The railway pantograph-catenary system employs a ratchet compensation device to sustain the tension of the contact wire.However,the excessive weight associated with the ratchet structure adversely affects the performa...The railway pantograph-catenary system employs a ratchet compensation device to sustain the tension of the contact wire.However,the excessive weight associated with the ratchet structure adversely affects the performance of the compensation device.An optimization design aimed at lightweight optimization of the ratchet wheel structure can enhance the system’s agility,improve material utilization,and reduce costs.This study uses a finite element model to establish an equivalent load model for the ratchet under service conditions and analyzes its load-bearing state.An optimization model was created and solved using ANSYS Workbench.The topological optimization configurations were compared under unconstrained conditions and four different periodic constraint scenarios.Following this,the structure was redesigned based on the topological optimization results,and a simulation analysis was conducted to compare the reconstructed model with the original model.The comparison results indicate that the masses of all four optimized models have been reduced by more than 10%.Additionally,under conditions of a fully wound compensation rope,the maximum stress has decreased by over 20%,leading to a more uniform stress distribution and improved overall performance.The topology optimization and redesign method based on periodic constraints offers a viable engineering solution for the lightweight design of the ratchet structure.展开更多
We presented a detailed investigation on the movement of two-headed Brownian motors in an asymmetric potential under a feedback control. By numerical simulations the direct current is obtained. The current is periodic...We presented a detailed investigation on the movement of two-headed Brownian motors in an asymmetric potential under a feedback control. By numerical simulations the direct current is obtained. The current is periodic in the initial length of spring. There is an optimal value of the spring constant. And the dependence of the current on the opposing force is reversed. Then we found that when the change of the temperature and the opposing force have optimal values, the Brownian motors can also obtain the optimal efficiency.展开更多
Directional motion of dust particles in a dusty plasma ratcnet is observed experimentally.The dusty plasma ratcnet consists of two concentric gears with asymmetric sawtooth.It is found that the sawtooth number affects...Directional motion of dust particles in a dusty plasma ratcnet is observed experimentally.The dusty plasma ratcnet consists of two concentric gears with asymmetric sawtooth.It is found that the sawtooth number affects the directional motion of dust particles along the saw channel.With the inerease of the sawtooth number,the particle velocity increases firstly and then decreases,and there is an optimum number of the sawtooth which could induce fast rotation of dust particles.The velocities of dust particles change as they are flowing along the saw channel.We also explore the force acting on the dust particle experimentally.展开更多
Using time-dependent Ginzburg-Landau formalism,we investigate the multiple reversals of ratchet effects in an unpatterned superconducting strip by the tilted dynamic pinning potential.In the case of collinear sliding ...Using time-dependent Ginzburg-Landau formalism,we investigate the multiple reversals of ratchet effects in an unpatterned superconducting strip by the tilted dynamic pinning potential.In the case of collinear sliding potential and Lorentz force,vortices are always confined in the channels induced by sliding potential.However,due to the inclination angle of sliding pinning potential with respect to the Lorentz force,vortices could be driven out of the channels,and unexpected results with multiple reversals of vortex rectifications are observed.The mechanism of multiple reversals of vortex rectifications is explored by analyzing different vortex motion scenarios with increasing ac current amplitudes.The multiple reversals of transverse and longitudinal ratchet effects can be highly controlled by ac amplitude and dynamic pinning velocity.What's more,at certain large current the ratchet effect reaches strongest within a wide range of pinning sliding velocity.展开更多
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...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.展开更多
On the basis of the double-well ratchet potential which can be calculated theoretically and implemented experimentally, the influences of the time delay, the coupling constant, and the asymmetric parameter of the pote...On the basis of the double-well ratchet potential which can be calculated theoretically and implemented experimentally, the influences of the time delay, the coupling constant, and the asymmetric parameter of the potential on the performance of a delayed feedback ratchet consisting of two Brownian particles coupled mutually with a linear elastic force are investigated. The centre-of-mass velocity of two coupled Brownian particles, the average effective diffusion coefficient, and the Pe number are calculated. It is found that the parameters are affected by not only the time delay and coupling constant but also the asymmetric parameter of the double-well ratchet potential. It is also found that the enhancement of the current may be obtained by varying the coupling constant of the system for the weak coupling case. It is expected that the results obtained here may be observed in some physical and biological systems.展开更多
A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins. Extensive Langevin simulations of the model are performed. We disc...A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins. Extensive Langevin simulations of the model are performed. We discuss the dependences of motion and efficiency on the model parameters, including the external force and the temperature. A good qualitative agreement with the expected behavior is observed.展开更多
