bluuebunny/crossref_metadata_2025 huggingface dataset:
SU(2)0 AND OSp(2|2)-2 WZNW MODELS: TWO CURRENT ALGEBRAS, ONE LOGARITHMIC CFT
Authors: KOGAN I. I. , NICHOLS A.
Published: July 2002

We show that the SU (2)0 Wess–Zumino–Novikov–Witten (WZNW) model has a hidden OSp (2|2)-2 symmetry. Both these theories are known to have logarithms in their correlation functions. We also show that, like OSp(2|2)-2, the logarithmic structure present in the SU (2)0 model is due to an underlying c = - 2 sector. We demonstrate that the quantum Hamiltonian reduction of SU (2)0 leads very directly to the correlation functions of the c=-2 model. We also discuss some of the novel boundary effects which can take place in this model.
LARGE SOLAR NEUTRINO MIXING IN AN EXTENDED ZEE MODEL
Authors: KITABAYASHI TERUYUKI , YASUÈ MASAYAKI
Published: July 2002

The Zee model, which employs the standard Higgs scalar (ϕ) with its duplicate (ϕ ′) and a singly charged scalar (h+), can utilize two global symmetries associated with the conservation of the numbers of ϕ and ϕ′, Nϕ, ϕ′, where Nϕ + Nϕ′ coincides with the hypercharge while Nϕ - Nϕ′ (≡ X) is a new conserved charge, which is identical to Le - Lμ - Lτ for the left-handed leptons. Charged leptons turn out to have e–μ and e–τ mixing masses, which are found to be crucial for the large solar neutrino mixing. In an extended version of the Zee model with an extra triplet Higgs scalar (s), neutrino oscillations are described by three steps: (1) the maximal atmospheric mixing is induced by democratic mass terms supplied by s with X = 2 that can initiate the type II seesaw mechanism for the smallness of these masses; (2) the maximal solar neutrino mixing is triggered by the creation of radiative masses by h+ with X=0; (3) the large solar neutrino mixing is finally induced by a νμ - ντ mixing arising from the rotation of the radiative mass terms as a result of the diagonalization that converts e–μ and e–τ mixing masses into the electron mass.
REVIEW OF BALLOONS MUON MEASUREMENT IN THE ATMOSPHERE
Authors: SANUKI TOMOYUKI
Published: July 2002

In order to study neutrino oscillation phenomena using atmospheric neutrinos, it is crucially important to calculate their absolute fluxes and spectral shapes accurately. Since production and decay processes of muons are accompanied by neutrino production, observations of atmospheric muons give fundamental information about atmospheric neutrinos. Atmospheric muons have been measured at various sites; from a ground level to a balloon floating altitude. Very precise measurement has been carried out on the ground. Muon growth curves are measured during balloon ascending periods. These data can be used to investigate hadronic interaction models. Investigations of atmospheric muons will improve accuracy of the neutrino calculations. Statistics in the muon measurement during balloon experiments are still insufficient. In order to improve the statistics drastically, dedicated muon experiments are very important.
Solution of a Chain-Like Ising Spin Cluster Model
Authors: Gulacsi Miklos , Gulacsi Zsolt
Published: July 2002

We present a solution for a chain-like cluster model, when the elements of the cluster are Ising spins interacting via a short-range potential. The solution is obtained in the limit where no spin agglomeration or percolation type processes are allowed. We also determine the magnetic susceptibility of the model.
Delta Interaction on a Ring: The Topological Bethe Ansatz
Authors: McGuire J. B.
Published: July 2002

The integrable state function of delta interaction on an infinite line is constrained to a ring of finite circumference. The state function remains consistent with the Bethe ansatz, but in a multiply connected state space. The constants of integration of the integrable state function are roots of a transcendental equation determined by the topological properties of this multiply connected space.
Free Fermion Conditions and the Symmetries of Integrability
Authors: Viallet Claude-M.
Published: July 2002

We show that free-fermion conditions on vertex models amount to degeneration conditions for the inversion relations and the symmetries of the Yang-Baxter equations. We also show how solutions of the tetrahedron equations enjoy a similar property, and analyze the phenomenon.
A Quantum Field Theory Approach to Simple Liquids: The Elementary Excitations of Helium 4
Authors: Mele R. , Preparata G. , Villa S.
Published: July 2002

In the framework of Quantum Field Theory we propose a novel approach to the theory of bosonic simple liquids, formulated in terms of a scalar, complex quantum field, the wave-field Ψ(x,t). The problem is treated in a mean-field approximation, diagonalizing the quadratic part of the Hamiltonian à la Bogoliubov and calculating in a perturbative scheme the one-loop correction to the self-energy function. We derive the dispersion relation and the dynamic and static structure factors of the liquid 4 He , obtaining results that are successfully compared with experimental data.
Band Effects on Ion-Surface Charge Exchange
Authors: Souda Ryutaro
Published: July 2002

