bluuebunny/crossref_metadata_2025 huggingface dataset:
A CORRELATION ESTIMATE WITH APPLICATIONS TO QUANTUM SYSTEMS WITH COULOMB INTERACTIONS
Authors: GRAF GIAN MICHELE , SOLOVEJ JAN PHILIP
Published: July 2002

We consider some two-body operators acting on a Fock space with either fermionic or no statistics. We prove that they are bounded below by one-body operators which mimic exchange effects. This allows us to compare two-body correlations of fermionic and bosonic systems with those in Hartree-Fock, respectively Hartree theory. Applications of the fermionic estimate yield lower bounds for the ground state energy of jellium at high densities and of molecules with large nuclear charges.
Scaling Algebras and Renormalization Group in Algebraic Quantum Field Theory.
Authors: Buchholz D. , Verch R.
Published: July 2002

The concept of scaling algebra provides a novel framework for the general structural analysis and classification of the short distance properties of algebras of local observables in relativistic quantum field theory. In the present article this method is applied to the simple example of massive free field theory in s=1,2 and 3 spatial dimensions. Not quite unexpectedly, one obtains for s=2,3 in the scaling (short distance) limit the algebra of local observables in massless free field theory. The case s=1 offers, however, some surprises. There the algebra of observables acquires in the scaling limit a non-trivial center and describes charged physical states satisfying Gauss' law. The latter result is of relevance for the interpretation of the Schwinger model at short distances and illustrates the conceptual and computational virtues of the method.
FROM EUCLIDEAN FIELD THEORY TO QUANTUM FIELD THEORY
Authors: SCHLINGEMANN DIRK
Published: July 2002

In order to construct examples for interacting quantum field theory models, the methods of Euclidean field theory turned out to be powerful tools since they make use of the techniques of classical statistical mechanics.

Starting from an appropriate set of Euclidean n-point functions (Schwinger distributions), a Wightman theory can be reconstructed by an application of the famous Osterwalder–Schrader reconstruction theorem. This procedure (Wick rotation), which relates classical statistical mechanics and quantum field theory, is, however, somewhat subtle. It relies on the analytic properties of the Euclidean n-point functions.

We shall present here a C*-algebraic version of the Osterwalder–Schrader reconstruction theorem. We shall see that, via our reconstruction scheme, a Haag–Kastler net of bounded operators can directly be reconstructed.

Our considerations also include objects, like Wilson loop variables, which are not point-like localized objects like distributions. This point of view may also be helpful for constructing gauge theories.
A SPLITTING THEOREM FOR KÄHLER MANIFOLDS WHOSE RICCI TENSORS HAVE CONSTANT EIGENVALUES
Authors: APOSTOLOV VESTISLAV , DRĂGHICI TEDI , MOROIANU ANDREI
Published: July 2002

It is proved that a compact Kähler manifold whose Ricci tensor has two distinct constant non-negative eigenvalues is locally the product of two Kähler–Einstein manifolds. A stronger result is established for the case of Kähler surfaces. Without the compactness assumption, irreducible Kähler manifolds with Ricci tensor having two distinct constant eigenvalues are shown to exist in various situations: there are homogeneous examples of any complex dimension n ≥ 2 with one eigenvalue negative and the other one positive or zero; there are homogeneous examples of any complex dimension n ≥ 3 with two negative eigenvalues; there are non-homogeneous examples of complex dimension 2 with one of the eigenvalues zero. The problem of existence of Kähler metrics whose Ricci tensor has two distinct constant eigenvalues is related to the celebrated (still open) conjecture of Goldberg [24]. Consequently, the irreducible homogeneous examples with negative eigenvalues give rise to complete Einstein strictly almost Kähler metrics of any even real dimension greater than 4.
NEW POLARIZATIONS ON THE MODULI SPACES AND THE THURSTON COMPACTIFICATION OF TEICHMÜLLER SPACE
Authors: ANDERSEN JØRGEN ELLEGAARD
Published: July 2002

Given a foliation F with closed leaves and with certain kinds of singularities on an oriented closed surface Σ, we construct in this paper an isotropic foliation on ℳ(Σ), the moduli space of flat G-connections, for G any compact simple simply connected Lie-group. We describe the infinitesimal structure of this isotropic foliation in terms of the basic cohomology with twisted coefficients of F.

For any pair (F, g), where g is a singular metric on Σ compatible with F, we construct a new polarization on the symplectic manifold ℳ′(Σ), the open dense subset of smooth points of ℳ(Σ). We construct a sequence of complex structures on Σ, such that the corresponding complex structures on ℳ′(Σ) converges to the polarization associated to (F, g). In particular we see that the Jeffrey–Weitzman polarization on the SU(2)-moduli space is the limit of a sequence of complex structures induced from a degenerating family of complex structures on Σ, which converges to a point in the Thurston boundary of Teichmüller space of Σ. As a corollary of the above constructions, we establish a certain discontinuiuty at the Thurston boundary of Teichmüller space for the map from Teichmüller space to the space of polarizations on ℳ′(Σ).

