共查询到20条相似文献,搜索用时 15 毫秒
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A time-delayed feedback ratchet consisting of two Brownian particles interacting through the elastic spring is consid ered. The model describes the directed transport of coupled Brownian particles in an asymmetric two-well ratchet potential which can be calculated theoretically and implemented experimentally. We explore how the centre-of-mass velocity is af fected by the time delay, natural length of the spring, amplitude strength, angular frequency, external force, and the structure of the potential. It is found that the enhancement of the current can be obtained by varying the coupling strength of the delayed feedback system. When the thermal fluctuation and the harmonic potential match appropriately, directed current evolves periodically with the natural length of the spring and can achieve a higher transport coherence. Moreover, the external force and the amplitude strength can enhance the directed transport of coupled Brownian particles under certain conditions. It is expected that the polymer of large biological molecules may demonstrate a variety of novel cooperative effects in real propelling devices. 相似文献
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本文研究了周期对称势中时间非对称外力驱动的布朗粒子输运现象, 建立了分数阶布朗马达输运模型. 其中外力是零均值的, 而分数阶阶数则刻画了客观环境的非均匀性程度. 通过将模型离散化进行数值模拟, 讨论了分数阶阶数、系统参量和外部参量与定向流之间的依赖关系. 研究表明, 即使没有倾斜势场的作用, 时间非对称外力也可以诱导系统产生定向输运; 输运速度随分数阶阶数的增大而单调递增; 当阶数固定时, 系统的输运速度会随着势垒高度、噪声强度非单调变化, 表现出广义随机共振现象. 分析指出, 分数阶郎之万方程所刻画的输运现象是在整数阶模型基础上的一个推广, 进而为输运现象提供了一个可能更为真实的模型. 相似文献
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The Kanai model of a quantum mechanical Brownian particle is used to examine the effect of interactions between particles and their environment. Random forces cause the thermalization of the particle. Reflection of a particle from a step barrier is analyzed. The problem of tunneling of the Brownian particle through a rectangular barrier is solved. Finally, a solution for a Brownian particle in a box is presented. 相似文献
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《理论物理通讯》2015,(9)
The transport of Brownian particles in the infinite channel within an external force along the axis of the channel has been studied. In this paper, we study the transport of Brownian particle in the infinite channel within an external force along the axis of the channel and an external force in the transversal direction. In this more sophisticated situation, some property is similar to the simple situation, but some interesting property also appears. 相似文献
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The transport of Brownian particles in the infinite channel within an external force along the axis of the channel has been studied. In this paper, we study the transport of Brownian particle in the infinite channel within an external force along the axis of the channel and an external force in the transversal direction. In this more sophisticated situation, some property is similar to the simple situation, but some interesting property also appears. 相似文献
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The transport properties of an active Brownian particle with a time-delayed feedback and an external bias are investigated theoretically. By virtue of the perturbation theory for small delay, analytical expressions for the mean velocity and effective diffusion coefficient are derived. There exists a critical absolute value of the bias, below and above which the delay, respectively, enhances and weakens the diffusion, for a fixed noise intensity. The effects of delay observed above are more pronounced for weaker noise. These results are further verified via direct numerical simulations. 相似文献
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We present explicit expressions for the Floquet states of a periodically kicked particle in coordinate and momentum representations.
These states have been used to evaluate the energy of the particle after an arbitrary number of kicks. 相似文献
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Directed transport of Brownian particles in a deformable two-dimensional tube is investigated in the presence of asymmetric unbiased fluctuations. It is found that the current can be enhanced by choosing appropriate noise intensity and deformation. There exists a value of deformation at which the current takes its maximum. For small deformable parameter, transport is dominated by noise intensity, and for very large deformable parameter, transport is dominated by deformation. The competition between the deformation and the asymmetric driving forces will induce rich phenomena in transport. 相似文献
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The hopping motion of a classical bounded pair of two particles along a chain is investigated. It is shown that in the asymmetric
case of the system dynamics including excited states which differ from the respective ground states by the barrier to be overcome
by one of the two particles, the over- and underpopulation of these excited states leads to a directed motion of the particle
pair. Thereby, overpopulation results in one direction of motion, whereas underpopulation results in the opposite direction,
and the mean velocity is determined by the amount of over-resp. underpopulation. For small deviations from equilibrium, the
system exhibits linear response well known from other ratchet-type models. Possible generalizations and applications are discussed.
