粉末高温合金盘件等温成形过程PID控制

对FGH96合金涡轮盘件等温锻造过程的控制进行了设计与仿真.采用PID控制,通过迭代学习算法,在SIMULINK下实现了PID控制仿真.应用于实际生产控制时,将对微观不可控参数的控制转化为对宏观可控参数的控制,并根据成形过程的不同阶段特征调整控制量,提高了生产效率和锻件质量.     

NOVEL RADAR SIGNAL SORTING METHOD BASED ON GEOMETRIC COVERING

With the increase of complexity of electromagnetic environment and continuous appearance of advanced system radars, signals received by radar reconnaissance receivers become even more intensive and complex. There- fore, traditional radar sorting methods based on neural network algorithms and support vector machine （SVM） cannot process them effectively. Aiming at solving this problem, a novel radar signal sorting method based on the cloud model theory and the geometric covering algorithm is proposed. By applying the geometric covering algo- rithm to divide input signals into different covering domains based on their distribution characteristics, the method can overcome a typical problem that it is easy for traditional sorting algorithms to fall into the local extrema due to the use of complex nonlinear equation to describe input signals. The method uses the cloud model to describe the membership degree between signals to be sorted and their covering domains, thus it avoids the disadvantage that traditional sorting methods based on hard clustering cannot deinterleave the signal samples with overlapped param- eters. Experimental results show that the presented method can effectively sort advanced system radar signals with overlapped parameters in complex electromagnetic environment.     

The characteristics of the semi-diurnal tides in mesosphere/low-thermosphere (MLT) during 2002 at Wuhan (30.6°N, 114.4°E) – using canonical correlation analysis technique

In this paper, we use canonical correlation analysis (CCA) method to investigate the semi-diurnal tidal winds in mesosphere and low thermosphere (MLT) region, observed by a newly installed meteor radar at Wuhan (30.6°N, 114.4°E), during the year 2002. In general, 4(3) effective semi-diurnal tidal pairs of patterns are obtained, which represent ∼2/3 total variances of the origin data set. These patterns are expected to be corresponding to the atmospheric oscillations within the semi-diurnal frequency band excited or modulated by different sources, i.e., the seasonal variations, the modulations by the planetary wave oscillations or the solar 27-day activity. Among all the patterns, the 1st pattern, which represents ∼1/3 of total variances, is the most notable. Its amplitudes show maximum values in spring and autumn, and the vertical wavelengths are longer in summer and shorter in winter, which is in line with the results obtained from traditional harmonic analysis. The vertical wavelengths of the higher order patterns (∼50 km) suggest the classic semi-tidal mode S(2, 4)/S(2, 5) is dominant.     

A320系列飞机大气数据系统的维护

大气数据系统是飞机重要的机载系统。本文结合系统原理、工程技术资料和自身维护经验,对A320系列飞机大气数据系统日常维护中的一些常见故障和特殊故障进行分析,给出维护建议,并对系统维护中的注意事项进行提示与强调。     

Induction of vascular endothelial phenotype and cellular proliferation from human cord blood stem cells cultured in simulated microgravity

Recent studies have demonstrated that stem cells derived from adult hematopoietic tissues are capable of trans-differentiation into non-hematopoietic cells, and that the culture in microgravity (microg) may modulate the proliferation and differentiation. We investigated the application of microg to human umbilical cord blood stem cells (CBSC) in the induction of vascular endothelial phenotype expression and cellular proliferation. CD34+ mononuclear cells were isolated from waste human umbilical cord blood samples and cultured in simulated microg for 14 days. The cells were seeded in rotary wall vessels (RWV) with or without microcarrier beads (MCB) and vascular endothelial growth factor was added during culture. Controls consisted of culture in 1 G. The cell cultures in RWV were examined by inverted microscopy. Cell counts, endothelial cell and leukocyte markers performed by flow cytometry and FACS scan were assayed at days 1, 4, 7 and at the termination of the experiments. Culture in RWV revealed significantly increased cellular proliferation with three-dimensional (3D) tissue-like aggregates. At day 4, CD34+ cells cultured in RWV bioreactor without MCB developed vascular tubular assemblies and exhibited endothelial phenotypic markers. These data suggest that CD34+ human umbilical cord blood progenitors are capable of trans-differentiation into vascular endothelial cell phenotype and assemble into 3D tissue structures. Culture of CBSC in simulated microg may be potentially beneficial in the fields of stem cell biology and somatic cell therapy.     

利用极化信息实现目标重构的算法研究

本文研究了一个光滑的、理想导电的、凸散射体的轮廓重构问题。主要从物理光学散射场的一阶修正项入手,分析了散射场的共极化和交叉极化信息与目标表面形状之间的关系,获得了散射场的极化特性与散射体表面上镜面点的主曲率密切相关的概念。借助于微分几何中曲面再现问题,重构出目标的外形图象。     

基于遥测数据的射前惯性测量系统稳定性检测方法

地地导弹惯性测量系统的稳定性直接影响导弹惯性导航系统导航的准确程度。介绍利用导弹射前的遥测数据及惯性测量系统误差补偿模型计算重力加速度和地球自转角速度方法,通过比较计算出的重力加速度和地球自转角速度与当地的实际值,检验惯性测量系统的稳定性,试验验证了该方法的正确性。     

引信目标RCS理论算法的发展及应用

论述了引信近场雷达散射截面(RCS)计算的特殊性及难点，同时介绍了计算引信目标RCS的多种高频理论预估方法，着重比较了物理光学面元法与几何光学法，并讨论了其他一些理论方法的特点。通过某型导弹的应用实例，指出了引信目标模型在雷达引信目标系统仿真中的重要作用。     

基于解耦和动态补偿的卫星控制系统设计

针对带大型挠性单翼太阳帆板和偏置动量的三轴稳定卫星,研究如何消除星内外干扰对姿态控制精度影响的卫星控制系统的设计问题。首先对星内外干扰进行了数值分析,进而阐明了在经典控制方案中干扰力矩对姿态控制精度的影响,指出经典控制在克服干扰力矩对姿态控制精度影响方面存在的不足之处。然后根据卫星的动力学特点,提出并论证了在设定角动量交换系统标称值条件下基于解耦和动态补偿的卫星控制系统的设计方案。最后深入分析了在该方案下太阳帆板挠性模态的稳定性。     

反馈结构模型及应用

反馈结构结构系统的排序原理是在递阶导次结构基础上提出来的，对于元素关系很复杂的系统，可能无法建立递阶层次结构模型，而反馈结构模型就为复杂关系提供了条件。在论述了建立反馈结构模型方法的基础上，对大型工程项目总设计单位的评审这一涉及因素多，关系复决策问题，进行了分析计算，在分析反馈结构模型时，借用了图论分析的方法，并建立了两类结构的运算模型，对反馈结构运算模型和递阶层次结构模型的排序结果进行了对比研究