bluuebunny/crossref_metadata_2025 huggingface dataset:
A manmachine balanced rapid object model for automation of pavement crack sealing and maintenance
Authors: Kim Young-Suk , Haas Carl T
Published: July 2002

A number of studies during the last few years have discussed automated crack detection and mapping using digital image processing technologies in roadway maintenance and rehabilitation. Many recent studies have applied digital image processing to the recognition or sealing of cracks in pavement. There have been great discrepancies, however, among various segmentation methods that extract crack types and locations or classify the extent of cracking. Since all sensing systems also produce some spurious data and experience noise due to the varied topological and color conditions of the pavement surface, accurately mapping and representing the pavement cracks to be sealed using such segmentation methods would be even harder. This paper illustrates an innovative machine vision algorithm developed for accurate crack mapping and representation in the University of Texas (UT) automated road maintenance machine (ARMM). The paper mainly focuses on illustrating the detailed logic and descriptions of the algorithm. Efficiency evaluation results of the ARMM manmachine balanced crack mapping and representation process, including the line-snapping and path-planning functions, are also shown. Using the algorithms as an edge-describing tool can have broader applications in automation of infrastructure maintenance and inspection of civil works and in the domain of digital image processing.Key words: automation, image processing, line snapping, pavement, crack sealing, maintenance.
Gene for integrin-associated protein (IAP, CD47): Physical mapping, genomic structure, and expression studies in skeletal muscle
Authors: Schickel Jörg , Stahn Katharina , Zimmer Klaus-Peter , Sudbrak Ralf , Størm Tim M , Dürst Matthias , Kiehntopf Michael , Deufel Thomas
Published: July 2002

Integrin-associated protein (IAP) is a widely expressed membrane protein with multiple functions in immunological and neuronal processes. Having physically mapped the IAP gene into a BAC/PAC contig covering approximately 1 Mb on human chromosome 3q13.1-q13.2, we determined the genomic organization of the gene, established its expression in skeletal muscle, and identified a novel splice variant. Our expression studies demonstrate expression of integrin-associated protein in the t-tubular system and the euchromatin of skeletal muscle cells where its function thus far is not known.Key words: integrin-associated protein, novel splice form, expression and subcellular localization in skeletal muscle, genomic organization.
A simplified nonlinear settlement prediction model for foundations on sand
Authors: Lehane Barry , Fahey Martin
Published: July 2002

This paper presents a simple method for predicting the settlement of spread foundations on sand operating under typical working loads. The method accounts for the well known effects on soil stiffness of strain, stress level, and density dependence, but adopts the simplifying assumption that the stress distribution beneath a loaded foundation can be obtained from Boussinesq's equations for an elastic half space. Despite this simplification, the method is shown to predict foundation responses that closely match those computed using more sophisticated finite element (FE) analyses and those measured in laboratory footing tests, where the stiffness characteristics in triaxial compression were well defined. The method is also seen to predict general variations of foundation settlement with bearing pressure, foundation width, and degree of preloading that are entirely consistent with empirically observed trends. It is concluded that satisfactory settlement predictions for shallow foundations on cohesionless soil may be obtained using Boussinesq's equations if the soil's vertical stiffness characteristics, as inferred from triaxial compression data, can be specified with some degree of precision.Key words: stiffness, settlement, cohesionless soil.
Growth and nutrition of hybrid poplars over 3 years after fertilization at planting
Authors: Brown K R , Driessche R van den
Published: July 2002

A hybrid poplar plantation on eastern Vancouver Island was fertilized at planting with two readily soluble and four controlled-release fertilizers (CRF). The CRFs varied in their duration of release and in their ratio of N to other elements. Fertilizers were applied at rates supplying 0, 13.5, or 27 g N/tree (N0, N13.5, and N27 treatments). The plantation contained one Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh. (T × D) and one P. trichocarpa × Populus maximowiczii A. Henry (T × M) hybrid. The T × D hybrid was consistently larger than the T × M hybrid. After 1 year, stem volumes were 24 and 35% greater in the N13.5 and N27 treatments, respectively; after 3 years, volumes were 9 and 21% greater, respectively. Volumes of trees fertilized with readily soluble fertilizers did not differ from those fertilized with CRFs, but volumes may have differed between CRFs. Growth of poplar on this site appeared to be limited by multiple elemental deficiencies, particularly of N, P, and S.
Coupling whole-tree transpiration and canopy photosynthesis in coniferous and broad-leaved tree species
Authors: Catovsky S , Holbrook N M , Bazzaz F A
Published: July 2002

We used sap flow as a measure of whole-tree function to examine how coniferous and broad-leaved species in mixed temperate forests differ in canopy-level transpiration and photosynthetic rates. We used heat dissipation probes to measure whole-tree sap flow in three species throughout one full year and then combined these measurements with micrometeorological monitoring and leaf-level gas exchange to determine whole-tree carbon gain. Both broad-leaved species (red oak, Quercus rubra L.; red maple, Acer rubrum L.) had two- to four-fold greater annual fluxes of water and carbon on a ground area basis than did the conifer (eastern hemlock, Tsuga canadensis (L.) Carrière), with red oak trees additionally showing 6080% higher fluxes than red maple. Despite fixing one-third of its carbon when broad-leaved species were leafless, hemlock was not able to compensate for its low photosynthetic rates during the growing season. Productivity measures derived from annual growth rings and eddy covariance confirmed that whole-tree sap flow provided a valuable estimate of both the magnitude of current forest fluxes and differences in individual species' fluxes. Our results indicate that the predicted loss of hemlock from mixed temperate forests could potentially increase whole-forest water loss and carbon gain by two- to four-fold, provided sufficient nitrogen and water remain available to support such a change.
Spatial and temporal patterns of solar radiation based on topography and air temperature
Authors: Kang Sinkyu , Kim Sungwoo , Lee Dowon
Published: July 2002

