bluuebunny/crossref_metadata_2025 huggingface dataset:
BASIS FOR SYNTHESIS OF SPIRAL LATTICE QUASICRYSTALS
Authors: BURSILL L. A. , RYAN GEORGE , FAN XUDONG , ROUSE J. L. , PENG JULIN , PERKINS ANNE
Published: November 2004

Observations of the sunflower Helianthus tuberosus reveal the occurrence of both Fibonacci and Lucas numbers of visible spirals (parastichies). This species is multi-headed, allowing a quantitative study of the relative abundance of these two types of phyllotaxis. The florets follow a spiral arrangement. It is remarkable that the Lucas series occurred, almost invariably, in the first-flowering heads of individual plants. The occurrence of left-and right-handed chirality was found to be random, within experimental error, using an appropriate chirality convention.

Quantitative crystallographic studies allow the average growth law to be derived (r = alτ−1; θ = 2πl/(τ + 1), where a is a constant, l is the seed cell number and τ is the golden mean [Formula: see text]). They also reveal departures from classical theoretical models of phyllotaxis, taking the form of persistent oscillations in both divergence angle and radius. The experimental results are discussed in terms of a new theoretical model for the close-packing of growing discs. Finally, a basis for synthesis of (inorganic) spiral lattice structures is proposed.
Hcl MEASUREMENT AND NONLINEAR MAGNETIZATION BEHAVIOR IN SINGLE-CRYSTAL Bi2Sr2CaCu2Oy
Authors: YANG G. , CHEN G. H. , YAN Y. F. , NI Y. M. , ZHENG D. N. , JIA S. L. , YANG Q. S. , ZHAO Z. X.
Published: November 2004

H c1 (T) values near T c for the field along the c direction of single crystal Bi 2 Sr 2 CaCu 2 O y are obtained from the magnetization measurements at low field. The nonlinear behavior of magnetization just above H cl are discussed with a model of pinning and dissipative flux creep.
RAMAN SCATTERING STUDY OF Ag+-IMPLANTED β-ALUMINA CRYSTALS
Authors: FENG YIPING , ZHANG MINGSHENG , HU GONGJIAN , CHEN QIANG
Published: November 2004

We have measured Raman spectra of sample of sodium β-alumina and samples with silver ion implantation where one kind of sample was not annealed after the implantation, and the others were Ag +-implanted with annealing for 30 minutes at 300, 400, 500 and 700°C, respectively. Raman spectra show that silver ion implantation disturbs sublattice of Na + in β-alumina with some disorder features and some resonance modes appeared in the Raman spectra. We have found the critical annealing temperature near 400°C, above which the silver ion, typically with small activation energy 0.18 eV, gains enough energy to diffuse rapidly through the vacancy clusters formed by silver ion implantation and also through the conduction plane of crystal between clusters in β-alumina with high ionic conductivity.
A NEW HIGH-Tc SUPERCONDUCTOR YBa2Ca2Cu3Ox
Authors: SHIMA A. , SHOJI T. , UKAKU M. , WATANABE Y. , TAZAWA Y. , SAKAI H.
Published: November 2004

We report that the high temperature superconductivity observed in a new ceramic Y–Ba–Ca–Cu oxide compound which exhibited the onset of superconductivity clearly at above 90 K and became completely superconductive at liquid nitrogen temperature (77 K).

Powder X-ray diffraction analysis showed that the crystal structure of this new superconductor had the same one as a YBa 2 Cu 3 O x.
MAGNETIC PROPERTIES OF SUPERCONDUCTING nMBa2Cu3Ox:Ag (M = Y, Gd, and Eu) COMPOSITES
Authors: HUANG C. Y. , LI T. J. , YAO Y. D. , GAO L. , HUANG Z. J. , SHAPIRA Y. , McNIFF E. J. , WU M. K.
Published: November 2004

We measured the M-H hysteresis loops of n YBa 2 Cu 3 O x: Ag (n = 3, 5, and 7) and 3RBa 2 Cu 3 O x: Ag (R = Gd and Eu) as a function of temperature, and found that the residual magnetization and, hence, pinning is independent of n and the rare-earth ions (R and Y), but depends greatly on the processing conditions. These samples exhibit the strongest pinning force for high-temperature superconductors developed to date.
A GINZBURG-LANDAU THEORY FOR CRITICAL TEMPERATURE OF LAYERED HIGH-Tc SUPERCONDUCTORS
Authors: NAGAO TATSUYA , MORI HIROYUKI , YONEZAWA FUMIKO
Published: November 2004

Using a phenomenological model for layered superconductors, we derive a formalism for the critical temperature T c in terms of the layer numbers. We show that T c of a system of n identical layers is the same as that of a single layer for all values of n. In a periodic layered structure composed of two kinds of layers, T c increases monotonically with the number of higher-T c layers. When the carrier number depends on structure, T c shows a behavior consistent with the experimental data on some high-T c superconductors such as Tl and Bi families. We make a suggestion to achieve a higher T c .
MELT PROCESSING OF YBaCuO SUPERCONDUCTORS AND CRITICAL CURRENTS
Authors: MURAKAMI MASATO
Published: November 2004

In the Y–Ba–Cu–O system, the superconducting phase is produced by a peritectic reaction: Y2 BaCuO 5(211) + L → 2YBa 2 Cu 3 O x (123). In order to promote the continuous growth of the 123 phase, uniform distribution of 211 in the liquid is required. In this review, I first present the melt process which enables us to achieve fine dispersion of 211 in the liquid. Large 123 crystals can be grown from this precursor structure by slow cooling in temperature gradient. As a result of incomplete peritectic reaction, the crystals contain fine 211 inclusions. The fine dispersion of 211 inclusions in the 123 matrix is considered to have three beneficial effects: 1) to suppress crack formation; 2) to promote oxygen diffusion; and 3) to provide pinning centers.

