Zeng Chunhua

Stochastic Resonance in a Bacterium Growth System Subjected to Colored Noises

We present the logistic growth model to study the stochastic resonance (SR) in a bacterium growth system under the simultaneous action of two external multiplicative cross-correlation noises and periodic external forcing. The expression of the signal-to-noise ratio (SNR) for a bacterium growth system is derived by using the theory of SNR in the adiabatic limit. Based on SNR, we discuss the effects of self-correlation time τ1 and τ2, cross-correlation time τ3 and cross-correlation strength λ on the SNR. It is found that the self-correlation time τ1 and τ2, and cross-correlation strength λ enhance the SR of the bacterium growth system, while cross-correlation time τ3 weakens the SR of the bacterium growth system.

Transport enhancement and efficiency optimization in two heat reservoir ratchets

We study a Brownian motor moving in a sawtooth potential in the presence of an external driving force and two heat reservoirs. Based on the corresponding Fokker?Planck equation, the analytical expressions of the current and efficiency in the quasi-steady-state limit are obtained. The effects of temperature difference and the amplitude of the external driving force on the current and efficiency are discussed, respectively. The following is our findings. (i) The current increases with both ? and A. In other words, ? and A enhance the transport of the Brownian motor. (ii) The competition between the temperature difference and the amplitude of the external driving force can lead to efficiency optimization. The efficiency is a peaked function of temperature, i.e., ? > 0 and a lower amplitude value of the external driving force is necessary for efficiency optimization. (iii) The efficiency increases with ?, and decreases with A. ? and A play opposite roles with respect to the efficiency, which indicates that ? enhances the efficiency of energy transformation while A weakens it.

Entropic Resonant Activation and Stochastic Resonance Driven by Non-Gaussian Noise

The transition rate and stochastic resonance (SR) of a Brownian particle moving in a confined system under the presence of entropic barriers are investigated when the system is driven by non-Gaussian noise. The explicit expressions of the transition rate and the spectral power amplification (SPA) are obtained, respectively. The effects of the parameter q indicating the departure from the Gaussian noise and the correlation time τ of the non-Gaussian noise on the transition rate and the SPA are discussed. Research results show that: (i) The transition rate as a function of the noise strength exhibits a maximum. This maximum for transition rate identifies the phenomenon of entropic resonant activation (ERA), the parameter q and the noise correlation time τ weaken the ERA of the system; (ii) The curves of SPA appear a transition from one peak to double-peak, and then to one peak again as the noise correlation time τ of non-Gaussian noise increases.

Stochastic Resonance of a Periodically Driven Bistable System with Two Different Kinds of Time Delays

In this paper, we study the phenomenon of stochastic resonance (SR) in a periodically driven bistable system with correlations between multiplicative and additive white noise terms when there are two different kinds of time delays existed in the deterministic and fluctuating forces, respectively. Using the small time delay approximation and the theory of signal-to-noise ratio (SNR) in the adiabatic limit, the expression of SNR is obtained. The effects of the delay time τ in the deterministic force, and the delay time θ in the fluctuating force on SNR are discussed. Based on the numerical computation, it is found that: (i) There appears a reentrant transition between one peak and two peaks and then to one peak again in the curve of SNR when the value of the time delay θ is increased. (ii) SR can be realized by tuning the time delay τ or θ with fixed noise, i.e., delay-induced stochastic resonance (DSR) exists.

Colored Noises-Induced Regime Shifts in a Vegetation Ecological System

In this paper, we investigate the stationary probability distribution and mean first passage time in a vegetation ecological system, which is driven by cross-correlation between intrinsic and extrinsic colored noises as well as the nonzero cross-correlation in between. The impacts of the self-correlation time τ1 and τ2, the cross-correlation time τ3 and intensity k on the stationary probability distribution and mean first passage time are discussed, respectively. Our main results show that: (i) the self-correlation time τ1 can induce regime shifts from the desert state to the sustainable vegetation state, while the self-correlation time τ2, cross-correlation time τ3 and intensity k can induce regime shifts from the sustainable vegetation state to the desert state; and (ii) the self-correlation time τ1 or τ2 can enhance the stability of the sustainable vegetation biomass, while the cross-correlation time τ3 or strength k weakens the stability of the sustainable vegetation biomass.

The mean first passage time of a three-level atomic optical bistable system subjected to noise

The transient properties of a three-level atomic optical bistable system in the presence of multiplicative and additive noises are investigated. The explicit expressions of the mean first-passage time (MFPT) of the transition from the high intracavity intensity state to the low one are obtained by numerical computations. The impacts of the intensities of the multiplicative noise DM and the additive noise DA, the intensity of correlation between two noises λ, and the intensity of the incident light y on the MFPT are discussed, respectively. Our results show: (i) for the case of no correlation between two noises (λ = 0.0), the increase in DM and DA can lead to an increase in the probability of the transition to the low intracavity intensity state, while the increase in y can lead to a retardation of the transition; and (ii) for the case of correlation between two noises (λ = 0.0), the increase in λ can cause an increase in the probability of the transition, and the increase in DA can cause a retardation of the transition firstly and then an increase in the probability of the transition, i.e., the noise-enhanced stability is observed for the case of correlation between two noises.