柱形等离子体电离阻抗测量与分析

表面波等离子体的研究由于实验数据的大量积累而得到快速发展.结合传输线阻抗匹配原理,设计实验对柱形表面波等离子体电离阻抗进行测量;参照金属辐射体中辐射阻抗与损耗阻抗的求解方法,在简化条件下理论计算柱形等离子体的电离阻抗,并与实验数据进行分析比对.研究表明,表面波激发柱形等离子体的电离阻抗对等离子体源产生效率的分析及等离子体参数的诊断有着重要作用.这种新型等离子体源的研究具有非常重要的意义.     

Minimum quantity lubrication machining of aeronautical materials using carbon group nanolubricant: From mechanisms to application

It is an inevitable trend of sustainable manufacturing to replace flood and dry machining with minimum quantity lubrication(MQL) technology. Nevertheless, for aeronautical difficult-tomachine materials, MQL couldn’t meet the high demand of cooling and lubrication due to high heat generation during machining. Nano-biolubricants, especially non-toxic carbon group nano-enhancers(CGNs) are used, can solve this technical bottleneck. However, the machining mechanisms under lubrication of CGNs are uncl...     

Soft landing stability analysis of a Mars lander under uncertain terrain

Safe soft landing of the lander is vital to the Mars surface exploration mission. Analysis and verification of the landing stability under uncertain terrain play an important role in lander design. However, the effect of uncertain terrain is ignored in most existing studies, making the analysis incomprehensive and increasing the risk of landing failure in practice. In this paper, a Mars lander with 10 attitude control thrusters is introduced and its dynamics model is then established considering...     

Flow field design and experimental investigation of electrochemical machining on blisk

Flow field is a crucial factor to influence the stability and surface quality in the electrochemical machining (ECM) of blisks. A four-way flow mode was proposed to eliminate mixing regions of electrolyte at the leading and tailing edges. Two flow field models were described separately in this report: a W-shaped flow mode and a four-way flow mode. The flow field was analyzed through a finite element method. The results showed that, in comparison with the W-shaped flow mode, the distribution of electrolyte flow was more uniformed and the mixed region in the flow channel was improved. The pressure of the leading and tailing edges inlets was optimized, and optimal pressure of 0.6 MPa was determined. In addition, verification experiments were performed, and the results showed that the stability, efficiency, and quality of the profiles of the blisk blade manufactured by ECM were enhanced in the new flow mode.     

航天飞行器防热涂层烧蚀行为及机理研究

为拓宽航天飞行器防热涂层裂解温域,提高涂层的耐烧蚀性能,文章通过热重–差示扫描量热分析仪（TG-DTG）分析了2种硅橡胶基体的热分解行为,并结合马弗炉烧蚀实验研究铁红、云母、白炭黑等3种功能组元对硅橡胶涂层静态烧蚀性能的影响,通过扫描电镜（SEM）以及红外光谱分析仪（FT-IR）分析烧蚀机理,最后通过马弗炉烧蚀实验及高温燃气流烧蚀实验对2种涂层的烧蚀性能进行考核。结果表明：甲基苯基硅橡胶在220～320 ℃温域的裂解主要以侧基交联为主;在320～480 ℃以由羟基引发的主链“回咬”机制为主;在480～630 ℃则通过链间折叠发生环降解反应。主链“回咬”和链间环降解反应均会导致树脂基体交联密度降低,力学性能下降,产生“粉化”。甲基乙烯基硅橡胶在其裂解温域370～780 ℃主要发生侧基交联反应,树脂基体交联密度上升,热稳定性提高。白炭黑对于2种硅橡胶基体的热稳定性提升最为显著;铁红、云母等均会在高温下与硅橡胶基体产生共融,减缓硅橡胶基体的高温裂解。     

表面等离子体共振生物传感器在微生物检测中的应用

在地球环境及航天空间环境中存在有多种多样的微生物,快速、准确地检测这些微生物成为亟待解决的问题.在众多微生物检测方法中,表面等离子体共振生物传感器凭借其快速、灵敏的检测特点,近年来发展迅速.本文综述了表面等离子体共振生物传感器在微生物检测领域中的应用,以期为地面及航天环境的微生物检测工作提供技术参考.     

