bluuebunny/crossref_metadata_2025 huggingface dataset:
SELECTIVE ATTENTION TO PERCEPTUAL GROUPS: THE PHASE TRACKING MECHANISM
Authors: LUMER ERIK D.
Published: November 2004

We introduce a new mechanism of selective attention among perceptual groups as part of a computational model of early vision. In this model, selection of objects is a two-stage process: perceptual grouping is first performed in connectionist networks which dynamically bind together the neural activities triggered in response to related features in the image; secondly, by locking its output on the quasi-periodic bursts of activity associated with a single perceptual group, a system called the phase-tracker produces a temporal filter which retains the selected group for further processing while rejecting the unattended ones. The properties of our model are investigated in a number of simulations and interpreted in the context of current theories of visual attention developed in psychology.
RETRIEVAL IN INTERACTING NEURAL NETWORKS
Authors: OCHI MÁRCIA M. , DE MENEZES O.L.T.
Published: November 2004

We study the associative memory properties for a particular structure of neural network. It is assumed a low connectivity between two highly connected network regions. As process of common learning correlates the subpatterns stored in each region. The retrieval of the global pattern is studied as a function of the overlap between the associated subpatterns.
NEURAL NETS FOR KINK FINDING
Authors: Stimpfl-Abele Georg
Published: November 2004

Neural network learning techniques for the recognition of decays of charged tracks are improved by adding the track momentum to the input. This allows the use of one single network for a wide range of energies. The efficiency of this method is compared with previous results and conventional methods and the behaviour of the nets is discussed in detail.
PRINCIPLES OF MONOLITHIC WIDEBAND FEEDBACK AMPLIFIER DESIGN
Authors: HULL CHRISTOPHER D. , MEYER ROBERT G.
Published: November 2004

Fundamental principles for wideband amplifier analysis and design are presented. Analytically simple small-signal models for bipolar and field-effect devices are discussed. A more complex model is presented to show the effects of device parasitics, and a method is developed for gain-bandwidth analysis using the models derived. This method is applied to a number of common wideband amplifier circuits. Compound transistors are introduced and their advantages and disadvantages over single transistors are discussed. Finally, a comparison is made of circuit configurations that use shunt feedback to obtain impedance matching.
IMPACT OF OPTICAL FIBER AMPLIFIERS ON HIGH-SPEED LIGHTWAVE SYSTEMS AND WDM OPTICAL NETWORKS
Authors: LIN CHINLON
Published: November 2004

Significant advances in the technologies of optical fiber amplifiers have led to important applications in both very-high-speed long-distance lightwave transmission systems and broadband optical distribution networks. Optical fiber amplifiers can amplify optical signals at very high speeds (10–100 Gb/s) as well as multiple optical signals (10–100 optical channels) over a relatively wide spectral range. The combination of these two unique capabilities of optical fiber amplifiers makes it possible to achieve simultaneous optical amplification of multiple-optical-channel wavelength-division-multiplexed (WDM) optical signals, each optical channel carrying very-high-speed time-division-multiplexed (TDM) electronic signals. This paper gives a system user’s perspective on the implications and the potential impact of optical fiber amplifiers on very-high-speed lightwave transmission systems and broadband WDM-based optical networks.
REAL PROJECTIVE MANIFOLDS DEVELOPING INTO AN AFFINE SPACE
Authors: CHAE YOUNKI , CHOI SUHYOUNG , PARK CHAN-YOUNG
Published: November 2004

Suppose that an n-dimensional closed real projective manifold M, n ≥ 2, develops into an affine space RPn − RPn − 1 for an (n − 1)-dimensional subspace RPn − 1 of the projective space RPn. Then either M is convex or affine or M admits a flat foliation [Formula: see text] with a transverse invariant Hilbert metric. Further, if the codimension of [Formula: see text] is n − 1, then M is convex. We prove this statement by a use of a variation of Carrière's discompacté, a measure of non-compactedness of an affine group acting on an affine space.
QCD ON THE iPSC/860
Authors:   The MIMD Lattice Collaboration (MILC), BERNARD CLAUDE , DEGRAND THOMAS A. , DETAR CARLETON , GOTTLIEB STEVEN , KRASNITZ A. , OGILVIE MICHAEL C. , SUGAR R.L. , TOUSSAINT D.
Published: November 2004

Performance of the Intel iPSC/860 parallel processor for Quantum Chromodynamics codes with dynamical fermions is described. After reviewing the hardware and software environments provided by the manufacturer, the data structures appropriate for the QCD code are described. Techniques for maximum performance are briefly discussed. We achieve a speed of 10–15 Mŕlops per node depending upon how many lattice sites are located on each node.
PARALLEL ACCELERATION ALGORITHM FOR SPIN MODELS
Authors: BHANOT G.V. , ADLER S.L.
Published: November 2004

We describe and implement a multi-scale acceleration algorithm for spin models on a massively parallel supercomputer, the Connection Machine CM-200. Unlike usual cluster algorithms, our algorithm is completely parallelizable. The time to update all variables in a system of volume Ld scales as Ld log 2L. We prove this by computing the time for one lattice sweep for the 2-d XY model for our algorithm on lattices of size up to 2048×2048.
METASTABILITY AND DYNAMICS
Authors: HEERMANN DIETER W.
Published: November 2004

We briefly review some of the results on metastable and unstable states as observed by Monte Carlo simulations of short- and long-range Ising models.
EQUAL WEIGHT VERSUS EQUAL HEIGHT —A CONTROVERSY IN FINITE-SIZE SCALING THEORY
Authors: KAPPLER STEFAN , BORGS CHRISTIAN
Published: November 2004

