LIMITING BEHAVIOR OF UNIFORM RECURSIVE TREES

The authors consider the limiting behavior of various branches in a uniform recursive tree with size growing to infinity.The limiting distribution ofζ_(n,m),the number of branches with size m in a uniform recursive tree of order n,converges weakly to a Poisson distribution with parameter 1/m with convergence of all moments.The size of any large branch tends to infinity almost surely.     

A Novel Method to Synthesize Polyorganozircosilazane

A new kind of polyorganozircosilazane as Si/Zr/C/N-based ceramic precursor was synthesized from the condensation reaction of hexamethyleyclotrisilazane lithium salts(D3^NLi）and zirconium tetrachloride(ZrCl4).In the presence of N,N,N’,N’-tetramethyl ethylene diamine(TMEDA),polyorganozircosilazane was obtained in high yield.     

a-Si:H掺杂机理的研究

本文利用CNDO/2量子化学理论方法,对P和B原子在四面体配位的Si₄₆和Sl₄₆H₆₀H₄^*原子集团中置换Si原子前后的原子集团能量和能态分布变化进行了计算.计算结果表明:1)在Si₄₆H₆₀H₄^*原子集团中用P(或B)置换引Si原子后在能隙中明显地出现施主(或受主)态子带,同样在Si_{46相似文献}   

聚合物电致发光材料研究进展

本文较详细地综述了聚合物电致发光材料的研究进展，重点介绍了聚对苯撑乙烯（ＰＰＶ），并提出了有关聚合物电致发光材料及器件构造研究的一些观点。     

微波常压法合成水杨酸酯

在浓硫酸催化下，采用微波常压法由水杨酸分别与正丁醇、异丁醇、正戊醇和异戊醇反应合成相应的水杨酸酯。结果表明：当水杨酸：醇：Ｈ２ＳＯ４＝１：５．５：０．３（摩尔比）时，采用５６０Ｗ微波辐射２２ｍｉｎ，水杨酸酯的产率可达８８．７％￣９６．４％，反应速度至少是常规反应的１４倍。     

The Electrochemical Investigation of MEH-PPV in Ionic Liquid

Ionic liquids are a new kind of room-temperature molten organic salts. It can be used as solvents in the organic/polymeric syntheses, and some of them are called "green" solvents because of its recyclability1. Ionic liquids possess the superior properties, such as thermal stability up to 200(C, involatility and re-designability(for both cation and anion). The ionic liquid employed in this work is [bmim] [PF6]- ( butylmethylimidazolium hexafluorophosphate ) which is immiscible with water and h…     

过渡金属钼钒砷杂多化合物的合成与TPR,TPD研究

Seven transition metal molybdovanadoarsenic heteropoly compounds have been synthesized and characterized using IR, UV, TG-DTA, pH potential titration techniques. The molecular formulae of these compounds are pro-posed to be H_xM_yAsMO₁₀V₂O₄₀·zH₂O(x=1～3, y=1,2, M=Cr, Mn, Fe, Co, Ni, Cu, Zn).They are all keggin structure. Surface nature of these compounds have been investigated by temperature programmed desorption and temperature programmed reduction techniques. NH₃-TPD results show that in TPD profiles of the compounds there are two desorption peaks corresponding to weak acid sites of desorption, respectively. Desorbing activativon energy and preexponential factor of weak acid site of desorption for compounds have been calculated. H₂-TPR re-sults show that introducting transtion metal to molybdovanarsenic acid, the reduction peak temperatures of H₂-TPR shift regularly with increasing d electron numbers of transition metals. In addition, Zn and Cu heteropoly com-pounds have yet apparent effect of hydrogen spill over.     

Li^＋／MgO上乙烷氧化脱氢制乙烯的研究（Ⅱ）：催化作用机理

借助ＸＲＤ、ＩＲ、ＴＧ等技术对Ｌｉ＾＋／ＭｇＯ进行了表征，结果表明，酸、碱中心的数目，强度、催化性与Ｌｉ＾＋的添加量相关 ，起酸碱作用的表面金属离子、表面低配位氧集团、Ｏ（Ｌ ｉ＾＋Ｏ＾－）是其反应的活性物种，反应机理可能由离子基、游离基协同完成。     

铜基甲醇合成催化剂TPR导数谱

铜基甲醇合成催化剂ＴＰＲ导数谱胡云行，万惠霖，蔡启瑞（厦门大学化学系，固体表面物理化学国家重要实验室，厦门，３６１００５）关键词ＴＰＲ，导数谱，铜基催化剂ＴＰＲ是非稳态条件下研究催化剂的有效方法。该法具有设备简单、快速和信息量大等特点，已成为常用的催...     

(4S)-4-羧基杂氮硅三环的合成

利用L-N,N-双(β-羟乙基)丝氨酸及L-N,N-双(β-羟乙基)苏氨酸与三乙氧基硅烷或氯烷基三乙氧基硅烷反应合成了具有手性的(4S)-4-羧基杂氮硅三环(1～5),并运用IR、~1HNMR、EI-MS等手段表征了结构。证据显示存在着贯穿笼状结构的N→Si配键。