bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of oesophageal manometry testing in a district general hospital
Authors: Ragunath K , Williams J G
Published: July 2002

Although several modalities are available to investigate oesophageal motility disorders, manometry is the gold standard. The procedure is increasingly available in district general hospitals but the clinical utility of this investigation in this setting remains unclear. The aim in this study was to evaluate the use and outcome of oesophageal manometry in a district general hospital. Data on 100 consecutive oesophageal manometry procedures were analysed, taking into account the referral pattern, indications, and results. The indications were gastro-oesophageal reflux disease (preoperative assessment before fundoplication) (58), dysphagia (28), chest pain (12), and epigastric pain (2). Diagnoses were made using predefined standard criteria and were as follows: normal (41), non-specific motility disorder (NSMD) (38), achalasia (15), diffuse oesophageal spasm (4), and scleroderma (2). Of the 58 patients who had undergone manometry as a preoperative assessment of oesophageal motility, 27 (47%) were abnormal. Twenty five (43%) had NSMD and two (3%) had achalasia. Forty eight of these preoperative cases were combined with 24 hour pH recording, which confirmed acid reflux in 35 (73%). The experience reported here reflects the published evidence that the use of manometry is changing. It is now more commonly used for assessment before antireflux surgery and for dysphagia, and the use in the assessment of chest pain is declining. The findings confirm the importance of eliminating achalasia before inappropriate antireflux surgery.
Inhibition de la corrosion de l'alliage d'aluminium 6063 au moyen de composés inorganiques dans une solution de chlorure de sodium à 3 %
Authors: Bazzi L , Salghi R , Zine E , Issami S El , Kertit S , Hammouti B
Published: July 2002

Some inorganic compounds have been tested as corrosion inhibitors for 6063 aluminium alloy in 3% NaCl by electrochemical and metalographic methods. The compounds were MoO42, CrO42, NO2 oxo-anions and Li+ and Mg2+ metallic cations. Results obtained show that these compounds inhibited corrosion of 6063 aluminium alloy, and that the Li+ cations were the best inhibitors. The difference between pitting potential and corrosion potential increase by increasing the concentration of Li+. The maximum inhibition efficiency (E% = 85%) was attained at 5 × 103 M. Increasing temperature from 25 to 55°C improve corrosion resistance of 6063 aluminium alloy in the absence of Li+. However, in the presence of these cations, E% decreased at elevated temperature.Key words: corrosion, inhibition, inorganic compounds, 6063 aluminium alloy, 3% NaCl.
Évolution de la structure diamétrale et production ligneuse des pessières noires issues de coupe et de feu
Authors: Lussier Jean-Martin , Morin Hubert , Gagnon Réjean
Published: July 2002

The widespread use of careful logging in the province of Quebec raises many questions about the effects of this practice on the structure and productivity of boreal black spruce (Picea mariana (Mill.) BSP) stands compared with fire-origin stands that are currently being harvested. The objective of this study is to describe and compare the evolution pattern of the diameter structure of stands originating from fire or logging dating back to the first half of the 20th century. The dendrochronological approach allowed the reconstitution of the dynamics of 40- to 96-year-old stands. Second-growth stands differ from fire-origin stands by their highly hierarchized initial structure. After the recruitment period, the degree of hierarchy of the structure of second-growth and fire-origin stands is comparable. After logging, the diameter structure of black spruce stands keeps a higher skewness index than that of stands originating from fire. For both stand types the skewness decreases or remains constant with time, which invalidates the model proposed by Mohler et al. (C.L. Mohler, P.L. Marks, and D.G. Sprugel. 1978. J. Ecol. 66: 599614). This observation questions the existence of a strong asymmetric competition among trees in black spruce stands. Results indicate that the yield of black spruce stands originating from clearcuts from the early 20th century is higher than or equal to fire-origin stands mainly because (i) basal area was maintained to levels higher than or equal to fire-origin stands and (ii) most advanced growth was taller that 1 m at the time of logging.
CONVOLUTED GENERALIZED WHITE NOISE, SCHWINGER FUNCTIONS AND THEIR ANALYTIC CONTINUATION TO WIGHTMAN FUNCTIONS
Authors: ALBEVERIO SERGIO , GOTTSCHALK HANNO , WU JIANG-LUN
Published: July 2002

We construct Euclidean random fields X over [Formula: see text] by convoluting generalized white noise F with some integral kernels G, as X=G*F. We study properties of Schwinger (or moment) functions of X. In particular, we give a general equivalent formulation of the cluster property in terms of truncated Schwinger functions which we then apply to the above fields. We present a partial negative result on the reflection positivity of convoluted generalized white noise.

Furthermore, by representing the kernels Gα of the pseudo-differential operators [Formula: see text] for α∈(0, 1) and m0>0 as Laplace transforms we perform the analytic continuation of the (truncated) Schwinger functions of X=Gα*F, obtaining the corresponding (truncated) Wightman distributions on Minkowski space which satisfy the relativistic postulates on invariance, spectral property, locality and cluster property.