Describing asymmetric first-order phase transitions by an order parameter distribution, there is a controversy in the literature concerning the relative normalization of the two occurring peaks. There are two rules for normalizing the distribution, called the “equal weight”-rule and the “equal height”-rule, which lead to different predictions of the finite-size scaling. We tested these predictions for an asymmetric model with two co-existing phases by means of a Monte Carlo simulation. We find overwhelming numerical evidence in favour of the “equal weight”-rule, showing at the same time that the shift of the susceptibility maximum with respect to the infinite volume transition point ht is proportional to L−2d, and not to L−d. In addition we tested a new method to determine the transition point ht which was recently proposed by Borgs and Janke.
AN APPROACH TO DATA PARALLEL MOLECULAR DYNAMICS FOR LIQUIDS
Authors: HEDMAN FREDRIK , LAAKSONEN AATTO
Published: November 2004

An efficient approach to large scale data parallel short-range molecular dynamics for liquids is presented. The method is based on the coarse-grained cell method in which the simulation cell is decomposed into equally sized subcells, with the shortest side being larger than the cut-off radius. To avoid a large fraction of the nonproductive calculations we develop a geometric sorting procedure based on particle distances to subcell boundaries. Due to particle migration, the contents of the subcells need to be updated. This is done with a method based only on nearest-neighbor communications. Special "null-particles" are introduced, which act as buffers during periodic updates and allow for a globally uniform algorithm during the force calculations. The method should be easy to implement on most massively parallel computers of SIMD or MIMD type. We have implemented our code in CM Fortran on an 8K CM200. Communication cost is around 7% of the total cpu time. The overall speed for one million particles is approximately 5.9μs per MD time step and per particle and 5.5μs for five million particles.
DIGITAL OPTICAL COMPUTING: A NEW APPROACH OF SYSTOLIC ARRAYS BASED ON COHERENCE MODULATION OF LIGHT AND INTEGRATED OPTICS TECHNOLOGY
Authors: GOEDGEBUER Jean-Pierre , BUTTERLIN Nadia , PORTE Henri
Published: November 2004

In optical computing, matrix-vector products are usually computed using systolic processors formed by acousto-optic cells illuminated by laser beams. We report a new approach based on coherence modulation of light. In this method, matrix-vector products are implemented electro-optically by a cascade of modulators forming a computing array. Several inputs can be operated on in parallel, and a number of operations can be performed digitally at one time. The demonstrator that was built in the frame of the European Programme "ESPRIT II Basic Research Action" to test this concept, is reported together with new results obtained using integrated optics technology.
SPLINE TECHNIQUES FOR SOLVING RELATIVISTIC CONSERVATION EQUATIONS
Authors: DEAN D. J. , BOTTCHER C. , STRAYER M. R.
Published: November 2004

We discuss a new numerical method for solving the relativistic hydrodynamic equations based upon the basis-spline collocation approach. Analytical and numerical results are compared for several problems, including one-dimensional expansions and collisions for which analytical solutions exist. Our methods, which may be easily and massively parallelized, are shown to give numerical results which agree to within a few percent of the analytic solutions. We discuss the relevance of the υ = z/t scaling solutions for the one-dimensional problem when applied to relativistic heavy-ion collisions. Finally, we discuss applications to three-dimensional problems, and present results for a typical three-dimensional expansion.
NEW SIMD ALGORITHMS FOR CLUSTER LABELING ON PARALLEL COMPUTERS
Authors: APOSTOLAKIS JOHN , CODDINGTON PAUL , MARINARI ENZO
Published: November 2004

Cluster algorithms are non-local Monte Carlo update schemes which can greatly increase the efficiency of computer simulations of spin models of magnets. The major computational task in these algorithms is connected component labeling, to identify clusters of connected sites on a lattice. We have devised some new SIMD component labeling algorithms, and implemented them on the Connection Machine. We investigate their performance when applied to the cluster update of the two-dimensional Ising spin model. These algorithms could also be applied to other problems which use connected component labeling, such as percolation and image analysis.
A SIMPLE MODEL WITH STRONG ASYMMETRIC COUPLINGS
Authors: BERNARDES AMÉRICO T. , HERRMANN HANS J.
Published: November 2004

In this paper an Ising model on a random lattice with strongly asymmetric couplings inspired by neural networks is studied. We investigate the phase space structure and find evidence for an ultrametric, "multivalley" structure as observed in disordered magnetic systems. We have calculated the size of the basins of attraction.
VISUALIZATION OF GRAPHICAL METHODS OF SERIES ANALYSIS
Authors: ADLER JOAN , CHANG IKSOO , SHAPIRA SHYE
Published: November 2004

Exact power series expansions provide a powerful method for studying the critical behaviour of many systems. Efficient analysis methods are essential to fully exploit the series approach. A particularly challenging problem in the analysis of these expansions is the elucidation of the critical behaviour in cases where critical temperature (or threshold) as well as dominant and correction exponent is unknown. We describe a scheme (which we call Visualization of Graphical methods for Series analysis, or VGS) developed explicitly for this situation and discuss its high precision implementation in a workstation environment. Our approach involves visualization of multiple approximants in a three-dimensional space. Several examples from Ising models, percolation and exactly solved systems are given.
THE STATIC QUARK-ANTIQUARK-POTENTIAL: A 'CLASSICAL' EXPERIMENT ON THE CONNECTION MACHINE CM-2
Authors: SCHILLING K. , BALI G. S.
Published: November 2004