Incident solar radiation is a driving force for many ecological and hydrological processes. For this study, we developed TopoRad, a new radiation model, to describe spatial and temporal patterns of daily radiation based on topography and daily temperature regimes. The model was applied to the Mount Jumbong Forest, located in the mid-eastern area of the Korean peninsula; and the model calculations were evaluated by varying the spatial scales of the digital elevation models (DEMs). In the TopoRad, a clearness index was used to calculate global radiation on a horizontal surface and to partition direct and diffuse radiation. Topographic corrections were separately calculated for each direct and diffuse radiation, using daily topographic modifiers calculated from a DEM. TopoRad predicted daily global radiation of five weather stations with a mean absolute error of 3.1 MJ·m2·day1 and a mean bias of 0.3 MJ·m2·day1. In the spatial application for Mount Jumbong Forest, distinctively different patterns between direct and diffuse radiations were found where direct radiation (5.2 MJ·m2·day1) had more influence than diffuse radiation (4.6 MJ·m2·day1) on annual mean daily radiation. When the scaling effect was inspected across different spatial resolutions, the predicted global radiation was nonlinearly related to spatial resolutions. As the spatial resolution became more coarse, the predicted radiation decreased for south-facing slopes and increased for north-facing slopes, indicating that the predictions from the models cannot be generalized for gradients. TopoRad is better suited to predict daily radiation in rugged landscapes where fine-scale prediction is required.
ERRATUM TO "HADAMARD STATES, ADIABATIC VACUA AND THE CONSTRUCTION OF PHYSICAL STATES FOR SCALAR QUANTUM FIELDS ON CURVED SPACETIME"
Authors: JUNKER WOLFGANG
Published: July 2002

In this erratum we want to correct or modify some of the original statements and proofs in "Hadamard States, Adiabatic Vacua and the Construction of Physical States for Scalar Quantum Fields on Curved Spacetime" in Rev. Math. Phys. 8 (1996) 1091–1159.
EEG SOURCE LOCALIZATION: A COMPARATIVE STUDY OF CLASSICAL AND NEURAL NETWORK METHODS
Authors: ABEYRATNE UDANTHA R. , ZHANG G. , SARATCHANDRAN P.
Published: July 2002

We address the problem of estimating biopotential sources within the brain, based on EEG signals observed on the scalp. This problem, known as the inverse problem of electrophysiology, has no closed-form solution, and requires iterative techniques such as the Levenberg – Marquardt (LM) algorithm. Considering the nonlinear nature of the inverse problem, and the low signal to noise ratio inherent in EEG signals, a backpropagation neural network (BPN) has been recently proposed as a solution. The technique has not been properly compared with classical techniques such as the LM method, or with more recent neural network techniques such as the Radial Basis Function (RBF) network. In this paper, we provide improved strategies based on BPN and consider RBF networks in solving the inverse problem. We compare the performances of BPN, RBF and a hybrid technique with that of the classical LM method.
TOPOLOGICAL STRING DEFECT FORMATION DURING THE CHIRAL PHASE TRANSITION
Authors: BALACHANDRAN A. P. , DIGAL S.
Published: July 2002

We extend and generalize the seminal work of Brandenberger, Huang and Zhang on the formation of strings during chiral phase transitions1 and discuss the formation of Abelian and non-Abelian topological strings during such transitions in the early universe and in the high energy heavy-ion collisions. Chiral symmetry as well as deconfinement are restored in the core of these defects. Formation of a dense network of string defects is likely to play an important role in the dynamics following the chiral phase transition. We speculate that such a network can give rise to non-azimuthal distribution of transverse energy in heavy-ion collisions.
RAMAN AND FTIR SPECTRA OF RE(BrO3)3·9H2O(RE = Eu, Tb) AND ELECTRONIC TRANSITIONS IN Eu(BrO3)3·9H2O
Authors: BUSHIRI M. J. , NAYAR V. U.
Published: July 2002

Raman, FTIR spectra of Eu ( BrO 3)3·9 H 2 O and Tb ( BrO 3)3·9 H 2 O are recorded and analyzed. The observed bands are assigned on the basis of [Formula: see text] and H 2 O vibrations. Electronic transitions observed in the Raman spectra of Eu ( BrO 3)3· 9 H 2 O are also investigated. In Tb ( BrO 3)3·9 H 2 O the symmetry of [Formula: see text] anion is lowered from C 3 v to C s due to distortion. The wavenumber value of the ν1 mode of [Formula: see text] anion is found to be decreased from that of free state and is due to hydrogen bonding in the crystal. The decrease in wavenumber values of stretching modes and the increase in wavenumber values of the bending modes of water molecules from free state values confirm that they form hydrogen bonds with oxygen atoms are bromate ions in agreement with the structural data. Further the spectral pattern of water molecules indicates the presence of hydrogen bonds of varying strengths. The electronic transitions observed in Eu ( BrO 3)3·9 H 2 O suggest that Eu 3+ ions are situated in the crystal at sites having symmetry higher than C 2 or C 1.
THE 8V CSOS MODEL AND THE sl2 LOOP ALGEBRA SYMMETRY OF THE SIX-VERTEX MODEL AT ROOTS OF UNITY
Authors: DEGUCHI TETSUO
Published: July 2002

