Publications

Hopf bifurcation and chaos analysis of Chen’s system with distributed delays

In this paper, a general model of nonlinear systems with distributed delays is studied. Chen’s system can be derived from this model with the weak kernel. After the local stability is analyzed by using the Routh–Hurwitz criterion, Hopf bifurcation is studied, where the direction and the stability of the bifurcating periodic solutions are determined by using the normal form theory and the center manifold theorem. Some numerical simulations for justifying the theoretical analysis are also presented. Chaotic behavior of Chen’s system with the strong kernel is also found through numerical simulation, in which some waveform diagrams, phase portraits, and bifurcation plots are presented and analyzed.

Revisiting type-2 triangular norms on normal convex fuzzy truth values

This paper studies t-norms on the space L of all normal and convex fuzzy truth values. We first prove that the only non-convolution form type-2 t-norm constructed by Wu et al. satisfies the distributivity law for meet-convolution and show that t-norm in the sense of Walker and Walker is strictly stronger than t r -norm on L, which is strictly stronger than t-norm on L. Furthermore, we characterize some restrictive axioms of t r -norms for convolution operations on L and obtain some necessary conditions for t r -(co)norm convolution operations on L.

MAXIMUM SYNCHRONIZABILITY OF GENERAL TIME-INVARIANT DYNAMICAL NETWORKS

This paper shows that the maximum synchronizability of a general time-invariant dynamical network is completely determined by its associated internal feedback dynamics, which has a precise physical meaning in terms of synchronous communication. Also, a concept of synchronizability matrix is introduced to characterize the robustness of synchronization of the network. Based on the knowledge of synchronizability, we can purposefully increase the robustness of the network synchronization and better prevent it from attacks.

Controlling Halo-Chaos via Variable Structure Method

We propose a variable structure control method which is another innovative technique for suppressing beam halo-chaos in the periodic focusing channels of high-current proton beam accelerator, which belongs to a high-tech field. The analysis and numerical results show that the method is effective for controlling beam halo-chaos. Physical implementation of such a kind of control strategy remains an important and open issue for further applications.

Quasi-synchronization of heterogeneous dynamic networks via distributed impulsive control: Error estimation, optimization and design

This paper studies leader–follower synchronization in heterogeneous dynamic networks via distributed impulsive control. The goal is to drive the followers to approximately synchronize with the leader within a nonzero error bound, referred to as quasi-synchronization. Some fundamental and yet challenging problems are addressed : (1) How to obtain a tight quasi-synchronization error bound; (2) How many and which nodes should be controlled; (3) How to design the coupling strength, to select the pinned nodes and to determine the impulse intervals to optimize the error bound or to achieve quasi-synchronization within a prescribed error bound. First, some general quasi-synchronization conditions are derived with explicit expressions of the error bound. Second, the pinning strategy and the coupling strength in achieving quasi-synchronization are explored and expressed in term of impulse intervals. It is interesting to find that a large coupling strength will destroy synchrony, in contrast to continuous pinning control. Furthermore, the common requirement that the leader has a directed path to every node is needed only in the case that the impulse intervals can be arbitrarily small. A new concept, referred to as impulse pinning controllability, is introduced to the case that impulses cannot take place too frequently. Third, an optimization of the error bound is discussed and formulated. Under a prescribed error bound, the design problem of the coupling strength, pinned nodes and impulse intervals is solved. Finally, three examples are given to verify the theoretical results.

Analysis of a new chaotic system

This paper reports a new three-dimensional continuous quadratic autonomous chaotic system, modified from the Lorenz system, in which each equation contains a single quadratic cross-product term, which is different from the Lorenz, Rössler, Chen, Lü systems. Basic properties of the new system are analyzed by means of Lyapunov exponent spectrum and bifurcation diagrams. Analysis results show that this system has complex dynamics with some interesting characteristics.

A Talk About Systems and Networks

This is an essay to present some personal views onsystemsandnetworkswith respect to their similarities and differences as well as their relationships.

Linear time-delay feedback control of a pathological rhythm in a cardiac conduction model

This paper describes a method based on one-step linear time-delay feedback (LTDF) for suppressing a pathological period-2 rhythm (cardiac alternans) in an atrioventricular nodal conduction model. The LTDF controller is effective at suppressing alternans by stabilizing the map to one of a set of unstable fixed points. Additionally, we show that alternans can be prevented by tracking the period-1 rhythm past the point where bifurcation occurs, and that the method is robust to both measurement error and experimental noise. Finally, we demonstrate that this method is simpler to implement and more effective than the OGY chaos control method which was used recently to stabilize the same system.

