Publications

In this paper a new architecture for digital image stabilizer (DIS) is presented. The system utilizes a matching algorithm on the Gray-coded bit-plane of the video sequence, which greatly reduces the complexity and enables the real-time processing capability in its motion estimating mechanism. According to the algorithm, a flexible system architecture containing software and hardware blocks is proposed. The proposed design is computationally efficient and is thus well suited as a low-cost solution for DIS in camcorders. In practice, the system has been validated on a mixed FPGA/DSP-based prototype.

This article offers an overview on some commonly concerned issues related to control and anticontrol of chaos. Similar to conventional systems control, the concept of controlling chaos is first to mean suppressing chaos in the sense of stabilising chaotic system responses. The process of chaos control is now understood as a transition between chaos and order and, sometimes, from chaos to chaos, depending on the application of interest. Anticontrol of chaos, in contrast to the main stream of ordering or suppressing chaos, is to make a nonchaotic dynamical system chaotic, or to retain/enhance the existing chaos of a complex system. Anticontrol of chaos has emerged as a theoretically attractive and potentially useful new subject in system control theory and time critical or energy-critical high-performance applications.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Frequency-modulated differential chaos shift keying (FM-DCSK) ultrawideband (UWB) communication systems convey information by transmitting ultrashort chaotic pulses (in the nanosecond scale). Since such pulses are ultrashort, timing offset may severely degrade the bit error rate (BER) performance. In this paper, a fast data-aided timing synchronization algorithm with low complexity is proposed for FM-DCSK UWB systems, which capitalizes on the excellent correlation characteristic of chaotic signals. Simulation results show that the BER performance of such systems is fairly close to that of perfect timing thanks to the proposed new algorithm. Moreover, the new algorithm requires less synchronization searching time and lower computational complexity than the conventional one for transmitted reference UWB systems existing in the current literature. </para>

In this paper, a new memristor-based chaotic system is designed, analyzed, and implemented. Multistability, multiple attractors, and complex riddled basins are observed from the system, which are investigated along with other dynamical behaviors such as equilibrium points and their stabilities, symmetrical bifurcation diagrams, and sustained chaotic states. With different sets of system parameters, the system can also generate various multi-scroll attractors. Finally, the system is realized by experimental circuits.

This paper studies chaos synchronization between two coupled chaotic systems using linear state feedback control. A new, simple and yet easily applicable criterion is derived for chaos synchronization based on the Lyapunov stability theory and the Linear Quadratic Optimal Control theory. This criterion is given in terms of some simple algebraic inequalities established by the Gerschgorin theorem, and it is easily applicable to a large class of chaotic systems. As an example, the familiar Chua's circuit is simulated for demonstration.

No abstract is provided for this article.

In this Letter, we prove that the algorithm of Chen and Lai [1996, 1997, 1998] for the anticontrol of chaos leads to chaos not only in the sense of Devaney but also in the sense of Li and Yorke, for both linear and nonlinear autonomous systems of any dimensionalities.

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.

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.

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.

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.

We address the problem as if the initial function space of a time-delayed system can be finite-dimensional. We argue that the dimension of the initial function space of a time-delayed feedback control system is just identical to that of the corresponding plant which is to be controlled, and so is finite-dimensional in many cases. We prove this property by constructing an injection map between the two spaces. We anticipate that this may also be applied to some other systems, such as ecological processes involving time delays without control. We believe that the significance of this discovery not only makes available the physical interpretation and intuitional explanation of the basins of attraction associated with time-delayed feedback control, but also suggests the principle as how to evaluate the robustness of the time-delayed feedback control schemes to external disturbances. We finally visualize and illustrate such basins of attraction via numerical simulation for the classical Duffing system by equipping it with the velocity time-delayed feedback control.

We present a memory-based snowdrift game (MBSG) taking place on networks. We found that, when a lattice is taken to be the underlying structure, the transition of spatial patterns at some critical values of the payoff parameter is observable for both four- and eight-neighbor lattices. The transition points as well as the styles of spatial patterns can be explained by local stability analysis. In sharp contrast to previously reported results, cooperation is promoted by the spatial structure in the MBSG. Interestingly, we found that the frequency of cooperation of the MBSG on a scale-free network peaks at a specific value of the payoff parameter. This phenomenon indicates that properly encouraging selfish behaviors can optimally enhance the cooperation. The memory effects of individuals are discussed in detail and some nonmonotonous phenomena are observed on both lattices and scale-free networks. Our work may shed some new light on the study of evolutionary games over networks.