Effect of biases in integrity monitoring for RTK positioning

In road transport, continuous high-accuracy positioning is required in real time. To ensure the proper functioning and safety of vehicular applications, integrity monitoring (IM) is needed to protect from the positioning errors under a certain alert limit (AL) with a pre-defined probability of misleading information (MI). In this study, a detailed threat model is developed for real-time kinematic (RTK) positioning application of short baselines. The model distinguishes between ambiguity-float and -fixed scenarios, and considers the influences of phase and code multipath as well as between-receiver atmospheric residuals. With the float ambiguities temporally constrained, the bias contribution that propagates with time-updated ambiguities was studied analytically for the horizontal protection level (HPL) in IM. Based on real data from both static and kinematic experiments, HPL was computed along the direction of the semi-major axis of the horizontal error ellipse. In ambiguity-float and -fixed cases, the HPL was mostly several meters and decimetres, respectively. It was found that time-propagated biases play a dominant role in the ambiguity-float HPL, and among them, phase and code multipath had in general the largest contributions. For ambiguity-fixed case, the phase multipath was found to play a dominant role in the HPL. This shows the importance of considering the biases in the RTK IM for both the ambiguity-float and -fixed scenarios. Given a horizontal alert limit (HAL) of 5 m, the availabilities of ambiguity-float solutions were low, i.e., below 50% for the static roof tests and below 5% for the kinematic road tests. For the ambiguity-fixed scenario, with HAL at 0.5 m, integrity availability was nearly 100% for the static roof tests and above 85% for the kinematic road tests.     

Multi-scale strength analysis of bolted connections used in integral thermal protection system

Efficient and accurate strength analysis of bolted connections is essential in analyzing the integral thermal protection system(ITPS) of hypersonic vehicles, since the system bears severe loads and structural failures usually occur at the connections. Investigations of composite mechanical properties used in ITPS are still in progress as the architecture of the composites is complex. A new method is proposed in this paper for strength analysis of bolted connections by investigating the elastic behavior and failure strength of three-dimensional C/C orthogonal composites used in ITPS. In this method a multi-scale finite element method incorporating the global–local method is established to ensure high efficiency in macro-scale and precision in meso-scale in analysis.Simulation results reveal that predictions of material properties show reasonable accuracy compared with test results. And the multi-scale method can analyze the strength of connections efficiently and accurately.     

极化角对跟踪接收机相位影响分析

根据卫星通信中遇到的极化问题及其对移动地面站的影响,针对不同极化卫星间的差异,从电磁场理论中极化的定义和分类出发,给出不同极化电磁波电场信号表示方法,以某型移动卫通站天线馈源结构为例,介绍了不同状态下极化工作方式和线极化方式中线极化面调整的机理,然后结合单通道单脉冲跟踪接收机工作原理,对天线跟踪水平极化信标时线极化角与跟踪接收机相位间的关系进行了详细分析,为解决实际应用中遇到的跟踪接收机相位漂移问题提供了技术依据。     

民用飞机配电网络过流保护分析方法研究

飞机配电网络过流保护分析是验证飞机电网设计合理性、可靠性和安全性的重要内容之一.因此,主要对飞机配电网络过流保护分析方法进行了研究,并提出了一种特性曲线法.该特性曲线法基于导线载流特性曲线和电网保护装置过流保护动作特性曲线,分析方法简单、实用,可用于支持合格审定阶段飞机配电网络设计验证.     

基于C／S的信用合作银行综合业务处理网络系统的专用数据库开发

分析了信用合作银行综合业务处理网络系统采用专用分布式数据库的必要性，给出了相应的分布式数据库系统结构，针对该系统设计了专用数据库及其接口技术。     

BTT导弹地形跟踪/地形回避控制器设计方法

针对倾斜转弯(BTT)导弹地形跟踪/地形回避控制任务,在弹体坐标系下建立了导弹的动力学数学模型,将滚转通道独立解耦,俯仰-偏航通道耦合设计;依据H_∞混合灵敏度理论,设计了俯仰-偏航通道过载控制器和滚转通道滚转角控制器;通过六自由度非线性仿真,验证了设计方法的有效性。     

C/E表面镀Al膜的原子氧试验

为了提高C/E复合材料的导电性及耐空间环境的能力,应用电弧离子镀技术在C/E复合材料表面沉积了A l膜,研究了地面模拟原子氧环境对C/E复合材料表面镀A l前后的侵蚀、质损及A l膜的附着力、导电性的影响。通过XRD、SEM、FT-IR、万能拉伸测试仪、FZ-82数字式四探针测试仪等测试分析样品。结果表明:电弧离子镀A l膜微米级以上颗粒较多,但分布均匀,膜层致密,附着力达2 N/mm2以上;原子氧对C/E复合材料侵蚀明显,镀铝后具有明显的防护作用;原子氧侵蚀后的A l膜电阻率有所上升,但还是有较好的导电性;辐照后的A l膜附着力比辐照前反而增加,其机理尚待进一步研究。     

单元表面间辐射传递系数的新型计算方法

通过对辐射能量传递过程的分解，建立辐射传递系数与角系数之间的关系，提出了一种计算具有漫反射辐射界面特性的单元表面之间辐射传递系数的新型计算方法。该方法分离了单元表面辐射特性和几何特性对辐射传递系数的影响。分别采用新方法和蒙特卡洛法计算了立方体内部单元表面之间的辐射传递系数，并且从理论上对两种计算方法的耗时性和计算精度进行了分析比较。结果表明，相对于蒙特卡洛法，该方法所需的计算时间更少，而且不随单元表面吸收率的变化而变化；在计算精度上，该方法相对于蒙特卡洛法具有更高计算精度。     

基于级联耦合的大功率测量技术研究CSCD

讨论了采用级联耦合测量技术的大功率测量系统,指出大功率测量条件下引起测量不确定度的因素,搭建了基于该技术的大功率校准系统,减小了系统测量不确定度,实现了功率放大器的高精度校准和测量。     

不同来流条件对涡轮叶片表面颗粒沉积影响的实验研究

为了研究微颗粒在涡轮叶片表面的沉积特性,采用熔融态石蜡代替熔融态微颗粒,通过石蜡在平板表面的沉积来模拟真实涡轮叶片表面的微颗粒沉积,从而开展较低温度条件下微颗粒的沉积实验。通过实验观察石蜡在试验件表面附着固化分布,同时测量石蜡在平板表面不同位置的沉积量,研究了不同来流攻角、颗粒浓度对平板表面颗粒物沉积的影响规律,分析了等效加速实验的颗粒物沉积效果。结果表明：颗粒物沉积主要发生在平板前缘及压力面的中后部,前缘的颗粒沉积物质量远大于压力面和吸力面的。随着攻角的增大,压力面和吸力面沉积量显著增大,前缘变化不明显;随着来流颗粒浓度的增加,前缘和压力面的沉积量增加;对于已有等效加速实验准则,保持总粒子喷射质量相同,在颗粒浓度升高,实验时间变短的情况下,平板前缘位置的沉积量增大。