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171.
ZHONG Wei-Rong SHAO Yuan-Zhi BIE Meng-Jie HE Zhen-Hui 《理论物理通讯》2008,50(9):793-796
Understanding the cause of the synchronization of population evolution is an important issue for ecological improvement. Here we present a Lotka-Volterra-type model driven by two correlated environmental noises and show, via theoretical analysis and direct simulation, that noise correlation can induce a synchronization of the mutualists. The time series of mutual species exhibit a chaotic-like fluctuation, which is independent of the noise correlation, however, the chaotic fluctuation of mutual species ratio decreases with the noise correlation. A quantitative parameter defined for characterizing chaotic fluctuation provides a good approach to measure when the complete synchronization happens. 相似文献
172.
We consider a new class of estimators for volatility functionals in the setting of frequently observed Itō diffusions which are disturbed by i.i.d. noise. These statistics extend the approach of pre-averaging as a general method for the estimation of the integrated volatility in the presence of microstructure noise and are closely related to the original concept of bipower variation in the no-noise case. We show that this approach provides efficient estimators for a large class of integrated powers of volatility and prove the associated (stable) central limit theorems. In a more general Itō semimartingale framework this method can be used to define both estimators for the entire quadratic variation of the underlying process and jump-robust estimators which are consistent for various functionals of volatility. As a by-product we obtain a simple test for the presence of jumps in the underlying semimartingale. 相似文献
173.
Experimental measurements of power spectra of a single longitudinal and transverse mode ring dye laser are presented that reveal the critical slowing down of the laser near threshold. External pump noise serves as a probe of the frequency response of the dye laser. Detailed comparisons of the spectral characteristics with computer simulations and an approximate analytic theory are given. The dynamics of spatial pattern formation in a multimode dye laser is examined through measurements of first-passage-time distributions. A comparison of the experiments with computer simulations based on a simple theoretical model of the two-mode laser shows qualitative agreement. These measurements indicate that there are a variety of complex phenomena associated with the transverse mode pattern formation dynamics that need to be addressed theoretically and studied further experimentally. 相似文献
174.
The effect of fluctuations in the two-variable discrete delay model proposed earlier by us [1] for the circadian rhythm of
the fungal species Neurospora Crassa is studied. We have investigated the effect of parametric and additive noise in two different regimes namely, steady-state
and Period-1 regimes. It is found that under the influence of noise coherent oscillations are generated in the steady-state.
Oscillations are preserved and robust to a wide range of noise intensity in the Period-1 regime. The oscillations in both
these regimes are always found to be close to the circadian period (21.5 h). Coherence resonance is observed when parametric
or velocity additive noise is added near the Hopf bifurcation. Finally, the implications of fluctuations in circadian rhythms
are discussed.
This article is dedicated to Professor Karl Jug on the occassion of his sixtyfifth birthday. 相似文献
175.
A new type of acoustic liner developed for broadband noise reduction in flow ducts is considered in this paper. It combines passive absorbent properties of a porous layer and active control at its rear face. The complete design procedure of this hybrid passive/active liner is developed here. The passive part is first considered with the determination of a suitable porous material and the cut-off frequency separating the active low frequency regime from the passive high frequency one. The control system is then presented: a digital adaptive feedback control is performed independently cell by cell, allowing an easy subsequent increase of the liner surface. The entire optimization process has been successfully applied to a laboratory flow duct: both predictions and measurements show the interest of the hybrid liner to reduce the noise radiation. 相似文献
176.
You Ming-Chang 《International Journal of Infrared and Millimeter Waves》1986,7(6):919-925
The configurations of the coupling network, which can effectively aecrease the effect of the noise sources within the amplifier on the equivalent input noise of the whole pyroelectric detector-amplifier system, are studied. The influences of feedback upon the noise properties of the basic amplifiers are analyzed. The procedures of designing low-noise pyroelectric detector-amplifier systems are followed. 相似文献
177.
A. Robledo 《Pramana》2005,64(6):947-956
We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order
ζ > 1, the dynamics rigorously obeys the Tsallis statistics. We account for theq-indices and the generalized Lyapunov coefficients λq that characterize the universality classes of the pitchfork and tangent bifurcations. We identify the Mori singularities
in the Lyapunov spectrum at the onset of chaos with the appearance of a special value for the entropic indexq. The physical area of the Tsallis statistics is further probed by considering the dynamics near criticality and glass formation
in thermal systems. In both cases a close connection is made with states in unimodal maps with vanishing Lyapunov coefficients. 相似文献
178.
B. A. van Tiggelen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):261-269
In this work we apply field regularization techniques to formulate a number of new phenomena related to momentum induced by
electromagnetic zero-point fluctuations. We discuss the zero-point momentum associated with magneto-electric media, with moving
media, and with
magneto-chiral media. 相似文献
179.
Cenap Özel Erol Yılmaz Hünkar Kayhan Aliekber Aktağ 《International Journal of Theoretical Physics》2008,47(12):3101-3107
In this paper, the entanglement properties of a system of two atoms inside an optical cavity in a stochastic interaction with
field are studied by the Jaynes-Cummings Model. The phase telegraph noise is considered as a noise term and an exact solution
to the model is obtained. The solution reveals the resulting decoherence effects of the noise on the entanglement properties
of the system. It shows that under the noise the individual atoms do not entangle with the cavity field. However, a strong
atom-atom entanglement is observed in a stationary state. It is seen that a relatively strong noise is cooperative in the
construction of the steady state atom-atom entanglement. 相似文献
180.
Long-Distance Transmission at Zero Dispersion: Exact Expressions for One-Time Statistical Properties
We study the transmission of a signal through a dispersionless fiber with in-line amplifiers. The nonlinearities of the fiber and the noise generated at each amplifier are taken into account. Exact analytical expressions are obtained for the field averages. From these results we obtain the distributed amplification approximation, and study the conditions under which this approximation is valid. 相似文献