bluuebunny/crossref_metadata_2025 huggingface dataset:
SYNAPTIC ACTIVITY IN A KINETIC THEORY OF NEURAL SYSTEMS
Authors: VENTRIGLIA F. , RADDI A.
Published: November 2004

In this article we attempt to extend a kinetic model of neural systems presented earlier, with the introduction of elements related to the dynamics of neurotransmitters. We emphasize the importance of neurotransmitters inducing slow inhibitory postsynaptic potentials (IPSPs) to smoothen the neural system activity obtained in computer simulations. Some kinetic equations are formulated to describe the activity of complex neural systems constituted of several possible subfields. The results of some computational experiments performed with a model of simple feed-forward neural system are described.
NEURAL NETWORK SIMULATIONS OF DISTRIBUTED VERSUS INTERVAL DISPARITY CELL CODINGS
Authors: O’TOOLE A.J. , NGUYEN T.H.T.
Published: November 2004

The purpose of the present paper was to implement two computational models of structure-from-stereopsis comparing the computational utility of interval and distributed codings of image disparity. Interval codings represent disparity in discrete ranges, whereas distributed codings represent disparity using overlapping tuning curves similar to the response profiles of neurons found in the visual cortex of primates. We relate this also to recent neurophysiological work indicating that binocular neurons may be tuned to the relative phase of luminance input to the left and right eyes. A distributed coding of disparity has been shown previously to provide a good model for human stereoacuity. In this paper we show that it is also advantageous for solving the structure-from-stereopsis problem. Separate sets of neural network simulations were undertaken to learn a mapping function from (1) interval and (2) distributed disparity codings to a three-dimensional surface representation. Example pairs of disparity codings and surface representations were used to adjust the weights on a radial basis function network to learn the mapping function for the example surfaces. The generalizability of the learned mapping function was tested with novel surfaces. While the networks performed equally well (perfectly) on the learned surfaces, the distributed disparity coding networks generalized better to novel surfaces than did the interval code.
TOWARDS A DYNAMIC MODEL OF ASSOCIATIVE SEMANTIC MEMORY
Authors: RODET L. , TIBERGHIEN G.
Published: November 2004

When we analyze a particular stimulus, a number of neurons in the brain are specifically activated. The recognition of a visual pattern can be interpreted as the activation of a particular group of such neurons, in a particular way. Some recent results [5] have shown that a group of neurons may respond to a stimulus with a coupled activity. This notion of coupled neural activity can be used to understand the multiple levels of parallelism in the brain. It is known that, in response to a single stimulus, many mental representations are activated in parallel [1]. Our objective is to examine how coupled activity of groups of neurons can explain this parallelism of concept activation in the brain. The neural activity of a single neuron or groups of neurons is simulated. Simple neural networks combining groups of neurons could also be used to simulate the synchronization of neural activities.
DATA AND KNOWLEDGE VISUALIZATION IN AN ENVIRONMENTAL INFORMATION SYSTEM
Authors: LAM DAVID C.L. , WONG ISAAC , SWAYNE DAVID A. , FONG PHILIP
Published: November 2004

An environmental information system is an important tool in conducting ecosystem research that integrates data and knowledge from many disciplinary studies. Effective computer visualization of these data and knowledge leads to better communication and understanding of the individual results and the concept of the ecosystem approach. By using examples from an environmental information system prototype, the advantages and issues surrounding the development and application of visualization methodologies will be discussed. It was found that while data visualization techniques have advanced significantly, the knowledge representation and visualization procedures have not been fully developed. Further work in this area was recommended particularly in view of the demand for better knowledge exchange mechanisms among scientists with different disciplines.
SELF-SIMILAR COLONY MORPHOGENESIS BY BACTERIA AS THE EXPERIMENTAL MODEL OF FRACTAL GROWTH BY A CELL POPULATION
Authors: MATSUYAMA TOHEY , HARSHEY RASIKA M. , MATSUSHITA MITSUGU
Published: November 2004

Bacteria point inoculated onto the solid medium exert two-dimensional spreading growth on the surface. The colony morphologies are rich in diversity and depend on various biological and physico-chemical factors. Since it is easy to pursue the growth processes macro- and microscopically and to carry out experiments by controlling specific factors, precise experimental approaches to morphogenesis by living cells have now become possible. Several critical factors for self-similar morphogenesis were identified.
FRACTAL DESCRIPTION OF ANOMALOUS DIFFUSION IN DYNAMICAL SYSTEMS
Authors: KLAFTER J. , ZUMOFEN G. , SHLESINGER M.F.
Published: November 2004

Anomalous diffusion properties are common in a broad spectrum of systems including dynamical systems. In this paper we review an approach based on Lévy scale-invariant distributions to describe transport in dynamical systems. We introduce the basic ingredients that make the approach useful in describing anomalous diffusion and demonstrate the applicability in the cases of one-dimensional iterated maps and of the standard map.
PATTERN FORMATION OF ELECTROLESS DEPOSITION AND COLLOID AGGREGATION OF GOLD IN HIGH MAGNETIC FIELDS
Authors: MOGI IWAO , OKUBO SUSUMU , KIDO GIYUU , NAKAGAWA YASUAKI
Published: November 2004