Interference and grinding characteristics in ultra-precision grinding of thin-walled complex structural component using a ball-end grinding wheel

As for ultra-precision grinding of difficult-to-process thin-walled complex components with ball-end grinding wheels, interference is easy to occur. According to screw theory and grinding kinematics, a mathematical model is established to investigate the interference and grinding characteristics of the ball-end wheel. The relationship between grinding wheel inclination angle, C axis rotation angle, grinding position angle and grinding wheel wear are analyzed. As the grinding wheel inclination angle increases, the C axis rotatable range decreases and the grinding position angle increases. The grinding position angle and wheel radius wear show a negative correlation with the C axis rotation angle. Therefore, a trajectory planning criteria for increasing grinding speed as much as possible under the premise of avoiding interference is proposed to design the grinding trajectory. Then grinding point distribution on the ball-end wheel is calculated, and the grinding characteristics, grinding speed and maximum undeformed chip thickness, are investigated. Finally, a complex structural component can be ground without interference, and surface roughness and profile accuracy are improved to 40.2 nm and 0.399 μm, compared with 556 nm and 3.427 μm before ultra-precision grinding. The mathematical model can provide theoretical guidance for the analysis of interference and grinding characteristics in complex components grinding to improve its grinding quality.     

Development cost prediction of general aviation aircraft projects with parametric modeling

The study of the development cost of general aviation aircraft is limited by small samples with many cost-driven factors. This paper investigates a parametric modeling method for prediction of the development cost of general aviation aircraft. The proposed technique depends on some principal components, acquired by utilizing P value analysis and gray correlation analysis. According to these principal components, the corresponding linear regression and BP neural network models are established respectively. The feasibility and accuracy of the P value analysis are verified by comparing results of model fitting and prediction. A sensitivity analysis related to model precision and suitability is discussed in detail. Results obtained in this study show that the proposed method not only has a certain degree of versatility, but also provides a preliminary prediction of the development cost of general aviation aircraft.     

烧蚀热响应计算中的不确定性传播分析方法研究

发展了基于代理模型的不确定度量化方法，以少量确定性模拟结果为样本，通过代理模型来构建目标变量和不确定性输入参数的响应关系，以此来分析目标变量的不确定性信息，包括均值、标准差、概率密度分布等统计信息以及各个输入参数对目标变量的敏感性大小。本文以烧蚀热响应计算为例，通过分析材料物性参数的不确定性对烧蚀热响应预测的影响，表明该方法具有准确度高、效率高的特点，为工程中的高维不确定度量化问题提供了很好的解决思路。     

Integrated supersonic wind tunnel nozzle

In supersonic wind tunnels, the airflow at the exit of a convergent-divergent nozzle is affected by the connection between the nozzle and test section, because the connection is a source of disturbance for supersonic flow and the source of disturbance generated by this disturbance propagates downstream. In order to avoid the disturbance, the test can only be carried out in the rhombus area. However, for the supersonic nozzle, the rhombus region is small, limiting the size and attitude angle of the test model. An integrated supersonic nozzle is a nozzle and a test section as a whole, which is designed to weaken or eliminate the disturbance. The inviscid contour of the supersonic nozzle is based on the method of characteristics. A new curve is formed by the smooth connection between the inviscid contour and test section, and the boundary layer is corrected for the overall curve. Integrated supersonic nozzles with Mach number 1.5 and 2 are designed, which are based on this method. The flow field is validated by numerical and experimental results. The results of the study highlight the importance of the connection about the nozzle outlet and test section. They clearly show that the wave system does not exist at the exit of the supersonic nozzle, and the flow field is uniform throughout the test section.