The Tunguska event in 1908: evidence from tree-ring anatomy

We analyzed tree rings in wood samples collected from some of the few surviving trees found close to the epicenter (within 4-5 km) of the Tunguska event that occurred on the last day of June 1908. Tree-ring growth shows a depression starting in the year after the event and continuing during a 4-5-year period. The most remarkable traces of the event were found in the rings' anatomical structure: (1) formation of "light" rings and a reduction of maximum density in 1908; (2) non-thickened tracheids (the cells that make up most of the wood volume) in the transition and latewood zones (the middle and last-formed parts of the ring, respectively); and (3) deformed tracheids, which are located on the 1908 annual ring outer boundary. In the majority of samples, normal earlywood and latewood tracheids were formed in all annual rings after 1908. The observed anomalies in wood anatomy suggest two main impacts of the Tunguska event on surviving trees--(1) defoliation and (2) direct mechanical stress on active xylem tissue. The mechanical stress needed to fell trees is less than the stress needed to cause the deformation of differentiating tracheids observed in trees close to the epicenter. In order to resolve this apparent contradiction, work is suggested on possible topographic modification of the overpressure experienced by these trees, as is an experimental test of the effects of such stresses on precisely analogous growing trees.     

螺纹联接结构密封材料应用研究

提出了一种适用于固体火箭发动机（SRM）的新型密封结构，并对应用于特定尺寸的螺纹联接结构方式、胶种选择进行了研究。通过压力、高低温循环等大量的试验和理论分析表明：采用填充密封胶的螺纹联接密封结构具有优异的密封性，适宜在固体火箭发动机环境中应用。     

固体火箭发动机密封材料(F108)回弹特性研究

设计了橡胶回弹特性的测试实验方法，对固体火箭发动机用氟橡胶圈密封材料（F108）回弹特性进行了研究。分析了固体火箭发动机实际使用条件下材料压缩状态、材料截面直径以及环境温度对橡胶圈回弹特性的影响，给出了部分回弹速度函数，为固体火箭发动机密封圈的设计提供了参考数据。     

大型水陆两栖飞机制造/装配方法分析

在对现代民用飞机制造装配方法特点进行分析的基础上,根据大型水陆两栖飞机自身外形、使用环境及机队数量,分析了两栖飞机与普通民用飞机的制造装配方法差异,主要体现在耐腐蚀性材料选择、机身船底制造装配和水密性要求三方面,大型水陆两栖飞机制造装配方法能满足增加维修间隔、便于维护及后续改装的要求。