bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURE AND DYNAMICS OF CRYSTALLINE C60·n-PENTANE CLATHRATE
Authors: Faigel G. , Tegze M. , Pekker S. , Kemény T.
Published: November 2004

Clathrate type single crystals with the composition of C 60(n- C 5 H 12)0.88( C 7 H 8)0.05 were grown from C 60-toluene-petroleum ether solution. The structure of the crystals, determined by X-ray diffraction is b-face centered orthorhombic. A phase transition is observed at 190 K by differential scanning calorimetry.
AUTOIONIZATION AND AUGER SPECTRA OF C60 FILMS: IMPLICATIONS FOR CHARGE SCREENING AND TRANSPORT
Authors: Brühwiler P.A. , Maxwell A.J. , Mårtensson N.
Published: November 2004

We have measured the spectator autoionization shift of C 60 near the C 1s threshold, and compared it to the Coulomb correlation energy U found by another spectroscopic method. We find that the U we obtain is smaller by a factor of 30% than a prior result, due to a calibration difference. The spectator shift can be comparable to U , with a value that decreases as the excited electron wavefunction becomes more diffuse. This indicates that screening effects vary drastically with molecular orbital.
SCREENED INTERACTION AND COULOMB PSEUDO-POTENTIAL IN C60
Authors: Gunnarsson O. , Rainer D. , Zwicknagl G.
Published: November 2004

We study the screening for C 60 in the random phase approximation. For a free molecule we find a substantial reduction of the interaction between close atoms but an “antiscreening” of the interaction between distant atoms. For a C 60 solid there is an efficient screening of the intraband Coulomb interaction (U~0.05 eV ), leading to µ=UN(0)~0.4, where N(0) is the density of states per spin and molecule. We then study the renormalization of the Coulomb pseudo-potential µ* due to higher subbands in a simple two-band model. We find that the renormalization is small, although a traditional approach, summing ladder diagrams in the screened interaction, predicts a large renormalization. This suggests that µ* may not be much smaller than µ~0.4 in C 60. To obtain reasonable transition temperatures, Tc, this value of μ* (~0.4) requires values of the electron-phonon coupling constant λ, which are not very much larger than what has been calculated.
RAMAN SCATTERING AND SUPERCONDUCTIVITY OF AxC60
Authors: Mitch M.G. , Chase S.J. , Lannin J.S.
Published: November 2004

Raman scattering measurements of line width variations in A x C 60 ultrathin films provide detailed information on vibrational coupling of H g or A g modes relevant to superconductivity. In situ, UHV studies of 400A thick Rb 3 C 60 and K 3 C 60 films indicate somewhat similar behavior, suggesting the predominance of low frequency H g (2) radial modes for electron-phonon coupling. Measurements of nonsuperconducting Na x C 60 in ultrathin films, in contrast, yield reduced line broadening effects for H g (8) and H g (2) modes relative to Rb and K materials.
RELATION BETWEEN THE SUPERCONDUCTIVITY AND ELECTRON SPIN RESONANCE ON DOPED C60
Authors: KINOSHITA N. , TANAKA Y. , TOKUMOTO M. , MATSUMIYA S.
Published: November 2004

Superconducting transition of Cs-doped C60 is observed at about 29 K along with those of the already reported K- and Rb-doped C 60. ESR studies have been carried out on alkali-metal (K, Rb, Cs)-doped C 60 and relations between the superconductivity and the observed ESR properties are reported.
ELECTRODYNAMICS OF A ROTATING BODY: RELATIVISTIC THEORY OF CIRCULAR AND AXIAL BIREFRINGENCE
Authors: EVANS M. W.
Published: November 2004

The theory of the electrodynamics of a rotating body is used to show that there exists: 1) circular birefringence of purely relativistic origin, composed of dispersive aether drag and residual, ensemble averaged, magnetization; 2) non-relativistic circular birefringence due to the angular velocity of the body in the observer frame; 3) non-relativistic axial birefringence in chiral media due to the angular velocity of the body; 4) second order, relativistic equivalents of 2) and 3).
TOWARD A CONFORMAL FIELD THEORY FOR THE QUANTUM HALL EFFECT
Authors: NAGAO GREG
Published: November 2004

An effective Hamiltonian for the study of the quantum Hall effect is proposed. This Hamiltonian, which includes a "current-current" interaction has the form of a Hamiltonian for a conformal field theory in the large N limit. An order parameter is constructed from which the Hamiltonian may be derived. This order parameter may be viewed as either a collective coordinate for a system of N charged particles in a strong magnetic field; or as a field of spins associated with the cyclotron motion of these particles.
EXPERIMENTAL FINITE-SIZE SCALING IN THE QUANTUM HALL EFFECT
Authors: KOCH S. , HAUG R.J. , KLITZING K. v. , PLOOG K.
Published: November 2004

The critical exponent ν of the localization length in the integral quantum Hall regime can be measured directly using small Hall-bar geometries with different sizes. We obtain a universal behaviour for the three lowest Landau levels. This is in agreement with the universality prediction of the field-theoretic approach to the metal-insulator-transition in the quantum Hall effect. The value of ν=2.3±0.1 agrees with recent numerical studies for the lowest Landau level. We review recent experimental findings on the basis of these results and discuss the situation in Landau levels where spin-splitting is not resolved.
TIME REVERSION OF PROCESSES IN DISSIPATIVE SYSTEMS
Authors: ZMITRENKO N.V. , KURDYUMOV S.P.
Published: November 2004

