反渗透过程中双壁碳纳米管通水阻盐性能的分子动力学模拟

采用分子动力学模拟方法, 探究了非常规双壁碳纳米管(DWCNT)在反渗透过程中, 不同内外管间距对管道内水分子与盐离子运动行为的影响. 本文采用0.5 mol·L^-1氯化钠水溶液模拟海水, 内管始终采用CNT(8,8)型, 并对盐水层施加恒力模拟反渗透压. 重点考察盐离子数量分布与通水情况, 计算水分子平均力势, 并分析水分子氢键寿命与偶极矩分布. 结果表明, 管间距不仅影响上述各项性质, 还会改变盐离子与水分子在碳管中的渗透特性. 模拟结果显示, 小尺寸DWCNT可以有效实现盐水分离但水通量较小, 大尺寸DWCNT的水容量较大但阻盐效率不高, 而中尺寸DWCNT (即: 管间距为0.815 nm)则具有最佳的通水阻盐性能. 本文试图从分子层面揭示了DWCNT通水阻盐机理, 并为人们设计新型海水淡化渗透膜提供理论指导.     

柔性棘轮在活性粒子浴内的自发定向转动

活性物质在自然界中广泛存在.利用二维布朗动力学模拟方法,设计了一种柔性边界棘轮,并研究了其在活性粒子浴内的动力学行为.发现棘轮在活性粒子浴内能够发生定向转动,这是因为活性粒子在柔性边界周围的不均匀分布导致压力的不均匀分布,进而对棘轮产生扭矩.进一步研究了影响转动速率的因素,发现平均转动角速度随活性粒子驱动力、活性粒子密度的增大而增大,随粒子旋转扩散系数、支架数的增大而降低.研究结果对于设计新的实验系统来研究此类非平衡物理现象具有一定的指导意义.     

Self-adaptive behavior of nunchakus-like tracer induced by active Brownian particles

We design a nunchakus-like tracer and investigate its self-adaptive behavior in an active Brownian particle (ABP) bath via systematically tuning the self-propelled capability and density of ABPs. Specifically, the nunchakus-like tracer will have a stable wedge-like shape in the ABP bath when the self-propelled force is high enough. We analyze the angle between the two arms of the tracer and the velocity of the joint point of the tracer. The angle exhibits a non-monotonic phenomenon as a function of active force. However, it increases with density of ABPs increasing monotonically. A simple linear relationship between the velocity and the self-propelled force is found under the highly active force. In other words, the joint points of the tracer diffuse and the super-diffusive behavior can make the relation between the self-propelled force and the density of ABPs persist longer. In addition, we find that the tracer can flip at high density of ABPs. Our results also suggest the new self-adaptive model research of the transport properties in a non-equilibrium medium.