橡胶密封材料加速系数研究

根据6种橡胶密封材料的加速老化试验数据和自然贮存数据,分别计算出加速系数,并对加速温度之间的加速系数进行了研究.结果表明:除氟橡胶外,橡胶密封材料的加速系数符合范德霍夫规则,即加速系数在2～4内.在无自然贮存数据的情况下,整机加速试验采用加速温度之间的加速系数作为橡胶密封材料的加速系数更接近于实际情况.     

极化敏感均匀圆阵中PARAFAC信号检测算法

分析了极化敏感均匀圆阵接收到的信号,该信号具有三线性模型特征。提出了极化敏感均匀圆阵中平行因子信号检测算法。该算法利用三线性交替最小二乘（TALS）算法估计出信源矩阵,然后对其进行判决。仿真结果表明;该算法误码率性能接近于非盲解相关方法;与非盲解相关方法相比,在较高的SNR情况下误码率相差不到2dB;且在阵列扰动情况下仍具有较好的误码率性能。该算法无需空域信息和极化信息,是一种盲鲁棒方法。     

多元统计在学生成绩分析的运用

运用多元统计中的聚类分析和因子分析方法,对大学生四年的学习成绩进行了成绩分析。通过聚类分析,给出了学生的分类;通过因子分析从中找出了影响该专业的主要课程,同时也给出了该专业学生成绩的综合评价模型。     

New method of enhancement using wavelet transforms applied to SODISM telescope

PICARD is a space-based observatory hosting the Solar Diameter Imager and Surface Mapper (SODISM) telescope, which has continuously observed the Sun from July 2010 and up to March 2014. In order to study the fine structure of the solar surface, it is helpful to apply techniques that enhance the images so as to improve the visibility of solar features such as sunspots or faculae. The objective of this work is to develop an innovative technique to enhance the quality of the SODISM images in the five wavelengths monitored by the telescope at 215.0?nm, 393.37?nm, 535.7?nm, 607.1?nm and 782.2?nm. An enhancement technique using interpolation of the high-frequency sub-bands obtained by Discrete Wavelet Transforms (DWT) and the input image is applied to the SODISM images. The input images are decomposed by the DWT as well as Stationary Wavelet Transform (SWT) into four separate sub-bands in horizontal and vertical directions namely, low-low (LL), low–high (LH), high-low (HL) and high–high (HH) frequencies. The DWT high frequency sub-bands are interpolated by a factor 2. The estimated high frequency sub-bands (edges) are enhanced by introducing an intermediate stage using a Stationary Wavelet Transform (SWT), and then all these sub-bands and input image are combined and interpolated with half of the interpolation factor α/2, used to interpolate the high-frequency sub-bands, in order to reach the required size for IDWT processing. Quantitative and visual results show the superiority of the proposed technique over a bicubic image resolution enhancement technique. In addition, filling factors for sunspots are calculated from SODISM images and results are presented in this work.     

Spatial asymmetry in topside ion density and vertical E × B plasma drift velocity within 75°E–95°E

The ion density measured by the Ionospheric Plasma and Electrodynamics Instrument (IPEI) on board the ROCSAT -1 over the 75°E and 95°E meridian at 600km altitude has been utilized to examine the latitudinal and longitudinal distribution within the Indian sector, in particular, the north-south and east-west asymmetries of the equatorial ionization anomaly (EIA). A longitudinal gradient in ion density at 600?km higher towards 95°E develops during the noontime and afternoon hours when the EIA is at its peak. The density gradient persists till evening hours when pre-reversal enhancements occur. The vertical E?×?B plasma drift velocity measured simultaneously by ROCSAT -1 for the same space-time configuration has also been studied. In addition to diurnal, seasonal and solar activity variations in E?×?B drift velocity, the longitudinal gradient is also observed. The EIA at the altitude of 600?km peaks at different latitudes and are mostly asymmetric about the magnetic equator. From midnight till 0800 LT, the ion density across the equator is nearly uniform in the equinoxes. But in the solstices, the density exhibits a north-south gradient. In the June solstice, density is higher in the northern hemisphere and decreases gradually towards south. The gradient in density reverses in December solstice. Normally, the EIA peaks within 1200 LT and 1600 LT while around 2000 LT, pre-reversal enhancement of ionization occurs affecting the EIA evening structure. The strength of the EIA also exhibits seasonal, year-to-year and hemispheric variations. The longitudinal asymmetry of drift velocity along 75°E and 95°E longitude sectors is the contributing factor behind the observed longitudinal asymmetry in ion density. Significant positive correlation between the strength of the EIA and E?×?B drift is observed in both longitudes.     

