bluuebunny/crossref_metadata_2025 huggingface dataset:
A POSSIBLE PAIRING MECHANISM FOR HTSC: TWO-DIMENSIONAL CONFINEMENT AND COULOMB OVER-SCREENING
Authors: ARIOSA D. , BECK H.
Published: July 2002

Among all the common properties of HTCS cuprates, we build our model on two of them: their high anisotropy, and their extremely low density of charge carriers. The intra-layer pairing mechanism is provided by the two-dimensional over-screening of Coulomb repulsion.1,2 The c-axis zero point energy restricts this pairing to a low carrier density region. Below a critical density, the system behaves as a two-dimensional confined jellium where the energy gain due to charge pairing is larger than the c-axis localization energy. In the high density region, where the pairing energy cannot compensate the localization energy, the system delocalizes and crosses over to a three-dimensional regime. This competition between binding and confinement energies implies a monotonic decrease of mass anisotropy with doping. Pre-formed pairs which exist below a Mean Field (MF) temperature defined by the binding energy, account for pseudo-gap observations.3,4 The superconducting critical temperature T c is given by the Beresinskii–Kosterlitz–Thouless (BKT) transition of the two-dimensional layer, renormalized by quantum phase fluctuations (QPF).5 QPF account for the metal-insulator transition at very low doping.
PROTEIN NANODOMAIN PATTERNS IN LIPIDIC BICONTINUOUS CUBIC PHASES
Authors: ANGELOV BORISLAV
Published: July 2002

Ordered nanopatterns that match to the {6, 4} tiling of the diamond type infinite periodic minimal surface are generated. The construction of the unit cell, generally recognized as a Monkey Saddle, is done numerically using the exact Weierstrass–Enneper representation of minimal surfaces. The obtained patterns are a good model for the self-assembly nanodomain organizations of membrane proteins, compatible with 3- or 6-fold symmetries and formed upon reconstitution in bicontinuous cubic lipid phases.
Investigation of the Quasicrystalline State of the D-Al67.5Cu17.5Rh15 and I-Al70Cu12Ru18 alloys
Authors: Athanasiou N. S. , Spirlet J. C. , Zwirner S. , Baskoutas S.
Published: July 2002

In the present study we report on the formation, characterization and magnetic susceptibility of two conventionally solidified quasicrystalline alloys with the nominal composition Al 67.5 Cu 17.5 Rh 15 (decagonal phase) and Al 70 Cu 12 Ru 18 (icosahedral phase). The characterization of the quasicrystalline state was examined by X-ray diffractometry (XRD), differential thermal analysis (DTA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDXA). Magnetic susceptibility results in the temperature range from 5 to 300 K utilizing SQUID magnetometry under constant magnetic field H=1 kOe are presented.
SHAPE TRACKING AND PRODUCTION USING HIDDEN MARKOV MODELS
Authors: CAELLI TERRY , MCCABE ANDREW , BRISCOE GARRY
Published: July 2002

This paper is concerned with an application of Hidden Markov Models (HMMs) to the generation of shape boundaries from image features. In the proposed model, shape classes are defined by sequences of "shape states" each of which has a probability distribution of expected image feature types (feature "symbols").The tracking procedure uses a generalization of the well-known Viterbi method by replacing its search by a type of "beam-search" so allowing the procedure, at any time, to consider less likely features (symbols) as well the search for an instantiable optimal state sequences. We have evaluated the model's performance on a variety of image and shape types and have also developed a new performance measure defined by an expected Hamming distance between predicted and observed symbol sequences. Results point to the use of this type of model for the depiction of shape boundaries when it is necessary to have accurate boundary annotations as, for example, occurs in Cartography.
AN INTEGRATED APPROACH TO SHAPE AND COLOR-BASED IMAGE RETRIEVAL OF ROTATED OBJECTS USING HIDDEN MARKOV MODELS
Authors: MÜLLER STEFAN , EICKELER STEFAN , RIGOLL GERHARD
Published: July 2002

An integrated approach to shape and color-based image retrieval, where the cues color and shape are both utilized in a local rather than a global way, is presented in this paper. An experimental retrieval system has been developed, which enables the user to search a color image database intuitively by presenting simple sketches. In order to be able to perform an elastic matching, which is especially needed in sketch-based image retrieval, objects in the images are represented by Hidden Markov Models. The use of streams (sets of features that are assumed to be statistically independent) within the HMM framework allows the integration of shape and color derived features into a single model, thereby allowing to control the influence of the different streams via stream weights. The approach has been evaluated on a color image database containing 120 different isolated objects with arbitrary orientation and showed good retrieval results with several users. Furthermore, the use of HMMs allows efficient pruning and thus a fast retrieval even with large databases.
SHAPE CLASSIFICATION BY MOMENT AND AUTOREGRESSIVE INVARIANTS
Authors: PEJNOVIĆ PREDRAG , MARKOVIĆ MILAN , STANKOVIĆ SRDAN
Published: July 2002

