室外木结构用胶粘剂胶合制品分层试验对比

以红松、落叶松、杉木和桦木为试验材料,使用苯酚-间苯二酚-甲醛树脂胶粘剂（RPF）和酚醛树脂胶粘剂（PF）,将试材顺纹胶合成抗分层试件,经过3个真空-加压-真空-加压-干燥循环,研究2种胶粘剂的抗分层能力。试验表明,RPF树脂与PF树脂的抗分层能力相近,桦木试件的抗分层能力低于其他木材试件。     

Detection of glue deficiency in laminated wood with pulse thermography

 Adhesion problems sometimes occur during the production of laminated wood products. To minimize such quality problems, there is a need for a nondestructive test that can provide continuous control of the process and the product. This study presents results from measurements performed to evaluate the potential of pulse thermography as a method to detect glue deficiency in laminated wood. Defect depth, defect size, and degree of glue deficiency have been varied. The surface layer was made of merbau (Intsia bijuga) and the substrate of Scots pine (Pinus silvestris). The results showed that pulse thermography is a promising tool for detecting glue deficiency underneath the thin laminated wood surface layers, mainly because of the short inspection time. Lack of glue with a minimum thermal defect size of 3 was detectable (thermal defect size is defined as the quotient of defect size and defect depth). The penetration depth was 1.0 mm and the highest contrast, 0.62°C, was achieved for one of the largest defects (24 mm) below the thinnest (0.5 mm) surface layer after 1 second. Starved glue joints showed about half the contrast compared to areas with total lack of glue. Received: April 24, 2002 / Accepted: July 26, 2002 Acknowledgments We gratefully acknowledge the support of this work from the Knowledge Foundation and The Swedish Wood Association.     

基于分层发散思想的四边形网格生成算法

针对铺路法的不足,提出了一种基于分层发散思想的有限元网格生成方法。详细介绍了这种分层发散网格生成过程中的初始条件确定、布点、布点加速方法等网格划分处理的关键内容,在分层发散法产生的节点基础上进行网格生成。通过大量的网格生成实例验证了本算法对2-D区域进行网格划分的可行性。     

纤维增强树脂复合材料/竹木胶合界面的处理工艺

以砂光处理、等离子体处理、羟甲基间苯二酚(HMR)处理为不同因素,研究了纤维增强树脂复合材料(FRP)/竹、FRP/木胶合界面处理工艺。结果表明胶合界面优化工艺为:FRP不做处理,而竹材和木材表面以150 g/m~2的涂布量涂布HMR。     

Role of N-cadherin in cranial neural crest delamination during chick embryogenesis

AIM: To investigate the role of N-cadherin in the delamination of neural crest cells. METHODS: The normal expression of N-cadherin in neural tube was identified using in situ hybridization. The cells with N-cadherin over expression were obtained by transfection of wild-type N-cadherin (wt-N-cadherin),and the cells with N-cadherin silencing expression were obtained by transfection of dominant-negative N-cadherin (dn-N-cadherin). The migration of cranial neural crest cells was determined by the technique of immunohistochemistry. RESULTS: Either overexpression or down-regulation of N-cadherin significantly affected the migration of cranial neural crest cells. CONCLUSION: Delamination and migration of the cranial neural crest cells rely on the relative N-cadherin expression in the neural tube during neurulation.     

汽车复合材料内燃机缸体的分层精化机理

基于物理力学弹性半解析方法,对复合材料内燃机缸体进行了分层精化、本构控制理论研究和典型算例数值计算。采用缸体的动态实时测试,获得了缸体所受真实载荷下主要点的应变响应,并通过系统仿真方法对计算结果进行了验证,得出了汽车复合材料内燃机缸体分层精化方法的一些结论。