This meeting produces another evidence that present parallel computers are (a) real instruments of computational physics, (b) largely in the hands of still-pioneers, (c) efficiently promoted by basic research groups with large-scale computational needs. Progress in parallel computing is carried by two types of such groups, that either follow the build-it-yourself or the early-use strategies. In this contribution, we describe, as an example to the second approach, the Wuppertal university pilot project in applied parallel computing. We report in particular about one of our key applications in theoretical particle physics on the Connection Machine CM-2: a high statistics computer experiment to determine the static quark-antiquark potential from quenched quantum chromodynamics.
THE CUBE-CONNECTED CYCLES NETWORK IS A SUBGRAPH OF THE BUTTERFLY NETWORK
Authors: FELDMANN R. , UNGER W.
Published: November 2004

We prove the following results:

(a) The Cube-Connected Cycles network of dimension n is a subgraph of the Butterfly network of dimension n.

(b) The Shuffle-Exchange network of dimension n is a subgraph of the DeBruijn network of dimension n.
THE COMBINATION TECHNIQUE FOR THE SPARSE GRID SOLUTION OF PDE'S ON MULTIPROCESSOR MACHINES
Authors: GRIEBEL MICHAEL
Published: November 2004

We present a new method for the solution of partial differential equations. In contrast to the usual approach which needs in the 2-D case [Formula: see text] grid points, our combination technique works with only [Formula: see text] grid points, where hn denotes the employed grid size. The accuracy of the obtained solution deteriorates only slightly from [Formula: see text] to [Formula: see text] for a sufficiently smooth solution. Additionally, the new method is perfectly suited for parallelization. On a machine with [Formula: see text] processors we get in practice an overall parallel complexity of only [Formula: see text]. The method can be generalized to higher dimensions. Then, the gain is expected to be even more dramatic. For the two-dimensional case, we report the results of numerical experiments obtained on a Transputer system and on the CRAY Y-MP.
A RECONFIGURATION TECHNIQUE FOR FAULT TOLERANCE IN A HYPERCUBE
Authors: RAI SURESH , TRAHAN JERRY L.
Published: November 2004

The hypercube architecture is a popular topology for many parallel processing applications. For continued operation of the hypercube multiprocessors after the failure of one or more i-subcubes and/or links, fault tolerance by reconfiguration is an important problem. This paper considers the reconfiguration issue and presents an algebraic technique to analyze the problem extending the concepts in [9]. The technique uses algebraic operators to identify the maximum dimensional fault-free subcube, and thus helps in achieving graceful degradation of the system. We analyze the complexity of our algorithm and show that it is efficient as compared to previous algorithms [1, 8, 14].
A LOW OVERHEAD SCHEDULE FOR A 3D-GRID GRAPH
Authors: BAMPIS E. , KÖNIG J.-C. , TRYSTRAM D.
Published: November 2004

We propose a new scheduling algorithm for a three-dimensional grid precedence graph of size n, and we prove that the communication overhead is just in Θ( log log n). Finally, we show that a lower bound for the overhead of any schedule with a fixed number of processors (p ≥ 3) is Ω( log log n).
GAUGE TRANSFORMATIONS AND GAUGE-FIXING CONDITIONS IN CONSTRAINT SYSTEMS
Authors: SUGANO REIJI , KAGRAOKA YUSHO , KIMURA TOSHIEI
Published: November 2004

Gauge transformations and gauge-fixing conditions in the total Hamiltonian (H T ) and extended Hamiltonian (H E ) formalisms are investigated. For gauge-fixing conditions χα, only the condition det ({ϕα, χβ}) ≠ 0 is usually imposed, where ϕα are first class constraints. This condition is not sufficient and one should (i) employ H T and (ii) choose the gauge-fixing conditions χα to be stationary under H T .

Gauge degrees of freedom in the Lagrangian formalism are equal in number to the primary first class constraints [Formula: see text]. Hence the number of arbitrarily chosen primary gauge conditions [Formula: see text] is the same as that of [Formula: see text]. Secondary gauge-fixing conditions associated with secondary first class constraints should be determined by the stationarity conditions of [Formula: see text]. If a canonical Hamiltonian (weakly) vanishes, χα must be explicitly time-dependent, otherwise we have the trivial result. Further, it is pointed out that the H E formalism has discrepancies with the H T formalism in many aspects.

As illustrations of these properties, a few typical models are examined.
A REALIZATION OF W GRAVITIES IN THE CONFORMAL GAUGE THROUGH GENERALIZED GAUSS MAPS
Authors: PARTHASARATHY R. , VISWANATHAN K. S.
Published: November 2004

String dynamics in ℝn with extrinsic geometry is studied in order to understand their hidden symmetries. String world sheet, realized as a conformal immersion in ℝn, is mapped into the Grassmannian G2, n through the Gauss map. This enables us to study the role of the extrinsic curvature in determining the WSO (n) gravities in the conformal gauge. It is shown that, classically, in ℝ3 and ℝ4 the geometry of surfaces of constant mean curvature densities is equivalent to WSO (n) (n = 3, 4) gravities, the corresponding W algebras being Virasoro (Vir) and Vir ⊕ Vir, respectively.
DESCRIPTION OF THE PAIRING CORRELATION FOR A STRONG COUPLING REGIME WITHOUT BREAKING THE ROTATIONAL SYMMETRY
Authors: SANDULESCU N. , RADUTA A. A.
Published: November 2004