Pattern formation of two kinds of aggregation was investigated in high magnetic field of 8 T (tesla) as an experimental approach to the irreversible aggregation with particle drifts. A drastic change was observed in the growth pattern of the gold metal-forest (electroless deposit of gold around a lead ribbon), including a randomly ramified structure at 0 T and oblique growth with a smooth interface at 8 T. On the other hand, no remarkable effect of the magnetic field was observed in the branching pattern of the gold colloid solution.
A CASCADE MODEL OF WAVE TURBULENCE WITH APPLICATIONS TO SURFACE GRAVITY AND CAPILLARY WAVES
Authors: GLAZMAN ROMAN E.
Published: November 2004

A heuristic approach to the derivation of power spectra of wave motion is described and applied to capillary waves. The case of gravity waves studied earlier is briefly reviewed. In contrast to the previous studies, the nonlinearity of the wave motion is not required to be small, and the mean number of resonantly interacting wave harmonics is not limited to a smallest possible number (which is 4 for gravity waves on a deep fluid and 3 for capillary waves). The main external parameter of the problem is the input flux Q of the wave energy related to the mean wind velocity as QαU3. Depending on its value, wave spectra S(ω)αω−qand F(k) α k−p take various forms—from that corresponding to the weak-turbulence limit and to that corresponding to the saturated (Phillips’) wave spectra. Fractal dimensions of the sea surface are related to external factors, specifically to the mean wind speed. The theoretically predicted spectra are in qualitative agreement with the observations on capillary waves conducted in a large wave tank.
STRUCTURES GENERATED BY MODEL NONLINEAR HAMILTONIANS BASED ON OCEAN WAVES
Authors: WILLEMSEN JORGE F.
Published: November 2004

When surface gravity waves in deep water are driven to a balance between energy input and dissipation, it has been observed that the spectrum of wave-height correlations exhibits power-law behavior consistent with the interpretation that over a range of length scales the surface is a self-affine fractal. Zakharov and L’vov long ago invoked a Kolmogorov cascade hypothesis to describe the nonlinear modal transfer of energy which might explain this observation, even in the absence of driving and dissipation. If their hypothesis is correct, a purely autonomous Hamiltonian system would be capable of driving a surface to fractal roughness, in analogy to dynamical system chaos. In this report I summarize a body of recent work aimed at testing the Z-L hypothesis through numerical integration of Zakharov’s Hamiltonian equations. I investigate both scaling and the existence of postulated emergent dynamical times which scale with modenumber. The results are mixed, in ways not easily abstracted. They lead to hard questions regarding the roles of driving and dissipation, and the process of equilibration of the waveheight statistical distribution, which cannot be answered at our present state of knowledge. But I hope that the form of the questions will prove stimulating.
BI-MULTIFRACTAL ANALYSIS AND MULTI-AFFINE MODELING OF NON-STATIONARY GEOPHYSICAL PROCESSES, APPLICATION TO TURBULENCE AND CLOUDS
Authors: DAVIS A.B. , MARSHAK A.L. , WISCOMBE W.J.
Published: November 2004

In recent years, considerable progress has been achieved in the description of natural variability, largely due to the widespread use of scale-invariant concepts such as fractals and multifractals. In particular, this last concept has been used to clarify the fuzzy notion of “inhomogeneity” by introducing and quantifying the effects of intermittency. In this paper, we present a more comprehensive approach to multifractal data analysis and simulation that includes and combines the currently popular singularity analysis techniques with the more traditional approach based on structure functions. Being related to the new idea of “multi-affinity”, these last statistics are regaining favor and constitute the proper framework to address the problem of quantifying and qualifying yet another outstanding fuzzy notion, that of “non-stationarity”. This is an important step because non-stationary behavior is ubiquitous in Nature.

Using turbulence as an example, we also show how a unified multifractal formalism can help in extracting, from data alone, the “effective constitutive laws” that describe phenomenologically the nonlinearities of the macroscopic transport processes that shape the geophysical field represented by the dataset. Finally, we argue that the essential multifractality of any natural system can be captured on the “q=1 multifractal plane” and describe ways in which it can be used in practical geophysical problems.
ESTIMATION OF UNIVERSAL FOR ATMOSPHERIC TURBULENT MULTIFRACTAL INDICES VELOCITY FIELDS
Authors: SCHMITT F. , SCHERTZER D. , LOVEJOY S. , BRUNET Y.
Published: November 2004

We study wind turbulence with the help of universal multifractals, using atmospheric high resolution time series. We empirically determine the three universal indices (H, C1, and α) which are sufficient to characterize the statistics of turbulence. The first, H, which characterizes the conservation of the field, is theoretically and empirically known to be ≈1/3, while C1 corresponds to the inhomogeneity of the mean field (C1=0 for homogeneous fields, and C1>0 for inhomogeneous and intermittent fields). The most important index is the Lévy index α corresponding to the degree of multifractality (0≤α≤2, α=0 for a monofractal). The two latter indices are directly obtained by applying the double trace moment technique (DTM) on the turbulent field. Analyzing various atmospheric velocity measurements we obtain: α≈1.45±0.1 and C1≈0.25±0.1. These results show that atmospheric turbulence has nearly the same multifractal behavior everywhere in the boundary layer, corresponding to unconditionally hard multifractal (α≥1) processes. This describes the entire hierarchy of singularities of the Navier-Stokes equations.
A MINIMUM ENERGY DISSIPATION MODEL FOR RIVER NETWORKS AND THEIR ASSOCIATED TOPOGRAPHIES
Authors: SUN T. , MEAKIN P. , JØSSANG T.
Published: November 2004