基于工程实践的民机金属结构ADR确定方法研究

偶然损伤额定值（ADR）的确定主要依赖用户（航空公司）和设计部门的经验。本文在对民机结构偶然损伤额定值（ADR）体系做简介的基础上,针对如何通过工程实践确定影响ADR的各因素指标等级,给出了采集工程实践数据的方法,以及统计数据的处理方法,确定出各指标等级。以前起落架舱壁板为例,确定出其ADR及检查间隔,结果与实际相符,验证了方法的正确性,为民机初始维修大纲的制定提供一种有效的方法。     

II型裂纹扩展与绝热剪切带传播的数值对比

通过数值计算的方法,对比绝热剪切带内裂纹扩展和预制II型疲劳裂纹扩展的动态性能参数。分析热塑失稳现象中裂纹的传播与绝热剪切带传播的关系。采用ABAQUS/CAE进行二维模型建立,预制疲劳裂纹和绝热剪切带,分析计算了材料在2种情况的应力应变时间曲线、II型动态应力强度时间历程以及裂纹扩展速度。计算结果表明,预制绝热剪切带与预制疲劳裂纹对于材料的破坏方式影响一致,即裂纹跟随绝热剪切带传播最终导致材料失效。     

Analytical method of dynamic properties of FRP based on micromechanical level

A mathematic model is proposed for predicting the dynamic properties of fiber reinforced plastic composites(FRP) with interphase. Dynamic properties mainly include loss factors and elastic moduli. The results of elastic moduli from the present model are compared with other models. Elastic moduli E11, E22, G12, G23 and loss factors η11, η22, η12 and η23 of FRP are calculated and a study of the effect of elastic modulus EIand loss factor ηI of interphase on dynamic properties in FRP is carried out here. In this paper, E11 linearly increases with EI, but the growth rate is slow. E22, G12, G23 increase rapidly for lower value of EI. The longitudinal loss factor g11 decreases with the increase of EIin the case of ηI 0.0026. But η11 linearly increases with EIin larger range of ηI, ηI≥ 0.0026. On the contrary, transverse loss factor η22, transverse shear loss factors η23 and longitudinal shear loss factors η12 increase with increase of EIin the case of lower value of ηI, but decreases at larger value of gI. And they also show insensitivity to EIat higher value.     

面向数字化装配生产过程的动态调度方法

针对数字化装配实际生产过程中动态扰动因素造成静态调度失效问题,建立面向数字化装配生产过程的动态调度模型。模型考虑了机器故障、人员流失和不合格产品等动态扰动对装配过程的影响,建立飞机大部件数字化装配工艺流程描述模型。在此基础上计算预调度方案,扰动产生时刻重新计算调整预调度方案。将资源利用率、平均生产率和作业平衡系数等指标作为优化目标,结合多目标优化遗传算法求解模型的Pareto最优解,得到多目标优化的装配作业调度方案。     

装备时延校准及监控技术研究CSCD

装备时延校准误差是靶场测控系统中事件记录和交会定位的重要误差因素,其精确校准是实现装备时间同步的关键技术。针对装备时延问题展开研究,提出了一种物理含义清晰、易于测量的装备时延定义,实现了离散站点装备时延校准,验证了基于改进型B码的装备时延校准监控的有效性。试验结果表明,时延校准的精度达到了十微秒量级。