For any reducible finite order diffeomorphism of the surface, our constuction produces an invariant polarization on the moduli space.
A QUANTUM NEURAL NETWORK MODEL
Authors: ANDRECUT M. , ALI M. K.
Published: July 2002

We present the algorithms necessary for the implementation of a quantum neural network with learning and classification tasks. A complete implementation for the classification and learning algorithms is given in terms of unitary quantum gates. Such a quantum neural network can be used to perform complex classification tasks or to solve the general problem of binary mapping.
THE MINIMUM BINDING ENERGY AND SIZE OF DOUBLY MUONIC D3 MOLECULE
Authors: ESKANDARI M. R. , FAGHIHI F. , MAHDAVI M.
Published: July 2002

The minimum energy and size of doubly muonic D3 molecule, which two of the electrons are replaced by the much heavier muons, are calculated by the well-known variational method. The calculations show that the system possesses two minimum positions, one at typically muonic distance and the second at the atomic distance. It is shown that at the muonic distance, the effective charge, z eff is 2.9. We assumed a symmetric planar vibrational model between two minima and an oscillation potential energy is approximated in this region.
PERTURBATION EXPANSION OF THE CONDUCTIVITY CORRECTION TO THE CASIMIR FORCE
Authors: BEZERRA V. B. , KLIMCHITSKAYA G. L. , ROMERO C.
Published: July 2002

The perturbation expansion of the finite conductivity correction to the Casimir force is obtained up to the sixth order in the small parameter which represents the relative penetration depth of electromagnetic zero-point oscillations into the metal. Configurations consisting of two plates and a spherical lens placed above a plate are considered. The perturbation results are shown to coincide with the results of numerical computations in the framework of plasma model to better than 1%. The influence of the errors in the value of effective plasma frequency onto the correction factor is estimated. The plasma model correction factor to the Casimir force is compared with the ones computed in the context of Drude model and on the base of optical tabulated data for the complex refractive index. The exactness of each model is determined.
EXACT SOLUTIONS OF THE SU(2) YANG–MILLS–HIGGS THEORY
Authors: TEH ROSY
Published: July 2002

Some exact static solutions of the SU(2) Yang–Mills–Higgs theory are presented. These solutions do satisfy the first order Bogomol'nyi equations, and possess infinite energy. They are axially symmetric and could possibly represent monopoles and an antimonopole sitting on the z-axis.
SPIN-CHARGE STRIPE STRUCTURE OF SUPERCONDUCTING YBa2Cu3O6+x
Authors: ARAI MASATOSHI , ENDOH YASUO , TAJIMA SETSUKO , BENNINGTON STEPHAN. M.
Published: July 2002

According to the recent neutron scattering data on YBCO, it has been concluded that the incommensurability of the spin dynamics is a common feature among oxide high-Tc superconductors, which cannot be explainable by Fermi surface anomaly. In this paper, we speculate a possible scenario of the mechanism of the superconductivity based upon an assumption of the stripe domain structures; RVB-like spin singlet formation plays a primary role for the attractive force for the Cooper pair formation of dopant holes existing in the adjacent charge chain site, which is separated by the spin stripes.
VARIATIONAL WAVE FUNCTIONS OF A VORTEX IN CYCLOTRON MOTION
Authors: TANG JIAN-MING
Published: July 2002

In two dimensions the microscopic theory, which provides a basis for the naive analogy between a quantized vortex in a superfluid and an electron in an uniform magnetic field, is presented. A one-to-one correspondence between the rotational states of a vortex in a cylinder and the cyclotron states of an electron in the central gauge is found. Like the Landau levels of an electron, the energy levels of a vortex are highly degenerate. However, the gap between two adjacent energy levels does not only depend on the quantized circulation, but also increases with the energy, and scales with the size of the vortex.
CORRELATION BETWEEN BULK AND SURFACE PHENOMENA IN Ga-(Bi,In) AND In-Bi LIQUID ALLOYS
Authors: AKINLADE O. , ALI I. , SINGH R. N.
Published: July 2002

Thermodynamic models are used to correlate the bulk and surface properties of mixing of Ga-(Bi,In) and In-Bi liquid alloys. It provides useful insight into the energetics of binary alloys (Ga-Bi, Ga-In and In-Bi) which are constituent components of ternary Ga-In-Bi alloys. The positive deviation of the properties of Ga-Bi and Ga-In alloys from the ideal mixing condition and negative deviation for In-Bi are discussed in terms of the interaction energies and hence a consistent set of different thermodynamic functions are obtained as a function of composition. Our calculations indicate that the surface of Ga-Bi is richer with Bi- atoms than in In-Bi. However, in atoms segregate to the surface of the Ga-In alloys.
ENERGY TRANSPORT IN A MESOSCOPIC THERMO-HYDRODYNAMICS
Authors: JOU DAVID , CASAS-VáZQUEZ JOSé , MADUREIRA JUSTINO. R. , VASCONCELLOS ÁUREA R. , LUZZI ROBERTO
Published: July 2002