The model for the river networks presented here is based on minimum energy dissipation principles. The foundation for this model is the empirical relationship s~Qα between the link slope s in channel networks and the mean annual discharge Q in that link. The associated landscapes were constructed using a range of values for the exponent α. The surfaces appear to be more complex than simple self-affine fractals. The boundaries of drainage basins covering the entire drainage area were found to have an effective fractal dimension about 1.10 for all values of α in the range −1<α<0. A universal power-law size (area) distribution is also found for the drainage basins obtained from this minimum energy dissipation model.
NUMERICAL DETERMINATION OF FRACTAL AND ENTROPY CHARACTERISTICS OF THE SEISMIC PROCESS ON THE TERRITORY OF ARMENIA
Authors: SHAHVERDIAN A.Yu. , AKOPOV N.Z.
Published: November 2004

An application of certain methods of the theory of dynamical chaos to researching of the seismic process is considered. By means of computer-assisted processing of the earthquakes catalogue the numerical values of the fractal, information and correlation dimensions for this process on the territory of Armenia are determined. Using the numerical method, the inequality K>0 for the Kolmogorov-Sinay entropy K for seismic process is examined.
MULTI-SINGULAR AND MULTI-AFFINE PROPERTIES OF BOUNDED CASCADE MODELS
Authors: MARSHAK A. , DAVIS A. , CAHALAN R. , WISCOMBE W.
Published: November 2004

We investigate a class of one-dimensional bounded random cascade models which are multiplicative and stationary by construction but additive and non-stationary with respect to some, but not all, of their statistical properties. In essence, a new parameter H>0 is introduced to “smooth” standard (p-model) cascades, these well-studied processes being retrieved at H=0. The resulting ambivalent statistical behavior of the new model leads to a 1st order multifractal phase transition in the structure function exponents, i.e., there is a discontinuity in the derivative of ζq= min{qH, 1}. We interpret this bifurcation as a separation of the stationary and non-stationary “ingredients” of the model by lowering the multifractal “temperature” (1/q) below the critical value H. We also see exactly how the generalized dimensions Dq converge to one in the small scale limit for all q. We discuss this last finding in terms of “residual” multifractality, a singularity spectrum that is entirely traceable to finite size effects (to which we are never immune in data analysis situations). Finally, we locate the bounded and unbounded versions of the model in the “q=1 multifractal plane” where the coordinates are C1=1−D1 (a direct measure of “intermittency”) and H1=ζ1 (a direct measure of “smoothness”), both of which are normally in the interval [0, 1]. This provides us with a simple way of comparing the multiplicative models with their additive counterparts, as well as with different types of geophysical data.
PLURIFRACTAL SIGNATURE IN THE STUDY OF RESONANCES OF DYNAMICAL SYSTEMS
Authors: PLANAT M. , KOCH P.
Published: November 2004

This paper deals with the numerical investigation of the resonant zones of dynamical equations. Starting from the continuous differential model, the section of trajectories is obtained using resonant principles. Several techniques have been developed for measuring the stability of windings: the Liouville exponent γ of the Kolmogorov-Arnold-Moser theory; the Lipschitz-Hölder exponent α introduced by Mandelbrot; and a frequency locking exponent β that is related to Fourier spectra. These techniques are implemented on typical models and some original results concerning the fractal structure of resonant regions are emphasized.
LARGE SCALE STRUCTURE OF INTERFACES: AN INVERSE METHOD
Authors: LAM CHI-HANG , SANDER LEONARD M.
Published: November 2004

We propose an inverse method to extract effective couplings and the renormalization group flow for growing interfaces. We apply it to discrete surface growth models in the Kardar-Parisi-Zhang universality class in 1+1 dimensions and obtain the first measurement of a universal coupling constant. We consider interfaces not in the steady state. It may also be applicable to analyze experimental data and for other forms of interface growth.
THE MORPHOLOGY AND EVOLUTION OF THE SURFACE IN EPITAXIAL AND THIN FILM GROWTH: A CONTINUUM MODEL WITH SURFACE DIFFUSION
Authors: FAMILY FEREYDOON , AMAR JACQUES G.
Published: November 2004

A number of discrete models as well as continuum equations have been proposed for describing epitaxial and thin film growth. We have shown that there exists a macroscopic groove instability in many of these models. This unphysical feature in the continuum equations arises from the truncation or linearization of the diffusion operator along the surface. A similar artifact occurs in the discrete models, because in these models adatoms only diffuse horizontally and must take an unphysical vertical jump at step edges. We have proposed and studied a continuum equation for epitaxial and thin-film growth in which the full diffusion along the surface is taken into account. The results of the solutions of this continuum equation, for the growth and the morphology of the surface, are in excellent agreement with recent low temperature molecular-beam epitaxy and ion-sputtering experiments. In particular, we find that at late times dynamic scaling breaks down and the surface is no longer a self-affine fractal. The surface develops a characteristic morphology whose dependence on deposition rate and surface diffusion is similar to that found in experiments.
GRANULAR COCKTAIL ROTATED AND SHAKEN
Authors: BAUMANN G. , JOBS E. , WOLF D.E.
Published: November 2004