An experimental analysis of shape classification methods based on moment and autoregressive (AR) invariants is presented. Various types of translation, scale and rotation invariants are used to construct feature vectors for classification. The performance is evaluated using five different objects picked up from real scenes with a TV camera. Silhouettes and contours are extracted from nonoccluded two-dimensional (2D) objects rotated, scaled and translated in 3D space. The feature extraction methods are implemented and systematically tested using several parametric and nonparametric classifiers. The results clearly show the advantage of the method based on the moment invariants.
SPECT IMAGE RECONSTRUCTION USING COMPOUND PRIOR MODELS
Authors: LÓPEZ ANTONIO , MOLINA RAFAEL , MATEOS JAVIER , KATSAGGELOS AGGELOS K.
Published: July 2002

We propose a new iterative method for Maximum a Posteriori (MAP) reconstruction of SPECT (Single Photon Emission Computed Tomography) images. The method uses Compound Gauss Markov Random Fields (CGMRF) as prior model and is stochastic for the line process and deterministic for the reconstruction. Synthetic and real images are used to compare the new method with existing ones.
AUTOMATIC POINT CORRESPONDENCE AND REGISTRATION BASED ON LINEAR STRUCTURES
Authors: MARTÍ ROBERT , ZWIGGELAAR REYER , RUBIN CAROLINE M. E.
Published: July 2002

A novel method to obtain point correspondence in pairs of images is presented. Our approach is based on automatically establishing correspondence between linear structures which appear in images using robust features such as orientation, width and curvature extracted from those structures. The extracted points can be used to register sets of images. The potential of the developed approach is demonstrated on mammographic images.
ALGORITHMS AND VISUALIZATION FOR SOLUTIONS OF NONLINEAR ELLIPTIC EQUATIONS, PART II: DIRICHLET, NEUMANN AND ROBIN BOUNDARY CONDITIONS AND PROBLEMS IN 3D
Authors: CHEN GOONG , NI WEI-MING , PERRONNET ALAIN , ZHOU JIANXIN
Published: July 2002

This paper is a continuation of our earlier work [Chen et al., 2000]. Here, we use finite elements to help discretize a three-dimensional dumbbell-shaped domain with a cavity. The domain is thus nonconvex, nonstar-shaped, nonsymmetric and multiconnected. The finite element method is coupled with the scaling iterative algorithm to compute solutions of the Lane–Emden type equation with a single superlinear power nonlinearity term. The main thrust of this paper is to present graphical results (in color) for visualization in 3D to understand certain nonlinear effects and the occurrence of multiplicity of solutions when the domain has irregular geometry.
HEXAGONAL STRUCTURE IN INTERMEDIATE ASPECT RATIO BÉNARD–MARANGONI CONVECTION
Authors: RAMÓN M. L. , MAZA D. M. , MANCINI H. L. , MANCHO A. M. , HERRERO H.
Published: July 2002

In the present work, an isolated hexagonal structure is studied for the intermediate aspect ratio Bénard–Marangoni convection. Experimental and numerical results are contrasted, providing an alternative interpretation of the hexagon: Numerical results show that the hexagonal pattern can be reproduced by the overlapping of only two proper modes, which are numerical solutions of a linear analysis for the cylindrical problem with realistic boundary conditions. Experimental and numerical streamlines are compared. In bulk, this 3D structure gives rise to 2D streamlines, forming warped figures.
CLASSIFICATION OF BIFURCATIONS AND ROUTES TO CHAOS IN A VARIANT OF MURALI–LAKSHMANAN–CHUA CIRCUIT
Authors: THAMILMARAN K. , LAKSHMANAN M.
Published: July 2002

We present a detailed investigation of the rich variety of bifurcations and chaos associated with a very simple nonlinear parallel nonautonomous LCR circuit with Chua's diode as its only nonlinear element as briefly reported recently [Thamilmaran et al., 2000]. It is proposed as a variant of the simplest nonlinear nonautonomous circuit introduced by Murali, Lakshmanan and Chua (MLC) [Murali et al., 1994]. In our study we have constructed two-parameter phase diagrams in the forcing amplitude-frequency plane, both numerically and experimentally. We point out that under the influence of a periodic excitation a rich variety of bifurcation phenomena, including the familiar period-doubling sequence, intermittent and quasiperiodic routes to chaos as well as period-adding sequences, occur. In addition, we have also observed that the periods of many windows satisfy the familiar Farey sequence. Further, reverse bifurcations, antimonotonicity, remerging chaotic band attractors, and so on, also occur in this system. Numerical simulation results using Poincaré section, Lyapunov exponents, bifurcation diagrams and phase trajectories are found to be in agreement with experimental observations. The chaotic dynamics of this circuit is observed experimentally and confirmed both by numerical and analytical studies as well PSPICE simulation results. The results are also compared with the dynamics of the original MLC circuit with reference to the two-parameter space to show the richness of the present circuit.
DIFFUSIONAL MODEL FOR NOISY ON–OFF INTERMITTENCY
Authors: ČENYS A. , ULBIKAS J. , ANAGNOSTOPOULOS A. N. , BLERIS G. L.
Published: July 2002

