不同结构芳香侧链酰基牛磺酸钠的表面扩张性质

利用悬挂滴方法研究了N-(α-苯氧基)十四酸牛磺酸钠(12+B-T)和N-(α-对乙基苯氧基)十四酸牛磺酸钠(12+2B-T)在空气/水表面上的动态扩张粘弹性质, 考察了时间、扩张频率及摩尔浓度对扩张模量和相角的影响, 测定了不同摩尔浓度条件下的泡沫性能. 研究发现: 低浓度条件下, 表面分子间相互作用决定表面活性剂吸附膜的性质, 膜以弹性为主; 高浓度条件下, 扩散交换过程起主导作用, 吸附膜表现出粘弹特性. 表面活性剂芳环支链上增加一个乙基, 分子间相互作用增强, 扩张模量增大, 泡沫更加稳定.     

Analytical results for the cluster size distribution in controlled deposition processes

This paper proposes a controlled particle deposition model for cluster growth on the substrate surface and then presents exact results for the cluster (island) size distribution. In the system, at every time step a fixed number of particles are injected into the system and immediately deposited onto the substrate surface. It investigates the cluster size distribution by employing the generalized rate equation approach. The results exhibit that the evolution behaviour of the system depends crucially on the details of the adsorption rate kernel. The cluster size distribution can take the Poisson distribution or the conventional scaling form in some cases, while it is of a quite complex form in other cases.     

阴离子表面活性剂在水/正烷烃界面的分子动力学模拟(英文)

利用分子动力学模拟方法研究了阴离子表面活性剂在水/正烷烃(壬烷,癸烷和十一碳烷)界面的结构和动力学特点.十六烷基苯磺酸钠作为研究对象,其中苯磺酸基团在十六碳烷的第4号碳原子上,记作4-C16.分析了不同油相和特定盐度条件下正烷烃-表面活性剂-水体系的界面特点(如密度剖面图、界面张力和径向分布函数).模拟结果表明平衡模型体系展现了一个很好的水/正烷烃界面.当加氯化钠到水溶液中,正烷烃-表面活性剂-水体系的界面张力有微小的变化,有趣的是表面活性剂二面角的反式结构分数的变化联系着界面张力的微小变化.可见,表面活性剂在界面处的结构对降低界面张力起到重要的作用.此外,还发现表面活性剂的极性头与钠离子和水分子存在较强的相互作用.     

中国人口分布规律及演化机理研究

近20年来,中国的总人口近似地按指数规律增加,但增加的速度有减缓的趋势.省、市、县三级的人口分布具有相似的规律：人口数k小的各级人口分布随k缓慢地变化;而k较大时,人口分布随k急剧变化,满足齐普夫定律.研究结果表明中国人口系统的各级分布具有自相似性.采用无标度网络上的聚集体迁移模型较好地解释了中国人口分布的演化规律. 关键词： 人口分布 齐普夫定律 迁移 动力学行为     

Thresholds and Universality of the Site Percolation on the Sierpinski Carpets

Following the methods proposed by Yonezawa, Sakamoto and Hori, we have calculated the percolation thresholds P_c, their error bars ΔP_c, and the correlation length exponents v of a family of the Sierpinski carpets for the site percolation problems by making use of MonteCarlo simulations and finite size scaling. We have found the dependence of P_c and v on the fractal dimensionality D_f and the lacunarity. We ascertain that the site percolation problems on a family of Sierpinski carpets with central cutouts and different D belong to different universal classes, and those on Sierpinski carpets with same D_f but of different lacunarities belong to different universal classes.     

Monomer Migration and Annihilation Processes

We propose a two-species monomer migration-annihilation model, in which monomer migration reactions occur between any two aggregates of the same species and monomer annihilation reactions occur between two different species. Based on the mean-field rate equations, we investigate the evolution behaviors of the processes. For the case with an annihilation rate kernel proportional to the sizes of the reactants, the aggregation size distribution of either species approaches the modified scaling form in the symmetrical initial case, while for the asymmetrical initial case the heavy species with a large initial data scales according to the conventional form and the light one does not scale. Moreover, at most one species can survive finally. For the case with a constant annihilation rate kernel, both species may scale according to the conventional scaling law in the symmetrical case and survive together at the end.     

Analytical Results of a Two-Species Predator-Prey Model

We propose a sequential monomer reaction model for a two-species predator-prey system, in which the aggregates of either species can spontaneously produce or lose one monomer and meanwhile, a type-B aggregate can prey upon one monomer of a type-A aggregate when they meet. Using the mean-field rate equation approach, we analytically investigate the kinetic behavior of the system. The results show that the evolution of the system depends crucially on the details of the rate kernels. The aggregate size distribution of either species approaches the conventional or modified scaling form in most cases. Moreover, the total size of either species grows exponentially with time in some cases and asymptotically retains a constant quantity in other cases, while it decays with time and vanishes finally in the rest cases.     

Aggregation Processes with Catalysis-Driven Decomposition

We propose a three-species aggregation model with catalysis-drivendecomposition. Based on the mean-field rate equations, weinvestigate the evolution behavior of the system with thesize-dependent catalysis-driven decomposition rate J(i;j;k)=J ijk^v and the constant aggregation rates. The results show that the cluster size distribution of the species without decomposition can always obey the conventional scaling law in the case of 0≤ v ≤1, while the kinetic evolution of the decomposed species depends crucially on the index v. Moreover, the total size of the species without decomposition can keep a nonzero value atlarge times, while the total size of the decomposed speciesdecreases exponentially with time and vanishes finally.     

凝胶网格沉淀法制备MgO纳米晶

Monodispersed spherical MgO nanocrystallites were successfully prepared by a novel gel-network precipitation process. The face-centred cubic samples were with narrow size distribution of 10～15 nm. The formation process and structure of MgO nanocrystallites were investigated by means of TG-DTA, FTIR, XRD and TEM. The results show that the particle sizes are related to the network structure of gelatin, not only can the shapes and sizes of nanocrystallites be controlled, but the aggregation and agglomeration can be prevented by gel-network. The products have smaller particle size and better homogeneity.     

外场中分形晶格上Gauss模型的临界现象

在分形晶格上把Gauss模型加以推广 ,认为Gauss分布常数和重整化的外磁场都依赖于晶格格点的配位数 ,且格点i和j上的Gauss分布常数b _qi 和bb_qj 满足关系b_qi b_qj = q_i q_j (q_i 和q_j分别是格点i和j的配位数 ) .利用实空间重整化群变换的方法 ,在Koch型曲线和一族钻石型等级 (DH)晶格上计算了外场中Gauss模型的临界点和临界指数 .结果表明 :对于这些晶格 ,在临界点 ,格点近邻相互作用参量和外磁场都可表示为K =b_qi q_i 和h q_i =0的形式 ,h_qi 是格点i上的简化磁场 ,而临界指数则决定于分形系统的分形维数d_f;另外 ,对于DH晶格 ,临界指数与平移对称晶格上的结果完全相同 ,且在d_f=4时和平均场理论的结果完全一致