PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Nonlinear Dynamics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed2000

Stabilizing nonlinear dynamical systems by an adaptive adjustment mechanism

An adaptive adjustment mechanism is applied to stabilize multidimensional dynamical systems. Without utilizing any prior knowledge of the system itself, nor extra external control signals, the mechanism can ensure a large class of chaotic systems to converge to their "generic" stable periodic orbits.

Journal Article↗
PubMed2000

Nonlinear dynamics optically induced in nematic liquid crystals

We report the analysis of the dynamical regimes induced in a homeotropically aligned nematic liquid-crystal layer when an s-polarized laser beam impinges at a small incident angle. These regimes are studied by analyzing the time series of the variation of the polarization state of a light probe beam, recorded at different light intensities. A detailed description of the dynamical regimes, based on the analysis of the wavelet transforms performed on the observed time series, is presented. We recognize a first Hopf bifurcation followed by a gluing bifurcation, and a further transition toward an irregular regime. Similarities between our experimental results and a scenario of transition to chaos via a sequence of gluing bifurcations have been discussed.

Journal Article↗
PubMed2001

Spatiotemporal nonlinear dynamics of a magnetoelastic ribbon.

Magnetoelastic materials have a strong coupling between strain and magnetization, so applying a magnetic field to a magnetoelastic material can change its shape. This coupling leads to interesting dynamics. We have studied the dynamics of a wide ribbon of Metglass 2605sc which was driven by a magnetic field. The ribbon was suspended as a pendulum in a set of Helmholtz coils, which provided both dc and ac magnetic fields. Laser light was reflected off the ribbon to measure its angular displacement. Two points on the ribbon could be simultaneously illuminated, and one of the laser beams could be scanned over the ribbon. We observed quasiperiodic bifurcations in the motion of the ribbon, and characterized the spatial aspect of the motion with some recently developed statistics.

Journal Article↗
PubMed2002

Coupled-mode approach to the nonlinear dynamics induced by an elliptically polarized laser field in liquid crystals at normal incidence.

A coupled-mode theory is presented to describe the dynamics of the molecular director induced by an elliptically polarized light plane wave normally incident onto a homeotropic liquid crystal film. The model provides a set of time ordinary differential equations for the lowest two modes of the system while the influence of the higher-order twist modes is accounted for by means of the adiabatic approximation. The resulting dynamics is complex above the reorientation threshold, according to the intensity and polarization of the incident light, rotating, oscillating, or steady states may settle. The dynamical regimes have been studied as functions of external parameters. The agreement with the experimental data was very good.

Journal Article↗
PubMed2002

Nonlinear dynamics of topological solitons in DNA.

Dynamics of topological solitons describing open states in the DNA double helix are studied in the framework of a model that takes into account asymmetry of the helix. It is shown that three types of topological solitons can occur in the DNA double chain. Interaction between the solitons, their interactions with the chain inhomogeneities, and stability of the solitons with respect to thermal oscillations are investigated.

Journal Article↗
PubMed2002

Detection and classification of nonlinear dynamic switching events.

A method is proposed for detecting chaotic switching events. Switching events are classified by the time of the event and by parameter value. Classifications are based on the density of localized dynamics about a test trajectory. This method is shown to be successful in tracking short-time parameter modulation and hyperchaotic key shifting used in otherwise secure communications.

Journal Article↗
PubMed2004

Nonlinear dynamic conversion of analog signals into excitation patterns.

Local periodic perturbations induce frequency-dependent propagation waves in an excitable spatiotemporally chaotic system. We show how segments of noise-contaminated and chaotic perturbations induce characteristic sequences of excitations in the model system. Using a set of "tuned" excitable systems, it is possible to characterize signals by their spectral composition of excitation pattern. As an example, we analyze an epileptic "spike-and-wave" time series.

Journal Article↗
PubMed2005

Nonlinear dynamics of short traveling capillary-gravity waves.

We establish a Green-Nagdhi model equation for capillary-gravity waves in (2+1) dimensions. Through the derivation of an asymptotic equation governing short-wave dynamics, we show that this system possesses (1+1) traveling-wave solutions for almost all the values of the Bond number theta (the special case theta=1/3 is not studied). These waves become singular when their amplitude is larger than a threshold value, related to the velocity of the wave. The limit angle at the crest is then calculated. The stability of a wave train is also studied via a Benjamin-Feir modulational analysis.

Journal Article↗
PubMed2006

Nonlinear dynamics induced in liquid crystals in the presence of the orbital and spin angular momentum of light.

We studied the dynamical effects induced in a homeotropic nematic film when a normally incident circularly polarized light beam with an elliptical intensity profile is used. A three-dimensional dynamical model shows that, besides the spin, the orbital angular momentum of photons also plays a role in the reorientation process. Our measurements fairly reproduce the main dynamical features predicted by the model in the near threshold region. The model, however, does not work, as it is, at higher incident laser power where chaotic director rotation was reported [A. Vella, A. Setaro, B. Piccirillo, E. Santamato, Phys. Rev. E 67, 051704 (2003)].

Journal Article↗