We review an algebraic method for constructing degenerate eigenvectors of the transfer matrix of the eight-vertex Cyclic Solid-on-Solid lattice model (8V CSOS model), where the degeneracy increases exponentially with respect to the system size. We consider the elliptic quantum group Eτ,η(sl2) at the discrete coupling constants: 2N η = m1 + im2τ, where N, m1 and m2 are integers. Then we show that degenerate eigenvectors of the transfer matrix of the six-vertex model at roots of unity in the sector SZ ≡ 0 ( mod N) are derived from those of the 8V CSOS model, through the trigonometric limit. They are associated with the complete N strings. From the result we see that the dimension of a given degenerate eigenspace in the sector SZ ≡ 0 ( mod N) of the six-vertex model at Nth roots of unity is given by [Formula: see text], where [Formula: see text] is the maximal value of the total spin operator SZ in the degenerate eigenspace.
ENERGY LEVELS IN A SPHERICAL QUANTUM DOT WITH PARABOLIC CONFINEMENT UNDER APPLIED ELECTRIC FIELDS
Authors: NICULESCU ECATERINA C.
Published: July 2002

Using a variational procedure, we have studied the electric field effect on the electronic states in a spherical GaAs – Ga 1-x Al x As quantum dot with parabolic confinement in the case of both finite and infinite barrier heights. For single-particle states of electrons and heavy holes a relative weak Stark shift at weak fields and a transition to a stronger shift at higher fields is found. Compared with a spherical quantum dot with a rectangular confinement potential, the parabolic quantum dot presents a greater restriction to the carriers. As a result, the confinement energy is larger, while the electric field effects on the energy levels are weaker. We conclude that a spherical quantum dot with a parabolic confinement may be significant for practical application.
PROPERTIES OF AlN(100) THIN FILMS PREPARED BY REACTIVE LASER ABLATION
Authors: WANG HONG-HAI
Published: July 2002

Aluminium nitride (100) thin films, grown on Si(100) by reactive laser ablation at low substrate temperature, have been investigated by many methods. Results show the AlN(100) films are dense and stable, with excellent (100) growth orientation and low residual stress. The intensity of the (100) diffraction peak correlates with deposition temperature and the residual stress is proportional to nitrogen pressure, but inversely proportional to discharge voltage. AlN(100) thin films retain thermal stability up to 500°C on annealing in an oxygen atmosphere. The etch rates of AlN(100) films in 85% and 0.5M NaOH increase with increasing solution temperature, and the activation energies in NaOH and H3PO4 are 36.3 kJ/mol and 23.2 kJ/mol, respectively.
CIRCULAR CODED TARGET FOR AUTOMATION OF OPTICAL 3D-MEASUREMENT AND CAMERA CALIBRATION
Authors: AHN SUNG JOON , RAUH WOLFGANG , KIM SUNG IL
Published: July 2002

One of the primary, but tedious, tasks for the user and developer of an optical 3D-measurement system is to find the homologous image points in multiple images, a task that is frequently referred to as the correspondence problem. Along with the solution, error-free correspondence and accurate measurement of image points are of great importance, on which the qualitative results of succeeding camera calibration and 3D-measurements are immediately dependent. In fact, the automation of measurement processes is getting more important with progresses in production, and hence, is of increasing topical interest. In this paper, we present a circular coded target for automatic image point measurement and identification. The applied image processing method will be described in detail, and we will show some application examples of the circular coded target to optical 3D-measurement techniques.
A SUPERVISED MODIFICATION OF THE HAUSDORFF DISTANCE FOR VISUAL SHAPE CLASSIFICATION
Authors: PUJOL ALBERT , VILLANUEVA JUAN JOSE , ALBA JOSE LUIS
Published: July 2002

Hausdorff distance is a deformation tolerant measure between two sets of points. The main advantage of this measure is that it does not need an explicit correspondence between the points of the two sets. This paper presents the application to automatic face recognition of a novel supervised Hausdorff-based measure. This measure is designed to minimize the distance between sets of the same class (subject) and at the same time maximize the distance of sets between different classes.
HOMOCLINIC BIFURCATION IN AN OCEAN CIRCULATION BOX MODEL
Authors: TITZ SVEN , KUHLBRODT TILL , FEUDEL ULRIKE
Published: July 2002

The qualitative behavior of a conceptual ocean box model is investigated. It is a paradigmatic model of the thermohaline ocean circulation of the Atlantic. In a bifurcation study, the two occurring bifurcations, a saddle-node and a Hopf bifurcation, are computed analytically. Using normal form theory, it is shown that the latter bifurcation is always subcritical. The unstable periodic orbit emerging at the Hopf bifurcation vanishes in a homoclinic bifurcation. The results are interpreted with respect to the stability of the thermohaline circulation.
MIXING OF GRANULAR MATERIALS: A TEST-BED DYNAMICAL SYSTEM FOR PATTERN FORMATION
Authors: HILL K. M. , GILCHRIST J. F. , OTTINO J. M. , KHAKHAR D. V. , McCARTHY J. J.
Published: July 2002

