局部后掠型栅格舵的气动特性研究

针对栅格舵(翼)技术的主要缺点——跨声速壅塞和阻力高的问题。以简化栅格为研究对象,采用数值分析方法开展了P型和V型局部后掠对气动特性的影响研究,并开展了不同后掠角对气动特性的影响研究。研究发现,局部后掠方式能够弱化或消除亚声速背风区的分离问题,减小跨声速区激波与边界层干扰,解决栅格舵固有的跨声速壅塞和阻力大的问题。局部后掠对栅格减阻有显著效果,尤其是高超声速段,同时能够增加单位浸润面积的法向力,从而提高栅格舵的操纵效率。     

卫星结构基础加速度激励及界面力识别试验研究

针对某卫星结构模型,开展基于实测卫星结构加速度的卫星基础激励和星-箭连接界面动载荷反演试验研究.首先,根据卫星结构和试验条件,设计了用于测量星-箭界面传递载荷的工装;其次,基于卫星结构模态试验和有限元模型修正技术,获取了卫星结构的高保真有限元模型;进一步,开展基础激励下的卫星结构模型振动试验,利用动载荷识别技术获取振动...     

基于不完整正弦基础激励响应数据的模型修正方法

文章直接应用航天器正弦振动试验所获取的结构动力学特性响应数据,开展了模型修正方法的研究。在试验数据不完整时,需进行模型缩聚。首先对比分析了Guyan缩聚和IRS缩聚方法的优缺点和适用范围;然后以缩聚后模型为基础,推导了基于基础激励响应数据的模型修正方法;最后以GARTEUR桁架结构的不完整的基础激励试验数据为基础对归一化的结构参数进行修正。结果表明:IRS缩聚模型修正后对模态频率具有良好的复现能力和预示能力,对响应曲线的修正也得到了明显改善。     

基于低碳经济的环京津贫困带发展模式研究

在受到资源环境约束的当代,经济发展必须采取低碳发展模式,环京津贫困带的发展更是如此。改革开放以来,环京津贫困带与京津郊县的发展差距越来越大。其中的原因是多方面的,既有京津方面的因素,也有河北方面的责任。在保证区域生态安全的前提下,促进"环京津贫困带"的发展,必须发展低碳经济,创新发展模式。     

阴影环境下陆地移动卫星信道模型及仿真研究

在对陆地移动卫星信道传播特性分析的基础上,建立阴影环境下移动卫星信道的混合模型,并采用随机数产生器实现了该信道模型的统计特性仿真。通过与实测数据的统计特性进行比较,验证了该信道模型和仿真实现方法的正确性。由于移动卫星信道是一个复杂的时变随机信道,所以,通过随机数产生器产生的统计特性具有很好的普适性。     

空间飞行器自动对接系统的多变量模型参考反馈设计方法

本文从两空间飞行器交会对接过程最后接近阶段的飞行特性出发,利用多变量频域理论,给出了空间飞行器自动对接系统的多变量模型参考反馈设计方法.     

一种改进的基于模糊-粗糙集的属性约简算法

FRSAR(Fuzzy-rough Set Attribute Reduction)是一种基于模糊-粗糙集的属性约简算法,它可以避免离散化时数据信息的丢失,但是该算法中决策属性对条件属性集依赖度的计算设计的不是很完善.本文提出了一种改进的FRSAR算法,它只考虑能够使属性集依赖度增大的属性,这样就降低了计算量.实验结果表明,改进算法和原有算法得到相同的约简结果,但是改进算法的执行时间大大降低.     

Supersonic Two-Dimensional Minimum Length Nozzle Design at High Temperature. Application for Air

When the stagnation temperature of a perfect gas increases, the specific heat ratio does not remain constant any more, and start to vary with this temperature. The gas remains perfect, its state equation remains always valid, except it will name in more calorically im-perfect gas or gas at High Temperature. The goal of this work is to trace the profiles of the supersonic Minimum Length Nozzle with centered expansion when the stagnation temperature is taken into account, lower than the threshold of dissociation of the molecules and to have for each exit Mach number several nozzles shapes by changing the value of the temperature. The method of characteristics is used with a new form of the Prandtl Meyer function at high temperature. The resolution of the obtained equations is done by the second order of finite differences method by using the predictor corrector algorithm. A study on the error given by the perfect gas model com-pared to our model is presented. The comparison is made with a calorically perfect gas for goal to give a limit of application of this model. The application is for the air.     

Static aeroelastic analysis including geometric nonlinearities based on reduced order model

This paper describes a method proposed for modeling large deflection of aircraft in non-linear aeroelastic analysis by developing reduced order model (ROM). The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geo-metric nonlinearities; meanwhile, the non-planar effects of aerodynamics and follower force effect have been considered. ROMs are computational inexpensive mathematical representations com-pared to traditional nonlinear finite element method (FEM) especially in aeroelastic solutions. The approach for structure modeling presented here is on the basis of combined modal/finite ele-ment (MFE) method that characterizes the stiffness nonlinearities and we apply that structure mod-eling method as ROM to aeroelastic analysis. Moreover, the non-planar aerodynamic force is computed by the non-planar vortex lattice method (VLM). Structure and aerodynamics can be cou-pled with the surface spline method. The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to anal-ysis based on the FEM and experimental result.     

基于粗糙集属性约简和支持向量机的变压器故障诊断

针对油浸式变压器的故障诊断问题,提出一种利用差异化的粗糙集属性约简与有向无环图-支持向量机(DAG-SVM)相结合的方法实现变压器故障类型的快速诊断。该方法首先通过油浸液中溶解气体量的历史数据及其对应的故障类型建立原始故障决策表;然后利用等频率间隔划分法对条件属性数据作离散化处理,利用差分矩阵对决策表信息进行差异化属性约简,建立每两类故障间的诊断规则,消除对决策结果区分度较低的冗余属性;最后根据约简属性的对应数据作为特征向量输入,构建有向无环图-支持向量机多分类诊断网络,进而实现对故障类型的判断。仿真实例表明,该方法在系统检测中提高了故障诊断的准确率。