Validating ionospheric models with measured electron density profiles

On behalf of an URSI Working Group 3 initiated study (VIM), three ionospheric models, IRI, PL/PRISM and FLIP, are compared with electron density profiles derived from ionograms Millstone Hill. Four months of data in 1989/90 were analyzed. For most of the time, N(h) profiles were available every 15 minutes providing a good statistical database for the evaluation of the ionospheric models in terms of diurnal and seasonal variations.     

二维 C/SiC复合材料的室温疲劳行为及寿命预测

为了研究二维C/SiC复合材料的疲劳行为并对其进行寿命预测,进行室温下二维C/SiC复合材料的拉伸试验和疲劳试验,并使用扫描电镜(SEM)观察其断口形貌。结果表明:C/SiC复合材料表现出类似金属的韧性断裂行为,疲劳极限约为极限拉伸强度(UTS)的85%,在室温下具有较为优良的抗疲劳性能;由于复合材料的缺口钝化效应,缺口试样的S-N曲线要高于光滑试样,但两者趋势一致,据此提出基于名义应力的疲劳寿命预测方法。     

航空航天用高强度Mg-RE系合金的研究进展

近年来，镁稀土合金由于其高强度、低密度和高温性能良好等特点，在追求轻量化的航空航天产业当中受到越来越多的关注。总结当前主流的2系高强度Mg-RE合金(Mg-Gd和Mg-Y系合金)的性能特点、强化机制和研究进展，简要介绍其他Mg-RE合金的研究情况，最后回顾镁稀土合金在航空航天领域的应用。