Such crystals exhibit large J c values exceeding 104 A/cm 2 at 77 K and 1 T according to both transport and magnetic measurements. Magnetization measurements also show that the critical state model is established in the sample indicating that no weak-link is present. Flux creep rate is reasonably small compared to that of single crystals. Attainable J c due to the 211 inclusions is estimated based on the conventional flux pinning theory.

Finally, I propose the application of such crystals as a superconducting permanent magnet.
INVESTIGATION OF SUPERCONDUCTIVITY IN Y–Sr–Cu–O
Authors: SURYANARAYANAN R. , BALIGA S. B. , JAIN A. L. , GOROCHOV O.
Published: November 2004

Preparation, X-ray diffraction (XRD), resistivity (ρ) and magnetic susceptibility (χ) of YSrCuO y (nominal composition) synthesized at 1200°C are reported. XRD data indicate more than one phase. Zero resistivity is observed at 72 K. The field cooled χ indicates a superconducting transition at 68 K and also an anti-ferromagnetic transition at 15 K which could be due to Y 2 Cu 2 O 5. These data confirm the earlier observations of Wu et al.5 who have, however, observed a higher T c at 85 K which could be due to a higher temperature used for synthesis.
CORRELATION BETWEEN ELECTRIC CHARGING OF THE SAMPLE SURFACE AND KINETICS OF OPTICALLY STIMULATED EXOELECTRON EMISSION (OSEE) FROM CRYOSOLIDIFIED NaCl SOLUTION
Authors: GIEROSZYŃSKI A.
Published: November 2004

It was found that OSEE kinetics from electron bombarded cryosolidified NaCl solution, depend on electric charging of the sample surface.

It was shown that from the relationship between the maximum surface potential and the parameters of OSEE kinetic, intensities of electric fields in the emitter layer could be estimated.

It is supposed that nonhomogeneous electric fields existing in the emitter surface region, influence the emission levels responsible for the course of OSEE kinetics.
THE SELF CONSISTENT COHERENT POTENTIAL APPROXIMATION TO THE HUBBARD MODEL
Authors: CORRIAS MASSIMO
Published: November 2004

We introduce, by an exact formula for the double occupancy probability δ in the Hubbard model, a self consistent version of the CPA which is aimed at taking into better account correlations of the electrons motion. We show that CPA breaks down at large values of the interaction strength, and we suggest a way of overcoming this limitation along the lines of the model proposed here.
CONVERGENT BEAM ELECTRON DIFFRACTION STUDY OF Bi-BASED HIGH TEMPERATURE SUPERCONDUCTING LAYERED COMPOUNDS
Authors: ZHANG X. F. , YAN Y. F. , FUNG K. K.
Published: November 2004

Cleaved specimens of layered compounds Bi 2 Sr 2( CaCuO 2)n CuO 6, n = 0, 1 and 2 phases have been studied by convergent beam electron diffraction. The identity and the symmetry of the phases have been determined from the higher order Laue zone (HOLZ) rings and the symmetry of their [001] patterns. In the case of Bi 2 Sr 2 CuO 6, the [001] axial periodicity corresponds to the component of the wave vector of the monoclinic modulation along the c axis. Widely different axial periodicities have been obtained. This is interpreted as the manifestation of the variation of the monoclinic modulation. The presence of basal stacking fault lowers the symmetry of the [001] pattern.
EFFECT OF MAGNETIC FIELD ON THE PERFECTION OF MCZ SILICON
Authors: MAI Z. H. , CUI S. F. , WANG C. Y. , WU L. S. , LI H. P. , CHEN G. X. , ZHOU S. R. , YE S. C.
Published: November 2004

n-type and p-type MCZ silicon grown under different magnetic field strengths and different pulling rates compared with the CZ silicon were investigated by means of X-ray topography, micro-region infrared absorption, infrared microscopy, optical microscopy and spreading resistance, etc. The experimental results show that the MCZ method can provide high quality silicon crystals with a low oxygen concentration, uniform distribution of dopant and good thermal stability, leading to low thermal donor generation.
210 K ULTRASONIC AND SPECIFIC HEAT ANOMALIES IN THE (Bi0.85Pb0.15)2Sr2Ca2Cu3O10+x SUPERCONDUCTORS
Authors: HE YUSHENG , XIANG JIONG , ZHANG JINCANG , HE AISHENG , CHANG FANGAO , LI FUXUE
Published: November 2004

Ultrasonic study on single phase ( Bi 0.85 Pb 0.15)2 Sr 2 Ca 2 Cu 3 O 10+x revealed that there are isothermal-like anomalies near 210 K in both velocity and attenuation of longitudinal and transverse sound waves. Specific heat measurements also showed clear anomaly at about 210 K, suggesting the occurrence of some structural changes or phase transition. Comparing with YBa 2 Cu 3 O 7−y, possible mechanisms are discussed.
PLASMA SPRAY DEPOSITED SUPERCONDUCTING Y-Ba-Cu-OXIDE COATINGS
Authors: ROHR S. , ECKART G. , BÄCHER I. , SCHLÄFER U. , SCHNEIDER L. , MÜLLER R. , TERESIAK A. , VERGES P.
Published: November 2004

The properties of YBa 2 Cu 3 O 6+x thick films, deposited by plasma spraying of reacted powders in Ar atmosphere, are determined as a function of powder properties, conditions of post-annealing process and substrate materials. The relations between the electrical resistivity near critical temperature, the chemical composition and structure of the films in their as-sprayed and annealed states were investigated by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and metallography.
ON THE EFFECTIVE THEORY OF A BCS SYSTEM AT ZERO TEMPERATURE
Authors: SCHAKEL ADRIAAN M.J.
Published: November 2004