We analyse the question of transport of energy in fluids, done, for specificity, for the case of a system of fermions interacting with a boson system. Resorting to a generalized thermo-hydrodynamics based on a nonequilibrium ensemble formalism, the so-called MaxEnt-NESOM, we derive the equations of evolution for the energy density and its first and second fluxes in a truncated description. We obtain a generalized Fourier's law, relating the flux of energy with extended thermodynamic forces which include contributions of the Guyer–Krumhansl–type. An extended evolution equation for the density of energy is derived, and the conditions when it goes over restricted forms of the type of the telegraphist equation and the traditional Fourier heat diffusion equation are discussed.
Optical Spectroscopy of Individual Photosynthetic Pigment Protein Complexes
Authors: Köhler J. , van Oijen A. M. , Ketelaars M. , Hofmann C. , Matsushita M. , Aartsma T. J. , Schmidt J.
Published: July 2002

Photosynthesis is the process by which plants, algae and photosynthetic bacteria convert solar energy into a form that can be used to sustain the life process. The light reactions occur in closely coupled pigment systems. The energy is absorbed by a network of antenna pigment proteins and efficiently transferred to the photochemical reaction centre where a charge separation takes place providing the free energy for subsequent chemical reactions. The total conversion process, starting with the absorption of a photon and ending with a stable charge separated state occurs within less than 50 ps and has an overall quantum yield of more than 90%. The success of this natural process is based on both the highly efficient absorption of photons by the light-harvesting antenna system and the rapid and efficient transfer of excitation energy to the reaction centre.

It is known that most photosynthetic purple bacteria contain two types of antenna complexes, light-harvesting complex 1 (LH1) and light harvesting complex 2 (LH2) which both have a ring-like structure [1,2]. (Some bacterial species like Rhodopseudomonas acidophila contain a third light-harvesting complex termed B800-820.) The reaction centre (RC) presumably forms the core of the LH1 complex, while LH2 complexes are arranged around the perimeter of the LH1 ring in a two-dimensional structure. However the full three-dimensional structure of the whole photosynthetic unit is as yet unknown. The absorption of a photon (mainly) takes place in the LH2 pigments followed by a fast transfer of the excitation energy to the LH1 complex and subsequently to the reaction centre. It appears that the whole structure is highly optimized for capturing light energy and to funnel it to the reaction centre [3-7].
LOW TEMPERATURE GROWTH OF ALIGNED CARBON NANOTUBES IN LARGE AREA
Authors: LIN P. H. , LIN C. R. , CHEN K. H. , CHEN L. C.
Published: July 2002

We have synthesized well-aligned, uniform carbon nanotubes (CNTs) in large area at low temperature of 500°C using microwave plasma- enhanced chemical vapor deposition on silicon and Corning glass 7059. This is a two-step process in that ion beam sputtering deposition was used to deposit iron catalyst thin films and followed by hydrogen plasma pretreatment to form nano-size Fe particles before the CNTs growth at the second step. The thickness of Fe catalyst thin film was found to be the most important factor in the low temperature CNTs growth process. Systematic control of the length, diameter, and alignment of the CNTs has been achieved by changing the deposition parameters such us microwave power, pressure, temperature and the thickness of Fe catalyst. High resolution SEM and TEM were used to characterize the morphology and structure of the nanotubes. Field emission measurement showed a low turn on field (6.2 V/m) and high emission current density (0.1 mA/cm2 at 9 V/m) for the films grown at low temperature of 500°C.
ONSAGER'S ALGEBRA AND PARTIALLY ORTHOGONAL POLYNOMIALS
Authors: VON GEHLEN G.
Published: July 2002

The energy eigenvalues of the superintegrable chiral Potts model are determined by the zeros of special polynomials which define finite representations of Onsager's algebra. The polynomials determining the low-sector eigenvalues have been given by Baxter in 1988. In the ℤ3-case they satisfy 4-term recursion relations and so cannot form orthogonal sequences. However, we show that they are closely related to Jacobi polynomials and satisfy a special "partial orthogonality" with respect to a Jacobi weight function.
PYGMY RESONANCES IN ARTIFICIAL NUCLEI: FAR-INFRARED ABSORPTION BY ELECTRON–HOLE DROPLETS
Authors: CAPOTE ROBERTO , DELGADO ALAIN , GONZALEZ AUGUSTO
Published: July 2002

The structure of E1 resonances has been examined in a microscopic random phase approximation calculation for neutral, symmetric, closed shell and electron–hole systems in a quantum dot. The number of electron–hole pairs, N, is varied from 6 to 42. The occurrence of small, but distinct, E1 peaks in the far-infrared spectra located in the low energy tail of the giant dipole resonance consisting of highly coherent electron–hole excitations is predicted. These pygmy resonances account for about 2% of the dipole energy-weighted photoabsorption sum rule. A very weak dependence of the average pygmy resonance energy on the number of electron–hole pairs is found.
A 92.5 K REBa2Cu3O7-δ SUPERCONDUCTOR STARTING FROM NATURAL MIXTURE OF RARE EARTH ELEMENTS
Authors: RODRIGUES P. , JURELO A. R. , FLEMMING J.
Published: July 2002