By projecting out the lowest angular momentum from an orthogonal set of intrinsic functions describing a particle-core interacting system, a single-particle basis is obtained.1 This basis is used for describing a system of nucleons which interact among themselves by pairing forces. The specific influence of both the shell structure and the gap parameter is explicitly given.
PERTURBATION THEORY IN THE WESS–ZUMINO–NOVIKOV–WITTEN MODEL
Authors: LEUTWYLER H. , SHIFMAN M.
Published: November 2004

The perturbation theory of the WZNW model in two dimensions is investigated. We obtain closed expressions for the generating functional of the chiral currents and of the energy–momentum tensor, valid to all orders in 1/k where k is the integer parameter of the model. It is demonstrated how the relations of the Kač–Moody and Virasoro algebras emerge within the perturbative approach.
THE CASALBUONI–BRINK–SCHWARZ SUPERPARTICLE WITH COVARIANT, REDUCIBLE CONSTRAINTS
Authors: DAYI ÖMER F.
Published: November 2004

The fermionic constraints of the massless Casalbuoni–Brink–Schwarz superparticle in d = 10 are separated covariantly as first- and second-class constraints which are infinitely reducible. Although the reducibility conditions of the second-class constraints include the first-class ones a consistent quantization is possible. The ghost structure of the system for quantizing it in terms of the BFV–BRST methods is given and unitarity is shown.
A LIQUID ARGON OR XENON DETECTOR TO OBSERVE A NEUTRINO MAGNETIC MOMENT OF μν~10−11μB
Authors: CLINE DAVID B. , HONG WOOPYO
Published: November 2004

We describe the current situation in the search for a finite magnetic moment. Solar neutrino experiments can be interpreted in terms of a neutrino magnetic moment of ~10−10−10−11μB. Other astrophysical constraints are very model-dependent. We then describe a technique to detect a magnetic moment using neutrinos from a reactor or low energy neutrino facility and a cryogenic electron drift detector with a mass in the range of 1–5 tons. Background estimates are also given for an experimental search. We estimate that a neutrino magnetic moment down to 4×10−11μB can be searched for with this technique. We consider both argon and xeuon to be suitable detector components.
CLASSICAL AND CHERN-SIMONS VORTICES ON CURVED SPACE
Authors: VALTANCOLI PAOLO
Published: November 2004

The classical dynamics of some vortex models coupled to gravity in the critical coupling is considered. We derive the set of Bogomol’nyi-type equations of motion for the Abelian Higgs model and for the Chern-Simons vortex model, coupled to gravity. In both cases we are able to reduce the dynamics to a single nonlinear equation which generalizes, on a curved space, the corresponding vortex equation on the plane. We finally compute in both cases the asymptotic behavior for a multivortex configuration from the N particle metric without and with spin, respectively.
THE EXTRA GAUGE SYMMETRY OF STRING DEFORMATIONS IN ELECTROMAGNETISM WITH CHARGES AND DIRAC MONOPOLES
Authors: KLEINERT H.
Published: November 2004

We point out that electromagnetism with Dirac magnetic monopoles harbors an extra local gauge invariance called monopole gauge invariance. The gauge transformations act on a gauge field of monopoles [Formula: see text] and are independent of the ordinary electromagnetic gauge invariance. The extra invariance expresses the physical irrelevance of the shape of the Dirac strings attached to the monopoles. The independent nature of the new gauge symmetry is illustrated by comparison with two other systems, superfluids and solids, which are not gauge-invariant from the outset but which nevertheless possess a precise analog of the monopole gauge invariance in their vortex and defect structure, respectively. The extra monopole gauge invariance is shown to be responsible for the Dirac charge quantization condition 2eg/ħc=integer, which can now be proved for any fixed particle orbits, i.e. without invoking fluctuating orbits which would correspond to the standard derivation using Schrödinger wave functions. The only place where quantum physics enters in our theory is by admitting the action to jump by 2πħ×integer without physical consequences when moving the string at fixed particle orbits.
QUANTUM ANHOLONOMY AND GEOMETRICAL PHASE INTERFERENCE
Authors: LIANG J.Q.
Published: November 2004

Dragged wave functions are suggested for description of quantum geometrical phase interference. It is shown that the nontrivial topology of configuration space and Wess-Zumino type interactions are responsible for the nontrivial quantum anholonomy. The Aharonov-Bohm and Aharonov-Casher effects are unified under our framework.
GAUGE FIXING, UNITARITY AND PHASE SPACE PATH INTEGRALS
Authors: LAVELLE MARTIN , MCMULLAN DAVID
Published: November 2004

We analyse the extent to which path integral techniques can be used to directly prove the unitarity of gauge theories. After reviewing the limitations of the most widely used approaches, we concentrate upon the method which is commonly regarded as solving the problem, i.e. that of Fradkin and Vilkovisky. We show through explicit counterexamples that their main theorem is incorrect. A proof is presented for a restricted version of their theorem. From this restricted theorem we are able to rederive Faddeev’s unitary phase space results for a wide class of canonical gauges (which includes the Coulomb gauge) and for the Feynman gauge. However, we show that there are serious problems with the extensions of this argument to the Landau gauge and hence the full Lorentz class. We conclude that there does not yet exist any satisfactory path integral discussion of the covariant gauges.
ON THE CLASSICAL WN(l) ALGEBRAS
Authors: DEPIREUX DIDIER A. , MATHIEU PIERRE
Published: November 2004