Finally we give some remarks on scattering theory for these models.
QUANTUM MECHANICS IN AFC*-SYSTEMS
Authors: HIAI FUMIO , PETZ DÉNES
Published: July 2002

Motivated from the chemical potential theory, we study quantum statistical thermodynamics in AF C*-systems generalizing usual one-dimensional quantum lattice systems. Our systems are C*-algebras [Formula: see text] which have a localization [Formula: see text] of finite-dimensional subalgebras indexed by finite intervals of Z and an automorphism γ acting as a right shift on the localization. Model examples are supplied from derived towers (string algebras) for type II1 factor-subfactor pairs. Given a (γ-invariant) interaction and a specific tracial state, we formulate the Gibbs conditions and the variational principle for (γ-invariant) states on [Formula: see text], and investigate the relationship among these conditions and the KMS condition for the time evolution generated by the interaction. Special attention is paid to C*-systems of gauge invariance (typical model in the chemical potential theory) and to C*-systems considered as quantum random walks on discrete groups. The CNT-dynamical entropy for the shift automorphism γ is also discussed.
PATTERN RECOGNITION WITH STOCHASTIC RESONANCE IN A GENERIC NEURAL NETWORK
Authors: TAN Z. , ALI M. K.
Published: July 2002

We discuss stochastic resonance in associative memory with a canonical neural network model that describes the generic behavior of a large family of dynamical systems near bifurcation. Our result shows that stochastic resonance helps memory association. The relationship between stochastic resonance, associative memory, storage load, history of memory and initial states are studied. In intelligent systems like neural networks, it is likely that stochastic resonance combined with synaptic information enhances memory recalls.
PATTERN OF THE APPROXIMATE MASS DEGENERACY OF MAJORANA NEUTRINOS
Authors: MA ERNEST
Published: July 2002

In view of the recently reported evidence for a nonzero Majorana mass of the electron neutrino, together with the established phenomena of atmospheric and solar neutrino oscillations, the case of three nearly mass-degenerate Majorana neutrinos is now an interesting possibility. We show in this paper how a natural pattern of symmetry breaking in the recently proposed A4 model of Majorana neutrino masses can accommodate the data on neutrino oscillations, resulting in the predictions sin 2 2θ atm = 1 and sin 2 2θ sol = 2/3.
TESTS OF THE STANDARD MODEL USING MUON POLARIZATION ASYMMETRIES IN KAON DECAYS
Authors: DIWAN MILIND V. , MA HONG
Published: July 2002

We have examined the physics and the experimental feasibility of studying various kaon decay processes in which the polarization of a muon in the final state is measured. Valuable information on CP violation, the quark mixing (CKM) matrix, and new physics can be obtained from such measurements. We have considered muon polarization in KL→μ+μ- and K→πμ+μ- decays. Although the effects are small, or difficult to measure because of the small branching ratios involved, these studies could provide clean measurements of the CKM parameters. The experimental difficulty appears comparable to the observation of [Formula: see text]. New sources of physics, involving nonstandard CP violation, could produce effects observable in these measurements. Limits from new results on the neutron and electron electric dipole moment, and [Formula: see text] in neutral kaon decays, do not eliminate certain models that could contribute to the signal. A detailed examination of muon polarization out of the decay plane in K+→μ+π0ν and K+→μ+νγ decays also appears to be of interest. With current kaon beams and detector techniques, it is possible to measure the T-violating polarization for K+→μ+π0ν and with uncertainties approaching ~10-4. This level of sensitivity would provide an interesting probe of new physics.
EXACT SYMMETRIES REALIZED ON THE RG FLOW
Authors: IGARASHI Y. , ITOH K. , SO H.
Published: July 2002

We show that the BRS symmetry is present even with the finite IR cutoff in the Wilsonian RG approach. Based on the antifield formalism, we explain how the symmetry is realized on the RG flow.
MINIMAL SUPERSTRING STANDARD MODEL: A REVIEW
Authors: Cleaver Gerald B.
Published: July 2002

I review a heterotic-string solution in which the observable sector effective field theory just below the string scale reduces to that of the MSSM, with the standard observable gauge group being just SU(3)C × SU(2)L × U(1)Y and the SU(3)C × SU(2)L × U(1)Y - charged spectrum of the observable sector consisting solely of the MSSM spectrum. Associated with this model is a set of distinct flat directions of vacuum expectation values (VEVs) of fields that all produce solely the MSSM spectrum. Some of these directions only involve VEVs of non-Abelian singlet fields while others also contain VEVs of non-Abelian charged fields. The phenomenology of theses flat directions is summarized.
REAL TIME NONEQUILIBRIUM DYNAMICS OF QUANTUM PLASMAS: QUANTUM KINETICS AND THE DYNAMICAL RENORMALIZATION GROUP
Authors: de VEGA H. J.
Published: July 2002