Received 17 August 2001 and Received in final form 11 October 2001 相似文献
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D. Chakraborty 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):375-380
In this article, we present molecular dynamics study of the velocity autocorrelation
function (VACF) of a Brownian particle. We compare the results of the simulation with the
exact analytic predictions for a compressible fluid from [T.S. Chow, J.J. Hermans, Physica
65, 156 (1973)] and an approximate result combining the predictions from
hydrodynamics at short and long times. The physical quantities which determine the decay
were determined from separate bulk simulations of the Lennard-Jones fluid at the same
thermodynamic state point. We observe that the long-time regime of the VACF compares well
the predictions from the macroscopic hydrodynamics, but the intermediate decay is
sensitive to the viscoelastic nature of the solvent. 相似文献
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Frank Grossmann Thomas Dittrich Peter Jung Peter Hänggi 《Journal of statistical physics》1993,70(1-2):229-245
The quantum dynamics of a quartic double well, subjected to a harmonically oscillating field, is studied in the framework of the Floquet formalism. The modifications of the familiar tunneling process due to the driving are investigated numerically and explained in terms of the structure of the corresponding local quasienergy spectrum. In particular, there is a one-dimensional manifold in the parameter space spanned by the amplitude and frequency of the driving force, where tunneling is almost completely suppressed by the coherent driving. The quantal dynamics in the semiclassical regime as well as the influence of weak incoherent processes are briefly discussed. 相似文献
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The frequency dependent mobility of a Brownian particle moving in a double well potential is calculated for different damping parameters and temperatures by means of continued fraction approximations. These results are remarkably well reproduced by a simple memory function ansatz. Applications to the motion of Ag+ ions in Ag3SX(X =I, Br) crystals are indicated. 相似文献
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Lemons D.S. Kaufman D.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(5):1288-1296
We develop and numerically illustrate an exact solution of the multivariate, stochastic, differential equations that govern the velocity and position of a charged particle in a plane normal to a uniform, stationary, magnetic field. The equations self-consistently incorporate the Lorentz force into an Ornstein-Uhlenbeck collision model. Properties of the solution in the infinite dissipation limit are explored and the spectral energy density function is found 相似文献
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Roumen Tsekov 《Physics letters. A》2018,382(33):2230-2232
The Klein–Kramers equation, governing the Brownian motion of a classical particle in a quantum environment under the action of an arbitrary external potential, is derived. Quantum temperature and friction operators are introduced and at large friction the corresponding Smoluchowski equation is obtained. Introducing the Bohm quantum potential, this Smoluchowski equation is extended to describe the Brownian motion of a quantum particle in quantum environment. 相似文献
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Masumi Sato 《等离子体物理论文集》1971,11(6):445-459
Moving striations in the tapered tube with smoothly changing radius are studied experimentally. The frequency depends on local tube radius by nature and increases toward the narrow end of the tube, independent of direction and magnitude of the discharge current. Radius-frequency versus radius-pressure is compatible with the similarity law for striations in cylindrical tubes. When there appears synchronization, the frequency becomes apparently constant throughout the tube column. The wavelength shows different dependences on radius without and with the synchronization. An important role is played by the feedback through an electric circuit. Also, direction and magnitude of the current have influence on the phenomena. Steady states in the tubes are compared with those in cylindrical tubes. An attempt is made to explain the observed synchronizations and then the remarkable discrepancies between the previous experiments can be eliminated. 相似文献