Biomolecular motors are tiny engines that transport materials at the microscopic level within biological cells. In recent years, Elston and Peskin et al have investigated the effect of the elastic properties of the te...Biomolecular motors are tiny engines that transport materials at the microscopic level within biological cells. In recent years, Elston and Peskin et al have investigated the effect of the elastic properties of the tether that connects the motor to its cargo at the speed of the motor. In this paper we extend their work and present a tether in the form of symmetric linear potential. Our results show that when the driving mechanism is an imperfect Brownian ratchet, the average speed decreases as the stiffness of the tether increases in the limit of large motor diffusion coefficient, which is similar to the results of Elston and Peskin. However, a threshold for the stiffness of the tether connecting the motor to its cargo is found in our model. Only when the tether is stiffer than the threshold can the motor and its cargo function co-operatively, otherwise, the motor and its cargo depart from each other. This result is more realistic than that of the spring model of Elston and Peskin.展开更多
Molecular motors are proteins or protein complexes which function as transporting engines in biological cells. This paper models the tether between motor and its cargo as a symmetric linear potential. Different from E...Molecular motors are proteins or protein complexes which function as transporting engines in biological cells. This paper models the tether between motor and its cargo as a symmetric linear potential. Different from Elston and Peskin＇s work for which performance of the system was discussed only in some limiting cases, this study produces analytic solutions of the problem for general cases by simplifying the transport system into two physical states, which makes it possible to discuss the dynamics of the motor--cargo system in detail. It turns out that the tether strength between motor and cargo should be greater than a threshold or the motor will fail to transport the cargo, which was not discussed by former researchers yet. Value of the threshold depends on the diffusion coefficients of cargo and motor and also on the strength of the Brownian ratchets dragging the system. The threshold approaches a finite constant when the strength of the ratchet tends to infinity.展开更多
T7 RNA polymerase can transcribe DNA to RNA by translocating along the DNA. Structural studies suggest that the pivoting rotation of the O helix in the fingers domain may drive the movement of the O helix C-terminal T...T7 RNA polymerase can transcribe DNA to RNA by translocating along the DNA. Structural studies suggest that the pivoting rotation of the O helix in the fingers domain may drive the movement of the O helix C-terminal Tyr639 from pre- to post-translocation positions. In a series of all-atom molecular dynamics simulations, we show that the movement of Tyr639 is not tightly coupled to the rotation of the O helix, and that the two processes are only weakly dependent on each other. We also show that the internal potential of the enzyme itself generates a small difference in free energy （△E） between the post- and pre-translocation positions of Tyr639. The calculated value of △E is consistent with that obtained from single-molecule experimental data. These findings lend support to a model in which the translocation takes place via a Brownian ratchet mechanism, with the small free energy bias △E arising from the conformational change of the enzyme itself.展开更多
We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement w...We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement with the experimental data. Our study not only reveals that the maximum efficiency depends on elasticity and is independent of transition rates but also indicates that the parameters fitted to fast muscle are different from those fitted to a slow one. The latter may imply that the structure of the fast muscle is different from that of the slow one. The main reason that our model succeeds is that velocity in this model is an independent variable.展开更多
Using a dusty plasma ratchet,one can realize the rectification of charged dust particle in a plasma.To obtain the ratchet potential dominating the rectification,here we perform quantitative simulations based on a two-...Using a dusty plasma ratchet,one can realize the rectification of charged dust particle in a plasma.To obtain the ratchet potential dominating the rectification,here we perform quantitative simulations based on a two-dimensional fluid model of capacitively coupled plasma.Plasma parameters are firstly calculated in two typical cross sections of the dusty plasma ratchet which cut vertically the saw channel at different azimuthal positions.The balance positions of charged dust particle in the two cross sections then can be found exactly.The electric potentials at the two balance positions have different values.Using interpolation in term of a double-sine function from previous experimental measurement,an asymmetrical ratchet potential along the saw channel is finally obtained.The asymmetrical orientation of the ratchet potential depends on discharge conditions.Quantitative simulations further reproduce our previous experimental phenomena such as the rectification of dust particle in the dusty plasma ratchet.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52075033)Research and Development Plan of REG(Grant No.2023-20)。
文摘The railway pantograph-catenary system employs a ratchet compensation device to sustain the tension of the contact wire.However,the excessive weight associated with the ratchet structure adversely affects the performance of the compensation device.An optimization design aimed at lightweight optimization of the ratchet wheel structure can enhance the system’s agility,improve material utilization,and reduce costs.This study uses a finite element model to establish an equivalent load model for the ratchet under service conditions and analyzes its load-bearing state.An optimization model was created and solved using ANSYS Workbench.The topological optimization configurations were compared under unconstrained conditions and four different periodic constraint scenarios.Following this,the structure was redesigned based on the topological optimization results,and a simulation analysis was conducted to compare the reconstructed model with the original model.The comparison results indicate that the masses of all four optimized models have been reduced by more than 10%.Additionally,under conditions of a fully wound compensation rope,the maximum stress has decreased by over 20%,leading to a more uniform stress distribution and improved overall performance.The topology optimization and redesign method based on periodic constraints offers a viable engineering solution for the lightweight design of the ratchet structure.
