bluuebunny/crossref_metadata_2025 huggingface dataset:
LOCAL ENERGY-DENSITY FUNCTIONAL APPROACH TO MANY-BODY NUCLEAR SYSTEMS WITH S-WAVE PAIRING
Authors: FAYANS S. A. , ZAWISCHA D.
Published: July 2002

The ground-state properties of superfluid nuclear systems with 1S0 pairing are studied within a local energy-density functional (LEDF) approach. A new form of the LEDF is proposed with a volume part which fits the Friedman-Pandharipande and Wiringa-Fiks-Fabrocini equation of state at low and moderate densities and allows an extrapolation to higher densities which preserves causality. For inhomogeneous systems, a surface term is added, with two free parameters, which has a fractional form like a Padé approximant containing the square of the density gradient in both the numerator and denominator. In addition to the direct and exchange Coulomb interaction energy, an effective density-dependent Coulomb-nuclear correlation term is included with one more free parameter. A three-parameter fit to the masses and radii of about 100 spherical nuclei has shown that the latter term gives a contribution of the same order of magnitude as the Nolen-Schiffer anomaly in the Coulomb displacement energy. The root-mean-square deviations from experimental masses and radii with the proposed LEDF come out about a factor of two smaller than those obtained with the conventional functionals based on the Skyrme or finite-range Gogny force, or on relativistic mean-field theory. The generalized variational principle is formulated leading to the self-consistent Gor'kov equations which are sovled exactly, with physical boundary conditions both for the bound and scattering states. The method is used to calculate the differential observables such as odd-even mass differences and staggering in charge radii. With a zero-range density-dependent cutoff pairing interaction incorporating a density-gradient term, the evolution of these observables is reproduced reasonably well, including the kinks at magic neutron numbers and the sizes of the associated staggering. An extrapolation from the pairing properties of finite nuclei to pairing in infinite nuclear matter is discussed. A "reference" value of the pairing gap ΔF≈ 3.3 MeV is found for subsaturated nuclear matter at about 0.65 of the equilibrium density. With the formulated LEDF approach, we study also the dilute limit in both the weak and strong coupling regimes. Within the sum rules approach it is shown that the density-dependent pairing may also induce sizeable staggering and kinks in the evolution of the mean energies of multipole excitations.
LARGE DEFORMATION OF SPHERICAL VESICLE STUDIED BY PERTURBATION THEORY AND SURFACE EVOLVER
Authors: ZHOU JIANJUN , ZHANG YONG , ZHOU XIN , ZHONG-CAN OU-YANG
Published: July 2002

With tangent angle perturbation approach the axial symmetry deformation of a spherical vesicle in large under the pressure changes is studied by the elasticity theory of Helfrich spontaneous curvature model. Three main results in axial symmetry shape: biconcave shape, peanut shape, and one type of myelin are obtained. These axial symmetry morphology deformations are in agreement with those observed in lipsome experiments by dark-field light microscopy and in the red blood cell with two thin filaments (myelin) observed in living state. Furthermore, the biconcave shape and peanut shape can be simulated with the help of a powerful software, Surface Evolver, in which the spontaneous curvature can be easy taken into account.
FORMATION ENHANCEMENT OF THE C54-TiSi2 BY A MULTI-CYCLE PRE-COOLING TREATMENT
Authors: ZHANG LIN , LEE YONG KEUN , PARK HUN SUB
Published: July 2002

This work investigated effects of different processing methods on the transformation of the C49-TiSi 2 phase to the C54-TiSi 2 phase in 20nm IMP Ti/Si thin films. A multi-cycle pre-cooling treatment was added to the titanium silicidation process sequence before the rapid thermal annealing (RTA) step. Compared with the conventional process, this new processing method was found to enhance formation of the low-resistivity C54-TiSi 2 phase. The extent to which the C49 transformed to the C54 phase at 720°C was observed to increase with the number of the pre-cooling cycle. The kinetic mechanisms of the C49 to C54 phase transformation were adopted to explain the experimental results. It is considered that defects at the Si/Ti interface caused by the thermal mismatch between these two layers during the pre-cooling treatment contributed to the increase in the C49 nucleation sites. This supplied more C49 grain boundaries and triple junction sites at which the C54 phase could nucleate. This discovery has a potential of reducing the complexity and cost associated with forming the low-resistivity C54 phase on sub-micron structures.
VORTEX-LINE PHASE DIAGRAM FOR ANISOTROPIC SUPERCONDUCTORS
Authors: MORGADO W. A. M. , DORIA M. M. , CARNEIRO G. , DE OLIVEIRA I. G.
Published: July 2002

The zero-temperature vortex phase diagram for uniaxial anisotropic superconductors placed in an external magnetic field tilted with respect to the axis of anisotropy is studied for parameters typical of BSCCO and YBCO. The exact Gibbs free energy in the London approximation, using a self-energy expression with an anisotropic core cut-off, is minimized numerically, assuming only that the equilibrium vortex state is a vortex-line-lattice with a single vortex line per primitive unit cell. The numerical method is based on simulated annealing and uses a fast convergent series to calculate the energy of interaction between vortex lines. A phase diagram with three distinct phases is reported and the phases are characterized in detail. New results for values of the applied field close to the lower critical field are reported.
FRACTIONAL STATISTICS IN SOME EXACTLY SOLVABLE MODELS WITH PT INVARIANT INTERACTIONS
Authors: BASU-MALLICK B.
Published: July 2002