A microscopic derivation is given of the recently proposed effective action of a BCS-type system at zero temperature.
A TIME QUASI-CRYSTAL
Authors: MACKAY ALAN L.
Published: November 2004

The great attention recently devoted to quasi-crystals has popularised the method of showing quasi-periodicity by the cut and projection of a regular lattice, plotting each of the periodicities on a separate axis. The date of Easter can be seen in this light.
EXTRINSIC SYMMETRY-BREAKING EFFECT ON ELECTRO-OPTICS OF LIQUID CRYSTALS
Authors: LEE SIN-DOO , PATEL J.S.
Published: November 2004

It is demonstrated that the symmetry-breaking of interfacial interactions between two surface layers in liquid crystals can produce a polar electro-optic effect. In a simple geometry with homogeneous boundary conditions, it is found that the magnitude of this polar effect is directly proportional to the difference in the anchoring strength between two aligning surface layers.
DERIVATION OF GIBBS STATES FORM QUANTUM FIELD THEORY
Authors: SYROS C.
Published: November 2004

A Lorentz invariant and Hermitian statistical field theory is presented. Its derivation is based on the random field theory, the evolution operator and the path integration. It yields the density matrix, the Gibbs states and the temperatures for equilibrium, nonequilibrium and variable particles numbers states. The chemical potential follows from a spontaneous energy renormalization of the Hamiltonian in the evolution operator. The generalization to any field other than scalar fields is straightforward.
LOCAL SCALING PROPERTIES OF FRACTALS OBSERVED IN Ni-Zr ALLOY FILMS
Authors: DING J.R. , WANG F. , LIU B.X.
Published: November 2004

Wavelet transform was performed based on the fractals observed in Ni-Zr alloy films during ion irradiation. The mass distribution measure and the Laplacian potential gradient measure were used to study the local scaling properties of the ion-induced fractals. The strength of singularities at each point was calculated according to the wavelet transform. The densities of the strength of singularities were also deduced and compared with the f-α spectra yielded by multifractal analysis. The results showed that the ion-induced fractals had a wide range of strength of singularities.
STM STUDY OF POLYCRYSTALLINE COPPER
Authors: OSHIO T. , SAKAI Y. , EHARA S.
Published: November 2004

Grain boundaries and their electric potential were studied in connection with the electric conduction in polycrystalline copper using a scanning tunneling microscope (STM). It was found that the grain boundaries consist mainly of cuprous oxide ( Cu 2 O ) and electric potential barriers are formed at most grain boundaries.
EDGE EXCITATIONS IN THE FRACTIONAL QUANTUM HALL STATES AT GENERAL FILLING FRACTIONS
Authors: WEN X.G.
Published: November 2004

We propose a scheme to construct the edge states for the Fractional Quantum Hall (FQH) states obtained by the Jain’s scheme. The low energy effective theory of the edge excitations is obtained. We calculate the number of the branches and the electron propagators of the edge states for various FQH states. We demonstrate that two FQH states with the same filling fraction may have different topological orders and may support different edge excitations.
THE KINKED VORTICES IN LAYERED SUPERCONDUCTORS IN THE PRESENCE OF A TILTED MAGNETIC FIELD
Authors: IVLEV B.I. , OVCHINNIKOV YU. N. , POKROVSKY V.L.
Published: November 2004

In highly layered high-Tc superconductors in the presence of a magnetic field having an angle with respect to the planes, a system of vortex kinks is a more appropriate description of the structure than a set of rectilinear vortices. This description leads to a finite jump of the sample torque at zero angle between planes and magnetic field direction, to the nontrivial behaviour of the ratio at the perpendicular and parallel magnetization, and to strong anisotropy of the critical current.
ON THE ROLE OF THE TIO LAYERS IN THE THALLIUM HIGH Tc SUPERCONDUCTORS
Authors: EAB C.H. , TANG I.M.
Published: November 2004

The roles of the thallium mono and bi layers in the superconducting series TlBa 2 Ca n−1 Cu nO2n+3 and Tl 2 Ba 2 Ca n−1 Cu n O 2n+4 are studied within the framework of the Ginzburg-Landau approach. Expressions for the transition temperatures in terms of phenomenological parameters are obtained. To achieve a consistent interpretation of the increases in the Tc’s of the members of the two series, it must be assumed that the TIO layers behave in different ways in the two series.
THE POLARON EFFECTS AND RELAXATION OF NON-EQUILIBRIUM ELECTRONS IN THE QUASI-TWO-DIMENSIONAL SYSTEMS
Authors: GUSEINOV N.M. , RUSTAMOV K.A. , SEYID-RZAYEVA S.M.
Published: November 2004

The problem on weak-coupling polaron in the quasi-two-dimensional electron system is solved. Analytical expressions for polaron energy shift of the subband and polaron contribution to the effective electron mass with arbitrary quantum well width are found. The expressions obtained give the well-known values for two- and three-dimensional limiting cases. A comparison of the polaron contribution to the mass with the available experimental data is carried out. Energy relaxation processes of non-equilibrium quasi-two-dimensional electrons with the optic phonon emission are also considered. General analytical expressions for the frequencies of intra-subband and inter-subband transitions for the threshold electron energy are obtained.
IONIZATION OF RYDBERG ATOMS BY CIRCULARLY POLARIZED MICROWAVE FIELDS
Authors: GALLAGHER T.F.
Published: November 2004