The processing and characterization of a REBa 2 Cu 3 O 7-δ, sample superconductor is described, where RE corresponds to a natural mixture of rare earth elements extracted from xenotime mineral. This mixture contains no Pr and, contrary to previous studies, can substitute the yttrium atom in YBa 2 Cu 3 O 7-δ, (YBCO) without deleterious effects in structural and superconducting properties, as measured by X-ray diffraction, resistivity and magnetoresistivity. Our sample presented T c =92.5 K and average lattice parameters a=3.821 Å, b=3.896 Å and c=11.686 Å, which are very similar to YBCO properties. Considering that the process of separation of Y (and other pure rare earth elements) from any natural mixture involves high costs, our system represents a practical alternative to YBCO compound.
VIBRATIONAL SPECTROSCOPY OF CO/Cu(211) WITH A CO TERMINATED TIP
Authors: MORESCO FRANCESCA , MEYER GERHARD , RIEDER KARL HEINZ
Published: July 2002

Vibrational excitations of an isolated CO molecule adsorbed on a Cu(211) surface have been, for the first time, observed with a CO terminated scanning tunneling microscope tip. Both the frustrated translational and rotational modes were observed, and in agreement with the case of a metallic tip. The presence of a CO molecule on the tip, transferred by controlled vertical manipulation, strongly influences the frustrated translational mode of the CO molecule, while it does not affect the frustrated rotational mode. The present work demonstrates that scanning tunneling vibrational spectroscopy is also possible with a molecule at the end of the tip, opening new interesting fields of research and putting some more light on the still open question of inelastic tunneling and its selection rules.
HIDDEN MARKOV MODELS FOR MODELING AND RECOGNIZING GESTURE UNDER VARIATION
Authors: WILSON ANDREW D. , BOBICK AARON F.
Published: July 2002

Conventional application of hidden Markov models to the task of recognizing human gesture may suffer from multiple sources of systematic variation in the sensor outputs. We present two frameworks based on hidden Markov models which are designed to model and recognize gestures that vary in systematic ways. In the first, the systematic variation is assumed to be communicative in nature, and the input gesture is assumed to belong to gesture family. The variation across the family is modeled explicitly by the parametric hidden Markov model (PHMM). In the second framework, variation in the signal is overcome by relying on online learning rather than conventional offline, batch learning.
A GENERAL APPROACH IN THE DESIGN OF ACTIVE CONTROLLERS FOR NONLINEAR SYSTEMS EXHIBITING CHAOS
Authors: SINHA S. C. , HENRICHS J. T. , RAVINDRA B.
Published: July 2002

A general framework for local control of nonlinearity in nonautonomous systems using feedback strategies is considered in this work. In particular, it is shown that a system exhibiting chaos can be driven to a desired periodic motion by designing a combination of feedforward controller and a time-varying controller. The design of the time-varying controller is achieved through an application of Lyapunov–Floquet transformation which guarantees the local stability of the desired periodic orbit. If it is desired that the chaotic motion be driven to a fixed point, then the time-varying controller can be replaced by a constant gain controller which can be designed using classical techniques, viz. pole placement, etc. A sinusoidally driven Duffing's oscillator and the well-known Rossler system are chosen as illustrative examples to demonstrate the application.
FUZZY DECISIONS IN MODULAR NEURAL NETWORKS
Authors: MIZRAJI EDUARDO , LIN JUAN
Published: July 2002

Modular neural networks structured as associative memories are capable of processing inputs built from tensorial products of vectors. In this context, the operators of propositional and modal logic can be represented as modular distributed memories that can process not only classical Boolean but also fuzzy evaluations of truth-values of sentences. Furthermore, projecting memory outputs onto unit vectors yield discrete dynamical systems that exhibit varying degrees of complexity. As examples, we analyze outcomes of semantic evaluations in several self-referential systems including modal versions of the chaotic liar, antagonistic decisions and extended dilemmas. By studying these examples we hope to shed some light on the modeling of cognitive decisions.
IMPROVED CORRELATION DIMENSION CALCULATION
Authors: SPROTT J. C. , ROWLANDS G.
Published: July 2002

For many chaotic systems, accurate calculation of the correlation dimension from measured data is difficult because of very slow convergence as the scale size is reduced. This problem is often caused by the highly nonuniform measure on the attractor. This paper proposes a method for collecting data at large scales and extrapolating to the limit of zero scale. The result is a vastly reduced required number of data points for a given accuracy in the measured dimension. The method is illustrated in detail for one-dimensional maps and then applied to more complicated maps and flows. Values are given for the correlation dimension of many standard chaotic systems.
RIDDLED BASINS AND UNSTABLE DIMENSION VARIABILITY IN CHAOTIC SYSTEMS WITH AND WITHOUT SYMMETRY
Authors: VIANA RICARDO L. , GREBOGI CELSO
Published: July 2002

Riddling occurs in dissipative dynamical systems with more than one attractor, when the basin of one attractor is punctured with holes belonging to the basins of the other attractors. The basin of a chaotic attractor is riddled if (i) it has a positive Lebesgue measure; (ii) in the vicinity of every point belonging to the basin of the attractor, there is a positive Lebesgue measure set of points that asymptote to another attractor. We investigate the presence of riddled basins in a two-dimensional noninvertible map with a symmetry-breaking term. In the symmetric case the onset of riddling is characterized by an unstable–unstable pair bifurcation, which also leads to unstable dimension variability in the invariant chaotic set. The nonsymmetric case exhibits a chaotic attractor, but a riddled basin occurs only at the bifurcation point, since after that the attractor becomes a chaotic saddle. We analyze the presence of unstable dimension variability in the symmetric case by computing the finite-time transverse Lyapunov exponents. We point out some consequences of those facts to the synchronization properties of coupled chaotic systems.
ℓ∞-COHOMOLOGY AND METABOLICITY OF NEGATIVELY CURVED COMPLEXES
Authors: MINEYEV IGOR
Published: July 2002