Here we review a method for constructing exact eigenvalues and eigenfunctions of a many-particle quantum system, which is obtained by adding some nonhermitian but PT invariant (i.e., combined parity and time reversal invariant) interaction to the Calogero model. It is shown that such extended Calogero model leads to a real spectrum obeying generalised exclusion statistics. It is also found that the corresponding exchange statistics parameter differs from the exclusion statistics parameter and exhibits a 'reflection symmetry' provided the strength of the PT invariant interaction exceeds a critical value.
DOES LIOUVILLE'S THEOREM IMPLY QUANTUM MECHANICS?
Authors: SYROS C.
Published: July 2002

The essentials of quantum mechanics are derived from Liouville's theorem in statistical mechanics. An elementary solution, g, of Liouville's equation helps to construct a differentiable N-particle distribution function (DF), F(g), satisfying the same equation. Reality and additivity of F(g): (i) quantize the time variable; (ii) quantize the energy variable; (iii) quantize the Maxwell–Boltzmann distribution; (iv) make F(g) observable through time-elimination; (v) produce the Planck constant; (vi) yield the black-body radiation spectrum; (vii) support chronotopology introduced axiomatically; (viii) the Schrödinger and the Klein–Gordon equations follow.

Hence, quantum theory appears as a corollary of Liouville's theorem. An unknown connection is found allowing the better understanding of space-times and of these theories.
THE TRANSVERSE ISING MODEL BY CBF
Authors: CLARK J. W. , RISTIG M. L. , KIM J. W.
Published: July 2002

The method of correlated basis functions (CBF) is applied at the variational level to the transverse Ising model in two and three spatial dimensions (D=2,3). The model consists of Pauli spins arranged on a simple square or cubic lattice, experiencing nearest-neighbor interactions through their x components and subject to a transverse field in the z direction of strength λ. Working at zero temperature, full optimization of a Hartree-Jastrow trial wave function is performed by solving two Euler-Lagrange equations, namely a renormalized Hartree equation for the order parameter characterizing the ferromagnetic phase and a paired-magnon equation for the optimal two-spin spatial distribution function. The optimized trial wave function yields a second-order transition with a numerically determined critical coupling of λc=3.14(D=2) or λc= 5.10(D=3). Numerical results have been obtained for the magnetization order parameter, the energy per spin and its potential component, the static structure function at zero wave number, and the magnon energy gap corresponding to a Feynman description of the elementary excitations. Correlated density matrix theory provides for a natural extension of this approach to finite temperature.
SOFT MODE AND SPIN-GLASS LIKE TRANSITION IN INSULATING GLASS
Authors: BUSIELLO G. , SABUROVA R. V.
Published: July 2002

The spectrum and damping of collective excitations of a system of electric dipole centers with internal degrees of freedom in glass are calculated. It is shown that one of the collective modes becomes soft, signaling a spin-glass like phase transition in insulating glass. The contribution to the specific heat is determined. The possibility of phase transition from paraelectric to electric pseudospin glass phase in dielectric glass is considered.
Fluctuation and Anisotropy in the Resistivity of Bi2Sr2CaCu2O8+x Single Crystal
Authors: Fastampa R. , Giura M. , Sarti S. , Marcon R. , Neri D. , Silva E. , Boffa V.
Published: July 2002

We report a study of the resistive transitions in Bi2Sr2CaCu2O8+x in presence of an applied magnetic field (up to 12 tesla) at various field orientations. We focus our attention on the results obtained with orientations parallel and perpendicular to the (a,b) planes. We show that scaling arguments, typical of dissipative regimes independent of oriented defects, can explain the experimental findings, provided a 3D-2D crossover is assumed as the temperature is lowered, due to the variation of the out of plane coherence length.
Characterization of an Electrorheological Suspension of Poly(Vinyl Alcohol) in Corn Oil
Authors: Bombard Antonio José Faria , Joekes Inés
Published: July 2002

Suspensions of poly(vinyl alcohol) at 31% w/w in corn oil were studied. At 20°C, yield stresses of 7, 39, 103 and 170 Pa, respectively at 0, 500, 1000 and 1500 Vdc/mm were obtained. At 25°C and 500 Vrms/mm, measurements in the range of 20 to 1000 Hz were made. Yield stresses were not obtained, but the electrorheological effect was less pronounced under an AC field than a DC field: at 20 Hz and steady shear rates of 10.8, 48.6 and 97.2s-1, the shear stresses were 16, 30 and 50 Pa, respectively. Under 500 Vdc/mm, at the same shear rates, the shear stresses were 40, 65 and 90 Pa. The shear stresses decrease exponentially as the frequency rises. The reproducibility of this effect is good: the values stay between ± 20% for triplicate suspension samples.
QUANTUM-CHEMISTRY STUDY OF SEMICONDUCTOR SYSTEMS: THE INITIAL OXIDATION OF THE (111)Si-H SURFACE
Authors: BAIERLE R. J. , CALDAS M. J.
Published: July 2002

