bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of methods to estimate the prevalence of ovine Johne's infection from pooled faecal samples
Authors: Toribio J‐ALML , Sergeant ESG
Published: August 2007

Objective  To compare estimates of ovine Johne's infection prevalence produced by several alternate methods based on pooled faecal culture (PFC) results with prevalence estimates based on individual faecal culture (IFC).

Procedure  Seven methods for estimating prevalence of infection based on PFC results were incorporated in a computer program, including methods for imperfect test sensitivity and specificity, for variable pool size and a Bayesian method that incorporates prior knowledge about test performance and prevalence. These methods were then used to analyse PFC data at one observation 30 months post‐vaccination in a field trial of a killed vaccine for the control of OJD, undertaken on three farms in New South Wales.

Results  Prevalence estimates, for three methods that assume a perfect test, were close to the IFC estimate, whereas for three other methods that assume an imperfect test, the estimated prevalence was generally higher than the IFC estimate. In comparison, the Bayesian approach produced more variable estimates that were substantially higher than the IFC estimate when an inappropriately high prior estimate of prevalence was used.

Conclusion  Despite the limitations of each method, two methods provided accurate and reasonable estimates of the prevalence assessed by IFC in all instances, and are appropriate for the analysis of data from this vaccine trial. One of these methods also has the advantage of allowing for variable pool size. However, further research is needed to develop a method that will simultaneously account for variation in pool size and in test sensitivity and specificity.
Comparison of ELISA and CFT assays forChlamydophila abortusantibodies in ovine sera
Authors: McCauley LME , Lancaster MJ , Young P , Butler KL , Ainsworth CGV
Published: August 2007

Objective To compare the sensitivity and specificity ofChlamydophila abortusantibody assays, to find a suitable serological assay for testing sheep for export.

Design Comparison of results from known positive and negative sheep populations.

Procedure Fifty‐five positive and fifty negative sera were analysed by four enzyme linked immunosorbent assays (ELISA), three using recombinant antigens based on the chlamydial polymorphic outer membrane proteins (POMP90‐3, POMP90‐4, POMP80‐90) and one using a synthetic peptide based on chlamydial major outer membrane proteins (MOMP‐P). They were also analysed by complement fixation tests (CFT) using crude antigens from chlamydia isolated from an Australian sheep, a Californian parakeet and a Texan turkey. Assay sensitivity and specificity were expressed as point estimates and 95% confidence intervals. Results were compared using McNemar's test for paired samples.

Results ELISA sensitivity ranged from 70 to 98% and complement fixation test sensitivity from 60 to 96%; with POMP90‐3 > POMP90‐4 > CFT (parakeet) > CFT (turkey) > POMP80‐90 > MOMP‐P > CFT (sheep). There was no significant difference from POMP90‐3 to POMP80‐90 (P > 0.05). ELISA specificity ranged from 88 to 100% and CFT specificity was 100% for all three antigens; with CFT and POMP90‐4 > MOMP‐P > POMP80‐90 > POMP90‐3. There was no significant difference from CFT to POMP80‐90 (P > 0.05). Changing the CFT cut‐off from 1:32 to 1:4 substantially reduced the specificity with little improvement in sensitivity.

Conclusion  Assays using POMP90‐4, POMP80‐90, CFT (parakeet) and CFT (turkey) had equivalent sensitivity and specificity; none of the ELISAs were more specific than any CFT. The POMP80‐90 ELISA is recommended as an alternative to CFT (parakeet) but as its specificity is not ideal the search for a more specific assay should continue.
Abstract
Authors: Cecil James
Published: August 2007

Geddes, Dorothy A. M., Edgar, W. M., Jenkins, G. N., and Rugg‐Gunn, A. J. Apples, salted peanuts and plaque pH. Brit. Dent. J., 142:317–9, May 17, 1977.
Topical Effects of Fluoride in the Reversal and Prevention of Dental Decay
Authors: Featherstone John D. B.
Published: August 2007

This paper briefly reviews the clinical evidence for, and the science behind, the topical effects of fluoride in the inhibition and reversal of dental caries. Fluoride from topical sources such as drinking water, mouthrinses, dentifrice, and office‐ applied gels and foams inhibits demineralization and enhances remineralization. Inhibition of demineralization occurs when fluoride diffuses into the tooth and adsorbs to the crystal surfaces, protecting them from further acid attack. During times when the plaque pH is raised by salivary buffering, remineralization takes place through calcium and phosphate diffusing to the crystal surfaces in the subsurface lesion and building a new veneer on the remaining crystal remnants in the lesion. Fluoride speeds up this process, is incorporated together with calcium and phosphate, and leaves the crystal much more acid resistant. Remineralization is the body's natural caries repair process.
Systemic Benefits of Fluoride and Fluoridation
Authors: Newbrun Ernest
Published: August 2007

Clinical trials, animal studies, and in vitro tests demonstrate effectiveness of exposure to topical (posteruptive) fluoride in caries prevention and reduction of enamel dissolution. However, careful analyses of human epidemiologic data on caries increments, following communal water fluoridation, show unquestionably that fluoride has an important preemptive effect on caries in permanent teeth, particularly on pit and fissure surfaces. These preemptive or systemic benefits also apply to the use of fluoride supplements or fluoridated salt when used continuously during the period of tooth formation. The role of systemic fluoride in caries prevention is neither “minimal” nor “of borderline significance.” On the contrary, it is a major factor in preventing pit and fissure caries, the most common site of tooth decay. Maximal caries‐preventive effects of water fluoridation are achieved by exposure to optimal fluoride levels both pre‐ and posteruptively.
Pre‐ and Posteruptive Fluoride: Do Both Actions Control Caries?
Authors: Burt Brian A.
Published: August 2007

