2,312 publications from this institution
Beam halo-chaos is essentially a complex spatiotemporal chaotic motion in a periodic-focusing channel of a high-power linear proton accelerator. The controllability condition for beam halo-chaos is analysed qualitatively. A special nonlinear control method, i.e. the wavelet-based function feedback, is proposed for controlling beam halo-chaos. Particle-in-cell simulations are used to explore the nature of halo-chaos formation, which has shown that the beam halo-chaos is suppressed effectively after using nonlinear control for the proton beam with an initial full Gaussian distribution. The halo intensity factor Hav is reduced from 14% to zero, and the other statistical physical quantities of beam halo-chaos are more than doubly reduced. The potential applications of such nonlinear control in experiments are briefly pointed out.
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.
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.
In this paper, a methodology for the synchronization of two chaotic systems by means of a sampled driving signal is presented. The method is based on the fuzzy Takagi-Sugeno representation of the chaotic system, from which a continuous-time fuzzy observer is designed as the solution of an LMI problem. Then, via the dual-system, the fuzzy observer is digitally redesigned such that the performance is maintained for the sampled system. Numerical simulations of Chua's circuit are used to illustrate the effectiveness of the proposed synchronization methodology.
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.
No abstract is provided for this article.
A new method is developed for controlling chaos in discrete systems by perturbing one of its parameters in the neighborhood of an unstable periodic orbit (UPO). For 2-D systems, only two changes in the parameter value are needed in order to stabilize a UPO embedded in the chaotic attractor. The method is general and can be applied to any discrete chaotic system, in which a parameter is accessible and can be changed around a nominal value. To validate and visualize the applicability of the method, an electronic circuit is designed, which resembles the dynamics of the Hénon system, and the control scheme is successfully tested on this circuit. The experimental results show good performance of the method in the presence of noise in the signals, uncertainties in the model, and disturbances in the real circuit system.
Encryption of images is different from that of texts due to some intrinsic features of images such as bulk data capacity and high redundancy, which are generally difficult to handle by traditional methods. Due to the exceptionally desirable properties of mixing and sensitivity to initial conditions and parameters of chaotic maps, chaos-based encryption has suggested a new and efficient way to deal with the intractable problem of fast and highly secure image encryption. In this paper, the two-dimensional chaotic cat map is generalized to 3D for designing a real-time secure symmetric encryption scheme. This new scheme employs the 3D cat map to shuffle the positions (and, if desired, grey values as well) of image pixels and uses another chaotic map to confuse the relationship between the cipher-image and the plain-image, thereby significantly increasing the resistance to statistical and differential attacks. Thorough experimental tests are carried out with detailed analysis, demonstrating the high security and fast encryption speed of the new scheme.
For a Hertz chain model, by using the methodology of dynamical systems and singular traveling wave theory developed by Li and Chen [9] to its traveling wave system defined on a two-dimensional foliations in the three-dimensional space, under different parameter conditions, the existence of all possible bounded solutions (solitary wave solutions, periodic wave solutions, periodic peakons, and compactons) is proved. For the nonlinearity exponent $ k = \frac32, k = 2 $ and $ k = 3 $ in the model, as many as 23 exact explicit parametric representations of the above-mentioned traveling wave system are obtained.
This paper presents a comprehensive analysis on the security of the Yi-Tan-Siew chaotic cipher proposed in [IEEE TCAS-I 49(12):1826-1829 (2002)]. A differential chosen-plaintext attack and a differential chosen-ciphertext attack are suggested to break the sub-key K, under the assumption that the time stamp can be altered by the attacker, which is reasonable in such attacks. Also, some security Problems about the sub-keys $α$ and $β$ are clarified, from both theoretical and experimental points of view. Further analysis shows that the security of this cipher is independent of the use of the chaotic tent map, once the sub-key $K$ is removed via the proposed suggested differential chosen-plaintext attack.