Various aspects of charge exchange between low-energy ions (10 eV–2 keV) and solid surfaces are discussed with particular emphasis placed on the effects of valence orbital hybridization on the electronic transition probabilities, and uniqueness of surface scattering relative to diatomic gas-phase collision is highlighted. Two classes of projectiles are explored, i.e. inert noble-gas ions and a reactive hydrogen ion. One or two core vacancies are created in noble-gas projectiles during collisions with specific target atoms, leading to (re)ionization and autoionization. In contrast to gas-phase collision, it is found that one-electron excitation predominates over simultaneous two-electron excitation. This result is basically ascribed to the band effect of energy-level crossing. Neutralization of the slow hydrogen ion at a surface is rather unique compared to the noble-gas ions and its probability is sensitively dependent upon ionicity of target atoms or the nature of the valence band. This is because a valence electron is captured via a new class of resonance neutralization which is mediated by a short-lived chemisorption state of hydrogen on a surface.
A New Method to Obtain U(J) Relationship in High Temperature Superconductor
Authors: Qin M. J. , Jin X. , Yao X. X. , Fu Y. X. , Rong X. S. , Ni Y. M.
Published: July 2002

An implicit expression for the time dependence of the current density J(t) is derived without the constant assumption of dU/dJ or , based on which a new method to extract U(J) relationship from magnetic relaxation data in high temperature superconductors is described. This method is applied to a melt textured growth YBa2Cu3O6+x sample and we obtain U(J)~ J-μ with μ=0.90 for H‖c, which is in accordance with that derived by the usual method suggested by Malery et al.(μ=0.87). Moreover, both methods give the same value of the constant C, which implies that the determination of C by the requirement of continuity of the U(J) curve at different temperatures is reliable. And the results U(J)~ J-μ by both methods are evidence for the collective pinning or the vortex glass theory.
A Derivation of Relativistically-Invariant Nonlinear Field Equations for Strongly Interacting Many-Body Systems
Authors: Tuszyński J. A. , Dixon J. M.
Published: July 2002

We re-examine the derivation of nonlinear field equations for a system of strongly interacting quasiparticles. Emphasis is placed on typical dispersion relations in the relativistic regime. Through Heisenberg's equations of motion for second-quantised operators we demonstrate that interacting many-body systems are described by a nonlinear Klein–Gordon type field equation. Its nonrelativistic equivalent was previously shown to be of the nonlinear Schrödinger type.
Electron–Interface–Phonon Interaction and Magnetopolaronic Impurity Transitions in Quantum Wells
Authors: Chen R. , Lin D. L.
Published: July 2002

The polaronic effect on the hydrogenic 1s–2p+ transition energy of a donor impurity located at the quantum well center in a double heterostructure is studied theoretically in detail. The electron–optical–phonon interaction Hamiltonian is derived on the basis of eigenmodes of lattice vibrations supported by the double heterostructure. Both the confined and interface phonon modes are included in the electron–phonon coupling. The transition energy is calculated as a function of the applied magnetic field for GaAs/Al 1-x Ga x As samples of well -widths d=125 Å, 210 Å and 450 Å by the second-order perturbation. Wide transition gaps are predicted around the two-level and three-level resonances for all three cases. It is found that the transition gap narrows with the increasing well-width but remains larger than the LO and TO phonon frequency difference for d=450 Å as is observed. We also perform the same calculation by assuming that the confined electron interacts with three-dimensional and two-dimensional phonon modes. The transition energy spectra from these calculations appear to be similar to those for a bulk sample, the spectrum splits at the resonance with the longitudinal optical phonon frequency only. From comparisons of our results with these calculations as well as with experiments, it is conclusively established that the wide gap of transition energy is solely due to the interface modes.
Time-Reversal Symmetry Breaking at Grain Boundaries in d-Wave Superconductors
Authors: Kuklov A. B. , Sigrist Manfred
Published: July 2002

Crystal lattice distortion can generate a superconducting state which breaks locally time-reversal symmetry by yielding a coupling between order parameters of different symmetry. The problem of a twist in the crystal lattice at a boundary between differently oriented grains is investigated by means of a generalized Ginzburg–Landau theory. It is shown that under certain conditions a time-reversal breaking state appears at the grain boundary. This state leads to a nontrivial phase shift in the Josephson effect across the grain boundary. This phase shift can be observed through a modified flux quantization (fractional fluxes) and phase slip effects.
Resistance Anomaly Near Superconducting Transition Temperature of Zr–Cu Metallic Glasses
Authors: Mondal A. K. , Roy S. K.
Published: July 2002

The theoretical analyses of the recent discovery of a new resistance anomaly in Zr–Cu superconducting metallic glasses with dilute magnetic impurities have been made. The resistance peaks are found to occur within 20–60 mK range above the resistive midpoint of the superconducting transition. The influence of Zr concentration on the peak has also been investigated. The results are in good qualitative agreement with the reported experimental findings.
Eigenstates of the Vorticity Operator: The Creation and Annihilation of Vortex States in Two Dimensions
Authors: Speliotopoulos A. D.
Published: July 2002

A quantum mechanical description of vortices in two-dimensional superfluid 4 He films is presented. Single vortex creation and annihilation operators are defined and wavefunctions for these states are explicitly constructed.
Nonequilibrium Transport and Population Inversion in Double Quantum Dot Systems
Authors: Zang Jun , Birman Joseph L. , Bishop A. R. , Wang L.
Published: July 2002

