction and the B–B bond is stretched. The structures will be unstable as the c/a value deviates from 1.074. MgB2 has the largest value of c/a among the examined diborides, except for lanthanide diborides and YB2.
PROCEDURES OF GAUGE SYMMETRY BREAKING IN SUPERCONDUCTIVITY: COMMENT ON SPONTANEITY
Authors: KOLLEY W.
Published: July 2002

The breakdown of the U(1) gauge invariance in conventional superconductivity is re-examined by drawing parallels between the BCS and Abelian Higgs models. The global and local U(1) symmetries are broken spontaneously and explicitly in view of the Goldstone and Elitzur theorems, respectively. The approximations at which spontaneity comes into the symmetry-breaking condensation, that are differently interpreted in the literature, are clarified.
NONORGANIZED DETERMINISTIC DISSYMMETRIES INDUCE REGULARITY IN SPATIOTEMPORAL DYNAMICS
Authors: ARENA PAOLO , CAPONETTO RICCARDO , FORTUNA LUIGI , RIZZO ALESSANDRO
Published: July 2002

This letter deals with the remarkable effects observed in arrays of circuits and systems when parameter spatial diversity is induced by using chaos, leading to pattern formation and regularization. The communication emphasizes the fact that generating spatial dissymmetries by using chaos enhances regularity and pattern formation capability with respect to the case in which diversity is generated by random processes. Several examples are reported showing the previous conjecture. A further aim of the paper is to emphasize that the introduction of a small amplitude chaotic spatial diversity could control chaos in both 1D and 2D large scale connected arrays of nonlinear circuits like Cellular Neural Network (CNN).
OBSERVED ROTATION NUMBERS IN FAMILIES OF CIRCLE MAPS
Authors: SAUM MICHAEL A. , YOUNG TODD R.
Published: July 2002

Noninvertible circle maps may have a rotation interval instead of a unique rotation number. One may ask which of the numbers or sets of numbers within this rotation interval may be observed with positive probability in term of Lebesgue measure on the circle. We study this question numerically for families of circle maps. Both the interval and "observed" rotation numbers are computed for large numbers of initial conditions. The numerical evidence suggests that within the rotation interval only a very narrow band or even a unique rotation number is observed. These observed rotation numbers appear to be either locally constant or vary wildly as the parameter is changed. Closer examination reveals that intervals with wild variation contain many subintervals where the observed rotation numbers are locally constant. We discuss the formation of these intervals. We prove that such intervals occur whenever one of the endpoints of the rotation interval changes. We also examine the effects of various types of saddle-node bifurcations on the observed rotation numbers.
FROM SYMBOLIC DYNAMICS TO A DIGITAL APPROACH
Authors: KARAMANOS K.
Published: July 2002

We show that the numbers generated by the symbolic dynamics of Feigenbaum attractors are transcendental. Due to the asymmetry of the chaotic attractors of unimodal maps around the maximum in the general case, a standard conjecture, that the occurrence of chaos is related to the transcendence of the number defined by the corresponding symbolic dynamics is reassessed and formulated in a quantitative manner. It is concluded that transcendence may provide an appropriate measure of complexity.
THE BREAKDOWN OF SYNCHRONIZATION IN SYSTEMS OF NONIDENTICAL CHAOTIC OSCILLATORS: THEORY AND EXPERIMENT
Authors: CHUBB JENNIFER , BARRETO ERNEST , SO PAUL , GLUCKMAN BRUCE J.
Published: July 2002

The synchronization of chaotic systems has received a great deal of attention. However, most of the literature has focused on systems that possess invariant manifolds that persist as the coupling is varied. In this paper, we describe the process whereby synchronization is lost in systems of nonidentical coupled chaotic oscillators without special symmetries. We qualitatively and quantitatively analyze such systems in terms of the evolution of the unstable periodic orbit structure. Our results are illustrated with data from physical experiments.
INTERMITTENT LAG SYNCHRONIZATION IN A PAIR OF COUPLED CHAOTIC OSCILLATORS
Authors: VALLADARES D. L. , BOCCALETTI S. , CARUSELA M. F.
Published: July 2002

The intermittent lag synchronization of two nonidentical symmetrically coupled Rössler systems is investigated numerically. This phenomenon orginates by intermittent bursts away from a principal lag synchronization regime, that correspond to jumps of the system toward other lag configurations. The global scenario of transitions toward a perfect lag synchronization regime may be tracked by the identification of the different lag configurations and the measure of the fraction of time spent by the system in each one of them. The statistical properties of this intermittent behavior are described and compared with the ones of on–off intermittency.
CHARACTERIZATION OF DYNAMIC BIFURCATIONS IN THE FREQUENCY DOMAIN
Authors: ITOVICH GRISELDA R. , MOIOLA JORGE L.
Published: July 2002