It is shown that a process running in a dissipative system described by continuum equations may be organized so that the system under compression and heating will pass through a sequence of states the same as those occur in this system under rarefaction and cooling, but in the reverse time order. In the model reconstructed for such a process, the boundary regimes on the piston have a special form where the adiabatic exponent γ in the “forward” and “backward” motion of the medium are connected by a certain relation.
ALLOY PHASE FORMATION BY MECHANICAL ALLOYING: CONSTRAINTS AND MECHANISMS
Authors: MA E. , ATZMON M.
Published: November 2004

Alloy phase formation in binary metallic systems by mechanical alloying (MA) of elemental powders is briefly reviewed. Our recent results indicate the inadequacy of the current understanding of the MA process, which has been depicted as an isothermal solid-state interdiffusion reaction under interfacial, metastable, equilibrium in layered composites. A structural and thermodynamic analysis of the supersaturation followed by amorphization in the Zr-Al system demonstrates that a system can be constrained to be a single phase without reaching two-phase (metastable) equilibrium during MA. Alloying, resulting in a single metastable phase, has also been achieved in immiscible systems with positive heat of mixing, such as Fe-Cu. In both cases, the interfacial free energy associated with a repeatedly deformed, fine-structured, two-phase alloy appears to pose polymorphous constraints. In addition, equilibrium phases can be formed during MA in an exothermic, self-sustained fashion, as observed for the formation of AlNi. Al-Ni phases formed under different milling conditions suggest that self-sustained reactions may occur, undetected, on a grain-by-grain basis.
BELL FUNCTIONAL INTEGRAL FOR GAS OF STRINGS
Authors: BOTELHO LUIZ C.L.
Published: November 2004

We generalize the Bell functional integral representation for a statistical ensemble of strings with two-body interaction.
SYNTHESIS OF NEARLY-PURE 2223 PHASE Tl2Ba2Ca2Cu3O10 WITH Tc ABOVE 120 K FROM 2223 STARTING COMPOSITION
Authors: SHENG Z.Z. , GU D.X. , XIN Y. , LI Y.F. , PEDERSON D.O.
Published: November 2004

Nearly-pure 2223 phase Tl 2 Ba 2 Ca 2 Cu 3 O 10 with zero-resistance temperature of 120 K or higher was synthesized for the first time from 2223 starting composition using a Ba 2 Ca 2 Cu 3 O 7 precursor method in a half-closed system. The results from resistance and ac susceptibility measurements and powder X-ray diffraction analyses are presented. The optimal preparation condition is heating at about 900° C for about 48 hours. This optimal condition actually produces the true composition of the “2223” phase.
A STUDY OF THE STABILITIES AND SUPERCONDUCTIVITIES OF THE SUPERSTRUCTURE IN YBa2Cu3O6+x SYSTEM (0 < x < 1)
Authors: WANG QIANG , RUSHAN HAN , YIN D. L. , GAN Z. Z.
Published: November 2004

We calculated the Madelung potentials of a set of possible oxygen ordering superstructures of YBa 2 Cu 3 O 6+x system by using the standard Ewald method. According to the Madelung potential criteria on cations and anions, it is easy to present the possible stable superstructures. Furthermore, the density of carriers (hole or electron) for each superstructure was obtained and the superconductivities discussed.
ELECTRON CHARGE DENSITY DISTRIBUTION IN A SURFACE JELLIUM POTENTIAL BY THE INVARIANT IMBEDDING METHOD
Authors: POON H. C. , HOWE P. T.
Published: November 2004

The Friedel's formula for spherically symmetric potential1 is generalized to the case of a jellium surface potential. The scattering coefficients due to the surrounding potential as a function of position are first found by using the invariant imbedding method. The electron charge distribution at any point near the surface is then expressed in terms of these scattering coefficients in a form similar to the Friedel's formula. Results for electron density profile due to various types of surface potentials are presented. Possible generalization to a more complete surface band structure calculation method is also discussed.
CHROMATIC ABERRATION OF SINGLE-POLE PROJECTOR LENSES
Authors: ALAMIR A. S. A.
Published: November 2004

The chromatic aberration of magnetic projector lenses is divided into axial aberration and chromatic field aberration. Analytical expressions for chromatic aberration coefficients of the spherical field model which is useful for the study of single-pole magnetic lenses are given.
ONE DIMENSIONALITY OF DEUTERON VELOCITY DISTRIBUTION FOR CLUSTER-IMPACT FUSION
Authors: KIM YEONG E. , YOON JIN-HEE , RICE ROBERT A. , RABINOWITZ MARIO
Published: November 2004

In cluster-impact fusion, the width of the proton energy spectrum gives information about the temperature of the fusing deuterons, and its shape reflects the dimensionality of their velocity distribution. The observed symmetrical spectrum implies a one-dimensional distribution, whereas a three-dimensional distribution would result in a skewed spectrum. One dimensionality implies either extremely rapid thermalization in the beam direction, or the possibility of beam ion fusion.
ON THE PREDICTION OF FERROMAGNETISM AND METAMAGNETISM IN 4d TRANSITION-METAL OVERLAYERS
Authors: ERIKSSON OLLE , ALBERS R. C. , BORING A. M. , FERNANDO G. W. , COOPER B. R.
Published: November 2004

We present theoretical evidence for ferromagnetism in Ru and Rh overlayers on Ag(001). These predictions are based on ab-initio, spin-polarized, electronic-structure calculations within the framework of the local spin-density approximation. For Tc, Ru, Rh and Pd overlayers chemisorbed on Ag(001), only Ru and Rh exhibited ferromagnetism. Several metamagnetic spin states were found for the Ru overlayers.
THE CRITICAL BEHAVIOR OF SINE-GORDON MODEL
Authors: LIU YI-MIN , PU FU-CHO , SU HANG
Published: November 2004

