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一、引言
国际航空界公认风切变是飞机起飞和着陆阶段的一个重要危险因素。与风切变有关的飞行事故都发生在300m以下的起飞和着陆阶段,尤以着陆阶段为甚,占78%。航空气象学根据风场的结构,把风切变分为水平风的垂直切变、水平风的水平切变和垂直气流切变等三种类型。根据飞机相对于风矢量间的不同情况,又可把风切变分为顺风切变、逆风切变、侧风切变和垂直气流切变等四种形式。 相似文献
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1999年9月10日阳出现的强对流天气是1989-1999十年间持续时间最长的强对流天气,强度之大实属罕见。本从天气形势和物理场的变化对1999年9月10日洛阳机场的强对流天气过程进行分析,得出一些有意义的结论。 相似文献
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根据统计学原理,利用哈尔滨太平国际机场1996年至1995年的气象观测资料,对该机场低能见度的基本气候特征及其变化规律作出详细的统计分析。 相似文献
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ZHANG Yu-xiang WANG Jin-cheng YANG Yu-juan YANG Gen-cang ZHOU Yao-he 《中国航空学报》2007,20(2):107-110
A phase-field method was employed to study the influence of elastic field on the nucleation and microstructure evolution. Two kinds of nucleation process were considered:one using fixed nucleation probability and the other calculated from the classical nucleation theory. In the latter case, the simulated results show that the anisotropic elastic strain field yields significant effects on the behavior of nucleation. With a large lattice misfit between the matrixes and the precipitates, the nucleation process does not appear fully random but displays some spatial correlation and has a preference for the elastic soft direction. However, with a small lattice misfit, this bias does not look quite clear. On the contrary, in the case of fixed nucleation probability, the elastic field has no influence on the nucleation proc- ess. The lattice mismatch also exerts influences on the microstructure morphology: with lattice mismatch becoming larger, the micro- structure proves to align along the elastic soft direction. 相似文献