bluuebunny/crossref_metadata_2025 huggingface dataset:
Finding Rectilinear Paths Among Obstacles in a Two-Layer Interconnection Model
Authors: Lee D. T. , Yang C. D , Wong C. K.
Published: October 2003

Finding the best rectilinear path with respect to the bends and teh lengths of paths connecting two given points in the presence of rectilinear obstacles in a two-layer model is studied in this paper. In this model, rectilinear obstacles on each layer are specified separately, and the orientation of routing in each layer is fixed. An algorithm is presented to transform any problem instance in the two-layer model to one in a one-layer model, so that almost all algorithms for finding rectilinear paths among obstacles in the plane can be applied. The transformation algorithm runs in O(e log e) time where e is the number of edges on obstacles lying on both layers. A direct graph-theoretic approach to finding a shortest path in the two-layer model, which is easier to implement is also presented. The algorithm runs in O(e log 2 e) time.
Software Quality Classification Modeling Using the SPRINT Decision Tree Algorithm
Authors: Khoshgoftaar Taghi M. , Seliya Naeem
Published: October 2003

Predicting the quality of system modules prior to software testing and operations can benefit the software development team. Such a timely reliability estimation can be used to direct cost-effective quality improvement efforts to the high-risk modules. Tree-based software quality classification models based on software metrics are used to predict whether a software module is fault-prone or not fault-prone. They are white box quality estimation models with good accuracy, and are simple and easy to interpret.

An in-depth study of calibrating classification trees for software quality estimation using the SPRINT decision tree algorithm is presented. Many classification algorithms have memory limitations including the requirement that datasets be memory resident. SPRINT removes all of these limitations and provides a fast and scalable analysis. It is an extension of a commonly used decision tree algorithm, CART, and provides a unique tree pruning technique based on the Minimum Description Length (MDL) principle. Combining the MDL pruning technique and the modified classification algorithm, SPRINT yields classification trees with useful accuracy. The case study used consists of software metrics collected from a very large telecommunications system. It is observed that classification trees built by SPRINT are more balanced and demonstrate better stability than those built by CART.
Active Tracking and Cloning of Facial Expressions Using Spatio-Temporal Information
Authors: Yin Lijun , Basu Anup , Yourst Matt T.
Published: October 2003

This paper presents a new method to analyze and synthesize facial expressions, in which a spatio-temporal gradient based method (i.e., optical flow) is exploited to estimate the movement of facial feature points. We proposed a method (called motion correlation) to improve the conventional block correlation method for obtaining motion vectors. The tracking of facial expressions under an active camera is addressed. With the motion vectors estimated, a facial expression can be cloned by adjusting the existing 3-D facial model, or synthesized by using different facial models. The experimental results demonstrate that the approach proposed is feasible for applications such as low bit rate video coding and face animation.
Computing with Bees: Attacking Complex Transportation Engineering Problems
Authors: Lučić Panta , Teodorović Dušan
Published: October 2003

The Bee System (an artificial bee swarm) is introduced in this paper. The proposed approach is applied to the Traveling Salesman Problem. The obtained results are very promising. The potential applications of the developed Bee System in the field of transportation engineering are discussed. The Bee System represents the new, successful application of emergent techniques based on natural metaphors, such as simulated annealing, genetic algorithms, and neural networks, to the complex engineering and management problems.
The Intrinsic Derivative and Centrifugal Forces in General Relativity: I.
Authors: Bini Donato , Carini Paolo , Jantzen Robert T.
Published: October 2003

Everyday experience with centrifugal forces has always guided thinking on the close relationship between gravitational forces and accelerated systems of reference. Once spatial gravitational forces and accelerations are introduced into general relativity through a splitting of spacetime into space-plus-time associated with a family of test observers, one may further split the local rest space of those observers with respect to the direction of relative motion of a test particle world line in order to define longitudinal and transverse accelerations as well. The intrinsic covariant derivative (induced connection) along such a world line is the appropriate mathematical tool to analyze this problem, and by modifying this operator to correspond to the observer measurements, one understands more clearly the work of Abramowicz et al. who derine an "optical centrifugal force" in static axisymmetric spacetimes and attempt to generalize it and other inertial forces to arbitrary spacetimes. In a companion article the application of this framework to some familiar stationary axisymmetric spacetimes helps give a more intuitive picture of their rotational features including spin precession effects, and puts related work of de Felice and others on circular orbits in black hole spacetimes into a more general context.
The Wheeler–Dewitt Equation for the Superstring World Sheet
Authors: Pollock M. D.
Published: October 2003

The Wheeler–DeWitt equation for the wave function ψ is obtained from the two-dimensional world-sheet action for the bosonic string and the superstring, including higher-derivative terms, as the Schrödinger equation i ∂ ψ/ ∂τ = V(τ)ψ. The potential is given by the rate at which the world-sheet area is swept out, V(τ) = dA(τ)/dτ, and is positive semi-definite, allowing the existence of a ground state, corresponding to the absence of the string, with a non-vanishing probability density ψ ψ*. Integration of this equation yields the solution [Formula: see text], where [Formula: see text] is the action, minus the higher-derivative terms [Formula: see text] (and terms involving ∊ab in the case of the superstring), which, however, are constrained to vanish semi-classically, being constructed from the square of the equation of motion for the bosonic coordinates XA derived from [Formula: see text] alone. This path-integral expression for ψ is consistent with the operator replacements for the canonical momenta used in its derivation, and forms the basis of the approach due to Polyakov of summing over random surfaces.

