The development of remote time frequency distribute system based on BD satellite common-view

2015 ◽  
Author(s):  
Chen Ruiqiong ◽  
Liu Ya ◽  
Xiaohui Li
Keyword(s):  
Common View ◽  
Time Frequency ◽  
Distribute System

An experiment of determining the geopotential difference using two hydrogen atomic clocks

2020 ◽  
Author(s):  
Kuangchao Wu ◽  
Wen-Bin Shen ◽  
Ziyu Shen ◽  
Chenghui Cai ◽  
Xiao Sun ◽  
...  
Keyword(s):  
Geographic Distance ◽  
Relativity Theory ◽  
Atomic Clocks ◽  
Common View ◽  
Time Frequency ◽  
The Common ◽  
Zero Baseline ◽  
Clock Comparison ◽  
The Stability ◽  
Geopotential Determination

<p>According to general relativity theory, one may determine the geopotential difference between two arbitrary stations by comparing there-located clocks’ running rates. In this study, we provide experimental results of the geopotential determination based on the time elapse comparison between two hydrogen atomic clocks, one fixed clock  and one portable clock , using the common view satellite time transfer (CVSTT) technique. We compared the portable clock  located at Jiugongshan Time Frequency Station (JTFS) with the fixed clock  located at Luojiashan Time Frequency Station (LTFS) for 30 days. The two stations are separated by a geographic distance of around 240 km with height difference around 1230 m. Then the clock  was transported (without stopping its running status) to LTFS and compared with clock  for zero-baseline calibration for 15 days. The clock-comparison-determined geopotential difference between JTFS and LTFS is determined. Results show that the clock-comparison-determined result deviates from the EGM20080-determined result by about 2322±1609 m<sup>2</sup>s<sup>-2</sup>, equivalent to 237±164  m in height, in consistence with the stability of the hydrogen atomic clocks applied in the experiments (at the level of 10<sup>-15</sup>/day).</p><p>This study is supported by NSFCs (grant Nos. 41721003, 41631072, 41874023, 41804012, 41429401, 41574007) and Natural Science Foundation of Hubei Province of China (grant No. 2019CFB611).</p>

scholarly journals Comparison of VLBI and GNSS common view for time transfer

2019 ◽  
Vol 10 ◽  
pp. 15 ◽  
Author(s):  
Pingli Wang ◽  
Guangli Wang ◽  
Yuping Gao ◽  
Hongbing Cai ◽  
Na Liu
Keyword(s):  
High Precision ◽  
Rapid Development ◽  
Next Generation ◽  
Time Transfer ◽  
Position Measurement ◽  
Common View ◽  
Practical Applications ◽  
Time Frequency ◽  
Frequency Standards ◽  
Frequency Transfer

With the rapid development of optical clock, the stability and system uncertainty of optical clocks has reached a 1.0e–18 level. Optical clocks will likely constitute the next generation of time-frequency standards for redefining the SI second. Because time and frequency transfer services that rely on satellite systems are not always reliable and currently available technologies are insufficient for comparing the next generation of frequency standards, high-precision time and transfer techniques are strongly desired. Very Long Baseline Interferometry (VLBI) is one of the space geodetic techniques that measure the arrival time delays between multiple stations utilizing radio signals from distant celestial radio sources. Not only can VLBI obtain the angle position measurement of the radio source with sub-millisecond accuracy and the station coordinate measurement with millimeter accuracy, but also, it can provide high-precision information regarding inter-station atomic clock differences. Therefore, it is theoretically feasible to use the VLBI technology to do the remote time transfer. Because of this characteristic of VLBI technology, VLBI has significant application potential in the field of remote time transfer. To confirm the suitability of VLBI to time-frequency transfer for future practical applications, the results of VLBI and GPS common view time transfer were compared using a Kunming-Urumqi baseline. The performance characteristics of time transfer based on VLBI are then analyzed. Experimental results show that VLBI technology can accurately measure the variation of clock differences between stations as same as the GPS common view time comparison technology. It briefly describes the challenges of future VLBI technology for practical applications of time transfer.

GNSS Carrier Phase Integer Single Difference Times and Frequency Transfer Accuracy Evaluation

2021 ◽  
Author(s):  
Wei Xu ◽  
Wen-Bin Shen ◽  
Cheng-hui Cai ◽  
An Ning ◽  
Zi-yu Shen
Keyword(s):  
Natural Science ◽  
Carrier Phase ◽  
Gravity Potential ◽  
Double Difference ◽  
Transfer Model ◽  
Common View ◽  
Time Frequency ◽  
Single Difference ◽  
Frequency Transfer ◽  
Transfer Accuracy

<p>Due to the influence of pseudo-range noise, traditional GNSS common view method is difficult to improve the accuracy of time-frequency transfer. GNSS carrier phase precise point positioning (PPP) time-frequency transfer has become a research hotspot because of its high accuracy. In this paper, a time-frequency transfer model of GNSS carrier phase single difference (SD) and Integer Single Difference (ISD) between any two ground stations is studied. In order to solve the problem that the SD ambiguity cannot be fixed due to the influence of the phase biases at the receivers, a method of SD ambiguity fixing is proposed, that is the SD ambiguity is fixed with the constraint of the fixed double difference ambiguity among several stations and satellites. Here taking four time-frequency links between pairs of ground stations, BRUX-OPMT (262.3km), BRUX-PTBB (454.6km), BRUX-WTZR (637.7km) and BRUX-CEBR (1331.6km) as examples, the multi-GNSS time-frequency transfer experiment of SD, ISD and PPP method is carried out. The results show that the SD and PPP time-frequency transfer accuracy is equivalent, the stability of ISD is improved compared with SD, and the difference RMS between epochs is less than 10 ps. High precision carrier phase SD, ISD and PPP technology can be applied to the study of determining the gravity potential based on time-frequency measurements. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.</p>

