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51.
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White Rabbit(WR)时钟同步技术是综合了同步以太网、精密定时协议(IEEE1588v2)和数字相位测量技术而发展的分布式同步授时技术,能够实现数千米范围内多节点亚纳秒精度的时钟分发。该技术兼容标准以太网协议,不占用额外网络带宽,与数据链路直接集成,结构简单成本低。介绍了White Rabbit技术的基本技术原理及初步应用方法,并给出了各种拓扑结构下的测试结果。采用White Rabbit能很好地解决各种长距离多节点高精度授时需求,能够作为地基增强导航系统的关键支撑技术。 相似文献
53.
A. Hovhannisyan A. Chilingarian 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Particle detectors of worldwide networks are continuously measuring various secondary particle fluxes incident on Earth surface. At the Aragats Space Environmental Center (ASEC), the data of 12 cosmic ray particle detectors with a total of ∼280 measuring channels (count rates of electrons, muons and neutrons channels) are sent each minute via wireless bridges to a MySQL database. These time series are used for the different tasks of off-line physical analysis and for online forewarning services. Usually long time series contain several types of errors (gaps due to failures of high or low voltage power supply, spurious spikes due to radio interferences, abrupt changes of mean values of several channels or/and slowly trends in mean values due to aging of electronics components, etc.). To avoid erroneous physical inference and false alarms of alerting systems we introduce offline and online filters to “purify” multiple time-series. In the presented paper we classify possible mistakes in time series and introduce median filtering algorithms for online and off-line “purification” of multiple time-series. 相似文献
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从分析双混频时差(DMTD)测量系统的测量误差着手,对系统设计和使用中常磁到的一些理论和技术问题进行了探讨,这涉及到公共源的影响、移相器的作用、自校和测量中的其它问题。 相似文献
56.
根据**飞机上,CW-1002和Ⅱ-5的试飞结果,对两种产品的性能做了对比分析;对飞行中大气温度的获取方法提出了的新意见。 相似文献
57.
Wei Wang Bin Zhao Qi Wang Shaomin Yang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The Crustal Movement Observation Network of China (CMONOC) is one of the major scientific infrastructures, mainly using Global Positioning System (GPS) measurements, to monitor crustal deformation in the Chinese mainland. In this paper, decade-long coordinate time series of 26 continuous GPS sites of CMONOC are analyzed for their noise content using maximum likelihood estimation (MLE). We study the noise properties of continuous GPS time series of CMONOC for the unfiltered, filtered solutions and also the common mode signals in terms of power law plus white noise model. In the spatial filtering, we remove for every time series a common mode error that was estimated from a modified stacking of position residuals from other sites within ∼1000 km of the selected site. We find that the common mode signal in our network has a combination of spatially correlated flicker noise and a common white noise with large spatial extent. We demonstrate that for the unfiltered solutions of CMONOC continuous GPS sites the main colored noise is a flicker process, with a mean spectral index of ∼1. For the filtered solutions, the main colored noise is a general power law process, indicating that a major number of the filtered regional solutions have a combination of noise sources or local effects. The velocity uncertainties from CMONOC continuous GPS coordinate time series may be underestimated by factors of 8–16 if a pure white noise model is assumed. In addition, using a white plus flicker noise model, the median values of velocity errors for the unfiltered solutions are 0.16 (north), 0.17 (east) and 0.58 (vertical) mm/yr, and the median values for the filtered solutions are 0.09 (north), 0.10 (east) and 0.40 (vertical) mm/yr. 相似文献
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Conflict Detection and Resolution(CDR) is the key to ensure aviation safety based on Trajectory Prediction(TP). Uncertainties that affect aircraft motions cause difficulty in an accurate prediction of the trajectory, especially in the context of four-dimensional(4D) Trajectory-Based Operation(4DTBO), which brings the uncertainty of pilot intent. This study draws on the idea of time geography, and turns the research focus of CDR from TP to an analysis of the aircraft reachable space constrained by 4D waypoint constraints. The concepts of space–time reachability of aircraft and space–time potential conflict space are proposed. A novel pre-CDR scheme for multiple aircraft is established. A key advantage of the scheme is that the uncertainty of pilot intent is accounted for via a Space-Time Prism(STP) for aircraft. Conflict detection is performed by verifying whether the STPs of aircraft intersect or not, and conflict resolution is performed by planning a conflict-free space–time trajectory avoiding intersection. Numerical examples are presented to validate the efficiency of the proposed scheme. 相似文献