Ai Bao-Quan

Effects of Colored Noise on Periodic Orbits in a One-Dimensional Map

Noise can induce inverse period-doubling transition and chaos. The effects of the colored noise on periodic orbits, of the different periodic sequences in the logistic map, are investigated. It is found that the dynamical behaviors of the orbits, induced by an exponentially correlated colored noise, are different in the mergence of transition, and the effects of the noise intensity on their dynamical behaviors are different from the effects of the correlation time of noise. Remarkably, the noise can induce new periodic orbits, namely, two new orbits emerge in the period-four sequence at the bifurcation parameter value μ = 3.5, four new orbits in the period-eight sequence at μ = 3.55, and three new orbits in the period-six sequence at μ = 3.846, respectively. Moreover, the dynamical behaviors of the new orbits clearly show the resonancelike response to the colored noise.

Enhancement effect of asymmetry on the thermal conductivity of double-stranded chain systems

Using nonequilibrium molecular dynamics simulations, we study the thermal conductivity of asymmetric double chains. We couple two different single chains through interchain coupling to build three kinds of asymmetric double-stranded chain system: intrachain interaction, external potential, and mass asymmetric double chains. It is reported that asymmetry is helpful in improving the thermal conductivity of the system. We first propose double-heat flux channels to explain the influence of asymmetric structures on the thermal conductivity. The phonon spectral behaviour and finite size effect are also included.

Particle Transport with Asymmetric Unbiased Forces and Entropic Barrier

Transport of a Brownian particle moving along the axis of a three-dimensional (3D) symmetric and periodic tube is investigated in the presence of asymmetric unbiased forces. It is found that in the presence of entropic barrier, the asymmetry of the unbiased forces is a way of inducing a net particle current. The particle current is a peaked function of temperature, which indicates that the thermal noise may facilitate the transport even in the presence of entropic barrier. There exists an optimized radius at the bottleneck at which the particle current takes its maximum value. The current can be influenced by the slope of tube walls and there exists an optimized slope for which the particle current takes its maximum value.

Current Reversal Due to Coupling Between Asymmetrical Driving Force and Ratchet Potential

Transport of a Brownian particle moving in a periodic potential is investigated in the presence of an asymmetric unbiased external force. The asymmetry of the external force and the asymmetry of the potential are the two ways of inducing a net current. It is found that the competition of the spatial asymmetry of potential with the temporal asymmetry of the external force leads to the phenomena like current reversal. The competition between the two opposite driving factors is a necessary but not a sufficient condition for current reversals.

Controlling Thermal Conductivity of Few-Layer Graphene Nanoribbons by Using the Transversal Pressure

We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations. It is reported that the pressure can improve the thermal conductivity of few-layer graphene nanoribbons. This improvement can reach 37.5% in the low temperature region. The pressure dependence of thermal conductivity is also investigated for different length, width and thickness of few-layer graphene. Our results provide an alternative option to tuning thermal conductivity of few-layer graphene nanoribbons. Furthermore, it maybe indicate a so-called pressure-thermal effect in nanomaterials.

Directed Current Induced by an Symmetrically ac Force Coexisting with a Time-Delayed Feedback

We study the transport of overdamped Brownian particles in a symmetrically periodic potential in the presence of an asymmetrically ac driving force and a time-delayed feedback. It is found that for low frequencies, the average velocity can be negative by changing the driving amplitude, for high frequencies, there exists an optimized driving amplitude at which the average velocity takes its maximum value. Additionally, there is a threshold value of driving amplitude below which no directed transport can be obtained for high frequencies. For the large value of the delay time, the average velocity is independent of the delay time.

Noise-Induced Transition in a Voltage-Controlled Oscillator Neuron Model

In the presence of Gaussian white noise, we study the properties of voltage-controlled oscillator neuron model and discuss the effects of the additive and multiplicative noise. It is found that the additive noise can accelerate and counterwork the firing of neuron, which depends on the value of central frequency of neuron itself, while multiplicative noise can induce the continuous change or mutation of membrane potential.

Population Growth of Small Harmful Rats in Grassland Subjected to Noise

The population growth of small harmful rats in grassland subjected to environment fluctuation has been modelled in a logistic equation. Two correlated random variables responsible to the fluctuation of the genetic factor and the suppression factor are used. A two-peak structure of the steady probability distribution of rate population is observed in the large fluctuation regime of the genetic factor. With the increase of correlation constant λ, the steady probability distribution can change from two peaks to a single peak. The suppression factor μ and its fluctuation also affect the steady probability distribution and can push it toward a small population.

Current Inversion in a Temperature Ratchet with Asymmetric Unbiased External Forces

Transport of a Brownian particle moving in a symmetric potential is investigated in the presence of an asymmetric unbiased external force. The viscous medium is alternately in contact with the two heat reservoirs. We present the analytical expression of the net current at the quasi-steady state limit. It is found that the competition of the temporal asymmetric parameter of the driving force with the temperature difference leads to current reversals. The competition between the two opposite driving factors is a necessary but not a sufficient condition for current reversals.

A General Random Walk Model of Molecular Motor

A general random walk model framework is presented which can be used to statistically describe the internal dynamics and external mechanical movement of molecular motors along filament track. The motion of molecular motor in a periodic potential and a constant force is considered. We show that the molecular motors movement becomes slower with the potential barrier increasing, but if the force is increased, the molecular motors movement becomes faster. The relation between the effective rate constant and the potential barriers height, and that between the effective rate constant and the value of the force are discussed. Our results are consistent with the experiments and relevant theoretical consideration, and can be used to explain some physiological phenomena.