In this paper dynamical systems with certain degenerate Hopf bifurcations are considered. An analysis of the bifurcation behavior is proposed using several tools from the frequency domain approach. The analyzed bifurcations are the building blocks to understand the multiplicity of Hopf bifurcation points and to propose certain strategies in the future for controlling the bifurcation behavior in nonlinear systems.
TURBULENCE AND COHERENT STRUCTURES IN SUBSONIC SUBMERGED JETS: CONTROL OF THE TURBULENCE
Authors: LANDA P. S. , ZAIKIN A. A. , GINEVSKY A. S. , VLASOV YE. V.
Published: July 2002

The onset of turbulence and formation of large-scale patterns (coherent structures) in subsonic submerged jets are considered from the standpoint of noise-induced nonequilibrium phase transitions of the second kind. It is shown by the example of noise-induced oscillations of a pendulum with a randomly vibrating suspension axis that such a transition can be controlled by an additional harmonic action. The known possibility of notable suppression or intensification of turbulence in jets and free shear layers by means of a slight acoustic action at one or another frequency can be attributable to such control.
CLUSTER DYNAMICS IN SYSTEMS WITH CONSTANT MEAN FIELD COUPLING
Authors: PARRAVANO A. , COSENZA M. G.
Published: July 2002

A procedure to predict the occurrence of periodic clusters in a system of globally coupled maps displaying a constant mean field is presented. The method employs the analogy between a system of globally coupled maps and a single map driven by a constant force. By obtaining the asymptotic orbits of the driven map, an associated coupling function can be constructed. This function allows to establish a direct connection between both systems. Some applications are shown.
UNIFORMITIES ON FREE SEMIGROUPS
Authors: PIN J.-E. , WEIL P.
Published: July 2002

It is known that the profinite completions of a free semigroup which are associated with a pseudovariety of semigroups or of ordered semigroups, can be defined by an écart or a quasi-écart. We characterize those quasi-écarts and those quasi-uniformities which arise in this fashion. We also prove an Eilenberg-like one-to-one correspondence between pseudovarieties of ordered semigroups and so-called varieties of quasi-uniformities.

Résumé: On sait que les complétions profinies d'un semigroupe libre qui sont associées à une pseudovariété de semigroupes ou de semigroupes ordonnés peuvent être définies par un écart ou un quasi-écart. Nous caractérisons les quasi-écarts et les quasi-uniformités qui peuvent étre obtenues de cette façon. Nous démontrons également l'existence d'une correspondance injective "à la Eilenberg", entre pseudovariétés de semigroupes ordonnés et ce que nous appelons des variétés de quasi-uniformités.
UNDECIDABILITY, AUTOMATA, AND PSEUDOVARITIES OF FINITE SEMIGROUPS
Authors: RHODES JOHN
Published: July 2002

The author proves for each of the operations # equalling *, °, **, □ or m, there exist pseudovarieties of finite semigroups [Formula: see text] and [Formula: see text] with decidable membership problems, such that [Formula: see text] has an undecidable membership problem.

In addition, if [Formula: see text] denotes the pseudovariety of all finite aperiodic semigroups, [Formula: see text] denotes the pseudovariety of all finite groups, and [Formula: see text](E) denotes the pseudovariety of all finite aperiodic semigroups satisfying the finite number of equations E, then it is proved that there exists E such that [Formula: see text](E) has an undecidable membership problem. Note [Formula: see text] equals all semigroups of complexity ≤1.

Section 6 is expanded into a joint paper with B. Steinberg, following this paper.
SPATIALLY VARYING DISCRETE ORDINATES METHODS IN XY-GEOMETRY
Authors: BAL GUILLAUME
Published: July 2002

We consider the coupling of angular discretizations of the two-dimensional linear transport equation. We show the well-posedness of the coupled problem and give an error estimate. The angular discretization is based on the discrete ordinates method. It involves a quadrature rule specifically designed for our coupling. The theory uses the integral formulation of transport and will be demonstrated on simplified geometries.
CONSTRUCTION METHOD OF SUBJECTIVE MODEL EXPRESSING COLOR IMPRESSIONS
Authors: KAWAMURA MAKOTO , ONISAWA TAKEHISA
Published: July 2002