We propose a well-defined procedure to adapt a Quantum-Chemistry technique for the study of semiconductor structures. The procedure comprises use of a Bloch-periodic version of the standard molecular code and a nanocrystal cluster model. We reparametrize according to this procedure the MNDO/AM1 technique for Si and O and present this new parametrization AM1/Crystal. We apply AM1/Crystal to study oxidation of the hydrogenated silicon(111) surface, at the initial stages, when the absorbed oxygen atoms form isolated surface defects. We obtain self-consistent charge distributions and total energies for optimised geometries of different incorporation sites and configurations, including up to three oxygen atoms. We also obtain vibrational frequencies for the complexes that compare well with available experimental data. Our results confirm that backbond incorporation (Si-O-Si-H) is energetically favored compared to a surface hydroxyl configuration (Si-OH) and indicate that the first subsurface layer incorporation should proceed by island formation in a two-dimensional regime.
SINE-GORDON QUANTUM MAGNETS
Authors: EßLER FABIAN H. L.
Published: July 2002

We discuss applications of the Sine-Gordon model to quasi-one-dimensional quantum magnets.
ON THE CORRESPONDENCE BETWEEN CLASSICAL AND QUANTUM MEASUREMENTS ON A BOSONIC FIELD
Authors: D'ARIANO G. M. , SACCHI M. F. , YUEN H. P.
Published: July 2002

We study the correspondence between classical and quantum measurements on a harmonic oscillator that describes a one-mode bosonic field with annihilation and creation operators a and a† with commutation [a, a†]=1. We connect the quantum measurement of an observable Ô=Ô (a, a†) of the field with the possibility of amplifying the observable Ô ideally through a quantum amplifier which achieves the Heisenberg-picture evolution Ô→ gÔ, where g is the gain of the amplifier. The "classical" measurement of Ô corresponds to the joint measurement of the position [Formula: see text] and momentum [Formula: see text] of the harmonic oscillator, with following evaluation of a function [Formula: see text] of the outcome α=q+ip. For the electromagnetic field the joint measurement is achieved by a heterodyne detector. The quantum measurement of Ô is obtained by preamplifying the heterodyne detector through an ideal amplifier of Ô and rescaling the outcome by the gain g. We give a general criterion which states when this preamplified heterodyne detection scheme approaches the ideal quantum measurement of Ô in the limit of infinite gain. We show that this criterion is satisfied and the ideal measurement is achieved for the case of the photon number operator a† a and for the quadrature [Formula: see text], where one measures the functions [Formula: see text] and [Formula: see text] of the field, respectively. For the photon number operator a† a the amplification scheme also achieves the transition from the continuous spectrum |α|2∈ℝ to the discrete one n∈ℕ of the operator a† a. Moreover, for both operators a† a and [Formula: see text] the method is robust to nonunit quantum efficiency of the heterodyne detector. On the other hand, we show that the preamplified heterodyne detection scheme does not work for arbitrary observable of the field. As a counterexample, we prove that the simple quadratic function of the field [Formula: see text] has no corresponding polynomial function [Formula: see text] — including the obvious choice f= Im (α2) — that allows the measurement of [Formula: see text] through the preamplified heterodyne measurement scheme.
A POSSIBLE FIRST PRINCIPLE ARGUMENTS ON THE SYMMETRY OF SUPERCONDUTING GAP PARAMETER
Authors: GONG CHANGDE
Published: July 2002

The symmetry of superconducting gap parameter in high-Tc cuprate superconductors has been studied based on general physical considerations. The disagreement between theoretical prediction and experimental data is discussed.
PREDICTING FILM THERMAL COUPLING FROM THE CURRENT-INDUCED S→N TRANSITION
Authors: Harrabi Kh. , Ladan F-R , Maneval J-P
Published: July 2002

C-axis YBCO bridges (≈10 μm wide) deposited on crystalline surfaces were submitted to current step pulses and their resistance was monitored as a function of time. The stable dissipative regime sets in after a latency period Td on the scale of nanoseconds characteristic of the phase-slip (PSC) regime. Through a time-dependent Ginzburg-Landau analysis of the superconducting-to-normal transition, Td is used to provide the phonon escape time virtually up to Tc. Results are in quantitative agreement with measurements performed either by others workers or by independent methods presented at this Conference.
A RE-EXAMINATION OF THE ELECTRONIC STRUCTURE AND FERMI SURFACE OF BSCCO
Authors: DESSAU D. S. , CHUANG Y.-D. , GROMKO A. D. , AIURA Y. , YAMAGUCHI Y. , OKA K. , ARKO A. J. , JOYCE J. , EISAKI H. , UCHIDA S. I. , NAKAMURA K. , ANDO YOICHI
Published: July 2002

We have performed angle-resolved photoemission (ARPES) experiments on a variety of Bi-Sr-Ca-Cu-O (BSCCO) samples. By applying a stricter set of FS crossing criteria as well as by varying the incident photon energy outside the usual range, we have found very different behavior from that previously observed. Instead of being centered around the X or Y points and having hole-like character, we argue that the FS is centered around the Γ point and contains electron-like portions. In addition, the flat bands just below EF around [Formula: see text] are not observed at the photon energy of 33eV, raising questions about the origin of these states.
THE EFFECT OF OXYGEN ON SUPERCONDUCTIVITY AND MAGNETISM IN Eu1.5Ce0.5RuSr2Cu2O10 +δ
Authors: FELNER I. , ASAF U. , LEVI Y. , MILLO O.
Published: July 2002