Comparison is made with the Schrödinger equations derived previously from the reduced, four-dimensional effective action for the heterotic superstring, and for the Schwarzschild black hole (by Tomimatsu), where the potential is also positive semi-definite, being (twice) the total mass of the Universe and the mass of the black hole, respectively, showing the unity of the method.
Nonclosure of Constraint Algebra in N = 1 Supergravity
Authors: Wulf Matthias
Published: October 2003

The algebra of constraints arising in the canonical quantization of N = 1 supergravity in four dimensions is investigated. Using the holomorphic action, the structure functions of the algebra are given and it is shown that the algebra does not close formally for two chosen operator orderings.
Isotropic Cosmological Model in Generalized Scalar Tensor Theory with Bulk Viscosity
Authors: Banerjee N. , Beesham Aroonkumar
Published: October 2003

In this paper both exponential and power law solutions for the flat Robertson–Walker cosmological model have been derived in a generalized Brans–Dicke theory, where the parameter ω is a function of the scalar field, along with a bulk viscous fluid. The solutions are obtained in Dicke's revised units and these are also given in the original atomic units via the conformal transformation prescribed by Dicke.
Cosmic Iron Whiskers: Their Origin, Length Distribution and Astrophysical Consequences
Authors: Narlikar J. V. , Wickramasinghe N. C. , Sachs R. , Hoyle F.
Published: October 2003

The idea that iron ejected from supernovae condenses in the form of slender whiskers in developed further. The formation mechanism and the resulting length distribution of the whiskers are related to several astrophysical and cosmological phenomena.
The Intrinsic Derivative and Centrifugal Forces in General Relativity: II. Applications to Circular Orbits in Some Familiar Stationary Axisymmetric Spacetimes
Authors: Bini Donato , Carini Paolo , Jantzen Robert T.
Published: October 2003

The tools developed in a preceding article for interpreting spacetime geometry in terms of all possible space-plus-time splitting approaches are applied to circular orbits in some familiar stationary axisymmetric spacetimes. This helps give a more intuitive picture of their rotational features including spin precession effects, and puts related work of Abramowicz, de Felice, and others on circular orbits in black hole spacetimes into a more general context.
Quantum Creation of a Black Hole
Authors: Wu Zhong Chao
Published: October 2003

Using the Hartle–Hawking no-boundary proposal for the wave function of the universe, we can study the wave function and probability of a single black hole created at the birth of the universe. The black hole originates from a generalized gravitational instanton with conical singularities. The wave function and probability of a universe with a black hole are calculated at the W K B level. The probability of a black hole creation is the exponential of one quarter of the sum of areas of the black hole and cosmological horizons. One quarter of this sum is the total entropy of universe. We show that these arguments apply to all kinds of black holes in the de Sitter space background.
Classical Signature Change in the Black Hole Topology
Authors: Hellaby Chariles , Sumeruk Ariel , Ellis G. F. R.
Published: October 2003

Investigations of classical signature change have generally envisaged applications to cosmological models, usually a Friedmann–Lemaître–Robertson–Walker model. The purpose has been to avoid the inevitable singularity of models with purely Lorentzian signature, replacing the neighbourhood of the big bang with an initial, singularity free region of Euclidean signature, and a signature change. We here show that signature change can also avoid the singularity of gravitational collapse. We investigate the process of re-birth of Schwarzschild type black holes, modelling it as a double signature change, joining two universes of Lorentzian signature through a Euclidean region which provides a "bounce". We show that this process is viable both with and without matter present, but realistic models — which have the signature change surfaces hidden inside the horizons — require nonzero density. In fact the most realistic models are those that start as a finite cloud of collapsing matter, surrounded by vacuum. We consider how geodesics may be matched across a signature change surface, and conclude that the particle "masses" must jump in value. This scenario may be relevant to Smolin's recent proposal that a form of natural selection operates on the level of universes, which favours the type of universe we live in.
Asymptotically Flat Spacetimes at Spatial Infinity: II. Gauge Invariance of the Integrals of Motion in the Field Approach
Authors: Petrov A. N.
Published: October 2003