Discussion, which can get spirited, has been going on about fluoride's primary mode of action for some years. In the early days of fluoride research, it was assumed that the anticaries benefits of fluoride came from preeruptive effects; however, posteruptive action was soon evident. Today the primacy of the posteruptive hypothesis is hardly questioned; remaining questions concern the role of preeruptive fluoride. We are in the age of evidence‐based dentistry, where we expect scientific evidence to shape our conclusions. In this cursory look at the data from fluoride studies, the data to support the posteruptive hypothesis are consistent from laboratory to epidemiology; findings in human populations support the mechanisms of action that have been demonstrated in the laboratory. With the preeruptive hypothesis, there is some evidence in support; however, the data are not consistent across the different areas of study. As a result, the posteruptive hypothesis can be readily adopted as the primary mechanism for fluoride's anticariogenic action. Preeruptive fluoride may have some anticaries action; but when the evidence‐based philosophy is applied, the inconsistencies around the preeruptive hypothesis make it hard to adopt.
PIV Measurements in Square Backward-Facing Step
Authors: Piirto Mika , Karvinen Aku , Ahlstedt Hannu , Saarenrinne Pentti , Karvinen Reijo
Published: August 2007

Measurements with both two-dimensional (2D) two-component and three-component stereo particle image velocimetry (PIV) and computation in 2D and three-dimensional (3D) using Reynolds stress turbulence model with commercial code are carried out in a square duct backward-facing step (BFS) in a turbulent water flow at three Reynolds numbers of about 12,000, 21,000, and 55,000 based on the step height h and the inlet streamwise maximum mean velocity U0. The reattachment locations measured at a distance of Δy=0.0322h from the wall are 5.3h, 5.6h, and 5.7h, respectively. The inlet flow condition is fully developed duct flow before the step change with the expansion ratio of 1.2. PIV results show that the mean velocity, root mean square (rms) velocity profiles, and Reynolds shear stress profiles in all the experimental flow cases are almost identical in the separated shear-layer region when they are nondimensionalized by U0. The sidewall effect of the square BFS flow is analyzed by comparing the experimental statistics with direct numerical simulation (DNS) and Reynolds stress model (RSM) data. For this purpose, the simulation is carried out for both 2D BFS and for square BFS having the same geometry in the 3D case as the experimental case at the lowest Reynolds number. A clear difference is observed in rms and Reynolds shear stress profiles between square BFS experimental results and DNS results in 2D channel in the spanwise direction. The spanwise rms velocity difference is about 30%, with experimental tests showing higher values than DNS, while in contrast, turbulence intensities in streamwise and vertical directions show slightly lower values than DNS. However, with the modeling, the turbulence statistical differences between 2D and 3D RSM cases are very modest. The square BFS indicates 0.5h–1.5h smaller reattachment distances than the reattachment lengths of 2D flow cases.
New Model for Compressible Vortices
Authors: Aboelkassem Yasser , Vatistas Georgios H.
Published: August 2007

A new analytical solution for self-similar compressible vortices is derived in this paper. Based on the previous incompressible formulation of intense vortices, we derived a theoretical model that includes density and temperature variations. The governing equations are simplified assuming strong vortex conditions. Part of the hydrodynamic problem (mass and momentum) is shown to be analogous to the incompressible kind and as such the velocity is obtained through a straightforward variable transformation. Since all the velocity components are bounded in the radial direction, the density and pressure are then determined by standard numerical integration without the usual stringent simplification for the radial velocity. While compressibility is shown not to affect the tangential velocity, it influences only the meridional flow (radial and axial velocities). The temperature, pressure, and density are found to decrease along the converging flow direction. The traditional homentropic flow hypothesis, often employed in vortex stability and optical studies, is shown to undervalue the density and greatly overestimate the temperature. Comparable to vorticity diffusion balance for the incompressible case, the incoming flow carries the required energy to offset the contributions of conduction, viscous dissipation, and material expansion, thus keeping the temperature steady. This model is general and can be used to obtain a compressible version for all classical previous incompressible analysis from the literature such as Rankine, Burgers, Taylor, and Sullivan vortices.
Power Law Velocity Profile in the Turbulent Boundary Layer on Transitional Rough Surfaces
Authors: Afzal Noor
Published: August 2007