In order to study scaling phenomena in granular materials, simple extensions of a model originally proposed by Jullien, Meakin and Pavlovitch (Phys. Rev. Lett. 69, 640 (1992)) are developed. It is shown that the model reproduces phenomena like the heap formation due to friction at the container walls during vertical shaking, as well as size segregation in a rotating drum. The geometrical mechanisms underlying these phenomena are discussed, as well as preliminary results about the critical behavior.
SURFACTANT-MEDIATED SURFACE GROWTH: NONEQUILIBRIUM THEORY
Authors: BARABÁSI ALBERT-LÁSZLÓ
Published: November 2004

A number of recent experiments have shown that surfactants can modify the growth mode of an epitaxial film, suppressing islanding and promoting layer-by-layer growth. Here a set of coupled equations are introduced to describe the coupling between a growing interface and a thin surfactant layer deposited on the top of the non-equilibrium surface. The equations are derived using the main experimentally backed characteristics of the system and basic symmetry principles. The system is studied using a dynamic-renormalization-group scheme, which provides scaling relations between the roughness exponents. It is found that the surfactant may drive the system into a novel phase, in which the surface roughness is negative, corresponding to a flat surface.
ON ANOMALOUS DIFFUSION OF GROWING CLUSTERS
Authors: GADOMSKI ADAM , LUCZKA JERZY
Published: November 2004

A continuous random walk of a growing cluster of dimension df is studied. It is assumed that its behavior is represented by a standard diffusion equation. A diffusion coefficient is assumed to be a cluster mass dependent power function which in the dilute solution regime takes a form first suggested by Kirkwood. The mass of the cluster increases in time according to another power law. It results in anomalous diffusion of the cluster in a three dimensional space which, in a linear case, is manifested by either power or logarithmic law of the mean square displacement. Some interesting examples and realizations of that process in polymer science, colloid physicochemistry or materials science are pointed out.
ANTIFERROMAGNETIC FRACTON AND ITS SPECTRAL DIMENSION
Authors: YAKUBO KOUSUKE , TERAO TAKAMICHI , NAKAYAMA TSUNEYOSHI
Published: November 2004

The spectral dimensions of spin-wave fractons in percolating antiferromagnets are investigated in terms of a dynamic scaling argument and numerical simulations. It is found, by the scaling argument, that the value of the spectral dimension [Formula: see text] of antiferromagnetic fractons should be less than unity for any Euclidean dimensions d(≥2). Simulated results of [Formula: see text] for d=2, 3 and 4 percolating antiferromagnets indicate that [Formula: see text] are very close to unity independent of Euclidean dimension d.
NONLINEAR STOCHASTIC DIFFERENTIAL EQUATIONS AND SELF-ORGANIZED CRITICALITY
Authors: DIAZ-GUILERA ALBERT
Published: November 2004

Several nonlinear stochastic differential equations have been proposed in connection with self-organized critical phenomena. Due to the threshold condition involved in its dynamic evolution, an infinite number of nonlinearities arise in a hydrodynamic description. We study two models with different noise correlations which make all nonlinear contributions to be equally relevant below the upper critical dimension. The asymptotic values of the critical exponents are estimated from a systematic expansion in the number of coupling constants by means of the dynamic renormalization group.
SCALE-INVARIANT DYNAMICS AND UNIVERSALITY CLASSES IN LAPLACIAN FRACTAL GROWTH
Authors: VESPIGNANI A. , PIETRONERO L.
Published: November 2004

We consider the problem of the universality and general structure of the scale invariant dynamics in Laplacian fractal growth models. In particular, we show that growth having sticking probability not equal to one is renormalized asymptotically into effective growth rules with unit sticking probability (standard growth rule). This result shows why this modified model belongs to the same universality class as the standard DLA, and contributes to clarifying the asymptotic form of the scale invariant growth rule. These conclusions about the universality classes can also be extended to reaction-limited cluster-cluster aggregation.
SOC IN A CLASS OF SANDPILE MODELS WITH STOCHASTIC DYNAMICS
Authors: LÜBECK S. , USADEL K.D.
Published: November 2004

We have studied one-dimensional cellular automata with updating rules depending stochastically on the difference of the heights of neighboring cells. The probability for toppling depends on a parameter λ which goes to one with increasing slope, i.e., the dynamics can be varied continuously. We have investigated the scaling properties of the model using finite-size scaling analysis. A robust power-law behavior is observed for the probability density of the size of avalanches in a certain range of λ values. The two exponents which determine the dependence of the probability density on time and system size both depend continuously on λ, i.e., the model exhibits nonuniversal behavior. We also measured the roughness of the surface of the sandpile and here we obtained a universal behavior, i.e., a roughness exponent of about 1.75 for all values of λ. For the temporal behavior of the mass, a f−Φ spectrum is obtained with an exponent Φ close to 2, again for all λ-values.
SPATIAL MULTIFRACTALITY OF ELECTRONIC STATES AND THE METAL-INSULATOR TRANSITION IN DISORDERED SYSTEMS
Authors: SCHREIBER MICHAEL , GRUSSBACH HEIKO
Published: November 2004