Using the algebraic Bethe Ansatz and Euler-Maclaurin formulae, we calculate the finite-size corrections to the energy and momentum of ground and excited states for the sine-Gordon model. The conformal anomaly, operator dimension and critical coupling parameter are given in the ultraviolet limit.
LOW DENSITY HUBBARD MODEL IN TWO AND THREE DIMENSIONS
Authors: YU. KHLEBNIKOV S.
Published: November 2004

We consider two- and three-dimensional repulsive Hubbard models at low density, using the gas approximation. The large-U three-dimensional model is shown to behave as a Fermi liquid and the corresponding two-particle scattering length is found. In the two-dimensional case we find that the gas approximation is inconsistent, as indicated by an isolated pole of the two-particle Green function below the occupied states in the upper half-plane. This behaviour is specific to the lattice system as opposed to the continuum two-dimensional Fermi gas with short-range repulsion.
DISORDER EFFECTS IN WEAK ITINERANT ELECTRON FERROMAGNETS
Authors: MISHRA SURESH G. , PAI RAMESH V.
Published: November 2004

A review of the effect of diffusive motion of electrons on various low temperature thermal and magnetic properties of weak itinerant ferromagnetic alloys is given.
QUANTUM OPTICS IN NMR SPECTROSCOPY
Authors: EVANS M. W.
Published: November 2004

A circularly polarised laser is shown to produce a static magnetic field, Bπ, in its axis of propagation. The field Bπ is expressed in quantum optical form and is shown to interact with a nuclear dipole moment to produce a real interaction energy which produces a frequency shift in a standard NMR spectrum. The observed shift is two orders of magnitude smaller than that predicted with a classical Bπ. This is explained qualitatively using the fact that the classical Bπ produces an interaction energy which is the upper bound of the energy produced by the quantised [Formula: see text]. The quantum field in NMR appears to behave quite differently, therefore, from its classical counterpart.
TO THE COLORED-LOSS-NOISE DYE-LASER MODEL WITH ADDITIVE NOISE TERM BELOW THRESHOLD
Authors: SOLDATOV A. V.
Published: November 2004

A single-mode colored-loss-noise dye-laser model with additive spontaneous emission noise term is treated by a new version of approximate effective Fokker–Planck equation which is proved to be valid below at and above threshold. Particular attention is paid to the dye-laser operation below threshold, where the additive noise term seems to play irreplaceable role in the context of the above mentioned model, preventing collapsing of the system to the vacuum state.
A REVIEW OF THE HYDROGEN REDUCTION OF RUBY AT MEGABAR PRESSURE
Authors: RUOFF ARTHUR L.
Published: November 2004

It is shown that the available optical data on composites of hydrogen and Al 2 O 3 are an indirect proof of the presence of metallic Al formed in the reaction Al 2 O 3 + 0.75 H 2 = 1.5 AlOOH + 0.5 Al at 177 GPa. The AlOOH (diaspore) Raman peak for the OH stretching mode is not strong and is very broad. This unfortunately eliminates one direct method of showing that the reaction proceeds. It is shown that recent arguments attempting to show that Al does not form at high pressure are invalid.
QUANTUM STOCHASTIC HEISENBERG EQUATION
Authors: SAITO T. , ARIMITSU T.
Published: November 2004

By extending the quantum stochastic Liouville equation formulated by one of the authors (T. A.) within Non-Equilibrium Thermo Field Dynamics (NETFD), it is shown that, by means of stochastic Heisenberg equation, one can construct a unified framework of stochastic differential equations for quantum systems with the quantum white noise of non-thermal ensemble. A new aspect is given to deal with the difficulties attending quantum Langevin equations.
SUPPRESSION OF THE FERROMAGNETIC STATE BY DISORDER IN THE KONDO LATTICE
Authors: CRIŞAN M. , POPOVICIU C.
Published: November 2004

The ferromagnetic ground state of a Kondo lattice with a low concentration of conduction electrons is ferromagnetic. Assuming the existence of disorder in the Fermi liquid of the conduction electrons we showed that the ferromagnetic state can be suppressed by the effect of the spin fluctuations of the disordered Fermi liquid.
AXIAL ELECTROMAGNETIC FORCE DENSITY IN MPD THRUSTERS
Authors: SHESHADRI T.S.
Published: November 2004

An MPD thruster formulation involving coupled aerothermodynamic-electromagnetic equations and including viscous effects is developed and solved. The electromagnetic force density distribution in the thruster interior is studied. Axial force densities are found to be largest on the cathode longitudinal surface. Very large force densities are found at the cathode upstream end and this is attributed to large values of the Hall parameter. Over the rest of the cathode longitudinal surface, axial force densities increase with increasing inlet velocities and mass densities and larger plasma viscosities. Equivalent increases in inlet velocity and mass density produce effects of different magnitudes.
MACROSCOPIC QUANTUM TUNNELING IN A SUPERCONDUCTING RING CONTAINING A WEAK SUPERCONDUCTING JUNCTION
Authors: EXTREMERA A.
Published: November 2004

Macroscopic quantum effects in SQUIDs are discussed. An equation describing the behavior of the superconducting ring in the harmonic approximation is reduced to the standard form of Mathieu’s equation. For well-defined flux states, good agreement with exact theoretical calculations and experimental results is found near the minimum energy regions. We establish the effective dissipation dependence on tunneling rate via the “instanton” or “bounce” action. WKB-type approximations enable us to obtain the quantum decay rate for a metastable state in the anharmonic (quartic) potential.
DETERMINATION OF SPONTANEOUS CURVATURE AND INTERNAL PRESSURE OF VESICLES AND RED CELLS BY THEIR SHAPE AND THE FLEXOELECTRIC EFFECT OF MEMBRANE
Authors: ZHONG-CAN OU-YANG , JIAN-GUO HU , JI-XING LIU
Published: November 2004

