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排序方式: 共有2772条查询结果,搜索用时 15 毫秒
1.
2.
The present paper concerns the induction of stable sustained oscillation in feedback-linearizable single-input affine nonlinear dynamical systems via continuous-time state feedback control. The proposed application-oriented control approach is based on the conception of a state feedback controller that ensures the tracking of a limit cycle characterized in terms of the feedback-linearized system. Boundedness and convergence of the closed-loop trajectories are established following the Lyapunov theoretical framework and applying LaSalle׳s stability principle. The proposed approach is demonstrated with computer-simulated control experiments, showing that it ensures the convergence of the state trajectories of the controlled system to a designed limit cycle and that the methodology can, in principle, be applied to any single input feedback linearizable system. 相似文献
3.
Analysis of non-stationary electrochemical oscillations emerges utilization of the techniques allowing an observation of time evolution of their parameters such as instantaneous frequency, amplitude or frequency band. An algorithm of extraction of these parameters can be based on one of linear or quadratic time-frequency representations of oscillations record. In this paper, the authors present representatives of such transformations (Choi-Williams and Cone-shaped) originating from one of the most popular joint time-frequency energy distribution—Wigner-Ville distribution. Short introduction to the mathematics of the topic discussed is provided, then the authors present an example of application in the analysis of current oscillations of copper dissolution process. 相似文献
4.
Acoustic Emission (AE) signals, which are electrical version of acoustic emissions, are usually analysed using a set of signal
parameters. The major objective of signal analysis is to study the characteristics of the sources of emissions. Peak amplitude(P
a
) and rise time(R
t
) are two such parameters used for source characterization. In this paper, we theoretically investigate the efficiency ofP
a
andR
t
to classify and characterize AE sources by modelling the input stress pulse and transducer. Analytical expressions obtained
forP
a
andR
t
clearly indicate their use and efficiency for source characterization. It is believed that these results may be of use to
investigators in areas like control systems and signal processing also 相似文献
5.
6.
The notions of dynamical synchronization and adaptive dynamical synchronization problems are introduced. The algorithm solving adaptive synchronization problem for a subclass of Lurie systems with exciting input is proposed. The performance and potentialities of proposed solutions are demonstrated by two examples related to formation control and self‐organization of swarm systems. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
钱定榕 《红外与毫米波学报》1991,10(2):156-160
研究已表明掺杂HgCdTe中不存在对于自由载流子等离子体振荡的朗道阻尼,本文进一步研究了HgCdTe掺杂及随之产生的简并对自由载流子能量色散关系的影响,并将这种影响计入自由载流子的介电函数后,从理论上证明了掺杂窄禁带半导体中不存在朗道阻尼的现象是由于自由载流子能量色散关系变化引起其运动行为变化所致。 相似文献
8.
D. Bergmann U. KaiserS. Wagner 《Journal of Wind Engineering & Industrial Aerodynamics》2003,91(4):543-550
The determination of dynamic wind loads on buildings, i.e. pressure and deflection, has gained increasing interest (European Prestandard ENV 1991-2-4, Eurocode 1: basis of design and actions on structures—Part 2-4: actions on structures—wind actions, European Committe for Standardization, Brussels, 1995; DIN 1055 Teil 4 Lastannahmen für Bauten, Verkehrslasten, Windlasten bei nicht schwingungsanfälligen Bauwerken, 1991; N. Hölscher, M. Hortmanns, J. Sahlem, Praxisnahe Erfassung von Windwirkung an Industrie- und Hochbauten, Windwirkung im Bauwesen, Braunschweig, 7, Dreiländertagung D-A-CH 2001, Windtechnologische Gesselschaft, 2001 [1], [2] and [3]). Therefore, the spectral distributions of velocity and pressure fluctuations in wind tunnels are an important quality aspect. While velocity fluctuations can be manipulated by the obstacles used to create the turbulence, pressure fluctuations are influenced by acoustic noise as well. Especially, the first eigenfrequency of the longitudinal mode of the wind tunnel tends to disturb the pressure spectrum.In this paper, a solution for the reduction of low-frequency acoustic pressure fluctuation is presented and its application in the atmospheric boundary layer wind tunnel at the IAG is shown. 相似文献
9.
Seong Hyuk Lee Junghee Lee Kwan-Gu Kang Joon Sik Lee 《Journal of Mechanical Science and Technology》2006,20(8):1292-1301
This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated
by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser
pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin
film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established
for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results,
it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and
nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this
lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates
increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated.
For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser
irradiation. 相似文献
10.
T. Brard F. H. Cornet 《International Journal of Rock Mechanics and Mining Sciences》2003,40(7-8):1121-1140
When they occur, borehole breakouts are considered strong markers of principal stress directions at depth. An innovative processing method for automatically identifying breakouts from ultrasonic borehole wall images has been developed. It has been applied to data sets from two deep, sub-vertical wells (GPK1 and GPK2) at the Soultz geothermal site in eastern France. In well GPK1, below 3 km depth, compression breakouts, with a 95°±7° azimuth, increasingly occur with depth. They result from time dependent compression failure at sub-critical stress levels and are indicators of the minimum horizontal principal stress orientation. However, in the uppermost logged section of well GPK2 (1.6–2.9 km depth), continuous borehole elongations share roughly the same azimuth with so called drilling-induced fractures (164°±18° and 175°±17° azimuth, respectively). Both features concomitantly vanish with depth, together with the amplitude of the thermal perturbation induced by drilling. It is proposed that these latter borehole elongations result from a pervasive, cooling-induced, tensile micro-cracking process prior to macroscopic failure localization. They are termed thermal elongations and are indicators of the maximum horizontal principal stress orientation. Had a simple logging caliper tool been used for this work, these thermal elongations might have been confused with classical compression breakouts. A simple criterion for differentiating compression breakouts from thermal elongation is proposed. 相似文献