We analyze the WN(l) algebras according to their conjectured realization as the second Hamiltonian structure of the integrable hierarchy resulting from the interchange of x and t in the l th flow of the sl (N) KdV hierarchy. The W4(3) algebra is derived explicitly along these lines, thus providing further support for the conjecture. This algebra is found to be equivalent to that obtained by the method of Hamiltonian reduction. Furthermore, its twisted version reproduces the algebra associated to a certain nonprincipal embedding of sl(2) into sl(4), or equivalently, the u(2) quasi-superconformal algebra. General aspects of the WN(l) algebras are also presented. We point out in particular that the x↔t interchange approach of the WN(l) algebra appears straightforward only when N and l are coprime.
THE CONFORMAL GROUP, POINT PARTICLES AND TWISTORS
Authors: HOWE P.S. , WEST P.C.
Published: November 2004

The massless particle action is interpreted as mechanics with a vanishing Hamiltonian on a phase space which is a coset space of the form G/H, where G is the conformal group and H is a certain subgroup. In dimensions 3, 4 and 6, twistor variables emerge naturally. In these same dimensions, the formalism can be extended straightforwardly to superparticles. In this approach the κ symmetry of the superparticle is interpreted as a part of the H gauge invariance of the action.
INVARIANT STRUCTURES IN GAUGE THEORIES AND CONFINEMENT
Authors: PROKHOROV L.V. , SHABANOV S.V.
Published: November 2004

The problem of finding all gauge invariants is considered in connection with the problem of confinement. Polylocal gauge tensors are introduced and studied. It is shown (both in physical and pure geometrical approaches) that the path-ordered exponential is the only fundamental bilocal gauge tensor, which means that any irreducible polylocal gauge tensor is built of P-exponentials and local tensors (matter fields). The simplest invariant structures in electrodynamics, chromodynamics and a theory with the gauge group SU(2) are considered separately. As a consequence of gauge invariance any “elementary” charge is accompanied by an external static field located on the integration contour of a P- exponential, i.e. by a string. The Coulomb field is analyzed from this point of view; it is demonstrated that it can also be considered as made of exponential line integrals. In QCD strings can branch—it means that the interquark static field cannot be associated with a simple P-exponential. On the contrary, in pure gluodynamics strings do not branch. Different forms of confinements are briefly reviewed.
REPRESENTATIONS OF QUANTUM GROUPS AT ROOTS OF 1: REDUCTION TO THE EXCEPTIONAL CASE
Authors: DE CONCINI CORRADO , KAC VICTOR G.
Published: November 2004

This paper is a continuation of the papers [DC-K] and [DC-K-P] on representations of quautum groups at roots of 1. Here we show that an irreducible representation of a quantum group at an odd root of 1 can be uniquely induced from an exceptional representation of a smaller quantum group. This reduces the classification of representations, the calculation of their characters and dimensions, etc, to the exceptional case.
RESTRICTED QUANTUM AFFINE SYMMETRY OF PERTURBED MINIMAL CONFORMAL MODELS
Authors: FELDER G. , LECLAIR A.
Published: November 2004

We study the structure of superselection sectors of an arbitrary perturbation of a conformal field theory. We describe how a restriction of the q-deformed sl(2) affine Lie algebra symmetry of the sine-Gordon theory can be used to derive the S-matrices of the Φ(1,3) perturbations of the minimal unitary series. This analysis provides an identification of fields which create the massive kink spectrum. We investigate the ultraviolet limit of the restricted sine-Gordon model, and explain the relation between the restriction and the Fock space cohomology of minimal models. We also comment on the structure of degenerate vacuum states. Deformed Serre relations are proven for arbitrary affine Toda theories, and it is shown in certain cases how relations of the Serre type become fractional spin supersymmetry relations upon restriction.
ON SEIFERT CIRCLES AND FUNCTORS FOR TANGLES
Authors: LEE H. C.
Published: November 2004

The properties of the Seifert circles in an oriented tangle diagram are exploited to prove a theorem that asserts that every (n,n)-tangle diagram is isotopic to a partially closed braid, and a second one that facilitates the assignment of wrong-way edges, one on each Seifert circle, in a tangle diagram. These result are used to identify the structure of an abstract algebra on which a functor for the isotopy of general tangles may be constructed. Any finite dimensional irreducible representation of a quasitriangular Hopf algebra is a realization of this algebra.
FIELD IDENTIFICATION IN NONUNITARY DIAGONAL COSETS
Authors: MATHIEU PIERRE , SÉNÉCHAL DAVID , WALTON MARK
Published: November 2004

We study the nonunitary diagonal cosets constructed from admissible representations of Kač-Moody algebras at fractional level, with an emphasis on the question of field identification. Generic classes of field identifications are obtained from the analysis of the modular S matrix. These include the usual class related to outer automorphisms, as well as some intrinsically nonunitary field identifications. They allow for a simple choice of coset field representatives where all field components of the coset are associated with integrable weights.
COMPARISON OF NEURAL NETWORK AND K-NN CLASSIFICATION METHODS IN VOWEL AND PATELLAR SUBLUXATION IMAGE RECOGNITIONS
Authors: KIM EUNG-KYEU , WU JIAN-TONG , TAMURA SHINICHI , SATO YOSHINOBU , CLOSE ROBERT , TAKETANI HISASHI , KAWAI HIDEO , INOUE MASAHIRO , ONO KEIRO
Published: November 2004

We make a comparision of classification ability between BPN (BackPropagation Neural Network) and k-NN (k-Nearest Neighbor) classification methods. Voice data and patellar subluxation images are used. The result was that the average recognition rate of BPN was 9.2 percent higher than that of the k-NN classification method. Although k-NN classification is simple in theory, classification time was fairly long. Therefore, it seems that real time recognition is difficult. On the other hand, the BPN method has a long learning time but a very short recognition time. Especially if the number of dimensions of the samples is large, it can be said that BPN is better than k-NN in classification ability.
GRAPH-BASED THINNING FOR BINARY IMAGES
Authors: SUZUKI SATOSHI , UEDA NAONORI , SKLANSKY JACK
Published: November 2004