A new approach to scaling of transitional wall roughness in turbulent flow is introduced by a new nondimensional roughness scale ϕ. This scale gives rise to an inner viscous length scale ϕν∕uτ, inner wall transitional variable, roughness friction Reynolds number, and roughness Reynolds number. The velocity distribution, just above the roughness level, turns out to be a universal relationship for all kinds of roughness (transitional, fully smooth, and fully rough surfaces), but depends implicitly on roughness scale. The open turbulent boundary layer equations, without any closure model, have been analyzed in the inner wall and outer wake layers, and matching by the Izakson-Millikan-Kolmogorov hypothesis leads to an open functional equation. An alternate open functional equation is obtained from the ratio of two successive derivatives of the basic functional equation of Izakson and Millikan, which admits two functional solutions: the power law velocity profile and the log law velocity profile. The envelope of the skin friction power law gives the log law, as well as the power law index and prefactor as the functions of roughness friction Reynolds number or skin friction coefficient as appropriate. All the results for power law and log law velocity and skin friction distributions, as well as power law constants are explicitly independent of the transitional wall roughness. The universality of these relations is supported very well by extensive experimental data from transitional rough walls for various different types of roughnesses. On the other hand, there are no universal scalings in traditional variables, and different expressions are needed for various types of roughness, such as inflectional roughness, monotonic roughness, and others. To the lowest order, the outer layer flow is governed by the nonlinear turbulent wake equations that match with the power law theory as well as log law theory, in the overlap region. These outer equations are in equilibrium for constant value of m, the pressure gradient parameter, and under constant eddy viscosity closure model, the analytical and numerical solutions are presented.
Evolution and Turbulence Properties of Self-Sustained Transversely Oscillating Flow Induced by Fluidic Oscillator
Authors: Fung Huang Rong , Tong Chang Kuo
Published: August 2007

The evolution process and turbulence properties of a transversely oscillating flow induced by a fluidic oscillator are studied in a gravity-driven water tunnel. A planar jet is guided to impinge a specially designed crescent surface of a target blockage that is enclosed in a cavity of a fluidic oscillator. The geometric configuration of the cavity transforms the inherent stability characteristics of the jet from convective instability to absolute instability, so that the jet precedes the persistent back and forth swinging in the cavity. The swinging jet is subsequently directed through two passages and issued alternatively out of the fluidic oscillator. Two short plates are installed near the exits of the alternatively issuing pulsatile jets to deflect the jets toward the central axis. The deflected jets impinge with each other and form a pair of counter-rotating vortices in the near wake of the oscillator with a stagnation point at the impingement point. The stagnation point of the counter-rotating vortex pair moves back and forth transversely because of the phase difference existing between the two issued jets. The merged flow evolving from the counter-rotating vortices formed by the impingement of the two pulsatile jets therefore presents complex behavior of transverse oscillation. The topological models corresponding to the flow evolution are constructed to illustrate the oscillation process of the oscillating flow. Significant momentum dispersion and large turbulence intensity are induced by the transverse oscillation of the merged flow. The statistical turbulence properties show that the Lagrangian integral time and length scales of the turbulence eddies (the fine-scale structure) produced in the oscillating flow are drastically reduced.
Cavitation Influence on von Kármán Vortex Shedding and Induced Hydrofoil Vibrations
Authors: Ausoni Philippe , Farhat Mohamed , Escaler Xavier , Egusquiza Eduard , Avellan François
Published: August 2007

The present study deals with the shedding process of the von Kármán vortices at the trailing edge of a 2D hydrofoil at high Reynolds number Reh=25×103–65×103. This research focuses mainly on the effects of cavitation and fluid-structure interaction on the mechanism of the vortex generation. The vortex shedding frequency, derived from the flow-induced vibration measurement, is found to follow the Strouhal law provided that no hydrofoil resonance frequencies are excited, i.e., lock-off. For such a regime, the von Kármán vortices exhibit strong spanwise 3D instabilities and the cavitation inception index is linearly dependent on the square root of the Reynolds number. In the case of resonance, the vortex shedding frequency is locked onto the hydrofoil eigenfrequency and the spatial coherence is enhanced with a quasi-2D shape. The measurements of the hydrofoil wall velocity amplitude and phase reveal the first torsion eigenmotion. In this case, the cavitation inception index is found to be significantly increased compared to lock-off conditions. It makes clear that the vortex roll-up is amplified by the phase locked vibrations of the trailing edge. For the cavitation inception index, a new correlation relationship that encompasses the entire range of Reynolds numbers, including both the lock-off and the lock-in cases, is proposed and validated. In contrast to the earlier models, the new correlation takes into account the trailing edge displacement velocity. In addition, it is found that the transverse velocity of the trailing edge increases the vortex strength linearly. This effect is important in the context of the fluid-structure interaction, since it implies that the velocity of the hydrofoil trailing edge increases the fluctuating forces on the body. It is also demonstrated that cavitation developing in the vortex street cannot be considered as a passive agent for the turbulent wake flow. In fact, for fully developed cavitation, the vortex shedding frequency increases up to 15%, which is accompanied by the increase of the vortex advection velocity and reduction of the streamwise vortex spacing. In addition, a significant increase of the vortex-induced vibration level is found at cavitation onset. These effects are addressed and thought to be a result of the increase of the vorticity by cavitation.
PIV Study of Shallow Open Channel Flow Over d- and k-Type Transverse Ribs
Authors: Tachie M. F. , Adane K. K.
Published: August 2007

