Oligomer-Rich Fraction from Polydisperse Sample of Poly(bis(β-phenoxyethoxy)phosphazene)

Poly[bis(-phenoxyethoxy)phosphazene] [PBPEP] had been shown in our previous paper to be a very useful polymer for investigating the crystallization mechanism of polymers, as the crystallization rate of PBPEP is extraordinarily small when isothermally crystallized from the melt. The crystallization of the low molecular weight oligomers of PBPEP was first studied in comparison to the high molecular weight polymers. The oligomer-rich fraction was obtained by fractionation of the as-polymerized sample, which had a broad molecular weight distribution. The fractions thus obtained were characterized by solution viscometry and size exclusion chromatography. The melting temperature and the growth rate of the spherulite from the melt were investigated by differential scanning calorimetry and optical microscopy. The growth rate was one or two orders of magnitude smaller in the oligomer-rich fraction than in the other high molecular weight fractions. A collapsed spherulite appeared in the oligomer-rich fraction at high crystallization temperatures. It is speculated that in the oligomer-rich fraction there is an excess free energy due to defects in the crystal phase. This defect is considerably larger in the oligomer-rich fraction than in the other fractions because a large quantity of short length chains is present.     

13C n.m.r. study of raw materials for carbon black

¹³C n.m.r. spectroscopy has been applied to investigate a number of coal tar and petroleum-derived carbon black feedstocks. Application of the J-modulated spin echo technique is especially rewarding, as this method renders the quaternary carbons directly detectable. Thus the quality of carbon black feedstocks can additionally be gauged on the basis of the contents of quaternary carbons, which is a direct indication of the carbon yield in the carbon black production process.     

Analysis of epoxidized natural rubber. A comparative study of d.s.c., n.m.r., elemental analysis and direct titration methods

A comparative analysis of epoxidized natural rubber samples by ¹H and ¹³C n.m.r., titrimetric, elemental and d.s.c. techniques has been made. Whereas the titrimetric method is only applicable at low epoxy contents (< 15 mol%) both n.m.r. methods give reasonable precision over the compositional range of 20–75 mol%. Elemental analysis appears less reliable. D.s.c. analysis through measurement of T_g provides the highest precision of measurement but requires independent calibration by one or more of the primary methods. The epoxy content may also be related to the polymer density.     

The influence of an intermediate MoO3 layer on the solid state reaction of cobalt oxide withγ-Al2O3

In view of the importance for Co_xO_y,-MoO₃/-Al₂O₃ hydrodesulphurization (HDS) catalysts, the reactivity of cobalt oxide layers towards cobalt aluminate formation was investigated on both MoO₃-covered and bare -Al₂O₃ substrates. Co₃O₄/MoO₃/-Al₂O₃ and Co₃O₄/-Al₂O₃ systems were prepared by vapour-deposition of MoO₃ (12 × 10¹⁵ Mo atoms/cm²) and Co (400 × 10¹⁵ Co atoms/cm²) layers onto a -Al₂O₃ substrate, followed by oxidation of the Co layer to Co₃O₄. After annealing at 800°C for 40 h, the interfacial reaction to cobalt aluminate was assessed using Rutherford backscattering spectrometry. The presence of molybdenum oxide appeared to enhance cobalt aluminate formation. The Mo atoms, which spread out over the entire cobalt-containing layer, presumably caused a high defect density, which explains the observed higher reaction rate. The amount of MoO₃ was much too low to stabilize all cobalt atoms by cobalt molybdate formation.     

7.63m特大型焦炉砌筑施工技术及要点

主要针对7.63m特大型焦炉砌筑施工技术,从工程实践效果分析其施工技术在质量、工期、成本等方面收到良好的经济效益和社会效益,现对7.63m特大型焦炉施工技术作简要介绍。     

掺Er^3＋镓磷酸盐玻璃的光学性质

利用熔融淬火法制备了摩尔分数为40．8Ga2O3-58．0NaPO3-1．2Er2O3掺Er^3＋镓磷酸盐玻璃,测试并研究了样品中Er^3＋的吸收光谱、1．5μm发射光谱,根据Judd-Ofelt理论计算了Er^3＋离子强度参量Ωt（t=2,4,6）及自发辐射概率、荧光分支比、自发辐射寿命．结果表明,Er3＋1．5μm发射光谱半峰全宽达到40nm．同时,利用McCumber方法计算了Er^3＋4 I13／2→^4I15／2跃迁的受激发射截面,峰值达到6．10×10^-21cm^2,测定了Er^3＋4I13／2能级荧光寿命为4．88ms,^4I13／2能级量子效率为56．3％．     

缺失数据下m相依样本的大样本性质

讨论了缺失数据在随机补充方式下均值的估计,证明了估计的相合性和渐进正态性,并给出了经验似然比统计量的渐进分布．     

多步自适应组合预测及其应用

提出一种多步自适应组合预测方法.预测由多个并行不同的多步自适应预测模型组成,最终预测结果,由多个预测模型预测值的线性加权组合决定.本法适用于随机时变动态系统过程的多步预测问题,在某省粮食产量趋势预测中,应用此法获得了良好的效果.     

基于企业核心竞争力的中部企业“多梯制”人才发展通道研究

从提高中部企业核心竞争力的角度出发,对中部企业人才发展通道不畅的现状和原因进行分析,提出建立管理人才、技术人才和技能人才“多梯制”发展通道的构想,试图通过充分发挥人才资源的作用来有效整合其内部和外部的各种资源,不断推陈出新,提升企业的核心竞争力,使中部企业在日益激烈的市场竞争中始终立于不败之地,实现中部地区的快速崛起。     

住宅设计原理——“住”的思考

居住类建筑一直是建筑设计人员关注的重点,关于"住"的思考人们也从未停歇过,将结合一些流行的住宅设计观点展开对于"住"的思考.