We prove the analog of de Rham's theorem for ℓ∞-cohomology of the universal cover of a finite simplicial complex. A sufficient criterion is given for linearity of isoperimetric functions for filling cycles of any positive dimension over ℝ. This implies the linear higher dimensional isoperimetric inequalities for the fundamental groups of finite negatively curved complexes and of closed negatively curved manifolds. Also, these groups are ℝ-metabolic.
LOOP CONSTRAINTS: A HABITAT AND THEIR ALGEBRA
Authors: LEWANDOWSKI JERZY , MAROLF DONALD
Published: July 2002

This work introduces a new space [Formula: see text] of 'vertex-smooth' states for use in the loop approach to quantum gravity. Such states provide a natural domain for Euclidean Hamiltonian constraint operators of the type introduced by Thiemann (and using certain ideas of Rovelli and Smolin). In particular, such operators map [Formula: see text] into itself, and so are actual operators in this space. Their commutator can be computed on [Formula: see text] and compared with the classical hypersurface deformation algebra. Although the classical Poisson bracket of Hamiltonian constraints yields an inverse metric times an infinitesimal diffeomorphism generator, and despite the fact that the diffeomorphism generator has a well-defined nontrivial action on [Formula: see text], the commutator of quantum constraints vanishes identically for a large class of proposals.
THE ADSORPTION GEOMETRY OF BENZOIC ACID ON Ni(110)
Authors: NEUBER M. , ZHARNIKOV M. , WALZ J. , GRUNZE M.
Published: July 2002

The adsorption geometry of benzoic acid on Ni(110) was investigated by X-ray photoelectron spectroscopy, angle-resolved near edge X-ray absorption fine structure spectroscopy at the C1s and O1s excitation edges, and thermal desorption spectroscopy. At a substrate temperature of 360 K and saturation coverage the adsorbate forms a benzoate with molecules adsorbed on the surface via two equivalent oxygen atoms. For this dense adsorbate layer the molecular plane was found to be azimuthally rotated by about ± 30° with respect to the [Formula: see text] surface azimuth and tilted by ≈ 30° with respect to the surface normal. At about half the saturation coverage some rearrangement of molecules occurs in such a way that their planes become directed along the [001] surface direction, which is different from the adsorption geometry observed after annealing the saturated layer. At even smaller coverage the benzoate molecules appear to adsorb with their molecular planes nearly parallel to the surface. Semiempirical quantum-mechanical cluster calculations indicate that the carboxylate oxygens favor the highly coordinated sites in the [Formula: see text]-oriented troughs of the Ni(110) surface. Possible adsorption models are discussed.
ASYMMETRICAL INFORMATION AND INCOMPLETE MARKETS
Authors: GRORUD AXEL , PONTIER MONIQUE
Published: July 2002

This paper is an extension of [13] where we have studied a financial market with informed and non-informed agents. The informed agent has an initial insider information. We analyze the completeness of the market and the family of risk-neutral probabilities. Some cases of arbitrage opportunities are done.
PARTITION-BASED ENTROPIES OF DETERMINISTIC AND STOCHASTIC MAPS
Authors: EBELING W. , STEUER R. , TITCHENER M. R.
Published: July 2002

In this paper we explore the relationship between the Kolmogorov–Sinai entropy, the sum of positive Lyapunov exponents, denoted here as the Pesin entropy and a new measure, the T-entropy, for nonlinear maps. We demonstrate that threshold-crossing partitions are effective in deriving representative symbolic realisations for the real-valued time series. We describe the recently developed entropy measure for finite strings and compare with values derived from the application of Shannon's theory. These techniques are further applied to a simple stochastic system, appearing to further confirm recent theoretical results on Lyapunov exponents.
VIRTUAL MANUFACTURING: AN IMPORTANT ASPECT OF COLLABORATIVE PRODUCT COMMERCE
Authors: SHRIDHAR JOSHI MANDAR , RAVI SHAILENDRA
Published: July 2002

The sweeping changes in the web-related technologies in the late 1990s have brought paradigm shift in the business environment and strategic thinking of the organizations. To remain competitive in this ever-changing business scenario, the organizations are focusing more and more on the globalization of businesses and collaboration in the product development across the value chain. This phenomenon has given rise to a new business concept — Collaborative Product Commerce (CPC) that applies web-related technologies for the integration of various value-chain constituents from suppliers to customers. It focuses on cross-enterprise teams to share the intellectual capital in real time to reduce the time-to-market in the product development life cycle.

Manufacturing is the central activity that encompasses product, process, resources and plant. Manufacturing activities across the enterprises with real time exchange of information result in the optimization of design, resources and processes, which is in the true spirit of collaborative product commerce.

One of the most important facilitators of the collaborative aspects of manufacturing is the virtualization of the manufacturing process components. It involves various visualization and data integration aspects. To deliver value added solutions in this area, it is imperative to have thorough expertise in the engineering services.

