民航英语词块教学与英语口语交际能力

本文分析了词块教学在提高民航英语学习者口语交际能力方面的重要作用。根据卡纳尔和斯温对交际能力的划分,交际能力分为语法能力、社会语言能力、语篇能力和策略能力四个方面,分别讨论了词块教学对民航英语学习者在这四种能力方面的促进作用。     

单晶硅电火花线切割表面损伤层形成机理

 为了研究单晶硅电火花线切割(WEDM)表面损伤层的损伤形式和形成机理,以电火花线切割加工后的单晶硅表面为研究对象,采用表面形貌观察分析及择优腐蚀方法研究了单晶硅经过电火花线切割后的加工表面.研究结果表明单晶硅经电火花放电加工后表面损伤形式分为4种:热损伤、应力损伤、热与应力综合作用损伤及电解/电化学腐蚀损伤.热损伤使得硅表面形成多晶或非晶硅;应力损伤使硅表面产生裂纹;热与应力综合作用会产生小孔效应,且随着放电功率密度的增加,小孔会明显增多;电解/电化学作用会加快损伤区域及杂质元素富集区域的腐蚀.     

复杂信息系统中单点登录的设计与实现

使用令牌机制,设计了一种适用于复杂信息系统门户平台的单点登录模型,实现了用户的统一身份认证和授权管理。用户一次登录门户就能自动访问所有授权的应用子系统或子模块,方便系统管理的同时有效提高了系统的安全性。最后以某保障信息系统为背景,描述了模型的技术实现。     

基于自适应遗传算法的航迹关联模型

如何解决关联过程巾产生的多维分配问题,是研究多节点航迹关联的关键。遗传算法能够很好地解决组合优化问题。但是基本遗传算法具有收敛速度慢和易于早熟等缺点,对于计算航迹关联问题来说实时性较差。文章在利用遗传算法解决航迹关联问题算法的基础上进行了改进,提出了自适应策略。仿真试验表明,该模型能够使航迹关联保持较高的正确关联率和较快的计算速度。     

Parameter Optimization Method for Gaussian Mixture Model with Data Evolution

To learn from evolutionary experimental data points effectively,an evolutionary Gaussian mixture model based on constraint consistency（EGMM）is proposed and the corresponding method of parameter optimization is presented.Here,the Gaussian mixture model（GMM）is adopted to describe the data points,and the differences between the posterior probabilities of pairwise points under the current parameters are introduced to measure the temporal smoothness.Then,parameter optimization of EGMM can be realized by evolutionary clustering.Compared with most of the existing data analysis methods by evolutionary clustering,both the whole features and individual differences of data points are considered in the clustering framework of EGMM.It decreases the algorithm sensitivity to noises and increases the robustness of evaluated parameters.Experimental result shows that the clustering sequence really reflects the shift of data distribution,and the proposed algorithm can provide better clustering quality and temporal smoothness.     

The influence of the spatial and temporal collocation windows on the comparisons of the ionospheric characteristic parameters derived from COSMIC radio occultation and digisondes

GPS radio occultation (RO) ionospheric products obtained by Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during the year of 2014 and the observations from 3 digisonde stations which are located at different latitudes are used to study the influence of different time and space collocation windows on the comparisons of the ionospheric characteristic parameters (ICPs), including the peak density and peak height, derived from the two techniques. The results show that the correlation coefficients (CC) and the standard deviation of the absolute biases (SDAB) between the ICPs derived from the two techniques vary distinctly under different spatial and time collocation windows. Generally, the CC (SDAB) of the ICPs decrease (increase) as the size of the collocation window increases in time dimension or in space dimension. The rate of change of the statistic parameters with the increase in the size of the collocation window in time dimension and space dimension is analyzed for each digisonde station. It is found that within the collocation window of $\left(60\mathrm{m}\mathrm{i}\mathrm{n},{20}^{°},{20}^{°}\right)$, the influence of the increase of $1^{°}$ in the space window on the statistical comparison is much more significant than that of the increase of 1?min in the time window, and it is suggested that there can be appropriate relaxation on the time window within the threshold of 60?min to get a balance between the quality of the comparison results and the number of the matched pairs. In addition, it is found that the same variations in the longitude window and in the latitude window may have different influences on the comparison results when the horizontal gradients in electron density are distinctly different along different directions at the digisonde station, and strict space collocation window is preferred when comparing the observations from COSMIC RO with those from the digisonde station in such cases.     

澳大利亚国立大学等离子体推进研究

介绍了澳大利亚国立大学在等离子体推进领域的发展历程、技术特色及其工作原理(螺旋波双层推进器—Helicon double layer thruster、双阶段4层栅格离子发动机—Dual stage 4 grid thruster、口袋火箭—Pocket rocket),主要装置及其特征参数(WOMBAT—Waves on magnetized beams and turbulence、WOMBAT XL、Chi Kung、Piglet)、诊断设备及其典型结果 (射频补偿朗缪尔探针、发射探针、B-dot磁探针、迟滞场能量分析仪、高灵敏度动量测量摆)以及研究成果、人才队伍、项目来源和国际合作等情况,并结合在等离子体推进领域的研究现状以及研究中遇到的科学技术问题,给出了针对性的建议和思考。     

基于误差随机过程无人飞行器的撞地概率计算公式

在误差随机过程为平稳正态过程的假设下，研究了无人飞行器撞地概率的计算问题。在已知地形数据的情况下，从理论上推导出无人飞行器只受到垂直干扰时的撞地概率的计算公式；并在仅利用地形特征参数的情况下，得到了较为简洁的计算公式，在进行无人飞行器航迹规划过程中可以实现撞地概率的实时计算。给出了无人飞行器既受到垂直干扰又受到水平干扰时的撞地概率的计算公式，并对它们的计算作了简化，得到了一个近似计算公式。讨论了撞地概率计算公式的应用问题，分析了误差随机过程的标准差、飞行器机动带宽及地形标准差对撞地概率的影响。     

某压气机试验件中1/2阶副谐波振动分析

本文首先概述了某压气机试验中观察到的1／2阶副谐波振动现象,然后根据旋转机械振动的研究结果,并结合该压气机试验件的具体结构,分析了该试验件可能产生1／2阶副谐波振动的主要原因,最后给出了排振措施。     

基于XML的MEMS材料数据库的设计与实现

MEMS材料数据库已经成为MEMS设计领域中必不可少的设计工具.本课题采用原生XML数据库,以XML文档构建底层数据库,用Tcl/TK作为数据库的前台开发工具.数据库保存了80多种材料的属性数据,实现了对数据的灵活操作,满足了MEMS的设计需要.