Three geometric relations for vesicle equilibrium within the Helfrich elasticity model have been derived. The relations can serve to determine the spontaneous curvature c0 and cell internal pressure −Δp=pin−pext from the vesicle shape. In analogy with the theory of the flexoelectric effect of nematic liquid crystals we have also obtained a relation between c0 and the membrane potential. By applying these predictions to the human red blood cell (RBC) shape measured by Evans and Fung we found good agreement of the calculated potential with measured values previously given by other biologists by direct impaling RBC with a microelectrode. The calculated value of the internal pressure is discussed by comparison with previous works.
MORE ON FINITE TEMPERATURE ANYON SUPERCONDUCTIVITY
Authors: LEBLANC Y. , WALLET J.C.
Published: November 2004

In the framework of finite temperature linear response theory, we analyze to a greater extent the nature of anyonic superconductivity. Using identities among Laguerre polynomials and Bessel functions, we provide simple and useful expressions for the response function in the form of high temperature expansions. The physical penetration depth as well as the Landau-Ginzburg coherence length are calculated for all temperatures. We find that for statistics restricted by n≪450, anyon superconductors are type II local (London) superconductors at low temperature and type I non-local (Pippard) superconductors at high temperature. The threshold temperature is also obtained.
COLLECTIVE EFFECTS IN RESONANCE PROPERTIES OF A SYSTEM OF N TWO-LEVEL ATOMS
Authors: DAT NGUYEN NHU
Published: November 2004

We consider resonance properties of an assembly of N two-level atoms interacting with an intense photon beam. The atoms are assumed to be noninteracting with each other except via the action of the electromagnetic field. Using the phase representation of the radiation field and the boson description of the atom system we calculate the one-photon resonance frequency for two kinds of the system: a beam of atoms moving with uniform velocity and a Boltzmann atom gas. The resonance frequency shift is found to be dependent on the total number of atoms and the initial preparation of the atom system. Numerical results show that the collective shift is of the same magnitude as the Bloch-Siegert one.
ZERO FIELD EXCESS CONDUCTIVITY STUDIES IN THE Bi-Sr-Ca-Cu-O SYSTEM
Authors: RAVI S. , BAI V. SESHU
Published: November 2004

The excess conductivity (∆σ) data on several samples of 85 K phase and 110 K phase of Bi-Sr-Ca-Cu-O system were fitted to a sum of direct (AL) and indirect (MT) contribution of fluctuation induced excess conductivity, in the mean field region. The samples of the 85 K phase are of compositions Bi2Sr2CaCu2Oy, Bi2Sr2CaCu2Ag0.8Oy, and Bi2Sr2.14Ca0.86Cu2Oy with Tc (zero) of 78.9 K, 86.5 K and 81.8 K respectively. The two samples of 110 K phase with composition Bi1.2Pb0.3Sr1.5Ca2Cu3Oy were prepared from nitrate and citrate routes respectively and have Tc (zero) of 105.3 K and 102.9 K. We find from our analysis relatively strong pair-breaking effects in both 85 K and 110 K phases, indicating the contribution of Maki-Thompson term to the excess conductivity to be rather insignificant. The average value estimated for the phase-breaking time for the 85 K and 110 K phases are (3.7±0.5)×10−16s and(11.3±1.6)×10−16s respectively, at 100 K.
DYNAMICS OF FLUXONS IN PERTURBED LONG JOSEPHSON JUNCTIONS
Authors: GONZÁLEZ JORGE A.
Published: November 2004

The dynamics of fluxons in systems perturbed by inhomogeneous external forces and nonlinear damping is investigated.
THE DISPERSIVE DIFFUSION OF ATOMS IN DISORDERED SOLIDS
Authors: HALPERN V.
Published: November 2004

The experimental results on the dispersive diffusion of atoms in disordered solids cannot be explained by conventional diffusion theory. The random trap model is also shown to be irrelevant to the experimental situation, but the random bond problem is more promising. The accurate analysis of this model requires important and non-trivial extensions to customary percolation theory. Numerical simulations of the model could prove of great value in determining its relevance to the experimental results.
NONLINEAR AND CHAOTIC OSCILLATIONS IN SEMICONDUCTORS UNDER THE INFLUENCE OF A TRANSVERSE MAGNETIC FIELD: THE DYNAMIC HALL EFFECT
Authors: HÜPPER G. , SCHÖLL E. , REIN A.
Published: November 2004

The dynamic Hall effect is presented as a novel model for transverse magnetic field induced oscillatory instabilities in semiconductors. Comprehensive account is given of the theoretical derivation of nonlinear dynamic magnetotransport properties of hot electrons, a linear stability analysis, and nonlinear simulations for a variety of materials with positive or negative differential conductivity in the regime of low-temperature impurity breakdown. Periodic, chaotic, and intermittent voltage oscillations and period-doubling scenarios as a function of current or magnetic field are found under dc bias.