文摘We presented a detailed investigation on the movement of two-headed Brownian motors in an asymmetric potential under a feedback control. By numerical simulations the direct current is obtained. The current is periodic in the initial length of spring. There is an optimal value of the spring constant. And the dependence of the current on the opposing force is reversed. Then we found that when the change of the temperature and the opposing force have optimal values, the Brownian motors can also obtain the optimal efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant No.11975089)the Program for National Defense Science and Technology Innovation Special Zone of Chinathe Program for Young Top-Notch Talents of Hebei Province of China.
文摘Directional motion of dust particles in a dusty plasma ratcnet is observed experimentally.The dusty plasma ratcnet consists of two concentric gears with asymmetric sawtooth.It is found that the sawtooth number affects the directional motion of dust particles along the saw channel.With the inerease of the sawtooth number,the particle velocity increases firstly and then decreases,and there is an optimum number of the sawtooth which could induce fast rotation of dust particles.The velocities of dust particles change as they are flowing along the saw channel.We also explore the force acting on the dust particle experimentally.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11702034,11972298,and 11702218)the China Postdoctoral Science Foundation(Grant No.2019M663812)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.300102129104,3102018zy013,and 3102017jc01003)the Young Talent Fund of University Association for Science and Technology in Shaanxi,China(Grant Nos.20180503 and 20180501).
文摘Using time-dependent Ginzburg-Landau formalism,we investigate the multiple reversals of ratchet effects in an unpatterned superconducting strip by the tilted dynamic pinning potential.In the case of collinear sliding potential and Lorentz force,vortices are always confined in the channels induced by sliding potential.However,due to the inclination angle of sliding pinning potential with respect to the Lorentz force,vortices could be driven out of the channels,and unexpected results with multiple reversals of vortex rectifications are observed.The mechanism of multiple reversals of vortex rectifications is explored by analyzing different vortex motion scenarios with increasing ac current amplitudes.The multiple reversals of transverse and longitudinal ratchet effects can be highly controlled by ac amplitude and dynamic pinning velocity.What's more,at certain large current the ratchet effect reaches strongest within a wide range of pinning sliding velocity.
基金supported by the National Natural Science Foundation of China(Grant No.11075016)the Fundamental Research Funds for the Central Universities,China(Grant No.201001)+1 种基金the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20100003110007)the Science Foundation of the Educational Department of Liaoning Province,China(Grant No.L2012386)
文摘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.
基金supported by the Foundation for the Doctoral Research Project of Shenyang Normal University,China (Grant No.054-55440107021)the Science Foundation of the Educational Department of Liaoning Province,China (Grant No.2009A646)
文摘On the basis of the double-well ratchet potential which can be calculated theoretically and implemented experimentally, the influences of the time delay, the coupling constant, and the asymmetric parameter of the potential on the performance of a delayed feedback ratchet consisting of two Brownian particles coupled mutually with a linear elastic force are investigated. The centre-of-mass velocity of two coupled Brownian particles, the average effective diffusion coefficient, and the Pe number are calculated. It is found that the parameters are affected by not only the time delay and coupling constant but also the asymmetric parameter of the double-well ratchet potential. It is also found that the enhancement of the current may be obtained by varying the coupling constant of the system for the weak coupling case. It is expected that the results obtained here may be observed in some physical and biological systems.
基金Project supported by the Educational Commission of Henan Province,China (Grant No. 2006140015)the Science and Technology Planning Project of Henan Province,China (Grant No. 092300410142)
文摘A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins. Extensive Langevin simulations of the model are performed. We discuss the dependences of motion and efficiency on the model parameters, including the external force and the temperature. A good qualitative agreement with the expected behavior is observed.