The focus of this paper will be on virtualization aspects of manufacturing in a collaborative environment. Important paradigms of virtual manufacturing such as design-centered, production-centered and control-centered virtualization will be first discussed in brief. Virtualization of important components of manufacturing such as process planning and design, equipment designs and factory layout and resource management will be discussed in details. To conclude, significance of virtualization of manufacturing in terms of business benefits in the collaborative product development environment will be considered.
Algebraic surface design with Hermite interpolation
Authors: Bajaj Chanderjit L. , Ihm Insung
Published: July 2002

This paper presents an efficient algorithm called Hermite interpolation, for constructing low-degree algebraic surfaces, which contain, with

C
1

or tangent plane continuity, any given collection of points and algebraic space curves having derivative information. Positional as well as derivative constraints on an implicitly defined algebraic surface are translated into a homogeneous linear system, where the unknowns are the coefficients of the polynomial defining the algebraic surface. Computaional details of the Hermite interpolation algorithm are presented along with several illustrative applications of the interpolation technique to construction of joining or blending surfaces for solid models as well as fleshing surfaces for curved wire frame models. A heuristic approach to interactive shape control of implicit algebraic surfaces is also given, and open problems in algebraic surface design are discussed.
A model of authorization for next-generation database systems
Authors: Rabitti Fausto , Bertino Elisa , Kim Won , Woelk Darrell
Published: July 2002

The conventional models of authorization have been designed for database systems supporting the hierarchical, network, and relational models of data. However, these models are not adequate for next-generation database systems that support richer data models that include object-oriented concepts and semantic data modeling concepts. Rabitti, Woelk, and Kim [14] presented a preliminary model of authorization for use as the basis of an authorization mechanism in such database systems. In this paper we present a fuller model of authorization that fills a few major gaps that the conventional models of authorization cannot fill for next-generation database systems. We also further formalize the notion of implicit authorization and refine the application of the notion of implicit authorization to object-oriented and semantic modeling concepts. We also describe a user interface for using the model of authorization and consider key issues in implementing the authorization model.
Performance evaluation of programs related to the real gamma function
Authors: Cody W. J.
Published: July 2002

Methods are presented for evaluating the performance of programs for the functions Γ(
x
), ln Γ(
x
), and ψ(
x
). Accuracy estimates are based on comparisons using the manipulation theorem. Ideas for checking robustness are also given, and details on specific implementations of test programs are included.
On computational aspects of bounded linear least squares problems
Authors: Dax Achiya
Published: July 2002

The paper describes numerical experiments with active set methods for solving bounded linear least squares problems. It concentrates on two problems that arise in the implementation of the active set method. One problem is the choice of a good starting point. The second problem is how to move out of a “
dead point
.” The paper investigates the use of simple iterative methods to solve these problems. The results of our experiments indicate that the use of Gauss-Seidel iterations to obtain a starting point is likely to provide large gains in efficiency. Another interesting conclusion is that dropping one constraint at a time is advantageous to dropping several constraints at a time.
On finding the closest bitwise matches in a fixed set
Authors: Klier Peter , Fateman Richard J.
Published: July 2002

In a given large fixed table of bit-vectors, we would like to find, as rapidly as possible, those bit-vectors which have the least Hamming distances from a newly-presented arbitrary bit-vector.
Architectural support for reduced register saving/restoring in single-window register files
Authors: Huguet Miquel , Lang Tomás
Published: July 2002

The use of registers in a processor reduces the data and instruction memory traffic. Since this reduction is a significant factor in the improvement of the program execution time, recent VLSI processors have a large number of registers which can be used efficiently because of the advances in compiler technology. However, since registers have to be saved/restored across function calls, the corresponding register saving and restoring (RSR) memory traffic can almost eliminate the overall reduction. This traffic has been reduced by compiler optimizations and by providing multiple-window register files. Although these multiple-window architectures produce a large reduction in the RSR traffic, they have several drawbacks which make the single-window file preferable. We consider a combination of
hardware support
and
compiler optimizations
to reduce the RSR traffic for a single-window register file, beyond the reductions achieved by compiler optimizations alone. Basically, this hardware keeps track of the registers that are written during execution, so that the number of registers saved is minimized. Moreover, hardware is added so that a register is saved in the activation record of the function that uses it (instead of in the record of the current function); in this way a register is restored only when it is needed, rather than wholesale on procedure return. We present a register saving and restoring policy that makes use of this hardware, discuss its implementation, and evaluate the traffic reduction when the policy is combined with intraprocedural and interprocedural compiler optimizations. We show that, on the average for the four general-purpose programs measured, the RSR traffic is reduced by about 90 percent for a small register file (i.e., 32 registers), which results in an overall data memory traffic reduction of about 15 percent.
How the Nintendo generation learns
Authors: Soloway Elliot
Published: July 2002

Recently, I was chatting with my son, Daniel (age 7) about Nintendo. I asked him if he could bring it in to school for show and tell and he was horrified! “No,” he exclaimed, “that's not for learning.” Well, what do
you,
dear reader, think about that? Is Nintendo for learning? No one is watching/listening … go ahead … admit it …
You don't really like Nintendo
. (Of course, when you play Tetris, that is exercising problem-solving skills. Right.) And, afterall, you didn't use all that technology in school, and you learned just fine. So, why do “kids these days” need all this new multimedia technology, anyhow? That technology just makes it fun and easy to learn—it's just glitz. And as for calculators.....
Simple conditions for guaranteeing higher normal forms in relational databases
Authors: Date C. J. , Fagin Ronald
Published: July 2002