Mixing of granular materials provides fascinating examples of pattern formation and self-organization. More mixing action — for example, increasing the forcing with more vigorous shaking or faster tumbling — does not guarantee a better-mixed final system. This is because granular mixtures of just barely different materials segregate according to density and size; in fact, the very same forcing used to mix may unmix. Self-organization results from two competing effects: chaotic advection or chaotic mixing, as in the case of fluids, and flow-induced segregation, a phenomenon without parallel in fluids. The rich array of behaviors is ideally suited for nonlinear-dynamics-based inspection. Moreover, the interplay with experiments is immediate. In fact, these systems may constitute the simplest example of coexistence between chaos and self-organization that can be studied in the laboratory. We present a concise summary of the necessary theoretical background and central physical ideas accompanied by illustrative experimental results to aid the reader in exploring this fascinating new area.
QUATERNION DYNAMICS AND FRACTALS IN ℝ4
Authors: GALEEVA R. , VERJOVSKY A.
Published: July 2002

In this paper we study the Fatou–Julia theory for some quaternionic rational functions in the quaternion skew-field ℍ. We obtain new dynamically-defined fractals in ℝ4 as the corresponding Julia sets. We also define the quaternionic Mandelbrot set.
NAIVE SINGULAR PERTURBATION THEORY
Authors: O'MALLEY ROBERT E.
Published: July 2002

The paper demonstrates, via extremely simple examples, the shocks, spikes, and initial layers that arise in solving certain singularly perturbed initial value problems for first-order ordinary differential equations. As examples from stability theory, they are basic to many asymptotic techniques. First, we note that limiting solutions of linear homogeneous equations [Formula: see text] on t≥0 are specified by the zeros of [Formula: see text], rather than by the turning points where a(t) becomes zero. Furthermore, solutions to the solvable equations [Formula: see text] for k=1, 2 or 3 can feature canards, where the trivial limit continues to apply after it becomes repulsive. Limiting solutions of the separable equation [Formula: see text] may likewise involve switchings between the zeros of c(x) located immediately above and below x(0), if they exist, at zeros of A(t). Finally, limiting solutions of many other problems follow by using asymptotic expansions for appropriate special functions. For example, solutions of [Formula: see text] can be given in terms of the Bessel functions Kj(t4/4ε) and Ij(t4/4ε) for j=3/8 and -5/8.
A POSTERIORI ERROR ESTIMATION FOR THE FINITE ELEMENT METHOD-OF-LINES SOLUTION OF PARABOLIC PROBLEMS
Authors: ADJERID SLIMANE , FLAHERTY JOSEPH E. , BABUŠKA IVO
Published: July 2002

Babuška and Yu constructed a posteriori estimates for finite element discretization errors of linear elliptic problems utilizing a dichotomy principal stating that the errors of odd-order approximations arise near element edges as mesh spacing decreases while those of even-order approximations arise in element interiors. We construct similar a posteriori estimates for the spatial errors of finite element method-of-lines solutions of linear parabolic partial differential equations on square-element meshes. Error estimates computed in this manner are proven to be asymptotically correct; thus, they converge in strain energy under mesh refinement at the same rate as the actual errors.
CONTINUOUS ANALOG OF THE GAUSS–NEWTON METHOD
Authors: AIRAPETYAN R. G. , RAMM A. G. , SMIRNOVA A. B.
Published: July 2002

A Continuous Analog of discrete Gauss–Newton Method (CAGNM) for numerical solution of nonlinear problems is suggested. In order to avoid the ill-posed inversion of the Fréchet derivative operator, some regularization function is introduced. For the CAGNM, a convergence theorem is proved. The proposed method is illustrated by a numerical example in which a nonlinear inverse problem of gravimetry is considered. Based on the results of the numerical experiments, practical recommendations for the choice of the regularization function are given.
VASSILIEV KNOT INVARIANTS COMING FROM LIE ALGEBRAS AND 4-INVARIANTS
Authors: SOBOLEVA E.
Published: July 2002

We study the 4-bialgebra of graphs and the bialgebra of 4-invariants introduced by S. K. Lando. Our main goal is the investigation of the relationship between 4-invariants of graphs and weight systems arising in the theory of finite order invariants of knots. In particular, we show that the corank of the adjacency matrix of a graph leads to the weight system coming from the defining representation of the Lie algebra gl(N).
EXACT RESULTS FOR THE BTZ BLACK HOLE
Authors: BIRMINGHAM DANNY , SACHS IVO , SEN SIDDHARTHA
Published: July 2002

In this review, we summarize exact results for the three-dimensional BTZ black hole. We use rigorous mathematical results to clarify the general structure and properties of this black hole spacetime and its microscopic description. In particular, we study the formation of the black hole by point particle collisions, leading to an exact analytic determination of the Choptuik scaling parameter. We also show that a "No Hair Theorem" follows immediately from a mathematical theorem of hyperbolic geometry, due to Sullivan. A microscopic understanding of the Bekenstein–Hawking entropy, and decay rate for massless scalars, is shown to follow from standard results of conformal field theory.
EXACT MODELS FOR ANISOTROPIC RELATIVISTIC STARS
Authors: MAK M. K. , DOBSON PETER N. , HARKO T.
Published: July 2002