Statistical properties of the laminar lengths for the noisy on–off intermittency are studied analytically. The universal distribution of the laminar phases is obtained at the critical point. It can be approximated by the power law with the exponent -3/2 and the exponential law describing fast falloff.
A NEW CRITERION FOR SYNCHRONIZATION OF COUPLED CHAOTIC OSCILLATORS WITH APPLICATION TO CHUA'S CIRCUITS
Authors: WANG XIAO FAN , WANG ZHI QUAN , CHEN GUANRONG
Published: July 2002

A new criterion is given for choosing the coupling constant in a system of coupled chaotic oscillators to guarantee their synchronization. The criterion is derived from a new observer design methodology based on Lyapunov stability theory. As an example and application, we prove the conjecture that synchronization of two chaotic Chua circuits can be achieved with the second state as the coupling variable provided that the coupling constant is suitably chosen according to the new criterion.
THE BLOCK PRODUCT OF C-VARIETIES: COMPARING APPROACHES
Authors: REY JEAN-FRANÇOIS
Published: July 2002

In this paper we compare the block product of C-varieties which we have defined in a previous paper to the two other constructions which were proposed on the one hand by D. Thérien and on the other hand by P. Jones and S. Pustejovsky. We prove that these three notions are equivalent. However, our definition is built on an explicit block product of two categories and then gives rise to a useful definition of the block product of two C-varieties which is needed for the theory of decompositions of monoids by means of wreath or block products.
ARTIN PRESENTATIONS I: GAUGE THEORY, 3 + 1 TQFT'S AND THE BRAID GROUPS
Authors: WINKELNKEMPER H. E.
Published: July 2002

We inititate the systematic study of Artin Presentations, (discovered in 1975 by González-Acuña), which characterize the fundamental groups of closed, orientable 3-manifolds, and form a discrete equivalent of the theory of open book decompositions with planar pages of such manifolds.

We list and prove the basic properties, state some fundamental problems and describe some of the advantages of the theory: e.g., an Artin Presentation of π1 (M3) does not just determine the closed, orientable 3-manifold M3, but also a canonical, smooth simply-connected cobordism of it, allowing us to tap into 4-dimensional gauge theory (and 3 + 1 TQFT's) in a more direct, purely discrete, functorial manner than others. Thus, in section 4, instead of using PDE's, we show how a canonical action of the commutator subgroup [Pn, Pn] of the pure braid group Pn can be used to study the smooth structures on a closed, smooth-connected 4-manifold with b2 = n, in a systematic way. However, the main purpose of this first paper is to Artin Presentations to set up simple criteria, testable with, say, MAGMA on the computer (where then no knowledge of topology is required) for finding explicit counter-examples to the so-called Weak Poincaré Conjecture: "Every homotopy 3-sphere bounds a smooth, compact, contractible 4-manifold," as well as: "Every irreducible Z-homology 3-sphere Σ, with π1 (Σ) = I (120) is homeomorphic to Σ (2, 3, 5)" and other conjectures implied by Thurston's Geometrization Conjecture. One first philosophical goal is to convince the reader that the truth of these conjectures is at least as unlikely as that of the Andrews-Curtis Conjecture and that ultimately, Artin Presentation Theory is a non-trivial intersection of string/M theory number theory.
EXISTENCE AND SURVIVAL OF TWO COMPETING SPECIES IN A POLLUTED ENVIRONMENT: A MATHEMATICAL MODEL
Authors: SHUKLA J. B. , AGRAWAL A. K. , DUBEY B. , SINHA P.
Published: July 2002

In this paper, a nonlinear mathematical model to study the effect of a toxicant emitted into the environment from external sources on two competing biological species is proposed and analyzed. The cases of constant emission and instantaneous spill of a toxicant are considered in the model study. In the case of constant emission, it is shown that four usual outcomes of competition between two species may be altered under appropriate conditions which are mainly dependent on emission rate of toxicant into the environment, uptake concentrations of toxicant by the two species and their growth rate coefficients and carrying capacities. However, in the case of instantaneous spill, it is found that if the washout rate of toxicant is large, then the four outcomes of competition exist under usual conditions. It is also pointed out that the survival of the competitors, coexisting in absence of the toxicant, may be threatened if the constant emission of toxicant into their environment continues unabatedly.
THE SHAPE OF THE HAZARD FUNCTION IN CERVICAL CANCER SURVIVAL
Authors: ZORIN A. V. , TSODIKOV A. D. , ZHARINOV G. M. , YAKOVLEV A. Y.
Published: July 2002