A key is
simple
if it consists of a single attribute. It is shown that if a relation schema is in third normal form and every key is simple, then it is in projection-join normal form (sometimes called fifth normal form), the ultimate normal form with respect to projections and joins. Furthermore, it is shown that if a relation schema is in Boyce-Codd normal form and
some
key is simple, then it is in fourth normal form (but not necessarily projection-join normal form). These results give the database designer simple sufficient conditions, defined in terms of functional dependencies alone, that guarantee that the schema being designed is automatically in higher normal forms.
Gaining efficiency in transport services by appropriate design and implementation choices
Authors: Watson Richard W. , Mamrak Sandy A.
Published: July 2002

End-to-end transport protocols continue to be an active area of research and development involving (1) design and implementation of special-purpose protocols, and (2) reexamination of the design and implementation of general-purpose protocols. This work is motivated by the perceived low bandwidth and high delay, CPU, memory, and other costs of many current general-purpose transport protocol designs and implementations. This paper examines transport protocol mechanisms and implementation issues and argues that general-purpose transport protocols can be effective in a wide range of distributed applications because (1) many of the mechanisms used in the special-purpose protocols can also be used in general-purpose protocol designs and implementations, (2) special-purpose designs have hidden costs, and (3) very special operating system environments, overall system loads, application response times, and interaction patterns are required before general-purpose protocols are the main system performance bottlenecks.
Precise computation using range arithmetic, via C++
Authors: Aberth Oliver , Schaefer Mark J.
Published: July 2002

An arithmetic is described that can replace floating-point arithmetic for programming tasks requiring assured accuracy. A general explanation is given of how the arithmetic is constructed with C++, and a programming example in this language is supplied. Times for solving representative problems are presented.
Distributed real-time system specification and verification in APTL
Authors: Wang Farn , Mok Aloysius K. , Emerson E. Allen
Published: July 2002

In this article, we propose a language, Asynchronous Propositional Temporal Logic (APTL), for the specification and verification of distributed hard real-time sytems. APTL extends the logic TPTL by dealing explicitly with multiple local clocks. We propose a distributed-system model which permits definition of inequalities asserting the temporal precedence of local clock readings. We show the expressiveness of APTL through two nontrivial examples. Our logic can be used to specify and reason about such important properties as bounded clock rate drifting. We then give a 2

2
0(n)

tableau-based decision procedure for determining APTL satisfiability, where
n
is the size (number of bits) of the input formula.
On the
k
-server conjecture
Authors: Koutsoupias Elias , Papadimitriou Christos H.
Published: July 2002

We prove that the
work function algorithm
for the
k
-server problem has a competitive ratio at most 2
k
−1. Manasse et al. [1988] conjectured that the competitive ratio for the
k
-server problem is exactly
k
(it is trivially at least
k
); previously the best-known upper bound was exponential in
k
. Our proof involves three crucial ingredients: A
quasiconvexity property
of work functions, a
duality lemma
that uses quasiconvexity to characterize the configuration that achieve maximum increase of the work function, and a
potential function
that exploits the duality lemma.
Performance analysis of redundant-path networks for multiprocessor systems
Authors: Padmanabhan Krishnan , Lawrie Duncan H.
Published: July 2002

Performance of a class of multistage interconnection networks employing redundant paths is investigated. Redundant path networks provide significant tolerance to faults at minimal costs; in this paper improvements in performance and very graceful degradation are also shown to result from the availability of redundant paths. A Markov model is introduced for the operation of these networks in the circuit-switched mode and is solved numerically to obtain the performance measures of interest. The structure of the networks that provide maximal performance is also characterized.
The design of a new frontal code for solving sparse, unsymmetric systems
Authors: Duff I. S. , Scott J. A.
Published: July 2002

We describe the design, implementation, and performance of a frontal code for the solution of large, sparse, unsymmetric systems of linear equations. The resulting software package, MA42, is included in Release 11 of the Harwell Subroutine Library and is intended to supersede the earlier MA32 package. We discuss in detail the extensive use of higher-level BLAS kernels within MA42 and illustrate the performance on a range of practical problems on a CRAY Y-MP, an IBM 3090, and an IBM RISC System/6000. We examine extending the frontal solution scheme to use multiple fronts to allow MA42 to be run in parallel. We indicate some directions for future development.
Algorithm 754: Fortran subroutines for approximate solution of dense quadratic assignment problems using GRASP
Authors: Resende Mauricio G. C. , Pardalos Panos M. , Li Yong
Published: July 2002