Differential Timing Method Based on Modified Traceability Model

2020 ◽  
Vol 73 (6) ◽  
pp. 1326-1339
Author(s):  
Ying Liu ◽  
Wenhai Jiao ◽  
Longxia Xu ◽  
Xiaohui Li
Keyword(s):  
Low Cost ◽  
Base Stations ◽  
Model Parameters ◽  
Common View ◽  
Time Frequency ◽  
Geostationary Satellites ◽  
Cost Differential ◽  
5G Network ◽  
The One ◽  
Differential Timing

The common view time transfer and two-way time and frequency transfer methods are currently the main means for achieving time synchronisation at nanosecond level. However, these methods have some limitations in real time and cost, which limit their wide applications in many fields, such as time synchronisation among base stations of the upcoming 5G network. In order to meet the requirements of nanosecond time synchronisation, a low-cost differential timing method is proposed in this paper by changing the manner of generation of traceability model parameters in GNSS navigation messages. The time deviation between GNSS system time and the timing laboratory that maintains Coordinated Universal Time (UTC) kept by timing laboratory named k (UTC(k)) is monitored by receiving the GNSS signal in space with monitoring receivers. The new traceability model parameters are generated with the monitored time deviations and then broadcast to users through the GNSS navigation message. The precision of the one-way timing method can be improved from tens of nanoseconds to the order of several nanoseconds with the proposed method. In addition, there are obvious advantages to carry out this method on the geostationary satellites in the BeiDou navigation satellite (BDS) constellation. The proposed method is verified on an experimental platform based on the UTC(NTSC) time frequency signal and the geostationary satellites in the BDS-3 constellation.

Articulatory Generalization in Two Word-Medial, Ambisyllabic Contexts

1988 ◽  
Vol 19 (3) ◽  
pp. 251-258 ◽  
Author(s):  
Virginia I. Wolfe ◽  
Suzanne D. Blocker ◽  
Norma J. Prater
Keyword(s):  
Common View ◽  
Perceptual Salience ◽  
The Common ◽  
Unitary Concept ◽  
Over Time

Articulatory generalization of velar cognates /k/, /g/ in two phonologically disordered children was studied over time as a function of sequential word-morpheme position training. Although patterns of contextual acquisition differed, correct responses to the word-medial, inflected context (e.g., "picking," "hugging") occurred earlier and exceeded those to the word-medial, noninflected context (e.g., "bacon," "wagon"). This finding indicates that the common view of the word-medial position as a unitary concept is an oversimplification. Possible explanations for superior generalization to the word-medial, inflected position are discussed in terms of coarticulation, perceptual salience, and the representational integrity of the word.

A Fault Detection Approach Based on Sound Signal Analysis for Equipment Monitoring

2020 ◽  
pp. 129-139
Author(s):  
Weihai Sun ◽  
Lemei Han
Keyword(s):  
Fault Detection ◽  
Signal Analysis ◽  
Energy Analysis ◽  
Detection Method ◽  
Sound Signal ◽  
Practical Significance ◽  
Time Frequency ◽  
Detection Approach ◽  
Machine Fault ◽  
Learning Data

Machine fault detection has great practical significance. Compared with the detection method that requires external sensors, the detection of machine fault by sound signal does not need to destroy its structure. The current popular audio-based fault detection often needs a lot of learning data and complex learning process, and needs the support of known fault database. The fault detection method based on audio proposed in this paper only needs to ensure that the machine works normally in the first second. Through the correlation coefficient calculation, energy analysis, EMD and other methods to carry out time-frequency analysis of the subsequent collected sound signals, we can detect whether the machine has fault.

Time-Frequency Analysis of Partial Discharge Phenomena in SF6 gas using Wavelet Transform

1997 ◽  
Vol 117 (3) ◽  
pp. 338-345 ◽  
Author(s):  
Masatake Kawada ◽  
Masakazu Wada ◽  
Zen-Ichiro Kawasaki ◽  
Kenji Matsu-ura ◽  
Makoto Kawasaki
Keyword(s):  
Wavelet Transform ◽  
Frequency Analysis ◽  
Partial Discharge ◽  
Time Frequency Analysis ◽  
Time Frequency

DARI PERSIA HINGGA CINA: Diskursus tentang Teori Kedatangan Islam di Melayu Nusantara

2018 ◽  
pp. 1-16
Author(s):  
Lukmanul Hakim
Keyword(s):  
The Other ◽  
Strong Tendency ◽  
Common View ◽  
Historical Method ◽  
Malay Archipelago

The arrival of Islam in Malay Archipelago to this day is still a debate, because no data and facts have been found to be scientifically justified, but also because of the unilateral nature of the various theories. There is a strong tendency, certain theories emphasize only the specific aspects, while ignoring the other aspects. Therefore, most of the theories that exist in certain aspects fail to explain the coming of Islam, and the process of Islamization. This paper aims to analyze the theory of the arrival of Islam in the Malay Archipelago world. The method used is historical method. Until now there are at least four theories that discuss the theory of the arrival of Islam in the Malay Archipelago world. The four theories are Gujarat theory, Mecca theory, Persian theory and fourth theory (Chinese). Each of these theories has the strengths and weaknesses and certainly these four theories have a common view of Islam as a religion developed in the archipelago through a peaceful way and Islam does not recognize mission as practiced by Christians and Catholics.

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