The shape of the hazard function is of great interest in studies of the efficacy of cancer treatment and post-treatment cancer surveillance. We present estimates of the hazard rates obtained from data on survival of patients with cervical cancer and discuss associated methodological problems. Our study was carried out on survival data for 1826 women with cancer of the cervix uteri stratified by clinical stage and tumor growth pattern. We used nonparametric and various smoothing techniques for estimating the hazard function from the data; these were a nonparametric estimator based on the Nelson-Aalen method and its kernel counterparts, the kernel local likelihood estimator with a data-adaptive bandwidth, and a parametric estimator specifically designed for two-component hazards. For all categories of patients, the estimated hazard functions pass through a clear-cut maximum, tending to zero as the follow-up time becomes sufficiently long. In one stratum of patients we observed a bimodal shape of the hazard function. There are two alternative models that provide equally plausible explanations of this observation; one of them attributes the observed pattern of the hazard function to a certain heterogeneity of tumor cell population, while the competing model refers to a heterogeneity of the subsample of patients under study. Providing the probability of cure is high, as is the case in our setting, there is no way to discriminate between the two models on the basis of survival data.
AN ANALYTIC APPROACH TO SOUND SCATTERING FROM A PAIR OF SCATTERERS WITH APPLICATION TO RIGID SPHERES
Authors: YE ZHEN , ALVAREZ ALBERTO
Published: July 2002

As a first step towards investigating multiple scattering of acoustic waves by a few scatterers, this paper presents a detailed study of the case that sound is scattered by a pair of arbitrary targets. An intuitive scheme is developed for calculating the effective scattering function. An approximate formula is derived and presented in a simple form. To verify the approach, it is applied to the special case of two rigid spheres, as the exact solution exists for this special situation. It is shown that the approximate results compare favorably with that from the exact solution for a wide range of situations. Through the comparison, the validity range of the approximate approach is inferred. Some ambiguities in the previously published results are also pointed out.
Ge LATERAL SEGREGATION AS A DOMINANT ALLOYING MECHANISM DURING LOW KINETIC Si CAPPING OF STRAINED Si1-xGex HUT ISLANDS
Authors: DENTEL D. , BISCHOFF J. L. , KUBLER L. , GHICA C. , WERCKMANN J. , DEVILLE J. P. , ULHAQ-BOUILLET C.
Published: July 2002

Several cross-sectional transmission electron microscopy images have shed light on the intermixing and island-smoothing mechanisms which occur during Si capping of roughened Si 0.5 Ge 0.5 hut cluster morphologies, strained on Si(001). By modifying either Si cap layer growth rates or temperatures upon identically corrugated alloys, more or less Si and Ge surface migrations are allowed, accordingly affecting the capped final morphology. In these images a Ge marker technique is used to take snapshots of the interfacial region in the first growing stages. They clearly demonstrate that, at 500°C and using low Si growth rates (a few monolayers/min), the segregation does not mainly operate by vertical site exchange but by Ge depletion from the island crests. Ge is able to diffuse laterally onto Si over distances comparable to the island rippling period (a few hundreds of Å) during Si heteregeneous growth in the morphology troughs. The initial island structure, subjected to strain gradients, thus acts as a Ge reservoir for noninterrupted Si surface energy reduction by lateral Ge segregation. The latter operates as long as Si is strain driven to accommodate heterogeneously in the island troughs where it minimizes its elastic energy. This finally results in a vanishing undulated morphology and in a smoothed Si/SiGe interface, at the cost of an alloyed region enlarged by the lateral segregation. As a consequence, the thickness of the smeared region is dominantly determined in this case by the initial hut cluster roughness and not by the usual vertical segregation length.
THE ORIENTATION OF BENZENE ON BIMETALLIC SURFACES
Authors: KOSCHEL H. , HELD G. , STEINRÜCK H.-P.
Published: July 2002

Angle-resolved UV photoelectron spectroscopy (ARUPS) using linearly polarized synchrotron radiation is used to determine the orientation of benzene molecules on two modifications of the pseudomorphic Ni/Cu(111) layer, the Ni-terminated adlayer and the Cu-terminated Ni sublayer. It is found that the molecules adsorb with their C–H bonds 30° off the close-packed substrate rows (σv orientation) on the Ni adlayer whereas no preferential orientation was found for the Cu-terminated Ni sublayer.

For these and other close-packed mono- and bimetallic surfaces involving Cu, Ni and Ru, the correlation between adsorption geometry and reactivity of benzene is explored in connection with temperature-programmed desorption (TPD). Like for the Ni/Cu(111) sublayer, no preferential lateral orientation and a weak bond is found on most other Cu-terminated surfaces at 80 K. This goes along with the absence of any dissociation on these surfaces. Only on the stretched 1 ML Cu/Ru(0001) surface is the substrate–benzene bond strong enough to induce a clear preferential orientation (σd with C–H bonds parallel to the close-packed rows) but still too weak to induce dissociation. The same orientation was found for the saturated benzene layer on Ni(111) where the molecules also do not dissociate. Dissociation is, however, observed for the saturation coverage of benzene on the Ni/Cu(111) adlayer and for low benzene coverages on Ni(111). On these surfaces the azimuthal orientation of the benzene molecules is σv, i.e. rotated by 30° with respect to the close-packed rows.
DETERMINATION OF TiO2(110) SURFACE RELAXATION BY VARIABLE POLARIZATION PHOTOELECTRON DIFFRACTION
Authors: VERDINI A. , SAMBI M. , BRUNO F. , CVETKO D. , NEGRA M. DELLA , GOTTER R. , FLOREANO L. , MORGANTE A. , RIZZI G. A. , GRANOZZI G.
Published: July 2002