The Eu 1.5 Ce 0.5 RuSr 2 Cu 2 O 10+δ compound is the first known Cu-O based material in which superconductivity (SC) and weak-ferromagnetism (W-FM) coexist (T c =32 K, T M =122 K). SC is confined to the CuO 2 planes, and the magnetic ordering is due to the Ru sublattice. For as-prepared samples (APS), the normal-state resistivity is characteristic of an under-doped SC compound. The hole doping in CuO 2 planes, can be achieved with appropriate variation of the oxygen concentrations, which is obtained by annealing the APS under oxygen pressures up to 150 atm. The effect of oxygen treatment is to shift the onset of SC monotonically, up to 49 K. For 75 atm., two transition temperatures are found, indicating the existence of two SC phases. At the same time, scanning tunneling spectroscopy measurements show spatial variations of the gap with a double-peak distribution.
CONDUCTANCE FLUCTUATIONS IN THE COULOMB BLOCKADE REGIME
Authors: BERKOVITS RICHARD
Published: July 2002

Recent experiments on the conductance through semiconducting quantum dots weakly coupled to external leads enable us to study the ground state properties of these dots. The spacings between the resonant peaks as well as their heights indicate that the electrons in the dot are in a correlated state due to their low density, in which both disorder and electron–electron interactions determine the properties of the electron system. Numerical treatments of model Hamiltonians were successful in reproducing many of the experimentally observed features of the conductance and reveal important clues on the relevant physics behind these features. These studies also indicate that the ground state is spin polarized, a prediction which could be experimentally verified.
LEVEL STATISTICS FOR THE GAPPED SPIN-1/2 XXZ HEISENBERG CHAINS
Authors: LIU YICHANG , SUN LIQUN , DAI JIANHUI , QIN SHAOJIN
Published: July 2002

We study the level spacing distribution of the gapped spin-1/2 XXZ Heisenberg chains. The level spacing distributions are calculated for a series of chain lengths from 10 to 19 by numerical exact diagonalization. We conclude that the missed states in the Bethe ansatz solution are statistically minor in thermodynamics limit in the whole spectrum.
EVEN- AND ODD-BINOMIAL STATES AS EIGENSTATES OF A NONLINEAR COMBINATION OF RADIATION FIELD OPERATORS
Authors: FAN HONG-YI , JING SI-CONG
Published: July 2002

We show that the even- and odd-binomial states are eigenstates of the definite nonlinear combination of radiation field operators, which generalizes the nonlinear coherent state theory in quantum optics.
RELAXATION OF Si DIMER ON THE Si(001) SURFACE INDUCED BY Pt ADSORPTION
Authors: CHOI D. S. , JUNG J. W. , YOON M. S. , JUNG K. H. , WHANG C. N.
Published: July 2002

The surface structure of Pt/Si(001) has been studied using LEED and Low Energy Ion Scattering Spectroscopy (ISS). We find that the Pt coverages are saturated at 0.25 ML after annealing regardless of the initial coverages between 0.5 ~ 1.0 ML. We observe a c(4 × 2) image after annealing the Pt/Si(001) sample at 700°C and a clean c(4 × 6) image mixed with a clean c(4 × 2) image at annealing temperatures around 900°C. We find the structure of the Si(001) surface is changed due to Pt adsorption. The changed Si(001) surface still has the p(2 × 1) structure with increasing dimer length 0.6 Å
Application of ESR to High-Tc Superconductors and Related Materials: I. ESR Study of Cu2+ as a Probe of Crystal Growth Rates of Y2BaCuOy at High Temperatures
Authors: Yamamoto K. , Arai N. , Hotta K. , Sugawara K. , Hirose H.
Published: July 2002

A number of pellets with nominal concentration ratio of Y:Ba:Cu =2:1:1 have been sintered in air at temperatures between 800°C and 1400°C for 1 min ~24 h. The heat-treated samples were quenched to room temperature and the crystal growth rates of Y 2 BaCuO y≃5 were measured using ESR of Cu 2+. Systematic data on the growth rates were taken as a function of heat-treatment temperature and period.
ANOMALOUS BCS EQUATION FOR A LUTTINGER SUPERCONDUCTOR
Authors: MASTROPIETRO V.
Published: July 2002

A self-consistence equation describing a superconductor whose normal state is a Luttinger liquid is computed in a rigorous way by renormalization group techniques. The gap and the critical temperatures are quite different with respect to the ones of normal superconductors (i.e. superconductors whose normal state is a Fermi liquid) and in particular, the critical temperature can be quite high for suitable values of the parameters. Such self-consistence equation can be obtained in a BCS mean field theory for a model of two Mattis models exchanging Cooper pairs. The connection of this model with recent theories of high T c superconductivity is briefly discussed.
INTERNAL INSTABILITY OF VIBRATIONAL MOTION OF A TRIATOMIC MOLECULE: CLASSICAL APPROACH
Authors: STANEK JERZY , KONARSKI JERZY
Published: July 2002

This study reports the manifestation of KAM theory in a simple triatomic molecule. Numerical examples are presented which show that for some Hamiltonian systems monotonic increase in energy does not always lead to irregular behavior. The transition from the normal mode at low energy to a local mode at higher one preserves the tori for some initial conditions, but between these two well-defined states, there are strongly perturbed ones which reveal a significant presence of chaotic behavior.
CONSTRUCTION OF SUBOPTIMAL FEEDBACK CONTROL FOR CHAOTIC SYSTEMS USING B-SPLINES WITH OPTIMALLY CHOSEN KNOT POINTS
Authors: LEE H. W. J. , TEO K. L. , LEE W. R. , WANG S.
Published: July 2002

