Biomedical subjects

Shiqun Zhu

Publications and source records attributed to Shiqun Zhu.

3 recordsLinked to original sources

PubMed2006

Brownian motor with time-delayed feedback.

An inertial Brownian motor with time-delayed feedback driven by an unbiased time-periodic force is investigated. It is found that the mean velocity and the rectification efficiency are decreased when the noise intensity is increased. While the shape of the mean velocity and the rectification efficiency can be changed from one peak to two peaks when the time delay is increased, the symmetry in the velocity probability distribution function is broken when the delay time is increased.

Biological Clocks↗

PubMed2003

Dispersive anomalous diffusive transport in ratchets with long-range correlated spatial disorder.

The effects of quenched disorder with long-range spatial correlations on the transport properties of an overdamped periodic ratchet are investigated. The modified Fourier-filtering method is applied to generate the long-range correlated spatial disorder with statistical properties eta(x)eta(x') approximately /x'-x/(-gamma), where gamma is the correlation exponent. Small amounts of this kind of quenched disorder are introduced in the equation of overdamped motion of a continuous time system, and the first two moments C1(t)= and C2(t)=<(x(t)- )(2) are calculated. We show that the drift velocity is almost independent of gamma. However, as a consequence of the long-range spatial correlations, the dispersive anomalous diffuse motion [C2(t) approximately t(H)] appears in ratchets, with the difussion exponent H (1<H<2) being dependent on gamma. Moreover, we show that both the amount of quenched disorder and the correlation degree can enhance the anomalous diffusive transport.

Journal Article↗

PubMed2003

Stochastic resonance driven by two different kinds of colored noise in a bistable system.

The phenomenon of stochastic resonance in a bistable nonlinear system is investigated when both the multiplicative noise and the coupling between additive and multiplicative noise are colored with different values of noise correlation time tau(1) and tau(2). Combining the functional analysis and unified colored noise approximation, the two different kinds of colored noise in the nonlinear system can be simplified. The signal-to-noise ratio is calculated when a weakly periodic signal is added to the system. It is found that there appears a transition between one peak and two peaks in the curve of the signal-to-noise ratio when either the noise correlation time tau(1) and tau(2) or the coupling strength lambda between additive and multiplicative noise is increased. The transition between one and two peaks depending on tau(1) and lambda is more complex than that depending on tau(2).

Journal Article↗