Thaumasite––direct, woodfordite and other possible formation routes

Two main formation routes for thaumasite exist below 15 °C. One is the direct route from C–S–H reacting with appropriate carbonate, sulfate, Ca²⁺ ions and excess water. The other route is the woodfordite route from ettringite reacting with C–S–H, carbonate, Ca²⁺ ions and excess water, in which thaumasite arises through the intermediate formation of the solid solution woodfordite. The woodfordite route for thaumasite formation appears to be relatively quicker (although still slow) than the direct route, presumably because with the former the ettringite already has the octahedral [M(OH)₆] units that can facilitate the critical change from [Al(OH)₆]³⁻ to [Si(OH)₆]²⁻ groupings. Both routes are mutually dependent on each other. The presence of magnesium salts can modify the path to thaumasite formation. High pressure might be able to stabilise [Si(OH)₆]²⁻ groupings and allow thaumasite to become formed above 15 °C. This possibility is discussed.     

3G网络中的IPv6 DNS服务器配置

说明了3G网络中IPv6递归DNS服务器地址配置的三种方法：路由器通告（RA）方案，DHCPv6方案，递归域名系统（DNS）服务器的公认任播地址方案，详细地说明了三种解决方案的操作特点。本文为3G中选择合适的方法进行主机DNS配置提供了指导。     

从RC5到RC6

论文详细描述并分析了从RC5到RC6的演化设计过程,在详细研究了RC6性能的同时,指出了应该如何从一个旧的密码设计出好的新密码。最后对RC6和Rijndael作了一些比较,指出各自在性能上的优缺点。     

Biotransformation of l‐menthol by twelve isolates of soil‐borne plant pathogenic fungi (Rhizoctonia solani) and classification of fungi

The microbial transformation of l‐menthol ( 1 ) was investigated by using 12 isolates of soil‐borne plant pathogenic fungi, Rhizoctonia solani (AG‐1‐IA Rs24, Joichi‐2, RRG97‐1; AG‐1‐IB TR22, R147, 110.4; AG‐1‐IC F‐1, F‐4, P‐1; AG‐1‐ID RCP‐1, RCP‐3, and RCP‐7) as a biocatalyst. Rhizoctonia solani F‐1, F‐4 and P‐1 showed 89.7–99.9% yields of converted product from 1 , RCP‐1, RCP‐3, and RCP‐7 26.0–26.9% and the other isolates 0.1–12.0%. In the cases of F‐1, F‐4 and P‐1, substrate 1 was converted to (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol ( 2 ), (?)‐(1S,3R,4S)‐1‐hydroxymenthol ( 3 ) and (+)‐(1S,3R,4R,6S)‐6,8‐dihydroxymenthol ( 4 ), which was a new compound. Substrate 1 was converted to 2 and/or 3 by RRG97‐1, 110.4, RCP‐1, RCP‐3 and RCP‐7. The structures of the metabolic products were elucidated on the basis of their spectral data. In addition, metabolic pathways of the biotransformation of 1 by Rhizoctonia solani are discussed. Finally, from the main component analysis and the differences in the yields of converted product from 1 , the 12 isolates of Rhizoctonia solani were divided into three groups based on an analysis of the metabolites. Copyright © 2003 Society of Chemical Industry     

癸二酸二甲酯与1,2,2,6,6-五甲基哌啶醇的酯交换反应

对癸二酸二甲酯与1,2,2,6,6-五甲基哌啶醇的酯交换反应进行了研究;分别考察了四异丙基钛酸酯、氨基锂、氧化二辛基锡3种催化剂的性能;采用氢核磁共振确定了产物的结构;考察了以四异丙基钛酸酯为催化剂时反应温度、反应时间、原料配比和催化剂用量对反应的影响。实验结果表明,四异丙基钛酸酯催化剂的催化效果最好;在癸二酸二甲酯与1,2,2,6,6-五甲基哌啶醇摩尔比1∶1.79、四异丙基钛酸酯催化剂的用量为反应物总质量的0.31%、反应温度180℃、反应时间6h的条件下,所得产物中单(1,2,2,6,6-五甲基-4-哌啶基)癸二酸甲酯(简称单酯)质量分数为23%和双(1,2,2,6,6-五甲基-4-哌啶基)癸二酸酯(简称双酯)质量分数为73%,单双酯质量比为1∶3.17,产物收率为93.3%。该方法可得到理想的单双酯比例及产物收率,具有很好的工业应用前景。     