This paper proposes a method to construct a subjective model expressing color impressions, which is expressed by fuzzy rules. Hue and tone are dealt with in the premise part of fuzzy rules and the degree of color impressions is expressed in the consequent part. Color impressions are the basic concept known as psychological effects of colors. In this paper two pieces of subjective information are considered in order to construct the subjective model. One is the information of the absolute relationship between a color and the subjective degree of its impressions. And the other is the one about the relative relationship between colors on a subjective measure in terms of color impressions. Two kinds of questionnaires, called the absolute and the comparative judgments, are performed to get the subjective information. Additionally, this paper proposes improves the method so that is more applicable to the practical use. A validity of the proposed methods are examined by evaluation experiments.
UNKNOTTING VIRTUAL KNOTS WITH GAUSS DIAGRAM FORBIDDEN MOVES
Authors: NELSON SAM
Published: July 2002

The forbidden moves can be combined with Gauss diagram Reidemeister moves to obtain move sequences with which we may change any Gauss diagram (and hence any virtual knot) into any other, including in particular the unknotted diagram.
GLOBAL STRING IN LYRA GEOMETRY
Authors: RAHAMAN FAROOK
Published: July 2002

We present an approximate solution of the Einstein equations for the metric of a global string based on Lyra's geometry. The geodesic of a test particle is studied due to the gravitational field of the string. Finally, the angle of deficit has been calculated for the string solution.
A FUZZY RECURRENT ARTIFICIAL NEURAL NETWORK (FRANN) FOR PATTERN CLASSIFICATION
Authors: BROUWER ROELOF K.
Published: July 2002

This paper proposes a recurrent neural network of fuzzy units, which may be used for approximating a hetero-associative mapping and also for pattern classification. Since classification is concerned with set membership, and objects generally belong to sets to various degrees, a fuzzy network seems a natural for doing classification. In the network proposed here each fuzzy unit defines a fuzzy set. The fuzzy unit in the network determines the degree to which the input vector to the unit lies in that fuzzy set. The fuzzy unit may be compared to a perceptron in which case the input vector is compared to the weighting vector associated with the unit by taking the dot product. The resulting membership value in case of the fuzzy unit is compared to a threshold. Training of a fuzzy unit is based on an algorithm for solving linear inequalities similar to the method used for Ho-Kashyap recording. Training of the whole network is done by training each unit separately. The training algorithm is tested by trying the algorithm out on representations of letters of the alphabet with their noisy versions. The results obtained by the simulation are very promising.
QUALITY EVALUATION USING GEOMETRIC DISTANCE APPROACH
Authors: WANG FU-KWUN , HUBELE NORMA F.
Published: July 2002

Quantitatively assessing quality and using this assessment for competitive benchmarking and diagnostics of manufactured part failure are very important for continuous improvement in modern manufacturing industries. Process capability analysis often entails characterizing or assessing process specification or quality characteristics. When these quality characteristics are related, the analysis should be based on a multivariate statistical technique. A current problem in multivariate quality control is that there is no consensus about a methodology for assessing capability. Thus, the critical first step in instituting a multivariate control scheme is not well defined. While numerous authors have recently proposed alternative definitions of multivariate capability indices, those methods may not be practical in some cases. In this research, a new process control variable, geometric distance (GD), for assessing or evaluating the quality of manufactured product is developed and investigated for reducing dimensionality. The theoretical distribution of the geometric distance is investigated and a suitable performance metric of the multivariate process data is proposed. Finally, some real data are used to demonstrate the capability of the proposed method.
Ge/Ag(111): SURFACE ALLOY OF A SEMICONDUCTOR ON A METAL
Authors: OUGHADDOU H. , AUFRAY B. , GAY J. M.
Published: July 2002

We present one of the first experimental studies of the formation of an ordered surface alloy of a semiconductor, Ge, and a metal, Ag, with bulk tendency to phase separation. The kinetics of growth at room temperature as well as the surface segregation of Ge have been investigated for the (111) orientation using Auger Electron Spectroscopy (AES) and Low Electron Energy Diffraction (LEED).

The growth mode of Ge on Ag(111) is layer-by-layer like up to at least two layers. An unexpected ordered surface alloy forming a [Formula: see text] superstructure is observed during the growth at 1/3 germanium monolayer, followed by a p(7× 7) superstructure at one-monolayer coverage. The surface Ge segregation studied via both dissolution and segregation kinetics shows the particular stability of the ordered [Formula: see text] surface alloy.
EVALUATION OF RECONSTRUCTIONS OF THE UNSTABLE DISTAL ULNA
Authors: Tsuruta Toshiyuki , Rosales Roberto S. , Scheker Luis R.
Published: July 2002

Because the distal radioulnar joint (DRUJ) is a weight-bearing joint, surgical procedures treating DRUJ instability must be evaluated accordingly. Biomechanically, such procedures can be viewed from two approaches: One that preserves DRUJ biomechanics, which includes Groups A (intracapsular anatomical reconstruction) and B (ulnar shortening alone); and another that radically alters DRUJ biomechanics, which includes Groups C (tendon sling) and D (resection of ulnar head). This study compared the results of these two approaches.