The physical mechanism rests upon the dielectric relaxation of both drift and Hall field, coupled with impurity impact ionization.
SUPPRESSION OF SUPERCONDUCTIVITY AND STRUCTURAL CHANGES IN R1-xPrxBa2Cu3O7-y (R=Sm, Gd, Er, Tm, Y)
Authors: LIU P. , ZHU W. J. , ZHANG J. L. , GUO S. Q. , JIA S. L. , ZHAO Z. X.
Published: November 2004

The compounds R 1-x Pr x Ba 2 Cu 3 O 7-y ( R = Sm , Gd , Er , Tm and Y ) have been prepared and examined for superconductivity and structural changes. It is observed that the superconducting transition temperature Tc of R 1-x Pr x Ba 2 Cu 3 O 7-y decreases monotonically with increasing Pr concentration for all systems. At constant Pr concentration, Tc decreases approximately linearly with increasing radius with R cations while the lattice constants a,b,c and unit cell volume V increase. The correlation of both the Tc and the lattice constants with the radius of R cations is the same as for 1:2:4, 2:4:7, and 1:2:1:2 compounds.
NUCLEAR RELAXATION RATES, PENETRATION DEPTH, AND ENERGY-DEPENDENT GAP FUNCTIONS IN HIGH-Tc SUPERCONDUCTORS
Authors: LI Q. P. , JOYNT ROBERT
Published: November 2004

We study the experimental consequences of a gap function which is odd in energy. This type of gap may occur in high temperature superconductors. We show that nuclear spin relaxation experiments can be used to probe the "particle-hole parity" of a gap function. We find that an exponent α=1/3 which characterizes the energy dependence is in agreement with the currently available experimental data of both the nuclear spin relaxation rate (∝T(2-α)/α) and the electromagnetic penetration depth (∝T(1-α)/α).
LIGHTNESS CONSTANCY FROM LUMINANCE CONTRAST
Authors: SKRZYPEK JOSEF , GUNGNER DAVID
Published: November 2004

To discount effects of uneven illumination we have designed and tested a neural network that can adaptively control light sensitivity at the photosensor level. Our neural network architecture simulates the ON channel response of the visual system using multiple layers of hexagonally arranged nodes having partially overlapping receptive fields of different spatial frequencies. Feedforward connections are excitatory while feedback pathways subserve lateral inhibition. The outputs of these nodes are combined so as to maximize the signal to noise ratio while providing constant feedback that resets photosensor thresholds to maintain high sensitivity. A sparse primitive interpolation technique was applied to the ensemble output of the sensitivity control module to determine if it sufficiently encodes surface reflectance. The motivation is to determine to what extent the ratio principle, as captured by the sensitivity control system, explains the lightness constancy phenomenon and whether information contained within an ON channel response is adequate to reconstruct the surface lightness. Our connectionist architecture can account for many characteristics attributed to the lightness constancy phenomenon observed in biological systems. The results suggest that our module maintains high sensitivity across a large range of intensities without interfering with the transmission of visual information embedded in the spatial discontinuities of intensity. However, the amplitude of the luminance derivative as encoded in ON channel responses is not sufficient to approximate surface reflectance.
MIXED FINITE ELEMENT BASED NEURAL NETWORKS IN VISUAL RECONSTRUCTION
Authors: SUTER D.
Published: November 2004

This paper shows how visual reconstruction problems can be solved using analog networks resulting from the reformulation of the reconstruction problem into a series of coupled sub-problems. A novel analog implementation based upon Platt's constraint networks is suggested for neural network implementation and the effectiveness is demonstrated with examples. The complete approach bears a philosophical similarity to the Harris Coupled Depth-Slope model of visual reconstruction. Significant differences appear, though, in the Lagrangian formulation, the mixed finite element discretization, and the analog implementation. It is also shown that the resulting networks can be structurally different from those suggested by Harris.
THREE DIMENSIONAL OBJECT PATTERN REPRESENTATION BY ARRAY GRAMMARS
Authors: WANG P. S. P.
Published: November 2004

A formal model for three-dimensional object representation is introduced. It uses parallel techniques and significantly reduces the time required for dealing with three-dimensional image analysis problems. Its fundamental properties are investigated and several interesting examples are illustrated.
LEARNING OF PATTERN AND PICTURE LANGUAGES
Authors: SIROMONEY RANI , SUBRAMANIAN K. G. , MATHEW LISA
Published: November 2004

A method of learning pattern languages in time polynomial in the length of the pattern is introduced. The learning of certain picture languages can then be done by considering them as an interpretation of pattern languages. The learning of Tabled Regular k-Matrix languages describing arrays of symbols is also examined.
REPLICATED IMAGE ALGORITHMS AND THEIR ANALYSES ON SIMD MACHINES
Authors: NARAYANAN P. J. , DAVIS LARRY S.
Published: November 2004

Data parallel processing on processor array architectures has gained popularity in data intensive applications, such as image processing and scientific computing, as massively parallel processor array machines became feasible commercially. The data parallel paradigm of assigning one processing element to each data element results in an inefficient utilization of a large processor array when a relatively small data structure is processed on it. The large degree of parallelism of a massively parallel processor array machine does not result in a faster solution to a problem involving relatively small data structures than the modest degree of parallelism of a machine that is just as large as the data structure. We presented data replication technique to speed up the processing of small data structures on large processor arrays. In this paper, we present replicated data algorithms for digital image convolutions and median filtering, and compare their performance with conventional data parallel algorithms for the same on three popular array interconnection networks, namely, the 2-D mesh, the 3-D mesh, and the hypercube.
THE DEPTH AND MOTION ANALYSIS MACHINE
Authors: FAUGERAS OLIVIER D. , DERICHE RACHID , MATHIEU HERVE , AYACHE NICHOLAS , RANDALL GREGORY
Published: November 2004

