浅析热电偶引线断裂对EGT测量系统的影响

本文对CFM56-5B发动机EGT测量系统构成原理和电路进行了分析,结合测量系统构成原理和电路分析,揭示热电偶引线断裂的非典型性故障未触发驾驶舱内警告的原因。     

Light weight optimization of stratospheric airship envelope based on reliability analysis

A stratospheric airship is an essential flight vehicle in the aviation field. In this paper, optimal design approach of stratospheric airships is developed to optimize envelope shape considering three failure modes and multidisciplinary analysis models, and could also reduce the mass of a stratospheric airship to be deployed at a specific location. Based on a theoretical analysis, three failure modes of airships including bending wrinkling failure, hoop tearing failure and bending kink failure, are given to describe and illustrate the failure mechanism of stratospheric airships. The results show that the location, length and size of the local uniform load and the large fineness ratio are easier to lead to bending wrinkling failure and bending kink failure. The small fineness ratio and the increasing differential pressure are more prone to cause hoop tearing failure for an airship hull. The failure probability is sensitive to the wind field. From an optimization design, the reliability analysis is essential to be carried out based on the safety of the airship. The solution in this study can provide economical design recommendations.     

The low and middle latitude semi-annual anomaly in NmF2 near noon: A statistical study

Hourly values of the F2-layer peak density, NmF2, measured by 99 ionosonde stations near noon from 1957 to 2010 at low and middle geomagnetic latitudes of the northern and southern geographic hemispheres are used in a statistical study of the F2-region semi-annual anomaly. The equinox/winter and equinox/summer geomagnetically quiet NmF2 ratios, X and Y, taken near noon over each ionosonde for approximately the same winter, equinox, and summer solar activity conditions are analyzed. The conditional probabilities of occurrences of X and Y in intervals of X and Y, the most frequent values of X and Y, the mean expected values of X and Y, and the conditional probability to observe the F2-region semi-annual anomaly are calculated and studied for the fist time for low, moderate, and high solar activity conditions. These statistical parameters are averaged over 5° geomagnetic latitude interval in the northern and southern geographic hemispheres, and the trends in these averaged statistical characteristics of the NmF2 semi-annual anomaly are calculated and studied for the fist time. It is shown that the median approach can produce the incorrect conclusions about the absence of the NmF2 semi-annual anomaly.     

Equatorial vertical E × B drift velocities inferred from ionosonde measurements over Ouagadougou and the IRI-2007 vertical ion drift model

F-region vertical plasma drift velocities were deduced from the hourly hmF2 values acquired from ionogram data over a near dip equatorial station Ouagadougou (12.4°N, 358.5°E, dip angle 5.9°N) in Africa. Our results are compared against the global empirical model of Scherliess and Fejer (1999) incorporated in the IRI model (IRI-2007) for 1600 to 0800 LT from 1 year of data during sunspot maximum year of 1989 (yearly average solar flux intensity, F10.7 = 192) corresponding to the peak phase of solar cycle 22, under magnetically quiet conditions. The drifts are entirely downward between 2000 and 0500 LT bin for both techniques and the root mean square error (RMSE) between the modeled and the ionosonde vertical plasma drifts during these periods is 3.80, 4.37, and 4.74 m/s for June solstice, December solstice and equinox, respectively. Ouagadougou average vertical drifts show evening prereversal enhancement (PRE) velocity peaks (V_ZP) of about 16, 14, and 17 m/s in June solstice, December solstice, and equinox, respectively, at 1900–2000 LT; whereas global empirical model average drifts indicate V_ZP of approximately 33 m/s (June solstice), 29 m/s (December solstice), and 50 m/s (equinox) at 1800 LT. We find very weak and positive correlation (+0.10376) between modeled V_ZP versus F10.7, while ionosonde V_ZP against F10.7 gives worst and opposite correlation (−0.05799). The results also show that modeled V_ZP–Ap indicates good and positive correlation (+0.64289), but ionosonde V_ZP–Ap exhibits poor and negative correlation (−0.22477).     

面向产品综合设计的故障知识本体研究

以满足产品的性能与可靠性维修性保障性(RMS)综合设计需求为目标,对产 品设计过程中如何预防故障,定位故障及故障维修的相关概念进行分析、总结和归纳,提出 了以故障知识为核心,面向产品综合设计的知识本体框架,该框架将相关概念划分为四层进 行描述,即产品层、故障基本概念层、故障扩展层、故障应对层。利用本体论方法对相关的 核心概念进行了形式化的定义,并给出了基本的故障知识本体和设计应对本体结构。最后以 挑战者号航天飞机的失事为例,应用本文建立的故障本体较好地表达了航天飞机故障过程及 应对的改进措施,验证了该方法的可行性。
     

基于热喷涂技术制备的热障涂层

着眼于热喷涂技术在热障涂层制备方面的研究现状,在分析热障涂层失效原因的基础上,介绍了等离子喷涂技术及冷喷涂技术和在热障涂层结合层和陶瓷层制备方面的研究进展。     

基于小波变换的脉冲耦合神经网络预测模型及其应用

被称为第三代人工神经网络的脉冲耦合神经网络(PCNN)模型,以其耦合机制、脉冲输出两大基本特性广泛应用于图像处理等领域。文章在两大基本特性的基础上对PCNN进行了改进:增加了绝对误差控制公式;连接强度以相关系数来控制,调整阈值设置为最小误差;网络的运行机制与以往的PCNN原理有所不同;将ATrous小波变换与PCNN模型相结合,形成了组合预测模型。将改进后的组合模型用于年降雨量的预测中,以求检验模型的可行性。预测结果表明,基于小波变换的PCNN组合模型用在年降雨量预测中是可行的,并取得良好效果。为进一步深化PCNN的理论、拓宽PCNN的应用领域、解决水文水资源中的预测问题提供了新的思路和方法。     

层合复合材料高速冲击仿真研究进展

简述高强度纤维增强层合复合材料在高速冲击下的主要损伤模式和计算后的能量评估内容,介绍有限元仿真过程中不同材料模型、失效模型和刚度软化的特点,评述整体和分层两种建模方法的优缺点,提出发展趋势。     

改进灰色预测模型在对地攻击弹药需求预测中的应用

针对战时航空兵编队对地攻击的弹药需求问题,研究了灰色预测模型在弹药需求预测中的应用问题。首先,分析了影响弹药需求预测的主要因素;其次,分析了基本GM(1,1)模型存在的问题,提出了一种新的改进参数和时间响应序列的GM(1,1)模型;最后,分别用基本GM(1,1)模型和改进的GM(1,1)模型对一组弹药需求数列进行比较分析。结果表明,相对于基本GM(1,1)模型而言,改进的GM(1,1)模型的相对误差较小。     

活塞式航空发动机悬摆式配重组件失效原因及预防措施浅析

为了保证发动机的振动平衡,在发动机曲轴上安装有消除振动的配重块。作为曲轴上的重要部件,若高速旋转的配重块失效,将立刻造成发动机连杆、汽缸、机匣等部件损坏,引起航空事故。本文针对已出现的活塞式航空发动机案例,分析了悬摆式配重失效原因,提出了相应的改进措施。