Publications

Controlling the dynamical behavior of a circle map model of the human heart

No abstract is provided for this article.

A stability theorem for Internet congestion control

This paper proves a stability theorem for an Internet congestion control algorithm with diverse propagation delays.

Degree-distribution Stability of Evolving Networks

In this paper, we study a class of stochastic processes, called evolving network Markov chains, in evolving networks. Our approach is to transform the degree distribution problem of an evolving network to a corresponding problem of evolving network Markov chains. We investigate the evolving network Markov chains, thereby obtaining some exact formulas as well as a precise criterion for determining whether the steady degree distribution of the evolving network is a power-law or not. With this new method, we finally obtain a rigorous, exact and unified solution of the steady degree distribution of the evolving network.

Chaos-Based Encryption for Digital Image and Video

Many digital services, such as pay TV, confidential videoconferencing, and medical and military imaging systems, require reliable security in storage and transmission of digital images and videos. This chapter focuses on different image and video encryption algorithms based on chaos and aims to clarify some experiences, lessons, and principles of using chaos to design such encryption schemes. In image and video encryption systems, some features are required to support special functions of diverse multimedia services in different environments. Since the 1990s, selective encryption has been widely suggested and adopted as a basic idea for the encryption of digital images and videos, aiming to achieve a better trade-off between the encryption load and the security level. Image and video encryption plays a more and more important role in today’s multimedia world. Although many encryption schemes have been proposed to provide security for digital images and videos, some of them are too weak to resist various attacks designed by cryptanalysts.

YET ANOTHER CHAOTIC ATTRACTOR

This Letter reports the finding of a new chaotic at tractor in a simple three-dimensional autonomous system, which resembles some familiar features from both the Lorenz and Rossler at tractors.

Disconnected synchronized regions of complex dynamical networks

This paper addresses the synchronized region problem, which is reduced to a matrix stability problem, for complex dynamical networks. For any natural number $n$, the existence of a network which has $n$ disconnected synchronized regions is theoretically demonstrated. This shows the complexity in network synchronization. Convexity characteristic of stability for matrix pencils is further discussed. Smooth and generalized smooth Chua's circuit networks are finally discussed as examples for illustration.

A SIMPLE SMOOTH CHAOTIC SYSTEM WITH A 3-LAYER ATTRACTOR

This Letter reports a simple smooth quadratic autonomous chaotic system with four unstable equilibrium points and three homoclinic orbits, and can display a 3-layer attractor among some others. It is the first example of a simple smooth quadratic system that we know, which can exhibit Šhilnikov chaos without numerical evidence of a route to chaos through period-doubling bifurcations.

Decoupling of Filtering Equations

No abstract is provided for this article.

Frequency-Domain Approach to Hopf Bifurcation Analysis

No abstract is provided for this article.

On the security defects of an image encryption scheme.

This paper studies the security of a recently-proposed chaos-based image encryption scheme, and points out the following problems: 1) there exist a number of invalid keys and weak keys, and some keys are partially equivalent for encryption/decryption; 2) given one chosen plain-image, a subkey K10 can be guessed with a smaller computational complexity than that of the simple brute-force attack; 3) given at most 128 chosen plain-images, a chosen-plaintext attack can possibly break the following part of the secret key: fKi mod 128g 10=4 , which works very well when K10 is not too large; 4) when K10 is relatively small, a known-plaintext attack can be carried out with only one known plain-image to recover some visual information of any other plain-images encrypted by the same key.

Formation control of networked multi-agent systems

In this study, a systematic framework is developed for the consensus control problem, particularly for formation control of networked dynamic agents. In view of the complexity of the framework with switching coupling topology and non-linearity, a new decentralised formation strategy based on artificial potential functions (APF) is proposed. Owing to the existence of local minima in the APF, the formation controller is designed to introduce some special functions to settle that limitation. A new concept of relative-position-based formation stability is defined, and a Lyapunov approach is used along with an extended linear matrix inequalities (LMI) algorithm to analyse the condition for formation stability. Finally, an example with simulations is provided to demonstrate the effectiveness of the designed formation controller.