Simplified Memristive Lorenz Oscillator

Memristor can be designed based on the topological structure of a dynamical system. Lorenz system provides such a structure for memristor building, in which one of the system variables can be regarded as the internal variable of the mathematical model. Based on the strong load capacity of AD633, two such capacitors are coupled directly to construct a simplified chaotic circuit. The memristor parameter can rescale the amplitudes of the system variables directly. Although the memristive Lorenz system has similar properties of bifurcation and multistability to the original one, it shows more opportunities for memristor-based information processing.

Learning First-Order Logic Rules for Argumentation Mining

Yang Sun, Guanrong Chen, Hamid Alinejad-Rokny, Jianzhu Bao, Yuqi Huang, Bin Liang, Kam-Fai Wong, Min Yang, Ruifeng Xu. Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). 2025.

Cyclic subway networks are less risky in metropolises

Subways are crucial in modern transportation systems of metropolises. To quantitatively evaluate the potential risks of subway networks suffered from natural disasters or deliberate attacks, real data from seven Chinese subway systems are collected and their population distributions and anti-risk capabilities are analyzed. Counterintuitively, it is found that transfer stations with large numbers of connections are not the most crucial, but the stations and lines with large betweenness centrality are essential, if subway networks are being attacked. It is also found that cycles reduce such correlations due to the existence of alternative paths. To simulate the data-based observations, a network model is proposed to characterize the dynamics of subway systems under various intensities of attacks on stations and lines. This study sheds some light onto risk assessment of subway networks in metropolitan cities.

L2 norm performance index of synchronization and optimal control synthesis of complex networks

In this paper, the synchronizability problem of dynamical networks is addressed, where better synchronizability means that the network synchronizes faster with lower-overshoot. The L2 norm of the error vector e is taken as a performance index to measure this kind of synchronizability. For the equilibrium synchronization case, it is shown that there is a close relationship between the L2 norm of the error vector e and the H2 norm of the transfer function G of the linearized network about the equilibrium point. Consequently, the effect of the network coupling topology on the H2 norm of the transfer function G is analyzed. Finally, an optimal controller is designed, according to the so-called LQR problem in modern control theory, which can drive the whole network to its equilibrium point and meanwhile minimize the L2 norm of the output of the linearized network.

A Distributed Finite-Time Consensus Algorithm for Higher-Order Leaderless and Leader-Following Multiagent Systems

By employing the finite-time control method, the consensus control algorithm for higher-order multiagent systems is designed in this paper. Under a neighbor-based rule, a higher-order finite-time consensus algorithm is explicitly constructed, which only uses local information. The finite-time consensus control algorithm can guarantee that the state consensus is achieved in a finite time. In addition, for multiagent systems having a leader-following structure, the consensus algorithm is also designed. Finally, two examples are presented to show the effectiveness.

Chaos stabilization: an inverse optimal control approach

Locating unstable periodic orbits: When adaptation integrates into delayed feedback control

Finding unstable periodic orbits (UPOs) is always a challenging demand in biophysics and computational biology, which needs efficient algorithms. To meet this need, an approach to locating unstable periodic orbits in chaotic dynamical system is presented. The uniqueness of the approach lies in the introduction of adaptive rules for both feedback gain and time delay in the system without requiring any information of the targeted UPO periods a priori. This approach is theoretically validated under some mild conditions and successfully tested with some practical strategies in several typical chaotic systems with or without significant time delays.

Cryptanalysis of two chaotic encryption schemes based on circular bit shift and XOR operations

Recently two encryption schemes were proposed by combining circular bit shift and XOR operations, under the control of a pseudorandom bit sequence (PRBS) generated from a chaotic system. This Letter studies the security of these two encryption schemes and reports the following findings: (1) there exist some security defects in both schemes; (2) the underlying chaotic PRBS can be reconstructed as an equivalent key by using only two chosen plaintexts; (3) most elements in the underlying chaotic PRBS can be obtained by a differential known-plaintext attack using only two known plaintexts. Experimental results are given to demonstrate the feasibility of the proposed attack.

Discrete chaos in Banach spaces

No abstract is provided for this article.

Generating multi-folded torus chaotic attractors

A systematic methodology for generating multi-folded torus chaotic attractors from a simple three-dimensional piecewise-linear system is presented in this paper. Theoretical analysis shows that multi-folded torus chaotic attractors can be created via alternative switching between two piecewise-linear systems. A novel circuit diagram is designed for physically creating multi-folded torus chaotic attractors. This is the first time in the literature to experimentally verify a maximum 9-folded torus chaotic attractor that is generated by an analog circuit.