Papers by Keyword: Chaos

Abstract: Due to the complexity of wind power system, it would make chaotic phenomenon which had existed in power system, a typical nonlinear system,receive more attentions. With its own characteristics, causes and hazards of chaos, it is determined to be valuable in research. At present, the wind power system chaotic phenomenon has become another popular direction in the study of wind power system. Its significance and prospect can be very large.

Abstract: A challenging task in wireless sensor network (WSN) is to deliver authentic data between source nodes and sink nodes. The collision or dead lock occurs when two or more close nodes are attempted to send data at the same time to the others node. To avoid such dead lock situation in the network we propose a nonlinear mathematical model. The effect of nonlinearity often renders a periodic solution unstable for certain parametric choices even a very small change in initial conditions can lead to different result in chaotic systems which appears to exhibit chaos for a range of parametric values when long time behavior studied. The local stability conditions for the system have been discussed and analyzed. Numerically simulations have been carried out to study the complex behavior of the system for reasonable ranges of parameters in WSN.

Abstract: The power system is a typical non-linear system, of which the influencing factors are complex. The existing power system stability analysis methods can only determine whether the system into chaos, and deem chaos unstable. The development of the science of chaos has opened up a new way for the power system stability analysis. First, chaotic time series based on the power system calculate the largest Lyapunov exponent of the power system time series by the use of C-C method in the chaos theory and reconstruction of phase space. Then it identifies Chaos according to the largest Lyapunov exponent. Finally, it determines whether the power system is the Lagrange stability according to the size of the index combined with systemic phase diagram. The analysis of actual power system simulation proved that it is feasible to use chaos theory to analyze the stability of the grid Lagrange.

Abstract: A period-doubling bifurcation may occur when the estimation error of the rotor time constant exists in an indirect field-oriented control (IFOC) of induction motor drives. Then chaos oscillations appear under some parameter values which are usually tested by the Largest Lyapunov exponents. In this paper, we apply the modified 0-1 method to detect chaos phenomenon instead, and design a controller to suppress chaos in the IFOC system. Simulation results indicate that the proper parameter region of the controller can be obtained with this method, and with the adaptive controller the system can quit from the chaotic state into the stable state effectively and robustly. The 0-1 method identifies chaotic behaviors directly through the time series without constructing phase space. Therefore, the proposed method is not affected by the complexity of the system and is not sensitive to noises.

Abstract: A novel chaos-control method of laser is presented by performing a path of photoelectric delayed nonlinear feedback. Two chaos-control models of injected semiconductor laser are studied by modulating the nonlinear and linear photoelectric delayed controllers. Firstly, by periodic modulation of the linear photocurrent under the condition of nonlinear control, the laser behavior can be brought into a dual-period, or multi-periodic state. Secondly, dynamical chaos-control is achieved successfully by switching the controllers.

Abstract: Symmetric features of the frieze group equivalent mappings were analysed, and two partitioning algorithms are given for constructing generalized Mandelbrot sets of frieze group equivalent mappings in order to study the characteristics of generalized Msets. Based on generating parameter space of dynamical system, lots of patterns of generalized Mandelbrot sets are produced.

Abstract: The principles and methods of chaos generation are researched using piecewise linear circuit theory. The chaos generation circuit based on integrated operational amplifiers is designed to realize chaos. Simulation results of the circuit are got using Multisim software. It indicates that using this method, the relationships and laws between chaos and various circuit element parameters can be better found out.

Abstract: Nonlinear dynamic-behavior analysis of rotor system under different parameters is presented. The derivation of nonlinear dynamic equations under the action of rub-impact force is set up basing on Jeffcott model, and the system bifurcation characteristics and influences has been investigated under the ratio of operating angular velocity and the rotor’ natural angular velocity influence by numerical analysis. Bifurcation and dynamical behaviors of nonlinear of system with the changes of argument (that is the ratio of operating angular velocity and the rotor’ natural angular velocity) under several specific parameters are analyzed. The results show that the ratio, rotor eccentricity and rotor stiffness have great effect on the dynamical behaviors of nonlinear system.

Abstract: This paper reports a novel three-dimensional autonomous chaotic system. By choosing an appropriate bifurcation parameter, we prove that a Hopf bifurcation occurs in this system when the bifurcation parameter exceeds a critical value, and some basic dynamical properties, such as Lyapunov exponents, fractal dimension, bifurcation diagram, continuous spectrum and chaotic dynamical behaviors of the new chaotic system are studied. Furthermore, the forming mechanism of its compound structure obtained by merging together two simple attractors after performing one mirror operation has been investigated by detailed numerical as well as theoretical analysis.

Abstract: In this paper, an effective self-embedding fragile watermarking scheme is proposed. The watermark is generated by encoding the DCT coefficients of each 2×2 block and embedded into another block. A non-linear pseudo random sequence is used for generating the block mapping which can enhance the security of the algorithm. An improved tamper localization and recovery algorithm are performed. The experiment results show that the tamper region can be successfully localized and exactly recovered, even if under the content-only tampering.