In this paper we complete the work which was started in an earlier paper where asymptotically flat spacetimes at spatial infinity were examined in the framework in the field approach to general relativity (GR) in the Lagrangian description. In the field formulation of GR, the Hamiltonian description of a real isolated system for which all the physical fields are concentrated in a confined domain of space is developed. The integrals of motion are constructed and examined under the weakest fall-off conditions for gravitational potentials found earlier. It is shown that these integrals of motion are exactly the Arnowitt–Deser–Misner (ADM) integrals. The gauge invariance of the integrals of motion in both the Lagrangian and the Hamiltonian descriptions in studied from the point of view of the field approach to GR. It is found that the invariance of the ADM integrals of motion, which follows from the Stokes theorem, is explained as a gauge invariance of the linear field of the spin 2. The ambiguities in the ADM angular momentum can be explained as a violation of the weakest fall-off conditions for the gauge transformations found earlier.
Metric-Affine Gauge Theory of Gravity: I. Fundamental Structure and Field Equations
Authors: Gronwald Frank
Published: October 2003

We give a self-contained introduction into the metric–affine gauge theory of gravity. Starting from the equivalence of reference frames, the prototype of a gauge theory is presented and illustrated by the example of Yang–Mills theory. Along the same lines we perform a gauging of the affine group and establish the geometry of metric–affine gravity. The results are put into the dynamical framework of a classical field theory. We derive subcases of metric-affine gravity by restricting the affine group to some of its subgroups. The important subcase of general relativity as a gauge theory of tranlations is explained in detail.
Density Perturbations of Thermal Origin During Inflation
Authors: Lee Wolung , Fang Li-Zhi
Published: October 2003

We study thermally induced density perturbations during inflation. This scenario is characterized by two thermodynamical conditions: (1) The primordial perturbations originate in the epoch when the inflationary universe contains a thermalized heat bath. (2) The perturbations of the inflationary scalar field are given by the fluctuation–dissipation relation. We show that the spectrum of the primordial perturbations is of power law, but tilted, and there is a relation between the amplitude and the index of the power spectrum. Aside from the mass scale of the inflation, the amplitude–index relation does not depend on the other parameters like g-factor. These results are found to be well consistent with observations of the temperature fluctuations of cosmic microwave background if the mass scale of the inflation is about 1015  GeV . Instead of the purely adiabatic case, the consequent density perturbation is an admixture of adiabatic and isocurvature one. Therefore, the detection of super-Hubble suppression of the spectrum would be effective for further discrimination between the thermally originated models and others.
On the Perturbations of a Nonrotating Star Excited by a Massive Source I.: The Matching Conditions at the Surface of the Star
Authors: Ferrari V. , Gualtieri L.
Published: October 2003

In this paper we discuss the matching conditions to be imposed at the surface of a non-rotating star, when it is perturbed by a massive source, m0 ≪ M, either orbiting around the star or scattered by it. We shall determine the relations existing among the Regge–Wheeler and the Zerilli functions, which can be constructed by integrating the equations in the interior of the star, and the Bardeen–Press–Teukolsy and the Nakamura–Sasaki functions, which describe the perturbation outside the star, in the framework of the Newman–Penrose formalism. We shall also find the general form of the solution of the Nakamura–Sasaki equation appropriate to describe the problem on hand, by the Green's function method.
Possibility of Radio-wave Radiation Production Inside a Pulsar
Authors: Ahmedov B. J.
Published: October 2003

The influence of general-relativistic effects on charge distribution inside a neutron star is investigated. The qualitative distinction of space charge distribution inside the conducting crust from that inside the superconducting core allows us to propose a possible mechanism of radio-wave radiation produced in the intermediate medium inside a pulsar. The possibility of modeling this radiation in laboratory experiments in a rotating frame of reference is analysed.
Nature of Singularity in Einstein-Massless Scalar Theory
Authors: Virbhadra K. S. , Jhingan S. , Joshi P. S.
Published: October 2003

We study the static and spherically symmetric exact solution of the Einstein-massless scalar equations given by Janis, Newman and Winicour. We find that this solution satisfies the weak energy condition and has strong globally naked singularity.
Cosmology with the CMB
Authors: Smoot G. F.
Published: October 2003

The cosmic microwave background (CMB) radiation provides a means to test the standard model of cosmology and determine its parameters with precision. Cosmology has made a great step forward with the observations and discoveries of the COBE satellite. These were followed with a series of observations and progress via ballon-borne and ground-based instrumentation. Now NASA and ESA have selected and approved new space missions: MAP and COBRAS/SAMBA (now named Planck) which may nearly reach the full potential of CMB observations.
Cluster Analysis and Global Topology of CMB Anisotropy and Polarization
Authors: Arbuzov P. , Kotok E. , Naselsky P. , Novikov I.
Published: October 2003

In this paper we develop the theory of clustering of peaks in a Gaussian random field of the cosmic microwave background polarization. We have simulated 100 × 100 sky maps of anisotropy and polarization expected from a standard CDM cosmological model with 6' resolution. We have investigated the dependence of the mean length of clusters in anisotropy and polarization on the cross levels of the maps. We explore the role of non-Gaussian noise in the primordial signal and show that the methods of the cluster analysis and percolation are very useful for the detection of this noise in the maps of anisotropy and polarization.
Multipole Expansion Model in Gravitional Lensing
Authors: Fukuyama Takeshi , Kakigi Yuuko , Okamura Takashi
Published: October 2003