In circularly polarized microwave fields of frequencies in the vicinity of 10 GHz ionization of Na Rydberg atoms occurs at a field E=1/16n4, up to principal quantum number n=50. This field is equal to the classical field for ionization and the static field required to ionize a Na atom. On the other hand, this field is far below the linearly polarized 10 GHz field required to ionize Na atoms, E=1/3n5. If the problem is transformed to a frame rotating with the microwave field, the field becomes a static field. In this case it is straightforward to calculate the ionization field classically. However, it is far lower than the experimentally observed field, a discrepancy which may be due to an angular momentum barrier.
SURFACE PHONONS OF THE (100) SURFACE OF SOME COMPOUNDS WITH A ROCK-SALT CRYSTAL STRUCTURE
Authors: OSHIMA CHUHEI
Published: November 2004

The energy dispersion curves of surface phonons of the (100) surface of some compounds with a rock-salt crystal structure (TiC, ZrC, HfC, NbC, TaC, MgO, and NiO) have been investigated using electron energy loss spectroscopy. Drastic changes in force constants on all the carbide surfaces are correlated with a rippled structure. On the other hand, the surface phonons of insulating compounds, NiO and MgO (100), have showed dispersion curves agreeing with the predicted ones calculated on the basis of a shell model with bulk dynamical parameters. No changes in the parameters near the NiO and MgO (100) surfaces have been detected. The shielding effect of free electrons on the surface phonon for the transition metal carbide surfaces is discussed.
BOSE CONDENSATION IN THE U=∞ HUBBARD MODEL
Authors: NARIKIYO OSAMU
Published: November 2004

We support the concept of FERMI→BOSE transmutation in the U=∞ Hubbard model of Doucot and Wen1 by use of the anyon formulation with spin degree of freedom of Lee and Kane.3
THE EPR STUDIES OF HIGH-Tc SUPERCONDUCTORS (Bi, Pb)-Ca-Sr-Cu-O
Authors: GUSKOS N. , PATAPIS S.K. , POLITIS C.
Published: November 2004

The high-T c superconductors Bi 1.55 Pb 0.25 Sr 2 Ca 2.2 Cu 3 O 10, Bi 1.75 Pb 0.25 Sr 2 Ca 2 Cu 3 O 10 and Bi 1.75 Pb 0.25 Sr 2 Ca 3 Cu 4 O 12 (with about T c =106, 103 and 101 K, respectively) have been investigated using EPR method. Differences in intensities of the EPR spectra of Cu 2+ ions have been observed. These differences could be caused by the skin effect.
INTERFERENCE OF INELASTIC NEUTRON SCATTERING IN ANHARMONIC MODEL OF La2CuO4
Authors: PLAKIDA N.M. , STAMENKOVIĆ S.
Published: November 2004

Inelastic neutron scattering on acoustic and soft tilting modes in La 2 CuO 4 crystal is considered in the framework of a microscopic model. Interference effects due to anharmonic interaction between acoustic and soft modes are studied with a discussion on some unsual behaviours of inelastic neutron scattering in recent experiments.
THE EFFECT OF NEUTRON IRRADIATION ON FLUX PINNING IN MELT-TEXTURED GROWTH YBa2Cu3O7 SUPERCONDUCTOR
Authors: CHEN T. , ZHANG H. , SUN Y.X. , LIANG S.C. , REN H.T. , XIAO L. , HE Q. , YAN S.S.
Published: November 2004

The distribution of flux pinning energy in melt-textured growth (MTG) YBa 2 Cu 3 O 7 superconductor irradiated by fast neutrons was determined by rotating-sample magnetic measurement at liquid nitrogen temperature. It was found that neutron irradiation strengthened flux pinning by increasing the most probable pinning energy along c-axis and in ab plane by 47% and 82% respectively. Anisotropy of flux pinning was also observed. New strong pinning sites might be created by neutron irradiation.
MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS II: Electron Spin Resonance of DPPH Coated on Y1Ba2Cu3Oy as A Probe of Magnetic Field Variations
Authors: SUGAWARA K. , BAAR D.J. , SHIOHARA Y. , TANAKA S.
Published: November 2004

The ESR linewidth (∆H pp ) of DPPH coated on the surface of powder specimens of Y 1 Ba 2 Cu 3 O y has been studied under various magnetic field and temperature conditions. ∆H pp increases substantially with decreasing temperature in the field cooled case, whereas almost no linewidth broadening was found in the zero field cooled case. ∆H pp was found to be sensitive to the applied magnetic field. This effect was very pronounced at temperatures lower than 40 K, but decreased strongly with increasing temperature. The broadening of the resonance lineshape has been attributed to spatial and temporal variations of the fluxon distribution in the powder particles.
INSULATING 211 PHASE-SUPERCONDUCTING 123 PHASE TRANSFORMATION IN THE YBaCuO SYSTEM
Authors: HUANG C. Y. , LOO B. H. , WU M. K.
Published: November 2004

We have studied the conversion of insulating Y 2 BaCuO 5 to superconducting YBa 2 Cu 3 O x by means of Raman scattering, magnetization and electrical resistance measurements, scanning electron microscope and X-ray diffraction methods. The magnetic data show that as high as 12% of the conversion can be achieved.
ERGODIC MOTION AND NEAR COLLISIONS IN A COULOMB SYSTEM
Authors: VILELA MENDES R.
Published: November 2004

A many-particle system with positive and negative charged species, interacting through Coulomb forces and undergoing classical ergodic motion, is considered. The rate of dose encounters of two like charged particles at low energies is shown to be controlled by three-body near collisions. The rate of near collisions, under ergodic motion, is found to be fairly large. Possible implications for the occurrence of fusion events, under non-equilibrium conditions, are discussed.
ORTHO-PARA HYDROGEN CONVERSION ON METAL SURFACES
Authors: ILISCA E.
Published: November 2004