We present a microscopic theory for both equilibrium and nonequilibrium transport properties of coupled double quantum dots (DQD). A general formula for current tunneling through the DQD is derived by the nonequilibrium Green's function method. Using a Hartree–Fock approach, effects of multi-level coupling and nonequilibrium electron distributions in resonant tunneling are considered. We find that the peak in the resonant tunneling current through two symmetric dots will split only when the inter-dot coupling is stronger than dot-lead coupling. We predict that population inversion can be achieved in one dot in the nonequilibrium regime.
Surface Characterisation from Adsorbate Knight Shifts
Authors: Khanra Badal C.
Published: July 2002

Recent works on catalyst surface characterisation from adsorbate Knight shifts are reviewed. It has been shown how for supported catalysts the proton NMR gives a better estimate of the metal dispersion than the classical volumetric technique where the amount of hydrogen adsorbed is measured to determine the dispersion. It has also been shown that adsorption on multiple sites can be probed by the adsorbate Knight shifts. Again, for bimetallic systems the Knight shifts has been shown to indicate the composition of the surfaces. This has been corroborated by a microscopic theory using Friedel sum rule.

The role of promoters on active site blocking, the evaluation of kinetic parameters and the effect of segregation on the adsorption energy may also be found from NMR Knight shifts.

The works reviewed here concern generally hydrogen as an adsorbate. However, some work using 2 H , 13 C and 129 Xe NMR are also discussed. Deuterium NMR helps to find the kinetic parameters in exchange reaction and is complementary to the proton NMR in surface studies.

Similarly, Carbon-13 NMR helps to understand the organic reactions on metal surfaces as well as the surface structure of catalysts. 129 Xe NMR helps to understand the internal structure of zeolites.
Critical Slowing-Down of Spatially Nonhomogeneous Patterns in a Reaction–Diffusion Model
Authors: Castelpoggi Fernando , Wio Horacio S. , Zanette Damian H.
Published: July 2002

We exploit the concept of the nonequilibrium potential in order to analize the approach to stationary homogeneous and nonhomogeneous equilibrium states in a bounded bistable reaction-diffusion model. The analysis proceeds through the study of the Lyapunov functional, in terms of a control parameter -the threshold parameter ϕc-in the neighbourghood of a critical point (where a stable and an unstable pattern coalesce), that clearly shows the phenomenon of critical slowing-down in a spatially extended system.
Spatial Temperature Distribution Out of Doors
Authors: Ćirić D. M. , Tošić B. S.
Published: July 2002

The space-time dependence of temperature is analysed in the case of out of doors fire. It is assumed that the fire is caused by a series of point heat sources. The analytical expression of temperature has been found and the line of maximum temperatures, depending on the wind velocity, has been investigated.
On the Collective Mode Spectrum for Composite Fermions at 1/3 Filling Factor
Authors: Pérez Martínez Aurora , Cabo Alejandro , Guerra Valia
Published: July 2002

The collective mode spectrum of the composite fermion state at 1/3 filling factor is evaluated. The conductivity at zero momentum, the result coincides with the cyclotron energy at the external magnetic field value, and not at the effective field, in spite of the fact that only the former enter in the equations, thus, the Kohn theorem is satisfied. In place of a magneto-roton minimum, the collective mode gets a threshold indicating the instability of the mean field composite fermion state under the formation of crystalline structures. However, the question about if this outcome only appears within the mean field approximation should be further considered.
SU(m|n) Supersymmetric Calogero–Sutherland Model Confined in Harmonic Potential
Authors: Piguet C.-A. , Wang D. F. , Gruber C.
Published: July 2002

In this work, we study a continuous quantum system of a mixture of bosons and fermions with the supersymmetry SU (m|n). The particles are confined in a harmonic well and interact with each other through the 1/r2 interaction. An eigenstate of the Hamiltonian is constructed explicitly for the most general SU (m|n) case and its energy is given explicitly. It is argued that this eigenstate is the ground state of the system. Moreover, we construct some excited states giving an equally spaced spectrum. In the limiting case where there are no bosons in the system, our results reduce to those obtained previously.
Renormalization Group Approach to the One–Dimensional 1/4–Filled Hubbard Model with Alternating on–Site Interactions
Authors: Jackeli G. , Japaridze G.
Published: July 2002

The one-dimensional Hubbard model with different on-site interactions is investigated by renormalization group technique. In the case of a 1/4-filled band the dynamical nonequivalence of sites leads to the appearance of Umklapp processes in the system, and to the dynamical generation of a gap in the charge excitation spectrum for Ua≠Ub, Ua>0 or Ub>0. The ground-state phase diagram is obtained in the limit of second order renormalization. Depending on the sign and relative values of the bare coupling constants, there is a gap in the spin or charge excitation spectrum, and the model system tends to superconducting or antiferromagnetic order at T=0, with doubled period. The role of interaction between particles on nearest and next-nearest neighbor sites is also considered.
Phase Diagram and Orientational Order of a System with Second and Fourth Rank Interactions
Authors: Chiccoli Cesare , Pasini Paolo , Zannoni Claudio
Published: July 2002

A simple generalized Lebwohl–Lasher model for liquid crystals, where a fourth rank interaction is added to the usual second rank one, is investigated in detail. We have obtained the phase diagram of the system performing extensive Monte Carlo computer simulations for a range of the fourth to the second rank relative strengths and we compare it with the prediction of Mean Field and Two Site Cluster theories. We show that the addition of a non-negligible fourth rank term significantly changes the temperature dependence of the order parameter. Fourth rank contributions larger than 20% worsen the agreement of the model with the typical temperature behavior of the order in nematics.
A Theoretical Study on the Pressure Dependence of the Band Gap in ${\rm A^{I}B^{III}C^{VI}_2}$ Compounds
Authors: Asokamani R. , Mercy Amirthakumari R. , Pari G.
Published: July 2002