Sixty-four patients having DRUJ surgery between 1984 and 1993 met the inclusion criteria of painful dorsal dynamic DRUJ instability, no DRUJ arthrosis, and no ulnocarpal impingement. However, only 25 returned for follow-up examination (Group A, 14 patients; B, 3; C, 2; D, 6). Grip strength, instability, pain, ROM, and satisfaction were scored.

The total scores of Groups A and B combined were significantly better than those of Groups C and D combined. Scores for pain with lifting weight and for instability in the combined Groups A and B were significantly better than those in the combined Groups C and D.

Although the number of patients who returned for follow-up was small, the significantly better scores achieved by the groups whose procedures preserved DRUJ biomechanics (anatomical reconstruction or ulnar shortening), indicate that these procedures may be the treatment of choice over the techniques that radically alter the DRUJ biomechanics (tendon slings or ulnar head resection).
FOLIATIONS ASSOCIATED TO REGULAR POISSON STRUCTURES
Authors: BERTELSON MÉLANIE
Published: July 2002

A regular Poisson manifold can be described as a foliated space carrying a tangentially symplectic form. Examples of foliations are produced here that are not induced by any Poisson structure although all the basic obstructions vanish.
DERIVING CHAOTIC DYNAMICAL SYSTEMS FROM ENERGY FUNCTIONALS
Authors: BRACKEN PAUL , GÓRA PAWEŁ , BOYARSKY ABRAHAM
Published: July 2002

Simple one-dimensional chaotic dynamical systems are derived by optimizing energy functionals. The Euler–Lagrange equation yields a nonlinear second-order differential equation whose solution yields a 2–1 map which admits an absolutely continuous invariant measure. The solutions of the differential equation are studied.
On discrete dynamical systems associated to games
Authors: Ahmed Elsayed , Hegazi Ahmed Sadek
Published: July 2002

Dynamical systems corresponding to continuous strategy games are introduced. The steady of the systems corresponding to continuous prisoner's dilemma, hawk-dove and rock-scissors-paper games are found and their stability are discussed. A discrete imitation equation is derived. Smale's payoff memory game formulation is generalized.
EXPLOITING AND NURTURING IN-HOUSE TECHNOLOGICAL CAPABILITIES: LESSONS FROM THE AEROSPACE INDUSTRY
Authors: PRENCIPE ANDREA
Published: July 2002

This paper identifies four major types of technological capabilities of firms developing multi-technology products: integrative, absorptive, coordinative, and generative. Using an in-depth case study of a high technology sub-system, the paper focuses on a firm's generative capabilities. The paper illustrates that a firm's generative capabilities enables it to (a) frame a particular problem, (b) enact an innovative vision, and (c) solve the problem by developing new manufacturing techniques. The triad frame-enact-solve is argued to be the primary feature of a firm's generative capability.
A modified random perturbation method for database security
Authors: Tendick Patrick , Matloff Norman
Published: July 2002

The random data perturbation (RDP) method of preserving the privacy of individual records in a statistical database is discussed. In particular, it is shown that if confidential attributes are allowed as query-defining variables, severe biases may result in responses to queries. It is also shown that even if query definition through confidential variables is
not
allowed, biases can still occur in responses to queries such as those involving proportions or counts. In either case, serious distortions may occur in user statistical analyses. A modified version of RDP is presented, in the form of a query adjustment procedure and specialized perturbation structure which will produce unbiased results.
The ASTOOT approach to testing object-oriented programs
Authors: Doong Roong-Ko , Frankl Phyllis G.
Published: July 2002

This article describes a new approach to the unit testing of object-oriented programs, a set of tools based on this approach, and two case studies. In this approach, each test case consists of a tuple of sequences of messages, along with tags indicating whether these sequences should put objects of the class under test into equivalent states and/or return objects that are in equivalent states. Tests are executed by sending the sequences to objects of the class under test, then invoking a user-supplied equivalence-checking mechanism. This approach allows for substantial automation of many aspects of testing, including test case generation, test driver generation, test execution, and test checking. Experimental prototypes of tools for test generation and test execution are described. The test generation tool requires the availability of an algebraic specification of the abstract data type being tested, but the test execution tool can be used when no formal specification is available. Using the test execution tools, case studies involving execution of tens of thousands of test cases, with various sequence lengths, parameters, and combinations of operations were performed. The relationships among likelihood of detecting an error and sequence length, range of parameters, and relative frequency of various operations were investigated for priority queue and sorted-list implementations having subtle errors. In each case, long sequences tended to be more likely to detect the error, provided that the range of parameters was sufficiently large and likelihood of detecting an error tended to increase up to a threshold value as the parameter range increased.
Vertical partitioning algorithms for database design
Authors: Navathe Shamkant , Ceri Stefano , Wiederhold Gio , Dou Jinglie
Published: July 2002

This paper addresses the vertical partitioning of a set of logical records or a relation into fragments. The rationale behind vertical partitioning is to produce fragments, groups of attribute columns, that “closely match” the requirements of transactions.

