基于经验的工程变更传播路径预测方法

 针对航空产品工程变更不易预测传播路径的问题,本文利用信息论和统计学的有关原理,提出了一套基于经验的工程变更传播路径预测方法。利用熵和互信息的概念,从海量经验数据中获取在预测过程中起到重要作用的参数;以其为样本空间,提出了一种从语义和变更影响两个角度计算变更参数相似度的算法;基于贝叶斯公式,分析了多因素情况下,相关参数的被影响概率,以此作为判断变更路径的依据;最后,以某型号航空涡轮叶盘为例对本文方法进行了验证,结果表明本文方法具有一定的准确度和优越性。     

带扰流片的升力风扇操纵特性数据采集系统设计

以带扰流片的升力风扇为动力系统的无人机,在动力学建模和控制方式上与传统升力风扇无人机有很大不同,升力风扇的操纵特性是这类升力风扇无人机动力学建模的关键,而目前国内尚未检索到对此进行研究或实验的报告或文献。因此,为了研究带扰流片的升力风扇动力系统的动态操纵特性,利用LabVIEW设计并制作一套动态数据试验采集系统,设计试验输入,完成带扰流片的升力风扇操纵特性动态数据采集,所获得数据及后续建模过程表明本试验采集系统是正确、有效的。     

利用热平衡试验稳态数据修正对接机构热模型

根据热平衡试验数据与计算结果的比较,分析两者存在差异的原因,用热平衡试验稳态工况数据修正对接机构热模型中的单元划分和热网络方程。研究了对热网络方程修正的方法,基于参数化和节点群概念改进参数化节点群整合方法,以明显减少需修正系数的数量,并与分级修正和局部修正综合,提高热网络修正方法的实用性。算例表明：通过热模型修正使温度计算值与试验值的偏差达到允许的要求,表明该热模型修正方法有效。     

星地遥感数据压缩的差分编码方法研究

为了提高星地传输的工作效率,文章以信息论为理论基础,提出一种差分编码方法用于星地遥感数据的传输。同时,鉴于地表覆盖本身的不确定度与应用需求的不同,提出了分区预测差分编码与保持立体测量精度的差分编码。这两种压缩策略可进一步显著提高差分编码的压缩比。     

内乘波式进气道与典型侧压式进气道的性能对比

采用流线追踪技术,基于一种有利于均匀性的基本流场,按内乘波式进气道设计方法生成了一个来流马赫数6.0且进出口形状均为矩形的内乘波式进气道。其设计马赫数、迎风面形状等因素均参照某典型侧压式进气道选取,以便与之对比。CFD计算结果给出了设计状态下该内乘波式进气道与某典型侧压式进气道的流量系数、总压恢复、动能效率等主要性能指标,发现该内乘波式进气道的各项性能参数均略优于侧压式进气道。在非设计马赫数、攻角、侧滑等非设计状态下类似的性能对比研究表明,该内乘波式进气道不仅在设计状态下可捕获98%的来流,而且在各非设计状态下也可捕获91%以上的来流,流量捕获性能优势明显。以上结果证实:实现三维压缩与激波贴口的内乘波式进气道是一种高性能的定几何进气道方案。     

一种信道系数服从高斯分布的8PSK信号信噪比盲估计算法

信噪比（SNR,Signalto Noise Ratio）是衡量通信系统性能的重要指标。针对传统信噪比估计算法要求利用训练序列或一帧数据范周内信道系数恒定等问题,提出了一种8PSK信号在信道系数服从高斯分布的衰落信道下肯信噪比估计算法。该算法取接收信号实部或虚部数值运算构成中间观测量,理论分析8PSK信号经过衰落信道后...     

Changes in hyperspectral reflectance signatures of lettuce leaves in response to macronutrient deficiencies

The adaptation of specific remote sensing and hyperspectral analysis techniques for the determination of incipient nutrient stress in plants could allow early detection and precision supplementation for remediation, important considerations for minimizing mass of advanced life support systems on space station and long term missions. This experiment was conducted to determine if hyperspectral reflectance could be used to detect nutrient stress in Lactuca sativa L. cv. Black Seeded Simpson. Lettuce seedlings were grown for 90 days in a greenhouse or growth chamber in vermiculite containing modified Hoagland’s nutrient solution with key macronutrient elements removed in order to induce a range of nutrient stresses, including nitrogen, phosphorus, potassium, calcium, and magnesium. Leaf tissue nutrient concentrations were compared with corresponding spectral reflectances taken at the end of 90 days. Spectral reflectances varied with growing location, position on the leaf, and nutrient deficiency treatment. Spectral responses of lettuce leaves under macronutrient deficiency conditions showed an increase in reflectance in the red, near red, and infrared wavelength ranges. The data obtained suggest that spectral reflectance shows the potential as a diagnostic tool in predicting nutrient deficiencies in general. Overlapping of spectral signatures makes the use of wavelengths of narrow bandwidths or individual bands for the discrimination of specific nutrient stresses difficult without further data processing.     

CubeSail: A low cost CubeSat based solar sail demonstration mission

CubeSail is a nano-solar sail mission based on the 3U CubeSat standard, which is currently being designed and built at the Surrey Space Centre, University of Surrey. CubeSail will have a total mass of around 3 kg and will deploy a 5 × 5 m sail in low Earth orbit. The primary aim of the mission is to demonstrate the concept of solar sailing and end-of-life de-orbiting using the sail membrane as a drag-sail. The spacecraft will have a compact 3-axis stabilised attitude control system, which uses three magnetic torquers aligned with the spacecraft principle axis as well as a novel two-dimensional translation stage separating the spacecraft bus from the sail. CubeSail’s deployment mechanism consists of four novel booms and four-quadrant sail membranes. The proposed booms are made from tape-spring blades and will deploy the sail membrane from a 2U CubeSat standard structure. This paper presents a systems level overview of the CubeSat mission, focusing on the mission orbit and de-orbiting, in addition to the deployment, attitude control and the satellite bus.     

基于FSK的测斜系统电路设计

本文重点阐述了测斜系统井下仪器数据采集单元和数据发送单元电路的设计及井上仪器解调电路的设计，给出了具体的电路设计结果及元器件参数。     

应用神经网络信息融合诊断航空发动机故障

研究了基于神经网络信息融合技术,同时结合模糊集合论对发动机气路部件进行故障诊断的方法,并以某型涡轴发动机为对象进行了仿真分析.研究结果表明该方法的故障诊断过程相对简单,对模型的精度要求不高,能够降低虚警、误报、漏报等情况的发生.