基于3D-PLM协同的航空复杂产品生命周期质量管理技术研究

目前我国航空复杂产品制造企业在PLM技术应用方面取得了一定的成果,在主机厂、所之间已经实现了基本的协同研制和生产,虽然这种协同模式未能包含诸如发动机和机载设备的供应商,但已在航空工业内部探索了价值链前端的部分协同,同时也开展了PLM多项目并行协同的数字化平台建设,这些都为基于3D-PLM协同的产品生命周期质量管理奠定了良好的基础。     

一种直升机总体概念设计方法

使用分析以及统计的方法,针对单旋翼带尾桨构型直升机提出了一种直升机总体概念设计的方法.首先根据直升机的主要设计要求,确定直升机总质量、发动机需用功率、旋翼半径、桨叶实度、废阻面积以及桨尖速度等总体参数.然后通过对直升机气动布局参数的统计与归纳,初步确定直升机的气动布局参数,利用这些参数对直升机总质量重新估算,经反复迭代后得到一组可以进行飞行性能以及操稳性计算的概念设计参数.     

Nb-Si 基超高温合金的研究进展

Nb-Si基超高温合金由于熔点高、密度低和优良的高温强度等特点受到广泛关注,极具作为下一代高推重比航空发动机和超然冲压发动机的热端部件用材料的潜力.本文主要介绍了国内外在合金化、粉末冶金、定向凝固和热处理工艺对Nb-Si基合金组织和性能影响等方面的研究现状,并展望了其发展趋势.     

发动机进气道短舱前缘结冰三维模拟研究

为计算发动机进气道短舱前缘的结冰冰形,在Messinger结冰热力学模型的基础上发展了一套纯三维的表面溢流水流动结冰模型。考虑空气摩擦力为表面溢流水流动的主要驱动力,用空气对进气道表面的剪切力来确定溢流水的流动方向及流量分配。为求解溢流水结冰模型,发展了一套重复查找表面控制体状态的方法,能够快速完成整个三维表面的计算。用该方法对某三维发动机进气道进行计算,得到了三维结冰冰形,并将计算结果与FENSAP-ICE计算结果进行了对比,结果显示两者的冰形轮廓基本一致,仅在冰角处存在差异,表明本文三维发动机结冰计算模型与计算方法是有效的,其计算精度与FENSAP-ICE结果相当。     

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity through the rim seal interacts with the main flow, producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation, development and evolution of downstream secondary flow. In this paper, a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss. Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation. Then, a deep insight into the loss mechanism of interaction between purge flow and main flow is gained. The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity, but also alters the cascade exit flow angle distribution along the spanwise. Moreover, aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced. Therefore, the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design. What is more, it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.     

高校体育行政管理信息系统的开发

介绍笔者开发的《高校体育行政管理信息系统》的基本特点、系统结构和主要功能，以及系统运行效果和应用前景。     

基于89C51的低速无线串行通信

在一些相对较复杂的单片机应用系统中,仅仅一个单片机资源是不够的,往往需要两个或多个单片机系统协同工作,论文介绍一种实现双机无线串行通信的方法。     

Active collision avoidance maneuver under constant thrust

In this paper, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target maneuver positions are calculated through the isochronous interpolation method. Furthermore, new switch control laws under constant thrust are designed for active collision avoidance maneuver of the chaser along a specified trajectory. The switch control laws are obtained based on the acceleration sequences and the working times of thrusters in three axes which can be respectively computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the working times.     

Assessment of the sensitivity of vegetation to El-Niño/Southern Oscillation events over China

This research explores the sensitivity of vegetation in China to El-Niño/Southern Oscillation (ENSO) events from 1982 to 2006. The ENSO events are defined by the Multivariate ENSO Index (MEI), and variation in vegetation cover is captured by the Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI). Pearson’s χ2 test was used to identify the areas where the variation in vegetation was sensitive to El Niño and La Niña events. The difference in the sensitivity of various ecosystems was investigated using the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover product in 2000. Composite NDVI graphs during El Niño, La Niña and non-ENSO years were also produced to investigate the ENSO relationship with the six vegetation ecosystems during El Niño, La Niña and normal phases. The results show that most of the ENSO-sensitive land in China is only affected by one of the two phases of ENSO events, and the area of El Niño-sensitive vegetation is much larger than that of La Niña-sensitive vegetation. North China and the Hengduan Mountains are the two cores of the El Niño-sensitive areas, while the La Niña-sensitive areas are mainly distributed in the central, northwest and northeast regions of China. The sensitivity of vegetation varies across ecosystems: grassland and shrubland had the largest share of El Niño-sensitive areas, and sparse vegetation and savanna were the most sensitive to La Niña events. Overall, the impacts of El Niño events on vegetation in China had regular seasonal variation, while the impacts of La Niña events had regular zonal distribution.     

基于聚偏二氟乙烯(PVDF)压电薄膜的密封舱壁穿孔损伤识别技术

日益恶化的空间碎片环境将严重威胁空间站及航天员的在轨安全。文章基于聚偏二氟乙烯（polyvinylidene fluoride,PVDF）压电薄膜设计了一种密封舱壁穿孔损伤识别技术方案,用于识别空间碎片超高速撞击对航天器密封舱壁造成的损伤模式,可为航天员合理选择应急措施提供依据。首先,发射超高速弹丸穿透铝合金靶板以模拟密封舱壁被击穿损伤的情况,形成的碎片云撞击PVDF压电薄膜探头,利用信号采集设备获取高速撞击引起的去极化效应信号,识别该信号的频率特征;其次,对PVDF压电薄膜探头及其支撑结构进行敲击试验,模拟在轨运行时因碰撞产生的干扰信号,掌握此类干扰信号的频率特征。试验结果表明,当系统采样频率为20 MHz时：1）所获得的探头去极化效应信号具有极为陡峭的上升沿,且上升沿的时长为亚μs量级;2）去极化效应信号主要由1 MHz以下的信号组成,但也包含少量的3～10 MHz高频成分;3）敲击探头及其支撑结构所产生的干扰信号频率在20 kHz以下。可根据频率差异进行两种信号的识别。