Vertical partitioning is applied in three contexts: a database stored on devices of a single type, a database stored in different memory levels, and a distributed database. In a two-level memory hierarchy, most transactions should be processed using the fragments in primary memory. In distributed databases, fragment allocation should maximize the amount of local transaction processing.

Fragments may be nonoverlapping or overlapping. A two-phase approach for the determination of fragments is proposed; in the first phase, the design is driven by empirical objective functions which do not require specific cost information. The second phase performs cost optimization by incorporating the knowledge of a specific application environment. The algorithms presented in this paper have been implemented, and examples of their actual use are shown.
Addendum to “Delta algorithms: an empirical analysis”
Authors: Hunt James J. , Tichy Walter F.
Published: July 2002

The authors supply machine configurations for experiments reported in “Delta Algorithms: An Empirical Analysis,” by Hunt et al. (ACM
Trans. Softw. Eng. Methodol.
7, 2 (Apr. 1998), pp. 192-214).
Efficient equivalence checking of multi-phase designs using phase abstraction and retiming
Authors: Hasteer G. , Mathur A. , Bannerjee P.
Published: July 2002

Equivalence checking of finite state machines (FSMs) traditionally assumes single phase machines where a single clock (implicit or explicit) synchronizes the state of the FSM. We extend the equivalence checking paradignm to FSMs with multi-phase clocks. Such designs are becoming increasingly popular in high performance microprocessors since they result in lower synchronization overhead. In addition, aggressive pipelining and the use of “sparse” encodings results in designs where the ratio of steady states to the total state space is very low. In this paper, we show that automatically transforming such designs to ones that have more “dense” encodings can result in significant benefits in using implicit BDD-based techniques for their verification. We explore two such techniques:
phase abstraction
and
retiming
and demonstrate their utility in the context of FSM equivalence checking. The main contributions of our work are:

—We show that a multi-phase FSM can be transformed to a functionally equivalent one phase FSM and this phase abstraction leads to significant improvement in the size of FSMs that can be checked for equivalence.

—We show that min-latch retiming preserves equivalence and can be performed efficiently in multi-phase designs, even when latch borrowing and discarding is allowed at the primary inputs and outputs.

—We demonstrate the utility of our approach on several controller FSMs from the industry.
Fifteen years ACM
Authors: Alt Franz L.
Published: July 2002

The development years of ACM, as recounted in 1962 by founding member and former president Franz L. Alt, depicts the players and progress of an organization committed to sharing computing knowledge and skills.
Remark on Algorithm 751
Authors: Renka Robert J.
Published: July 2002

The triangulation package TRIPACK has been revised to run more efficiently and to eliminate some potential errors. Also, a portable triangulation plotting routine was added.
Remark on Algorithm 752
Authors: Renka Robert J.
Published: July 2002

The triangulation-based scatterd-data fitting package SRFPACK was updated for (a) compatibility with a revised interface to the triangulation package TRIPACK, (b) the elimination of potential errors in the treatment of tension factors and in the extrapoltion procedure, and (c) the addition of a more accurate local gradient-estimation procedure and a simple but portable contour-plotting capability.
Evaluation of step directions in optimization algorithms
Authors: Davidon William C. , Nocedal Jorge
Published: July 2002

We present a method for comparing that part of optimization algorithms that chooses each step direction. It is an example of a general approach to algorithm evaluation in which one tests specific parts of the algorithm, rather than making overall evaluations on a set of standard test problems. Our testing procedure can he useful for developing new algorithms and for writing and evaluating optimization software.

We use the method to compare two versions of the conjugate gradient algorithm, and to compare these with an algorithm based on conic functions.
A relation-based language interpreter for a content addressable file store
Authors: Addis T. R.
Published: July 2002

The combination of the Content Addressable File Store (CAFS®; CAFS is a registered trademark of International Computers Limited) and an extension of relational analysis is described. This combination allows a simple and compact implementation of a database query and update language (FIDL). The language has one of the important properties of a “natural” language interface by using a “world model” derived from the relational analysis. The interpreter (FLIN) takes full advantage of the CAFS by employing a unique database storage technique which results in a fast response to both queries and updates.
Mathematical models of database degradation
Authors: Heyman Daniel P.
Published: July 2002

As data are updated, the initial physical structure of a database is changed and retrieval of specific pieces of data becomes more time consuming. This phenomenon is called database degradation. In this paper two models of database degradation are described. Each model refers to a different aspect of the problem.