The self-consistent scalar relativistic band structure for AgGaX 2 (X = S, Se, Te) performed in chalcopyrite structure using the TBLMTO method at various pressures are reported here. Empty spheres were introduced in the calculations as the chalcopyrite structure is loosely packed. From the total energy calculations, the equilibrium lattice constant and the bulk modulus at zero pressure were calculated and these values agree well with the reported experimental values. All these compounds are found to have direct energy gap at ambient pressure with the gap widening with increased pressures which are in agreement with the experimental results. The deformation potential, dE g /dP for the compounds are also reported here. The metallisation volumes are calculated and the possibility of observing superconductivity in these compounds is discussed.
Design of Gates for Quantum Computation: The NOT Gate
Authors: Mozyrsky Dima , Privman Vladimir , Hotaling Steven P.
Published: July 2002

We offer an alternative to the conventional network formulation of quantum computing. We advance the analog approach to quantum logic gate/circuit construction. As an illustration, we consider the spatially extended NOT gate as the first step in the development of this approach. We derive an explicit form of the interaction Hamiltonian corresponding to this gate and analyze its properties. We also discuss general extensions to the case of certain time-dependent interactions which may be useful for practical realization of quantum logic gates.
Lattice-Gas Theory of Collective Diffusion in Adsorbed Layers
Authors: Danani A. , Ferrando R. , Scalas E. , Torri M.
Published: July 2002

A general theory for collective diffusion in interacting lattice-gas models is presented. The theory is based on the description of the kinetics in the lattice gas by a master equation. A formal solution of the master equation is obtained using the projection-operator technique, which gives an expression for the relevant correlation functions in terms of continued fractions. In particular, an expression for the collective dynamic structure factor S c is derived. The collective diffusion coefficient D c is obtained from S c by the Kubo hydrodynamic limit. If memory effects are neglected (Darken approximation), it turns out that D c can be expressed as the ratio of the average jump rate  and of the zero-wavevector static structure factor S(0). The latter is directly proportional to the isothermal compressibility of the system, whereas  is expressed in terms of the multisite static correlation functions gn. The theory is applied to two-dimensional lattice systems as models of adsorbates on crystal surfaces. Three examples are considered. First, the case of nearest-neighbour interactions on a square lattice (both repulsive and attractive). Here, the theoretical results for D c are compared to those of Monte Carlo simulations. Second, a model with repulsive interactions on the triangular lattice. This model is applied to NH 3 adsorbed on Re(0001) and the calculations are compared to experimental data. Third, a model for oxygen on W(110). In this case, the complete dynamic structure factor is calculated and the width of the quasi-elastic peak is studied. In the third example the gn are calculated by means of the discretized version of a classical equation for the structure of liquids (the Crossover Integral Equation), whereas in the other examples they are computed using the Cluster Variation Method.
Landau Theory of the Direct Smectic-A to Isotropic Phase Transition
Authors: Nandi B. , Saha M. , Mukherjee Prabir K.
Published: July 2002

Direct smectic-A to isotropic phase transition is studied by means of Landau theory. The theory predicts the first order behaviour of the smectic-A to isotropic phase transition. The temperature difference T AI -T* is also calculated from the scaling equation of state and compared with the nematic to isotropic phase transition
Molecular Mean Field Study on Even–Odd Effect in Discotic Liquid Crystals
Authors: Saha Jayashree , Ghose D. , Saha M.
Published: July 2002

The mean field model for rectangular lattice having herring-bone packing of tilted molecules has been extended to reproduce even–odd alternation in the transition temperatures in a discotic system by taking into account the specific change in layering interaction and molecular biaxiality for each member of a homologous series.
OPTIMAL SIZE FOR THE NANOCRYSTALLINE SEMICONDUCTOR AND EFFECTIVE EXPONENT IN THE QUANTUM CONFINEMENT MODEL
Authors: JOHRI G. K. , SHARMA RAJESH , JOHRI MANOJ , SAXENA SAUMYA , YOSHINO KATSUMI
Published: July 2002

An expression for the effective exponent of the size in the quantum confinement model to understand the mechanism of photoluminescence for various surface geometries in nanocrystalline semiconductor is formulated. An optimal size of the nanocrystalline semiconductor passivated with hydrogen is given in the range of 2.89 to 4.89 nm for all surface geometries. The lowest limit of the optimal size is reasonably closer to the experimental value.
INFERENCE OF ELECTRON CONFIGURATION AND ACTIVATION ENERGY OF SOLUTE ATOMS IN COPPER AND SILVER CONDUCTORS ON ELECTROMIGRATION VOID FORMATION
Authors: ZEHE A. , RAMÍREZ A.
Published: July 2002

