随机映射图的局部图

讨论了当n趋向无穷大时,n个顶点的随机映射图的k-局部图收敛于随机生长过程时刻k的二叉图,这儿,k-局部图是随机映射图前k个顶点{1,2,…,k}所生成的最小图.在这种意义下,称随机映射图为渐近二叉的.     

随机环境下堵塞可恢复的旅行者问题策略研究

针对旅行者在行走过程中遇到的某一或一系列无法预知堵塞事件的加拿大旅行者问题,考虑每个堵塞恢复时间是一个相互独立随机变量的情形,从在线问题与竞争策略的角度,给出了每个堵塞恢复时间都为正态分布下的等待策略和贪婪策略以及相应策略下的竞争比,并对两种策略的执行效果进行了分析和比较。     

随机映射图的连接概率

本文将计算随机映射图的给定顶点集的任意分类的连接概率及其极限性质,导出随机映射图的连通分支个数的分布与渐进分布．     

《高分子物理》教学中WLF方程的系数求解与分析

Williams-Landel-Ferry方程(简称WLF方程)是高分子物理中一个非常重要的经验公式。其中,C1、C2作为两个经验参数,取决于参考温度Tr的取值,且其乘积为定值(C1.C2≈900),与自由体积热膨胀系数αf有关。本文分析讨论了C1、C2参数的物理意义及C1、C2参数的两种不同求解方法,发现与由-1/logαT对1/(T-Tr)作图的方法I相比较,由-(T-Tr)/logαT对(T-Tr)作图的方法II的灵敏度更高,平均相对残差更小;正是由于对(T-Tr)变化的更高的敏感响应,导致方法II作图的线性相关性(相关系数)较低。综合C1、C2解析值的合理性和作图求解的平均相对残差,推荐采用方法II。     

室温下三光气作环合剂合成5-取代-1,3,4-噁二唑-2-酮类化合物

1,3,4-噁二唑具有抗菌,抗肿瘤,抗惊厥等生物活性~([1-6]),在药物化学方面具有重要的理论意义和实际应用价值.1,3,4-噁二唑类材料具有优良的荧光性和闪烁性和优异的电子传输性能,以及特殊的稳定性和良好的耐热性,被认为是下一代显示器件中载流子输送的首选材料~([7-8]).     

PMMI/PVDF共混体系相分离的时温依赖性

用小角激光光散射(SALLS)研究了聚(N-甲基甲基丙烯酰亚胺)/聚偏氟乙烯(PMMI/PVDF)共混体系的相分离行为.通过升温法获得了PMMI/PVDF体系的浊点温度,发现体系的浊点温度强烈依赖于升温速率,呈明显的非线性关系,即升温速率大于1 K.min-1时,升温速率是影响I(t)的唯一因素;升温速率较小时,高分子链松弛速率的差别得以体现,则该情况下升温速率与松弛速率共同影响浊点温度.该体系具有典型的最低临界共溶温度(LCST)特征.恒温法相分离结果表明,在实验温度范围内该体系相分离行为对温度的依赖性遵循时温叠加(time-temperature superposition,TTS)原理.     

聚丙烯酰胺絮凝效果的母液浓度依赖性及其影响

考察了相同剂量下不同浓度阴离子型聚丙烯酰胺絮凝剂(PAM)母液对三氧化二铁悬浮液的絮凝效果.通过电导率和流变行为测试,阐明了随母液浓度增大絮凝效果先变好后变差的原因.研究结果表明,母液浓度为0.3 g/L时PAM絮凝效果最佳.根据聚电解质标度理论及流变测试结果,认为此最佳母液浓度(cop)接近临界缠结浓度.母液电导率及加入絮凝剂后的搅拌过程中水体电导率变化表明,絮凝剂浓度高于最佳母液浓度时出现的电荷屏蔽现象使得有效电荷减少,导致高母液浓度下絮凝效果变差.向低浓度母液中添加适量β-环糊精后,环糊精分子通过氢键作用搭桥使PAM分子间距变小,发生协同絮凝形成足够大的絮体,从而使絮凝效果得到改善.这一结果表明,低于最佳母液浓度时由于PAM分子相对孤立形成的絮体不足以沉降,是导致絮凝效果较差的原因.     

Three 3D M~Ⅱ (M = Co,Ni, Zn) Supramolecular Polymers Constructed from O-vanillic Acid: Synthesis,Crystal Structure and TGA

The title compounds, [Co(H2O)6](OVA)2·2H2O 1, [Ni(H2O)6](OVA)2·2H2O 2 and [Zn(OVA)2·2H2O] 3 (HOVA = o-vanillic acid = 2-hydroxy-3-methoxybenzoate), were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR and TGA. Compounds 1 and 2 are both of triclinic with space group P1. The metal atom coordinated by six water molecules displays a slightly distorted octahedral configuration. Interestingly, the carboxyl group from HOVA ligand does not coordinate to the metal atom. Correspondingly, compound 3 belongs to the monoclinic system, space group C2/c. Each zinc(Ⅱ) atom exhibits a distorted four-coordinated tetrahedral geometry. Two monodentate carboxyl groups link one zinc(Ⅱ) atom to form a mononuclear molecule. The structure feature is different from that of compounds 1 and 2, which could be attributed to the different coordinated numbers and radii of Co(Ⅱ), Ni(Ⅱ) and Zn(Ⅱ) atoms.     

EGCG在Tween80胶束体系中的性质(英文)

通过离子萃取技术,从黄山绿茶中提取高纯度儿茶素没食子酸酯(EGCG).在Tween 80/EGCG/H2O体系中,随着EGCG浓度增加,Tween 80临界胶束浓度和胶束动力学半径增大;随着Tween 80浓度增加,EGCG和Tween 80扩散系数减小,而EGCG的紫外-可见吸收光强度和荧光强度增加.对EGCG在Tween 80胶束中的定位也进行了讨论.     

Optimization of fin geometry in heat convection with entransy theory

The entransy theory developed in recent years is used to optimize the aspect ratio of a plate fin in heat convection.Based on a two-dimensional model,the theoretical analysis shows that the minimum thermal resistance defined with the concept of entransy dissipation corresponds to the maximum heat transfer rate when the temperature of the heating surface is fixed.On the other hand,when the heat flux of the heating surface is fixed,the minimum thermal resistance corresponds to the minimum average temperature of the heating surface.The entropy optimization is also given for the heat transfer processes.It is observed that the minimum entropy generation,the minimum entropy generation number,and the minimum revised entropy generation number do not always correspond to the best heat transfer performance.In addition,the influence factors on the optimized aspect ratio of the plate fin are also discussed.The optimized ratio decreases with the enhancement of heat convection,while it increases with fin thermal conductivity increasing.