A thinning method for binary images is proposed which converts digital binary images into line patterns. The proposed method suppresses shape distortion as well as false feature points, thereby producing more natural line patterns than existing methods. In addition, this method guarantees that the produced line patterns are one pixel in width everywhere. In this method, an input binary image is transformed into a graph in which 1-pixels correspond to nodes and neighboring nodes are connected by edges. Next, nodes unnecessary for preserving the topology of the input image and the edges connecting them are deleted symmetrically. Then, edges that do not contribute to the preservation of the topology of the input image are deleted. The advantages of this graph-based thinning method are confirmed by applying it to ideal line patterns and geographical maps.
DESIGN OF 2-D DIGITAL FILTERS BASED ON THE OPTIMAL DECOMPOSITION OF MAGNITUDE SPECIFICATIONS
Authors: DENG T.-B. , KAWAMATA M. , HIGUCHI T.
Published: November 2004

The optimal decomposition (OD) technique for decomposing 2-D magnitude specifications into 1-D ones is proposed. Differing from the conventional matrix decomposition methods such as the singular value decomposition (SVD), the OD of a 2-D magnitude specification matrix results in 1-D magnitude specifications which are always non-negative while the root mean-squared (rms) error in decomposition is minimum. Therefore, the OD is more suitable for designing 2-D digital filters (2DDFs) through designing one-dimensional digital filters (1DDFs) than the conventional matrix decomposition methods.

Based on the OD, the problem of designing a recursive 2DDF can be reduced to one of designing a pair of 1DDFs, one 1-input/multi-output, and the other multi-input/ 1-output. Consequently, 2DDFs can easily be obtained by designing 1DDFs using the well-established 1-D design techniques. Three design examples are presented to illustrate that this OD-based 2DDF design technique is extremely efficient.
NEW FIRST-ORDER COMPLEX DIGITAL-FILTER SECTIONS AND THEIR APPLICATION FOR THE REALIZATION OF IIR FILTERS
Authors: PRASAD K. S. , ESWARAN C. , ANTONIOU A.
Published: November 2004

New first-order complex digital-filter sections are realized using the concept of the generalized-immittance converter. These sections are then employed for the realization of infinite impulse response digital filters with real coefficients. The filters obtained with the proposed sections have sensitivity and roundoff noise properties that are comparable to those of other structures of this class reported earlier.
IDENTIFICATION OF TRUE AND SPURIOUS LYAPUNOV EXPONENTS FROM TIME SERIES
Authors: PARLITZ ULRICH
Published: November 2004

A new method for the identification of true and spurious Lyapunov exponents computed from time series is presented. It is based on the observation that the true Lyapunov exponents change their signs upon time reversal whereas the spurious exponents do not. Furthermore by comparison of the spectra of the original data and the reversed time series suitable values for the free parameters of the algorithm used for computing the Lyapunov exponents (e.g., the number of nearest neighbors) are determined. As an example for this general approach an algorithm using local nonlinear approximations of the flow map in embedding space by radial basis functions is presented. For noisy data a regularization method is applied in order to get smooth approximating functions. Numerical examples based on data from the Hénon map, a four-dimensional analog of the Hénon map, a quasiperiodic time series, the Lorenz model, and Duffing’s equation are given.
CHAOTIC PULSATION IN HUMAN CAPILLARY VESSELS AND ITS DEPENDENCE ON MENTAL AND PHYSICAL CONDITIONS
Authors: TSUDA ICHIRO , TAHARA TAKASHI , IWANAGA HIROAKI
Published: November 2004

We found a chaotic pulsation in a finger’s capillary vessels in both normal subjects and psychiatric patients, as well as cardiac chaos. A proof of chaos was made by the reconstruction of the dynamics in phase space and the calculation of the Lyapunov exponents. From the aspect of chaotic information processing, we give a measure of the information storage capacity of the observed chaos. We also found a difference in the topology of capillary and cardiac chaos, and a difference in their dependence on the subject’s conditions.
ABRUPT DIMENSION CHANGES AT BASIN BOUNDARY METAMORPHOSES
Authors: PARK BAE-SIG , GREBOGI CELSO , LAI YING-CHENG
Published: November 2004

Basin boundaries in chaotic dynamical systems can be either smooth or fractal. As a system parameter changes, the structure of the basin boundary also changes. In particular, the dimension of the basin boundary changes continuously except when a basin boundary metamorphosis occurs, at which it can change abruptly. We present numerical experiments to demonstrate such sudden dimension changes. We have also used a one-dimensional analytic calculation and a two-dimensional qualitative model to explain such changes.
SOFTWARE COMPONENTS FOR OBJECT-ORIENTED DATABASE SYSTEMS
Authors: BATORY DON , VASAVADA DEVANG
Published: November 2004

Genesis is a software system generator for database management systems that relies exclusively on as-is large scale component reuse. We review the general model of software components on which Genesis is based and discuss component libraries for relational database systems that we have implemented. We then explain how we have evolved Genesis and its libraries to be able to synthesize object-oriented database systems. We study a subproblem of creating “self-tuning” software systems by examining the performance of selected components for object-oriented database systems.
“ANTI-REFLECTION” COATING FOR A NONLINEAR TRANSMISSION TO TOTAL REFLECTION SWITCH
Authors: ZHOU P. , KHOO I.C.
Published: November 2004

