飞机雷电防护设计与鉴定试验

飞机遭受雷击后产生强大的雷电流,它严重的威胁飞行的安全.本文分析了雷电造成的危害,并论述了飞机结构设计应为雷电流提供低阻抗的通路.对雷击放电敏感的部位和部件,必须根据自身的重要性采取适当的雷电防护措施,以尽可能减少雷电对飞机的损害.最后介绍了为确保雷电防护措施的可靠性而进行的验证试验方法.     

Lower ionosphere response to external forcing: A brief review

There are two ways of external forcing of the lower ionosphere, the region below an altitude of about 100 km: (1) From above, which is directly or indirectly of solar origin. (2) From below, which is directly or indirectly of atmospheric origin. The external forcing of solar origin consists of two general factors – solar ionizing radiation variability and space weather. The solar ionization variability consist mainly from the 11-year solar cycle, the 27-day solar rotation and solar flares, strong flares being very important phenomenon in the daytime lower ionosphere due to the enormous increase of the solar X-ray flux resulting in temporal terminating of MF and partly LF and HF radio wave propagation due to heavy absorption of radio waves. Monitoring of the sudden ionospheric disturbances (SIDs – effects of solar flares in the lower ionosphere) served in the past as an important tool of monitoring the solar activity and its impacts on the ionosphere. Space weather effects on the lower ionosphere consist of many different but often inter-related phenomena, which govern the lower ionosphere variability at high latitudes, particularly at night. The most important space weather phenomenon for the lower ionosphere is strong geomagnetic storms, which affect substantially both the high- and mid-latitude lower ionosphere. As for forcing from below, it is caused mainly by waves in the neutral atmosphere, i.e. planetary, tidal, gravity and infrasonic waves. The most important and most studied waves are planetary and gravity waves. Another channel of the troposphere coupling to the lower ionosphere is through lightning-related processes leading to sprites, blue jets etc. and their ionospheric counterparts. These phenomena occur on very short time scales. The external forcing of the lower ionosphere has observationally been studied using predominantly ground-based methods exploiting in various ways the radio wave propagation, and by sporadic rocket soundings. All the above phenomena are briefly mentioned and some of them are treated in more detail.     

Nighttime cloud properties retrieval using MODIS and artificial neural networks

In this work a methodology for inferring water cloud macro and microphysical properties from nighttime MODIS imagery is developed. This method is based on the inversion of a theoretical radiative transfer model that simulates the radiances detected in each of the sensor infrared bands. To accomplish this inversion, an operational technique based on Artificial Neural Networks (ANNs) is proposed, whose main characteristic is the ability to retrieve cloud properties much faster than conventional methods. Furthermore, a detailed study of input data is performed to avoid different sources of errors that appear in several MODIS infrared channels. Finally, results of applying the proposed method are compared with in-situ measurements carried out during the DYCOMS-II field experiment.     

基于领域专家知识的发动机模糊可靠性分配方法

提出了一种基于多领域专家知识的发动机模糊可靠性分配方法,以降低决策者主观偏好以及分配过程中模糊和不确定因素对分配结果的影响.基于对影响发动机可靠性因素的分析,建立了发动机模糊可靠性分配的数学模型,并以三角模糊数代替常规层次分析法中的标度,提出了一种模糊评判矩阵方法来确定影响可靠性因素的权重.在可靠性分配过程中,充分考虑多领域专家的意见和产品开发过程的风险性.以应用实例对提出方法的有效可行性进行了验证.      

基于投影寻踪的高光谱图像异常检测并行算法

投影寻踪方法能有效提取数据中的非高斯结构凸显异常信息,但在求解最优投影方向时存在计算量大、运行时间长的问题,为提高处理效率,提出一种机群环境下的并行算法.选用偏度和峰度组合作为投影指标,将所有像素光谱作为特定投影方向集依次搜索,求解最优投影方向.在并行计算各候选方向投影指标时,分割图像数据分布存储于各机群结点,数据子块朝候选方向并行投影后,将指标计算式变形分解,使各结点在指标计算过程中所需数据均为本地数据,解决数据局部性问题,并采用一种"轮流作主"的机制提高算法负载均衡程度.利用实用型模块化高光谱仪数据在机群系统上进行测试,达到了较好的加速效果,表明该并行算法具有良好的并行性能.     

易于硬件实现的遥感图像两倍压缩算法

结合干涉多光谱遥感图像航天应用的要求,参考CCSDS标准无损压缩算法,提出了一种易于硬件实现的干涉多光谱遥感图像无损／近无损压缩算法。该算法在对12bit干涉多光谱图像进行2倍压缩时压缩性能与JPEG 2000标准算法相当,但算法复杂度和所需存储空间大大降低,在单片FPGA内部即可实现全部压缩功能,可以很好地满足航天应用的要求。     

AEG评审在型号合格审定中的研究与应用

概述了申请人的航空器评审工作,并简要对比分析了运行符合性清单、型别等级和训练要求、MMEL、MRBR、OCAI等11个AEG工作评审项目。同时通过对比分析航空器评审组(简称AEG)评审与型号合格审定之间的区别和联系,为申请人顺利开展AEG工作提出4条建议。     

东北主体功能区绩效评价体系的构建

根据<国民经济和社会发展第十一个五年规划纲要>并结合东北实际,针对划分的优化开发、重点开发、限制开发和禁止开发四类主体功能区,按照全面性、科学性、针对性和可操作性的原则,初步设计了一套差别化的区域绩效评价体系的设计思路和评价指标.     

基于BP神经网络的国防企业技术创新能力评价

结合自组织理论提出了国防企业技术创新评价体系,构建了BP神经网络模型,运用MATLAB软件进行了模型仿真.研究发现仿真结果与专家评价结果基本一致.可见,运用BP神经网络方法对国防企业技术创新能力进行评价有一定的通用性、便捷性和实用性.     

Antenna for precise orbit determination

The ESA SWARM mission will consist of three satellites that will measure the Earth magnetic field. The system calls for metre accuracy knowledge of the measurement locations. To achieve this a GPS receiver is used. At least four GPS signals are tracked to determine the code and carrier ranges, from which the position can be derived. The accuracy improves when using more GPS satellites and by averaging over many measurements. The latter is achieved in ground processing with a model-based orbit prediction, resulting in cm accuracy. The main error contributions in the processing are often measurement errors due to satellite multi-path effects. The multipath effects are characterized by measuring the antenna on a 1.5 m mock-up, representing the 9 m long satellite. In order to verify that the mock-up is representative, extensive electromagnetic simulations were made. The simulations included the antenna and the complete satellite and were then reduced to the antenna and a section of the satellite. The actual design of the antenna was performed with several levels of software. First, a fast bodies-of-revolution simulation found a geometry with the right coverage. Then, a finite element method simulation allowed us to match the antenna at two frequencies simultaneously.