RF-Interferences Generate Chaotic GHz FM—Carrier for Communications

Following the principle of a highly nonlinear delay oscillator, we demonstrate the generation of an RF chaotic frequency modulated carrier, which could be used in chaos based communication systems. The nonlinear process is provided by the transfer function of an RF interferometer, modulating the amplitude of an FM signal; for this purpose, the path difference required for the interference process, as well as a long delay required for complex chaotic oscillation, are designed through the use of optical fibers. The RF signal used to produce interferences is transposed in the optical domain by a direct laser modulation with the gigahertz chaotic FM signal. The interference is obtained at fiber outputs terminated by photodiodes for backconversion of the RF signal into the electrical domain. Experimental results reporting the particular dynamical behavior of the nonlinear delay RF oscillator are presented, and also discussed in terms of chaos communication applications     

A SCBSS methodology for time-frequency overlapped signals using non-negative matrix factorisation

This article presents a new methodology for single-channel blind signal separation (SCBSS) of time-frequency overlapped signals in electromagnetic surveillance domain. The proposed algorithm is based on non-negative matrix factorisation (NMF) through a dynamical embedding framework. This method is deterministic requiring no priori information of the original signals. Firstly, a series of delay vectors of the single-channel recording are selected to construct an appropriate dynamical embedding matrix. NMF algorithm is used to decompose the dynamical embedding matrix. Then, a convenient expansion basis of original sources can be obtained, which will be projected back to the original measurement space according to the dynamical embedding framework. The power density spectrum of the projected components and the independent nature of original signals are employed to extract the interested signals from measurement space. The feasibility and effectiveness of proposed algorithm are proved by computer simulation.     

AUTOMATICALLY EXTRACTING AND OPTIMIZING FUZZY RULE BASE

A method of automatically extracting and optimizing fuzzy rule base is presented in this paper. Firstly, it applies the method of CCM (cell-to-cell mapping) to analyze the evolving trend and global behavior of a fuzzy dynamical system based on a cell state space, which is characterized by equilibrium, cost and their domain of attractions. Secondly, each rule base is evaluated to determine a performance index based on the information of the system obtained by CCM. Thirdly, CA (Genetic Algorithm) optimizes the coded rule bases according to the performance index generation by generation. The method presented in this paper can be applied to various systems (linear or nonlinear, continuous or discrete) to automatically obtain optimal rule base, for it fuses the advantages of GA and CCM. As an example, a complicated nonlinear system-an inverted pendulum is simulated to demonstrate the validity of the method.     

Asymmetrical Oscillations in Digitally Controlled Power-Factor-Correction Boost Converters

Digitally controlled power-factor-correction (PFC) converters are essentially piecewise-smooth nonlinear systems due to their switching action. However, their complex behavior almost remains unexplored. Unlike analog control, digital control introduces a time delay due to the sample-and-hold and the digital computation. Here, a small-signal model that takes the time delay into account is derived to judge the stability of a digitally controlled PFC boost converter. It is proven that the time delay seriously degrades the converter's stability. After the inner current loop and/or the outer voltage loop lose stability, we experimentally discover that oscillations begin to occur, and the oscillations are asymmetrical. Such an asymmetry can be interpreted by the underdevelopment characteristic of the dynamical behavior in the digitally controlled PFC boost converter. The results reported in this brief offer more knowledge about the dynamical behavior in digitally controlled PFC converters.      

A dynamical polarization mode dispersion emulator

A polarization mode dispersion (PMD) emulator is presented which accurately follows the dynamics of PMD in field optical fiber. A modification on a dynamic mode coupling wave-plate model is presented to model the emulator. It is found that the emulator and model can accurately describe the dynamical behavior of the state of polarization and thus PMD in a field fiber. The emulator is shown to be repeatable. Generally, the dynamical PMD emulator is shown to cause more realistic bit-error-rate degradation than a classical PMD emulator.     

Simplified model for the domain dynamics in Gunn-effect semiconductors covered with dielectric sheets

A simplified model is proposed which describes the effect of the stray fields in dielectric surface layers on the dynamical behaviour of domains in thin Gunn-effect semiconductors. The stray fields cause an increase in domain capacitance and hence a decrease in build-up time which leads to larger n0L products for stable operation.     

Frequency domain identification methods

Methods for estimating linear dynamical models from frequency data are studied, including the properties of frequency domain data generated by the discrete Fourier transform. The stochastic characteristics of the frequency domain data lead to a maximum likelihood (ML) formulation of the frequency domain estimation problem. Both discretetime and continuous time models are discussed. Consistency and variance of the ML estimate are described, and the connection with simpler frequency domain estimation schemes as well as the time domain ML method is pointed out.Supported by the Swedish Foundation for International Cooperation in Research and Higher Education (STINT). This work was partly completed while the author was visiting the Department of Electrical and Computer Engineering, University of Newcastle, Australia.     

Bifurcation analysis of switched dynamical systems with periodically moving borders

This paper describes a method for analyzing the bifurcation phenomena in switched dynamical systems whose switching borders are varying periodically with time. The type of systems under study covers most of power electronics circuits where two or more dynamical systems are cyclically switched according to the interaction of the state variables and some periodically moving borders. In particular, the complex bifurcation behavior of a voltage feedback buck converter is studied in detail. The analytical method developed in this paper allows bifurcation scenarios to be clearly revealed in any chosen parameter space.     