In this article, we describe some of the algorithms for depth and motion analysis which have been developed within ESPRIT project 940. Specifically we discuss edge detection, token tracking in sequences of images, and trinocular stereo. These processes have been implemented in hardware to form the core of the Depth and Motion Analysis (DMA) machine which has been developed to provide sophisticated real time vision capabilities for a large variety of robotics tasks.
STEALTH TERRAIN NAVIGATION FOR MULTI-VEHICLE PATH PLANNING
Authors: TENG Y. ANSEL , DEMENTHON DANIEL , DAVIS LARRY S.
Published: November 2004

In this paper, we propose a method for solving visibility-based terrain path planning problems for groups of vehicles using data parallel machines. The discussion focuses on path planning for two groups of vehicles so that they move in a bounding overwatch manner. Furthermore, the planned paths for the vehicles themselves are subject to intervisibility constraints, configuration constraints, and different terrain traversabilities due to variations in terrain type and slope. A spatial-temporal sampling approach is adopted to discretize the solution space and facilitate fast computation on a data parallel machine. One of the key computations in the planning is the region-to-region visibility analysis, which is computationally expensive but essential to the choice of subgoals to carry out reconnaissance activities. A parallel algorithm for this analysis is developed. By reducing the communication complexity, our algorithm achieves much faster running time than traditional methods. The algorithms are implemented on a Connection Machine CM-2, and the experimental results show that the planning system effectively generates good paths.
RECENT ADVANCES IN MACHINE LEARNING
Authors: KODRATOFF YVES
Published: November 2004

Inference is a very general reasoning process that allows us to draw consequences from some body of knowledge. Machine learning (ML) uses the three kinds of possible inferences, deductive, inductive, and analogical. We describe here different methods, using these inferences, that have been created during the last decade to improve the way machines can learn. We have already presented the most classical approaches in a book (Kodratoff, 1988), and in several review papers (Kodratoff, 1989, 1990a, 1992). These results will be described here very briefly, in order to leave room for newer results. We include also genetic algorithms as an induction technique. We restrict our presentation to the symbolic aspects of connectionism.

A learning system can also be viewed as a mechanism skimming interesting knowledge out of the flow of information that runs through it. We present several existing learning systems from this point of view.
RECOGNIZING NOISY PATTERNS VIA ITERATIVE OPTIMIZATION AND MATCHING OF THEIR DESCRIPTIONS
Authors: BALA J. W. , PACHOWICZ P. W.
Published: November 2004

This paper presents an approach to the recognition of noisy patterns. We assume that learned concept descriptions contain noisy components. These descriptions can be optimized to gain better performance through the elimination of some less significant noisy components. Parametric control of such an optimization, however, is very difficult and a parameter value has to be found through the training process. This value can change over concept variations and time, and in consequence, it can decrease the system recognition effectiveness. We found that the classification decision can be based on the dynamic characteristics of the recognition curve acquired over increasing degree of optimization. In this approach, the optimization and matching steps are repeated iteratively. The dynamic characteristics of recognition curves are completed and a pattern of each recognition curve is labeled. For a given set of test data, the system selects recognition curves of uptrend patterns (when the recognition rate increases with the increase of the optimization degree), and the final classification is made for the class which has the highest recognition rates among selected uptrend recognition curves. Thus, the method classifies data based on a series of matches that determines the behavior of the recognition curve instead of the traditional single match. The effectiveness of the proposed methodology is illustrated on the example of specially prepared very noisy texture attributes.
DIAGNOSIS WITH CONTINUOUS AND DISCRETE CAUSAL RELATIONSHIPS: KNOWLEDGE REPRESENTATION
Authors: CHU BEI-TSENG B.
Published: November 2004

Most present research on diagnostic reasoning has dealt with discrete causal relationships. However, continuous causal relationships are frequently encountered in many applications, particularly in equipment/instrument diagnostic applications. This paper offers an integrated model of discrete and continuous causal relationships based on probability theory. Four types of continuous and discrete causal relationships are identified. For each type of causal relationship the following issues are addressed: its semantics and causation strength based on probability theory, and how causation strength can be acquired. It is also demonstrated that causation probabilities for continuous causal relationships can be derived based on classical statistical theory and Bayesian probability theory. It will be shown in a companion paper that the knowledge representation framework presented in this paper can be used in causal network-based diagnostic inference models.
ROBUST AND ADAPTIVE SEGMENTATION OF NOISY IMAGES USING GIBBS RANDOM FIELD MODELS
Authors: WANG TAO , ZHUANG XINHUA , XING XIAOLIANG
Published: November 2004

A robust and adaptive algorithm for segmenting a noisy image is presented. The original (or noise-free) images are modeled by an underlying Gibbs random field (GRF) or equivalently by a Markov random field (MRF), and the driving noise is a mixture of an additive independent Gaussian noise and an outlier process. The processes of maximum a posteriori (MAP) segmentation and maximum-likelihood (ML) estimation for the image model parameters are carried out simultaneously. Both procedures, which are based on stochastic relaxation algorithms with a simulated annealing technique, are efficiently implementable on parallel architectures, such as artificial neural networks.