We implement the dynamical renormalization group (DRG) using the hard thermal loop (HTL) approximation for the real-time nonequilibrium dynamics in hot plasmas. The focus is on the study of the relaxation of gauge and fermionic mean fields and on the quantum kinetics of the photon and fermion distribution functions. As a concrete physical prediction, we find that for a QGP of temperature T~200 MeV and lifetime 10≤t≤ 50 fm /c there is a new contribution to the hard (k~T) photon production form off-shell bremsstrahlung (q→qγ and [Formula: see text] at just O(α) that grows logarithmically in time and is comparable to the known on-shell Compton scattering and pair annihilation at O(ααs).
MEASUREMENTS OF THE NORMAL AND SHAPE DEPENDENT CASIMIR FORCES USING AN ATOMIC FORCE MICROSCOPE
Authors: CHEN F. , HARRIS B. W. , ROY A. , MOHIDEEN U.
Published: July 2002

The precision instrumental developments and the modern unification theories using compact dimensions have motivated a resurgence in the field of Casimir force measurements. Here, after a brief discussion of the history of Casimir force measurements, the experimental results of Casimir force measurements using an Atomic Force Microscope will be presented. Precision measurements of the normal Casimir force, demonstration of the shape dependent Casimir force and the lateral Casimir force will be presented.
CORRELATION BETWEEN PLASMA AND TEMPERATURE CORRECTIONS TO THE CASIMIR FORCE
Authors: GENET CYRIAQUE , LAMBRECHT ASTRID , REYNAUD SERGE
Published: July 2002

When comparing experimental results with theoretical predictions of the Casimir force, the accuracy of the theory is as important as the precision of experiments. Here we evaluate the Casimir force when finite conductivity of the reflectors and finite temperature are simultaneously taken into account. We show that these two corrections are correlated, i.e. that they can not, in principle, be evaluated separately and simply multiplied. We estimate the correlation factor which measures the deviation from this common approximation. We focus our attention on the case of smooth and plane plates with a metallic optical response modeled by a plasma model.
APPLICATION OF SYMBOL-OPERATOR TECHNIQUE
Authors: BANIN A. T. , PLETNEV N. G.
Published: July 2002

In the present talk we briefly demonstrate an elegant and effective technique for calculation of the trace expansion in the derivatives of background fields. One of main advantages of the technique is manifestly (super)symmetrical and gauge invariant form of expressions on all stages of calculations. Other advantage is the universality of the calculation method. It shows itself to be good for calculation of one-loop effective action in several well-known models and new results in supersymmetrical models has already been found.
L-DEPENDENCE OF PARTICLE RADIATION IN MAGNETIC-SOLENOID FIELD AS AHARONOV-BOHM EFFECT
Authors: BAGROV V. G. , GITMAN D. M. , TLYACHEV V. B.
Published: July 2002

Aharonov-Bohm solenoid changes the energy spectrum of charge particles in pure magnetic field. In particular, the degeneracy with respect to azimuthal quantum number l is partially lifted. In turn, this complicates the radiation spectrum of a charged particle in magnetic field in the presence of the solenoid (Aharonov-Bohm effect). In particular, the degeneracy of the radiation intensity with respect to the azimuthal quantum number is lifted completely. In the present work we study l-dependence (induced by Aharonov-Bohm solenoid) of synchrotron radiation intensity in semiclassical approximation.
IMPLICIT DENSITY FUNCTIONALS FOR THE EXCHANGE-CORRELATION ENERGY: DESCRIPTION OF VAN DER WAALS BONDS
Authors: ENGEL E. , BONETTI A. FACCO
Published: July 2002

The energy surface of the Helium dimer, as a prototype of a van der Waals bond molecule, is investigated within the framework of density functional theory. For the exchange-correlation energy an implicit density functional, depending on the Kohn-Sham orbitals, is applied in which exchange is treated exactly, while correlation is approximated by the lowest order contribution obtained by Kohn-Sham perturbation theory. The resulting energy surface is in fair quantitative agreement with highly accurate empirical data over the complete range of internuclear separations, demonstrating that the concept of orbital-dependent functionals can provide a seamless description of dispersion forces. As selfconsistent calculations with implicit functionals on the basis of the optimized potential method are rather time-consuming, the correlation part of the exchange-correlation functional is evaluated perturbatively in the Helium dimer calculations. However , we also present an approximate scheme for the evaluation of the corresponding correlation potential.
ROTATING FERMIONS IN TWO DIMENSIONS: A THOMAS–FERMI APPROACH
Authors: GHOSH SANKALPA , MURTHY M. V. N. , SINHA SUBHASIS
Published: July 2002

Properties of confined mesoscopic systems have been extensively studied numerically over recent years. We discuss an analytical approach to the study of finite rotating fermionic systems in two dimension. We first construct the energy functional for a finite fermionic system within the Thomas–Fermi approximation in two dimensions. We show that for specific interactions the problem may be exactly solved. We derive analytical expressions for the density, the critical size as well as the ground state energy of such systems in a given angular momentum sector.
EXCITONIC BANDS IN THE PHOTOCONDUCTIVITY SPECTRA OF SOME ORGANIC-INORGANIC HYBRID COMPOUNDS BASED ON METAL HALIDE UNITS
Authors: PAPAVASSILIOU G. C. , MOUSDIS G. A. , KOUTSELAS I. B. , PAPAIOANNOU G. J.
Published: July 2002

