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Qin C.,Shanghai Key Laboratory of Modern Optical Systems | Zhang X.,Shanghai University
Journal of Visual Communication and Image Representation | Year: 2015

In this paper, we propose a novel reversible data hiding scheme in encrypted image. The content owner encrypts the original image with the encryption key to achieve privacy protection for image content, and then, each block of the encrypted image is embedded with one secret bit by the data hider using the data-hiding key. Through the elaborate selection for partial pixels to be flipped, data hiding process only conducts slighter modifications to each block, which leads to significant improvement of visual quality for the decrypted image. The receiver can easily decrypt the marked, encrypted image using the encryption key, and then, through the data-hiding key and an adaptive evaluation function of smoothness characteristic along the isophote direction, secret data can be extracted from the decrypted image, and the original image can further be recovered successfully. Experimental results demonstrate the effectiveness of the proposed scheme. © 2015 Elsevier Inc. All rights reserved. Source

Ding D.,Shanghai Key Laboratory of Modern Optical Systems | Wang Z.,Brunel University | Shen B.,Donghua University | Dong H.,Northeast Petroleum University
Automatica | Year: 2015

In this paper, the envelope-constrained H∗ filtering problem is investigated for a class of discrete time-varying stochastic systems over a finite horizon. The system under consideration involves fading measurements, randomly occurring nonlinearities (RONs) and mixed (multiplicative and additive) noises. A novel envelope-constrained performance criterion is proposed to better quantify the transient dynamics of the filtering error process over the finite horizon. The purpose of the problem addressed is to design a time-varying filter such that both the H∗ performance and the desired envelope constraints are achieved at each time step. By utilizing the stochastic analysis techniques combined with the ellipsoid description on the estimation errors, sufficient conditions are established in the form of recursive matrix inequalities (RMIs) reflecting both the envelope information and the desired H∗ performance index. The filter gain matrix is characterized by means of the solvability of the deduced RMIs. Finally, a simulation example is provided to show the effectiveness of the proposed filtering design scheme. © 2015 Elsevier Ltd. Source

Wang L.,Shanghai Key Laboratory of Modern Optical Systems | Wei G.,Shanghai Key Laboratory of Modern Optical Systems | Shu H.,Donghua University
Neurocomputing | Year: 2013

In this paper, the H∞ state estimation problem is investigated for a class of discrete-time complex networks with randomly occurring phenomena. The proposed randomly occurring phenomena include both probabilistic missing measurements and randomly occurring coupling delays which are described by two random variable sequences satisfying individual probability distributions, respectively. Rather than the common Lipschitz-type function, a more general sector-like nonlinear function is employed to characterize the nonlinearities in the networks. The purpose of the addressed H∞ state estimation problem is to design a state estimator such that, for all admissible nonlinear disturbances, missing measurements as well as coupling delays, the dynamics of the augmented systems is guaranteed to be exponentially mean-square stable and attenuated to a given H∞ performance level. By constructing a novel Lyapunov-Krasovskii functional and utilizing convex optimization method as well as Kronecker product, we derive the sufficient conditions under which the desired state estimator exists. An illustrative example is exploited to show the effectiveness of the proposed state estimation scheme. © 2013 Elsevier B.V. Source

Ding D.,Shanghai Key Laboratory of Modern Optical Systems | Wang Z.,Brunel University | Shen B.,Donghua University | Wei G.,Shanghai Key Laboratory of Modern Optical Systems
Automatica | Year: 2015

This paper is concerned with the event-triggered consensus control problem for a class of discrete-time stochastic multi-agent systems with state-dependent noises. A novel definition of consensus in probability is proposed to better describe the dynamics of the consensus process of the addressed stochastic multi-agent systems. The measurement output available for the controller is not only from the individual agent but also from its neighboring ones according to the given topology. An event-triggered mechanism is adopted with hope to reduce the communication burden, where the control input on each agent is updated only when a certain triggering condition is violated. The purpose of the problem under consideration is to design both the output feedback controller and the threshold of the triggering condition such that the closed-loop system achieves the desired consensus in probability. First of all, a theoretical framework is established for analyzing the so-called input-to-state stability in probability (ISSiP) for general discrete-time nonlinear stochastic systems. Within such a theoretical framework, some sufficient conditions on event-triggered control protocol are derived under which the consensus in probability is reached. Furthermore, both the controller parameter and the triggering threshold are obtained in terms of the solution to certain matrix inequalities involving the topology information and the desired consensus probability. Finally, a simulation example is utilized to illustrate the usefulness of the proposed control protocol. © 2015 Elsevier Ltd. Source

Fang L.,Shanghai Key Laboratory of Modern Optical Systems | Jia H.,Shanghai Key Laboratory of Modern Optical Systems
Optics Communications | Year: 2014

Coupling characteristics of core higher-order modes LP0m with optical fiber gratings written in step-index multimode fiber (MMF) and their application in mode-division multiplexing (MDM) transmission are presented and analyzed in this article. Several long-period fiber gratings (LPFGs) cascaded in one MMF can realize conversion between any two core modes, HE1m (m=1,2,3,.,6) in other words and scalar mode LP0m, in mode order from low to high. These eigenmodes supported in fiber as independent data channels are theoretically proposed to be multiplexed in one MMF by the combination of LPFGs and fiber Bragg gratings (FBGs) united with optical circulators as both multiplexers and de-multiplexers. This method of flexible mode conversion using optical gratings can be practically significant on fiber communication as a mode-selective converter. © 2014 Elsevier B.V. Source

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