A new method to determine the surface relaxation by means 0 of photoelectron diffraction (PED) from an s-core level has been applied to the (1 × 1)- TiO 2(110) surface. Complete 2π solid angle PED patterns for both oxygen 1s and titanium 3s core level peak intensities have been measured at the ALOISA beamline (Elettra Synchrotron, Italy) in two different photon polarization/electron detection geometrical configurations: one with the photon polarization vector parallel to the surface normal (TM polarization) and the other with the photon polarization vector perpendicular to the surface normal (TE polarization). In the latter case the PED sensitivity to the vertical spacing is enhanced. Because forward scattering is suppressed on the node of the primary wave along the surface normal, the relative weight of the distance-sensitive higher order interference fringes is enhanced. The opposite occurs for the TM polarization, which enhances the PED sensitivity to lateral spacing at grazing emission angles. The experimental PED patterns are compared with the theoretical simulations calculated for the relaxed and unrelaxed TiO 2(110) surface. The results prove the feasibility of the method and the adequacy of the PED technique to the studies of relaxation phenomena at crystal surfaces.
IS THE REGENERATIVE ABILITY OF A SEVERED MOTOR NERVE IN A RAT MODEL MAINTAINED OVER TIME?
Authors: Morohashi Masato , Maki Yutaka , Yoshizu Takae , Tsubokawa Naoto
Published: July 2002

We observed the change in the regenerative ability of a severed motor nerve at different time lapses using the cross nerve suture method in a rat model. A left tibial rat nerve was severed 15 mm distal to the divergent point of the sciatic nerve, and its proximal stump was covered with a silicon cap to prevent reinnervation. Zero, 1, 3, and 6 months after the initial operation, the proximal stump of the tibial nerve was anastomosed with the freshly severed distal stump of the peroneal nerve by a silicone cuff technique. Three and 6 months after the second operation, the tetanic isometric contraction force, wet weight, and minor axis of transversely sectioned reinnervated anterior tibial muscle fiber were measured. The regenerative ability of the severed motor nerve was maintained fairly well even 6 months after severance.
SIMULATED SWAPTION DELTA–HEDGING IN THE LOGNORMAL FORWARD LIBOR MODEL
Authors: DUN TIM , BARTON GEOFF , SCHLÖGL ERIK
Published: July 2002

Alternative approaches to hedging swaptions are explored and tested by simulation. Hedging methods implied by the Black swaption formula are compared with a lognormal forward LIBOR model approach encompassing all the relevant forward rates. The simulation is undertaken within the LIBOR model framework for a range of swaptions and volatility structures. Despite incompatibilities with the model assumptions, the Black method performs equally well as the LIBOR method, yielding very similar distributions for the hedging profit and loss — even at high rehedging frequencies. This result demonstrates the robustness of the Black hedging technique and implies that — being simpler and generally better understood by financial practitioners — it would be the preferred method in practice.
FROM THE IMPLIED VOLATILITY SKEW TO A ROBUST CORRECTION TO BLACK-SCHOLES AMERICAN OPTION PRICES
Authors: FOUQUE JEAN-PIERRE , PAPANICOLAOU GEORGE , SIRCAR K. RONNIE
Published: July 2002

We describe a robust correction to Black-Scholes American derivatives prices that accounts for uncertain and changing market volatility. It exploits the tendency of volatility to cluster, or fast mean-reversion, and is simply calibrated from the observed implied volatility skew. The two-dimensional free-boundary problem for the derivative pricing function under a stochastic volatility model is reduced to a one-dimensional free-boundary problem (the Black-Scholes price) plus the solution of a fixed boundary-value problem. The formal asymptotic calculation that achieves this is presented here. We discuss numerical implementation and analyze the effect of the volatility skew.
CONFRONTING MODEL MISSPECIFICATION IN FINANCE: TRACTABLE COLLECTIONS OF SCENARIO PROBABILITY MEASURES FOR ROBUST FINANCIAL OPTIMIZATION PROBLEMS
Authors: FRIEDMAN CRAIG
Published: July 2002

Despite the widespread realization that financial models for contingent claim pricing, asset allocation and risk management depend critically on their underlying assumptions, the vast majority of financial models are based on single probability measures. In such models, asset prices are assumed to be random, but asset price probabilities are assumed to be known with certainty, an obviously false assumption.

We explore practical methods to specify collections of probability measures for an assortment of important financial problems; we provide practical methods to solve the robust financial optimization problems that arise and, in the process, discover "dangerous" measures.
Dynamic Modeling of Stock Market Interdependencies: An Empirical Investigation of Australia and the Asian NICs
Authors: Masih Abul M. M. , Masih Rumi
Published: July 2002

