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| 1 | Impact of China’s high speed train window glass on GNSS signals and positioning performance显示文摘High speed train(HST)is an excellent platform to perform ultra-high spatial and temporal resolution observations of atmosphere using global navigation satellite systems(GNSS).However,we find that signal attenuation caused by HST window glass is a major barrier for HST-based GNSS applications inside HST chambers.A field experiment is conducted to analyze the effect of HST glass on GNSS signal propagation.In the experiment,GNSS observations are collected and analyzed from a receiver covered with an HST window glass and one with an open-sky view.The size of the HST window glass is 670 mm×720 mm,with a thickness of 34 mm.The window glass is a double-glazing glass in which each layer has an actual thickness of 6 mm,and the two layers are separated by an air gap of 22 mm.The experiment results indicate that HST window glass can cause significant degradation to GNSS signals and even loss of tracking of the signal.Based on statistical results,HST window glass causes 39%,56%,49%,and 59%loss in GPS,GLONASS,Galileo,and BDS signals,respectively.Additionally,up to 20 dB-Hz of carrier-to-noise ratio(C/N0)degradation is also observed in the remaining observations.The significant signal attenuation and loss further lead to the decrease in the number of tracked satellites and occurrence of more cycle slips.The results of the study indicate that 44-230 cycle slips are detected for the HST glass-covered receiver whereas the receiver without glass does not exhibit more than 16 cycle slips.Additionally,the number of GNSS satellites tracked by the HST glass-covered receiver is reduced by 65%owing to the loss of signal.Furthermore,GNSS positioning performances from two receivers are also tested.With respect to GPS+GLONASS static precise point positioning(PPP),HST glass causes a degradation of 1.516 m and 1.159 m in the single-frequency and dual-frequency three-dimensional positioning accuracy,respectively.With respect to the GPS+GLONASS kinematic PPP,the accuracy degradations for single-frequency and dual-frequency kinematic PPP are 2.670 m and 4.821 m,respectively. | Zhizhao Liu Yangzhao Gong Letao Zhou | 2020 | Satellite Navigation2020，1，1： | 1 |
| 2 | Web and Mobile Computation based VRS/RTK Positioning and the Service System Development 显示文摘 | Huang Dingfa Zhou Letao Liao Hua | | Acta Geodaetica et Cartographica0，，： | 1 |
| 3 | Opportunities for ionic liquid-based electrolytes in rechargeable lithium batteries显示文摘Ionic liquids(ILs)have been deemed as promising electrolyte materials for building safer and highly-performing rechargeable lithium batteries,owing to their negligible volatility,low-flammability,and high thermal stability,etc.The profound structural designability of IL cations and anions allows relatively facile regulations of their key physical(e.g.,viscosities,and ionic conductivities)and electrochemical(e.g.,anodic,and cathodic stabilities)properties,and therefore fulfills the critical requirements stipulated by various battery configurations.In this review,a historical overview on the development of ILs for nonaqueous electrolytes is provided,and the correlations between chemical structures and the basic properties of ILs are discussed.Furthermore,the key achievements in the field of IL-based electrolytes are scrutinized,including liquid electrolytes,polymer electrolytes,and composite polymer electrolytes.Based on literature reports and our previous work in this field,possible strategies to improve the performance of IL-based electrolytes and their rechargeable batteries are discussed.The present work not only provides the status quo in the development of IL-based electrolytes but also inspires the structural design of ILs for other kinds of rechargeable batteries(e.g.,sodium,potassium,zinc batteries). | Xingxing Wang Letao Jin Wenfang Feng Zhibin Zhou Heng Zhang | 2023 | Science China Chemistry2023，66，12： | 0 |
| 4 | Global precision analysis of carrier phase relative positioning in BeiDou navigation satellite system and United States global positioning system显示文摘In this paper, we derived a high-efficiency formula for calculating the precision of carrier phase relative positioning,analyzed the various factors that affect the positioning accuracy using the carrier phase, and proposed the concept of using a frequency dilution of precision to describe the quantitative effect of different frequency combinations on the positioning precision. To this end, we computed and plotted the global spatial distribution map of the relative positioning dilution of precision for single-day solution, half-hour solution, and single-epoch solution of the global positioning system(GPS), regional Beidou navigation satellite system(BDS2), future global Beidou navigation satellite system(BDS3), and their fusion systems.Using processing software with autonomous intellectual property rights(GCN and VENUS/ARSNet), we solved the measurement data and examined the positioning precision of the single-day solution and single-epoch solution of GPS and BDS2.The analysis demonstrated that the B1/B2 frequency positioning precision of BDS2 was better than that of L1/L2 frequency positioning of GPS, but the positioning precision of the BDS2 is worse than that of GPS over most of the service region of the BDS2. Further, the positioning precision of BDS3 is better than that of GPS in the Asia-Pacific region, while it is the opposite in other regions. Based on these conclusions, we put forth some optimization recommendations regarding the signal frequency of the navigation system and GPS measurement standards to serve as references for optimizing the system performance and formulating standards. | Letao ZHOU Dingfa HUANG Wei FENG Wu CHEN Xi ZHANG Li YAN | 2019 | Science China Earth Sciences2019，62，4： | 0 |
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