A particle image velocimetry was used to study shallow open channel turbulent flow over d-type and k-type transverse ribs of square, circular, and semi-circular cross sections. The ratio of boundary layer thickness to depth of flow varied from 50% to 90%. The mean velocities and turbulent quantities were evaluated at the top plane of the ribs to characterize interaction between the cavities and overlying boundary layer. It was found that the overlying boundary layer interacts more strongly with k-type cavities than observed for d-type cavities. The profiles of the mean velocities and turbulent statistics were then spatially averaged over a pitch, and these profiles were used to study the effects of rib type and cross section on the flow field. The mean velocity gradients were found to be non-negligible across the boundary layer, and the implications of this observation for momentum transport, eddy viscosity, and mixing length distributions are discussed. The results show that the skin friction coefficient, Reynolds stresses and mixing length distributions are independent of rib cross section for d-type. For the k-type ribs, significant variations in skin friction coefficient values, mean flow, and turbulence fields are observed between square ribs and circular/semi-circular ribs.
Vortex Dynamics and Low-Pressure Fluctuations in the Tip-Clearance Flow
Authors: You Donghyun , Wang Meng , Moin Parviz , Mittal Rajat
Published: August 2007

The tip-clearance flow in axial turbomachines is studied using large-eddy simulation with particular emphasis on understanding the unsteady characteristics of the tip-leakage vortical structures and the underlying mechanisms for cavitation-inducing low-pressure fluctuations. A systematic and detailed analysis of the velocity and pressure fields has been made in a linear cascade with a moving end-wall. The generation and evolution of the tip-leakage vortical structures have been investigated throughout the cascade using mean streamlines and λ2 contours. An analysis of the energy spectra and space-time correlations of the velocity fluctuations suggests that the tip-leakage vortex is subject to a pitchwise low frequency wandering motion. Detailed statistics of the pressure fields has been analyzed to draw inferences on cavitation. The regions of low pressure relative to the mean values coincide with regions of strong pressure fluctuations, and the regions are found to be highly correlated with the vortical structures in the tip-leakage flow, particularly in the tip-leakage and tip-separation vortices.
Surface Tension Measurement at High Temperatures by using Dynamics of Melt Flow
Authors: Moradian A. , Mostaghimi J.
Published: August 2007

Surface tension of melts at high temperature has significant effects on different industrial processes. In a new containerless method for surface tension measurement, an atmospheric radio-frequency inductively coupled plasma melts metallic or ceramic rods and a high-speed charge-coupled device records the drop formation caused by melting. Pendant drops produced by the melt flow are compared with the theoretical Young–Laplace (YL) profiles. Moreover, the dynamics of the melt flow is mimicked by using numerical simulations of drop injection from a nozzle. The numerical model solves the axisymmetric Navier–Stokes equations for both the melt and the surrounding gas by using the finite volume method. Since the YL equations provide theoretical pendant drop profiles based on an inviscid quasiequilibrium condition, a detailed study of the differences between experimental, numerical, and theoretical profiles demonstrates some of the hydrodynamic effects influencing the surface tension measurement methods, which are based on drop profiles. Results from this surface tension measurement method, in addition to a discussion on the hydrodynamic effects, are presented.
GAZE TRACKING SYSTEM MODEL BASED ON PHYSICAL PARAMETERS
Authors: VILLANUEVA ARANTXA , CABEZA RAFAEL , PORTA SONIA
Published: August 2007

In the past years, research in eye tracking development and applications has attracted much attention and the possibility of interacting with a computer employing just gaze information is becoming more and more feasible. Efforts in eye tracking cover a broad spectrum of fields, system mathematical modeling being an important aspect in this research. Expressions relating to several elements and variables of the gaze tracker would lead to establish geometric relations and to find out symmetrical behaviors of the human eye when looking at a screen. To this end a deep knowledge of projective geometry as well as eye physiology and kinematics are basic. This paper presents a model for a bright-pupil technique tracker fully based on realistic parameters describing the system elements. The system so modeled is superior to that obtained with generic expressions based on linear or quadratic expressions. Moreover, model symmetry knowledge leads to more effective and simpler calibration strategies, resulting in just two calibration points needed to fit the optical axis and only three points to adjust the visual axis. Reducing considerably the time spent by other systems employing more calibration points renders a more attractive model.
A WEIGHTED SUPPORT VECTOR MACHINE FOR DATA CLASSIFICATION
Authors: YANG XULEI , SONG QING , WANG YUE
Published: August 2007

This paper presents a weighted support vector machine (WSVM) to improve the outlier sensitivity problem of standard support vector machine (SVM) for two-class data classification. The basic idea is to assign different weights to different data points such that the WSVM training algorithm learns the decision surface according to the relative importance of data points in the training data set. The weights used in WSVM are generated by a robust fuzzy clustering algorithm, kernel-based possibilistic c-means (KPCM) algorithm, whose partition generates relative high values for important data points but low values for outliers. Experimental results indicate that the proposed method reduces the effect of outliers and yields higher classification rate than standard SVM does when outliers exist in the training data set.
A METHODOLOGY FOR IMPROVING THE PERFORMANCE OF NON-RANKER FEATURE SELECTION FILTERS
Authors: ROKACH LIOR , CHIZI BARAK , MAIMON ODED
Published: August 2007

Feature selection is the process of identifying relevant features in the dataset and discarding everything else as irrelevant and redundant. Since feature selection reduces the dimensionality of the data, it enables the learning algorithms to operate more effectively and rapidly. In some cases, classification performance can be improved; in other instances, the obtained classifier is more compact and can be easily interpreted. There is much work done on feature selection methods for creating ensemble of classifiers. Thus, these works examine how feature selection can help ensemble of classifiers to gain diversity. This paper examines a different direction, i.e. whether ensemble methodology can be used for improving feature selection performance. In this paper we present a general framework for creating several feature subsets and then combine them into a single subset. Theoretical and empirical results presented in this paper validate the hypothesis that this approach can help to find a better feature subset.
DISTRIBUTED LEARNING STRATEGY BASED ON CHIPS FOR CLASSIFICATION WITH LARGE-SCALE DATASET
Authors: YANG BO , SU XIAOHONG , WANG YADONG
Published: August 2007

