基于贝叶斯网络和共因失效的飞机电源系统可靠性分析

飞机电源系统中的冗余设计提升了飞机系统的可靠性，但同时也增加了共因失效发生的概率。为了准确分析飞机电源系统的可靠性，首先，采取α因子模型对共因失效部件的失效率进行分解计算，并利用贝叶斯网络（BN）建立考虑共因失效的飞机电源系统可靠性模型。然后，对比分析考虑与不考虑冗余部件之间的共因失效因素时飞机电源系统及其子系统的可靠性。结果表明，考虑冗余部件之间的共因失效因素时，得到的飞机电源系统及其子系统可靠度相对于不考虑冗余部件之间的共因失效因素时较低，更加吻合实际情况。     

The subauroral electron density trough: Comparison between satellite observations and IRI-2007 model estimates

We compare electron density predictions of the International Reference Ionosphere (IRI-2007) model with in situ measurements of the satellites CHAMP and GRACE for the years from 2005 to 2010 over the subauroral regions. The electron density between 58° and 68° Mlat are considered. The trough region Ne peaks during local summers and attain the valley during local winter. Around −100°E and 60°E, two larger electron density sectors features can be seen in both hemispheres during all three seasons, which attributed to the electron extending from middle latitude to trough region. From 2005 to the beginning of 2010, the model overestimates the trough region Ne by 20% on average and the decrease of Ne in this region can also be seen during the last solar minimum. In the southern hemisphere, the model prediction shows quite well consistence with the observation during all three seasons while the huge difference between observations and model estimation implies that the IRI-2007 model needs significant improvement to predict better the trough region in northern hemisphere.     

基于树形马氏链模型的可靠性分析方法

复杂系统的极限状态函数非线性程度较高，在进行可靠性分析时，易导致失效概率的计算误差大、效率低，针对上述问题，提出了树形马氏链（TMC）算法和基于该算法的可靠性分析方法。树形马氏链是对原始马尔可夫链的改进，其状态转移过程更加灵活，具备局部多链并行和自适应探索失效域边界的特性。树形马氏链通过多候选状态点扩大对失效域信息的收集，生成能充分反映失效分布特征的样本，对该样本进行自适应核密度估计得到近似最优的重要抽样分布密度函数，从而提高计算结果的准确度。文末的数值算例和工程算例验证了算法性能，计算结果表明算法对设计点、抽样起点的位置不敏感，处理强非线性及复杂串联系统问题时，能在少样本量下得到相对高准确度的计算结果，且在样本量改变时，计算结果相对稳定可靠；工程算例给出了所提方法在实际问题下的效率，体现了所提方法的工程应用价值。     

强激光对材料的热—力学破坏效应

概述了强激光对材料的热－力学破坏效应的最新进展，内容包括加热和熔融、热应力、汽化和烧蚀及层裂等方面。     

Sandwich module prototype progress for space solar power

Space solar power (SSP) has been broadly defined as the collection of solar energy in space and its wireless transmission for use on earth. This approach potentially gives the benefit of provision of baseload power while avoiding the losses due to the day/night cycle and tropospheric effects that are associated with terrestrial solar power. Proponents have contended that the implementation of such systems could offer energy security, environmental, and technological advantages to those who would undertake their development. Among recent implementations commonly proposed for SSP, the modular symmetrical concentrator (MSC) and other modular concepts have received considerable attention. Each employs an array of modules for performing conversion of concentrated sunlight into microwaves or laser beams for transmission to earth. While prototypes of such modules have been designed and developed previously by several groups, none have been subjected to the challenging conditions inherent to the space environment and the possible solar concentration levels in which an array of modules might be required to operate. The research described herein details our team's efforts in the development of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for microwave-based “sandwich” module prototypes. The implementation status and testing results of the prototypes are reviewed.     

Design concepts for the first 40 km a key step for the space elevator

The Marine Node for the Space Elevator Infrastructure is the base for all activities to load and unload the cargo and climbers. As the basic design of the space elevator power system is solar power only, the first 40 km is hazardous to operations and demands enclosed packaging of fragile tether climbers. A significant question is: how do we place a full-up tether climber, driven by solar power, above the atmosphere? Two approaches, starting at the Marine Node, allow the tether climber to initiate the climb with solar energy above the atmosphere. The third viable approach is to provide a platform at altitude for initiation of tether climb. These approaches would enable solar power to be the source of energy for climbing. The three approaches are:     

激光无线能量传输技术应用及其发展趋势

介绍了无线能量传输技术的分类,分析了无线能量传输技术在未来航天方面的应用需求,最后以激光无线能量传输系统为例,对系统组成、关键技术以及未来的发展趋势进行了展望。无线能量传输技术将为我国空间科学研究、天基遥感和环境监测等领域提供技术先进、应用灵活、可满足多类重大应用需求的支持。     

光学镜面磁流变抛光误差的频谱特征与分布特性研究

通过分析磁流变抛光误差的频谱特征,发现严重影响成像质量的敏感频率成分误差,采用二维连续小波变换算法确定出敏感频率误差的具体分布区域,分析其演变特征及其与工艺参数之间的关系,为修正加工提供指导,以实现精确控制不同频率成分、不同分布区域光学加工误差和改善成像质量的目的.     

Non-linear methods in remotely sensed multispectral data classification

The aim of this research is to develop an effective approach being able to deal with the stochastic nature of remote sensing data. In order to achieve this objective it is necessary to structure the methodological knowledge in the area of data mining and reveal the most suitable methods for the prediction and decision support based on large amounts of multispectral data. The idea is to establish a framework by decomposing the task into functionality objectives and to allow the end-user to experiment with a set of classification methods and select the best methods for specific applications. As a first step, we compare our results from Bayesian classification based on non-parametric probability density estimates of the data to the results obtained from other classification methods. Tree scenarios are considered, making use of a small benchmark dataset, a larger dataset from Corine land cover project for Bulgaria and analyzing different features and feature selection methods. We show that the theoretically optimal Bayesian classification can also achieve optimal classification in practice and provides a realistic interpretation of the world where land cover classes intergrade gradually.     

Application of Autoscala to ionograms recorded by the VIPIR ionosonde

In November 2008, the ionosonde station at Boulder, Colorado, USA (40.0°N; 105.3°W) became the host of a new ionosonde (VIPIR, Vertical Incidence Pulsed Ionospheric Radar) developed and built by Scion Associates.