982 research outputs found
Prediction-error of Prediction Error (PPE)-based Reversible Data Hiding
This paper presents a novel reversible data hiding (RDH) algorithm for
gray-scaled images, in which the prediction-error of prediction error (PPE) of
a pixel is used to carry the secret data. In the proposed method, the pixels to
be embedded are firstly predicted with their neighboring pixels to obtain the
corresponding prediction errors (PEs). Then, by exploiting the PEs of the
neighboring pixels, the prediction of the PEs of the pixels can be determined.
And, a sorting technique based on the local complexity of a pixel is used to
collect the PPEs to generate an ordered PPE sequence so that, smaller PPEs will
be processed first for data embedding. By reversibly shifting the PPE histogram
(PPEH) with optimized parameters, the pixels corresponding to the altered PPEH
bins can be finally modified to carry the secret data. Experimental results
have implied that the proposed method can benefit from the prediction procedure
of the PEs, sorting technique as well as parameters selection, and therefore
outperform some state-of-the-art works in terms of payload-distortion
performance when applied to different images.Comment: There has no technical difference to previous versions, but rather
some minor word corrections. A 2-page summary of this paper was accepted by
ACM IH&MMSec'16 "Ongoing work session". My homepage: hzwu.github.i
Backstepping controller design for a class of stochastic nonlinear systems with Markovian switching
A more general class of stochastic nonlinear systems with irreducible homogenous Markovian switching are considered in this paper. As preliminaries, the stability criteria and the existence theorem of strong solutions are first presented by using the inequality of mathematic expectation of a Lyapunov function. The state-feedback controller is designed by regarding Markovian switching as constant such that the closed-loop system has a unique solution, and the equilibrium is asymptotically stable in probability in the large. The output-feedback controller is designed based on a quadratic-plus-quartic-form Lyapunov function such that the closed-loop system has a unique solution with the equilibrium being asymptotically stable in probability in the large in the unbiased case and has a unique bounded-in-probability solution in the biased case
Extreme Spontaneous Deformations of Active Crystals
We demonstrate that two-dimensional crystals made of active particles can
experience extremely large spontaneous deformations without melting. Using
particles mostly interacting via pairwise repulsive forces, we show that such
active crystals maintain long-range bond order and algebraically-decaying
positional order, but with an exponent not limited by the
bound given by the (equilibrium) KTHNY theory. We rationalize our findings
using linear elastic theory and show the existence of two well-defined
effective temperatures quantifying respectively large-scale deformations and
bond-order fluctuations. The root of these phenomena lies in the sole
time-persistence of the intrinsic axes of particles, and they should thus be
observed in many different situations.Comment: 6 pages, 4 figure
Effects of polymer additives in the bulk of turbulent thermal convection
We present experimental evidence that a minute amount of polymer additives
can significantly enhance heat transport in the bulk region of turbulent
thermal convection. The effects of polymer additives are found to be the
\textit{suppression} of turbulent background fluctuations that give rise to
incoherent heat fluxes that make no net contribution to heat transport, and at
the same time to \textit{increase} the coherency of temperature and velocity
fields. The suppression of small-scale turbulent fluctuations leads to more
coherent thermal plumes that result in the heat transport enhancement. The fact
that polymer additives can increase the coherency of thermal plumes is
supported by the measurements of a number of local quantities, such as the
extracted plume amplitude and width, the velocity autocorrelation functions and
the velocity-temperature cross-correlation coefficient. The results from local
measurements also suggest the existence of a threshold value for the polymer
concentration, only above which can significant modification of the plume
coherent properties and enhancement of the local heat flux be observed.
Estimation of the plume emission rate suggests that the second effect of
polymer additives is to stabilize the thermal boundary layers.Comment: 8 figures, 11 page
Dynamical Sub-classes of Dry Active Nematics
We show that the dominant mode of alignment plays an important role in dry
active nematics,leading to two dynamical sub-classes defined by the nature of
the instability of the nematic bands that characterize, in these systems, the
coexistence phase separating the isotropic and fluctuating nematic states. In
addition to the well-known instability inducing long undulations along the
band, another stronger instability leading to the break-up of the band in many
transversal segments may arise. We elucidate the origin of this strong
instability for a realistic model of self-propelled rods and determine the
high-order nonlinear terms responsible for it at the hydrodynamic level.Comment: 5 pages, 4 figures. Supplementary and movies are available upon
reques
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