Our proposed method is adaptive in that it recursively segments the noise-corrupted images and estimates the model parameters necessary for the segmentation procedure. We should emphasize that the proposed algorithm is robust in eliminating the effect caused by outliers. Finally, a number of computer simulation experiments are given to demonstrate the robustness and effectiveness of the recursive algorithm.
A GRAPHICS ACCELERATOR FOR HIDDEN SURFACE REMOVAL AND COLOR SHADING
Authors: BAE SEONG-OK , BANG KYUNG-IL , KYUNG CHONG-MIN
Published: November 2004

In this paper, we describe a special purpose hardware called ESEU (Expandable Shading Engine Unit) for fast rendering of 3-D scenes using Gouraud shading model. Each ESEU has three major functional blocks: linear interpolator, multipliers and Edge Painting Tree. Linear interpolator with coupled binary tree structure yields the functional values at all pixels within each zone (zone denotes the smallest interval which encompasses the given span and consists of 2n successive pixels in the x-direction, where n is some integer) by interpolating the functional values, such as z-depth values or color intensities, at the left and right end points of the zone which are calculated by the multipliers. Mask pattern for the removal of data for the pixels outside the original span but within the corresponding zone is generated by the Edge Painting Tree. Since there are no interconnections among ESEU’s, graphics system with any screen size can be easily built using a multitude of the prototype ESEU’s. A prototype ESEU in this work handles 64 pixels; therefore, 16 ESEU’s are required for screens having a 1024-pixel width. The bit-serial nature of the prototype ESEU is suitable for its VLSI implementation at a reasonable cost.
PROVABLY SECURE KEY-UPDATING SCHEMES IN IDENTITY-BASED SYSTEMS
Authors: SHINOZAKI SHINJI , FUJIOKA ATSUSHI , TSUJII SHIGEO , ITOH TOSHIYA
Published: November 2004

In this paper, we present Key-Updating Schemes in identity-based (identification or signature) systems, and consider the security of the schemes. We propose two kinds of key-updating schemes, i.e., one is sequential and the other is parallel, and show that both schemes are equivalent to each other in a polynomial time sense, i.e., there exists a deterministic polynomial time algorithm that transforms the sequential key-updating scheme to the parallel one, and vice versa. We also show that even if any polynomially many entities conspire to find a secret-key of any other entities, both key-updating schemes are provably secure against polynomially many times key-updating if decrypting RSA is hard.
A CONTINUOUS DEFORMATION ALGORITHM FOR DC-ANALYSIS OF ACTIVE NONLINEAR CIRCUITS
Authors: VANDENBERGHE LIEVEN , VANDEWALLE JOOS
Published: November 2004

Globally convergent homotopy methods for solving nonlinear resistive circuits exploit eventual passivity of the components and are therefore not suited for active circuits. This paper describes a possible extension of the octahedral algorithm to make it applicable to a broad class of active circuits. It is also shown how the algorithm can be used to find multiple solutions.
DIAGNOSIS OF t/s-DIAGNOSABLE SYSTEMS
Authors: DAS A. , THULASIRAMAN K. , AGARWAL V.K.
Published: November 2004

A t/s-diagnosable system permits diagnosis of faulty units within a set of s units provided the number of faulty units does not exceed t. A characterization of t/s-diagnosable systems is presented. This characterization is then used to develop an efficient algorithm for diagnosis of t/s-diagnosable systems. It is noted that a useful modification of the algorithm can be used for fault diagnosis of sequentially t-diagnosable systems.
A HIGH SPEED HAAR TRANSFORM IMPLEMENTATION
Authors: ALBANESI M.G. , FERRETTI M.
Published: November 2004

This paper presents an implementation of the Haar transform suitable for VLSI integration. It shows how to map a bidimension linear transformation, which has a straightforward multiresolution realization on a pyramid data-parallel computer, onto a pipeline of simple processors. A further simplification of the linear structure leads to an extremely simple implementation based on a two-stage pipeline, capable of processing images as large as 1024×1024 pixels. VLSI simulations with current technologies predict HDTV video rates. Data compression is among the applications that benefit from the new formulation of the transform.
PERFORMANCE OF NEURAL ALGORITHMS FOR MAXIMUM-CUT PROBLEMS
Authors: URAHAMA KIICHI
Published: November 2004

The author previously developed a new neural algorithm effective for set-partitioning combinatorial optimization problems by extending the logistic transformation used in the Hopfield algorithm into its multivariable version. In this letter the performance of the algorithm is theoretically evaluated and it is proved that this algorithm is 1/p-approximate for p-partitioning maximum-cut problems.
ORDER AND CHAOS IN THE TORAL LOGISTIC LATTICE
Authors: ABRAHAM RALPH H. , CORLISS JOHN B. , DORBAND JOHN E.
Published: November 2004

Cellular dynamical systems, alias lattice dynamical systems, emerged as a new mathematical structure and modeling strategy in the 1980s. Based, like cellular automata, on finite difference methods for partial differential equations, they provide challenging patterns of spatiotemporal organization, in which chaos and order cooperate in novel ways. Here we present initial findings of our exploration of a two-dimensional logistic lattice with the Massively Parallel Processor (MPP) at NASA's Goddard Space Flight Center, a machine capable of 200 megaflops per second. A video tape illustrating these findings is available.
GENERIC PATTERNS OF BIFURCATION GOVERNING ESCAPE FROM POTENTIAL WELLS
Authors: STEWART H. B. , THOMPSON J. M. T. , LANSBURY A. N. , UEDA Y.
Published: November 2004

Extensive numerical simulations have established the generic character of patterns of bifurcation governing the escape of a forced oscillator across a smooth potential barrier and the close relation with the familiar nonlinear resonance within a potential well. Subtle but significant differences are found, depending on whether the damping is high or low, and the differences are related to the problem of experimentally determining the optimal escape condition.
RE-ENTRANT ROTATING WAVES IN A BEELER–REUTER BASED MODEL OF TWO-DIMENSIONAL CARDIAC ELECTRICAL ACTIVITY
Authors: COURTEMANCHE MARC , WINFREE ARTHUR T.
Published: November 2004

