19,637 research outputs found
Chaotic Combustion in Spark Ignition Engines
We analyse the combustion process in a spark ignition engine using the
experimental data of an internal pressure during the combustion process and
show that the system can be driven to chaotic behaviour. Our conclusion is
based on the observation of unperiodicity in the time series, suitable
stroboscopic maps and a complex structure of a reconstructed strange attractor.
This analysis can explain that in some circumstances the level of noise in
spark ignition engines increases considerably due to nonlinear dynamics of a
combustion process.Comment: 5 pages, figures can be obtained from
http://archimedes.pol.lublin.pl/~raf/graf/figures.pd
Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser
We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters. © 2011 Author(s)
Bifurcation and chaos in the double well Duffing-van der Pol oscillator: Numerical and analytical studies
The behaviour of a driven double well Duffing-van der Pol (DVP) oscillator
for a specific parametric choice () is studied. The
existence of different attractors in the system parameters () domain
is examined and a detailed account of various steady states for fixed damping
is presented. Transition from quasiperiodic to periodic motion through chaotic
oscillations is reported. The intervening chaotic regime is further shown to
possess islands of phase-locked states and periodic windows (including period
doubling regions), boundary crisis, all the three classes of intermittencies,
and transient chaos. We also observe the existence of local-global bifurcation
of intermittent catastrophe type and global bifurcation of blue-sky catastrophe
type during transition from quasiperiodic to periodic solutions. Using a
perturbative periodic solution, an investigation of the various forms of
instablities allows one to predict Neimark instablity in the plane
and eventually results in the approximate predictive criteria for the chaotic
region.Comment: 15 pages (13 figures), RevTeX, please e-mail Lakshmanan for figures,
to appear in Phys. Rev. E. (E-mail: [email protected]
Using skewness and the first-digit phenomenon to identify dynamical transitions in cardiac models
Disruptions in the normal rhythmic functioning of the heart, termed as
arrhythmia, often result from qualitative changes in the excitation dynamics of
the organ. The transitions between different types of arrhythmia are
accompanied by alterations in the spatiotemporal pattern of electrical activity
that can be measured by observing the time-intervals between successive
excitations of different regions of the cardiac tissue. Using biophysically
detailed models of cardiac activity we show that the distribution of these
time-intervals exhibit a systematic change in their skewness during such
dynamical transitions. Further, the leading digits of the normalized intervals
appear to fit Benford's law better at these transition points. This raises the
possibility of using these observations to design a clinical indicator for
identifying changes in the nature of arrhythmia. More importantly, our results
reveal an intriguing relation between the changing skewness of a distribution
and its agreement with Benford's law, both of which have been independently
proposed earlier as indicators of regime shift in dynamical systems.Comment: 11 pages, 6 figures; incorporating changes as in the published
versio
Recurrence networks - A novel paradigm for nonlinear time series analysis
This paper presents a new approach for analysing structural properties of
time series from complex systems. Starting from the concept of recurrences in
phase space, the recurrence matrix of a time series is interpreted as the
adjacency matrix of an associated complex network which links different points
in time if the evolution of the considered states is very similar. A critical
comparison of these recurrence networks with similar existing techniques is
presented, revealing strong conceptual benefits of the new approach which can
be considered as a unifying framework for transforming time series into complex
networks that also includes other methods as special cases.
It is demonstrated that there are fundamental relationships between the
topological properties of recurrence networks and the statistical properties of
the phase space density of the underlying dynamical system. Hence, the network
description yields new quantitative characteristics of the dynamical complexity
of a time series, which substantially complement existing measures of
recurrence quantification analysis
Fractal Measures and Nonlinear Dynamics of Overcontact Binaries
Overcontact binary stars are systems of two stars where the component stars
are in contact with each other. This implies that they share a common envelope
of gas. In this work we seek signatures of nonlinearity and chaos in these
stars by using time series analysis techniques. We use three main techniques,
namely the correlation dimension,f (\alpha) spectrum and the bicoherence. The
former two are calculated from the reconstructed dynamics, while the latter is
calculated from the Fourier transforms of the time series of intensity
variations(light curves) of these stars. Our dataset consists of data from 463
overcontact binary stars in the Kepler field of view [1]. Our analysis
indicates nonlinearity and signatures of chaos in almost all the light curves.
We also explore whether the underlying nonlinear properties of the stars are
related to their physical properties like fill-out-factor, a measure of the
extend of contact between the components of an overcontact binary system . We
observe that significant correlations exist between the fill out factor and the
nonlinear quantifiers. This correlation is more pronounced in specific
subcategories constructed based on the mass ratios and effective temperatures
of the binaries. The correlations observed can be indicative of variations in
the nonlinear properties of the star as it ages. We believe that this study
relating nonlinear and astrophysical properties of binary stars is the first of
its kind and is an important starting point for such studies in other
astrophysical objects displaying nonlinear dynamical behaviour.Comment: 17 pages, 12 figures, submitted to Communications in Nonlinear
Science and Numerical Simulatio
Complex Network Approach for Recurrence Analysis of Time Series
We propose a novel approach for analysing time series using complex network
theory. We identify the recurrence matrix calculated from time series with the
adjacency matrix of a complex network, and apply measures for the
characterisation of complex networks to this recurrence matrix. By using the
logistic map, we illustrate the potentials of these complex network measures
for detecting dynamical transitions. Finally we apply the proposed approach to
a marine palaeo-climate record and identify subtle changes of the climate
regime.Comment: 23 pages, 7 figure
Subdiffusion via dynamical localization induced by thermal equilibrium fluctuations
We reveal the mechanism of subdiffusion which emerges in a straightforward,
one dimensional classical nonequilibrium dynamics of a Brownian ratchet driven
by both a time-periodic force and Gaussian white noise. In a tailored parameter
set for which the deterministic counterpart is in a non-chaotic regime,
subdiffusion is a long-living transient whose lifetime can be many, many orders
of magnitude larger than characteristic time scales of the setup thus being
amenable to experimental observations. As a reason for this subdiffusive
behaviour in the coordinate space we identify thermal noise induced dynamical
localization in the velocity (momentum) space. This novel idea is distinct from
existing knowledge and has never been reported for any classical or quantum
systems. It suggests reconsideration of generally accepted opinion that
subdiffusion is due to road distributions or strong correlations which reflect
disorder, trapping, viscoelasticity of the medium or geometrical constraints.Comment: in press in Scientific Reports (2017
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