EELS experiments of H 2 absorbed at low temperature on Noble Metals have indicated that the o-p H 2 conversion can be very fast on metals, even in absence of chemisorption, in contradiction with the usual belief that the catalyst must be magnetic to be efficient. We examine a large family of processes which convert the hydrogen molecules on the basis of the emission of metal electron-hole pairs. The most efficient mechanism found is the Coulomb-Contact one based on a virtual charge transfer, back and forth, from the metal to the molecule, having a rate in agreement with experiment.
RAMAN SPECTROSCOPIC STUDY OF THE DIFFERENT CRYSTALLOGRAPHIC FACES OF YBa2Cu3O6+δ SINGLE CRYSTALS IN THE TETRAGONAL AND ORTHORHOMBIC PHASES
Authors: RAO S. M. , LOO B. H. , BREWSTER R. E. , CHANG J. M.
Published: November 2004

Raman spectra recorded on different crystallographic faces of the YBa 2 Cu 3 O 6+δ crystals in both the tetragonal and orthorhombic phases are presented which show that the spectra differ for the (001) face in the two phases.
THE COULOMB GAS FOR EXCITED STATES IN THE FRACTIONAL QUANTUM HALL EFFECT
Authors: HILKE M. , RUIZ-ALTABA M.
Published: November 2004

We follow Fubini's suggestion to use vertex operators for describing electrons and holes in the two-dimensional set-up appropriate for the description of the fractional quantum Hall effect, i.e., on the gauge-fixed magnetic plane. Laughlin's wave function is thus reproduced as the correlator of primary conformal fields, represented as exponentials of a free scalar field. We generalize an Ansatz by Halperin and present a new wave function describing the ground-state and the excited states of a system of unpolarized electrons. We realize these wave functions as correlators of normal-ordered exponentials of two free fields. We also give an explicit representation for the creation operator of an excitation.
ROOM TEMPERATURE MAGNETIC ANOMALIES IN BENZENE TREATED Bi–Pb–Sr–Ca–Cu–O POWDER
Authors: HARUTUNYAN A. R. , GRIGORYAN L. S. , KUZANYAN A. S. , KUZNETSOV A. A. , TERENTIEV A. A. , BARAN M. , JASIOLEK G. , SZYMCZAK H. , BASZYNSKI J.
Published: November 2004

Two samples of benzene-treated Bi–Pb–Sr–Ca–Cu–O powder exhibited at 300 K magnetic field dependent diamagnetism and magnetization irreversibility. The treatment with benzene resulted also in the appearance of microwave absorption at low magnetic fields, while is sensitive to magnetic history of the sample. From X-ray diffraction data one can see that upon benzene treatment the reflections of 85 K and 110 K phases do not change practically, but a series of new reflections appeared, indicating a lattice modulation with 4.9 nm periodicity. A microprobe analysis revealed substantial inhomogeneity of chemical composition across the samples. The room temperature anomalies were weakened in one sample and vanished in the second upon thermal cycling.
SUPERCONDUCTIVITY MECHANISM IN YBa2Cu3O7−x SYSTEMS FROM DIFFERENT DYNAMICAL ORBITAL POLARIZATIONS
Authors: LÓPEZ-AGUILAR F. , COSTA-QUINTANA J.
Published: November 2004

The electronic structure of the normal state of YBa 2 Cu 3 O 7−x for x=0 is analyzed by means of a model which includes different dynamical potentials for each localization channel (p and d). A feature of the electronic structure of YBa 2 Cu 3 O 7−x which has large influence on the appearance of the superconductivity is the different number of holes in the atoms of the CuO2 sheets with respect to the same atoms of the CuO3 chain. For increasing x-values, vacancies of neutral O4 atoms are produced and approximately an electron per O4 vacancy is added to the conduction band. The free charge added to the conduction band will tend to occupy fundamental states arising from the pz-orbital of O1 and dx2-y2/d3z2-y2 of Cu1 since these symmetries are dominant of EF. The process of O4 vacancy production produces a reorganization of the Cu sheet holes and they suffer an interatomic screening which implies coupling for the determined bandwidths and densities of unoccupied states.
STUDY OF THE DEPENDENCE OF HIGH Tc ON VARIOUS SINTERING TEMPERATURES FOR Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORS
Authors: NAQVI S.M. M.R. , QIDWAI A.A. , ZIA-UL-HAQUE S.M. , AHMAD FIROZ , RIZVI S.D.H. , HUMAYUN MUMTAZ
Published: November 2004

Bi1.7-Pb0.3-Sr2-Ca2-Cu3-Ox superconducting samples were prepared at 855°C, 862 C, 870 C, and 882 C sintering temperatures respectively. All samples were sintered for 120 hours. The samples were then quenched in liquid nitrogen.

The electrical resistivity measurements showed that the samples sintered at 870° C had the best Tc. For these samples the Tc onset was around 120 K and the zero resistance was obtained at 108 K. X-ray diffraction studies showed that the samples were multiphased.
DECAY OF THE ELECTRONIC SPIN POLARIZATION OUTSIDE A SURFACE OF A FERROMAGNETIC METAL
Authors: HELMAN J.S. , BALTENSPERGER W.
Published: November 2004

It is shown that the spin polarization of the electron cloud in thermal equilibrium with a ferromagnetic surface decays within a few Angstroms from the surface. This explains the vanishing spin polarization found in thermoemission from Ni and Fe by Vaterlaus et al. [Phys. Rev. Letters 65, 3041 (1990)].
MAGNETIC ORIGIN OF THE PHASE SEPARATION IN La2CuO4+δ
Authors: ERMILOV A.N.
Published: November 2004