In the NP-complete quadratic assignment problem (QAP),
n
facilities are to be assigned to
n
sites at minimum cost. The contribution of assigning facility
i
to site
k
and facility
j
to site
l
to the total cost is

f
ij

d
kl

, where

f
ij

is the flow between facilities
i
and
j
, and

d
kl

is the distance between sites
k
and
l
. Only very small (
n
≤20) instances of the QAP have been solved exactly, and heuristics are therefore used to produce approximate solutions. This article describes a set of Fortran subroutines to find approximate solutions to dense quadratic assignment problems, having at least one symmetric flow or distance matrix. A greedy, randomized, adaptive search procedure (GRASP) is used to produce the solutions. The design and implementation of the code are described in detail, and extensive computational experiments are reported, illustrating solution quality as a function of running time.
Formalizing style to understand descriptions of software architecture
Authors: Abowd Gregory D. , Allen Robert , Garlan David
Published: July 2002

The software architecture of most systems is usually described informally and diagrammatically by means of boxes and lines. In order for these descriptions to be meaningful, the diagrams are understood by interpreting the boxes and lines in specific, conventionalized ways. The informal, imprecise nature of these interpretations has a number of limitations. In this article we consider these conventionalized interpretations as architectural styles and provide a formal framework for their uniform definition. In addition to providing a template for precisely defining new architectural styles, this framework allows for analysis within and between different architectural styles.
How many queries are needed to learn?
Authors: Hellerstein Lisa , Pillaipakkamnatt Krishnan , Raghavan Vijay , Wilkins Dawn
Published: July 2002

We investigate the query complexity of exact learning in the membership and (proper) equivalence query model. We give a complete characterization of concept classes that are learnable with a polynomial number of polynomial sized queries in this model. We give applications of this characterization, including results on learning a natural subclass of DNF formulas, and on learning with membership queries alone. Query complexity has previously been used to prove lower bounds on the time complexity of exact learning. We show a new relationship between query complexity and time complexity in exact learning: If any “honest” class is exactly and properly learnable with polynomial query complexity, but not learnable in polynomial time, then P = NP. In particular, we show that an honest class is exactly polynomial-query learnable if and only if it is learnable using an oracle for Γ
p
4
.
Software unit test coverage and adequacy
Authors: Zhu Hong , Hall Patrick A. V. , May John H. R.
Published: July 2002

Objective measurement of test quality is one of the key issues in software testing. It has been a major research focus for the last two decades. Many test criteria have been proposed and studied for this purpose. Various kinds of rationales have been presented in support of one criterion or another. We survey the research work in this area. The notion of adequacy criteria is examined together with its role in software dynamic testing. A review of criteria classification is followed by a summary of the methods for comparison and assessment of criteria.
Electronic mail as a coalition-building information technology
Authors: Romm Celia T. , Pliskin Nava
Published: July 2002

One of the most intriguing lines of research within the literature on diffusion of information technologies (IT) is the study of the power and politics of this process. The major objective of this article is to build on the work of Kling and Markus on power and IT, by extending their perspective to email. To demonstrate how email can be used for political purposes within an organizational context, a case study is presented. The case study describes a series of events which took place in a university. In the case, email was used by a group of employees to stage a rebellion against the university president. The discussion demonstrates that email features make it amenable to a range of political uses. The article is concluded with a discussion of the implications from this case to email research and practice.
Database description with SDM
Authors: Hammer Michael , Mc Leod Dennis
Published: July 2002

SDM is a high-level semantics-based database description and structuring formalism (database model) for databases. This database model is designed to capture more of the meaning of an application environment than is possible with contemporary database models. An SDM specification describes a database in terms of the kinds of entities that exist in the application environment, the classifications and groupings of those entities, and the structural interconnections among them. SDM provides a collection of high-level modeling primitives to capture the semantics of an application environment. By accommodating derived information in a database structural specification, SDM allows the same information to be viewed in several ways; this makes it possible to directly accommodate the variety of needs and processing requirements typically present in database applications. The design of the present SDM is based on our experience in using a preliminary version of it.

SDM is designed to enhance the effectiveness and usability of database systems. An SDM database description can serve as a formal specification and documentation tool for a database; it can provide a basis for supporting a variety of powerful user interface facilities, it can serve as a conceptual database model in the database design process; and, it can be used as the database model for a new kind of database management system.
Distributed deadlock detection algorithm
Authors: Obermarck Ron
Published: July 2002

We propose an algorithm for detecting deadlocks among transactions running concurrently in a distributed processing network (i.e., a distributed database system). The proposed algorithm is a distributed deadlock detection algorithm. A proof of the correctness of the distributed portion of the algorithm is given, followed by an example of the algorithm in operation. The performance characteristics of the algorithm are also presented.
Operational characteristics of a harware-based pattern matcher
Authors: Haskin Roger L. , Hollaar Lee A.
Published: July 2002

The design and operation of a new class of hardware-based pattern matchers, such as would be used in a backended database processor in a full-text or other retrieval system, is presented. This recognizer is based on a unique implementation technique for finite state automata consisting of partitioning the state table among a number of simple digital machines. It avoids the problems generally associated with implementing finite state machines, such as large state table memories, complex control mechanisms, and state encodings. Because it consists primarily of memory, with its high regularity and density, needs only limited static interconnections, and operates at a relatively low speed, it can be easily constructed using integrated circuit techniques.

After a brief discussion of other pattern-matching hardware, the structure and operation of the partitioned finite state automaton is given, along with a simplified discussion of how the state tables are partitioned. The expected performance of the resulting system and the state table partitioning programs is then discussed.