X80焊管H_2S环境应力腐蚀开裂行为研究

采用三点弯曲加载法和微电极扫描测试技术,研究了X80高强度级管线钢及其焊缝区的抗H2S环境应力腐蚀开裂(SSCC)行为。测定了焊接接头的显微硬度分布,分析了显微组织结构、力学性能及抗腐蚀性能之间的相关性。研究表明,热影响区(HAZ)对应力腐蚀开裂最为敏感,母材的纵向和横向取样对应力腐蚀敏感性影响不显著,薄壁管材比厚壁管材有较好的抗H2S环境应力腐蚀性能。HAZ晶粒粗大、硬度高,局部腐蚀倾向大,由此导致该区SSCC敏感性高。     

PKI/CA技术综述

公开密钥基础设施(PKI)是解决网络安全的技术．典型PKI应用系统包括安全Web、注册机构(RA)、认证机构(CA)、目录(LDAP)和数据库等服务器．RA验证客户证书申请后提交CA．CA检查信息完整和数字签名正确后把证书存放到证书库和目录服务器，并将签发证书序列号通知客户和RA．客户即可使用该号通过目录服务器下载证书．1993年以来，美、加、欧洲、韩、日等国已相继展开PKI研究．我国2001年将PKI列入十五863计划，并着手解决PKI标准化、CA互联互通等关键技术问题。     

高校设备管理系统的设计与实现

运用Delphi 6和MS SQL Server 2000,在需求分析、功能模块划分、数据库模式分析的基础,设计了数据库结构并开发了高校的设备管理系统。该系统对设备管理中的需求计划、选型、购置、库存、使用、维修、更新及报废等全过程信息进行记录,同时兼顾资金计划和合同管理,使实物与财务有机结合,并为用户提供详尽准确的统计信息和便捷的管理手段。     

聚甲亚胺改性尼龙6复合材料的等温结晶动力学

采用差示扫描量热法（DSC）对聚甲亚胺（PAM）/尼龙6复合材料等温结晶过程进行了研究。结果表明，PAM的加入使得基体的结晶速率增大，尤其是当含量为5%时，半结晶期明显减少。研究还发现，该体系的等温结晶过程完全可以用Avrami方程来描述，各试样的Avrami指数均在2-3之间，表明Avrami指数，球晶生长方式基本不受聚甲亚胺加入的影响。基体中原位形成的聚甲胺微纤起到了诱导结晶的作用，使得基体的结晶速率加快，但随着微纤含量的增加，由于分散性能变差而使得诱导结晶的能力减弱，表现为结晶速率又有所降低。     

Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 2: Charakterisierung der Gefügeausbildung mittels hochauflösender Durchstrahlungselektronenmikroskopie und Feinbereichsbeugung

Chemical Composition and Microstructure of Polymer‐Derived Glasses and Ceramics in the Si–C–O System. Part 2: Characterization of microstructure formation by means of high‐resolution transmission electron microscopy and selected area diffraction Liquid or solid silicone resins represent the economically most interesting class of organic precursors for the pyrolytic production of glass and ceramics materials on silicon basis. As dense, dimensionally stable components can be cost‐effectively achieved by admixing reactive filler powders, chemical composition and microstructure development of the polymer‐derived residues must be exactly known during thermal decomposition. Thus, in the present work, glasses and ceramics produced by pyrolysis of the model precursor polymethylsiloxane at temperatures from 525 to 1550 °C are investigated. In part 1, by means of analytical electron microscopy, the bonding state of silicon was determined on a nanometre scale and the phase separation of the metastable Si–C–O matrix into SiO₂, C and SiC was proved. The in‐situ crystallization could be considerably accelerated by adding fine‐grained powder of inert fillers, such as Al₂O₃ or SiC, which permits effective process control. In part 2, the microstructure is characterized by high‐resolution transmission electron microscopy and selected area diffraction. Turbostratic carbon and cubic β‐SiC precipitate as crystallization products. Theses phases are embedded in an amorphous matrix. Inert fillers reduce the crystallization temperature by several hundred °C. In this case, the polymer‐derived Si–C–O material acts as a binding agent between the powder particles. Reaction layer formation does not occur. On the investigated pyrolysis conditions, no crystallization of SiO₂ was observed.