An anti-reflection dielectric coating is designed for a nonlinear interface between a linear and a nonlinear medium. Expressions for the required thickness and refractive indices are derived. It is shown that the appropriately coated system will allow low power light to be initially highly transmitted even for incident angles close to the critical angle for total reflection; the system will also perform the nonlinear transmission to total-reflection switching for high power light.
HIGH DYNAMIC RANGE PASSIVE OPTICAL LIMITERS
Authors: HAGAN D.J. , XIA T. , SAID A.A. , WEI T.H. , VAN STRYLAND E.W.
Published: November 2004

We present results of optical limiting experiments designed to study optical geometries for increasing the dynamic range over which limiters function without incurring optical damage. Specifically, we investigate a tandem geometry with two passive nonlinear elements, one placed in the focal plane of a lens and the second placed “upstream” of the focal position to protect the material at focus from damage. To provide a proof-of-principle demonstration of this geometry, simple limiters consisting of combinations of reverse saturable absorber dyes and a carbon black suspension in thin cells were tested. Our results show that a substantial increase in device performance can be achieved by use of a tandem limiter geometry. Simple modelling predicts that the dynamic range of a separate-element tandem limiter is given by the product of the dynamic ranges of the individual component limiting elements, in agreement with our experimental results.
COUPLING SUPERVISED AND UNSUPERVISED TECHNIQUES IN TRAINING FEED-FORWARD NETS
Authors: KOUTSOUGERAS CRIS , PAPADOURAKIS GEORGE
Published: November 2004

A popular approach to training feed-forward nets is to treat the problem of adaptation as a function approximation and to use curve fitting techniques. We discuss here the problems which the use of pure curve fitting techniques entail for the generalization capability and robustness of the net. These problems are in general inherently associated with the use of pure supervised learning techniques. We argue that a better approach to the training of feed-forward nets is to use adaptive techniques that combine properties of both supervised and unsupervised learning. A new formulation of the training problem is presented here. According to this formulation the net is viewed as two coupled sub-nets the first of which is trained by an unsupervised learning technique and the second by a supervised one. The same formulation gives rise to analytic expressions of the goals of the adaptation and leads to a new method for the adaptation of feed-forward nets.
MASSIVELY PARALLEL IDA* SEARCH
Authors: COOK DIANE J. , LYONS GARY
Published: November 2004

Heuristic search is a fundamental component of Artificial Intelligence applications. Because search routines are frequently also a computational bottleneck, numerous methods have been explored to increase the efficiency of search. Recently, researchers have begun investigating methods of using parallel MIMD and SIMD hardware to speed up the search process.

In this paper, we present a massively-parallel SIMD approach to search named MIDA* search. The components of MIDA* include a very fast distribution algorithm which biases the search to one side of the tree, and an incrementally-deepening depthfirst search of all the processors in parallel. We show the results of applying MIDA* to instances of the Fifteen Puzzle problem and to the robot arm motion planning problem. Results reveal an efficiency of 74% and a speedup of 8553 and 492 over serial and 16-processor MIMD algorithms, respectively, when finding a solution to the Fifteen Puzzle problem that is close to optimal.
SKEPTICAL ABDUCTION
Authors: MARQUIS P.
Published: November 2004

Abduction is the process of generating the best explanation as to why a fact is observed given what is already known. A real problem in this area is the selective generation of hypotheses that have some reasonable prospect of being valid. In this paper, we propose the notion of skeptical abduction as a model to face this problem. Intuitively, the hypotheses pointed out by skeptical abduction are all the explanations that are consistent with the given knowledge and that are minimal, i.e. not unnecessarily general.

Our contribution is twofold. First, we present a formal characterization of skeptical abduction in a logical framework. On this ground, we address the problem of mechanizing skeptical abduction. A new method to compute minimal and consistent hypotheses in propositional logic is put forward. The extent to which skeptical abduction can be mechanized in first—order logic is also investigated. In particular, two classes of first-order formulas in which skeptical abduction is effective are provided. As an illustration, we finally sketch how our notion of skeptical abduction applies as a theoretical tool to some artificial intelligence problems (e.g. diagnosis, machine learning).
AN ACTIVE DATABASE APPROACH TO CONSISTENCY MANAGEMENT IN DATA- AND KNOWLEDGE-BASED SYSTEMS
Authors: SELIGMAN LEONARD J. , KERSCHBERG LARRY
Published: November 2004

Many AI and other applications populate their knowledge-bases with information retrieved from large, shared databases. This paper describes a new approach to maintaining consistency between objects in dynamic, shared databases and copies of those objects which are cached in an application knowledge-base. The approach relies on an intelligent interface to active databases that we call a Mediator for Approximate Consistency (MAC). The MAC has several unique features: (1) it permits applications to specify their consistency requirements declaratively, using a simple extension of a frame-based representation language, (2) it automatically generates the interfaces and database objects necessary to enforce those consistency requirements, shielding the knowledge-base developer from the implementation details of consistency maintenance, and (3) it provides an explicit representation of consistency constraints in the database, which allows them to be queried and reasoned about. The paper describes the knowledge-base/database consistency problem and previous approaches to dealing with it. It then describes our architecture for maintaining approximate knowledge-base/database consistency, including techniques for specifying, representing, and enforcing consistency constraints.
A UNIFIED MODEL AND METHODOLOGY FOR TEMPORAL OBJECT DATABASES
Authors: PISSINOU NIKI , MAKKI KIA
Published: November 2004