This article examines the patterns of dynamic linkages among national stock prices of Australia and four Asian NIC stock markets namely, Taiwan, South Korea, Singapore and Hong Kong. By employing recently developed time-series techniques results seem to consistently suggest the relatively leading role of the Hong Kong market in driving fluctuations in the Australian and other NIC stock markets. In other words, given the generality of the techniques employed, Hong Kong showed up consistently as the initial receptor of exogenous shocks to the (long-term) equilibrium relationship whereas the Australian and the other NIC markets, particularly the Singaporean and Taiwanese markets had to bear most of the brunt of the burden of short-run adjustment to re-establish the long term equilibrium. Furthermore, given the dominance of the Hong Kong market in the region, the study also brings to light the substantial contribution of the Australian market in explaining the fluctuations to the other three markets, particularly Singapore and Taiwan. Finally, in comparison to all other NIC markets, Taiwan and Singapore appear as the most endogenous, with the former providing significant evidence of its short-term vulnerability to shocks from the more established market such as Australia.
Neutral networks: a combinatorial perspective
Authors: Kopp Stephan , Reidys Christian M.
Published: July 2002

The existence of neutral networks in genotype-phenotype maps has provided significant insight in theoretical investigations of evolutionary change and combinatorial optimization. In this paper we will consider neutral networks of two particular genotype-phenotype maps from a combinatorial perspective. The first map occurs in the context of folding RNA molecules into their secondary structures and the second map occurs in the study of sequential dynamical systems, a new class of dynamical systems designed for the analysis of computer simulations. We will prove basic properties of neutral nets and present an error threshold phenomenon for evolving populations of simulation schedules.
FEEDBACK SELF-ORGANIZING MAP AND ITS APPLICATION TO SPATIO-TEMPORAL PATTERN CLASSIFICATION
Authors: HORIO KEIICHI , YAMAKAWA TAKESHI
Published: July 2002

In this paper, a feedback self-organizing map (FSOM), which is an extension of the self-organizing map (SOM) by employing feedback loops, is proposed. The SOM consists of an input layer and a competitive layer, and the input vectors applied to the input layer are mapped to the competitive layer keeping their spatial features. In order to embed the temporal information to the SOM, feedback loops from the competitive layer to the input layer are employed. The winner unit in the competitive layer is not assigned by only current input vector but also past winner units, thus the temporal information can be embedded. The effectiveness and validity of the proposed FSOM are verified by applying it to a spatio-temporal pattern classification.
CLOS
Authors: Gabriel Richard P. , White Jon L. , Bobrow Daniel G.
Published: July 2002

Lisp has a long history as a functional language,
*
where action is invoked by calling a procedure, and where procedural abstraction and encapsulation provide convenient modularity boundaries. A number of attempts have been made to graft object-oriented programming into this framework without losing the essential character of Lisp—to include the benefits of data abstraction, extensible type classification, incremental operator definition, and code reuse through an inheritance hierarchy.

The Common Lisp Object System (CLOS) [3], a result of the ANSI standardization process for Common Lisp, represents a marriage of these two traditions. This article explores the landscape in which the major object-oriented facilities exist, showing how the CLOS solution is effective within the two contexts.
Optimal weight assignment for signature generation
Authors: Leng Chun-Wu Roger , Lee Dik Lun
Published: July 2002

Previous work on superimposed coding has been characterized by two aspects. First, it is generally assumed that signatures are generated from
logical
text blocks of the same size; that is, each block contains the same number of unique terms after stopword and duplicate removal. We call this approach the fixed-size block (FSB) method, since each text block has the same size, as measured by the number of unique terms contained in it. Second, with only a few exceptions [6,7,8,9,17], most previous work has assumed that each term in the text contributes the same number of ones to the signature (i.e., the weight of the term signatures is fixed). The main objective of this paper is to derive an optimal weight assignment that assigns weights to document terms according to their occurrence and query frequencies in order to minimize the false-drop probability. The optimal scheme can account for both uniform and nonuniform occurence and query frequencies, and the signature generation method is still based on hashing rather than on table lookup. Furthermore, a new way of generating signatures, the fixed-weight block (FWB) method, is introduced. FWB controls the weight of
every
signature to a constant, whereas in FSB, only the
expected
signature weight is constant. We have shown that FWB has a lower false-drop probability than that of the FSB method, but its storage overhead is slightly higher. Other advantages of FWB are that the optimal weight assignment can be obtained analytically without making unrealistic assumptions and that the formula for computing the term signature weights is simple and efficient.
An analysis of selected computer interchange color spaces
Authors: Kasson James M. , Plouffe Wil
Published: July 2002

Important standards for device-independent color allow many different color encodings. This freedom obliges users of these standards to choose the color space in which to represent their data. A device-independent interchange color space must exhibit an exact mapping to a colorimetric color representation, ability to encode all visible colors, compact representation for given accuracy, and low computational cost for transforms to and from device-dependent spaces. The performance of CIE 1931 XYZ, CIELUV, CIELAB, YES, CCIR 601-2 YCbCr, and SMPTE-C RGB is measured against these requirements. With extensions, all of these spaces can meet the first two requirements. Quantizing error dominates the representational errors of the tested color spaces. Spaces that offer low quantization error also have low gain for image noise. All linear spaces are less compact than nonlinear alternatives. The choice of nonlinearity is not critical; a wide range of gammas yields acceptable results. The choice of primaries for RGB representations is not critical, except that high-chroma primaries should be avoided. Quantizing the components of the candidate spaces with varying precision yields only small improvements. Compatibility with common image data compression techniques leads to the requirement for low luminance contamination, a property that compromises several otherwise acceptable spaces. The conversion of a device-independent representation to popular device spaces by means of trilinear interpolation requires substantially fewer lookup table entries with CCIR 601-2 YCbCr and CIELAB.
Efficient dataflow analysis of logic programs
Authors: Debray Saumya K.
Published: July 2002