The photoconductivity (PC) spectra of the compounds CH3NH3PbI3 , [CH3NH3][CH3C6H4CH2NH3]2Pb2I7 , [CH3C6H4CH2NH3]2PbI4 , [H2NC(I)=NH2]3PbI5 as well as the spectra of similar compounds bases on C10H21SC(NH2)2 , H3N(CH2)6NH3 , C14H9CH2SC(NH2)2 , SnI4 , PbClxI4-x and PbBrxI4-x are described. The position, intensity and shape of the PC bands depend on the dimensionality (or size) of the inorganic network as well as on the nature of metal halide and the organic groups. Excitonic features are discussed.
EFFECTIVE HARD-SPHERE DIAMETERS IN SIMPLE CLASSICAL FLUIDS AND APPLICATIONS TO DOUBLE YUKAWA POTENTIAL
Authors: OSMAN S. M. , ALI I.
Published: July 2002

We present an accurate method to determine the effective hard-sphere diameters for systems interacting via an arbitrary continuous potential within the Gibbs–Bogoliaubov variational approach. As a specific application we consider the double Yukawa (DY) model potential with potential parameters fitted such that they reproduce the Lennard–Jones potential. To assess the accuracy of the theory, we give a direct comparison of the thermodynamic properties with simulation results and with experimental data for Argon. Also, comparisons with previous models are made.
PERSISTENT CURRENTS IN MESOSCOPIC RINGS AND BOUNDARY CONFORMAL FIELD THEORY
Authors: JAIMUNGAL S. , AMIN M. H. S. , ROSE G.
Published: July 2002

A tight-binding model of electron dynamics in mesoscopic normal rings is studied using boundary conformal field theory. The partition function is calculated in the low energy limit and the persistent current generated as a function of an external magnetic flux threading the ring is found. We study the cases where there are defects and electron–electron interactions separately. The same temperature scaling for the persistent current is found in each case and the functional form can be fitted, with a high degree of accuracy, to experimental data.
TRANSITION FROM SHORT-RANGE TO LONG-RANGE ORDER IN LEAD-BISMUTHATE OXIDE GLASS MATRICES
Authors: SIMON V. , POP R. , SIMON S.
Published: July 2002

Glass transition and nucleation temperatures as well as densities and molar volumes of x Bi 2 O 3·y PbO (0.5≤x/y≤4) are reported. The glass transition temperature and molar volume are further analysed in terms of structural data. The obtained results indicate the occurrence of structural changes from short range to long range order induced by the heat treatment applied at 550°C, as per DTA results. These changes depend on the x/y ratio between Bi 2 O 3 and PbO content. The compositional variation of the molar volume of untreated and heat-treated samples are evidences that both Bi 2 O 3 and PbO play the role of network formers.
SYNTHESIS AND CHARACTERIZATION OF Au/ZnO NANOCOMPOSITES
Authors: PAL U. , AGUILA E. , VAZQUEZ O. , KOSHIZAKI N. , SASAKI T. , TERAUCHI S.
Published: July 2002

Au/ZnO nanocomposite thin films were prepared by co-sputtering of ZnO and gold. The Au content in the films was varied by varying the length of gold wires on the ZnO target. Depending upon the Au content in the films, the Au nanoparticles of different average size values were formed in the ZnO matrix. The composite films were annealed at different temperatures to study the evolution of Au particles and the subsequent change in their optical properties. With the increase of Au content in the films, the size of the nanometric Au particles decreased but increased with the increase of annealing temperature.
CURVATURE IN DIGITAL 2D IMAGES
Authors: KOVALEVSKY VLADIMIR
Published: July 2002

The paper presents an analysis of sources of errors when estimating derivatives of numerical or noisy functions. A method of minimizing the errors is suggested. When being applied to the estimation of the curvature of digital curves, the analysis shows that under the conditions typical for digital image processing the curvature can rarely be estimated with a precision higher than 50%. Ways of overcoming the difficulties are discussed and a new method for estimating the curvature is suggested and investigated as to its precision. The method is based on specifying boundaries of regions in gray value images with subpixel precision. The method has an essentially higher precision than the known methods.
DELAYED FEEDBACK CONTROL WITH A MINIMAL-ORDER OBSERVER FOR STABILIZATION OF CHAOTIC DISCRETE-TIME SYSTEMS
Authors: YAMAMOTO SHIGERU , HINO TORU , USHIO TOSHIMITSU
Published: July 2002

Delayed feedback control (DFC) is a powerful method for stabilizing unstable periodic orbits embedded in chaotic attractors, which uses a small control input fed by the difference between the current state and the delayed state. One drawback of the DFC is known as the odd number limitation; that is, DFC can never stabilize a target unstable fixed point of a chaotic discrete-time system, if the Jacobian of its linearized system around the unstable fixed point has an odd number of real eigenvalues greater than unity. To overcome it, in this paper we propose a dynamic DFC method using output measurements of the chaotic systems. The proposed dynamic DFC is realized by using an output feedback controller with a minimal-order observer that has the least order for estimating the state of the chaotic system from the control input and the output measurements. In addition to the design procedure of the controller, we derive a necessary and sufficient condition for the existence of such controllers.
FROM BOUNDARY VALUE PROBLEMS TO DIFFERENCE EQUATIONS: A METHOD OF INVESTIGATION OF CHAOTIC VIBRATIONS
Authors: ROMANENKO E. YU. , SHARKOVSKY A. N.
Published: July 2002