Learning with very large-scale datasets is always necessary when handling real problems using artificial neural networks. However, it is still an open question how to balance computing efficiency and learning stability, when traditional neural networks spend a large amount of running time and memory to solve a problem with large-scale learning dataset. In this paper, we report the first evaluation of neural network distributed-learning strategies in large-scale classification over protein secondary structure. Our accomplishments include: (1) an architecture analysis on distributed-learning, (2) the development of scalable distributed system for large-scale dataset classification, (3) the description of a novel distributed-learning strategy based on chips, (4) a theoretical analysis of distributed-learning strategies for structure-distributed and data-distributed, (5) an investigation and experimental evaluation of distributed-learning strategy based-on chips with respect to time complexity and their effect on the classification accuracy of artificial neural networks. It is demonstrated that the novel distributed-learning strategy is better-balanced in parallel computing efficiency and stability as compared with the previous algorithms. The application of the protein secondary structure prediction demonstrates that this method is feasible and effective in practical applications.
EXTENDED VISUAL SECRET SHARING SCHEMES: IMPROVING THE SHADOW IMAGE QUALITY
Authors: YANG CHING-NUNG , CHEN TSE-SHIH
Published: August 2007

Visual secret sharing (VSS) scheme is a perfectly secure method to divide a secret image into several noise-like shadow images by splitting a secret pixel into black and white subpixels. Unlike other secret sharing schemes, the VSS scheme can be easily decoded by the human visual sight when staking shadow images. However, noise-like shadows are unusual and suspected by censors when delivered by e-mail or fax. Also, noise-like shadows are difficult to identify and manage when distributed. The problem was solved by adding the extended capability, a meaningful shadow image, in the so-called extended visual secret sharing (EVSS) scheme. In this paper, we present a new EVSS scheme by using gray and white subpixels to represent the secret pixel. Our proposed scheme still has the capability of visually revealing the secret image by stacking shadow images without the help of hardware and complex computation. When compared to the previous EVSS scheme, our new scheme has less number of subpixels to represent a secret pixel and the clearer shadow images.
COEVOLUTION OF NEAREST NEIGHBOR CLASSIFIERS
Authors: GAGNÉ CHRISTIAN , PARIZEAU MARC
Published: August 2007

This paper presents experiments of Nearest Neighbor (NN) classifier design using different evolutionary computation methods. Through multiobjective and coevolution techniques, it combines genetic algorithms and genetic programming to both select NN prototypes and design a neighborhood proximity measure, in order to produce a more efficient and robust classifier. The proposed approach is compared with the standard NN classifier, with and without the use of classic prototype selection methods, and classic data normalization. Results on both synthetic and real data sets show that the proposed methodology performs as well or better than other methods on all tested data sets.
INTERACTION OF FAST-SCALE AND SLOW-SCALE BIFURCATIONS IN CURRENT-MODE CONTROLLED DC/DC CONVERTERS
Authors: CHEN YANFENG , TSE CHI K. , WONG SIU-CHUNG , QIU SHUI-SHENG
Published: August 2007

This paper investigates the interaction of fast-scale and slow-scale bifurcations in the boost converter under current-mode control operating in continuous conduction mode. Effects of varying some chosen parameters on the qualitative behaviors of the system are studied in detail. Analysis is performed to identify the different types of bifurcation. Boundaries of stable region, slow-scale bifurcation region, fast-scale bifurcation region, interacting fast and slow-scale bifurcation regions are identified.
HARMONIC DISTORTION ANALYSIS BASED ON HOPF BIFURCATION THEOREM AND FAST FOURIER TRANSFORM
Authors: ROBBIO F. I. , PAOLINI E. E. , MOIOLA J. L. , CHEN G.
Published: August 2007

A frequency domain method is used to estimate the harmonic contents of a smooth oscillation arising from the Hopf bifurcation mechanism. The harmonic contents up to the eighth-order are well estimated, which agree with the results obtained from a completely different approach that measures the frequency content of a signal by using digital signal processing techniques such as the Fast Fourier Transform (FFT). The accuracy of the approximation is evaluated by computing the Floquet multipliers of the variational system based on the fact that for periodic solutions one multiplier must be +1. The separation from this theoretical value is proportional to the error of the approximation. A limitation of the frequency domain method is encountered when being used for continuing the secondary branch of limit cycle bifurcations, such as pitchfork and period-doubling bifurcations. Two examples are shown to illustrate the main results: Colpitts' oscillator with a pitchfork bifurcation of cycles, and Chua's circuit with a period-doubling bifurcation of cycles.
HIGHER-DIMENSIONAL PERIODIC AND CHAOTIC OSCILLATIONS FOR VISCOELASTIC MOVING BELT WITH MULTIPLE INTERNAL RESONANCES
Authors: ZHANG W. , SONG C. Z.
Published: August 2007