In this paper we consider a class of optimal control problem involving a chaotic system, where all admissible controls are required to satisfy small boundedness constraints. A numerical approach is developed to seek for an optimal feedback control for the optimal control problem. In this approach, the state space is partitioned into subregions, and the controller is approximated by a linear combination of a modified third order B-spline basis functions. The partition points are also taken as decision variables in this formulation. An algorithm based on this approach is proposed. To show the effectiveness of the proposed method, a control problem involving the Lorenz system is solved by the proposed approach. The numerical results demonstrate that the method is efficient in the construction of a robust, near-optimal control.
ROTATION SETS FOR ORBITS OF DEGREE ONE CIRCLE MAPS
Authors: ALSEDÀ LLUÍS , MAÑOSAS FRANCESC , CHAS MOIRA
Published: July 2002

Let F be the lifting of a circle map of degree one. In [Bamón et al., 1984] a notion of F-rotation interval of a point [Formula: see text] was given. In this paper we define and study a new notion of a rotation set of point which preserves more of the dynamical information contained in the sequences [Formula: see text] than the one preserved from [Bamón et al., 1984]. In particular, we characterize dynamically the endpoints of these sets and we obtain an analogous version of the Main Theorem of [Bamón et al., 1984] in our settings.
SPATIAL DISORDER OF CELLULAR NEURAL NETWORKS — WITH BIASED TERM
Authors: BAN JUNG-CHAO , LIN SONG-SUN , HSU CHENG-HSIUNG
Published: July 2002

This study describes the spatial disorder of one-dimensional Cellular Neural Networks (CNN) with a biased term by applying the iteration map method. Under certain parameters, the map is one-dimensional and the spatial entropy of stable stationary solutions can be obtained explicitly as a staircase function.
SOME ANALYTICAL CRITERIA FOR LOCAL ACTIVITY OF TWO-PORT CNN WITH THREE OR FOUR STATE VARIABLES: ANALYSIS AND APPLICATIONS
Authors: MIN LEQUAN , YU NA
Published: July 2002

The local activity principle of the Cellular Nonlinear Network (CNN) introduced by Chua [1997] has provided a powerful tool for studying the emergence of complex patterns in a homogeneous lattice formed by coupled cells. This paper presents some analytical criteria for the local activity of two-port CNN cells with three or four state variables. As a first application, a coupled excitable cell model (ECM) CNN is introduced, which has cells defined by the Chay equations representing ionic events in excitable membranes in terms of a Hodgkin–Huxley type formalism. The bifurcation diagram of the ECM CNN supplies a possible explanation for the mechanism of arrhythmia (from normal to abnormal until stopping) of excitable cells: the cell parameter is changed from an active unstable domain to an edge of chaos. The member potentials along fibers are simulated numerically, where oscillatory patterns, chaotic patterns as well as convergent patterns are observed. As a second application, a smoothed Chua's circuit (SCC) CNN with two ports is presented, whose prototype has been introduced by Chua as a dual-layer two-dimensional reaction–diffusion CNN in order to obtain Turing patterns. The bifurcation diagrams of the SCC CNN are the same as those with one port, which have only active unstable domains and edges of chaos. Numerical simulations show that in the active unstable parameter domains, the evolutions of the patterns of the state variables of the SCC CNNs can exhibit divergence, periodicity and chaos, where, in the parameter domains located in the edge of chaos, periodic patterns and divergent patterns are observed. These results demonstrate once again the effectiveness of the local activity theory in choosing the parameters for the emergence of complex patterns of CNNs.
DISTRIBUTION OF THE LYAPUNOV EXPONENT OF THE CHAOTIC SKEW TENT MAP
Authors: LAI DEJIAN , CHEN GUANRONG , HASLER MARTIN
Published: July 2002

Distribution of the Lyapunov exponent of the chaotic skew tent map is studied. Complete expressions of the mean and the variance as well as the asymptotic distributions of the Lyapunov exponent are obtained for both noisy and noiseless cases of the map.
EFFECTS OF A QUENCHED DISORDER ON WAVE PROPAGATION IN EXCITABLE MEDIA
Authors: SENDIÑA-NADAL I. , PÉREZ-MUÑUZURI V. , GÓMEZ-GESTEIRA M. , MUÑUZURI A. P. , PÉREZ-VILLAR V. , VIVES D. , SAGUÉS F. , CASADEMUNT J. , SANCHO J. M. , RAMÍREZ-PISCINA L.
Published: July 2002

The behavior of autowaves under the effect of a quenched disorder is studied in the framework of the light-sensitive Belousov–Zhabotinsky reaction. This allows us to introduce spatial disorder on the excitability by projecting patterns of light transmittance. In particular, we have selected a dichotomic random distribution of levels of transmittance. If the two values of transmittance are equally probable and allows wave propagation without breaking the waves, we find an opposite effect on the wave front velocity and shape depending on the considered dimension. On the other hand, if one of the two values of the transmittance distribution is set on the nonexcitable region, percolation phenomena can arise by changing the number of excitable sites. The different addressed situations are analytically interpreted giving theoretical predictions for the experimental and numerical results.
TOWARDS A UNIFIED VERSION MODEL USING THE RESOURCE DESCRIPTION FRAMEWORK (RDF)
Authors: KITCHAROENSAKKUL SUPANAT , WUWONGSE VILAS
Published: July 2002

Version control, a fundamental component of Software Configuration Management (SCM) — a key mechanism for software development especially in large-scale systems — lacks a unified foundation for interchangeability, interoperability, and integrability. A practical solution of such problems is not readily achieved because version controls of different SCM systems employ various version models. Hence a single unified version model is required.