We present a class of exact solutions of the Einstein gravitational field equations describing spherically symmetric and static anisotropic stellar type configurations. The solution is represented in a closed integral form. The energy density and both radial and tangential pressure are finite and positive inside the anisotropic star. The energy density, radial pressure, pressure-density ratio and the adiabatic speed of sound are monotonically decreasing functions. Several stellar models with the anisotropy coefficient proportional to r2 are discussed, the values of the basic physical parameters of the star (radius, mass and red shift) and bound on anisotropy parameter is obtained.
THE IMPACT OF TIDAL ERRORS ON THE DETERMINATION OF THE LENSE–THIRRING EFFECT FROM SATELLITE LASER RANGING
Authors: PAVLIS ERRICOS C. , IORIO LORENZO
Published: July 2002

The general relativistic Lense–Thirring effect can be detected by means of a suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS II satellites. While this observable is not affected by the orbital perturbation induced by the zonal Earth solid and ocean tides, it is sensitive to those generated by the tesseral and sectorial tides. The assessment of their influence on the measurement of the parameter μ LT , with which the gravitomagnetic effect is accounted for, is the goal of this paper. After simulating the combined residual curve by calculating accurately the mismodeling of the more effective tidal perturbations, it has been found that, while the solid tides affect the recovery of μ LT at a level always well below 1%, for the ocean tides and the other long-period signals Δμ depends strongly on the observational period and the noise level: Δμ tides ≃ 2% after seven years. The aliasing effect of K11=3 p=1 tide and SRP(4241) solar radiation pressure harmonic, with periods longer than four years, on the perigee of LAGEOS II yield to a maximum systematic uncertainty on μ LT of less than 4% over different observational periods. The zonal 18.6-year tide does not affect the combined residuals.
A NONRELATIVISTIC QUANTUM MECHANICAL TREATMENT OF A SYSTEM OF SELF-GRAVITATING PARTICLES
Authors: TRIPATHY D. N. , MISHRA SUBODHA
Published: July 2002

By making an intuitive choice for the single-particle density of a system of N self-gravitating particles, without any source for the radiation of energy, we have been able to calculate the binding energy of the system by treating these particles as fermions. Our expression for the ground state energy of the system shows a dependence of N7/3 on the particle number, which is in agreement with the results obtained by other workers. We also arrive at a compact expression for the radius of a star following which we correctly reproduce the nucleon number to be found in a typical star. Using this value, we obtain the well-known result for the limiting value of the mass, M, of a neutron star (M ≃ 3.12 M ⊙, M⊙ being the solar mass) beyond which the black hole formation should take place. Generalizing the present calculation to the case of white dwarfs, we have been able to obtain the so called Chandrasekhar limit for the mass, M Ch , (M Ch ≃ 1.44 M ⊙) below which the stars are expected to go over to the white dwarf state. We reproduce this by introducing a radius, equivalent to Schwarzschild radius, at the interface of the neutron stars and white dwarfs. This is justified by considering the fact that it gives rise to the correct value for the degree of ionization μe(μe ≈ 2) for heavy nuclei.
WAVE PROPAGATION IN 2-D ELASTIC MEDIA USING A SPECTRAL ELEMENT METHOD WITH TRIANGLES AND QUADRANGLES
Authors: KOMATITSCH DIMITRI , MARTIN ROLAND , TROMP JEROEN , TAYLOR MARK A. , WINGATE BETH A.
Published: July 2002

We apply a spectral element method based upon a conforming mesh of quadrangles and triangles to the problem of 2-D elastic wave propagation. The method retains the advantages of classical spectral element methods based upon quadrangles only. It makes use of the classical Gauss–Lobatto–Legendre formulation on the quadrangles, while discretization on the triangles is based upon interpolation at the Fekete points. We obtain a global diagonal mass matrix which allows us to keep the explicit structure of classical spectral element solvers. We demonstrate the accuracy and efficiency of the method by comparing results obtained for pure quadrangle meshes with those obtained using mixed quadrangle-triangle and triangle-only meshes.
TRANSFORMATION OF THE ELECTRONIC STRUCTURE OF Cu INTO Cu2O IN THE ADSORPTION OF OXYGEN
Authors: BELASH V. P. , KLIMOVA I. N. , KORMILETS V. I. , TRUBITSIN V. YU. , FINKELSTEIN L. D.
Published: July 2002

Systematic photoelectron-spectroscopy studies of the oxygen adsorption on a polycrystalline copper in a wide range of oxygen exposures allowed us to trace the step-by-step transformation of the electronic structure of pure Cu into the electronic structure of Cu 2 O . With the use of the density-of-states calculations implemented by the full-potential linear muffin-tin-orbital method, the interpretation of a number of features in the photoelectron spectra and their behavior with the increase of oxygen exposure was carried out. It was also shown that copper-surface oxidation proceeds in three main steps.
MULTIFRACTAL FLUCTUATIONS IN FINANCE
Authors: SCHMITT FRANCOIS , SCHERTZER DANIEL , LOVEJOY SHAUN
Published: July 2002

