BP神经网络在波音737自动刹车故障诊断中的应用

随着人工神经网络研究的兴起,智能故障诊断技术成为近年来人们研究的一个热点问题。自动刹车是飞机起降时的重要装置,需要定期对其进行故障检测,以免形成飞行安全隐患,是飞机故障诊断的一个重要内容。本文从传统的BP神经网络算法出发,通过算法改进建立了波音737自动刹车故障诊断的神经网络模型,通过提取故障样本对网络进行训练和诊断,仿真结果显示这种方法能较理想地对波音737飞机自动刹车系统的故障进行分析和检测,对于建立波音飞机的故障自动诊断系统具有重要意义。     

Ti-22Al-25Nb合金ISM熔炼过程中的成分控制

采用X荧光光谱(XRF)分析水冷铜坩埚真空感应炉熔炼(ISM)加入和不加入稀土Y的Ti-22Al-25Nb合金铸锭成分,分析结果表明,在保证获得成分均匀的合金铸锭的情况下,Al的挥发烧损在28.94%～33.88%之间;加入at为0.5%～1%Y,Y的挥发烧损在w为17.20%～34.26%;采取提高熔化温度降低保温时间的措施可以降低Al的挥发烧损.     

水热法制备BiVO_4及其光催化性能研究

采用水热反应法并改变反应条件制备不同形貌和晶体结构的BiVO4可见光催化剂,并探讨不同形貌BiVO4的形成机制及其光催化活性的影响因素。借助X-射线衍射（XRD）、扫描电子显微镜（SEM）及固体紫外-可见漫反射光谱（DRS）对产品进行表征,并在可见光（λ〉420 nm）照射下考察其降解亚甲基蓝（MB）的光催化性能。结果表明,高温更有利于单斜型钒酸铋的生成,反应初始pH值对钒酸铋的形貌影响较大。反应过程中,前驱液中的颗粒通过溶解再结晶、定向聚集自组装、熟化过程最终形成不同形貌的钒酸铋颗粒。钒酸铋的光催化降解速率主要受其晶粒粒径和晶体微观应变的影响,晶粒粒径越大,微观应变越小,结晶度越好,降解速率越高。     

Analysis of electron structure of γ/α2 phase boundaries in ternary TiAl intermetallics

The electron structure of γ/α2 phase boundaries in lamellar colonies in Ti-47Al-2M（M=Nb, Cr, V） （mole fraction, %） alloys was theoretically investigated by Empirical Electron Theory of Solid and Molecules （EET） and the bond-length-difference （BLD） method. Average-Atom-Model was employed to calculate valence electron structure of TiAI intermetallics containing site substitution elements. On this basis, the boundary condition of electron movement was employed in the improved Thomas-Fermi-Dirac （TFD） theory to decide the continuity of the electron density of the lamellar colonies interface and it is found that of γ/α2 interface is continuous（△ρ〈10%）. Furthermore, it is found that adding alloying elements （including Nb, Cr, and V） can improve the electron density （ρ） of ）γ/α2 interfaces, and decrease the electron density difference（△ρ） of γ/α2 interfaces. Adding V element decreasing △ρ is more remarkable than other site substitution elements. According to electron structure study of γ/α2 interfaces in Ti-47Al-2M alloys, the added elements improve mechanical properties of the alloy in the following order： V〉Cr〉Nb.     

新能源发电并网中电能计量问题的研究

开发利用新能源已成为全球保障能源安全和实现可持续发展的重要举措。本文基于新能源发电并网的特点,着眼于电能计量系统的准确性、经济性和可靠性,对新能源发电并网中电能计量存在的问题进行了深入剖析。在此基础上,分别提出了低压和高压两种新能源发电并网方式下的多种电能计量解决方案,并对各方案的特点进行了分析。     

Effects of minor yttrium addition on hot deformability of lamellar Ti-45Al-SNb alloy

The effects of 0.3%（molar fraction, the same below） yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloy were investigated by simulated isothermal forging tests. The ingots with the nominal compositions of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y were prepared by induction skull melting. Simulated isothermal forging tests were conducted on Gleeble 1500D thermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of 1 100, 1 150, 1 200 ℃ and strain rates of 1.0, 0.1, 0.01 s^-1. The results show that yttrium addition remarkably improves hot deformability of Ti-45Al-5Nb alloy. An appropriate hot deformation processing parameter of Ti-45Al-5Nb-0.3Y alloy is determined as 1 200 ℃, 0.01 s^-1. The flow stresses are decreased by yttrium addition under the same compressive conditions. The activation energies of deformation Q are calculated as 448.6 and 399.5 kJ/mol for Y-free and Y-containing alloys, respectively. The deformed microstructure observation under 1 200 ℃, 0.01 s^-1 condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamic recrystallization. The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by yttrium addition should be attributed to that the smaller the original lamellar colonies, the lower the deformation resistance and activation energy of deformation are, and the more the dynamic recrystallization is.     

无卤阻燃聚乙烯的研究进展

综述了近几年国内外金属氢氧化物阻燃剂、磷系阻燃剂、氮系阻燃剂、碳族阻燃剂、膨胀型阻燃剂在聚乙烯复合材料中的应用与研究进展,最后对聚乙烯无卤阻燃复合材料进行总结.     

基于FPGA的高速实时光斑质心检测系统的设计

光斑质心检测是自由空间通信APT精跟踪子系统的关键技术之一,对此本文提出了基于FPGA的图像处理算法,主要采用3×3窗口模块和自适应阈值模块,先对CCD输入数据进行处理,判断光斑的范围,然后再运用光斑的质心算法对光斑所占的像元进行运算,得出光斑位置的脱靶量,最后通过串口送至总控单元处理。实验达到了3000帧／s的脱靶量帧速,精度为2urad的技术指标,实现了高速率、高精度的精跟踪要求。     

颚式破碎机齿板可靠性模糊设计

运用模糊随机理论对颚式破碎机齿板进行加载。通过可靠性分析,从众多不确定参数中获取了对齿板应力和应变影响较大的参数,在理论上为如何改善齿板结构强度指明了方向。