The work develops a single formalism to model major version control approaches as well as a prototype system. Its architecture is based on a federated SCM architecture and introduces a new SCM foundation which contains two layers: unified SCM representation and computation, based on the Resource Description Framework (RDF) and the Equivalent Transformation computational model, respectively. The evolution of software objects, their relationships as well as team cooperation strategies can be uniformly expressed under the representation layer. The computational layer is briefly mentioned for framework demonstration. Finally, a simple prototype system is presented.
SINGULARITY FEATURES OF PORE-SIZE SOIL DISTRIBUTION: SINGULARITY STRENGTH ANALYSIS AND ENTROPY SPECTRUM
Authors: CANIEGO F. J. , MARTÍN M. A. , SAN JOSÉ F.
Published: July 2002

In this paper, several features of pore-size soil distribution are first analyzed, suggesting that they are closer to those of singular measures than to those of distributions with smooth density. In a second step, the weighted singularity strength of an experimental measure obtained by image analysis of soil samples is evaluated. The results of this analysis show the singular nature of pore-size distribution. Finally, the distribution is characterized by means of a spectrum of entropies computed on distorted measures associated with the original experimental measure.
WETTING OF THE FERROELECTRIC DOMAIN STRUCTURE IN (Ba,Sr)TiO3
Authors: DORFMAN SIMON , FUKS DAVID , GORDON ALEX , WYDER PETER
Published: July 2002

Wetting of the ferroelectric domain walls is studied in external magnetic fields and for composition changes in (Ba,Sr)TiO 3. We discuss the sensibility of the domain structure to concentration of alloying element in perovskite ferroelectrics. A considerable magnetic-field and concentration-induced variation of the ferroelectric domain size and the paraelectric layer width is demonstrated. The concentration-temperature "phase diagram," showing the range of the wetting existence, is calculated.
REPLANTATION OF FINGERTIP AMPUTATION
Authors: Wancheng Tian , Chuanzhong Lu , Haitao Song , Qinping Fan , Fengting Chang
Published: July 2002

From April 1987 to February 1995, 188 amputated fingertips in 156 cases were replanted. 177 fingertips survived (94.3%). The follow-up time ranged from 12 to 36 months. The cosmesis and functions of the replanted fingertips were excellent.
Effect of Basic Fibroblast Growth Factor on Angiogenesis in Rabbit Flexor Digitorum Profundus Tendons Lacerated and Repaired in The Avascular Area
Authors: Shao F. , Sasaki K. , Tsuchida H. , Takayanagi M. , Watanabe Y.
Published: July 2002

Prompt angiogenesis has been hypothesised as beneficial for successful surgical repair of the flexor digitorum profundus (FDP) tendon, especially in the avascular area known as zone II. After the tendon has been lacerated and sutured, we analysed the angiogenic effects of the basic fibroblast growth factor (bFGF) on the suture site of zone II and the normal vasculature of rabbit FDP tendons, using the silicon vascular casting method in combination with microscopy. Intratendinous angiogenesis was accelerated at two weeks in the bFGF group. Capillaries formed well-developed vascular networks in the layer of the epitenon and invaded the tendon internally in the suture site along the connective tissue sheath. Three weeks after laceration and repair, the suture only group approved the same as the bFGF group at two weeks following treatment. These results suggest that bFGF has a significant angiogenic effect on a lacerated and sutured avascular area of an FDP tendon, along with development of the connective tissue sheath which may promote intratendinous vascular invasion and favourably influence the tendon repair process.
MULTI-AGENT LEARNING IN RECOMMENDER SYSTEMS FOR INFORMATION FILTERING ON THE INTERNET
Authors: DELGADO JOAQUIN , ISHII NAOHIRO
Published: July 2002

Recommender Systems (RS), allow users to share information about items they like or dislike and obtain, in a timely fashion, recommendations based on predictions about unseen items (physical or information goods and/or services). In this process, users' preferences are considered to be the learning target functions. We study Agent-based Recommender Systems (ARS) under the scope of online learning in Multi-Agent systems (MAS). This approach models the problem as a pool of independent cooperative predictor agents, one per each user (the masters) in the system, in situations in which each agent (the learners) faces a sequence of trials, with a prediction to make in every step, eventually getting the correct value from its master. Each learner is willing to discover the degree of similarity among the target function of its master and those of other agents' masters (i.e. preference similarity). The agent uses this information for the calculation of its own prediction task, the goal being to make as few mistakes as possible. A simple, yet effective method is introduced in order to construct a compound algorithm for each agent by combining memory-based individual prediction and online weighted-majority voting. We give a theoretical mistake bound for this algorithm that is closely related to the total loss of the best predictor agent in the pool. Finally, we conduct some experiments obtaining results that empirically support these ideas and theories.
ECONOPHYSICS: WHAT CAN PHYSICISTS CONTRIBUTE TO ECONOMICS?
Authors: STANLEY H. EUGENE , AMARAL LUÍS A. NUNES , GOPIKRISHNAN PARAMESWARAN , LIU YANHUI , PLEROU VASILIKI , ROSENOW BERND
Published: July 2002

