Browsing by Author "Makhnovskii, Yu. A."

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Adiabatically slow and adiabatically fast driven ratchets
(2012-04-12)
Rozenbaum, V. M.
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Makhnovskii, Yu. A.
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Shapochkina, I. V.
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Sheu, S. -Y.
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Yang, D. -Y.
We revisit two known models of deterministically driven ratchets, which exhibit high energetic efficiency, with the goal to uncover similarities and differences in the principles of their operation. Both the models rely on adiabaticity of the potential change process, however, the adiabaticity that we deal with in the two cases is of different types, slow and fast. It is shown that in the former (latter) case the drift velocity is an even (odd) functional of the potential, with the notable consequence that for the adiabatically slow driven ratchet the necessary symmetry breaking occurs only due to time-dependent parametric perturbations, while the spatial asymmetry of the potential is a mandatory condition for the adiabatically fast driven ratchet to operate. To treat energetic characteristics, the models are restated in terms of traveling potential ratchets. With such an approach, we find that in these cases (i) the conditions of high energetic efficiency to be reached are similar, and (ii) the symmetry properties of the kinetic coefficients are different. Based on our results, a strategy for designing efficient Brownian motors is suggested.
Drift of particles caused by fluctuations of their sizes
(2017-03-01)
Zitserman, V. Yu.
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Makhnovskii, Yu. A.
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Trakhtenberg, L. I.
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Yang, D-Y.
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Lin, S. H.
Externally stimulated fluctuations of the size of a particle in an asymmetric environment result in its directional motion. This is demonstrated by considering the particle drift in a periodic symmetric channel, which arises due to fluctuations of the particle size. The emergence of the drift is caused by the time variation of the particle entropy, whereas fluctuations of the diffusion coefficient accompanying fluctuations of the size enhance the drift. The effect of the geometry of the channel and the amplitude and frequency of fluctuations on the drift velocity is studied by the Brownian dynamics method. A coarse-grained analytical description of the process is proposed whose predictions are in satisfactory agreement with the results of simulation.
Reciprocating and Directed Motion on the Nanoscale: A Simple Kinetic Model
(2010-02-11)
Rozenbaum, V. M.
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Makhnovskii, Yu. A.
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Yang, D. -Y.
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Sheu, S. -Y.
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Lin, S. H.
We consider noise-induced reciprocating motion on the nanoscale and its rectification to directed motion using a simple model in which transitions between two fluctuating states occur through two reaction channels with fluctuating transition rates. The fluctuations of states and transition rates arise from equilibrium thermal and external nonthermal noise which is in either case position-dependent. The model is equivalent to a Brownian particle hopping in a periodic double-well potential which randomly switches between two profiles. With a nonequilibrium noise, a generalized driving force may be regarded as the sum of two forces: one resulting from energy fluctuations and the other from fluctuations of the spatial dependence of the transition rates. This suggests two mechanisms, energetic and informational, by which the motion occurs. The reciprocating motion results in directed motion if rectified by asymmetric fluctuations of potential barriers. The energy conversion efficiency is calculated and the conditions to maximize it are established.
Reciprocating nanoengine
(2006-08-01)
Makhnovskii, Yu. A.
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Rozenbaum, V. M.
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Yang, D. -Y.
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Lin, S. H.
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Tsong, T. Y.
Brownian motion in a confining potential fluctuating between two spatially separated potential profiles is considered as a model of an engine converting nonequilibrium fluctuations into reciprocating motion on the nanoscale. We present two exact solutions obtained for the parabolic and step potential, which reveal the temperature and frequency-modulation behavior of the engine. The confining potential determines the interplay of the independent internal (thermal) and external (discrete) noises: the noises are cooperated for any potential, except the parabolic one. The engine can operate as a molecular motor, being supplemented by a rectifying mechanism.