For the investigation of the spatial behavior of electronic wave functions in disordered systems, we employ the Anderson model of localization. The eigenstates of the corresponding Hamiltonian are calculated numerically by means of the Lanczos algorithm and are analyzed with respect to their spatial multifractal properties. We find that the wave functions show spatial multifractality for all parameter cases not too far away from the metal-insulator transition (MIT) which separates localized from extended states in this model. Exactly at the MIT, multifractality is expected to exist on all length scales larger than the lattice spacing. It is found that the corresponding singularity spectrum describing these multifractals is specific for the MIT and does not depend on microscopic parameters like energy or disorder, nor does it depend on the probability distribution used for the random site energies in the Anderson Hamiltonian. Therefore this calculated singularity spectrum which is characteristic for the transition can be used to identify the MIT in systems where the position of the MIT is not known a priori. We apply this idea to states near the band edge and show that the results are in agreement with other methods.
STOCHASTIC RESONANCE AT THE ONSET OF FINITE- AMPLITUDE OSCILLATIONS IN SEMICONDUCTOR BREAKDOWN
Authors: RICHTER R. , KITTEL A. , PYRAGAS K. , PARISI J.
Published: November 2004

The phenomenon of stochastic resonance has been observed when looking at low-temperature impact ionization breakdown in p-type germanium crystals. Originally, such an effect was predicted for the class of bistable nonlinear dynamical systems which are subject to a periodic modulation as well as to random perturbation. We demonstrate first experimental evidence that stochastic resonance can also be detected in a monostable system, i.e., immediately below the onset of finite-amplitude oscillations during semiconductor breakdown.
TRACER TIME DISTRIBUTION OF PARTICLES IN POROUS MEDIA
Authors: ARAUJO MARIELA
Published: November 2004

We study the transit time distributions of tracer particles in a porous medium through which a constant flow rate is established. Our model assumes that non-Gaussian dispersion is due to the presence of low velocity zones or channels in parallel with a faster flow path. Each channel is represented as a trap and simulates the existence of variable permeability blocks inside the porous medium. The time the tracer particle spends inside each channel is related to the heterogeneity of the sample, and is assumed here to have a power-law distribution. We compare the transit time distribution of these particles for the case in which the traps are Poisson distributed with the one in which the trap distribution is a power-law function.
TURBULENT FLOW IN VIBRATED BED OF POWDER: NEW TARGET TO INVESTIGATE TURBULENT FLOW
Authors: TAGUCHI Y.-H.
Published: November 2004

The flow patterns in the vibrated bed of powder are investigated numerically in two dimensions. They turn out to exhibit turbulent flow like that observed in fully developed turbulence. The power spectrum of their flow lines has k−5/3 power, where k is the wave number. Since the numerical investigation of powder requires very few computational resources, it provides us with a new tool to study turbulence easily.
A MODEL FOR SCATTERING FROM AN ACOUSTICALLY HARD SURFACE WITH NONDIFFERENTIABLE PERIODIC ROUGHNESS
Authors: BISHOP GARNER C. , SMITH JUDY
Published: November 2004

A model is described and numerical results are shown for the far-field scatter of a plane wave from an acoustically hard surface with a periodic roughness profile function that is continuous everywhere, but is nondifferentiable at a finite number of points within a period, and that may have a large maximum amplitude or slope. Scattering from these types of surfaces is modeled by approximating the roughness profile by truncating its Fourier series representation, and using the integral equation scattering formalism of Holford [J. Acoust. Soc. Am.70, (1981) 1116–1128]. To determine the effects of this approximation on the far-field scatter, the exact profile function and the scattering formalism of DeSanto [Radio Sci.16, (1981) 1315–1326], which is not an integral equation formalism, is also used to calculate the far-field scatter. Both formalisms are used to calculate plane wave scattering from sinusoidal surface roughness and from nondifferentiable periodic surface roughness constructed from (1) a trapezoid, (2) a rectified sinusoid, (3) concave upward and concave downward semi-ellipses, and (4) a power law spectrum. It is shown that the amplitudes of the plane wave modes scattered from a continuous and nondifferentiable surface and from its truncated Fourier series representation are essentially identical for all surfaces considered and over a wide range of incident grazing angles, wavenumbers, and surface roughness. In addition, it is shown that the Holford formalism may be used to calculate scattering from surfaces considerably rougher and at grazing angles lower than the DeSanto formalism, but that the Holford formalism is more computationally intensive than the DeSanto formalism, and that in the regions where both theories are numerically stable, the DeSanto formalism is preferable.
RADIATION BOUNDARY CONDITIONS FOR VERTICALLY HETEROGENEOUS ACOUSTIC MEDIA
Authors: LI GONGQIN , MURPHY JOSEPH E. , CHIN-BING STANLEY A.
Published: November 2004

Several radiation boundary conditions for inhomogeneous acoustic media are investigated. Previous investigators have developed various approximate radiation conditions and have studied their accuracy by calculating an effective reflection coefficient for plane waves incident on such radiating boundaries. In this paper, it is shown that effective reflection coefficients can be calculated for a class of parabolic approximations to the Helmholtz equation. These results are valid for vertically heterogeneous media. Comparison of these radiation conditions is given through numerical examples.
A QUALITATIVE BELIEF LOGIC
Authors: HARMANEC DAVID , HÁJEK PETR
Published: November 2004