A framework for efficient dataflow analyses of logic programs is investigated. A number of problems arise in this context: aliasing effects can make analysis computationally expensive for sequential logic programming languages; synchronization issues can complicate the analysis of parallel logic programming languages; and finiteness restrictions to guarantee termination can limit the expressive power of such analyses. Our main result is to give a simple characterization of a family of flow analyses where these issues can be ignored without compromising soundness. This results in algorithms that are simple to verify and implement, and efficient in execution. Based on this approach, we describe an efficient algorithm for flow analysis of sequential logic programs, extend this approach to handle parallel executions, and finally describe how infinite chains in the analysis domain can be accommodated without compromising termination.
Multiple comparisons with the best for steady-state simulation
Authors: Yuan Mingjian , Nelson Barry L.
Published: July 2002

Multiple-comparison procedures are useful for comparing the performance of competing systems via simulation. In this paper we extend a particular multiple-comparison procedure, multiple comparisons with the best, to steady-state simulation by using an autoregressive-output-analysis method.
Conjunction as composition
Authors: Zave Pamela , Jackson Michael
Published: July 2002

Partial specifications written in many different specification languages can be composed if they are all given semantics in the same domain, or alternatively, all translated into a common style of predicate logic. The common semantic domain must be very general, the particular semantics assigned to each specification language must be conducive to composition, and there must be some means of communication that enables specifications to build on one another. The criteria for success are that a wide variety of specification languages should be accommodated, there should be no restrictions on where boundaries between languages can be placed, and intuitive expectations of the specifier should be met.
Simplifying the modeling of multiple activities, multiple queuing, and interruptions
Authors: Davies Ruth M. , O'Keefe Robert M. , Davies Huw T. O.
Published: July 2002

Most conventional discrete-event simulation software assumes a simple progression of entities through queues and activities. Such software cannot cope easily with modeling systems where entities can be present in more than one queue, can be involved in more than one activity (i.e., scheduled for more than one event), or can be interrupted while queuing or taking part in an activity in order to join another queue or take part in a different activity. Low-level data structures to address these problems have been implemented in Pascal by extending an existing suite of Pascal procedures, call Pascal_SIM. The problems and their solutions are discussed in the context of machine breakdown in a production system. Comparisons between the use of the new structures and the existing ones showed some gain in computational efficiency and considerable improvement in ease of modeling. The generality of the data structure is considered.
References to remote mobile objects in Thor
Authors: Day Mark , Liskov Barbara , Maheshwari Umesh , Myers Andrew C.
Published: July 2002

Thor is a distributed object-oriented database where objects are stored persistently at highly available servers called object repositories, or ORs. In a large Thor system, performance tuning and system reconfiguration dictate that objects must be able to migrate among ORs. The paper describes two schemes for object references that support object migration, one using location-independent names and the other, location-dependent names. The paper analyzes the performance of the two schemes and concludes that location-dependent names are the right choice for systems like Thor, where we want fast access to objects that have migrated.
Parity logging disk arrays
Authors: Stodolsky Daniel , Holland Mark , Courtright William V. , Gibson Garth A.
Published: July 2002

Parity-encoded redundant disk arrays provide highly reliable, cost-effective secondary storage with high performance for reads and large writes. Their performance on small writes, however, is much worse than mirrored disks—the traditional, highly reliable, but expensive organization for secondary storage. Unfortunately, small writes are a substantial portion of the I/O workload of many important, demanding applications such as on-line transaction processing. This paper presents
parity logging
, a novel solution to the small-write problem for redundant disk arrays. Parity logging applies journalling techniques to reduce substantially the cost of small writes. We provide detailed models of parity logging and competing schemes—mirroring, floating storage, and RAID level 5—and verify these models by simulation. Parity logging provides performance competitive with mirroring, but with capacity overhead close to the minimum offered by RAID level 5. Finally, parity logging can exploit data caching more effectively than all three alternative approaches.
Bisimulation can't be traced
Authors: Bloom Bard , Istrail Sorin , Meyer Albert R.
Published: July 2002

In the concurrent language CCS, two programs are considered the same if they are
bisimilar
. Several years and many researchers have demonstrated that the theory of bisimulation is mathematically appealing and useful in practice. However, bisimulation makes too many distinctions between programs. We consider the problem of adding operations to CCS to make bisimulation fully abstract. We define the class of GSOS operations, generalizing the style and technical advantages of CCS operations. We characterize GSOS congruence in as a bisimulation-like relation called
ready-simulation
. Bisimulation is strictly finer than ready simulation, and hence not a congruence for any GSOS language.
Adaptive block rearrangement
Authors: Akyürek Sedat , Salem Kenneth
Published: July 2002

