非对称双原子分子在输运扩散中的取向效应

本文建立了同时具有化学势梯度和温度梯度的非平衡系统，研究非对称双原子分子的输运扩散行为.研究发现，双原子分子在非平衡输运中具有取向效应.浓度梯度与温度梯度使双原子分子在输运中产生的大小原子取向的方向刚好相反，沿着梯度的正方向，前者使小原子在前，后者使大原子在前.通过最小熵产生原理，解释了取向的物理机制.研究结果对于深刻理解非平衡条件下物质的输运与其形态的关系具有理论意义.     

Ratchet transport of self-propelled chimeras in an asymmetric periodic structure

We studied the rectified transport of underdamped particles subject to phase lag in an asymmetric periodic structure. When the inertia effect is considered, it is possible to observe reversals of the average velocity with small self-propelled force, whereas particles always move in the positive direction with large self-propelled force. The introduction of phase lag leads particles to follow circular orbits and suppress the polar motion. In addition, this can adjust the direction of particle motion. There exists an optimal value of polar interaction strength at which the rectification is maximal. These results open the way for many application processes, such as spatial sorting of particles mixture and separation based on their physical properties.     

非对称双链分子结构的热整流效应

采用非平衡分子动力学方法,研究由Frenkel-Kontorova模型构建的非对称双链分子结构体系,并考察了温度、链内耦合强度、链间耦合强度以及系统尺寸对体系的热整流效应的影响. 研究表明,低温下非对称双链体系表现出热整流效应;在一定的范围内,链间的耦合和链内的耦合强度越强,体系的热整流效果就越好;随着系统尺寸的增大,热整流效率先减小后增加,最后达到稳定. 非对称双链结构的链接粒子的功率谱行为与单链情形相似,其可以用于对热整流效应的解释. 关键词： 双链分子结构 热整流 Frenkel-Kontorova模型 链间相互作用     

狭窄程度对锥缩血管中脉动流的影响

建立了一个轴对称的狭窄锥缩刚性动脉模型.利用不可压缩的N-S方程作为计算的理论基础,采用有限差分方案进行数值分析.提供了3种狭窄程度下的管壁切应力分布曲线并进行了分析和比较,同时给出了模型M3(h R0=1 3)在一个流动周期内的流线图.结果显示狭窄附近的流场受到了干扰,特别是狭窄的喉部及其下游区域的流场,并且狭窄程度越严重,狭窄对流场的影响就越大.     

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.     

Particle Transport with Asymmetric Unbiased Forces and Entropic Barrier

Transport of a Brownian particle moving along the axis of a three-dimensional （313） 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.     

过阻尼布朗棘轮的斯托克斯效率研究

根据随机能量理论解析得到阻尼环境中布朗粒子的概率流和斯托克斯效率，并进一步研究布朗粒子的输运性能.详细讨论了空间的不对称性、外偏置力及外势结构等对棘轮定向输运的影响.研究发现，合适的外偏置力能使棘轮的定向输运达到最强.通过调节外势的不对称性可使棘轮中粒子的运动反向，当选择合适的空间不对称性时布朗粒子的反向输运可获得最强.此外，一定条件下合适的外势高度也能增强棘轮输运，且能使粒子克服黏滞阻力的斯托克斯效率达到最大.所得结论能够启发实验上设计合适的外势及外偏置来优化布朗棘轮的定向输运性能，并为生物纳米器件的研制提供一定的理论参考.     

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.     

σ介子的自相互作用对核物质物态方程的影响

在相对论σ–ω模型里,详细讨论了σ介子的自相互作用参数对正常核物质物态方程的影响,特别是对核物质的不可压缩系数、有效质量,以及σ介子与核子、ω介子与核子之间的耦合常数的影响,发现这些参数与核物质的性质之间有紧密的联系.同时,利用这些结果研究了相对论σ–ω–π模型下△共振态核物质的结合能和压强与温度之间的关系,并同我们以前的结果作了比较,得到了一些有意义的结果.在以上所有的分析中,考虑了核子、△粒子和σ介子的真空起伏.     

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.