Belief function theory is one of broadly used numerical formalisms for uncertainty processing. It was also studied in its qualitative form. In this paper we study relationship between this qualitative belief function theory and modal logic. We present a sound system of axioms and show its completeness with respect to sematics considered.
A FUZZY NEURAL NETWORK MODEL FOR FUZZY INFERENCE AND RULE TUNING
Authors: LEE KEON-MYUNG , KWANG DONG-HOON , WANG HYUNG LEEK
Published: November 2004

It is relatively easy to create rough fuzzy rules for a target system. However, it is time-consuming and difficult to fine-tune them for improving their behavior. Meanwhile, in the process of fuzzy inference the defuzzification operation takes most of the inferencing time. In this paper, we propose a fuzzy neural network model which makes it possible to tune fuzzy rules by employing neural networks and reduces the burden of defuzzification operation. In addition, to show the applicability of the proposed model we perform an experiment and present its result.
FUZZY C-MEANS CLUSTERING ALGORITHM WITH TWO LAYERS AND ITS APPLICATION TO IMAGE SEGMENTATION BASED ON TWO-DIMENSIONAL HISTOGRAM
Authors: XIE WEIXIN , LIU JIANZHUANG
Published: November 2004

This paper presents a fast fuzzy c-means (FCM) clustering algorithm with two layers, which is a mergence of hard clustering and fuzzy clustering. The result of hard clustering is used to initialize the c cluster centers in fuzzy clustering, and then the number of iteration steps is reduced. The application of the proposed algorithm to image segmentation based on the two dimensional histogram is provided to show its computational efficience.
A MEASURE OF AVERAGE SENSITIVITY FOR FUZZY LOGICS
Authors: NGUYEN HUNG T. , KREINOVICH VLADIK , TOLBERT DANA
Published: November 2004

Experts usually express their uncertainty by words of natural languages (like "perhaps", "for sure", etc). In the majority of expert systems and intelligent control systems, uncertainty of experts' statements is represented by a number from the interval [0, 1]. There are many different procedures that translate the words that experts use into numbers from [0, 1]. For one and the same word, different procedures can lead to different numbers. Some &– and ∨–operations are very sensitive to this difference in the sense that small changes in t(A) and t(B) can lead to absolutely different estimates for t(A&B) and t(A ∨ B). In view of that, it is reasonable to restrict ourselves to the operations that are the least sensitive to such changes.

In this paper, we prove that ab and a + b − ab are "in the average" the least sensitive &– and ∨–operations. This result is in good accordance with the experimental data according to which in. many cases, these operations provide the best description of how experts actually think.

We also show how this idea can be applied to other logical connectives (e.g., "not"), and to the choice of membership functions.
SATURATEDNESS AND A HIERARCHY OF APPROXIMATE IDENTITIES
Authors: CHAKRABORTY M. K. , BANERJEE MOHUA
Published: November 2004

In this paper, 'identity' is eventually considered to be determined by a specified collection of 'properties' represented extensionally by subsets. Generally, the collection may contain fuzzy subsets representing vague properties, thus rendering vagueness to the concept of identity. Saturatedness condition, which in essence is a portion of Leibniz's principle of identity, has been dealt with in some detail. A hierarchy of identities is obtained. This hierarchy also indicates some relationship between the concepts 'identity' and 'property'. Some applications of the results to the modelling of indistinguishability in information systems have been indicated.
RECOGNISING ENTREPRENEURIAL POTENTIAL IN GRADUATE BUSINESS START-UPS: THE DEVELOPMENT OF A BEHAVIOURALLY BASED ASSESSMENT TOOL
Authors: JOHNSON DAVID , MA ROSA
Published: November 2004

This paper presents the initial results of an investigation oriented towards developing a Behaviourally Anchored Rating Scale (BARS) system to assess the entrepreneurial potential of individuals who are either running their own business or are in the process of considering start-up.

A review of the literature identified seven dimensions as necessary, if not exhaustive, attributes of a successful entrepreneur. They are vision, internal locus of control, achievement orientation, calculated risk taking, need for autonomy, creativity and innovativeness, and opportunistic.

Previous psychological studies have focused primarily upon personality traits, attitudes, and more recently upon cognitive representations. The actual behaviour of the entrepreneur has been excluded from the analysis. The methodology developed within this paper seeks to overcome this deficit by developing the above mentioned BARS.

16 graduates who are at various stages in the business start-up process were interviewed and data collected regarding the performance of the business. The interview was structured around critical incidents in the recent history of the business and focused specifically upon the individual responses in terms of the seven core dimensions. The interviews were video recorded and transcribed. Assessments of the performance of the business were made by a number of independent assessors who rated each of the sample in terms of progress and success.

Initial findings indicate that the BARS do provide a valid measure of entrepreneurial potential as individuals who scored highly upon the BARS were those whose businesses were performing more successfully. As such, BARS could prove to be a very useful tool for research purposes and also in the selection and training of owner-managers and entrepreneurs. A longitudinal investigation is currently in preparation.
SINGAPOREAN ENTREPRENEURS—THE AUSTRALIAN CONNECTION
Authors: LEWIS PHILIP E.T.
Published: November 2004

This paper develops a framework for investigating the linkages between Singaporean entrepreneurs and Australia. The first link examined is through Singapore investment in Australia. There are about three thousand Singapore-based companies overseas with investments in a broad range of industries. Australia is among the top six investment host countries.