Among evolutionary boundary value problems for partial differential equations, there is a wide class of problems reducible to difference, differential-difference and other relevant equations. Of especial promise for investigation are problems that reduce to difference equations with continuous argument. Such problems, even in their simplest form, may exhibit solutions with extremely complicated long-time behavior to the extent of possessing evolutions that are indistinguishable from random ones when time is large. It is owing to the reduction to a difference equation followed by the employment of the properties of the one-dimensional map associated with the difference equation, that, it is in many cases possible to establish mathematical mechanisms for one or other type of dynamical behavior of solutions. The paper presents the overall picture in the study of boundary value problems reducible to difference equations (on which the authors have a direct bearing over the last ten years) and demonstrates with several simplest examples the potentialities that such a reduction opens up.
THREE-FREQUENCY RESONANCES IN DYNAMICAL SYSTEMS
Authors: CALVO OSCAR , CARTWRIGHT JULYAN H. E. , GONZÁLEZ DIEGO L. , PIRO ORESTE , ROSSO OSVALDO A.
Published: July 2002

We investigate numerically and experimentally dynamical systems having three interacting frequencies: a discrete mapping (a circle map), an exactly solvable model (a system of coupled ordinary differential equations), and an experimental device (an electronic oscillator). We compare the hierarchies of three-frequency resonances we find in each of these systems. All three show similar qualitative behaviour, suggesting the existence of generic features in the parameter-space organization of three-frequency resonances.
SYNCHRONIZATION IN A RING OF PULSATING OSCILLATORS WITH BIDIRECTIONAL COUPLINGS
Authors: DÍAZ-GUILERA ALBERT , PEREZ-VICENTE CONRAD J. , ARENAS ALEX
Published: July 2002

We study this dynamical behavior of an ensemble of oscillators interacting through short-range bidirectional pluses. The geometry is 1D with periodic boundary conditions. Our interest is twofold — to explore the conditions required to fully reach synchronization and to investigate the time needed to peach such a state. We present both theoretical and numerical results.
THE MINIMUM OF KNOT ENERGY FUNCTIONS
Authors: Dai Xingde , Diao Yuanan
Published: July 2002

In this paper we discuss some fundamental issues regarding knot energy functions. These include the existence of minimum values of energy functions of smooth knots and energy functions of polygonal knots within a knot type, the convergence of these minimum values in the case of polygonal knot energy and the convergence of the corresponding polygons where these minimum values are attained. When the polygonal knot energy is derived from a smooth knot energy, will the minimal polygonal knot energies converge to the infimum of the smooth knot energy? Do the corresponding polygons converge to a smooth knot at which the smooth energy achieves its minimal value? We show that one cannot expect these to be true in general and outline certain conditions that would ensure a positive answer to some of the above questions.
HAMILTONIAN DIAGONALIZATION FOR A NONCONFORMAL SCALAR FIELD IN AN ISOTROPIC GRAVITATIONAL BACKGROUND
Authors: BEZERRA V. B. , MOSTEPANENKO V. M. , ROMERO C.
Published: July 2002

The metrical Hamiltonian is investigated for a nonconformal scalar field with arbitrary coupling in a nonstationary spatially homogeneous isotropic gravitational field. It is shown that this Hamiltonian may be diagonalized by the canonical Bogoliubov transformations of creation-annihilation operators only for the values of coupling coefficient 0 ≤ ξ ≤ 1/6. The quasienergy of quasiparticles diagonalizing the Hamiltonian is shown to differ for the nonconformal case from the effective oscillator frequency of the wave equation. Different definitions of the initial vacuum state for the nonconformal scalar field are discussed.
A PRAGMATIC APPROACH TO MODELING MORPHOGENESIS
Authors: MARZEC CHRISTOPHER J.
Published: July 2002

The mathematical modeling of biological morphogenesis processes is considered. Emphasis is placed throughout on the lessons of experience in modeling three-dimensional forms that evolve in time. The qualitative requirements of a model, the general components of a dynamic system, and the products of a morphogenesis modeling program are discussed. Examples are drawn frequently from phyllotaxis.
TREE BASED INDEXES VERSUS BITMAP INDEXES: A PERFORMANCE STUDY
Authors: JÜRGERNS MARCUS , LENZ HANS-J.
Published: July 2002

Data warehouses are used to store large amounts of data which is often used for On-Line Analytical Processing (OLAP). Short response times are essential for on-line decision support. Common approaches to reach this goal in read-mostly environments are the precomputation of materialized views and the use of index structures. This paper focuses on the use of index structures for supporting fast access to data. The performance of index structures depends on many different parameters. Here, we focus on a set of nine parameters. Two approaches are presented to support the decision making process which index structure should be applied. The first approach is based on classification trees. The second approach uses an aggregation and scatter diagram method. Both approaches are applied to four distinct index structures: a tree-based index structure without aggregated data, a tree-based index structure with aggregated data and two bitmap index structures. This paper presents results of the comparison with both approaches.
GULFSTREAM AEROSPACE CORPORATION — PENETRATING ASIA'S CORPORATE JET MARKET
Authors: Lwin May , Wirtz Jochen
Published: July 2002