We consider the structure functions S(q)(τ), i.e. the moments of order q of the increments X(t + τ)-X(t) of the Foreign Exchange rate X(t) which give clear evidence of scaling (S(q)(τ)∝τζ(q)). We demonstrate that the nonlinearity of the observed scaling exponent ζ(q) is incompatible with monofractal additive stochastic models usually introduced in finance: Brownian motion, Lévy processes and their truncated versions. This nonlinearity correspond to multifractal intermittency yielded by multiplicative processes. The non-analyticity of ζ(q) corresponds to universal multifractals, which are furthermore able to produce "hyperbolic" pdf tails with an exponent qD > 2. We argue that it is necessary to introduce stochastic evolution equations which are compatible with this multifractal behaviour.
Dynamical Aspects in the Adoption of Agri-Environmental Measures
Authors: Weisbuch Gérard , Boudjema Gérard
Published: July 2002

We describe a simple model of the dynamics of adoption of agri-environmental measures by farmers in Europe. Farmers choices are based on their evaluation of the economic advantages of taking environmental premiums in exchange for environment friendly practices, plus imitation terms taking into account the information that they get from neighbours which have already made their own choice. We show that under a large set of social network topologies and hypotheses on distribution of farmers characteristics, the outcome of the social processes, namely premium uptake rate, depends upon local characteristics of farmers and their network. It is not directly related to average characteristics. Some conclusions and recommendations about policy implementation can then be driven.
Analysis of parallel replicated simulations under a completion time constraint
Authors: Glynn Peter W. , Heidelberger Philip
Published: July 2002

We analyze properties associated with a simple yet effective way to exploit parallel processors in discrete event simulations: averaging the results of multiple, independent replications that are run, in parallel, on multiple processors. We focus on estimating expectations from terminating simulations, or steady state parameters from regenerative simulations. We assume that there is a CPU time constraint,
t
, on each of
P
processors. Unless the replication lengths are bounded, one must be willing to simulate beyond any fixed, finite time
t
on at least some processors in order to always obtain a strongly consistent estimator (as the number of processors increases). We therefore consider simulation experiments in which
t
is viewed as either being a strict constraint, or a guideline, in which case simulation beyond time
t
is permitted. The statistical properties, including strong laws, central limit theorems, bias expansions, and completion time distributions of a variety of estimators obtainable from such an experiment are derived. We propose an unbiased estimator for a simple mean value. This estimator requires preselecting a fraction of the processors. Simulation beyond time
t
may be required on a preselected processor, but only if no replications have yet been completed on that processor. being a strict constraint, or a guideline, in which case simulation beyond time
t
is permitted. The statistical properties, including strong laws, central limit theorems, bias expansions, and completion time distributions of a variety of estimators obtainable from such an experiment are derived. We propose an unbiased estimator for a simple mean value. This estimator requires preselecting a fraction of the processors. Simulation beyond time
t
may be required on a preselected processor, but only if no replications have yet been completed on that processor.
A generalized envelope method for sparse factorization by rows
Authors: Liu Joseph W. H.
Published: July 2002

A generalized form of the envelope method is proposed for the solution of large sparse symmetric and positive definite matrices by rows. The method is demonstated to have practical advantages over the conventional column-oriented factorization using compressed column storage or the multifrontal method using full frontal submatrices.
Efficient at-most-once messages based on synchronized clocks
Authors: Liskov Barbara , Shrira Liuba , Wroclawski John
Published: July 2002

This paper describes a new at-most-once message passing protocol that provides guaranteed detection of duplicate messages even when the receiver has no state stored for the sender. It also discusses how to use at-most-once messages to implement higher-level primitives such as at-once-remote procedure calls and sequenced bytestream protocols. Our performance measurements indicate that at-most-once RPCs can provide at the same cost as less desirable forms of RPCs that do not guarantee at-most-once execution. Our method is based on the assumption that clocks throughout the system are loosely synchronized. Modern clock synchronization protocols provide good bounds on clock skew with high probability; our method depends on the bound for performance but not for correctness.
Color quantization by dynamic programming and principal analysis
Authors: Wu Xiaolin
Published: July 2002

Color quantization is a process of choosing a set of
K
representative colors to approximate the
N
colors of an image,
K < N
, such that the resulting
K
-color image looks as much like the original
N
-color image as possible. This is an optimization problem known to be NP-complete in
K
. However, this paper shows that by ordering the
N
colors along their principal axis and partitioning the color space with respect to this ordering, the resulting constrained optimization problem can be solved in
O
(
N
+
KM
2
) time by dynamic programming (where
M
is the intensity resolution of the device).