It is shown that the kinetics of vacancy coagulation to macroscopic erosion voids in dilute crystalline metallic alloys depends strongly on the chemical nature of the solute element. In numerous published and the author's own electromigration data, it was found that the formation of erosion voids is suppressed if valence electrons of the matrix metal atom and the alloying (or impurity) atom sum up to an odd number. This is due to the formation and electronic charging state of vacancy-impurity pairs. Provided that activation energies of the solute elements are low compared to those of matrix atoms, stable vacancy-impurity pairs dominate and resist coagulation. At higher temperatures the number of pairs diminishes, weakening the mechanism of mutual Coulomb repulsion. Dilute copper and silver alloys are compared in the framework of the mentioned properties, giving copper a better chance for electromigration resistance than silver.
EXPERIMENT OF DIELECTRIC QUANTUM INTERFERENCE IN LOW-DOPED c-ORIENTED LaSrCuO FILM CRYSTAL
Authors: SUGAHARA MASANORI , ASAI JUN , FUKUTOMI MASASI
Published: July 2002

An experiment is made on the dielectric property of c-oriented low-doped La 2 - x Sr x CuO 4 thin film crystal. The film-thickness dependence of the electric polarization of the low-doped films shows a logarithmically cyclic positive and negative polarization change at "anomalous thicknesses" of the film. Interference patterns are observed around the anomalous thicknesses in the polarization-charge dependence of the ‖ c film "capacitance" by the measurement of the stored charge in equilibrium under step voltage application. These results are well explained based on the model of the quantum- Hall-effect-like state in the accumulated 2D planes.
QUANTUM INTERFERENCE OF ELECTRON SYSTEM IN 2D NETWORK OF CIRCULAR MOLECULAR ORBITS
Authors: SUGAHANA MASANORI , BOGOLUBOV NIKOLAI N.
Published: July 2002

Our theoretical study reports on the quantum interference effect expected to be found in the correlated state of the hole-doped electron system in 2D networks of circular molecular orbits, where the ground state of the system is described by a FQHE-like state. When the phase-correlation length λΘ is larger than the incompressibility length λQ, the system of tunneling-coupled 2 FQHE-like states shows the interference of the Josephson effect. On the other hand, when λQ > λΘ, the system shows a dielectric interference effect analogous to the superconductor junction. In the film crystal of a multi-layer structure of FQHE-like systems of low hole-doping, logarithmically cyclic negative-positive change of film capacitance is expected to appear at "anomalous thicknesses" of the film. Comparison of the theoretical results with the interference effect found in the dielectric measurement of film crystals of low-doped La 2 - x Sr x CuO 4 reveals quantitative agreement.
SLIDING MODE CONTROL OF CHAOS IN THE CUBIC CHUA'S CIRCUIT SYSTEM
Authors: JANG MING-JYI , CHEN CHIEH-LI , CHEN CHA'O-KUANG
Published: July 2002

In this paper, a sliding mode controller is applied to control the cubic Chua's circuit system. The sliding surface of this paper used is one dimension higher than the traditional surface and guarantees its passage through the initial states of the controlled system. Therefore, using the characteristic of this sliding mode we aim to design a controller that can meet the desired specification and use less control energy by comparing with the result in the current existing literature. The results show that the proposed controller can steer Chua's circuit system to the desired state without the chattering phenomenon and abrupt state change.
MODELING OF KINETICS OF STRAIN INDUCED DEGRADATION OF POLYMER ADDITIVES IN LUBRICANTS
Authors: KUDISH ILYA I. , AIRAPETYAN RUBEN G. , COVITCH MICHAEL J.
Published: July 2002

A kinetics problem for a degrading polymer additive dissolved in a fluid lubricant is studied. The polymer degradation may be caused by the combination of such lubricant flow parameters as pressure, strain rate, and temperature as well as lubricant viscosity and the polymer characteristics (dissociation energy, bead radius, bond length, etc.). A fundamental approach to the problem of modeling stress-induced polymer degradation is proposed. The polymer degradation is modeled on the basis of a kinetic equation for the density of the statistical distribution of polymer molecules as a function of their molecular weight. The existence and uniqueness of the solution to the initial-value problem for the kinetic equation is proven. Moreover, some properties of the solution are established. The integrodifferential kinetic equation for polymer degradation is solved numerically for a number of different input data. The effects of pressure, strain rate, temperature, and lubricant viscosity on the process of lubricant degradation are considered. The increase of pressure promotes fast degradation while the increase of temperature delays degradation. In some cases, the density of the molecular weight distribution function maintained in time its initial single-modal shape and in other cases it changed with time from a single-modal shape to a bi-modal shape. A comparison of numerically calculated molecular weight distributions with experimental ones obtained in bench tests showed that they are in excellent agreement with each other.
AN OPTIMIZATION-BASED DOMAIN DECOMPOSITION METHOD FOR A BONDED STRUCTURE
Authors: KOKO JONAS
Published: July 2002

We study an optimization-based, non-overlapping, domain decomposition method for a bonded structure theoretically and numerically. The problem is restated as a constrained minimization problem for which the objective functional controls the normal component of stresses across the interface and the constraints are equlibrium equations in subdomains represented by adherents. We show that the minimization problem has a unique solution. We propose a domain decomposition method, based on the conjugate gradient minimization algorithm, which converges theoretically, in a finite number of steps.
DEVELOPING COLLABORATIVE GOLOG AGENTS BY REINFORCEMENT LEARNING
Authors: LEITA IOAN ALFRED , PRECUP DOINA
Published: July 2002