基金Project supported by the National Natural Science Foundation of China （Grant No 39970217）.
文摘Biomolecular motors are tiny engines that transport materials at the microscopic level within biological cells. In recent years, Elston and Peskin et al have investigated the effect of the elastic properties of the tether that connects the motor to its cargo at the speed of the motor. In this paper we extend their work and present a tether in the form of symmetric linear potential. Our results show that when the driving mechanism is an imperfect Brownian ratchet, the average speed decreases as the stiffness of the tether increases in the limit of large motor diffusion coefficient, which is similar to the results of Elston and Peskin. However, a threshold for the stiffness of the tether connecting the motor to its cargo is found in our model. Only when the tether is stiffer than the threshold can the motor and its cargo function co-operatively, otherwise, the motor and its cargo depart from each other. This result is more realistic than that of the spring model of Elston and Peskin.
基金supported by the National Natural Science Foundation of China (Grant No. 30600121)Doctoral Foundation of Shandong Province of China (Grant No. 2007BS09002)
文摘Molecular motors are proteins or protein complexes which function as transporting engines in biological cells. This paper models the tether between motor and its cargo as a symmetric linear potential. Different from Elston and Peskin＇s work for which performance of the system was discussed only in some limiting cases, this study produces analytic solutions of the problem for general cases by simplifying the transport system into two physical states, which makes it possible to discuss the dynamics of the motor--cargo system in detail. It turns out that the tether strength between motor and cargo should be greater than a threshold or the motor will fail to transport the cargo, which was not discussed by former researchers yet. Value of the threshold depends on the diffusion coefficients of cargo and motor and also on the strength of the Brownian ratchets dragging the system. The threshold approaches a finite constant when the strength of the ratchet tends to infinity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374352 and 11274374)the National Key Research and Development Program of China(Grant No.2016YFA0301500)
文摘T7 RNA polymerase can transcribe DNA to RNA by translocating along the DNA. Structural studies suggest that the pivoting rotation of the O helix in the fingers domain may drive the movement of the O helix C-terminal Tyr639 from pre- to post-translocation positions. In a series of all-atom molecular dynamics simulations, we show that the movement of Tyr639 is not tightly coupled to the rotation of the O helix, and that the two processes are only weakly dependent on each other. We also show that the internal potential of the enzyme itself generates a small difference in free energy （△E） between the post- and pre-translocation positions of Tyr639. The calculated value of △E is consistent with that obtained from single-molecule experimental data. These findings lend support to a model in which the translocation takes place via a Brownian ratchet mechanism, with the small free energy bias △E arising from the conformational change of the enzyme itself.
基金Project supported by the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.Y7Y1472Y61)the National Natural Science Foundation of China(Grant Nos.11205123,11574329,11774358,11747601,and 11675017)+3 种基金the Joint NSFC–ISF Research Program(Grant No.51561145002)the CAS Biophysics Interdisciplinary Innovation Team Project(Grant No.2060299)the CAS Strategic Priority Research Program(Grant No.XDA17010504)the Fundamental Research Funds for the Central Universities(Grant No.2017EYT24)
文摘We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement with the experimental data. Our study not only reveals that the maximum efficiency depends on elasticity and is independent of transition rates but also indicates that the parameters fitted to fast muscle are different from those fitted to a slow one. The latter may imply that the structure of the fast muscle is different from that of the slow one. The main reason that our model succeeds is that velocity in this model is an independent variable.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975089 and 11875014)the Interdisciplinary Research Program of Natural Science of Hebei University(Grant No.DXK202010)the Hebei Natural Science Fund(Grant Nos.A2021201003 and A2021201010)。
文摘Using a dusty plasma ratchet,one can realize the rectification of charged dust particle in a plasma.To obtain the ratchet potential dominating the rectification,here we perform quantitative simulations based on a two-dimensional fluid model of capacitively coupled plasma.Plasma parameters are firstly calculated in two typical cross sections of the dusty plasma ratchet which cut vertically the saw channel at different azimuthal positions.The balance positions of charged dust particle in the two cross sections then can be found exactly.The electric potentials at the two balance positions have different values.Using interpolation in term of a double-sine function from previous experimental measurement,an asymmetrical ratchet potential along the saw channel is finally obtained.The asymmetrical orientation of the ratchet potential depends on discharge conditions.Quantitative simulations further reproduce our previous experimental phenomena such as the rectification of dust particle in the dusty plasma ratchet.