DNA分子在调制激光作用下的动力学行为研究

本文在脱氧核糖核酸动力学方程的基础上,建立了ＤＮＡ分子在调制激光作用下的动力学方程,并研究了在激光的电场和频率分别受到正弦调制和混沌调制的情形下ＤＡＮ分子的动力学时间演化行为。     

Experimental and theoretical study of filtered optical feedback ina semiconductor laser

We report on the systematical investigation of the steady-state regime and the dynamical behavior of a semiconductor laser subject to delayed filtered optical feedback. We study a Fabry-Perot (FP) interferometer type of filter placed in the external feedback loop of a diode laser. The effects of the filter on the locking of the diode laser frequency to the external cavity modes are described. We report and observe hysteresis, bistability, and multistability and show that all these are well described by a set of rate equations for the coupled laser and FP cavity system. We also present an experimental stability diagram that summarizes the dynamical behavior of the system     

Neuro-computing versus linear statistical techniques applied to liver transplant monitoring: a comparative study

This paper explores the potential for the application of neurocomputing in on-line monitoring in the liver transplantation domain. It extends our previously documented work to provide both an assessment of the performance gains achievable by incorporating temporal and dynamical information about the measurements made on a patient as well as presenting a novel computerized clinical decision aid for this domain. A comparison of the performance of linear and nonlinear classification system is made and used to motivate the final selection of the diagnostic inputs.     

Design and experimental confirmation of a novel switched hyperchaotic system

To generate complex pseudo-noise (PN) sequences for chaos-based communications, this article presents a novel switched hyperchaotic model, which is constructed based on a modified Chen system by introducing a dynamical controller. The system consists of two different hyperchaotic subsystems and can change its behavior randomly via a switching function. Basic dynamical behaviors of the hyperchaotic system are further investigated. Furthermore, the switched system is confirmed by its positive Lyapunov exponents and laboratory measurements by an electronic circuit.     

Bayesian nonstationary autoregressive models for biomedical signal analysis

We describe a variational Bayesian algorithm for the estimation of a multivariate autoregressive model with time-varying coefficients that adapt according to a linear dynamical system. The algorithm allows for time and frequency domain characterization of nonstationary multivariate signals and is especially suited to the analysis of event-related data. Results are presented on synthetic data and real electroencephalogram data recorded in event-related desynchronization and photic synchronization scenarios.     

基于混沌映射的鲁棒性图像水印算法

本文提出一种基于混沌映射的强鲁棒性数字图像水印算法,首先用一混沌动态系统对水印信息进行预处理,而后将其扩频调制在图像空间域,并且使水印嵌入强度自适应于图像;通过预置已知模板和嵌入多块水印可实现水印检测位置的几何校准.实验结果表明,采用该算法实现的水印对常见的图像处理和几何变换具有很好的鲁棒性.     

Complicated Attractor and Novel Route to Chaos via Cubic Nonlinearity Controller

By introducing a nonlinear state feedback controller, a complicated chaotic attractor of fourdimensional continuous autonomous chaotic system evolved from Lorenz system is proposed. The controller consists of a cubic cross-product term of three variables and a self variable term with control parameter. This paper verifies that the proposed system has complex dynamical behavior, which can evolve into periodic and chaotic behavior cyclically. These circular routes to chaos have self-similar bifurcation structure in a wide parameter variation range. An electronic circuit is designed to demonstrate the complicated attractor.     

The system modelling and circuit implementation from time–frequency domain signal specifications

The system modelling and the circuit implementation of the nonlinear circuits using the wavelet domain techniques has been accomplished in this study. When the time–frequency domain specifications have been given as the wavelet ridges, the signal with the given ridges has been synthesized. Then, the dynamical wavelet network has been trained for the synthesized signal. The circuit of the wavelet network has been designed and simulated.     

Measurement and Simulation of Distributed-Feedback Tapered Master-Oscillator Power Amplifiers

The spectral and spatial behavior of monolithically integrated distributed-feedback tapered master-oscillator power amplifiers emitting around 973 nm is experimentally and theoretically investigated. We demonstrate a good agreement between experiments and theory and analyze peculiarities of the observed dynamical regimes.     

Spontaneous spatiotemporal instabilities in current modulatedmaster oscillator power amplifier lasers

We provide the first comprehensive theoretical evidence for nonlinear space-time dynamical behavior which seriously degrades the performance of a monolithically integrated master oscillator power amplifier laser under direct current modulation of the master oscillator. A host of instabilities, reflecting dynamical behavior of different sections of the device, are possible. These instabilities are due to the combination of weak feedback from the power amplifier section of the device causing leakage into the master oscillator section, from the buildup of unsaturated carriers along the narrow edges of the expanding flare and differential saturation of the passive regions under the distributed Bragg reflector grating sections     

Transport in Short-Period GaAs/AlAs Superlattices with Electric Domains

Electronic transport in short-period GaAs/AlAs superlattices with resonant cavities was studied at room temperature. The evolution of tunneling current at forward and backward bias sweep was investigated. The step-like decrease in current at some threshold voltage was referred to moving domain formation. The current hysteresis observed in current-voltage characteristics was explained by changes in electrical domain regimes. The series of maxima in the current-voltage characteristics was attributed to resonant tunneling of electrons through several barriers inside the domain. The change of threshold voltage for the domain formation at the change of the cavity parameters explained by the excitation of high-amplitude oscillations in the cavity which demonstrated the possibility to excite oscillations in the THz cavity by dynamical negative resistance of SLs with domains.