Nontransparent models of the multipole expansion model and the two point-mass model are analyzed from the catastrophe theory. Singularity behaviours of 2n-pole moments are discussed. We apply these models to the triple quasar PG1115+080 and compare with the typical transparent model, softened power law spheroids. The multipole expansion model gives the best fit among them.
Vacuum Stress-Energy Tensor of Nonconformal Scalar Field in Quasi-Euclidean Gravitational Background
Authors: Bordag M. , Lindig J. , Mostepanenko V. M. , Pavlov Yu. V.
Published: October 2003

The vacuum expectation value of the stress–energy tensor of a quantized scalar field with arbitrary curvature coupling in quasi-Euclidean background is calculated. The early time approximation for nonconformal fields is introduced. This approximation makes it possible to represent the matrix elements of the stress–energy tensor as explicit functionals of the scale factor. In the case of scale factors depending on time by the degree law the energy density is calculated explicitly. It is shown that the new contributions due to nonconformal curvature coupling significantly dominate the previously known conformal contributions.
Quantum Squeezing and Late Time Classical Behavior of Massive Fields in Expanding Robertson–Walker Universe
Authors: Mijić Milan
Published: October 2003

A Schroedinger picture analysis of time dependent quantum oscillators, in a manner of Guth and Pi, clearly identifies two physical mechanisms for possible decoherence of vacuum fluctuations in the early universe: turning of quantum oscillators upside-down, and rapid squeezing of upside-right oscillators so that certain squeezing factor diverges. In inflationary cosmology the former mechanism explains the stochastic evolution of light inflatons and the classical nature of density perturbations in most of the inflationary models, while the later one is responsible for the classical evolution of relatively heavy fields, with masses in a narrow range above the Hubble parameter: [Formula: see text]. The same method may be applied to the study of the decoherence of quantum fluctuations in any Robertson–Walker cosmology.
Statistics of Cosmic Microwave Background Radiation with the Cosmic String Model
Authors: Mähönen Petri , Hara Tetsuya , Voll Toivo , Miyoshi Shigeru
Published: October 2003

We have studied the cosmic microwave background radiation by simulating the cosmic string network induced anisotropies on the sky. The large-angular size simulations are based on the Kaiser–Stebbins effect calculated from full cosmic-string network simulation. The small-angular size simulations are done by Monte-Carlo simulation of perturbations from a time-discretized toy model. We use these results to find the normalization of μ, the string mass per unit length, and compare this result with one needed for large-scale structure formation. We show that the cosmic string scenario is in good agreement with COBE, SK94, and MSAM94 microwave background radiation experiments with reasonable string network parameters. The predicted rms-temperature fluctuations for SK94 and MSAM94 experiments are Δ T/T=1.57×10-5 and Δ T/T=1.62×10-5, respectively, when the string mass density parameter is chosen to be Gμ=1.4×10-6. The possibility of detecting non-Gaussian signals using the present day experiments is also discussed.
Black Holes with Short Hair
Authors: David Brown J. , Husain Viqar
Published: October 2003

We present spherically symmetric black hole solutions for Einstein gravity coupled to anisotropic matter. We show that these black holes have arbitrarily short hair, and argue for stability by showing that they can arise from dynamical collapse. We also show that a recent "no short hair" theorem does not apply to these solutions.
Charged Particle Trajectories in a Toroidal Magnetic and Rotation-Induced Electric Field Around a Black Hole
Authors: Sengupta Sujan
Published: October 2003

Trajectories of charged particles in a combined poloidal, toroidal magnetic field and a rotation-induced unipolar electric field superposed on a Schwarzschild background geometry have been investigated extensively in the context of accreting black holes. The main purpose of this paper is to obtain a reasonably good insight on the effect of spacetime curvature on the electromagnetic field surrounding black holes. The coupled equations of motion have been solved numerically and the results have been compared with that for flat spacetime. It is found that the toroidal magnetic field dominates the induced electric field in determining the motion of charged particles in curved spacetime. The combined electromagnetic field repels a charged particle from the vicinity of a compact massive object and deconfines the particle from its orbit. In the absence of a toroidal magnetic field the particle is trapped in a closed orbit. The major role of gravitation is to reduce the radius of gyration significantly while the electric field provides an additional force perpendicular to the circular orbit. Although the effect of inertial frame dragging and the effect of magnetospheric plasma have been neglected, the results provide a reasonably good qualitative picture of the important role played by gravitation in modifying the electromagnetic field near accreting black holes and hence the results have potentially important implications on the dynamics of the fluid and the radiation spectrum associated with accreting black holes.
Conserved Currents in Supersymmetric Quantum Cosmology?
Authors: Moniz P. V.
Published: October 2003

