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Nonlinear Characteristics (nonlinear + characteristic)
Selected AbstractsA comprehensive approach to characterization of the nonlinearity of runoff in the headwaters of the Tarim River, western ChinaHYDROLOGICAL PROCESSES, Issue 2 2010Jianhua Xu Abstract Nonlinear characteristics of the runoff processes in the headwaters of the Tarim River were identified and evaluated using several selected methods, including wavelet analysis, correlation dimension, and R/S analysis. Time-series of annual data describing runoff, average temperature, and precipitation from 1957 to 2005 were used to construct and test empirical models. The primary findings of this study were as follows: (1) The annual runoff of the headwaters are complex and nonlinear in nature, and they each presented periodic, nonlinear trends at the chosen time scales, chaotic dynamics, and long-memory characteristics. (2) These nonlinear trends appeared to have resulted from the regional climatic changes that occurred during the study period. The periodicity of changes in runoff occurred on an approximately 25-year cycle, which appeared to be correlated with temperature and precipitation cycles. In addition, the annual runoff exhibited a significant, positive correlation with the temperature and precipitation factors at the 4-, 8-, 16-, and 32-year temporal scales. (3) The correlation dimensions of the attractor derived from the runoff time series for the Hotan, Yarkand, and Aksu rivers were all greater than 3·0 and non-integral, implying that all three rivers are dynamic chaotic systems that are sensitive to initial conditions, and that the dynamic modelling of their annual runoff requires at least four independent variables. (4) The computed Hurst exponents indicate that a long-term memory characteristic exists in the annual runoff processes. However, there were some differences observed, with the Aksu and Yarkand rivers demonstrating a persistent trait, and the Hotan River exhibiting an anti-persistent feature. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nonlinear adaptive tracking-control synthesis for functionally uncertain systemsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2010Zenon Zwierzewicz Abstract The paper is concerned with the problem of adaptive tracking system control synthesis. It is assumed that a nonlinear, feedback linearizable object dynamics (model structure) is (partially) unknown and some of its nonlinear characteristics can be approximated by a sort of functional approximators. It has been proven that proportional state feedback plus parameter adaptation are able to assure its asymptotic stability. This form of controller permits online compensation of unknown model nonlinearities and exogenous disturbances, which results in satisfactory tracking performance. An interesting feature of the system is that the whole process control is performed without requisite asymptotic convergence of approximator parameters to the postulated ,true' values. It has been noticed that the parameters play rather a role of slack variables on which potential errors (that otherwise would affect the state variables) cumulate. The system's performance has been tested via Matlab/Simulink simulations via an example of ship path-following problem. Copyright © 2009 John Wiley & Sons, Ltd. [source] A dual continuous- and burst-mode clock recovery module utilizing fiber dispersionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Minhui Yan Abstract A clock recovery module suitable for both burst- and continuous-mode optical receiver utilizing fiber dispersion is experimentally demonstrated for the first time. The module utilizes the nonlinear characteristics of the received nonreturn-to-zero (NRZ) optical signals experiencing the fiber dispersion and the photo-detection to extract the clock information. Experiments demonstrated its functionality in both operation modes up to 9 Gbps. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1747,1750, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25347 [source] Image-based hysteresis modeling and compensation for an AFM piezo-scanner,ASIAN JOURNAL OF CONTROL, Issue 2 2009Yudong Zhang Abstract As an important component of Atomic Force Microscopes (AFM), a piezo-scanner exhibits some undesired nonlinear characteristics, among which the inherent hysteresis largely decreases positioning accuracy during scanning and nano-manipulation process. To alleviate this problem, an image-based approach is proposed in this paper to model and then compensate for the hysteresis behavior of the piezo-scanner. Specifically, some scanning images over standard samples are utilized to identify the parameters of the classical Preisach model (CPM) of hysteresis. On the basis of the obtained model, an inversion-based technique is adopted to design a compensator for the hysteresis of the piezo-scanner. The proposed algorithm presents such advantages as low cost and little complexity since no nanoscale position sensor is required to collect identification data. Some scanning and nano-imprinting results are included to demonstrate the performance of the proposed strategy. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] | ||||||||||