Phase behavior of amphiphiles at liquid crystals/water interface: A coarse-grained molecular dynamics study

We present a coarse-grained molecular dynamics simulation study of phase behavior of amphiphilic monolayers at the liquid crystal （LC）/water interface. The results revealed that LCs at interface can influence the lateral ordering of amphiphiles. Particularly, the amphiphile tails along with perpendicularly penetrated LCs between tails undergo a two-dimension phase transition from liquid-expanded into a liquid-condensed phase as their area density at interface reaches 0.93. While, the liquid-condensed phase of the monolayer never appears at oil/water interface with isotropic shape oil particles. These findings reveal the penetration of anisotropic LC can promote ordered lateral organization of amphiphiles. Moreover, we find the phase transition point is shifted to lower surface coverage of amphiphiles when the LCs have larger affinity to the amphiphile tails.     

粗信息矩阵的数量特征

利用已给出粗信息矩阵及粗集的有关理论,提出并研究了粗信息矩阵的两个数量特征--粗牲度短阵及粗精度矩阵,给出了一系列性质及定理.     

并行Pareto多目标演化算法

提出并实现了一个并行Pareto多目标演化算法(PPMEA)，PPMEA算法是一个通过演化算法来解决基于Pareto的多目标优化问题的并行计算模型。在这个算法中，采用了并行演化算法中常用的全局并行模型和粗粒度并行岛模型。构成每个岛的子群体以不同的杂交概率和变异概率各自独立的演化，但是每隔一定的代数它们要交换外部集中的个体。标准测试函数的数值实验结果表明，所提出的算法能够使找到的解集快速收敛到Pareto非劣最优目标域，并且解集沿着Pareto非劣最优目标域有很好的扩展性。     

纤维素二级结构的分子动力学模拟

运用分子动力学模拟的方法,详细研究了ˉ-纤维素的二级结构.随着糖链数量的增加,纤维素也变成螺旋型结构. 当糖链数量为6、24和36时,纤维素的结构为右手螺旋. 但是,当糖链数量为8、12、16,时,纤维素的结构为左手螺旋. 计算还表明,当糖链数量为36时,结构最稳定.     

聚合物与表面活性剂相互作用的分子模拟研究进展

聚合物与表面活性剂复配体系已广泛应用于医药、生物、石油石化等领域。从微观上认识其相互作用机理对指导其生产实际有着重要作用,因而此方面的研究倍受关注。随着分子模拟技术的发展,聚合物与表面活性剂在分子水平上的相互作用机理研究已经被广泛开展,并获得了大量有用的信息。本文综述了耗散粒子动力学(DPD)和粗粒度分子动力学(CG-MD)在聚合物与表面活性剂相互作用方面的应用,分别对中性聚合物与离子型表面活性剂,以及带相反电荷的聚电解质和表面活性剂在溶液相和界面相的相互作用进行了阐述,并揭示了聚合物/表面活性剂聚集体结构形态的变化规律。     

Coarse-Grained Langevin Approximations and Spatiotemporal Acceleration for Kinetic Monte Carlo Simulations of Diffusion of Interacting Particles

Kinetic Monte Carlo methods provide a powerful computational tool for the simulation of microscopic processes such as the diffusion of interacting particles on a surface, at a detailed atomistic level. However such algorithms are typically computationatly expensive and are restricted to fairly small spatiotemporal scales. One approach towards overcoming this problem was the development of coarse-grained Monte Carlo algorithms. In recent literature, these methods were shown to be capable of efficiently describing much larger length scales while still incorporating information on microscopic interactions and fluctuations. In this paper, a coarse-grained Langevin system of stochastic differential equations as approximations of diffusion of interacting particles is derived, based on these earlier coarse-grained models. The authors demonstrate the asymptotic equivalence of transient and long time behavior of the Langevin approximation and the underlying microscopic process, using asymptotics methods such as large deviations for interacting particles systems, and furthermore, present corresponding numerical simulations, comparing statistical quantities like mean paths, auto correlations and power spectra of the microscopic and the approximating Langevin processes. Finally, it is shown that the Langevin approximations presented here are much more computationally efficient than conventional Kinetic Monte Carlo methods, since in addition to the reduction in the number of spatial degrees of freedom in coarse-grained Monte Carlo methods, the Langevin system of stochastic differential equations allows for multiple particle moves in a single timestep.     

一种粗粒度并行遗传算法及其应用

提出一种粗粒度并行遗传算法 ,采用多种群遗传策略 ,在逐渐收缩的空间上搜索 ,并且用准精确惩罚函数处理约束 ,保证了算法稳定而迅速地收敛于全局最优解。本文还讨论了算法的分布式计算策略 ,并行计算是在天潮 1 0 0 0 (A)超级并行计算机上完成的 ,利用 PVM系统处理各个处理器间的通讯。算例显示了本算法的计算效率和加速比。     

Coarse-Grained Molecular Dynamics Simulation of a Red Blood Cell

A worm-like chain model based on a spectrin network is employed to study the biomechanics of red blood cells. Coarse-grained molecular dynamics simulations are performed to obtain a stable configuration free of external loadings. We also discuss the influence of two parameters： the average bending modulus and the persistence length. The change in shape of a malaria-infected red blood cell can contribute to the change in its molecular-based structure. As the persistence length of the membrane network in the infected red blood cell decreases, the deformability decreases and the biconcave shape is destroyed. The numerical results are comparable with previously reported experimental results. The coarse-grained model can be used to study the relationship between macro-mechanical properties and molecular-scale structures of cells.