Modelling the Complex Internet Topology

No abstract is provided for this article.

ON FEEDBACK CONTROL OF CHAOTIC NONLINEAR DYNAMIC SYSTEMS

In this paper, some interesting analysis and simulations on the control of chaotic dynamic systems using conventional feedback control strategies are presented. The typical discrete-time chaotic Lozi system is investigated in some detail. The trajectories of the chaotic Lozi system are controlled to its equilibrium points using conventional feedback controls. Analysis on the design of the feedback controllers and its computer simulations are included.

Minimizing Spectral Radius of Non-Backtracking Matrix by Edge Removal

The spectral radius of the non-backtracking matrix for an undirected graph plays an important role in various dynamic processes running on the graph. For example, its reciprocal provides an excellent approximation of epidemic and edge percolation thresholds. In this paper, we study the problem of minimizing the spectral radius of the non-backtracking matrix of a graph with n nodes and m edges, by deleting k selected edges. We show that the objective function of this combinatorial optimization problem is not submodular, although it is monotone. Since any straightforward approach to solving the optimization problem is computationally infeasible, we present an effective, scalable approximation algorithm with complexity O (n+km). Extensive experiment results for a large set of real-world networks verify the effectiveness and efficiency of our algorithm, and demonstrate that our algorithm outperforms several baseline schemes.

Model-Based Optimal Control

No abstract is provided for this article.

Effect of different antihypertensive programs on blood pressure and left ventricular hypertrophy in elderly patients with hypertension

Objective To discuss the effect of different antihypertensive programs on blood pressure and left ven-tricular hypertrophy of elderly patients with hypertension, and to provide a guidance for clinical practice. Methods A total of 162 patients with hypertension in Department of Internal Medicine in our hospital were selected from December 2012 to December 2014, and randomly divided into the observation group and the control group according to random number table, with 81 patients in each group. The observation group was treated by amlodipine combined with hydrochlorothi-azide, and the control group was treated with amlodipine combined with irbesartan, for a treatment course of two mouths. The blood pressure, left ventricular mass index (LVMI), after treatment were compared between the two groups. Results Among the 162 patients, eight patients were lost to follow-up. After treatment, the systolic blood pres-sure of patients in observation group and the control group was (123 ± 6) mmHg, (129 ± 8) mmHg, respectively, which were significantly decreased compared with those before treatment [(157 ± 12) mmHg, (156 ± 9) mmHg], and the value was significantly lower in observation group than control group (P<0.05). After treatment, the degree of LVMI were sig-nificantly reduced compared with before treatment, and the LVMI in observation group was significantly lower than that in the control group [(124±18) g/m2 vs (132±16) g/m2, P<0.05]. Conclusion Amlodipine combined with irbesartan and amlodipine combined with hydrochlorothiazide can both reduce blood pressure and LVMI of patients. However, the treat-ment effect of amlodipine combined with hydrochlorothiazide is more significant, which is worthy of clinical populariza-tion and application.

Robust adaptive synchronization of uncertain dynamical networks

This Letter studies local and global robust adaptive synchronizations in uncertain dynamical networks. For complex dynamical networks with unknown but bounded nonlinear couplings, with known or unknown bounds, some robust adaptive controllers are designed in this Letter, which can ensure that the state of a dynamical network locally or globally asymptotically synchronize with an arbitrarily assigned state of an isolate node of the network. The Letter also investigates the synchronization problem where the dynamics of the coupled states are different from that of the uncoupled states. The key idea is to suitably combine the Lyapunov stability theory with a good update law for estimating the unknown network coupling parameters in the design of the controllers. Two examples are simulated, using the smooth chaotic Chen system and the piecewise-continuous chaotic Chua circuit, respectively, as the nodes of the dynamical network, which demonstrate the effectiveness of the proposed controllers design methods.

Nonlinear TiC nanosheets for MIR Q-switched laser in Er:GYAP cavity