Propagation of cardiac electrical activity is simulated in a two-dimensional sheet of cells using the cable equation and the Beeler–Reuter membrane model for ventricular muscle cells. Re-entrant patterns are produced using the original Beeler–Reuter equations and two modified versions involving changes in the calcium and sodium channel dynamics. Both stable rotating waves and irregular activity are observed. The model is shown to exhibit conduction block due to stationary repolarization fronts. The origin and properties of these fronts are described.
ESTIMATING DIMENSIONS WITH CONFIDENCE
Authors: JUDD KEVIN , MEES ALISTAIR I.
Published: November 2004

Estimation of correlation and other fractal dimensions is a favored approach for investigating whether time series or other dynamical data may be produced by nonlinear deterministic systems. The standard methods have disadvantages which are widely recognised; briefly put, an estimate is always produced, with no indication of its reliability or likely error. By assuming an explicit geometrical model for an attractor, we are able to produce a better estimator and to give a form of weak confidence intervals. Experience so far indicates that this approach is much less likely to give misleading answers than the conventional ones.
NONLINEAR DYNAMICS OF SELF-SYNCHRONIZING SYSTEMS
Authors: DE SOUSA VIEIRA M. , LICHTENBERG A. J. , LIEBERMAN M. A.
Published: November 2004

We investigate the self-synchronization of nonlinear systems. The particular system considered is two-coupled, digital phase-locked loops. It is shown that the overall dynamics is far more complicated than that of a single loop, which is governed by a one-dimensional circle map. In the case of two-coupled loops, we observe that the dynamics is governed by explicit mapping equations only for certain regions of the parameter space. In the regions for which mapping equations can be derived, we find the universality class of the coupled loops. Using such a two loop system as a transmitter of a chaotic signal, it is shown how a third loop can synchronize with this signal. Our results may provide one possible solution to the problem of secure communications.
THE DIFFERENTIAL GEOMETRY OF SCROLL WAVES
Authors: TYSON JOHN J. , STROGATZ STEVEN H.
Published: November 2004

Traveling waves of excitation organize physical, chemical, and biological systems in space and time. In the biological context they serve to communicate information rapidly over long distances and to coordinate the activity of tissues and organs. An example of particular beauty, complexity and importance is the three-dimensional rotating scroll wave observed in the Belousov–Zhabotinskii reaction and in the ventricle of the heart. A scroll wave rotates around a filamentous phase singularity that weaves through the three-dimensional medium. At any instant of time the geometry of the scroll wave can be reduced to the spatial arrangement of a ribbon whose edges are the singular filament and the tip of the scroll wave. This ribbon, when it closes on itself, must satisfy the topological constraint L = Tw + Wr, where L is the linking number of the two edges of the ribbon, Tw is the total twist of the ribbon, and Wr is the writhing number of the singular filament. We discuss the origin of this equation and its implications for scroll wave statics and dynamics.
BICRITICAL DYNAMICS OF PERIOD-DOUBLING SYSTEMS WITH UNIDIRECTIONAL COUPLING
Authors: KUZNETSOV A. P. , KUZNETSOV S. P. , SATAEV I. R.
Published: November 2004

The simplest case of bicritical behavior arises in a system of two logistic maps with unidirectional coupling in the point of a parameter plane where lines of transition to chaos in both subsystems meet. We develop a renormalization group analysis of the bicriticality and find the corresponding fixed point universal function and constants featuring the scaling properties of the second system while the first one is in the Feigenbaum critical state. Fractal properties of the bicritical attractor and its quantitative characteristics (σ-functions, f(α)-spectra, generalized dimensions) are considered. It is shown that the bicriticality may be observed as well in lattice models of flow systems consisting of more than two coupled elements.
SAMEA: OBJECT-ORIENTED SOFTWARE MAINTENANCE ENVIRONMENT FOR ASSEMBLY PROGRAMS
Authors: CHEN S. , TSAI W. T. , CHEN X. P.
Published: November 2004

This paper presents a software maintenance environment for assembly programs, SAMEA. It presents an object-oriented database support for displaying, understanding, modifying and configuring assembly programs for software maintenance. Understanding of assembly programs is based on the theory of explicit representation of various structural and functionality elements of code and multiple relationships among them. Modification of program is based on an object-oriented incremental editor and a set of rules to check the correctness of instruction format.

The characteristics of SAMEA are: integration of multiple tools, on-line information, ease of adoption of new tools, and finally, support of software maintenance activities such as program understanding, ripple effect analysis, and program redocumentation. The ripple effect of a contemplated change is the parts of the code that need to be reexamined for possible modification.

Assembly code elements and relations among code elements are represented as objects in SAMEA which is built on top of an object-oriented database GemStone. SAMEA consists of 26K lines of C code and 4K lines of GemStone code. We have successfully populated 18K lines of BAL code in SAMEA.
KNOWLEDGE-BASED SUPPORT FOR REQUIREMENTS ENGINEERING
Authors: BOLTON DAVID , JONES SARA , TILL DAVID , FURBER DAVID , GREEN STEWART
Published: November 2004

Approaches to providing knowledge-based support for the process of requirements engineering are discussed. The kinds of knowledge commonly used in providing such support are placed within a taxonomy and the approaches of different projects to the definition and representation of each of these kinds of knowledge are considered. Finally, there is a brief review of the ways in which each kind of knowledge is used in various approaches to providing support for commonly recognized stages in the process of requirements engineering. It is concluded that knowledge-based techniques are at present capable of providing significant support for the requirements engineer, but that a considerable amount of work has still to be done before the potential of these techniques can be fully realized.