低粘度环氧树脂的性能分析

采用气相色谱-质谱法分析了两种低粘度环氧树脂的成分。分析结果表明,两种环氧树脂及其固化剂的基本组成较为一致,说明两种树脂的主体配方相似,只是个别组分存在差异。有关力学性能测试的结果表明这两种树脂的性能相当：I号树脂的韧性好于II号树脂,ll号树脂的耐热性能略好于I号树脂,由树脂的粘度一时间曲线看出两者的升温速率相当,II号树脂的初始粘度略低。     

Integrity Based Access Control Model for Multilevel XML Document

XML's increasing popularity highlights the security demand for XML documents. A mandatory access control model for XML document is presented on the basis of investigation of the function dependency of XML documents and discussion of the integrity properties of multilevel XML document. Then, the algorithms for decomposition/recovery multilevel XML document into/from single level document are given, and the manipulation rules for typical operations of XQuery and XUpdate QUERY, INSERT,UPDATE, and REMOVE, are elaborated. The multilevel XML document access model can meet the requirement of sensitive information processing application.