Traditional color quantization algorithms recursively bipartition the color space. By using the above dynamic-programming algorithm, we can construct a globally optimal
K
-partition,
K
>2, of a color space in the principal direction of the input data. This new partitioning strategy leads to smaller quantization error and hence better image quality. Other algorithmic issues in color quantization such as efficient statistical computations and nearest-neighbor searching are also studied. The interplay between luminance and chromaticity in color quantization with and without color dithering is investigated. Our color quantization method allows the user to choose a balance between the image smoothness and hue accuracy for a given
K
.
Experimental results from an automatic test case generator
Authors: DeMillo Richard A. , Offutt A. Jefferson
Published: July 2002

Constraint-based testing is a novel way of generating test data to detect specific types of common programming faults. The conditions under which faults will be detected are encoded as mathematical systems of constraints in terms of program symbols. A set of tools, collectively called Godzilla, has been implemented that automatically generates constraint systems and solves them to create test cases for use by the Mothra testing system. Experimental results from using Godzilla show that the technique can produce test data that is very close in terms of mutation adequacy to test data that is produced manually, and at substantially reduced cost. Additionally, these experiments have suggested a new procedure for unit testing, where test cases are viewed as throw-away items rather than scarce resources.
Motion planning in the presence of moving obstacles
Authors: Reif John , Sharir Micha
Published: July 2002

This paper investigates the computational complexity of planning the motion of a body B in 2-D or 3-D space, so as to avoid collision with moving obstacles of known, easily computed, trajectories. Dynamic movement problems are of fundamental importance to robotics, but their computational complexity has not previously been investigated.

We provide evidence that the 3-D dynamic movement problem is intractable even if B has only a constant number of degrees of freedom of movement. In particular, we prove the problem is PSPACE-hard if B is given a velocity modulus bound on its movements and is NP-hard even if B has no velocity modulus bound, where, in both cases, B has 6 degrees of freedom. To prove these results, we use a unique method of simulation of a Turing machine that uses time to encode configurations (whereas previous lower bound proofs in robotic motion planning used the system position to encode configurations and so required unbounded number of degrees of freedom).

We also investigate a natural class of dynamic problems that we call
asteroid avoidance problems
: B, the object we wish to move, is a convex polyhedron that is free to move by translation with bounded velocity modulus, and the polyhedral obstacles have known translational trajectories but cannot rotate. This problem has many applications to robot, automobile, and aircraft collision avoidance. Our main positive results are polynomial time algorithms for the 2-D asteroid avoidance problem, where B is a moving polygon and we assume a constant number of obstacles, as well as single exponential time or polynomial space algorithms for the 3-D asteroid avoidance problem, where B is a convex polyhedron and there are arbitrarily many obstacles. Our techniques for solving these asteroid avoidance problems use “normal path” arguments, which are an intereting generalization of techniques previously used to solve static shortest path problems.

We also give some additional positive results for various other dynamic movers problems, and in particular give polynomial time algorithms for the case in which B has no velocity bounds and the movements of obstacles are algebraic in space-time.
Counting networks
Authors: Aspnes James , Herlihy Maurice , Shavit Nir
Published: July 2002

Many fundamental multi-processor coordination problems can be expressed as
counting problems
: Processes must cooperate to assign successive values from a given range, such as addresses in memory or destinations on an interconnection network. Conventional solutions to these problems perform poorly because of synchronization bottlenecks and high memory contention.

Motivated by observations on the behavior of sorting networks, we offer a new approach to solving such problems, by introducing
counting networks
, a new class of networks that can be used to count. We give two counting network constructions, one of depth log
n
(1 + log
n
)/2 using
n
log

(1 + log
n
)/4 “gates,” and a second of depth log
2
n
using
n
log
2
n
/2 gates. These networks avoid the sequential bottlenecks inherent to earlier solutions and substantially lower the memory contention.

Finally, to show that counting networks are not merely mathematical creatures, we provide experimental evidence that they outperform conventional synchronization techniques under a variety of circumstances.
Sharing and protection in a single-address-space operating system
Authors: Chase Jeffrey S. , Levy Henry M. , Feeley Michael J. , Lazowska Edward D.
Published: July 2002

This article explores memory sharing and protection support in Opal, a single-address-space operating system designed for wide-address (64-bit) architectures. Opal threads execute within protection domains in a single shared virtual address space. Sharing is simplified, because addresses are context independent. There is no loss of protection, because addressability and access are independent; the right to access a segment is determined by the protection domain in which a thread executes. This model enables beneficial code-and data-sharing patterns that are currently prohibitive, due in part to the inherent restrictions of multiple address spaces, and in part to Unix programming style.

We have designed and implemented an Opal prototype using the Mach 3.0 microkernel as a base. Our implementation demonstrates how a single-address-space structure can be supported alongside of other environments on a modern microkernel operating system, using modern wide-address architectures. This article justifies the Opal model and its goals for sharing and protection, presents the system and its abstractions, describes the prototype implementation, and reports experience with integrated applications.
Universal switch modules for FPGA design
Authors: Chang Yao-Wen , Wong D. F. , Wong C. K.
Published: July 2002

A switch module
M
with
W
terminals on each side is said to be
universal
if every set of nets satisfying the dimensional constraint (i.e., the number of nets on each side of
M
is at most
W
) is simultaneously rout able through
M
. In this article, we present a class of universal switch modules. Each of our switch modules has 6
W
switches and
switch-module flexibility
three (i.e,

F
s

=3). We prove that no switch module with less than 6
W
switches can be universal. We also compare our switch modules with those used in the Xilinx XC4000 family FPGAs and the
antisymmetric
switch modules (with

F
S

=3) suggested by Rose and Brown [1991]. Although these two kinds of switch modules also have

