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.     

远程终端有效性测试的介绍及分析

综述了MIL -STD -1 553BRT有效性测试计划的诞生、发展及其应用情况 ,并对国内在RT有效性测试方面的研究与应用进行了介绍     

利用改正数信息的北斗三号实时精密单点定位及性能分析

北斗三号全球卫星导航系统已正式建成并开通服务。为了利用实时改正数信息系统地揭示北斗三号精密单点定位性能，并为用户提供理论依据和应用参考，首先解算了卫星实时精密轨道、钟差及其改正数，分析了其精度。然后基于实时改正数信息，利用监测站广播星历和观测数据，分别进行了双频静态、双频仿动态、单频静态和单频仿动态仿实时精密单点定位，以评估其性能。结果表明：北斗三号MEO卫星实时轨道和钟差精度均值分别约为12cm和0.2ns，满足实时精密单点定位需求。静态实时精密单点定位精度优于动态，双频优于单频，均可达到分米级。对于定位收敛时间，双频静态最短，约为40min；双频动态和单频静态均约为85min；单频动态最长，约为120min。     

应用于未来航电系统的互连标准--SCI/RT

SCI作为未来航电系统互连技术的首选标准,其协议本身不提供实时性的保证,不能直接应用于航电系统.本文介绍的SCI针对实时应用的扩展版本SCI/RT在实时性、可靠性、优先权等方面都进行了改进和增强,较好地满足了实时应用环境的要求.     

飞机环控温控系统的半物理仿真及在机电综合管理技术研究中的应用

机载机电系统综合控制管理(简称公管系统)是机载机电设备发展的必然趋势,为了研究公管系统对机电子系统的控制、管理功能,需要对子系统进行建模仿真。本文针对某型飞机环控温度控制系统工作过程对环控温度控制系统关键附件进行了数学建模,同时针对某课题研究内容的需要,研究如何采用半物理仿真的方法对飞机环控温度控制系统进行系统建模和环境仿真并进行了系统仿真验证试验,最后给出结论。     

盘管对接焊缝射线检测

采用小管径对接焊接接头的γ射线照相技术.按照JB/T4730.2-2005标准规定,根据工件特点和检验要求,选择适当的Se75-射线检验方法.用此种方法透照所要检验的管对接焊缝,用固定板固定射源很方便,只要将所要透照的管对接焊缝接头找出最佳偏移距离,将γ源置于偏移距离处,即可固定射源方便又快捷地进行检验.     

On Stabilizing Role of Parallel Inhomogeneous Flow on Low-frequency Space Fluctuations

A fundamental reality throughout the space plasma is the existence of magnetic field-aligned flows. It is usually believed that the spatial transverse shear in the parallel flow destabilizes many low frequency oscillations and this may be the origin of low frequency oscillations in the ionosphere (V. V. Gavrishchaka et al., 1998, Phys. Rev. Lett., 80, 728 and Phys. Rev. Lett.: 2000, 85, 4285). Here we show that this notion of destabilizing influence of the shear in the parallel flow can be changed altogether if one takes the effect of the flow curvature (second spatial derivative) into account. The transverse curvature in the parallel flow can overcome the destabilizing influence of the shear and can render the low frequency modes stable. It is shown that unlike flow shear the effect of flow curvature is sign- and mode-dependent. This revised version was published online in August 2006 with corrections to the Cover Date.     

航空电子系统MIL-STD-1553通信网络接口验证测试

MIL-STD-1553数据总线为航空电子系统提供了一个系统支撑数据交换网络,它是航空电子系统集成的纽带,其通信完成的质量直接影响航空电子系统设计的成败。本文首先介绍了航空电子系统MIL-STD-1553基于OSI模型的通信终端的基本结构;然后给出了对网络接口执行测试的内容,包括MIL-STD-1553标准协议验证测试、应用网络通信协议验证测试和实时通信验证测试。这三种类型的测试将全面验证MIL-STD-1553通信终端的设计是否满足MIL-STD-1553标准通信协议及航空电子系统通信协议的要求。