It is assumed that transactions are statistically independent and either add, delete, or update data. The first model examines the time during which a block of data is filling up. The second model examines the overflows from a block of data, which essentially describes the buildup of disorganization. Analytical results are obtained for both models. In addition, several numerical examples are presented which show that the mean number of overflows grows approximately linearly with time. This approximation is used to devise a simple formula for the optimal time to reorganize a stochastically growing database.
On a partitioning problem
Authors: Yu C. T. , Siu M. K. , Lam K.
Published: July 2002

This paper investigates the problem of locating a set of “boundary points” of a large number of records. Conceptually, the boundary points partition the records into subsets of roughly the same number of elements, such that the key values of the records in one subset are all smaller or all larger than those of the records in another subset. We guess the locations of the boundary points by linear interpolation and check their accuracy by reading the key values of the records on one pass. This process is repeated until all boundary points are determined. Clearly, this problem can also be solved by performing an external tape sort. Both analytical and empirical results indicate that the number of passes required is small in comparison with that in an external tape sort. This kind of record partitioning may be of interest in setting up a statistical database system.
Boundary Contraction Solution of Laplace's Differential Equation
Authors: Milnes Harold W. , Potts Renfrey B.
Published: July 2002

A numerical method is introduced for solution of the Dirichlet problem within a circle. The data prescribed on the original boundary is used to compute the solution at mesh points on a concentric circle of slightly smaller radius, thereby defining another boundary value problem over the smaller circle. The solution for the entire region is obtained by successive contractions of the boundary in this way. Appropriate approximating relations are presented and their stability is discussed.
Note on the Practical Computation of Proper Values
Authors: Fike C. T.
Published: July 2002

It has been suggested by Householder [1] and by Householder and Bauer [2] that orthogonal similarity transformations of matrices are particularly stable with respect to the practical computation of proper values. It is the purpose of this note to examine this question and to demonstrate in terms of a “condition number” to be defined below a sense in which this conjecture is true.

Broadly speaking, any problem may be termed “ill-conditioned” for which the solution is acutely sensitive to slight variations in the parameters of the problem. Examples of ill-conditioning occur in many contexts. Computers are familiar with the phenomenon as it manifests itself, for example, in the study of matrix inversion. Since our purpose is to study the conditioning of matrices specifically for the proper value problem, it is convenient to have a nomenclature and notation which will avoid confusion with conditioning as it is used in other senses.
A Comparison of Machine Organizations by Their Performance of the Iterative Solution of Linear Equations
Authors: Gauss E. J.
Published: July 2002

It is shown that for a given problem different machine organizations will vary in time of solution over a nine-fold range. This holds even if it is assumed that the machines used the same arithmetic section and the same memory. The comparison is made on the basis of a typical problem—in this case the Kaczmarz iteration. An efficiency number is developed giving the relative solution time required by each organization. When the efficiency number of a single address machine is taken to be 1.0, the following numbers are obtained: four address machine, 1.25; single address machine with index registers, 2.5; complex organization, 9.
Multifunctional Circuits in Functional Canonical Form
Authors: Curtis H. Allen
Published: July 2002

The primary objective of this paper is to extend the results of the earlier paper, “A Functional Canonical Form”, in this journal [4]. This extension includes the application of the fundamental functional canonical form to multiple output circuits and the formulation of cost bounds on these circuits. It also includes the use of a multifunctional canonical form in the design of single output circuits.
Remarks on the Unitary Triangularization of a Nonsymmetric Matrix
Authors: Morrison David D.
Published: July 2002

In [1], A. Householder described a method for the unitary triangularization of a matrix. The formulas given there are valid for the real case. In this note we describe the modifications to handle the complex case and also point out a small modification in the real case which will improve the numerical accuracy of the method.

At first we are concerned with a complex vector space. The basic tool is the fact that if ‖
u
‖ = √2, then the matrix
I
-
uu
*
is unitary, as may be readily verified.

The following lemma is a modification of the one give in [1].

LEMMA.
Let a
≠ 0
be an arbitrary vector and let v be an arbitrary unit vector. Then there exists a vector u with
‖
u
‖ = √2
and a scalar ζ with
|
ζ
| = 1
such that
(
I
-
uu
*
)
a
=
ζ
‖
a
‖
v
. (1) PROOF: Letting
α
= ‖
a
‖ and
μ
=
u
*
a
, (1) may be written
a
-
αζv
=
μu
.

