前体非对称涡高风速烟雾显示技术

通过在细长旋成体模型机身的不同位置设置出烟孔,使用新型发烟装置对模型注入雾化油 滴,采用激光片光法在常规风洞中高风速(60m/s)条件下得到清晰、完整而稳定的截面涡 结构图像. 并通过同状态标定法和等比例网格法发展了简易涡位定量测量技术,为前体非对 称涡Re数效应的研究提供了重要的技术平台.     

Effects of tip perturbation and wing locations on rolling oscillation induced by forebody vortices

The wing rock motion is frequently suffered by a wing-body configuration with low swept wing at high angle of attack. It is found from our experimental study that the tip perturbation and wing longitudinal locations affect significantly the wing rock motion of a wing-body. The natural tip perturbation would make the wing rock motion of a nondeterministic nature and an artificial mini-tip perturbation would make the wing rock motion deterministic. The artificial tip perturbation would, as its circumferential location is varied, generate three different types of motion patterns： （1） limit cycle oscillation, （2） irregular oscillation, （3） equilibrium state with tiny oscillation. The amplitude of rolling oscillation corresponding to the limit cycle oscillatory motion pattern is decreased with the wing location shifting downstream along the body axis.     

Graphene/Mo_2C heterostructure directly grown by chemical vapor deposition

Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo_2C heterostructure by using chemical vapor deposition(CVD). The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo_2C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.     

Asymmetric vortices flow over slender body and its active control at high angle of attack

The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed, which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks. The project supported by the National Natural Science Foundation of China (10172017), Aeronautical Science Foundation of China (02A51048) and Foundation of National Key Laboratory of Aerodynamic Design and Research (51462020504HK0101)     

磷在硅表面氧化层中的扩散

用示踪原子方法,研究了磷(Na₂HP³²O₄)在p型硅表面氧化层中的扩散。硅单晶的电阻率为5—6欧姆·厘米。氧化层是在高温下水汽中生长的,其厚度为0.5—0.6微米,是用灵敏度为10^-5克/刻度的微量天平测定的。发现在1245℃时氧化层的生长规律服从X^1.85=1.4×10^-2t,其中X为氧化层的厚度,单位为微米;t为氧化层的生长时间,单位为分钟。其红外吸收的测量结果与文献中的数据基本一致。扩散是在充满空气的封闭石英管中进行的,扩散温度为700—1250℃,扩散时间从4分钟到5小时。实验结果表明,磷在SiO₂层中的浓度分布不能直接用菲克第二定律描述,它可以看成是一个均匀分布和一个遵守菲克第二定律的分布的迭加。按后一种分布得到在700—1200℃范围内的扩散系数的温度依赖关系:D=1.9×10^-9exp(-1.1/kT)厘米²/秒。均匀分布部分的浓度为(1—8)×10¹⁹原子/厘米³。大中对所用方法和所得结果作了简单讨论.     

A critical pattern of crossflow around a slender

IntroductionModernhigh_performancefightersoftenrequiretobeoperatedunderafairlylargeangleofattacksoastoachieveexcellentmaneuverabilityandagility .Atsuchlargeangleofattack ,asymmetricallee_sidevortexflowwillformatthefrontpartofthefuselage .Sothatsuchagreats…     

Stability of the crossflow pattern around a slender and influence of disturbance

Topological structure and stability of a slender cross flow is discussed by the stability theory of dynamic system. The inner boundary of flow field was limiting streamline and it was proved that the topological structure connected saddles by limiting streamline is stable. It is proved that the development of slender vortices leads to the change of topological structure about cross flow. And it is the change from stable and symmetrical vortices flow pattern to unstable and symmetrical vortices flow pattern, and then to stable and asymmetrical vortices flow pattern due to little disturbance which leads to the development of asymmetrical slender vortices. The influence of disturbance to flowfield structure was discussed by unfolding theory too.     

大迎角细长体绕流背涡结构与气动特性分析

结合实验成果，对大迎角细长体绕流结构及其气动特征进行了分析。利用势流理论，探讨了大迎角下非对称侧向力沿物体轴线的变化特征与分离背涡结构之间的关系，得出截面侧向力系数沿轴向呈现正弦型曲线的变化特征是由轴向旋涡不断脱落所形成的多涡系统诱导的结果。对于三涡以上的多涡系统中，对称的物面压强分布并非一定对应对称的涡结构。     

磷在SiO2-Si系统中的扩散

用中子激活方法,对气态P₂O₅在SiO₂-Si系统中的扩散分布进行了直接测量。样品为p型Si单晶,电阻率为3—5欧姆·厘米,氧化层是在1250℃下水汽中生长的,其厚度为0.45—0.47微米。实验结果表明:对于完全掩蔽的样品,磷在SiO₂层中的浓度分布有个陡峭的边界;对于掩蔽失效情形,在靠近SiO₂-Si交界面约0.1微米的SiO₂层内,磷的浓度显著地降低,出现一个明显的交界层,在交界层以外的SiO₂层中磷的浓度是均匀的和恒定的,而交界层中磷的浓度及磷在Si中的表面浓度都随时间的延长而显著地升高,文中对所得的结果作了简单讨论。