In this paper, higher-dimensional periodic and chaotic oscillations for a parametrically excited viscoelastic moving belt with multiple internal resonances are investigated for the first time. The external damping and internal damping of the material for the viscoelastic moving belt are considered simultaneously. First, the nonlinear governing equation of planar motion for the viscoelastic moving belt with the external damping is given. Then, the transverse nonlinear oscillations of the viscoelastic moving belt are considered. The method of multiple scales and the Galerkin approach are applied directly to the governing partial differential equation of motion for the viscoelastic moving belt to obtain an eight-dimensional averaged equation for the case of 1:2:3:4 internal resonances for the first-, the second-, the third- and the fourth-order modes and primary parametric resonance of the first-order mode. Finally, numerical method is used to investigate higher-dimensional periodic and chaotic motions of the viscoelastic moving belt. The results of numerical simulation demonstrate that there exist the period, period 2, period 4, multiple period and chaotic motions of the viscoelastic moving belt. The multipulse chaotic motions of the viscoelastic moving belt are observed from numerical simulations.
DETECTION THRESHOLD OF THE CONTROL PARAMETERS MODULATION IN A NOISY CHAOTIC MAP
Authors: ANOSOV O. , HENSEL B. , BERCZYNSKI S. , KRAVTSOV Yu. A.
Published: August 2007

The least squares procedure is suggested to reveal weak modulation of the control parameters in a noisy chaotic map in the presence of both dynamical and observational noise. For a map of a known dynamical structure, which is supposed to depend linearly on modulated control parameters, the procedure allows to detect both harmonic and pulse modulation, reducing the problem of modulation extraction from noisy empirical time series to the classical scheme of signal detection in noisy data. As an example, detection of harmonic modulation in a logistic map is studied. It is shown that threshold amplitude is subjected to the influence of the noise enhancement phenomenon in chaotic systems. Despite noise enhancement, the method suggested is shown to be superior to direct spectral analysis of chaotic time series due to wideband noise-like spectrum of the chaotic map, which masks the weak control parameters modulation.
IDENTIFICATION OF THE BELOUSOV–ZHABOTINSKII REACTION USING CELLULAR AUTOMATA MODELS
Authors: ZHAO Y. , BILLINGS S. A. , ROUTH ALEXANDER F.
Published: August 2007

New methods of identifying the transition rule of a Belousov–Zhabotinskii (BZ) reaction directly from experimental data using cellular automata (CA) models are investigated. The experimental set-up and new techniques for image pre-processing to ensure the identification of representative models are discussed including noise reduction, pixel and color calibration. Two kinds of models, the Greenberg–Hasting model (GHM) and the polynomial CA model are studied in detail. It is shown that the results of identifying a real BZ reacting system are very encouraging and the predicted patterns compare well with the imaged patterns both visually and quantitatively.
PRINCIPLES OF CHAOTIC SIGNAL RADAR
Authors: LIU ZHONG , ZHU XIAOHUA , HU WEN , JIANG FEI
Published: August 2007

The noise-like chaotic signal can be generated with very simple nonlinear circuits, and has broad bandwidth and aperiodic properties. These characteristics have drawn considerable attention in the radar community. In the past, the chaotic signal or its modulated version serves as a transmitting signal, and the traditional correlation-type receiver is used for processing. In this sense, the chaotic signal acts as a radar waveform in the noise signal radar, and hence the performance advantages are not distinct. Here, we present a scheme for processing chaotic radar signals. We find a simple relation between the target parameters (range and velocity) and the system parameters of chaos-generating system. With this relation, the measurement of the target parameters is transformed into estimation of the system parameters from the radar return signals. Equipped with high resolution parameter estimation techniques, the proposed principles provide a way to develop high resolution noise signal radars.
DYNAMICAL STATES IN A RING OF FOUR MUTUALLY COUPLED SELF-SUSTAINED ELECTRICAL SYSTEMS WITH TIME PERIODIC COUPLING
Authors: YAMAPI R. , BOWONG S.
Published: August 2007

We investigate in this Letter different dynamical states in the ring of four mutually coupled self-sustained electrical systems with time periodic coupling. The transition boundaries that can occur between instability and complete synchronization states when the coupling strength varies are derived using the Floquet theory and the Whittaker method. The effects of the amplitude of the periodic parametric perturbations of the coupling parameter on the stability boundaries are analyzed. Numerical simulations are then performed to complement the analytical results.
OSCILLATIONS ON THE EDGE OF CHAOS VIA DISSIPATION AND DIFFUSION
Authors: ITOH MAKOTO , CHUA LEON O.
Published: August 2007

The primary purpose of this paper is to show that simple dissipation can bring about oscillations in certain kinds of asymptotically stable nonlinear dynamical systems; namely when the system is locally active where the dissipation is introduced. Furthermore, if these nonlinear dynamical systems are coupled with appropriate choice of diffusion coefficients, then the coupled system can exhibit spatio-temporal oscillations. The secondary purpose of this paper is to show that spatio-temporal oscillations can occur in spatially discrete reaction diffusion equations operating on the edge of chaos, provided the array size is sufficiently large.
Part 1: Chapter 2 Outline History of Geological Research
Authors: Harland W. Brian
Published: August 2007

Useful records of observations perhaps began in 1596 with Barents' voyage and resulting chart. The many expeditions until the middle of the eighteenth century were primarily for whaling with minor additions to the charts. In 1758 A. R. Martin led a Swedish voyage and in 1773 C. J. Phipps commanded a British naval expedition, the first of several, to seek a northeast passage to the Pacific. They penetrated no further than Spitsbergen and made useful observations. At that time and for many years the British Admiralty was concerned with extensive Arctic exploration. The elaborate nature of these expeditions was not so much designed for scientific purposes as for useful employment for enterprising officers, with ships in numbers no longer needed in the period of naval supremacy after 1805. Hydrographic survey was often the principal achievement. In terms of efficiency and Arctic know-how the early whalers such as Scoresby were superior.