(2) Multiply by
a
*
gives
α
2
-
αζa
*
v
=
μa
*
u
= ‖
μ
‖
2
. (3) It follows that
ζa
*
v
is real. Assuming for the moment that
a
*
v
≠ 0, we write it in polar form
a
*
v
=
rw
,
r
> 0, ‖
w
‖ = 1. Then the fact that
ζrw
is real implies that
ζ
= ±
w
. (4) Substituting into (3) gives ‖
μ
‖
2
=
α
2
∓
αr
. (5) We now set, arbitrarily, arg (
μ
) = 0. Then
μ
= √
α
(
α
∓
r
). (6) Next, we select the negative sign in (4) in order to avoid the subtraction of two positive quantities in (6), since such a subtraction may give rise to numerical difficulties. Collecting the formulas, we see that the following sequence of computations will produce the required
u
and
ζ
:
α
= ‖
a
‖ (7)
r
= ‖
a
*
v
‖ (8)
ζ
= -
a
*
v
/
r
(9)
μ
= √
α
(
α
+
r
) (10)
u
= 1/
μ
(
a
-
ζαv
).

(11) The case
a
*
v
= 0 may be handled if, instead of using (9), we let
ζ
be an arbitrary number with ‖
ζ
‖ = 1. It is easily verified that the formulas thus modified will still work.

The computation requires 3 square roots to compare
α
,
r
, and
μ
. A slight modification [1] permits one to avoid the root required to compute
μ
. In the real case, no root is required to compute
r
.

Now consider the case of a real vector space. The formulas given [1] for this case are essentially the same as ours except that (8) is replaced by
r
=
a
*
v
, and (10) by
μ
= √
α
(
α
-
r
). If
μ
is computed this way and if
r
is positive and near
α
(as is the case when
v
is near
a
/
α
), cancellation of significant digits will occur. This difficulty, and the need for making a special case when
v
is exactly
a
/
α
, is avoided in the present set of formulas.
An Automatic Sequencing Procedure with Application to Parallel Programming
Authors: Schwartz Eugene S.
Published: July 2002

An automatic sequencing procedure for assigning sets of instructions to predesignated autonomous units of a multiprocessor is described. The procedure is based upon an assignment matrix developed from a precedence matrix. By associating a column vector whose elements are the operation time of each instruction set with the assignment matrix, numerical computation is made possible. A topological index, the precedence number, stating the position of each instruction set in relation to the last set in its path is contained in a second column vector. A transfer matrix in conjunction with an automatically derived path table is employed in a multipath program.

Six generalized rules are derived for the procedure which proceeds directly to a solution without obtaining and testing all permutations of the sets of instructions, and seeks to establish a sequence of operations to minimize the total operation time while satisfying all precedence restrictions. Since the procedure does not require looking at the last instruction set before releasing the first sets for assignment to units, computer processing may start after the first assignment period is completed with processing and subsequent sequencing taking place concurrently.

The procedure is readily adaptable to computer operation and automatic development of the assignment matrix is described. A flow chart of the procedure and its use for solution of a problem is presented. The solution obtained is guaranteed to be feasible although it is not necessarily unique. In the examples tested, an optimum or near optimum solution has been obtained. Computational experience with the procedure in complex problems is required to determine its effectiveness in such cases.
Statistical Complexity of Algorithms for Boolean Function Minimization
Authors: Mileto Franco , Putzolu Gianfranco
Published: July 2002

The first problem in a two level Boolean minimization is the determination of the prime
k
-cubes. This paper is concerned with the estimation of the statistical complexity of some well-known algorithms which solve this problem. Formulas are given for the average number of comparison operations among
k
-cubes occurring in Quine's method and in Mc-Cluskey's method; these quantities provide indications of the average execution time of computer programs based on the corresponding algorithms. Numerical values are given and commented on.

Formulas are also obtained for the variance of the number of
k
-cubes and the variance of the number of cubes of a Boolean function; in fact the calculation of these quantities is strictly related to that of the average number of comparison operations among
k
-cubes.

These variances give an idea of the probable error made by using the corresponding average values (obtained in a previous paper by the authors) to make forecasts. It turns out that this error is quite small.
Convergence Problems in Maehly's Second Method: Part II
Authors: Dunham Charles B.
Published: July 2002

Maehly's second method is a general algorithm for finding the best Chebyshev approximation to a continuous function on a finite interval. This paper examines the convergence properties of Maehly's second method, a modification, and the more commonly used algorithm of Remez, using both analytical and numerical results.
A Method for the Solution of Roots of a Nonlinear Equation and for Solution of the General Eigenvalue Problem
Authors: Barlow C. A. , Jones E. L.
Published: July 2002