This paper identifies, explores and provides an approach to handling temporal information in object databases. It specifically involves the design and development of the Temporal Three Dimensional Information Space model that integrates time with objects. The model is based on a small number of simple temporal object constructs and provides a user with the basic primitives for temporal object definition, manipulation and retrieval. This research presents a step towards defining the concepts and techniques for incorporating time in object databases, and provides concrete experimental framework for demonstration thereof. Target Application environments include management and geographic information systems, database visualization and robotics.
KNOTS AND EXOTIC SMOOTH STRUCTURES ON 4-MANIFOLDS
Authors: AKBULUT S.
Published: November 2004

In this paper we give a short survey of exotic smooth structures of 4-manifolds. Various methods of constructing exotic structures and their relation to “Shake-Sliceness” and the Zeeman conjecture is discussed.
ON THE G2 LINK INVARIANT
Authors: KALFAGIANNI EFSTRATIA
Published: November 2004

We construct a polynomial link invariant as Markov trace on certain one parameter algebras and we prove that it is equal to the invariant corresponding to the exeptional Lie algebra of type G2. We use braid representatives to calculate the invariant for several knots and links.
MINISUPERSPACES: OBSERVABLES AND QUANTIZATION
Authors: ASHTEKAR ABHAY , TATE RANJEET , UGGLA CLAES
Published: November 2004

A canonical transformation is performed on the phase space of a number of homogeneous cosmologies to simplify the form of the scalar (or Hamiltonian) constraint. Using the new canonical coordinates, it is then easy to obtain explicit expressions of Dirac observables, i.e. phase-space functions which commute weakly with the constraint. This, in turn, enables us to carry out a general quantization program to completion. We are also able to address the issue of time through “deparametrization” and discuss physical questions such as the fate of initial singularities in the quantum theory. We find that they persist in the quantum theory in spite of the fact that the evolution is implemented by a one-parameter family of unitary transformations. Finally, certain of these models admit conditional symmetries which are explicit already prior to the canonical transformation. These can be used to pass to the quantum theory following an independent avenue. The two quantum theories — based, respectively, on Dirac observables in the new canonical variables and conditional symmetries in the original ADM variables — are compared and shown to be equivalent.
CLASSICAL CHANGE OF SIGNATURE INDUCED BY ACCELERATION
Authors: CAPOZZIELLO S. , FEOLI A.
Published: November 2004

We discuss the classical change of signature in Rindler space modified according to a model with maximal acceleration. This fact acquires great interest in quantum cosmology, when one considers the wave function of the universe tunneling from the Euclidean regime to the Lorentzian one.
QUANTUM GRAVITY ON CP2
Authors: VASSILEVICH D.V.
Published: November 2004

We construct the harmonic expansion for vector and tensor fields on CP2. Transversal harmonics are separated. The Seeley coefficients for the Maxwell field and gravity are computed.
SPECTRAL SHIFT FROM AN EVOLVING DUST SPHERE
Authors: BHUI B. , CHATTERJEE S. , BANERJEE A.
Published: November 2004

Following O’brien-Synge’s junction conditions we find an exterior solution for a (n+2)-dimensional spherically symmetric distribution in comoving coordinates and match it with the zero-pressure dust interior. An expression for Schwarzschild-like mass is also obtained from the conditions of fit at the boundary. The relevant transformation relations which recast the comoving exterior into the static Schwarzschild-like form are also obtained. This generalizes to higher dimensions an earlier work of Raychaudhuri in 4D spacetime. Utilizing the transformation relations, an expression for frequency shift of radiation emitted from the surface of the sphere is also obtained.
PARAMETRIZED t-MATRIX FOR pp → n Δ++ PROCESS
Authors: JAIN B. K. , SANTRA A. B.
Published: November 2004

Considering that, in pp scattering, the pp → n Δ++ transition occurs mainly from the elastic channel, a t-matrix for this process was constructed by us earlier. This t-matrix describes the measured cross-sections on the p (p, n) Δ++ process very well from threshold to a few GeV. The transition potential in it is described by the one pion-exchange potential and the elastic scattering wave function through the "measured" elastic scattering amplitude. In this paper, we have parametrized this t-matrix so that it can be used for describing the (p, Δ++) reaction in nuclei. The parametrized t-matrix has been found to have a structure similar to one pion-exchange potential except that it has a softer form factor (Λ ≈ 650–800 MeV/c ) and it has a Migdal term (g′ ≈ 0.65) in the central term. The imaginary part of the t-matrix is weak. In the single scattering approximation this t-matrix describes the measured cross-sections on p(3 He , t) Δ++ and 6 Li (p, Δ++)6 He reactions very well. It is also found that with this t-matrix, the "projectile excitation" contribution to the reaction is small.
EXCITATION FUNCTION STUDIES FOR THE ALPHA INDUCED REACTIONS IN INDIUM
Authors: BHARDWAJ M. K. , RIZVI I. A. , CHAUBEY A. K.
Published: November 2004

Excitation functions of the reactions (α, n ), (α, 2n ), (α, 3n ), (α, 4n ), (α, pn ), (α, 2p ) for 115 In and (α, n ), (α, 2n ) for 113 In have been measured up to 50 MeV bombarding energy using stacked foil activation technique. A stack of the target foils was irradiated at the Variable Energy Cyclotron Centre, Calcutta. The α-particle flux was monitored by charge collection method using Faraday Cup kept just behind the targets. Cross sections were measured at ten α-particle energies. The experimental data were compared with the theoretical predictions using ALICE/LIVERMORE-82 Code based on the geometry dependent hybrid model of Blann. The best consequence was obtained for exciton number n0 = 4 with configuration (2n + 2p + 0h).