平均轨道要素及其在卫星星座设计中的应用

平均轨道要素在卫星轨道设计及星座仿真中具有非常重要的作用。在综合国内外现有研究成果的基础上，给出了一整套简单实用、没有奇点的密切要素与平均要素间的相互转化方法，用此法进行的星座设计及仿真工作表明该方法非常有用。同时给出了利用平均轨道要素得以的关于赤道平面圆轨道的一个有意义的结论。     

基于SPCE061A数字语音温度控制系统的设计

以凌阳SPCE061A单片机为控制核心,设计并制作了一款具有温度设定灵活、数字显示及语言播报功能的水温控制器,通过PID控制算法产生脉宽调制波,提高了控制精度。实践表明:该水温控制器达到了设计要求,有一定的实用开发价值。     

关于非结构网格生成中的背景函数

背景信息对于用阵面推进法生成非结构网格是一个关键的环节.文章基于众多文献中提到的背景信息提供方法,提出一种更为实用的背景信息提供技术.此方法不仅避免了不必要的机时,内存的消耗,又使网格具有光滑性,网格的生成具有灵活性,方便性的特点.基于生成的网格采用有限体积法研究无粘高超音速化学非平衡流的流场分布,生成的网格能够成功的运用于高超音速化学非平衡流的数值计算。     

钛合金胶接点焊接头的性能检测

研究了不同焊接电流下钛合金板胶接点焊接头的A扫描信号和C扫描图像特征,并进行了拉伸-剪切试验。结果表明:通过观察C扫描图像的特征与A扫描信号的变化,能够划分胶接点焊接头的胶层区、热影响区、熔合区、熔核区以及焊接缺陷;随着电流(7~10 k A)的逐渐增大,接头熔核直径呈递增趋势,相应的失效载荷从7 231.5增加到10 939.0 N;当电流为7 k A时,在C扫描图像上反映出飞溅缺陷,此时接头失效载荷远小于没有出现飞溅的接头,可见飞溅降低了胶接点焊接头的拉剪载荷。     

飞机电磁防护设计

飞机经常在恶劣的电磁环境中飞行,为使机内的设备不受损害,除了保证机载设备具有足够的抗干扰能力外,在飞机结构上,还应采取其他防护措施。本文在分析电磁危害性的基础上,介绍了飞机雷电防护、静电防护,以及抗电磁脉冲和射频干扰的设计方法。     

一种利用ILSP的同步DS-CDMA信号快速盲解扩算法

针对同步DS-CDMA信号的盲解扩问题，本文提出了一种基于迭代最小二乘投影算法(ILSP)的快速盲解扩算法。本算法首先通过对截获信号的协方差矩阵进行特征分解，估计出由各用户扩频序列张成的信号子空间，然后结合扩频码序列的有限符号集特性，利用ILSP算法消除由特征分解产生的酉矩阵模糊问题，得到扩频序列的精确估计，最后利用估计得到的扩频序列对截获信号解扩得到信息码序列，完成DS-CDMA信号的盲解扩。仿真结果表明本算法在低信噪比条件下具有良好的盲解扩性能，且相较传统算法本文提出算法大大降低了计算复杂度 。     

摆线桨非定常动态失速的三维效应

对摆线桨三维全尺寸模型进行了非定常数值模拟。验证了两种嵌套网格方法的可靠性与适用性,针对二维/三维情况下摆线桨非定常涡流动特性及诱导分离特性开展了数值分析,重点研究了展向气动力随方位角的分布与全局流场的诱导速度分布,并分析了尾迹捕捉精度与涡量耗散特征。结果表明:受摆线桨切向速度、展向诱导速度等三维效应影响,两种计算结果的瞬态气动力极值差值达到44%。三维动态失速涡的产生、脱落与再附明显弱于二维翼型情况,这对于摆线桨非定常气动特性有较大影响。      