1827 may be considered as the year when geological work began, with expeditions from Norway (B. M. Keilhau 1831) and Britain (Capt. Parry, e.g. Horner 1860; Salter 1860). Keilhau, a geologist, visited Edgeoya and Bjornoya. Admiral Parry, Hydrographer of the Navy, wintered on
HMS Hecla
in Sorgfjorden where further specimens were collected. In 1837 an early Swedish expedition was directed by Loven. Then, 1838 to 1840, the French voyage of
La Recherche
took place under the Commission Scientifique du Nord (e.g. Robert 1840).

Only a selection of the many expeditions in the second half of the century are noted here.
Part 1: Chapter 3 Svalbard's geological frame
Authors: Brian Harland W.
Published: August 2007

This chapter gives an outline of the geology of Svalbard, an introduction to the principles applied in this work and a preview of the interpretations and conclusions that have come out of these studies.

The key position of Svalbard in relation to other Arctic lands is shown in a Polar projection (Fig. 3.1).

3.1 The space frame: Svalbard's structural frame

3.1.1 Solid outcrops

The conventional geological map of Svalbard shows in outline the outcrop areas according to age. (Fig. 3.2). Although rock ages are matters of interpretation, the diagrammatic map is at least consistent with the conclusions in this work. It differs from most maps in the larger outcrop of Vendian rocks within the basement. The outcrop pattern ignores Quaternary deposits, i.e. it is a solid geology map. It is diagrammatic because detail is impossible to show on this scale. The larger ice masses which obscure the exposure are also diagrammatic.

3.1.2 Regional descriptive sectors

Because the intention in this work is generally to describe rocks before interpreting their history and so not to begin with too many assumptions, the rocks are described in Part 2 of this work in the eight sectors or regions (Chapters 4 to 11) as shown in Fig. 3.3. Their boundaries are not fixed because it is convenient to treat some geological matters together in one chapter, even when they might overlap onto another. They are not terranes. Where strata are described the succession is presented as observed with the youngest at the top (as
Part 1: Chapter 5 Eastern Svalbard Platform
Authors: Harland W. B. , Kelly Simon R. A.
Published: August 2007

The Platform sequence (of younger rocks) i.e. latest Devonian, Carboniferous/Tournasian through Albian (and excluding Tertiary strata on land at least) appears once to have extended east of Spitsbergen in one sheet of which little now remains above sea level. It comprises two supergroups: Bünsow Land and Nordenskiöld Land.

The map (Fig. 5.1) illustrates that each of the islands rests on a much larger shelf, no deeper than 100 m and that with the exception of the outlying islands of Kong Karls Land and Hopen the 100 m isobath contains them within the Spitsbergen shallows.

In these circumstances, it would appear to be somewhat fortuitous as to what strata are preserved above sea level and it is perhaps remarkable that, if relatively thin strata with a maximum combined and exposed thickness in the area from (Tournaisian) through ?Barremian of
c
. 2 km, some representatives occur on each island with neither younger nor older rocks. If we plot the Triassic-Jurassic boundary, say the Rhaetian stage, it occurs at the top of the east Spitsbergen, south Nordaustlandet and south Edgeøya outcrops at heights respectively of about 550, 350 and 500 m a.s.l., at about 0-100 m at Kong Karls Land and at 370-300 m in Hopen. Thus departures from sea level over distances of 350 km N to S and 200 km E to W hardly exceed 500 m with average gradients of perhaps 300 m in 300 km - about half a degree. It is therefore reasonable on present evidence exposed above
Chapter 6 Northern Nordaustlandet (and associated Islands Storoya, Kvitoya)
Authors: Brian Harland W.
Published: August 2007

Nordaustlandet is the second largest island in the Svalbard archipelago. It has been generally inaccessible by ship because of polar pack ice except for the west coast, or in exceptional summers. Exploration has therefore been limited. The major part of the interior is covered by two large ice caps: Vestfonna and (the large) Austfonna which forms all of the southern coastline in the eastern part of the island. Pre-Devonian, mostly Precambrian outcrops of solid rock extend along the northern and northwestern seaboard. Wahlen-bergfjorden divides the west coast with post-Devonian rocks cropping out to the south of it. These have already been referred to in Chapter 5 so that the main object in this chapter is to outline what is known of the older rocks. Because of the ice caps covering the major part of the island, exposures, especially in the north and east, are often isolated on promontories along the highly indented coastline (Fig. 6.1).

After the early visit by Parry in 1828 research was largely by Swedish geologists with A.E. Nordenskiold's sledge journeys in 1861, 1866, 1869 and 1873.

