Results 31 to 40 of about 2,995,639 (168)

Test of Determining Geopotential Difference between Two Sites at Wuhan Based on Optical Clocks’ Frequency Comparisons

Remote Sensing, 2022
Applications of optical clocks in physical geodesy for determining geopotential are of increasing interest to scientists as the accuracy of optical clocks improves and the clock size becomes more and more compact.
Anh The Hoang, Ziyu Shen, Kuangchao Wu, An Ning, Wenbin Shen   +4 more
doaj   +1 more source

Time‐frequency BSS of biosignals [PDF]

Healthcare Technology Letters, 2018
Time–frequency (TF) representations are very important tools to understand and explain circumstances, where the frequency content of non‐stationary signals varies in time. A variety of biosignals such as speech, electrocardiogram (ECG), electroencephalogram (EEG), and electromyogram (EMG) show some form of non‐stationarity.
openaire   +3 more sources

Recent Advances Concerning the ⁸⁷Sr Optical Lattice Clock at the National Time Service Center

Applied Sciences, 2018
We review recent experimental progress concerning the 87Sr optical lattice clock at the National Time Service Center in China. Hertz-level spectroscopy of the 87Sr clock transition for the optical lattice clock was performed, and closed-loop operation of
Yebing Wang, Xiaotong Lu, Benquan Lu, Dehuan Kong, Hong Chang   +4 more
doaj   +1 more source

Design of a vacuum system for space active hydrogen maser

Frontiers in Physics, 2022
With the high precision and stability of its frequency signal outputs, active hydrogen maser plays an important role in such fields as timing, satellite navigation, and communication. However, it needs to be lighter so as to be applied in space.
Haohui Que, Haohui Que, Wujiabei Xu, Wujiabei Xu, Qi Li, Qi Li, Jie Xiang, Tao Lu, Tiexin Liu, Yong Cai, Jiayu Dai, Xueling Hou   +11 more
doaj   +1 more source

Analysis of Narrow-Line Laser Cooling and Trapping of Sr Atoms in Microgravity Environments

Applied Sciences, 2020
Obtaining ultracold alkaline earth(-like) atoms in space encounters the problem of performing narrow-line laser cooling in microgravity environments ( μ -gEs).
Jie Ren, Hui Liu, Xiaotong Lu, Hong Chang   +3 more
doaj   +1 more source

Redefinition of the SI Base Units: Its Background and Principle [PDF]

한국정밀공학회지, 2018
The International System of Units (acronym: SI) is founded on seven base units (meter, kilogram, second, ampere, kelvin, mole, and candela) corresponding to seven base quantities (length, mass, time, electric current, thermodynamic temperature, amount of
Ho Seong Lee
doaj   +1 more source

The weak frequency anomaly detection method of atomic clocks based on Kalman filter and extrapolation-accumulation

Measurement + Control, 2021
A new method based on the innovation of Kalman filter and extrapolation-accumulation is proposed to detect weak frequency anomalies in atomic clocks with short detection time and high detection probability. In this method, the detection statistics of the
Ran Yan, Junliang Liu, Jianfeng Wu, Chao Xu, Yonghui Hu   +4 more
doaj   +1 more source

Wideband Time Frequency Coding

2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications, 2020
In the wideband regime, the performance of many of the popular modulation schemes such as code division multiple access and orthogonal frequency division multiplexing falls quickly without channel state information. Obtaining the amount of channel information required for these techniques to work is costly and difficult, which suggests the need for ...
Kathleen Yang, Salman Salamatian, Rafael G. L. D'Oliveira, Muriel Médard   +3 more
openaire   +2 more sources

The research of 369.5 nm laser stabilizing method and its influence on ytterbium ion optical clock

AIP Advances
The 369.5 nm laser serves as the cooling laser for ytterbium-ion optical clocks, and its frequency instability directly affects the intensity of ion fluorescence. This paper compares two stabilization methods for a 369.5 nm frequency-tripled fiber laser:
Shaoyang Dai, Chaowei Wang, Shiying Cao, Yani Zuo, Kun Liu, Weiliang Chen, Fasong Zheng, Wenbo Zhao, Fang Fang   +8 more
doaj   +1 more source

Photonic bandgap microcombs at 1064 nm

APL Photonics
Microresonator frequency combs and their design versatility have revolutionized research areas from data communication to exoplanet searches. While microcombs in the 1550 nm band are well documented, there is interest in using microcombs in other bands ...
Grisha Spektor, Jizhao Zang, Atasi Dan, Travis C. Briles, Grant M. Brodnik, Haixin Liu, Jennifer A. Black, David R. Carlson, Scott B. Papp   +8 more
doaj   +1 more source