In recent years, a considerable number of physicists have started applying physics concepts and methods to understand economic phenomena. The term "Econophysics" is sometimes used to describe this work. Economic fluctuations can have many repercussions, and understanding fluctuations is a topic that many physicists have contributed to in recent years. Further, economic systems are examples of complex interacting systems for which a huge amount of data exist and it is possible that the experience gained by physicists in studying fluctuations in physical systems might yield new results in economics. Much recent work in econophysics is focused on understanding the peculiar statistical properties of price fluctuations in financial time series. In this talk, we discuss three recent results. The first result concerns the probability distribution of stock price fluctuations. This distribution decreases with increasing fluctuations with a power-law tail well outside the Lévy stable regime and describes fluctuations that differ by as much as 8 orders of magnitude. Further, this nonstable distribution preserves its functional form for fluctuations on time scales that differ by 3 orders of magnitude, from 1 min up to approximately 10 days. The second result concerns the accurate quantification of volatility correlations in financial time series. While price fluctuations themselves have rapidly decaying correlations, the volatility estimated by using either the absolute value or the square of the price fluctuations has correlations that decay as a power-law and persist for several months. The third result bears on the application of random matrix theory to understand the correlations among price fluctuations of any two different stocks. We compare the statistics of the cross-correlation matrix constructed from price fluctuations of the leading 1000 stocks and a matrix with independent random elements, i.e., a random matrix. Contrary to first expectations, we find little or no deviation from the universal predictions of random matrix theory for all but a few of the largest eigenvalues of the cross-correlation matrix.
TWO CHARACTERISATIONS OF THE LEXICOGRAPHIC EGALITARIAN SOLUTION
Authors: CHANG CHIH , HWANG YAN-AN
Published: July 2002

Two new axioms, additivity of additional bonus (AAB) and reduced game monotonicity (RGM), are introduced. AAB states that the players can gain an additional bonus after they achieved an agreement; on the other hand, if the bargaining fails then they get nothing. With its help, we characterise the lexicographic egalitarian solution by individual rationality (IR), AAB and consistency (CON). The other axiom, RGM, is a weaker axiom than CON and strong monotonicity (SMON), respectively. Using Pareto optimal (PO), IR, AAB and RGM, the second characterisation of the lexicographic egalitarian solution is presented.
FAULT-TOLERANT COMMUNICATIONS ON HYPERCUBE-CLUSTERS
Authors: LOH PETER KOK KEONG , HSU WEN JING
Published: July 2002

Hierarchical interconnection networks with n-dimensional hypercube clusters can strike a balance between wide application suitability, size scalability as well as reliability. Cluster communications support for such networks must therefore be reliable and efficient without incurring large overheads. This paper proposes a reliable and cost-effective intra-cluster communications strategy for such a class of interconnection networks. The routing algorithm can tolerate up to (n - 1) component faults in the cluster and generates routes that are cycle-free and livelock-free. The message is guaranteed to be optimally (respectively, sub-optimally) delivered within a maximum of n (respectively, 2n - 1) hops. The message overhead incurred is one of the lowest reported for the specified fault tolerance level – with only a single n-bit routing vector accompanying the message to be communicated. Finally, routing hardware support may be simply achieved with standard components, facilitating integration with the host network.
THE LATTICE STRUCTURE OF PRERADICALS II: PARTITIONS
Authors: RAGGI FRANCISCO , RÍOS JOSÉ , RINCÓN HUGO , FERNÁNDEZ-ALONSO ROGELIO , SIGNORET CARLOS
Published: July 2002

We continue the study of the preradicals of a ring in the lattice point of view. We introduce several interesting preradicals associated to a given preradical and some partitions of the whole lattice in terms of preradicals. As an application, we also give some classification theorems.
AN APPROACH FOR COMPARATIVE PERFORMANCE TESTING OF SURGICAL BURS
Authors: TAVAKOLI M. S. , POOLE BRETT
Published: July 2002

In this paper, a numerical procedure for obtaining a cutting performance "signature" for a bur is proposed. This procedure is applied to a comparative analysis of the cutting performance of a surgical bur under various operating conditions. An experimental method, which uses a constant feed rate and measures feed force, is utilized to perform tests leading to the data needed for the aforementioned procedure. Several proof-of-concept tests are performed and their results are presented. The proposed approach shows capability for tracking the cutting performance of a bur as it gets duller.
What every computer scientist should know about floating-point arithmetic
Authors: Goldberg David
Published: July 2002

Floating-point arithmetic is considered as esoteric subject by many people. This is rather surprising, because floating-point is ubiquitous in computer systems: Almost every language has a floating-point datatype; computers from PCs to supercomputers have floating-point accelerators; most compilers will be called upon to compile floating-point algorithms from time to time; and virtually every operating system must respond to floating-point exceptions such as overflow. This paper presents a tutorial on the aspects of floating-point that have a direct impact on designers of computer systems. It begins with background on floating-point representation and rounding error, continues with a discussion of the IEEE floating point standard, and concludes with examples of how computer system builders can better support floating point.
What are race conditions?
Authors: Netzer Robert H. B. , Miller Barton P.
Published: July 2002