In this paper we investigate whether conserved currents can be sensibly defined in super-symmetric minisuperspaces. Our analysis deals with k = +1 FRW and Bianchi class-A models. Supermatter in the form of scalar supermultiplets is included in the former. Moreover, we restrict ourselves to the first-order differential equations derived from the Lorentz and supersymmetry constraints. The "square-root" structure of N = 1 super-gravity was our motivation to contemplate this interesting research. We show that conserved currents cannot be adequately established except for some very simple scenarios. Otherwise, equations of the type ∇a Ja = 0 may only be obtained from Wheeler–DeWittlike equations, which are derived from the supersymmetric algebra of constraints. Two appendices are included. In Appendix A we describe some interesting features of quantum FRW cosmologies with complex scalar fields when supersymmetry is present. In particular, we explain how the Hartle–Hawking state can now be satisfactorily identified. In Appendix B we initiate a discussion about the retrieval of classical properties from supersymmetric quantum cosmologies.
Comments on the Cosmological Constant Problem and How it Can be Solved
Authors: Wesson Paul S.
Published: October 2003

The problem of disparate estimates of the energy density of the vacuum can be solved, at least in principle, by reducing a higher-dimensional theory of gravity to general relativity and a local cosmological "constant."
Complex Inflaton Field in Quantum Cosmology
Authors: Kamenshchik A. Yu. , Khalatnikov I. M. , Toporensky A. V.
Published: October 2003

We investigate the cosmological model with the complex scalar self-interacting inflaton field non-minimally coupled to gravity. The different geometries of the Euclidean classically forbidden regions are represented. The instanton solutions of the corresponding Euclidean equations of motion are found by numerical calculations supplemented by the qualitative analysis of Lorentzian and Euclidean trajectories. The applications of these solutions to the no-boundary and tunneling proposals for the wave function of the Universe are studied. Possible interpretation of obtained results and their connection with inflationary cosmology is discussed. The restrictions on the possible values of the new quasifundamental constant of the theory — non-zero classical charge — are obtained. The equations of motion for the generalized cosmological model with complex scalar field are written down and investigated. The conditions of the existence of instanton solutions corresponding to permanent values of an absolute value of scalar field are obtained.
Simplest Cosmological Model with the Scalar Field
Authors: Kamenshchik A. Yu. , Khalatnikov I. M. , Toporensky A. V.
Published: October 2003

We investigate the simplest cosmological model with the massive real scalar non-interacting inflaton field minimally coupled to gravity. The classification of trajectories in closed minisuperspace Friedmann–Robertson–Walker model is presented. The possible fractal nature of a set of infinitely bounced trajectories is discussed. The results of numerical calculations are compared with those obtained by perturbative analytical calculations around the exactly solvable minisuperspace cosmological model with massless scalar field.
On Invariant Qualitative Chaos in Multi-Black-Hole Spacetimes
Authors: Szydłowski Marek
Published: October 2003

It is analytically shown when chaos exists in the behavior of null and timelike geodesics in the general case of geodesic motion in static and diagonal fields of general relativity. We demonstrate the effectiveness of our method of investigating chaos in the behavior of geodesic motion in the multi-black-hole spacetimes. An optical model of chaotic behavior of geodesics in spacetimes with cylindrical symmetry is presented. The Lyapunov characteristic time is defined and estimated for geodesic motion of a test particle in the external fields of general relativity. We find that its value is positive in some compact regions of the configuration space. This means that the trajectories have the property of local instability which implies the sensitive dependence on initial conditions.
Quadrupole and Hexadecapole Vibrational Excitations in Deformed Nuclei
Authors: Soloviev V. G. , Sushkov A. V. , Shirikova N. Yu.
Published: October 2003

Energies, wave functions of the quadrupole and hexadecapole states, B(Eλ) and B(M1) values are calculated within the quasiparticle-phonon nuclear model in a number of well-deformed even-even nuclei in the rare earth region. Reasonably good overall agreement with available experimental data is obtained. Specific properties of the Kπ = 0+ and two-gamma vibrational states are discussed. The distributions of the M1 strength is studied. It is shown that the M1 strength is more strongly fragmented in Er isotopes compared to Gd and Dy isotopes. The fragmentation of one- and two-phonon states is investigated. The fragmentation of one-phonon states strongly affects the Eλ and M1 strength distribution at energies above 2.5–3.0 MeV. The wave functions in the energy range 2–4 MeV contain specific nuclear structure information and these states cannot be treated as chaotic.
Quantum Entropy for Nuclei
Authors: Panos C. P. , Massen S. E.
Published: October 2003

The position- and momentum-space information entropies of nuclei are calculated in the framework of two models of the nucleus, i.e. the harmonic oscillator shell model and a correlated model which takes into account short range correlations. It is found that for every nucleus the sum of position and momentum entropies is independent of the oscillator parameter and increases slightly by introducing short range correlations. Finally it turns out that the same functional form S =aN + bN ln N for the entropy as function of the number of particles N (electrons or nucleons) holds approximately for atomic and nuclear systems.
Recent Progress in Quantum Hadrodynamics
Authors: Serot Brian D. , Walecka John Dirk
Published: October 2003