One of the most important links is through Singaporean entrepreneurs sending their children to Australia to be educated. Educational services are provided to the next generation of entrepreneurs and also provide familiarity with the political and economic environment in which Singapore entrepreneurs can do business in Australia.

Another important link is through migration of Singaporean entrepreneurs to Australia. Research shows that the flow of Singaporean students to Australia is a major factor in determining the flow of entrepreneurs to Australia. This flow is, however, also strongly influenced by the general economic conditions.

The issues explored in this paper are major given the importance of Asian entrepreneurs to Australia’s economic strategy of incorporation into the markets of Asia. The drain of entrepreneurs to Australia may also be of concern to Singapore. On the other hand, the links created with Singapore firms may be of long term benefit to Singapore.
ETHNIC ENCLAVES AND SMALL BUSINESS OWNERSHIP PATTERNS IN WESTERN AUSTRALIA
Authors: KELMAR JOHN H
Published: November 2004

The Western Australian population base has been expanding due to a policy of increasing the immigrant component of the total population. Most of these migrants enter Western Australia through the family program, whilst the skill component accounted for one third the size of the family migrants. The tendency of many migrants is to reside in areas where previous migrants from their region already reside, thus forming ethnic enclaves. However, upon arrival, a significant number of migrants find that their overseas experiences and qualifications are not recognised to the same extent in Western Australia, and so they seek employment through entrepreneurial activities. This study examines Australian Census 1991 data to investigate the source of the current migration trends, their tendency to enter into entrepreneurial activities through self-employment or becoming an employer, and examines differences which may occur through occupational backgrounds and sex.
DIFFICULTIES FACED BY SMEs IN OBTAINING FINANCING FROM FINANCIAL INSTITUTIONS
Authors: TEO SUSAN , CHEONG SERENE
Published: November 2004

Small and medium-size enterprises (SMEs) have long been recognised as one of the cornerstones of a country’s development. It is, thus, important to understand what contributes to their success as well as the difficulties they face. Surveys have shown that the lack of available financing from financial institutions is one of the biggest problems facing small businesses today. In this paper, we try to identify the aspects of obtaining financing that SMEs have most problems with as well as to determine which firm-specific factors (such as type of set-up, size of operation, years in operation and type of industry) contribute to the firms’ ability to borrow. The results of our survey indicate that the main reasons firms do not apply for financing from financial institutions are that they are unable or unwilling to provide information required; that they have other sources of funds available; and the high interest rates charged by the financial institutions. For the firms that applied, the main difficulties faced were the lack of collateral, the lack of proven track records, the lack of proper business plans and the need to show good sales turnover. Actions that may be taken by the SMEs, the financial institutions, the Singapore government and tertiary institutions are also discussed in this paper.
EXPERIENCE IN METRICS AND MEASUREMENTS FOR N-VERSION PROGRAMMING
Authors: LYU MICHAEL R. , CHEN JIA-HONG , AVIŽIENIS ALGIRDAS
Published: November 2004

The N-Version Programming (NVP) approach applies the idea of design diversity to obtain fault-tolerant software units, called N-Version Software (NVS) units. The effectiveness of this approach is examined by the software diversity achieved in the member versions of an NVS unit. We define and formalize the concept of design diversity and software diversity in this paper. Design diversity is a property naturally applicable to the NVP process to increase its fault-tolerance attributes. The baseline design diversity is characterized by the employment of independent programming teams in the NVP. More design diversity investigations could be enforced in the NVP design process, including different languages, different tools, different algorithms, and different methodologies. Software diversity is the resulting dissimilarities appearing in the NVS member versions. We characterize it from four different points of view that are designated as: structural diversity, fault diversity, tough-spot diversity, and failure diversity. Our goals are to find a way to quantify software diversity and to investigate the measurements which can be applied during the life cycle of NVS to gain confidence that operation will be dependable when NVS is actually employed. The versions from a six-language N-Version Programming project for fault-tolerant flight control software were used in the software diversity measurement.
THRESHOLD VOTING IS FUNDAMENTALLY SIMPLER THAN PLURALITY VOTING
Authors: PARHAMI BEHROOZ
Published: November 2004

We show that n-way plurality voting on a large unordered object space has time and space complexities of θ(n2) and θ(n), respectively. If the object space is ordered, then sorting can be used to reduce the time complexity to the optimal θ(n log n). We then prove that weighted t- out-of -∑vi threshold voting on such an object space has time complexity O(np) and needs working storage space for only p objects, where p=[(∑vi)/t]. Thus, unless t is very small, threshold voting is considerably simpler than plurality voting. As a corollary, weighted majority voting can be performed in linear time with working storage for a single input object.
A MANIFOLD GROWTH MODEL THAT UNIFIES SOFTWARE RELIABILITY GROWTH MODELS
Authors: FURUYAMA TSUNEO , NAKAGAWA YUTAKA
Published: November 2004