In January 2000, Gulfstream was reviewing its plan to enter the East and Southeast Asian markets. Gulfstream Aerospace Corporation was well known for reliability, performance and innovative features of its business jets. Its existing clientele came mainly from North and South America and Europe. With the Asian markets recovering from an economic crisis, Gulfstream wanted to solidly position itself as the market leader in Asia. The company's major concern was how to sell the idea of travelling in corporate-owned business jets rather than in first or business class in commercial planes. Essentially, Gulfstream needed to devise a marketing strategy that would allow it to capture a leadership position in the Asian market. The case provides an understanding of the unique features of business buyer behavior and the unique aspects of industrial marketing.
COMPOSITE INDEX PREDICTION
Authors: ZEMKE STEFAN S.
Published: July 2002

Bagging different predictors for an exchange index can provide higher returns than by only using a single strategy.
OPTION PRICING AND HEDGING WITH TEMPORAL CORRELATIONS
Authors: CORNALBA LORENZO , BOUCHAUD JEAN-PHILIPPE , POTTERS MARC
Published: July 2002

We consider the problem of option pricing and hedging when stock returns are correlated in time. Within a quadratic-risk minimisation scheme with history-dependent hedging strategies, we obtain a general formula, valid for weakly correlated non-Gaussian processes. We show that for Gaussian price increments, the correlations are irrelevant, and the Black-Scholes formula holds with the volatility of the price increments calculated on the scale of the re-hedging. For non-Gaussian processes, further non trivial corrections to the "smile" are brought about by the correlations, even when the hedge is the Black-Scholes Δ-hedge. We introduce a compact notation which eases the computations and could be of use to deal with more complicated models.
KNIGHT'S MODEL, ITS AUTOMORPHISM GROUP, AND CHARACTERIZING THE UNCOUNTABLE CARDINALS
Authors: HJORTH GREG
Published: July 2002

We show that every ℵα(α<ω1) can be characterized by the Scott sentence of some countable model; moreover there is a countable structure whose Scott sentence characterizes ℵ1but whose automorphism group fails the topological Vaught conjecture on analytic sets.

We obtain some partial information on Ulm type dichotomy theorems for the automorphism group of Knight's model.
ANALYTICAL MODEL FOR PREDICTING NONLINEAR RANDOM AND SNAP-THROUGH RESPONSE OF BUCKLED PLATES
Authors: POON W. Y. , NG C. F. , LEE Y. Y.
Published: July 2002

This paper presents a simplified model for predicting the nonlinear random response of flat and buckled plates. Based on a single mode representation of vibration response, r.m.s. values of the strain response to broadband excitation are evaluated for different static buckled configurations using the equivalent linearization technique. The dynamic effects on the overall strain response due to instability motion of snap-through are included. Parametric studies are performed in which the influences of the clamped and simply-supported boundaries, aspect ratio of the plate, thickness and length of the plate are considered. Using a simple single-model formula, the results of dynamic buckling motion were compared with finite-element models as well as experimental results. The comparisons between analytical results and experimental results help to assess the accuracy of the theory and the conditions under which deviations from the theory due to effects of imperfection and higher modes are significant. It is found that the theoretical model is useful for design and checking of computer results for curved plates in a slightly deflected form (initial deflection less than twice the thickness of plate) and the prediction accuracy on nonlinear analysis is higher than existing design formula based on linear response.
METHODOLOGIES FOR SUSTAINABILITY IMPACT ASSESSMENTS OF PROPOSALS FOR NEW TRADE AGREEMENTS
Authors: LEE NORMAN , KIRKPATRICK COLIN
Published: July 2002

In the build-up to the World Trade Organisation (WTO) Ministerial Meeting in November 1999, and its aftermath, considerable interest has been expressed in the likely economic, environmental and social effects of trade liberalisation on sustainable development. This article explores the methodological challenges which are faced when undertaking a sustainability impact assessment (SIA) at different stages in multilateral trade negotiations. The article draws upon the authors' experiences when undertaking a preliminary SIA in advance of the proposed WTO New Round, and explores how the methodology used might need to be elaborated for use in later stages of the negotiating process. Given existing methodological deficiencies and data shortages, it points to some of the dangers in being over-ambitious and proposes, as an interim solution, the more detailed and specific application of "simpler" methods already in use.
The partition model: a deductive database model
Authors: Spyratos Nicolas
Published: July 2002

We present a new database model in which each attribute is modeled by a family of disjoint subsets of an underlying population of objects. Such a family is called a partitioning, and the set of all partitionings is turned into a lattice by appropriately defining product and sum. A database is seen as a function from a sublattice into the lattice of partitionings. The model combines the following features:

(1) syntactic simplicity (essentially that of the relational model),

(2) powerful means for the specification of semantic information (in the form of lattice equations), and

(3) deductive capability (essentially that of set theory).

