Cationic ring-opening polymerization of hexamethylcyclodisilazane: General aspects and tentative mechanisms

The ring-opening polymerization of hexamethylcyclodisilazane (D_2NMe), initiated by methyl triflate in 1,2-dichloroethane, forms in the first, fast kinetic step both linear polymer and cyclic dimer (D_4NMe). Subsequently a slow depolymerization process occurs leading to exclusively cyclotrisilazane (D_3NMe). On the basis of kinetic measurements carried out using an adiabatic calorimetric technique and complementary experiments, mechanisms of both propagation, cyclization and back-biting reactions are proposed. The influence of the reaction temperature was also studied; it is demonstrated that, at low temperature, polymerization does not lead to cyclic oligomer formation. In such conditions, the polymerization presents a ‘living’ character.     

光纤码分多址技术在城域接入网中的应用

分析了光纤码分多址技术O -CDMA在城域接入网中的应用。回顾了O -CDMA技术的发展历史 ,详细地介绍了O -CDMA技术的特点 ,其具有的公平性、灵活性、网络控制管理、对服务区处理能力以及高的安全性使O -CDMA技术成为较好的城域接入网技术。阐述了目前在应用中O -CDMA存在的一些技术方面的问题     

Validation of a Three-Dimensional Computational Fluid Dynamics Model of a Contact Tank

A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field.     

龙滩尾水出口枯期围堰设计与施工

介绍龙滩水电站尾水出口工程枯期围堰的设计参数及计算过程,结合施工过程中的实际情况,总结得出土石子围堰的闭气方法和浆砌石主围堰堰体防渗的应注意几个问题。     

Effects of multiple weak interactions on the binding of phenolic compounds by polymeric adsorbents

To investigate the effects of multiple weak interactions on the binding of phenolic compounds by polymeric adsorbents, macroporous polystyrene (PS) resin and PS‐based adsorbents with different hydrogen‐bond acceptor atoms (PS CH₂( OCH₂CH₂)_n OCH₃, n = 0, 1, 2, and 3, denoted as PS‐EG₀, PS‐EG₁, PS‐EG₂, and PS‐EG₃) were prepared. The phenol adsorption strength order on these adsorbents was PS/PS‐EG₀ < PS‐EG₁ < PS‐EG₂ < PS‐EG₃, indicating that the adsorption on PS and PS‐EG₀ was driven by hydrophobic and π–π interactions, and the adsorption on PS‐EG₁, PS‐EG₂, and PS‐EG₃ was driven by a hydrogen bond in addition to hydrophobic and π–π interactions. PS‐EG₂ may adsorb a second phenol molecule on each binding site and PS‐EG₃ may adsorb second and third ones. The adsorption strength of resorcinol increased in the order of PS, PS‐EG₁, and PS‐EG₂, indicating that the adsorption was driven by 0, 1, and 2 hydrogen bonds in addition to hydrophobic and π–π interactions. Similarly, the adsorption of phloroglucinol on PS, PS‐EG₁, PS‐EG₂, and PS‐EG₃ was driven by 0, 1, 2, and 3 hydrogen bonds in addition to hydrophobic and π–π interactions because the adsorption strength increased in this order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4652–4658, 2006     

模块化蓝光光存储性能静态测试系统

蓝光光存储是信息存储领域发展的一个重要方向。测试系统是研究蓝光光存储材料的必备条件，为建立蓝光光存储研究平台，设计和搭建了一套模块化蓝光光存储性能静态测试系统。激光工作波长为406．7nm。系统采用调制解调技术降低系统噪声，提高测量粘度：采用光点移动模式降低对样品尺寸的要求；采用纳米平台提高记录点的反复定位性能。实验结果证明测试系统性能良好，可以满足蓝光光存储性能静态测试要求。     

紫金山金矿低品位资源开发的地质技术研究

介绍了紫金山金矿床赋存的基本特征；重点阐述了生产探矿增加储量．扩大矿床规模，建立低品位矿开发蛭济模型和责源评价软件系统研制等系列地质技术研究与创新成果：强调了加大经济与科技投入．对矿山的发展有重大意义。     

大型压力容器现场热处理技术

以大连石化350万t/a催化裂化装置再生器为例,研究开发大型炼油化工设备现场新型热处理工艺。通过设置必要的热气流导向装置,采用微正压内燃工艺,配备新型大功率燃油喷嘴、用DCS集散控制系统调节油风比例和烟囱热量排放张合度,对超厚壁板适当增加电加热辅助热处理,解决了大容积、变截面、不等壁厚、超重设备施工现场热处理温度调整难度大、不均衡等技术问题。实践证明,应用该技术进行热处理,具有工期短、效果好、经济效益明显等特点。     

正确处理三种关系,促进测量学教学健康发展--非测绘专业测量学的教学研究

结合教学实践，对如何正确处理好教学与科研、传统技术与新技术、传统教学与多媒体教学之间的关系进行了研究，并得出正确处理好这三种关系是促进测量学教学健康发展和提高教学质量的有效途径的结论。     

茨21-133井CO2吞吐技术初步试验

茨榆坨油田茨13块原油属于普通稠油，1993年开始蒸汽吞吐采油，从第二轮开始效果明显变差，注汽返排率低，有效周期短，产量下降快，套管变形井增多。针对这些问题，在该区块茨21—133井进行CO2吞吐采油工艺现场试验，获得成功，增油效果明显。