An adaptive technique for reducing disk seek times is described. The technique copies frequently referenced blocks from their original locations to reserved space near the middle of the disk. Reference frequencies need not be known in advance. Instead, they are estimated by monitoring the stream of arriving requests. Trace-driven simulations show that seek times can be cut substantially by copying only a small number of blocks using this technique. The technique has been implemented by modifying a UNIX device driver. No modifications are required to the file system that uses the driver.
Static analysis techniques for predicting the behavior of active database rules
Authors: Aiken Alexander , Hellerstein Joseph M. , Widom Jennifer
Published: July 2002

This article gives methods for statically analyzing sets of active database rules to determine if the rules are (1) guaranteed to terminate, (2) guaranteed to produce a unique final database state, and (3) guaranteed to produce a unique stream of observable actions. If the analysis determines that one of these properties is not guaranteed, it isolates the rules responsible for the problem and determines criteria that, if satisfied, guarantee the property. The analysis methods are presented in the context of the
Starburst Rule System
.
Knowledge-based document retrieval in office environments
Authors: Celentano Augusto , Fugini Maria Grazia , Pozzi Silvano
Published: July 2002

In the office environment, the retrieval of documents is performed using the concepts contained in the documents, information about the procedural context where the documents are used, and information about the regulations and laws that discipline the life of documents within a given application domain. To fulfill the requirements of such a sophisticated retrieval, we propose a document retrieval model and system based on the representation of knowledge describing the semantic contents of documents, the way in which the documents are managed by procedures and by people in the office, and the application domain where the office operates. The article describes the knowledge representation issues needed for the document retrieval system and presents a document retrieval model that captures these issues. The effectiveness of the approach is illustrated by describing a system, named
Kabiria
, built on top of such model. The article describes the querying and browsing environments, and the architecture of the system.
Making a digital library
Authors: Entlich Richard , Garson Lorrin , Lesk Michael , Normore Lorraine , Weibel Stuart
Published: July 2002

The CORE project is an electronic library of primary journal articles in chemistry, containing about five years of twenty primary journals published by the American Chemical Society (about 425,000 pages). Unlike many digital library projects, CORE includes both a scanned image and a marked-up ASCII version (represented in Standard Generalized Markup Language, or SGML) for each page of the publisher's database. Each page was scanned and segmented, with graphical units isolated and linked to figure references in the articles. The original machine-readable typography was converted to SGML format and the results were used to build databases with indexes for full-text Boolean searching; a single search engine served data for each of three X-Window interfaces.
Algorithm 746: PCOMP—a Fortran code for automatic differentiation
Authors: Dobmann M. , Liepelt M. , Schittkowski K.
Published: July 2002

Automatic differentiation is an interesting and important tool for all numerical algorithms that require derivatives, e.g., in nonlinear programming, optimal control, parameter estimation, and differential equations. The basic idea is to avoid not only numerical approximations, which are expensive with respect to CPU time and contain round-off errors, but also
hand-coded
differentiation. This article introduces the forward and backward accumulation methods and describes the numerical implementation of a computer code with the name PCOMP. The main intention of the approach used is to provide a flexible and portable Fortran code for practical applications. The underlying language is described in terms of a formal grammar and is a subset of Fortran with a few extensions. Besides a parser that generates an intermediate code and that can be executed independently from the evaluation routines, there are other subroutines for the direct computation of function and gradient values, which can be called directly from a user program. On the other hand, it is possible to generate a Fortran code for function and gradient evaluation that can be compiled and linked separately.
The Zebra striped network file system
Authors: Hartman John H. , Ousterhout John K.
Published: July 2002

Zebra is a network file system that increases throughput by striping the file data across multiple servers. Rather than striping each file separately, Zebra forms all the new data from each client into a single stream, which it then stripes using an approach similar to a log-structured file system. This provides high performance for writes of small files as well as for reads and writes of large files. Zebra also writes parity information in each stripe in the style of RAID disk arrays; this increases storage costs slightly, but allows the system to continue operation while a single storage server is unavailable. A prototype implementation of Zebra, built in the Sprite operating system, provides 4–5 times the throughput of the standard Sprite file system or NFS for large files and a 15–300% improvement for writing small files.
Demonstrational and constraint-based techniques for pictorially specifying application objects and behaviors
Authors: Vander Zanden Brad , Myers Brad A.
Published: July 2002

The Lapidary interface design tool is a demonstrational system that allows the graphics and run-time behaviors that go
inside
an application window to be specified pictorially. In particular, Lapidary allows the designer to draw example pictures of application-specific graphical objects that the end user will manipulate (such as boxes, arrows, or elements of a list), the feedback that shows which objects are selected (such as small boxes on the sides and corners of an object), and the dynamic feedback objects (such as hairline boxes to show where an object is being dragged). The run-time behavior of all these objects can be specified ina straightforward way using constraints, demonstration, and dialog boxes that allow the designer to provide abstract descriptions of the interactive response to the input devices. Lapidary generalizes from these specific example pictures and behaviors to create prototype objects and behaviors from which instances can be made at run-time. A novel feature of Lapidary's implementation is its use of constraints that have been explicitly specified by the designer to help it generalize example objects and behaviors and to guide it in making inferences.