F
S

=3 and 6
W
switches, we show that they are not universal. Based on combinatorial counting techniques, we show that each of our universal switch modules can accommodate up to 25% more routing instances, compared with the XC4000-type switch module of the same size. Experimental results demonstrate that our universal switch modules improve routability at the chip level. Finally, our work also provides a theoretical insight into the important observation by Rose and Brown [1991] (based on extensive experiments) that

F
S

=3 is often sufficient to provide high routability.
A shared, segmented memory system for an object-oriented database
Authors: Hornick Mark F. , Zdonik Stanley B.
Published: July 2002

This paper describes the basic data model of an object-oriented database and the basic architecture of the system implementing it. In particular, a secondary storage segmentation scheme and a transaction-processing scheme are discussed. The segmentation scheme allows for arbitrary clustering of objects, including duplicates. The transaction scheme allows for many different sharing protocols ranging from those that enforce serializability to those that are nonserializable and require communication with the server only on demand. The interaction of these two features is described such that segment-level transfer and object-level locking is achieved.
Concurrency in linear hashing
Authors: Ellis Carla Schlatter
Published: July 2002

Concurrent access to complex shared data structures, particularly structures useful as database indices, has long been of interest in the database community. In dynamic databases, tree structures such as B-trees have been used as indices because of their ability to handle growth; whereas hashing has been used for fast access in relatively static databases. Recently, a number of techniques for dynamic hashing have appeared. They address the major deficiency of traditional hashing when applied to databases that experience significant change in the amount of data being stored. This paper presents a solution that allows concurrency in one of these dynamic hashing data structures, namely linear hash files. The solution is based on locking protocols and minor modifications in the data structures.
Algorithm 757: MISCFUN, a software package to compute uncommon special functions
Authors: MacLeod Allan J.
Published: July 2002

MISCFUN (MISCellaneous FUNctions) is a Fortran package for the evaluation of several special functions, which are not used often enough to have been included in the standard libraries or packages. The package uses Chebyshev expansions as the underlying method of approximation, with the Chebyshev coefficients given to 20D. A wide variety of functions are included, and the package is designed so that other functions can be added in a standard manner.
LH*—a scalable, distributed data structure
Authors: Litwin Witold , Neimat Marie-Anna , Schneider Donovan A.
Published: July 2002

We present a scalable distributed data structure called LH*. LH* generalizes Linear Hashing (LH) to distributed RAM and disk files. An LH* file can be created from records with primary keys, or objects with OIDs, provided by any number of distributed and autonomous clients. It does not require a central directory, and grows gracefully, through splits of one bucket at a time, to virtually any number of servers. The number of messages per random insertion is one in general, and three in the worst case, regardless of the file size. The number of messages per key search is two in general, and four in the worst case. The file supports parallel operations, e.g., hash joins and scans. Performing a parallel operation on a file of
M
buckets costs at most 2
M
+ 1 messages, and between 1 and
O
(log
2
M
rounds of messages.

We first describle the basic LH* scheme where a coordinator site manages abucket splits, and splits a bucket every time a collision occurs. We show that the average load factor of an LH* file is 65%–70% regardless of file size, and bucket capacity. We then enhance the scheme with load control, performed at no additional message cost. The average load factor then increases to 80–95%. These values are about that of LH, but the load factor for LH* varies more.

We nest define LH* schemes without a coordinator. We show that insert and search costs are the same as for the basic scheme. The splitting cost decreases on the average, but becomes more variable, as cascading splits are needed to prevent file overload. Next, we briefly describe two variants of splitting policy, using parallel splits and presplitting that should enhance performance for high-performance applications.

All together, we show that LH* files can efficiently scale to files that are orders of magnitude larger in size than single-site files. LH* files that reside in main memory may also be much faster than single-site disk files. Finally, LH* files can be more efficient than any distributed file with a centralized directory, or a static parallel or distributed hash file.
Solving low-density subset sum problems
Authors: Lagarias J. C. , Odlyzko A. M.
Published: July 2002

The subset sum problem is to decide whether or not the 0-l integer programming problem

Σ
n
i=l
a
i
x
i

=
M
,
∀I
,

x
I

= 0 or 1, has a solution, where the

a
i

and
M
are given positive integers. This problem is NP-complete, and the difficulty of solving it is the basis of public-key cryptosystems of knapsack type. An algorithm is proposed that searches for a solution when given an instance of the subset sum problem. This algorithm always halts in polynomial time but does not always find a solution when one exists. It converts the problem to one of finding a particular short vector v in a lattice, and then uses a lattice basis reduction algorithm due to A. K. Lenstra, H. W. Lenstra, Jr., and L. Lovasz to attempt to find v. The performance of the proposed algorithm is analyzed. Let the
density d
of a subset sum problem be defined by
d
=
n
/log
2
(max
i

a
i

). Then for “almost all” problems of density
d
< 0.645, the vector v we searched for is the shortest nonzero vector in the lattice. For “almost all” problems of density
d
< 1/
n
, it is proved that the lattice basis reduction algorithm locates v. Extensive computational tests of the algorithm suggest that it works for densities
d
<

d
c

(
n
), where

d
c

(
n
) is a cutoff value that is substantially larger than 1/
n
. This method gives a polynomial time attack on knapsack public-key cryptosystems that can be expected to break them if they transmit information at rates below

d
c

(
n
), as
n
→ ∞.