In shared-memory parallel programs that use explicit synchronization,
race conditions
result when accesses to shared memory are not properly synchronized. Race conditions are often considered to be manifestations of bugs, since their presence can cause the program to behave unexpectedly. Unfortunately, there has been little agreement in the literature as to precisely what constitutes a race condition. Two different notions have been implicitly considered: one pertaining to programs intended to be deterministic (which we call
general races
) and the other to nondeterministic programs containing critical sections (which we call
data races
). However, the differences between general races and data races have not yet been recognized. This paper examines these differences by characterizing races using a formal model and exploring their properties. We show that two variations of each type of race exist:
feasible
general races and data races capture the intuitive notions desired for debugging and
apparent
races capture less accurate notions implicitly assumed by most dynamic race detection methods. We also show that locating feasible races is an NP-hard problem, implying that only the apparent races, which are approximations to feasible races, can be detected in practice. The complexity of dynamically locating apparent races depends on the type of synchronization used by the program. Apparent races can be exhaustively located efficiently only for weak types of synchronization that are incapable of implementing mutual exclusion. This result has important implications since we argue that debugging general races requires exhaustive race detection and is inherently harder than debugging data races (which requires only partial race detection). Programs containing data races can therefore be efficiently debugged by locating certain easily identifiable races. In contrast, programs containing general races require more complex debugging techniques.
Algorithm 715: SPECFUN–a portable FORTRAN package of special function routines and test drivers
Authors: Cody W. J.
Published: July 2002

SPECFUN is a package containing transportable FORTRAN special function programs for real arguments and accompanying test drivers. Components include Bessel functions, exponential integrals, error functions and related functions, and gamma functions and related functions.
Algorithm 733: TOMP–Fortran modules for optimal control calculations
Authors: Kraft Dieter
Published: July 2002

A great number of analysis and synthesis problems of modern processes can be written as state and control constrained optimal control problems governed by ordinary differential equations with multipoint boundary values. As the software tools for following this attractive approach are still missing or can be used only by experts, the structure and usage of an easy-to-use software package is described which efficiently solves the given problem. Among its features are user-orientation, applicability on personal computers and mainframes, and robustness with respect to model changes and inaccurate starting values. It has been tested on a number of complex engineering tasks, including aerospace and robotic trajectory planning.
Analyzing due process in the workplace
Authors: Gerson Elihu M. , Star Susan Leigh
Published: July 2002

Every office is an open system, and the products of office work are the result of decentralized negotiations. Changing patterns of task organization and alliance inevitably give rise to inconsistent knowledge bases and procedures. This implies that there are no globally correct answers to problems addressed by OISs. Rather, systems must deal with multiple competing, possibly irreconcilable, solutions. Articulating alternative solutions is the problem of
due process
. This problem and its consequences are illustrated by a case study of a rate-setting group in a large health insurance firm.

There is no formal solution to the problem of due process. But it must be solved in practice if distributed intelligent OISs are to be developed. We propose an alternative approach based on the work of social scientists concerned with analyzing analogous problems in human organization. Solution of the due process problem hinges on developing local closures to the problem faced by an organization. This means analyzing (a) local, tacit knowledge and its transfer ability; (b) articulation work, that is, reconciling incommensurate assumptions and procedures.
CYC
Authors: Lenat Douglas B.
Published: July 2002

Since 1984, a person-century of effort has gone into building CYC, a universal schema of roughly 10
5
general concepts spanning human reality. Most of the time has been spent codifying knowledge about these concepts; approximately 10
6
commonsense axioms have been handcrafted for and entered into CYC's knowledge base, and millions more have been inferred and cached by CYC. This article examines the fundamental assumptions of doing such a large-scale project, reviews the technical lessons learned by the developers, and surveys the range of applications that are or soon will be enabled by the technology.
The solution of a combustion problem with Rosenbrock methods
Authors: Ostermann A. , Kaps P. , Bui T. D.
Published: July 2002

Solving flame propagation problems with the method of lines leads to large systems of ordinary differential equations. These systems are usually solved by Backward Differentiation Formula (BDF) methods, such as by LSODE of Hindmarsh. Recently, Rosenbrock methods turned out to be rather successful for integrating small systems with inexpensive function and Jacobian evaluations. However, no test has been done on the performance of some recently developed Rosenbrock codes in a situation in which the dimension of the system is large, for example, over one hundred equations. These Rosenbrock codes performed quite well on the STIFF DETEST and other small systems. The aim of this paper is to investigate the performance of the Rosenbrock methods in solving the flame propagation problem by the method of lines.
The X window system
Authors: Scheifler Robert W. , Gettys Jim
Published: July 2002

An overview of the X Window System is presented, focusing on the system substrate and the low-level facilities provided to build applications and to manage the desktop. The system provides high-performance, high-level, device-independent graphics. A hierarchy of resizable, overlapping windows allows a wide variety of application and user interfaces to be built easily. Network-transparent access to the display provides an important degree of functional separation, without significantly affecting performance, which is crucial to building applications for a distributed environment. To a reasonable extent, desktop management can be custom-tailored to individual environments, without modifying the base system and typically without affecting applications.