纳米铜团簇在并合过程中尺寸和温度效应的分子动力学模拟

在嵌入原子势的框架下,采用分子动力学模拟研究了不同初始温度、不同尺寸纳米铜团簇的并合过程·记录了体系在并合过程中演变的快照,计算了并合过程中与体系构形相关的几何参量,揭示并合体系的温度随时间的变化·结果表明:相同初始温度条件下,随着团簇尺寸的变小,并合程度升高,并合过程中温度上升幅度变大;对同尺寸团簇,随着初始温度的升高,并合程度提高,处于液态的团簇并合程度明显高于处于固态的团簇的并合程度·     

On Some Annihilating and Coalescing Systems

In the present paper we continue the investigation of the so-called coalescing ideal gas in one dimension, initiated by Ermakov. The model consists of point-like particles moving with velocities ±1 which coalesce and choose a fresh velocity with the same distribution when colliding. In the previous paper various identities in law were derived for the infinitely extended system. In the present paper we consider the scaling limit of the model in its various guises. The main result is the derivation of the scaling limit (invariance principle) for the joint law of an arbitrary finite number of individual particle trajectories in this system. We also obtain the scaling limit of the density profile of the system, which strongly resembles earlier results of Belitsky and Ferrari.     

用动力学夸克并合描述RHIC重离子碰撞中和各相异性流和它们的标度率

We report the results on anisotropic flows and their scaling forφmesons andΩ(Ω~- ■~ )baryons in Au Au collisions at RHIC,obtained from a dynamical quark coalescence model that uses the quark phase- space information from a multi-phase transport(AMPT)model within the string melting scenario and includes the quark structure of hadrons.     

The Discrete Coagulation Equations with Collisional Breakage

The discrete coagulation equations with collisional breakage describe the dynamics of cluster growth when clusters undergo binary collisions resulting either in coalescence or breakup with possible transfer of matter. Each of these two events may happen with an a priori prescribed probability depending for instance on the sizes of the colliding clusters. We study the existence, density conservation and uniqueness of solutions. We also consider the large time behaviour and discuss the possibility of the occurrence of gelation in some particular cases.     

Spontaneous crystallization of potassium chloride from aqueous and aqueous‐ethanol solutions; Part 3: Model of the crystallization process

A model of spontaneous crystallization process was proposed. The model describes kinetics of the crystallization process after the end of the induction period. To test the model the published earlier data on crystallization and aggregation kinetics of potassium chloride at its spontaneous crystallization from supersaturated aqueous and aqueous‐ethanol solutions were used. It was found excellent coincidence of the experimental and theoretical data on concentration of the salt and the total number of crystals in solution at crystallization. Somewhat change for the worse was at the theoretical calculations of crystal size distribution at the end of the crystallization process. It indicated that the ways of calculation of size of crystals and their weight fraction in deposit were very approximate. The model allows predicting with satisfactory accuracy kinetics of crystallization using such general parameters of potassium chloride as the specific surface energy and the height of the nucleus‐bridges between crystals at coalescence. It needs further test of the model for other salts. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

岩石裂纹演化过程中围压效应的数值模拟

应用岩石破裂过程分析程序分析了侧压对预制两个平行裂纹岩样中岩桥区裂纹的扩展、贯通和相互作用机制的影响,并对岩样。受载状态与其特征应力和峰值强度的关系进行了探讨,模拟结论与相关的实验结果相吻合。     

用于油水分离的聚结技术及其进展

对处理油水乳化液聚结分离技术的研究进展进行了综述,包括聚结床类型与材料、聚结的过程以及影响聚结性能的参数。重点介绍了多孔聚结床、颗粒聚结床和纤维聚结床的研究与应用;总结了液滴聚结过程中的接近机理、粘附机理和释放机理;详细叙述了填料表面性质、尺寸和流速、聚结床厚度、表面活性剂及其他因素对聚结性能的影响,指出了研究者对影响参数不一致甚至矛盾的结论。根据其研究状况阐述了存在的问题,其中聚结机理和影响参数需要进一步实验验证,提出了聚结技术未来研究和发展的方向。     

不完全相反转乳化过程分散相水滴形态发展研究

相反转乳化技术是制备高分子树脂水基分散体系的新方法[1～4].相反转指多组分体系(如油/水/乳化剂)中的连续相在一定条件下相互转化的过程,如在油/水/乳化剂体系中,其连续相由水相向油相(或从油相变为水相)的转变.在连续相转变区,体系的界面张力最低,因而分散相的尺寸最小.同理,可利用相反转技术直接将高分子树脂乳化为尺寸很小的水基微粒,即制备高分子树脂的水基分散体系.由于高分子树脂的粘弹性及相反转过程的复杂性,对高分子树脂的相反转乳化过程的机理研究较少.杨振忠[5]等通过调节高分子非离子型乳化剂浓度,可以有效地控制相反转完善程…     

Evolution of droplet size distribution and composition in miniemulsions

A fundamental understanding of the formation, degradation and polymerization of miniemulsions has been hindered by difficulties in quantifying their monomer droplet size distribution (DSD). In this work, particle sizing techniques including capillary hydrodynamic fractionation, acoustic attenuation spectroscopy, surfactant titration, and microscopy were adapted to characterize miniemulsion DSDs. The key ingredient in miniemulsions is the costabilizer, a low water solubility compound that limits monomer diffusion from the smaller to larger droplets (Ostwald ripening). The DSD evolution of styrene miniemulsions employing hexadecane (HD) as costabilizer was characterized. With less costabilizer, droplets were initially smaller, but increased in average size with time, and their DSDs broadened. These changes were slowed with addition of extra surfactant after homogenization. After several days, the average droplet size increased to about 150 nm regardless of the amount of HD or surfactant used. The HD content of separated portions of centrifuged miniemulsions was measured and showed significant Ostwald ripening within minutes after preparation. The further evolution of the DSD is attributed primarily to droplet coalescence. Less composition change occurred with either higher HD content or post‐homogenization surfactant addition, both of which led to minimization of free energy, increasing stability. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1529–1544     

DROPLET COLLISION AND COALESCENCE MODEL

A new droplet collision and coalescence model was presented,a quick-sort method for locating collision partners was also devised and based on theoretical and experimental results,further advancement was made to the droplet collision outcome. The advantages of the two implementations of smoothed particle hydrodynamics (SPH) method were used to limit the collision of droplets to a given number of nearest droplets and define the probability of coalescence,numerical simulations were carried out for model validation.Results show that the model presented is mesh-independent and less time consuming,it can not only maintains the system momentum conservation perfectly,but not susceptible to initial droplet size distribution as well.