Mg-Sc-Y三元合金的微观组织和力学性能

稀土元素作为重要的镁合金强化相元素,其多元添加产生的影响并未得到充分研究。在Mg-Sc二元系的基础上将Y作为第三元加入,制备了Mg-5Sc二元合金及Mg-5Sc-0.5Y,Mg-5Sc-1Y,Mg-5Sc-2Y,Mg-5Sc-3Y,Mg-5Sc-3.5Y(质量分数,%)5种三元合金,并通过光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射(XRD)及室温拉伸等试验,研究了Y元素的加入对Mg-Sc二元合金微观组织和力学性能的影响。结果表明:Y元素在合金中的主要存在形式为固溶态,富集于晶界处。随着Y元素含量的提升,合金晶粒度显著减小,屈服强度和硬度大幅提升,Mg-5Sc-3.5Y的屈服强度相比Mg-5Sc提升了约50%。该强度的提升主要是由细晶强化和固溶强化引起的。     

Crystal orientation and morphology of a lamellae in wrought titanium alloys: On the role of microstructure evolution in b processing

To obtain high-quality aviation forgings of titanium alloys, b forging is an essential processing step which must be considered throughout a production process. In this work, the effect of b forging on the crystal orientation and morphology of lamellar a was experimentally investigated in a two-phase titanium alloy. Strong dynamic recovery during b working resulted in the formation of low-angle grain boundary(LAGBb) inside b grains. The lamellar a can penetrate through the LAGBb, leading to similar intra a LAGBs on subgrain boundaries. Deformation banding occurs at high strain rates, and both diffusive and sharp boundaries of deformation bands can be observed.A continuous change of the b orientation in diffusive boundaries results in the formation of fine and disordered a lamellae without intra-lamellar boundary to hold the Burgers orientation relationship(OR). On sharp boundaries, it is prone to producing continuous grain boundary a(aGB) with a highly similar orientation along the boundaries. Meanwhile, there may exist several lower-angle boundaries within the grain boundary a for a smoother orientation change on the b grain boundary.     

A comprehensive study of the 2016 Mw 6.0 Italy earthquake based on high-rate (10 Hz) GPS data

The 2016 M_w 6.0 Italy earthquake is successfully recorded by the near-field 10?Hz GPS and 200?Hz Strong Motion (SM) stations, providing valuable data for this study. A comprehensive study of this earthquake is carried out based on GPS data, which contains coseismic deformations analysis, noise analysis, seismic wave picking, and magnitude determination. The noise of most GPS-derived displacement waveforms can be described as a combination of white noise, flicker noise, and random walk noise after the earthquake occurrence, and the spectral indices vary significantly for most stations, implying that the seismic signals have affected the noise characteristic of GPS-derived displacement waveforms. S-transform is employed to assess the GPS capability to detect the seismic arrival time. The SM station AMT and the GPS station AMAT are in good agreement in seismic wave picking, and the difference is only 1.2?s in the north component, suggesting that the outcome of seismic wave picking using GPS data is reliable. Then, a classic empirical formula is employed to determine the moment magnitude. A robust moment magnitude (Mw 5.90) can be estimated by the nine GPS stations with about 23.9?s. If four GPS stations near the epicenter is chosen to determine the magnitude, it only take 13.0?s to retrieve a reliable preliminary (Mw 5.82) magnitude, which is 5.4?s ahead of nine stations. In addition, Cross Wavelet Transform (XWT) is adopted to measuring the correlation and phase relationship between GPS and SM records. The result of XWT analysis indicates 10?Hz GPS is capable of capturing reliable and accurate coseismic dynamic deformations, as evidenced by the XWT-based semblance being close to 1 between GPS and SM records. The above results confirm the capability of 10?Hz GPS to capture coseismic dynamic deformations, detect seismic arrival time, and determine earthquake magnitude. Moreover, rapid magnitude determination based on 10?Hz GPS data can be regarded as an important supplement to Earthquake Early Warning (EEW).