The relational model of data and the basic constructs of semantic modeling can be embedded into our model in a simple and straightforward manner.
Automatic deduction of temporal information
Authors: Maiocchi Roberto , Pernici Barbara , Barbic Federico
Published: July 2002

In many computer-based applications, temporal information has to be stored, retrieved, and related to other temporal information. Several time models have been proposed to manage temporal knowledge in the fields of conceptual modeling, database systems, and artificial intelligence.

In this paper we present TSOS, a system for reasoning about time that can be integrated as a time expert in environments designed for broader problem-solving domains. The main intended goal of TSOS is to allow a user to infer further information on the temporal data stored in the database through a set of deduction rules handling various aspects of time. For this purpose, TSOS provides the capability of answering queries about the temporal specifications it has in its temporal database.

Distinctive time-modeling features of TSOS are the introduction of
temporal modalitites
, i.e., the possibility of specifying if a piece of information is always true within a time interval, or if it is only sometimes true, and the capability of answering about the possibility and the necessity of the validity of some information at a given time, the association of temporal knowledge both to
instances of data
and to
types of data
, and the development of a
time calculus
for reasoning on temporal data. Another relevant feature of TSOS is the capability to reason about temporal data specified at different time granularities.
Modularization techniques for active rules design
Authors: Baralis Elena , Ceri Stefano , Paraboschi Stefano
Published: July 2002

Active database systems can be used to establish and enforce data management policies. A large amount of the semantics that normally needs to be coded in application programs can be abstracted and assigned to active rules. This trend is sometimes called “knowledge independence” a nice consequence of achieving full knowledge independence is that data management policies can then effectively evolve just by modifying rules instead of application programs. Active rules, however, may be quite complex to understand and manage: rules react to arbitrary event sequences, they trigger each other, and sometimes the outcome of rule processing may depend on the order in which events occur or rules are scheduled. Although reasoning on a large collection of rules is very difficult, the task becomes more manageable when the rules are few. Therefore, we are convinced that modularization, similar to what happens in any software development process, is the key principle for designing active rules; however, this important notion has not been addressed so far. This article introduces a modularization technique for active rules called stratification; it presents a theory of stratification and indicates how stratification can be practically applied. The emphasis of this article is on providing a solution to a very concrete and practical problem; therefore, our approach is illustrated by several examples.
A graphical environment for the design of concurrent real-time systems
Authors: Moser L. E. , Ramakrishna Y. S. , Kutty G. , Melliar-Smith P. M. , Dillon L. K.
Published: July 2002

Concurrent real-time systems are among the most difficult systems to design because of the many possible interleavings of events and because of the timing requirements that must be satisfied. We have developed a graphical environment based on Real-Time Graphical Interval Logic (RTGIL) for specifying and reasoning about the designs of concurrent real-time systems. Specifications in the logic have an intuitive graphical representation that resembles the timing diagrams drawn by software and hardware engineers, with real-time constraints that bound the durations of intervals. The syntax-directed editor of the RTGIL environment enables the user to compose and edit graphical formulas on a workstation display; the automated theorem prover mechanically checks the validity of proofs in the logic; and the database and proof manager tracks proof dependencies and allows formulas to be stored and retrieved. This article describes the logic, methodology, and tools that comprise the prototype RTGIL environment and illustrates the use of the environment with an example application.
A tight bound for black and white pebbles on the pyramid
Authors: Klawe Maria M.
Published: July 2002

Lengauer and Tarjan proved that the number of black and white pebbles needed to pebble the root of a tree is at least half the number of black pebbles needed to pebble the root. This result is extended to a larger class of acyclic directed graphs including pyramid graphs.
A multilevel approach to intelligent information filtering
Authors: Mostafa J. , Mukhopadhyay S. , Palakal M. , Lam W.
Published: July 2002

In information-filtering environments, uncertainties associated with changing interests of the user and the dynamic document stream must be handled efficiently. In this article, a filtering model is proposed that decomposes the overall task into subsystem functionalities and highlights the need for multiple adaptation techniques to cope with uncertainties. A filtering system, SIFTER, has been implemented based on the model, using established techniques in information retrieval and artificial intelligence. These techniques include document representation by a vector-space model, document classification by unsupervised learning, and user modeling by reinforcement learning. The system can filter information based on content and a user's specific interests. The user's interests are automatically learned with only limited user intervention in the form of optional relevance feedback for documents. We also describe experimental studies conducted with SIFTER to filter computer and information science documents collected from the Internet and commercial database services. The experimental results demonstrate that the system performs very well in filtering documents in a realistic problem setting.
Applying GQM in an industrial software factory
Authors: Fuggetta Alfonso , Lavazza Luigi , Morasca Sandro , Cinti Stefano , Oldano Giandomenico , Orazi Elena
Published: July 2002

