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251.
Mingkun Su Yanxi Yang Lei Qiao Xuyang Teng Huina Song 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(2):868-882
This study proposes an enhanced multipath mitigation method based on multi-resolution carrier-to-noise-ratio (CNR) model and adaptive statistical test strategy for real-time kinematic precise point positioning (PPP) applications. The multi-resolution CNR model is established with GPS observation data collected from DOY 152 to 181 of 2019 by 230 globally distributed IGS stations, which used to analyze the relevant factors affecting CNR. Statistical results indicate that the CNR is not only related to the satellite elevation, but also closely related to the receiver types and specific satellite. The maximum difference between different receivers can reach 20 dB for the same satellite at the same elevation. In addition, the performance of the CNR is also obviously different between each satellite, and the maximum difference between different satellites is about 10 dB for the same receiver at the same elevation. Hence, in terms of the method which is based on CNR information for multipath detection and mitigation, the independence of receiver types, satellite and frequency must be considered. With the above analysis, this study developed a multi-resolution CNR model based on different receiver types, different satellites and different elevation firstly. Then, combined with the adaptive statistical test strategy which is based on the difference of CNR between inter-frequency and the difference of CNR between adjacent epochs, the multipath can be detected effectively. For the epoch which affected by multipath, the down-weighted strategy based on CNR is adopted to mitigate the influence of multipath on positioning. Real-time kinematic PPP data are collected to assess the proposed method, and the results demonstrate that the proposed method can detect the multipath effectively, and the detection rate can reach 90.28%. Moreover, after adopting the mitigation strategy, the RMS bias of the east, north and up components are improved about 19.95%, 17.89% and 23.07% compared to the original results, respectively. It is worth noting that this proposed method is also suitable for other GNSS, such as GLONASS and BDS, but the corresponding CNR model must be established simultaneously. 相似文献
252.
253.
A parameterized geometry design method for inward turning inlet compatible waverider 总被引:1,自引:1,他引:1
Intensive studies have been carried out on generations of waverider geometry and hypersonic inlet geometry. However, integration efforts of waverider and related air-intake system are restricted majorly around the X43A-like or conical flow field induced configuration, which adopts mainly the two-dimensional air-breathing technology and limits the judicious visions of developing new aerodynamic profiles for hypersonic designers. A novel design approach for integrating the inward turning inlet with the traditional parameterized waverider is proposed. The proposed method is an alternative means to produce a compatible configuration by linking the off-the-shelf results on both traditional waverider techniques and inward turning inlet techniques. A series of geometry generations and optimization solutions is proposed to enhance the lift-to-drag ratio. A quantitative but efficient aerodynamic performance evaluation approach (the hypersonic flow panel method) with lower computational cost is employed to play the role of objective function for opti- mization purpose. The produced geometry compatibility with a computational fluid dynamics (CFD) solver is also verified for detailed flow field investigation. Optimization results and other numerical validations are obtained for the feasibility demonstration of the proposed method. 相似文献
254.
在众多影响UV-LIGA(Ultra-violet lithography Galvanik abformung)技术制备微细金属零件尺寸精度的因素中,SU-8胶溶胀性是最主要的。通常采用隔离带方法降低SU-8胶的溶胀性,以提高电铸微细零件的尺寸精度。由于贵重金属会沉积到隔离带内,造成了贵重金属的浪费,增加制造成本,因此该方法不适合贵重金属微细零件制造。针对隔离带方法的弊端,提出了半隔离带方法,在保证电铸微细金属零件尺寸精度的前提下,避免了贵重金属的浪费。另外,还采用电解液喷射方法实现了高电流密度电铸,缩短了电铸时间,进一步提高了电铸微细金属零件的尺寸精度。试验结果表明:采用半隔离带方法和高电流密度,可以有效提高金微细零件的尺寸精度,当电流密度提高到0.6A/dm2,金微细零件的尺寸精度可以达到5μm。 相似文献
255.
介绍了VB与MATLAB混合编程的4种方法,通过这些方法,可使VB的可视化界面和Matlab强大的计算及绘图功能得以实现,从而提高编程的效率,并在某产品CNC修磨机床的上位机数据处理软件中通过了验证. 相似文献
256.
为实现航空发动机控制系统在数字仿真阶段的多用户、多学科协同功能,提高设计研发效率,搭建了全数字综合仿真平
台 — —FWORKS。针对常规数字仿真软件难以实现多用户间并行开发的缺点,采用分布式设计架构,通过以太网络将多个服务端
软件和人机交互软件相互联系,实现并行开发人数不少于30人的功能。该平台集成了EmbeddedCoder、SVN等工具,具备多学科
协同仿真、模型和算法的存储调用等功能。通过集成硬件在环平台所需第三方软件及编译环境等,FWORKS实现了与硬件在环平
台的无缝对接。结果表明:FWORKS仿真结果与传统全数字仿真的误差小于0.4%,与硬件在环平台的误差小于1%,表明该平台
仿真具有较高的准确性以及功能的有效性,为控制系统设计人员提供了开放的综合仿真平台。 相似文献
257.
苏子波 《中国民航飞行学院学报》2012,(6):76-77,80
利用语料库提取《阿Q正传》中鲁迅描写阿Q时所用的隐喻,从认知的角度考察了这些隐喻的源域。结果表明:作者似乎将阿Q比作一个少不更事的顽童,既可怜,又可悲。还利用语料库考察了阿Q对他人的称呼语,他愤世嫉俗的称呼语背后隐藏的是他的弱者心态。 相似文献
258.
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260.
张娟 《中国民航学院学报》2000,18(2):28-31
加强对战备管理的控制是使航空公司达到其战备目标的一个主要方法。传统的控制方法,大都是首先制定目标,然后监督执行,通过反馈将输出与所希望的目标进行比较,最后,按照偏差重新调整系统。结战略管理的控制,就是用控制理论来进行战略管理。重点分析战略管理的特性,然后指出传统控制方法用于战略管理的缺陷,进而提出适合战略管理的控制方法。 相似文献