We consider applications where agents have to cooperate without any communication taking place between them, apart from the fact that they can see part of the environment in which they act. We present a multi-agent system, defined in Golog, that needs to service tasks whose value degrades in time. Initial plans, reflecting prior knowledge about the environment, are expressed as Golog procedures, and are provided to the agents. Then the agents are trained using reinforcement learning, in order to ensure coordination both at the action level and at the plan level. This ensures better scalability and increased performance of the system.
AUTOMATIC GENERATION OF RULE-BASED SOLVERS FOR INTENTIONALLY DEFINED CONSTRAINTS
Authors: ABDENNADHER SLIM , RIGOTTI CHRISTOPHE
Published: July 2002

A general approach to implement propagation and simplification of constraints consists of applying rules over these constraints. However, a difficulty that arises frequently when writing a constraint solver is to determine the constraint propagation algorithm. In previous work, different methods for automatic generation of rule-based solvers for constraints defined over finite domains have been proposed1,2,3,4. In this paper, we present a method for generating rule-based solvers for constraint predicates defined by means of a constraint logic program, even when the constraint domain is infinite.
COEFFICIENTS OF HOMFLY POLYNOMIAL AND KAUFFMAN POLYNOMIAL ARE NOT FINITE TYPE INVARIANTS
Authors: JIN GYO TAEK , LEE JUNG HOON
Published: July 2002

We show that the integer-valued knot invariants appearing as the nontrivial coefficients of the HOMFLY polynomial, the Kauffman polynomial and the Q-polynomial are not of finite type.
EXPLICIT DESCRIPTION OF THE HOMFLY POLYNOMIALS FOR 2-BRIDGE KNOTS AND LINKS
Authors: NAKABO SHIGEKAZU
Published: July 2002

An explicit formula of the HOMFLY polynomial of 2-bridge knots and links is presented. As corollaries, some specific coefficient polynomials are described explicitly. Lastly, some examples are calculated, which are related to the classification problem of the 2-bridge knots and links by the HOMFLY polynomial.
COULOMB-MODIFIED EIKONAL MODEL ANALYSIS OF REFRACTIVE12C+12CELASTIC SCATTERING AT Elab= 240 AND 360MeV
Authors: KIM YONG JOO , CHA MOON HOE
Published: July 2002

We present the Coulomb-modified eikonal model by using a tangential velocity at the distance of closest approach. The Fraunhöfer oscillations observed in the elastic angular distributions of the12C +12C system at Elab= 240 and 360 MeV can be explained due to the strong interference between the near- and far-side scattering amplitudes. We have found that the strongly real and weakly imaginary potentials are required to describe the refractive12C +12C elastic scatterings at Elab= 240 and 360 MeV. The refractive pattern, dominated by the far-side component of the scattering amplitude, can be shown to be sensitive to the real part of optical potential at small radius. Introducing the tangential velocity, it is shown that the Coulomb-modified eikonal model satisfactorily reproduces experimental data concerning the refractive pattern in the angular distributions of the12C +12C system at Elab= 240 and 360 MeV.
ELASTIC SCATTERING AS A TEST OF DENSITY DISTRIBUTIONS IN 6He AND 8He
Authors: AVRIGEANU M. , ANAGNOSTATOS G. S. , ANTONOV A. N. , AVRIGEANU V.
Published: July 2002

Taking elastic scattering of 6,8 He on protons as an example, it is shown that the differences between density distributions coming from different models can be evaluated when scattering data of the nuclei involved are available for comparison. Microscopic elastic-scattering angular distributions have been calculated for incident energies <100A MeV by using the Tanihata and COSMA models for the density distributions of He nuclei, the M3Y-Paris effective NN interaction, and the Bray et al. imaginary part of the optical potential. The present microscopic angular distributions based on the Tanihata densities are in good agreement with the available experimental data and also similar to results of other theoretical calculations, showing the sensitivity of scattering to the density distributions of these helium isotopes.
STRUCTURE SIMULATION OF SPARSE SILICA AEROGELS
Authors: RICHTER K. , TIEN C. L.
Published: July 2002

Developed for the simulation of silica aerogel (an ultrafine structure of very high porosity) is a theoretical model that combines the concepts of percolation and cluster agglomeration. The model is formulated via a statistical growth algorithm. A set of probabilistic parameters determines the structural properties of the simulated porous medium and can be adjusted to match a wide spectrum of situations, including extremely sparse structures. The proposed model is discussed on the basis of Monte-Carlo simulations and renormalization theory. The fractal dimension of the simulated structure is in good agreement with the results of X-ray scattering experiments. This shows the potential of the proposed method for characterizing and analyzing structure-related physical properties of silica aerogels, like their extremely low thermal conductivity and extraordinary optical properties.
A CASCADE MODEL AND SCALING VIOLATIONS IN DEEP INELASTIC STRUCTURE FUNCTIONS
Authors: FIRAT-ACAR F. GÜLAY , HACINLIYAN AVADIS
Published: July 2002

A cascade model, using a splitting function based on a generalized Verhulst map, is introduced. It is demonstrated that phenomenological observations connected with scaling and departures from it in deep inelastic scattering can be explained by this simple model.
MAINTENANCE POLICIES FOR A TWO-UNITS SYSTEM: A COMPARATIVE STUDY
Authors: BARROS ANNE , GRALL ANTOINE , BÉRENGUER CHRISTOPHE
Published: July 2002

