a watermarking scheme for Grayscale image isproposed based on a family of the chaotic maps and discretecosine transform. Jacobian Elliptic mapis employed to encrypt ofwatermarked logo. Piecewise nonlinear chaotic map is also usedto determine the location of DCT coefficients for the watermarkembedding. The purpose of this algorithm is to improve theshortcoming of watermarking such as small key s...

a watermarking scheme for grayscale image isproposed based on a family of the chaotic maps and discretecosine transform. jacobian elliptic mapis employed to encrypt ofwatermarked logo. piecewise nonlinear chaotic map is also usedto determine the location of dct coefficients for the watermarkembedding. the purpose of this algorithm is to improve theshortcoming of watermarking such as small key s...

Motivated by conventional gauge theories, we consider a theory of gravity in which the Einstein–Hilbert action is replaced by a term that is quadratic in the Riemann tensor. We focus on cosmological solutions to the field equations in flat, open and closed universes. The gravitational action is scale invariant, so the only matter source considered is radiation. The theory can also accommodate i...

This paper introduces a new technique for intelligently exploring the reachability set of a spacecraft: the set of trajectories from a given initial condition that are possible under a specified range of control actions. The high dimension of this problem and the nonlinear nature of gravitational interactions make the geometry of these sets complicated, hard to compute, and all but impossible t...

Energy estimates show that linearized thermo-elasticity deenes a contraction semi-group on a Hilbert space. We show that under a geometric condition this contraction is not strict, or, more precisely, the norm of the semi group is 1 for all t 0. Convex domains always satisfy the geometric condition. 2. introduction Let R n be a bounded domain with smooth boundary ?. We consider the problem @ 2 ...

We present an efficient computational procedure for finite abstraction of discrete-time mixed monotone systems by considering a rectangular partition of the state space. Mixed monotone systems are decomposable into increasing and decreasing components, and significantly generalize the well known class of monotone systems. We tightly overapproximate the one-step reachable set from a box of initi...

In this paper, we present a sampling-based verification algorithm for continuous dynamic systems with uncertainty due to adversaries, unmodeled disturbance inputs, unknown parameters, or initial conditions. The algorithm attempts to find inputs (and resulting trajectories) that falsify the specifications of the system thus providing examples of bad inputs to the system. The system is said to be...

We use feedback control methods to prove existence of globally asymptotically stable equilibria for nonlinear (density dependent) population dynamics. We focus on populations modelled in discrete size or stage classes so that the model has a natural state space of nonnegative vectors in R. Combining comparison results and small gain techniques, we characterize the situations when there is a pos...