7,150 research outputs found
An Empirical Argument for Nontechnical Public Members on Advisory Committees: FDA As a Model
A discussion of the results of two surveys of present and past members of Food and Drug Administration Advisory Committees. The views and understanding of the issues before various categories of membership are compared and contrasted. It appears that technical members of advisory committees would generally welcome more participation by persons who lack special subject matter expertise
Different routes to chaos via strange nonchaotic attractor in a quasiperiodically forced system
This paper focusses attention on the strange nonchaotic attractors (SNA) of a
quasiperiodically forced dynamical system. Several routes, including the
standard ones by which the appearance of strange nonchaotic attractors takes
place, are shown to be realizable in the same model over a two parameters
() domain of the system. In particular, the transition through
torus doubling to chaos via SNA, torus breaking to chaos via SNA and period
doubling bifurcations of fractal torus are demonstrated with the aid of the two
parameter () phase diagram. More interestingly, in order to
approach the strange nonchaotic attractor, the existence of several new
bifurcations on the torus corresponding to the novel phenomenon of torus
bubbling are described. Particularly, we point out the new routes to chaos,
namely, (1) two frequency quasiperiodicity torus doubling torus
merging followed by the gradual fractalization of torus to chaos, (2) two
frequency quasiperiodicity torus doubling wrinkling SNA
chaos SNA wrinkling inverse torus doubling torus
torus bubbles followed by the onset of torus breaking to chaos via SNA or
followed by the onset of torus doubling route to chaos via SNA. The existence
of the strange nonchaotic attractor is confirmed by calculating several
characterizing quantities such as Lyapunov exponents, winding numbers, power
spectral measures and dimensions. The mechanism behind the various bifurcations
are also briefly discussed.Comment: 12 pages, 12 figures, ReVTeX (to appear in Phys. Rev. E
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]
Estimation of System Parameters in Discrete Dynamical Systems from Time Series
We propose a simple method to estimate the parameters involved in discrete
dynamical systems from time series. The method is based on the concept of
controlling chaos by constant feedback. The major advantages of the method are
that it needs a minimal number of time series data and is applicable to
dynamical systems of any dimension. The method also works extremely well even
in the presence of noise in the time series. The method is specifically
illustrated by means of logistic and Henon maps.Comment: 4 page
Effect of Phase Shift in Shape Changing Collision of Solitons in Coupled Nonlinear Schroedinger Equations
Soliton interactions in systems modelled by coupled nonlinear Schroedinger
(CNLS) equations and encountered in phenomena such as wave propagation in
optical fibers and photorefractive media possess unusual features : shape
changing intensity redistributions, amplitude dependent phase shifts and
relative separation distances. We demonstrate these properties in the case of
integrable 2-CNLS equations. As a simple example, we consider the stationary
two-soliton solution which is equivalent to the so-called partially coherent
soliton (PCS) solution discussed much in the recent literature.Comment: 11 pages, revtex4,Two eps figures. European Journal of Physics B (to
appear
Secure Communication using Compound Signal from Generalized Synchronizable Chaotic Systems
By considering generalized synchronizable chaotic systems, the
drive-auxiliary system variables are combined suitably using encryption key
functions to obtain a compound chaotic signal. An appropriate feedback loop is
constructed in the response-auxiliary system to achieve synchronization among
the variables of the drive-auxiliary and response-auxiliary systems. We apply
this approach to transmit analog and digital information signals in which the
quality of the recovered signal is higher and the encoding is more secure.Comment: 7 pages (7 figures) RevTeX, Please e-mail Lakshmanan for figures,
submitted to Phys. Lett. A (E-mail: [email protected]
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