This paper considers the age-based maintenance of a two-identical components system with economic dependences. Two existing approaches are presented and compared. One is a maintenance policy of (N,n)-type. It is very close to the optimal policy among all possible policies but difficult to optimize: Policy Iteration Algorithm is needed. The aim of the paper is to investigate if there are cases for which a simpler policy than those of (N,n)-type can be sufficient in terms of maintenance cost. A second approach proposed in literature (derived from the time-based block replacement one) is simpler but not sufficient in any situations. Some numerical experiments and an analysis of the stochastic behavior of the two-identical components system allows us to propose a third policy (Policy P). This third maintenance plan is simplified from the second one. It compensates for its weak point which is to be very expensive when the cost of replacement for one component is close to the cost of replacement for both components. Moreover it is possible to generalize this third policy from a two-identical components system to a n-identical components system. The performances analysis of the policy is based on numerical experiments.
BOOLEAN MODELLING AND EVALUATION OF A MULTISTATE-COMPONENT SYSTEM
Authors: POURRET OLIVIER , COLLET JÉRÔME , BON JEAN-LOUIS
Published: July 2002

We propose a method for computing the unavailability of a multistate-component system. This method is based on the construction of a Boolean model of the system, which may be represented in the form of a fault-tree. It is proved that the evaluation is always conservative, and very accurate when the probabilities of the component failures are low.
A MODEL FOR MARKET CLOSURE AND INTERNATIONAL PORTFOLIO MANAGEMENT WITHIN INCOMPLETE INFORMATION
Authors: BELLALAH MONDHER , WU ZHEN
Published: July 2002

This paper presents of model of market closure in the management of international portfolios. We consider an investor holding a portfolio of domestic stocks and foreign stocks who faces market closure in the management of his portfolio. The investor's portfolio is affected by the exchange rate risk and different dynamics of the underlying assets during the period of trading and non-trading. The investor must determine the optimal proportions of his wealth to allocate to domestic stocks and foreign stocks during the market open and close periods. The paper investigates the effects of opening and closing on transactions demand of domestic and foreign stocks. The transactions demand at open and close periods in the securities markets are studied in the presence of information costs using the main concepts in Merton's (1987) model of capital market equilibrium with incomplete information. Using optimal control theory, we provide a solution in the general case and propose analytic solutions for the constant relative aversion utility functions. The model can be applied to solve several problems in financial economics in the presence of market closure.
INNER MARKET AS A 'BLACK BOX' OF PARAMETERS FOR THE ENTIRE MARKET
Authors: BELENKIY ARI
Published: July 2002

Each market has its singular characteristics. Its inner structure is directly responsible for the observed distributions of returns though this fact is widely overlooked. Presence of a specialist leads to doubling the tails. Price dynamics of a market where market-makers have mutual obligations (or friendship) is different from one without them.

After representing the inner market case we suggest how to analyze its structure. We show that its framework may provide explanation for various problems arising in some popular market models. Several inverse problems are formulated.
A NOTE ON THE PRICING OF INDEX AMORTISING RATE SWAPS IN A WORST-CASE SCENARIO
Authors: EPSTEIN D. , WILMOTT P.
Published: July 2002

The index amortising rate swap is an ideal candidate for valuation under a worst-case scenario. We price this illiquid contract using a non-probabilistic interest rate with uncertain parameters and then form a static hedge using liquid, market-traded swaps, to find an optimal price.
HARMONIC ANALYSIS ON CONFIGURATION SPACE I: GENERAL THEORY
Authors: KONDRATIEV YURI G. , KUNA TOBIAS
Published: July 2002

We develop a combinatorial version of harmonic analysis on configuration spaces over Riemannian manifolds. Our constructions are based on the use of a lifting operator which can be considered as a kind of (combinatorial) Fourier transform in the configuration space analysis. The latter operator gives us a natural lifting of the geometry from the underlying manifold onto the configuration space. Properties of correlation measures for given states (i.e. probability measures) on configuration spaces are studied including a characterization theorem for correlation measures.
FINDING THE BEAT: AN ANALYSIS OF THE RHYTHMIC ELEMENTS OF MOTION PICTURES
Authors: ADAMS BRETT , DORAI CHITRA , VENKATESH SVETHA
Published: July 2002

This paper presents a new study on the application of the framework of Computational Media Aesthetics to the problem of automated understanding of film. Leveraging Film Grammar as the means to closing the "semantic gap" in media analysis, we examine film rhythm, a powerful narrative concept used to endow structure and form to the film compositionally and enhance its lyrical quality experientially. The novelty of this paper lies in the specification and investigation of the rhythmic elements that are present in two cinematic devices; namely motion and editing patterns, and their potential usefulness to automated content annotation and management systems. In our rhythm model, motion behavior is classified as being either nonexistent, fluid or staccato for a given shot. Shot neighborhoods in movies are then grouped by proportional makeup of these motion behavioral classes to yield seven high-level rhythmic arrangements that prove to be adept at indicating likely scene content (e.g. dialogue or chase sequence) in our experiments. The second part of our investigation presents a computational model to detect editing patterns as either metric, accelerated, decelerated or free. Details of the algorithm for the extraction of these classes are presented, along with experimental results on real movie data. We show with an investigation of combined rhythmic patterns that, while detailed content identification via rhythm types alone is not possible by virtue of the fact that film is not codified to this level in terms of rhythmic elements, analysis of the combined motion/editing rhythms can allow us to determine that the content has changed and hypothesize as to why this is so. We present three such categories of change and demonstrate their efficacy for capturing useful film elements (e.g. scene change precipitated by plot event), by providing data support from five motion pictures.
MOTION SEGMENTATION BY SUBSPACE SEPARATION: MODEL SELECTION AND RELIABILITY EVALUATION
Authors: KANATANI KENICHI
Published: July 2002