A model for the phenomenon of phase separation in La 2 CuO 4+δ is proposed. The model is studied by the Monte Carlo simulation. The phase separation is obtained and completely accounted for by magnetic effects. A hole induced by an excess-oxygen ion alternates ferromagnetic coupling between copper spins to ferromagnetic in a group of Cu-Cu bonds forming a defective nest. Clustering of the movable nests, which walk together with the excess oxygens, is energetically favorable, since it reduces frustration energy.
EXACT SOLUTIONS OF SCHRODINGER’S EQUATION FOR SPIN SYSTEMS IN A CLASS OF TIME-DEPENDENT MAGNETIC FIELDS
Authors: TAHMASEBI M.J. , SOBOUTI Y.
Published: November 2004

A spin system in a time variable magnetic field is considered. For certain fields there exists a frame in which the Hamiltonian becomes static. The criterion for such fields is derived. The unitary transformation that accomplishes this task is obtained and the underlying Schrodinger equation is solved exactly.
ICON PURITY — TOWARD A FORMAL THEORY OF ICONS
Authors: CHANG SHI-KUO , TORTORA G. , YU BING , GUERCIO A.
Published: November 2004

In this paper, we give purity-preserving conditions for iconic operators, and present a formal definition of degree of icon purity by extending an icon system to a fuzzy icon system, based upon the theory of fuzzy sets. We also show an icon system can be modeled by means of an attribute grammar.
MORPHOLOGY ON UMBRA MATRICES
Authors: DOUGHERTY EDWARD R. , GIARDINA CHARLES R.
Published: November 2004

The umbra transform serves as a connection between gray-scale morphology and the classical two-valued morphology of G. Matheron and H. Hadwiger. From a general set-theoretic perspective, the umbra transform of an image (or signal) results in an infinite set, even in the discrete case. By employing bound matrix image representation it is possible to represent the umbra by a finite data structure, the result being an approach that is both intuitive and computational. Moreover, the method is essentially dimensionally independent and thus applies to both morphological image and signal processing.
KNOWLEDGE REPRESENTATION SCHEME BASED ON PETRI NET THEORY
Authors: RIBARIĆ SLOBODAN
Published: November 2004

An original knowledge representation scheme named KRP based on Petri net theory is proposed. The formal description of the scheme, and the inference procedure similar to "intersection search" in semantic networks, are given.
SYSTOLIC PYRAMID AUTOMATA, CELLULAR AUTOMATA AND ARRAY LANGUAGES
Authors: KRITHIVASAN KAMALA , MAHAJAN MEENA
Published: November 2004

Systolic pyramid automata accepting square arrays are defined. Homogeneous and semi-homogeneous pyramid automata are shown to have equal power though regular pyramid automata are more powerful. Languages accepted by these automata are compared with languages generated by array grammars and languages accepted by one-way 2-D cellular automata. Hexagonal pyramid automata are also considered and are shown to accept some languages generated by hexagonal array grammars.
CROSS-CORRELATED MEMORIES IN COMPLETELY-CONNECTED NETWORKS
Authors: ABDULLAH W.A.T. WAN
Published: November 2004

The Hopfield model for associative recall in a massively connected binary network is reviewed. The problems involved in representation are pointed out. Learning of cross-correlations is introduced, and results of computer simulations are displayed. The relationship with least mean squares learning in feed-forward layered networks is pointed out, leading to the analogue of unlearning. Simulation results show the performance of such a system.
THE ROLE OF LEARNING IN LOGIC SYNTHESIS
Authors: KIPPS JAMES R. , GAJSKI DANIEL D.
Published: November 2004

The goal of logic synthesis is to obtain high-quality designs from specifications. Current approaches to logic synthesis often trade off design quality for technology independence. In this paper, we present a model of logic synthesis that uses technology-specific design rules and extends rule-based search to functional decomposition and technology mapping. While this model improves design quality by taking advantage of the target technology, it is not robust to technology changes. To improve robustness, we augment the model with two learning components: one for acquiring rules that make use of physical cells in a technology library, and another for acquiring rules that make use of appropriate design styles. These components are related to work in the learning of macro-operators and explanation-based learning.
REPRESENTING AND PROCESSING PRODUCTION SYSTEMS IN CONNECTIONIST ARCHITECTURES
Authors: SOHN ANDREW , GAUDIOT JEAN-LUC
Published: November 2004

Much effort has been expended on developing special architectures dedicated to the efficient execution of problems in artificial intelligence (AI), especially production systems. While artificial neural networks (ANNs) offer the promise of solving various problems in pattern recognition and classification, we demonstrate here that the ANN approach can be applied to the AI production system paradigm. Among various types of neural networks, the three-layers of ring-structured feedback network is considered in this paper to suit the problem domain under investigation. Characteristics of the production system paradigm are identified. Various aspects of the use of feedback neural networks in mapping production systems are discussed. Two types of representation techniques are studied: local and hierarchical representations. A hierarchical representation derives features from patterns in production systems and constructs a 3-dimensional space called feature space, where a pattern can be uniquely defined by a vector. To demonstrate the efficient use of the neural network approach, a mapping of the generic production system is detailed throughout the paper. The results of a deterministic simulation demonstrate that the three layers of ring-structured feedback neural network architecture can be an efficient processing mechanism for the AI production system paradigm.
DIFFERENTIAL A*: AN ADAPTIVE SEARCH METHOD ILLUSTRATED WITH ROBOT PATH PLANNING FOR MOVING OBSTACLES AND GOALS, AND AN UNCERTAIN ENVIRONMENT
Authors: TROVATO KAREN I.
Published: November 2004

The robot path planning problem involves planning optimal paths for a robot to follow while ensuring it will not hit any obstacles or itself. In a state or perfectly known world, this has been addressed using the configuration space representation and the A* search algorithm. However, when movement, changes, or unexpected obstacles occur in the environment, a new method, Differential A*, can adapt the solution to the current situation. It updates only the fraction of space that is critically affected. This technique can provide significant speed improvements, with the same desired results, compared to complete space regeneration.
EXPERT SYSTEM APPROACH TO ASSESSMENTS OF BLEEDING PREDISPOSITIONS IN TONSILLECTOMY/ADENOIDECTOMY PATIENTS
Authors: PIZZI NICOLINO J. , GERRARD JON M.
Published: November 2004

The purpose of this expert system is to assess a predisposition to bleeding in a patient undergoing a tonsillectomy and/or adenoidectomy, as may occur with patients who have certain blood conditions such as hemophilia, von Willebrand’s disease, and platelet function defects. This objective is achieved by establishing a correlation between the patients’ responses to a medical questionnaire and the relative quantities of blood lost during their operations.