A Swedish initiative led to the Russo-Swedish Arc of Meridian Survey along both sides of Hinlopenstretet. During the period 1899 to 1902 (De Geer 1923; Nathorst 1910) and later the Swedish-Norwegian expedition based at Sveanor in Murchisonfjorden (Kulling 1932) resulted in a thorough study of the Hecla Hoek rocks (Kulling 1934).

Alongside this were a series of multidisciplinary expeditions from Oxford University in 1924, 1935-36 and 1951. Sandford accompanied the
Chapter 9 Central western Spitsbergen
Authors: Harland W. Brian , Geddes Isobel , Doubleday Paul A.
Published: August 2007

The West Spitsbergen Orogen extends along the western side of Spitsbergen from Kongsfjorden to Sørkapp. It is the product of the latest main deformation event in Svalbard (Spitsbergian) dated provisionally as Eocene. The deformation is of a compressive or transpressive nature associated with the dextral strike-slip displacement between Svalbard and Greenland through Cenozoic time.

Within this fold and thrust belt earlier diastrophism is evident: Minor Late Cretaceous tilting with uplift took place. The main events were mid-Paleozoic. The mid-Paleozoic tectogenesis is commonly referred to as Caledonian. However the age of deformation appears to be mid-Ordovician rather than the typical mid-Silurian of the central and eastern terranes of Svalbard. To avoid confusion this is referred to as the
Eidembreen tectogenesis
(analogous with the M'Clintock Orogeny of northern Ellesmere Island). Some uncertainty must remain as to whether there was any Silurian diastrophism or more likely, late Devonian Early Carboniferous tectonism to match the Ellesmerian events of Arctic Canada. The rocks divide naturally into younger (Carboniferous through Eocene) strata, i.e. post-Devonian, and pre-Devonian older rocks, there being no Devonian exposure within the orogen.

Whereas the West Spitsbergen Orogeny was Paleogene (treated in Chapter 20) the orogen comprises the whole body of rock whether formed earlier or later. Because of the complex earlier history and variety of strata and structure along its length it is convenient to treat the structure in two parts, north and south of Isfjorden (Chapters 9 and 10 respectively). In this chapter the area treated comprises Oscar II Land and
Chapter 11 Southern Svalbard:Bjørnøya and submarine geology
Authors: Harland W. Brian , Geddes Isobel , Doubleday Paul A.
Published: August 2007

The area south of Spitsbergen (about 76°31'N) to latitude 74°N, and between longitudes 10°E and 35°E, by which Svalbard was first defined, contains the small island of Bjørnøya (Bear Island, Bären Insel) and the rest is sea (Fig. 11.1).

The 500 m isobath conveniently separates the edge of the Barents shelf from the Norwegian Sea Basin which runs south from Spitsbergen between 14° and 16°30'E. To the east, the large shallow area, Spitsbergenbanken, less than 100 m deep, supports Bjørnøya at its southwestern end, extends northeast to Hopen and joins Edge°ya. It is separated from Spitsbergen to the north by the Storfjordyrenna and to the east by Hopendjupet. These submarine valleys appear to drain westwards into the ocean deep with deltaic fronts convex westward.

This chapter focuses first on Bjørnøya which though small is a key outcrop in the Barents Sea and distinct in many respects from Spitsbergen being about 250 km distant. The chapter then surveys a little of what is known of the surrounding sub-sea area.

Bjørnøya (20 km N-S and 15 km E-W), as the southern outpost of Svalbard, has long been a key to Svalbard geology since it is generally free all year from tight sea ice. But though its location is convenient, its cliffs generally bar access. Indeed there are very few places where landing by other than inflatable dinghy are feasible. After the island had been claimed by a Norwegian syndicate in 1915 mining of Tournaisian coal began in 1916 and exported over 116000
Chapter 12 Pre-Vendian history
Authors: Harland W. Brian , Butterfield Nicholas J.
Published: August 2007

It so happens that rocks of Vendian age are extensive and are well exposed in Svalbard. This applies especially to early Vendian, i.e. Varanger, with two distinctive glacial horizons as are treated in the Chapter 13. The Early Varanger (Smalfjord) episode can be correlated in most sections and so provides a reference horizon which serves approximately to identify pre-Varanger rocks. The pre-Vendian rocks have yet to show such good correlation characters. Therefore in Svalbard it is convenient to consider pre-Vendian successions together. Their distribution is shown in the map (Fig. 12.1).

Some pre-Vendian sequences are punctuated by unconformities. Moreover, the sequences contain both high-grade metamorphosed and highly deformed rocks as well as undeformed fossiliferous strata. Therefore it is of interest to determine any Preeambrian diastroph-ism and even tectonothermal events. The term proto-basement was introduced (Harland 1997) to distinguish a Preeambrian basement, that formed in (say) Proterozoic time, from the ubiquitous basement formed by Early to mid Paleozoic tectogenesis, but made largely of Preeambrian rocks. It is to distinguish proto-basement within the basement underlying Devonian and Carboniferous strata. Proto-basement from such a study (structural, stratigraphic, isotopic) is shown in darker ornament in Fig. 12.1 and discussed in Section 12.3.

Were the spatial relationships between these localities originally as now, intense tectonism, metamorphism and magmatism would suggest a division of Preeambrian history in Svalbard by such events. But Svalbard, small though it is on a global scale, comprises three or more distinct provinces which in Preeambrian and early Paleozoic times may have