Reformulating the Costeira–Kanade algorithm as a pure mathematical theorem, we present a robust segmentation procedure, which we call subspace separation, by incorporating model selection using the geometric AIC. We then study the problem of estimating the number of independent motions using model selection. Finally, we present criteria for evaluating the reliability of individual segmentation results. Again, model selection plays an important role. We confirm the effectiveness of our method by experiments using synthetic and real images.
PERFORMANCE MEASURES FOR ASSESSING CONTOUR TRACKERS
Authors: TISSAINAYAGAM PRITHIRAJ , SUTER DAVID
Published: July 2002

In this paper we present techniques to compare the quality of tracking performances of B-spline based contour trackers. Three trackers reported to give good tracking performance have been considered for our empirical evaluation. They are the CONT-IMM tracker, the Condensation tracker and the Baumberg's tracker. Four different test conditions were set and for each test, the tracking performance of each tracker was measured against four performance measures. The results presented have revealed some interesting findings about the performance of the trackers under various conditions.
NOVEL ADAPTIVE FILTERING TECHNIQUE FOR THE PROCESSING OF ELECTROGASTROGRAM
Authors: SELVAN S.
Published: July 2002

The electrogastrogram measured cutaneously by attaching electrodes to the abdominal skin contains considerable noise. An attempt is made to develop an efficient adaptive filtering technique suitable for real time processing of electrogastrogram. A novel technique combining both adaptive noise cancellation and adaptive signal enhancement in a single recurrent neural network is proposed. To compare its performance, adaptive noise cancellation and cascaded connection of adaptive noise cancellation and adaptive signal enhancement are employed. Recurrent neural networks using Real Time Recurrent Learning (RTRL) algorithm are employed for implementing the all the above systems. An attempt is made to alleviate the computational burden imposed by RTRL algorithm by employing pruning of weights.
FIRST PASSAGE TIME STATISTICS FOR SYSTEMS DRIVEN BY LONG RANGE CORRELATED GAUSSIAN NOISES
Authors: ROMERO ALDO H. , SANCHO J. M. , LINDENBERG KATJA
Published: July 2002

We examine the mean first passage time for a particle driven by highly correlated Gaussian fluctuations to reach one or more predetermined boundaries. We discuss a numerical algorithm to generate power-law correlated fluctuations and apply these to three physical examples. One is the arrival of a free particle at either end of an interval. The second is the decay of a particle from an unstable state. The third is the time for a particle to cross a barrier separating one well from another in a double well potential. In each case, a comparison with the first passage time for a particle driven by Gaussian white noise is presented, as is an analysis of the dependence of the first passage time properties on the correlated noise parameters.
SIMULATION OF THERMAL NOISE IN SCALED MOSFETS
Authors: SPEDO SERGIO , FIEGNA CLAUDIO
Published: July 2002

In this work, hydrodynamic device simulations and a post-processor for the simulation of noise in MOSFETs are applied in order to evaluate the impact of scaling on the thermal noise of transistors representative of technologies with minimum gate length scaled from 0.25 μm down to 0.1 μm. The dependences on bias and technology scaling of the spectral densities of the equivalent drain- and induced gate-noise currents are anayzed in details. The effect of technology scaling on the two-port noise parameters of the intrinsic MOSFET is studied as well. The results of this work confirm that the transistor's noise performance tend to improve as the technology is scaled down, making CMOS a suitable technological option for the implementation of advanced low-power RF systems.
Collection statistics for fast duplicate document detection
Authors: Chowdhury Abdur , Frieder Ophir , Grossman David , McCabe Mary Catherine
Published: July 2002

We present a new algorithm for duplicate document detection that
uses collection statistics. We compare our approach with the
state-of-the-art approach using multiple collections. These
collections include a 30 MB 18,577 web document collection
developed by Excite@Home and three NIST collections. The first NIST
collection consists of 100 MB 18,232 LA-Times documents, which is
roughly similar in the number of documents to the
Excite&at;Home collection. The other two collections are both 2
GB and are the 247,491-web document collection and the TREC disks 4
and 5---528,023 document collection. We show that our approach
called I-Match, scales in terms of the number of documents and
works well for documents of all sizes. We compared our solution to
the state of the art and found that in addition to improved
accuracy of detection, our approach executed in roughly one-fifth
the time.
Consistency maintenance in real-time collaborative graphics editing systems
Authors: Sun Chengzheng , Chen David
Published: July 2002

The following abstracts are from recent issues and the forthcoming issue of ACM's
Transactions of Computer Human Interaction
(ToCHI). They are included here to alert
interactions'
readers to what research is being done in the field of Computer Human Interaction. The complete papers, when published, can be found in ACM's Digital Library at www.acm. org/pubs/contents/journals/tochi/2002-9/#1.