Quantum hadrodynamics (QHD) is a framework for describing the nuclear many-body problem as a relativistic system of baryons and mesons. Motivation is given for the utility of such an approach and for the importance of basing it on a local, Lorentz-invariant lagrangian density. Calculations of nuclear matter and finite nuclei in both renormalizable and nonrenormalizable, effective QHD models are discussed. Connections are made between the effective and renormalizable models, as well as between relativistic mean-field theory and more sophisticated treatments. Recent work in QHD involving nuclear structure, electroweak interactions in nuclei, relativistic transport theory, nuclear matter under extreme conditions, and the evaluation of loop diagrams is reviewed.
Using Fuzzy Set Theory to Analyse Investments and Select Portfolios of Tangible Investments in Uncertain Environments
Authors: Terceño Antonio , de Andrés Jorge , Barberà Glòria , Lorenzana Tomás
Published: October 2003

This paper shows how Fuzzy Set Theory can be used in investment analysis when, as usual, these investments are developed under uncertainty, i.e. the investor has only subjective estimates based on his experience or knowledge about the future cash-flows of the investments, the discount rate, etc. In particular, we will develop basic concepts for investment analysis as the Net Present Value and the Internal Rate of Return by assuming that the initial data are fuzzy numbers. Later we will analyse how to rank investments and how to select the tangible investment portfolios when the magnitudes are estimated subjectively by comparing fuzzy numbers and with possibilistic mathematical programming.
Imprecise Second-Order Hierarchical Uncertainty Model
Authors: Utkin Lev V.
Published: October 2003

A hierarchical uncertainty model for combining different evidence is studied in the paper. The model is general enough for many applications. The presented approach for dealing with the model allows us to combine the available heterogeneous information in the following ways: computing new probability bounds for some predefined interval of previsions, computing an "average" interval of first-order previsions, and updating the second-order probabilities after observing new events. Numerical examples illustrate this approach.
Representations of the Extensions of Many-Valued Equivalence Relations
Authors: Demirci Mustafa
Published: October 2003

Two fundamental questions on the extensions of many-valued equivalence relations, whose solutions have a crucial concern for the applications of many-valued equivalence relations, are explicitly stated to characterize the extensions of many-valued equivalence relations. Thereafter introducing the satisfactory solutions of these questions, the desirable characterizations of the extensions of many-valued equivalence relations are pointed out.
A Solution Method for Truncated Normalized Max Product Fuzzy Set of Equations
Authors: Brouwer Roelof K.
Published: October 2003

An iterative method of solving a set of equations based on the truncated normalized max product is described. The operation may serve as the transformation for the set of fully connected units in a fully recurrent network that might otherwise consist of linear threshold units. Because of truncation and normalization the network acting under this transformation has a finite number of states and components of the state vector are bounded. Component values however are not restricted to binary values as would be the case if the network consisted of linear threshold units but can now take on the values in the set {0, 0.1,..0.9, 1}. This means that each unit although still having discrete output can provide finer granularity compared to the case where a linear threshold unit is used. Truncation is natural in hardware implementation where only a finite number of places behind the decimal are retained.
Qualitative Probability and Order of Magnitude Reasoning
Authors: Parsons Simon
Published: October 2003

In recent years there has been a spate of papers describing systems for probabilistic reasoning which do not use numerical probabilities. In some cases these systems are unable to make any useful inferences because they deal with changes in probability at too high a level of abstraction. This paper discusses one of the problems this level of abstraction can cause, and shows how the use of a technique for order of magnitude reasoning can reduce its impact.
On the Fatigue-Life Distributions of Engineering Materials
Authors: Khaleel M. A. , Saunders S. C.
Published: October 2003

The applicability of the fatigue-life distribution of Birnbaum–Saunders for modeling the components of partially prestressed concrete girder bridges is argued by the agreement of the calculated distribution with a large data set comprised of many small censored samples, each put into standardized form, of the fatigue-lives of bridge components. Also, the Weibull and lognormal distributions are compared by the appropriateness of the assumptions in their derivation to the cumulative damage to bridge components.

The maximum likelihood estimates of the parameters of the fatigue lives of the prestressing steel, mild steel, and concrete are found from randomly censored samples, for several censored data-sets under various stress regimes. The parameters are postulated to be log-linear functions of the maximum stress and stress regimes. Weighted least-square regression is applied to determine the unknown coefficients. To compensate for differences in the precision of the estimates obtained under each stress regime the variances are calculated by the bootstrap statistical method. This procedure gives an estimated distribution of the fatigue life with its parameters functions of the stress regime which is applicable under virtually any realistic condition.
Some Reliability Models for Analyzing the Effect of Operating Conditions
Authors: Kumar Dhananjay , Westberg Ulf
Published: October 2003

Basic approaches of some of the reliability models available for analyzing the effect of operating conditions (or covariates) on the lifetime of a system are shortly discussed, and a general guideline for how to select an appropriate model for a given data set is provided. Some of the models have theoretical and computational difficulties which make them difficult to apply. Models that appear to be suitable for practical applications can broadly be classified as the class of proportional hazards models and the class of accelerated failure time models. In the class of proportional hazards models, e.g. the proportional hazards model and the proportional odds model, the effect of the covariates is assumed to act multiplicatively on the hazard rate or its transformations. In the class of accelerated failure time models, e.g. the parametric regression models, the effect of the covariates is assumed to act multiplicatively on the failure time or its transformations. Models from the proportional hazards family appear to be the better ones for analyzing the effect of the covariates due to the method used for estimating the parameters of these models.
Two-Stage Control Charts for High Yield Processes
Authors: Chan L. Y. , Xie M. , Goh T. N.
Published: October 2003