Ensuring software reliability is one of the most important issues in software development. High-precision fault rate prediction is a powerful method for ensuring reliability. A variety of highly accurate methods have been proposed to date, the most widely used being software reliability growth models (SRGMs) based on how the cumulative number of faults detected varies over time. This paper presents a manifold model that unifies existing SRGMs. This model, in addition to reducing the labor in selecting the most suitable model for each growth curve, makes it possible to predict the number of remaining faults for complicated fault growth curves with higher accuracy than previously. Using the manifold model, this paper clarifies the relationships between the existing SRGMs. Then, using actual data, it compares the fault estimation accuracy of the manifold model and representative SRGMs, showing the usefulness of this model.
CONNECTIVITY RELIABILITIES AND HAMILTONIAN RELIABILITIES OF LINEAR AND CIRCULAR CONSECUTIVE-2 LINK SYSTEMS
Authors: HWANG F.K. , WINNIE LI WEN-CHING
Published: November 2004

We give recursive equations and closed form solutions for two kinds of reliability for linear and circular consecutive-2 link systems under a general reliability model where nodes and the two types of links can all fail and with different probabilities. The results can be extended to the case when the reliabilities of nodes (respectively, the two types of links) are not necessarily constant.
THE DESIGN OF OPTIMAL NMR PIPELINE SYSTEMS
Authors: FERNANDES RONALD , KAMAT SANJAY , KANEVSKY ARKADY
Published: November 2004

In this paper we develop a pipeline processing system called NMR pipeline. In an NMR pipeline, processing elements at each stage are replicated to achieve high fault tolerance. Each stage of the pipeline is an N-Modular Redundant (NMR) System. This design combines the benefits of pipeline processing and NMR systems and is suitable for high speed safety-critical computing. Reliability analysis of this system is presented taking into account possible failures of processing and communication elements. The optimality of the system is defined in terms a suitably defined cost function that accounts for the component costs and the costs associated with system unreliability.
PREDICTING SOFTWARE QUALITY, DURING TESTING, USING NEURAL NETWORK MODELS: A COMPARATIVE STUDY
Authors: KHOSHGOFTAAR TAGHI M. , SZABO ROBERT M.
Published: November 2004

The application of statistical modeling techniques has been an intensely pursued area of research in the field of software engineering. The goal has been to model software quality and use that information to better understand the software development process. Neural network modeling methods have recently been applied to this field. The results reported indicate that neural network models have better predictive quality than some statistical models when predicting reliability and the number of faults.

In this paper, we will investigate the application of principal components analysis to neural network modeling as a way of improving the predictive quality of neural network quality models. Using data we collected from a large commercial software system, we developed a multiple regression model using the principal components. Then, we trained two neural nets, one with raw data, and one with principal components. Then, we compare the predictive quality of the three competing models for a variety of quality measures.
A FRAMEWORK FOR ADAPTIVE FAULT MANAGEMENT IN DISTRIBUTED COMPUTING SYSTEMS
Authors: GANTENBEIN REX E. , LAWRENCE THOMAS F. , SHIN SUNG YUN
Published: November 2004

Most strategies for fault management in distributed computing systems are effective only for a narrow range of fault classes. In some systems, however, a wide range of operating environments may be encountered that require different strategies to be used at different times. Adaptive fault management can be used to increase a system’s survivability under conditions that can suddenly and drastically change, but there are a number of problems that must be solved for this paradigm to be successful.

Two of these problems are the characterization of fault management techniques and the evaluation of system behavior relative to system requirements. A taxonomy for distributed fault management characterizes a variety of well-known techniques for achieving survivability in distributed systems. A generalized metric can then evaluate the effectiveness of different fault management techniques under changing conditions. These two concepts may be used as a framework for understanding how an adaptive system can dynamically select an appropriate fault management strategy from a number of alternatives in response to changes in its operating environment. Applications that use multiple fault management techniques to enhance their survivability illustrate the applicability of this framework.
Molecular determinants of the prothrombogenic phenotype assumed by inflamed colonic venules
Authors: Mori Mikiji , Salter James W. , Vowinkel Thorsten , Krieglstein Christian F. , Stokes Karen Y. , Granger D. Neil
Published: November 2004

Although platelets have been implicated in the pathogenesis of human inflammatory bowel diseases, little is known about the magnitude of platelet accumulation in the inflamed bowel, what regulates this process, and its relevance to the overall inflammatory response. In this study, intravital video microscopy was used to monitor the trafficking of platelets and leukocytes and vascular permeability in colonic venules during the development of colonic inflammation induced by 3% dextran sodium sulfate (DSS). Blocking antibodies directed against different adhesion molecules as well as P-selectin-deficient mice were used to define the adhesive determinants of DSS-induced platelet recruitment. DSS induced an accumulation of adherent platelets that was temporally correlated with the appearance of adherent leukocytes and with disease severity. Platelet adhesion and, to a lesser extent, leukocyte adhesion were attenuated by immunoblockade of P-selectin and its ligand P-selectin glycoprotein ligand-1 (PSGL-1), with contributions from both platelet- and endothelial cell-associated P-selectin. DSS induced a rapid and sustained increase in vascular permeability that was greatly attenuated in P-selectin-deficient mice. P-selectin bone marrow chimeras revealed that both endothelial cell- and platelet-associated P-selectin contribute to the P-selectin expression detected in the inflamed colonic microvasculature, with endothelial P-selectin making a larger contribution. Our findings indicate that colonic inflammation is associated with the induction of a prothrombogenic phenotype in the colonic microcirculation, with P-selectin and its ligand PSGL-1 playing a major role in the recruitment of platelets.