Three major modules constitute the system: the automated questionnaire to be completed by the patient, the expert system proper, and the patient database. The questionnaire is divided into fourteen sections on topics such as the occurrence of bruises and positive familial history. The expert system takes the responses to the questionnaire and determines risk categories for patients undergoing the operations. The patient database contains the patients’ questionnaire responses, personal data and the risk assessments generated by the expert system.

Subsequent to the development of the expert system prototype, inductive learning techniques were examined to automatically classify patients as either normal or abnormal. Specifically, Quinlan’s ID3 induction algorithm was used whereby a training set of patient data generates a classification tree whose leaf nodes correspond to the classification outcomes.

This paper presents the architecture of the hematology expert system, identifies some problems encountered during the knowledge engineering process and presents some statistical data pertaining to the accuracy of its risk assessments. It also offers a comparative review of the expert system and inductive learning methodologies.
ADAPTIVE PLANNING FOR AIR COMBAT MANEUVERING
Authors: HAYSLIP IRIS COX , ROSENKING JEFFREY P. , EILBERT JAMES
Published: November 2004

This paper describes Grumman’s Rapid Expert Assessment to Counter Threats (REACT) project, designed to aid pilots in air combat decision making. We present a hierarchical design for a planning system which addresses some of the real-time aspects of planning for threat response. This paper concentrates on the lowest level of this hierarchy which is responsible for planning combat maneuvers at low altitude over hilly terrain when the enemy is not in sight. REACT’s Lost Line of Sight module attempts to maximize the amount and depth of knowledge which can be utilized in the time available before the system must commit to its next action. It utilizes a hybrid architecture for planning decisions which incorporates multiple knowledge representations and planners based on artificial intelligence, neural networks, and decision theory. This architecture allows planning at different degrees of competence to be performed by concurrently operating planners with differing amounts of knowledge. We describe research on the planning issues in REACT as well as the associated knowledge representation and knowledge acquisition issues. In addition, we describe how work on developing terrain reasoning capability in REACT has suggested guidelines for knowledge base design and data management, system and language specifications, and planner architectures pertinent to real-time coupled systems.
OPTICAL CHARACTER RECOGNITION — A SURVEY
Authors: IMPEDOVO S. , OTTAVIANO L. , OCCHINEGRO S.
Published: November 2004

In order to highlight the interesting problems and actual results on the state of the art in optical character recognition (OCR), this paper describes and compares preprocessing, feature extraction and postprocessing techniques for commercial reading machines.

Problems related to handwritten and printed character recognition are pointed out, and the functions and operations of the major components of an OCR system are described.

Historical background on the development of character recognition is briefly given and the working of an optical scanner is explained.

The specifications of several recognition systems that are commercially available are reported and compared.
TRANSFORMATION-RING-PROJECTION (TRP) ALGORITHM AND ITS VLSI IMPLEMENTATION
Authors: TANG YUAN Y. , CHENG H. D. , SUEN CHING Y.
Published: November 2004

The size-orientation-invariance characteristic plays an important role in pattern recognition. It has many applications in computer vision, optical character recognition (OCR), office automation, electronic publication, graphics, etc. In this paper, a new method called transformation-ring-projection (TRP) is proposed to achieve this characteristic. In TRP, shape transformation technique is employed to center the pattern image and normalize its size; the ring-projection scheme is used to handle the orientation problem. An experiment was conducted to verify the proposed method in character recognition. The TRP algorithm requires only simple and regular operations, and provides the feasibility or VLSI implementation to speed up computation for real-time processing. A study on VLSI architecture with extensive parallel processing and pipelining capabilities for the proposed TRP algorithm is also presented.
RECOGNITION AND VERIFICATION OF HARDWRITTEN AND HAND-PRINTER BRITISH POSTAL ADDRESSES
Authors: DOWNTON A. C. , TREGIDGO R. W. S. , KABIR E.
Published: November 2004

An algorithmic architecture for a high-performance optical character recognition (OCR) system for hand-printed and handwritten addresses is proposed. The architecture integrates syntactic and contextual post-processing with character recognition to optimise postcode recognition performance, and verifies the postcode against simple features extracted from the remainder of the address to ensure a low error rate.

An enhanced version of the characteristic loci character recognition algorithm was chosen for the system to make it tolerant of variations in writing style. Feature selection for the classifier is performed automatically using the B/W algorithm.

Syntactic and contextual information for hand-printed British postcodes have been integrated into the system by combining low-level postcode syntax information with a dictionary trie structure. A full implementation of the postcode dictionary trie is described. Features which define the town name effectively, and can easily be extracted from a handwritten or hand-printed town name are used for postcode verification.