A simple and yet powerful method of solving two of the more common numerical problems is heuristically derived and briefly discussed. The method makes possible the efficient solution of the zeros of a complex function, either transcendental or algebraic, of a complex variable. In addition, it is applicable to the computation of eigen values of a general matrix in which the parameter may appear in any elements of the matrix in a basically unrestricted way. The method is related to the classical secant and regula falsi methods for the finding of real zeros of a real function. Numerical examples of the method applied to several pathological matrices are presented.
An Abstract Machine for Symbolic Computation
Authors: Overheu D. L.
Published: July 2002

The design of an abstract machine with a recursive function programming language which avoids the predicate type of conditional is described. It is shown that trough the adoption of list processing techniques it has been possible to construct a simple simulator for the machine in FORTRAN. A program for the machine which causes it to perform symbolic differentiation with some algebraic manipulation of the expressions concerned is given as an example of the type of computations which may be performed.
Digital One-Third Octave Spectral Analysis
Authors: Negron C. D.
Published: July 2002

An economical approach is described for estimating power spectra from sampled data through the application of
Z
-transform theory. The method consists of computing a weighting sequence whose frequency characteristics approximate a one-third octave bandwidth filter, and applying these coefficients recursively to the digitized data record. Filtering is followed by a variance calculation and a division by the appropriate filter bandwidth. A specific example of power spectra computed in the usual manner (Fourier transformation of the autocorrelation function) and power spectra computed by the method in this paper demonstrates the practicability of the technique. The most significant advantage is the economical aspect. It is shown that owing to the variable bandwidth and the small number of filtering coefficients, the savings that may be realized by the employment of this technique, in lieu of the autocorrelation transformation approach, may be quite considerable, depending on the record length and the number of lag products.
Periodic Decomposition of Sequential Machines
Authors: Gill Arthur , Flexer J. Robert
Published: July 2002

Given a minimal sequential machine
M
and a positive integer
T
, it is desired to partition the state set of
M
into
T
classes, say
S
0
,
S
1
, · · ·,
S

T
-1

, such that all states in
S
1, under all possible inputs, pass into states in
S

i
+1 (mod
T
)

. If such a
T
-partition exists,
M
can be realized by means of periodically-varying logic, which often results in the saving of memory elements. The period of
M
is defined as the greatest common divisor of all cycle lengths of
M
—a quantity which can be readily evaluated since it depends only on a finite set of independent loops exhibited by the state graph.

The main result is that a
T
-partition exists for
M
if and only if
T
is a divisor of the period of
M
. For every such
T
, an algorithm is given for constructing the corresponding partition. If
M
is not required to be minimal, it is shown (constructively) that a
T
-partition exists for every
T
.
Solution of Integer Linear Programming Problems by Direct Search
Authors: Echols Robert E. , Cooper Leon
Published: July 2002

An approximate but fairly rapid method for solving integer linear programming problems is presented, which utilizes, in part, some of the philosophy of “direct search” methods. The method is divided into phases which can be applied in order and has the desirable characteristic that a best feasible solution is always available. Numerical results are presented for a number of test problems. Some possible extensions and improvements are also presented.
Structuring of Parallel Algorithms
Authors: Gilmore P. A.
Published: July 2002

The structuring of algorithms suitable for execution on parallel processors is discussed. Two examples of such algorithms are given. The first example exhibits a restructuring of Bellman's dynamic programming technique; the second presents a method of parsing MAD-type statements in parallel.
A Direct Proof of the Inherent Ambiguity of a Simple Context-Free Language
Authors: Maurer Herman A.
Published: July 2002

A direct and self-contained proof is given of the inherent ambiguity of the context-free language
L
= {

a
i
b
i
c
i

∣
i,j
> 1} ∪ {

a
i
b
i
c
i

∣
i,j
> 1}, which is the solution to an open problem pointed out by Ginsburg.
Lattice Approximations to the Minima of Functions of Several Variables
Authors: Berman Gerald
Published: July 2002

A computer-oriented method is developed for determining relative minima of functions of several variables. No derivatives (or approximations) are required and the process always converges to a relative minimum no matter which initial point is used. Numerical examples using test functions suggested in the literature are included to illustrate the effectiveness of the algorithms. Modifications can easily be incorporated which permit the inclusion of constraints or integer-valued variables.
Controllability of Nonlinear Sequential Networks
Authors: Mowle Frederic J.
Published: July 2002

A sequential network is said to be controllable if there exists at least one integer
k
such that it is possible to transition between any pair of arbitrary states (
S
α
,
S
β
) in exactly
k
steps. In this paper, necessary and sufficient conditions are given for a nonlinear sequential network to be controllable. Strong connectedness is a necessary condition for controllability. It is shown that the existence of two cycles
C
1
and
C
2
on a strongly connected sequential network, whose cycle lengths
L
1
and
L
2
are relatively prime, is both necessary and sufficient for controllability. Simple test procedures are also developed which determine if a sequential network is controllable and which determine the transition sequences.