非化学平衡条件下膏体富燃料推进剂的热力计算

膏体富燃料推进剂一次燃烧处于非平衡条件下,本文建立了非平衡条件下热力计算的理论模型以及不同热力学状态下求解平衡组分和燃烧温度的控制方程组。对给定配方的膏体富燃料推进剂在非平衡条件下的燃烧温度进行了计算,并对本文采用的方法进行了验证,证明是可行的。     

卫星光通信APT控制系统H∞设计

 捕获瞄准跟踪(APT)控制系统的设计是影响整个星间光通信系统性能的重要因素。利用指向偏差的概率分布阐述了卫星光通信过程中捕获概率、跟踪误差及误码率受卫星平台振动和终端装置参数摄动的影响,通过功率谱分析了卫星平台振动在低频段、对象不确定性在高频段对指向偏差的影响,并对其进行了模型化分析。采用H_∞控制混合灵敏度设计方法同时抑制干扰和处理受控对象不确定性问题进行控制器设计。仿真验证表明该方法得到的控制器对平台干扰具有抑制力,对对象摄动具有鲁棒性。     

基于后掠台阶流动的航空发动机尾锥流线型设计方法

受后掠台阶流动中旋涡形状类似于航空发动机中尾锥的启示,提出了发动机尾锥的流线型设计方法。对平面后掠台阶流场通过流线捕捉技术得到尾锥母线,该母线绕中心轴旋转所得即为流线型尾锥。通过全三维湍流数值模拟,对流线型尾锥和具有相同扩张比的圆锥形尾锥的流场进行了比较,得出了流线型尾锥在气流参数分布、流动组织上均具有优异性能的结论。     

Research on the Plane Multiple Cracks Stress Intensity Factors Based on Stochastic Finite Element Method

Taylor stochastic finite element method (SFEM) is applied to analyze the uncertainty of plane multiple cracks stress intensity factors (SIFs) considering the uncertainties of material properties, crack length, and load. The stochastic finite element model of plane multiple cracks are presented. In this model, crack tips are meshed with six-node triangular quarter-point elements; and other area is meshed with six-node triangular elements. The partial derivatives of displacement and stiffness matrix with respect to all the random variables obtained by Taylor SFEM are derived. Meanwhile, the mean and variance expressions of SIF under uncertain factors are also derived. Parallel double-crack illustrative example of using the proposed method is given. The calculation results indicate that the uncertainty of SIF is influenced by the distance of the cracks, the smaller the distance of cracks is, the greater the SIF uncertainty is, and the uncertainties of material elastic modulus, load and crack length markedly affect the uncertainty of SIF; and the Poisson ratio of material has little influence. Among the variables, the elastic modulus has the greatest effect on SIF uncertainty. The next is external load. The crack length has lower effect on SIF uncertainty than both the elastic modulus and external load.     

Accurate 3D Target Positioning in Close Range Photogrammetry with Implicit Image Correction

Accurate three-dimensional (3D) target positioning is of great importance in many industrial applications. Although various methods for reconstructing 3D information from a set of images have been available in the literature, few of them pay enough attention to the indispensable procedures, such as target extraction from images and image correction having strong influences upon the 3D positioning accuracy. This article puts forward a high-precision ellipse center (target point) extraction method and a new image correction approach which has been integrated into the 3D reconstruction pipeline with a concise implicit model to accurately compensates for the image distortion. The methods are applied to a copyright-reserved close range photogrammetric system. Real measuring experiments and industrial applications have evidenced the proposed methods, which can significantly improve the 3D positioning accuracy.     

直升机旋翼试验台动力学分析及建模

直升机旋翼动平衡试验台是一种主要的直升机旋翼测试设备之一,对试验台进行动力学分析和建模可以提高试验台的控制精度和试验的效果.在分析试验台结构和功能的基础上,简化了桨叶变距拉杆的载荷,通过对自动倾斜器的受力分析,得出了旋翼系统的动态模型.通过对液压系统和旋翼系统的联合仿真,分析了系统在旋翼姿态变化时的动态响应和交互耦合影响,初步了解了系统在各种不同负载特性下的响应,为试验台的姿态调节、激振的精度提高和进行理论研究提供基础,并为地面旋翼试验台系统的设计和控制提供依据.     

小尺寸封装(SOP)器件焊点可靠性研究

从器件引脚镀层种类、厚度、焊接参数和焊盘设计等几个方面对小尺寸封装(small outline package,简称SOP)器件焊点可靠性的影响作了分析,给出了提高焊点可靠性的方法,并通过UG软件建立了电路板和SOP焊点的三维有限元模型,进行了SOP器件焊点在近似试验载荷条件下的应力应变三维有限元数值模拟,得出了焊点内部精确的应力应变分布。     

控制力矩陀螺框架高精度周期随动控制

为实现控制力矩陀螺框架伺服系统的高精度周期随动控制,采用比例积分微分(PID,Proportion Integration Differentiation)控制器结合重复控制器的控制方式,PID控制器实现框架伺服系统静态和匀速运动的高精度控制,插入式重复控制器实现对周期性输入信号的精确跟踪.对控制力矩陀螺框架系统进行了建模,设计了PID控制器与插入式重复控制器,并分析了重复控制器的稳定性条件、稳态跟踪性能和对扰动的抑制能力.仿真结果和实验结果表明:采用插入式重复控制器使控制力矩陀螺跟踪1Hz给定速度信号时的稳态跟踪误差大幅减少.PID控制器结合插入式重复控制器结构简单,两者可分开独立设计,参数设计容易.     

钼酚醛树脂成碳率测量的影响因素及其不确定度

酚醛树脂的成碳率受样品自身及成碳条件的各种因素影响,使其成碳率的热重法(TGA)测量结果因试验条件不同而不同.为掌握其中关系,以便对酚醛树脂体系的成碳率做出正确的测评,本文通过试验考察了样品粒径分布、氮气流速、样品量等因素对钼酚醛树脂成碳率测量结果的影响程度与规律,并对其测量不确定度进行了分析.结果表明,样品粒径分布与样品量是影响钼酚醛树脂成碳率的主要因素,在常规测试条件下,TGA法测量钼酚醛树脂成碳率的扩展不确定度为0.9%.     

ZnO纳米颗粒薄膜的制备与光致发光特性研究

利用高分子包覆法(Polymer Capping Method)在Si衬底上生长了颗粒分布均匀、致密的纳米ZnO薄膜.样品的形貌和光学性能分别使用SEM,AFM和PL谱进行表征.实验发现,前驱体溶液的pH值对纳米颗粒的分散性和尺寸有很大影响,进而影响紫外发光峰位.在本实验条件下,随纳米颗粒尺寸增大,PL谱的紫外发光峰红移,符合量子尺寸效应.