In this paper, a two-stage control chart for monitoring the defective rate of high-yield processes is proposed and studied. The Cumulative Count of Conforming control chart is generalized by using the number of items inspected until two defective items are observed. As this will increase the time to alarm, a two-stage approach combining both schemes is proposed. The occurrence of a defective within n1 items inspected in the first stage indicates that the process is out of control. If no defective occurs within n1 items inspected, the occurrence of two defectives within the next n2 - n1 in the second stage also indicates that the process is out of control. The probability of making a false alarm at the first and second stages are equal to α1 and α2, respectively. This procedure improves the sensitivity of the control chart in detecting shifting of the process defective rate p when p is at the parts-per-million order of magnitude.
Simplified Phased-Mission System Analysis for Systems with Independent Component Repairs
Authors: Somani Arun K.
Published: October 2003

Accurate analysis of the reliability of a system requires that all major variations in the system's operation are accounted for. Most reliability analyses assume that the system's configuration, success criteria, and components' behavior remain the same during an entire mission. However, system requirements and behavior vary over the time. Moreover, individual components may be repaired (if failed) such that repairs do not conflict with the operation of the system. Thus repairs are independent of the system state. Thus, multiple phases are natural. For repairable systems, Markov analysis techniques are used but they suffer from state space explosion. This limits the size of system that can be analyzed and it is expensive in computation. We present a new computationally efficient technique for the analysis of phased-mission systems where the operational states of a system can be described by combinations of component states (such as fault trees or assertions). We avoid the state space explosion. The phase algebra is used to account for the effects of variable configurations, repairs, and success criteria from phase to phase. Our technique yields exact (as opposed to approximate) results. We demonstrate our technique by means of several examples and present numerical results to show the effects of phases and repairs on the system reliability/availability.
Thresholds for Safety Inspection Measurements Based on Control Charts
Authors: Cheng Andrew Y. , Liu Regina Y. , Luxhøj James T.
Published: October 2003

The rapid growth of air traffic density has long demanded the Federal Aviation Administration (FAA) to design an effective safety inspection system. Well defined thresholds are essential to such an inspection system since they provide standards for both monitoring and regulating purposes. In this paper, we use control chart techniques to derive thresholds and standards for inspection measures, and to provide charts for monitoring them continuously. These thresholds charts play the same role as control charts do in statistical quality control for the monitoring of manufacturing processes. In quality control, the centerline of the chart indicates the target value and the control limits determine whether the process is out of control. In safety inspections, we view the centerline as the safety standard, and justify some properly chosen levels of control limits as meaningful thresholds. For FAA safety inspection surveillance results concerning air carriers, these thresholds are termed alert, advisory, expected, and informational. They provide a concrete measure of the inspection results in terms of the severity of potential flaws, and serve as a guideline for the general rating of the safety performance of each carrier. Furthermore, we can now use the so-called average run length to measure the effectiveness of the inspection system with the proposed thresholds. This approach is implemented on a dataset of an operational performance measure collected from ten air carriers over a period of 6 months. The results are very supportive.
An NHPP Software Reliability Model and Its Comparison
Authors: Pham Hoang , Zhang Xuemei
Published: October 2003

In this paper, software reliability models based on a nonhomogeneous Poisson process (NHPP) are summarized. A new model based on NHPP is presented. All models are applied to two widely used data sets. It can be shown that for the failure data used here, the new model fits and predicts much better than the existing models. A software program is written, using Excel & Visual Basic, which can be used to facilitate the task of obtaining the estimators of model parameters.
Bayesian Reliability Analysis of High-Reliability Systems of Binomial and Poisson Subsystems
Authors: Martz Harry F. , Baggerly Keith A.
Published: October 2003

A Bayesian procedure for estimating the reliability of a complex system of independent series and parallel subsystems is presented. This method accepts either binomial or Poisson test data (perhaps both or neither) as inputs, as well as prior information, at any and all levels in the system (such as the component, subsystem and system levels). Natural conjugate beta and gamma priors are considered. A numerical example concerning the unreliability of the low-pressure coolant injection system of a certain U.S. commercial nuclear-powered boiling water reactor is used to illustrate the procedure. A Mathematica® notebook is available for implementing the method.
Determining the Optimum Cost for Systems with Component-Level Redundancy
Authors: Engelhardt Max
Published: October 2003

The problem of designing systems which are composed of several redundant subsystems in series is considered. A method for determining the number of components in each subsystem which will minimize the total cost of components while maintaining a prescribed level of system reliability is derived. One advantage of the approach used here is that it is not necessary to employ an elaborate search algorithm to obtain the optimum solution.
Optimal Replacement Policy for a Cumulative Damage Model with Deteriorated Inspection
Authors: Satow Takashi , Nakagawa Toshio
Published: October 2003

