基于CFD高精度算法的雷电电磁场研究

雷电空间电磁场一直是电磁领域研究的热门，成熟的算法例如有限时域差分法（FDTD），传输线矩阵法（TLM）以及频域的矩量法（MoM）在计算雷电问题方面都有广泛的应用。由于计算流体力学（CFD）中的Euler方程与电磁学中的Maxwell方程有着相同的守恒形式，而且采用间断伽辽金方法（DG）已经在流场问题上得到广泛的尝试，因此引入了基于计算流体力学的DG方法来离散时域Maxwell方程，并采用网格分区并行技术加速计算，使用基于DG的圆球雷达散射截面积（RCS）算例进行测试，数值结果一致表明DG算法在求解电磁场问题上的可行性，之后通过计算一段近场雷电通道的电场分布并与解析解、某算法仿真解对比，数据基本吻合，说明该方法适合于雷电电磁场的计算。     

机载托架自动校准系统的设计与实现

为了解决机载托架传统校准方法精度低、耗时、费力等问题,设计了一种高精度、高效率并且操作简单的成品托架自动校准系统。该系统运用调平精度较高的"循环多次"最高点不动调平方法,建立高精度机载托架校准的静力学数学模型,运用VC与Matlab的COM接口编程技术开发机载托架自动校准系统,并建立良好的人机交互界面。试验结果表明,利用该方法对机载托架进行校准,无论是校准精度还是校准效率都较传统方法有很大提高。     

Fault mode probability factor based fault-tolerant control for dissimilar redundant actuation system

This paper presents a Fault Mode Probability Factor (FMPF) based Fault-Tolerant Control (FTC) strategy for multiple faults of Dissimilar Redundant Actuation System (DRAS) composed of Hydraulic Actuator (HA) and Electro-Hydrostatic Actuator (EHA). The long-term service and severe working conditions can result in multiple gradual faults which can ultimately degrade the system performance, resulting in the system model drift into the fault state characterized with parameter uncertainty. The paper proposes to address this problem by using the historical statistics of the multiple gradual faults and the proposed FMPF to amend the system model with parameter uncertainty. To balance the system model precision and computation time, a Moving Window (MW) method is used to determine the applied historical statistics. The FMPF based FTC strategy is developed for the amended system model where the system estimation and Linear Quadratic Regulator (LQR) are updated at the end of system sampling period. The simulations of DRAS system subjected to multiple faults have been performed and the results indicate the effectiveness of the proposed approach.     

Evaluation of a regional real-time precise positioning system based on GPS/BeiDou observations in Australia

The performance of real-time (RT) precise positioning can be improved by utilizing observations from multiple Global Navigation Satellite Systems (GNSS) instead of one particular system. Since the end of 2012, BeiDou, independently established by China, began to provide operational services for users in the Asia-Pacific regions. In this study, a regional RT precise positioning system is developed to evaluate the performance of GPS/BeiDou observations in Australia in providing high precision positioning services for users. Fixing three hourly updated satellite orbits, RT correction messages are generated and broadcasted by processing RT observation/navigation data streams from the national network of GNSS Continuously Operating Reference Stations in Australia (AUSCORS) at the server side. At the user side, RT PPP is realized by processing RT data streams and the RT correction messages received. RT clock offsets, for which the accuracy reached 0.07 and 0.28?ns for GPS and BeiDou, respectively, can be determined. Based on these corrections, an accuracy of 12.2, 30.0 and 45.6?cm in the North, East and Up directions was achieved for the BeiDou-only solution after 30 min while the GPS-only solution reached 5.1, 15.3 and 15.5?cm for the same components at the same time. A further improvement of 43.7, 36.9 and 45.0 percent in the three directions, respectively, was achieved for the combined GPS/BeiDou solution. After the initialization process, the North, East and Up positioning accuracies were 5.2, 8.1 and 17.8?cm, respectively, for the BeiDou-only solution, while 1.5, 3.0, and 4.7?cm for the GPS-only solution. However, we only noticed a 20.9% improvement in the East direction was obtained for the GPS/BeiDou solution, while no improvements in the other directions were detected. It is expected that such improvements may become bigger with the increasing accuracy of the BeiDou-only solution.     

航空电子产品电磁环境效应模块化设计方法

对高强度辐射场（HIRF）环境特点与干扰类型进行分析，采用理论计算、计算机仿真技术（CST）的仿真分析及实测等方法分别对某型飞机航空电子系统综合显示单元的外部强电磁辐射场孔缝耦合、场线耦合及芯片前端电路影响关键芯片的相关规律进行了研究，给出了相关设计建议。结果表明，可通过分析孔缝、场线耦合获得进入关键芯片前端电路的电磁干扰能量，再结合关键芯片前端电路网络对干扰的插入损耗分析，获得关键芯片在外部强场激励下的感应电压。     

预测悬停旋翼跨音速流动的一种组合自由尾流/CFD方法

一种新的组合自由尾流 / CFD方法用于悬停旋翼流动的 CFD解中以考虑实际尾流的作用 .用文中描述的尾流分析方法研究了螺旋尖涡的运动 .首先从广义尾流模型开始 ,用半经验公式模化了涡核对旋翼尾流的作用 ;然后在环量收敛和尾迹收敛的条件下完成了自由尾迹计算 ;最后应用 Jameson有限体积龙格 -库塔推进格式求解了欧拉方程 .所得结果与相关文献和实验数据进行了比较     

晶体管h参数微变等效电路的研究

晶体管h参数微变等效电路是电子技术中求解低频、小信号放大电路常用的分析方法.本文通过具体分析,将模拟放大电路进行了新的分类,并且明确而系统地给出运用微变等效电路求解各类模拟放大电路动态指标Av、ri和γ0公式、解题难点及规律.     

一种用于人体早期病变诊断的仪器

根据探针在人体穴位电流量的变化情况 ,具体分析了该仪器电路设计的工作原理、电路结构及具体的使用方法。     

行星际结构与准平行无碰撞激波的相互作用

应用一维混合模拟方法数值研究了高密度等离子体团和行星际激波与准平行无碰撞激波的相互作用．结果表明，由于推平行无碰撞激波上游的大振幅低频波动的散射，除了在通过激波过渡区时稍有压缩外，等离子体团从激波的上游开始就一直是不断弥散的．行星际激波在向准平行无碰撞激波靠近的过程中，会在其上游产生大振幅的低频波动，同时行星际激波的强度不断增加，最后和准平行无碰撞激波会并成一个新的激波，在新激波前继续有大振幅的低频波动产生