中细纤度家蚕品种数量性状主成分分析

采用多元统计分析方法,对15个家蚕品种的7个主要经济性状进行主成分分析。结果表明:7个数量性状可简化为产量因子、效率因子、纤度因子3个主成分,所提供的信息量占7个数量性状信息量的85.70%。在主成分分析的基础上,对15个品种的3个主成分值进行聚类分析后划分为4大类群:产量因子的整体趋势是第1类群>第2类群>第4类群>第3类群;效率因子是第3类群>第1类群>第4类群>第2类群;纤度因子是第3类群>第2类群>第1类群>第4类群。基于选择中细纤度蚕品种育种亲本的指标,推测第1类群(苏17、761、SC3、春萌、794)和第2类群(镇12、895春珠肥、854A、898、SJ3)是亲本选择、选配的优先选择材料。

Caustics study of the effect of glass fibres on dynamic fracture of hardened cement paste

The reflected optical caustics method is applied to study dynamic fracture problems in hardened cement paste. First both the unreinforced cement paste and the glass fibres reinforced cement paste specimens were fabricated and the reflective coating on the surface of the specimen was prepared. Secondly the crack path and the shadow spot patterns during the crack propagation process for the two specimens were recorded by using a multi-spark high speed camera.Thirdly some dynamic parameters of two cement paste specimens including crack onset time the dynamic stress intensity factor and crack growth velocity were determined and analyzed comparatively.This indicates that the glass fibres can improve the fracture resistance and delay fracture time.These results will play an important role in evaluating the dynamic fracture properties of cement paste.