This paper proposes a replacement policy for a cumulative damage model where a unit suffers damage caused by both shocks and inspections, and fails when the total damage has exceeded a failure level. To detect such failure, a unit is inspected at periodic times kT(k = 1, 2, …), and is replaced by a new one at detection of failure or at time nT, whichever occurs first. The expected cost rate is derived, when shocks occur at a non-homogeneous Poisson process, and an optimal number n* which minimizes it is discussed. Numerical examples are finally given.
Infrared Absorptive and Dispersive Optical Bistabilities of Semiconductor Superlattice Etalons
Authors: Zhao Guo-Zhong , Pan Shao-Hua
Published: October 2003

We have derived Maxwell-Bloch equations of a two-subband model suitable for studying intersubband-transition induced optical-nonlinearities of semiconductor superlattices (SLs). Analytical expressions and numerical illustrations for absorptive and dispersive optical bistabilities (OBs) of SL etalons are given. Both OBs can be realized in infrared region with high frequency selectivity, and their bistable domains and hysteresis loops are much larger than those of a two-level system. The dispersive OB is preferable due to its lower value of the input power.
Characterisation of Liquid Brillouin Media at 532 nm
Authors: Jones D. C.
Published: October 2003

A number of transparent liquids have been evaluated for use in stimulated Brillouin scattering at 532 nm. Measurements were made of frequency shift, SBS threshold, reflectivity and optical breakdown properties. It was found that the alkanes, and in particular n-pentane, performed well and measurements were made of Brillouin gain coefficient and phonon lifetimes. It is suggested that these liquids are promising candidates for use in self-pumped phase conjugate mirrors, high gain Brillouin amplifiers and four-wave mixing mirrors.
Subharmonic Generation by Phase Modulated Light Beams and AC Field
Authors: Miklyaev Yu. V. , Safonov V. I.
Published: October 2003

Generation of spatial subharmonic gratings in photorefractive crystal under an external AC field and a phase modulated interference pattern is investigated. This method of grating formation can lower the threshold contrast mth for the subharmonic generation.
Excited-State Enhancement of Optical Nonlinearities of Dialkynyl Complexes
Authors: Zhao Jiang , Wang Yougui , Si Jinhai , Ye Peixian , Li Shijie , Zhang Linjun , Wu Zhefu , Yang Mujie
Published: October 2003

Optical nonlinearities of dialkynyl complexes at ground state and excited states have been investigated by DFWM. The nonlinear susceptibilities of the system were enhanced greatly through the population of the excited states. The values of the hyperpolarizabilities of the sample molecule at excited states, γ1111,se and γ1221,se, were determined to be 2.15 × 10-30 esu and 1.17 × 10-30 esu, respectively, while their values at ground state, γ1111,sg and γ1221,sg, were 1.08 × 10-31 esu and 2.30 × 10-32 esu.
Linear and Nonlinear Optical Responses in Double Quantum Wells with Field Induced Quantum Coherence and Interference
Authors: Huang Danhong , Zhao Yang , Awad Eddie
Published: October 2003

New results of quantum coherence and interference effects in linear and nonlinear optical responses in double quantum wells are presented. Three-subband model in which two upper tunneling-split subbands are coupled by a dc-field is studied. We show the importance of the dc-field in establishing the quantum coherence and interference which introduces into the lasing without inversion and enhances the optical nonlinearity in the system. The optimal threshold dc-field can achieve as low as 4 kV/cm in our model. The Coulomb renormalization of electron kinetic energy is included. The many-body theory is employed to calculate both the linear and nonlinear optical responses.
A Study of the Nonlinear Optical Transmittance in a Variety of TCNQ-Based Organometallic Colloidal Suspensions
Authors: Schuster P. R. , Viands C. A. , Potember R. S. , Schmitt M. G.
Published: October 2003

Optical limiting in a series of novel aqueous colloidal suspensions is investigated. The suspensions consist of an organometallic charge-transfer complex based on the organic acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ). We report on the synthesis of the organometallic complexes and their effectiveness at limiting nanosecond pulses at 532 nm. It is shown that some of the charge-transfer systems can effectively attenuate pulses at rates up to 10 Hz while other systems require continuous agitation in order to most efficiently limit the laser radiation. Finally we discuss the reversible field-induced phase transition that produces the observed nonlinear absorption.
Pulse-Shape Dependent Time Averaging Effects in Interferometric Nonlinear Phase Shift Measurements
Authors: Kim Dug Y. , Stegeman George I.
Published: October 2003

When optical pulses of temporal width less than or comparable to a detector's response time are used to interferometrically measure intensity-dependent phase shifts, it becomes necessary to use time-averaging protocols to deduce the material nonlinearity. Relations between the actual peak nonlinear phase shifts and the measured values are numerically evaluated for Gaussian and sech square pulse shapes. We believe that these results are also very important to understand the pulse break-up effect in Mach-Zehnder type all-optical switching applications.