Goal/Question/Metric GQM) is a paradigm for the systematic definition, establishment, and exploitation of measurement programs supporting the quantitative evaluation of softare processes and products. Although GQM is a quite well-known method, detailed guidelines for establishing a GQM program in an industrial environment are still limited. Also, there are few reported experiences on the application of GQM to industrial cases. Finally, the technological support for GQM is still inadequate. This article describes the experience we have gained in applying GQM at Digital Laboratries in Italy. The procedures, experiences, and technology that have been employed in this study are largely reusable by other industrial organizations willing to introduce a GQM-based measurement program in their development environments.
Methods for information server selection
Authors: Hawking David , Thistlewaite Paul
Published: July 2002

The problem of using a broker to select a subset of available information servers in order to achieve a good trade-off between document retrieval effectiveness and cost is addressed. Server selection methods which are capable of operating in the absence of global information, and where servers have no knowledge of brokers, are investigated. A novel method using Lightweight Probe queries (LWP method) is compared with several methods based on data from past query processing, while Random and Optimal server rankings serve as controls. Methods are evaluated, using TREC data and relevance judgments, by computing ratios, both empirical and ideal, of recall and early precision for the subset versus the complete set of available servers. Estimates are also made of the best-possible performance of each of the methods. LWP and Topic Similarity methods achieved best results, each being capable of retrieving about 60% of the relevant documents for only one-third of the cost of querying all servers. Subject to the applicable cost model, the LWP method is likely to be preferred because it is suited to dynamic environments. The good results obtained with a simple automatic LWP implementation were replicated using different data and a larger set of query topics.
An architecture for automatic relational database sytem conversion
Authors: Shneiderman Ben , Thomas Glenn
Published: July 2002

Changes in requirements for database systems necessitate schema restructuring, database translation, and application or query program conversion. An alternative to the lengthy manual revision process is proposed by offering a set of 15 transformations keyed to the relational model of data and the relational algebra. Motivations, examples, and detailed descriptions are provided.
On the efficiency of pairing heaps and related data structures
Authors: Fredman Michael L.
Published: July 2002

The pairing heap is well regarded as an efficient data structure for implementing priority queue operations. It is included in the GNU C++ library. Strikingly simple in design, the pairing heap data structure nonetheless seems difficult to analyze, belonging to the genre of self-adjusting data structures. With its design originating as a self-adjusting analogue of the Fibonacci heap, it has been previously conjectured that the pairing heap provides constrant amortized time decrease-key operations, and experimental studies have supported this conjecture. This paper demonstrates, contrary to conjecture, that the pairing heap requires more than constant amortized time to perform decrease-key operations. Moreover, new experimental findings are presented that reveal detectable growth in the amortized cost of the decrease-key operation.

Second, a unifying framework is developed that includes both pairing heaps and Fibonacci heaps. The parameter of interest in this framework is the storage capacity available in the nodes of the data structure for auxiliary balance information fields. In this respect Fibonacci heaps require log log
n
bits per node when
n
items are present. This is shown to be asymptotically optimal for data structures that achieve the same asymptotic performance bounds as Fibonacci heaps and fall within this framework.
Generation and search of clustered files
Authors: Salton G. , Wong A.
Published: July 2002

A classified, or clustered file is one where related, or similar records are grouped into classes, or clusters of items in such a way that all items within a cluster are jointly retrievable. Clustered files are easily adapted to broad and narrow search strategies, and simple file updating methods are available. An inexpensive file clustering method applicable to large files is given together with appropriate file search methods. An abstract model is then introduced to predict the retrieval effectiveness of various search methods in a clustered file environment. Experimental evidence is included to test the versatility of the model and to demonstrate the role of various parameters in the cluster search process.
An Asymptotically Random Tausworthe Sequence
Authors: Tootill J. P. R. , Robinson W. D. , Eagle D. J.
Published: July 2002

The theoretical limitations on the orders of equidistribution attainable by Tausworthe sequences are derived from first principles and are stated in the form of a criterion to be achieved. A second criterion, extending these limitations to multidimensional uniformity, is also defined. A sequence possessing both properties is said to be asymptotically random as no other sequence
of the same period
could be more random in these respects.

An algorithm is presented which, for any Tausworthe sequence based on a primitive trinomial over GF(2), establishes how closely or otherwise the conditions necessary for the criteria are achieved. Given that the necessary conditions are achieved, the conditions sufficient for the first criterion are derived from Galois theory and always apply. For the second criterion, however, the period must be prime.

An asymptotically random 23-bit number sequence of astronomic period, 2
607
- 1, is presented. An initialization program is required to provide 607 starting values, after which the sequence can be generated with a three-term recurrence of the Fibonacci type. In addition to possessing the theoretically demonstrable randomness properties associated with Tausworthe sequences, the sequence possesses equidistribution and multidimensional uniformity properties vastly in excess of anything that has yet been shown for conventional congruentially generated sequences. It is shown that, for samples of a size it is practicable to generate, there can exist no purely empirical test of the sequence as it stands capable of distinguishing between it and an ∞-distributed sequence. Bounds for local nonrandomness in respect of runs above (below) the mean and runs of equal numbers are established theoretically.

The claimed randomness properties do not necessarily extend to subsequences, though it is not yet known which particular subsequences are at fault.

Accordingly, the sequence is at present suggested only for simulations with no fixed dimensionality requirements.