A database totalling 3473 postcode/address image has used to evaluate the performance of the complete postcode recognition process. The basic character recognition rate for the full unconstrained alphanumeric character set is 63.1%, compared with an expected maximum attainable 75–80%. The addition of the syntactic and contextual knowledge stages produces an overall postcode recognition rate which is equivalent to an alphanumeric character recognition rate of 86–90%. Separate verification experiments on a subset of 820 address images show that, with the first-order features chosen, an overall correct address feature code extraction rate of around 35% is achieved.
A REAL-TIME IMAGE SEGMENTATION SYSTEM USING A CONNECTIONIST CLASSIFIER ARCHITECTURE
Authors: BLANZ W. E. , GISH SHERI L.
Published: November 2004

An image segmentation system which uses a connectionist classifier architecture as a central building block is described in this paper. The complete system, which consists of a feature extraction module and the connectionist classifier module, has been designed and implemented in digital VLSl; system architectural aspects as well as the procedure of adaptation of the system to different segmentation problems are discussed. The performance of the segmentation system on real world problems is demonstrated using scenes from industrial inspection, texture recognition, and combustion chamber research tasks.
PROPOSED MODIFICATIONS TO PARALLEL STATE SPACE SEARCH OF GAME TREES
Authors: SHINGHAL RAJIAN , SHVED SOFIA
Published: November 2004

Modifications have been proposed to state space search algorithms for pruning game trees in parallel.The performance of these modified algorithms is empirically shown to be better than the other known parallel pruning algorithms.
A LEARNING-BASED SOFTWARE ENGINEERING ENVIRONMENT FOR REUSING DESIGN KNOWLEDGE
Authors: BAILIN SIDNEY C. , GATTIS ROBERT H. , TRUSZKOWSKI WALT
Published: November 2004

As part of the NASA/Goddard Code 522.3 research program in software engineering, a Knowledge-Based Software Engineering Environment (KBSEE) is being developed. The KBSEE will support a comprehensive artifact-reuse capability and will incorporate knowledge-based concepts such as machine learning and design knowledge capture. The distinguishing features of this work are that it is a systematic approach to the reuse of knowledge, not just of products, and it implements learning as an explicitly supported function in a software engineering environment.

Each of these objectives is currently being pursued in a distinct prototype environment: design knowledge capture and knowledge reuse in KAPTUR (Knowledge Acquisition for Preservation of Tradeoffs and Underlying Rationales), and learning in LEARN (Learning Enhanced Automation of Reuse Engineering). Despite their prototype realization in different environments, the integration of these approaches into an overall KBSEE is a key goal of our work.
COMPACT INTERVAL TREES: A DATA STRUCTURE FOR CONVEX HULLS
Authors: GUIBAS LEONIDAS , HERSHBERGER JOHN , SNOEYINK JACK
Published: November 2004

In this paper, we investigate the problem of finding the common tangents of two convex polygons that intersect in two (unknown) points. First, we give a Θ( log 2n) bound for algorithms that store the polygons in independent arrays. Second, we show how to beat the lower bound if the vertices of the convex polygons are drawn from a fixed set of n points. We introduce a data structure called a compact interval tree that supports common tangent computations, as well as the standard binary-search-based queries, in O( log n) time apiece. Third, we apply compact interval trees to solve the subpath hull query problem: given a simple path, preprocess it so that we can find the convex hull of a query subpath quickly. With O(n log n) preprocessing, we can assemble a compact interval tree that represents the convex hull of a query subpath in O( log n) time. In order to represent arrangements of Lines implicitly, Edelsbrunner et al. used a less efficient structure, called bridge trees, to solve the subpath hull query problem. Our compact interval trees improve their results by a factor of O( log n). Thus, the present paper replaces the paper on bridge trees referred to by Edelsbrunner et al.
COVERING CONVEX RECTILINEAR POLYGONS IN LINEAR TIME
Authors: LIOU W. T. , TANG C. Y. , LEE R. C. T.
Published: November 2004

In this paper, we discuss the problem of covering a convex rectilinear polygon with the minimum number of rectangles. The rectangles can overlap with each other. We show that this problem can be solved in linear time, which improves the previous O(n2) result proposed by Franzblau and Kleitman3. However, Franzblau and Kleitman's algorithm works for a larger class of polygons (vertically convex).
A REPRESENTATION OF THE BELAVKIN EQUATION VIA PHASE SPACE FEYNMAN PATH INTEGRALS
Authors: ALBEVERIO S. , GUATTERI G. , MAZZUCCHI S.
Published: November 2004

The Belavkin equation, describing the continuous measurement of the momentum of a quantum particle, is studied. The existence and uniqueness of its solution is proved via analytic tools. A stochastic characteristics method is applied. A rigorous representation of the solution by means of an infinite dimensional oscillatory integral (Feynman path integral) defined on the phase space is also given.
THE SQUARE OF WHITE NOISE AS A JACOBI FIELD
Authors: LYTVYNOV EUGENE
Published: November 2004

We identify the representation of the square of white noise obtained by Accardi, Franz and Skeide in [Comm. Math. Phys.228 (2002) 123–150] with the Jacobi field of a Lévy process of Meixner's type.
Estimating the Decadal Predictability of a Coupled AOGCM
Authors: Pohlmann Holger , Botzet Michael , Latif Mojib , Roesch Andreas , Wild Martin , Tschuck Peter
Published: November 2004

On seasonal time scales, ENSO prediction has become feasible in an operational framework in recent years. On decadal to multidecadal time scales, the variability of the oceanic circulation is assumed to provide a potential for climate prediction. To investigate the decadal predictability of the coupled atmosphere–ocean general circulation model (AOGCM) European Centre-Hamburg model version 5/Max Planck Institute Ocean Model (ECHAM5/MPI-OM), a 500-yr-long control integration and “perfect model” predictability experiments are analyzed. The results show that the sea surface temperatures (SSTs) of the North Atlantic, Nordic Seas, and Southern Ocean exhibit predictability on multidecadal time scales. Over the ocean, the predictability of surface air temperature (SAT) is very similar to that of SST. Over land, there is little evidence of decadal predictability of SAT except for some small maritime-influenced regions of Europe. The AOGCM produces predictable signals in lower-tropospheric temperature and precipitation over the North Atlantic, but not in sea level pressure.