中国科学院机构知识库网格系统: 检索

High-Precision Fiber Noise Detection and Comparison over a 260 km Field Fiber Link 期刊论文 OAI收割
SENSORS, 2024, 卷号: 24, 期号: 11, 页码: 9
作者: Zang, Qi; Zhang, Xiang; Wang, Dan; Zhou, Qian; Fan, Le

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收藏 | 浏览/下载：9/0 | 提交时间：2025/04/03

frequency comparison fiber noise sensing optical frequency transfer field fiber link

High-Resolution Multi-Channel Frequency Standard Comparator Using Digital Frequency Measurement 期刊论文 OAI收割
SENSORS, 2021, 卷号: 21, 期号: 16, 页码: 13
作者: Xiao, Bo; Liu, Ya; Li, Xiaohui; Deng, Zhifeng; Xue, Yanrong

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收藏 | 浏览/下载：33/0 | 提交时间：2021/11/29

multichannel frequency standard comparison digital frequency measurement

Influence of Precise Products on the Day-Boundary Discontinuities in GNSS Carrier Phase Time Transfer 期刊论文 OAI收割
SENSORS, 2021, 卷号: 21, 期号: 4, 页码: 23
作者: Zhang, Xiangbo; Guo, Ji; Hu, Yonghui; Sun, Baoqi; Wu, Jianfeng

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收藏 | 浏览/下载：19/0 | 提交时间：2021/11/29

GNSS precise point positioning time comparison station clock estimates day-boundary discontinuity precise products frequency stability

Demonstration of the frequency-drift-induced self-comparison measurement error in optical lattice clocks 期刊论文 OAI收割
JAPANESE JOURNAL OF APPLIED PHYSICS, 2020, 卷号: 59, 期号: 7, 页码: 4
作者: Lu, Xiaotong; Yin, Mojuan; Li, Ting; Wang, Yebing; Chang, Hong

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收藏 | 浏览/下载：24/0 | 提交时间：2020/09/01

optical lattice clock atomic clock self-comparison frequency drift optical lattice

Study on time registration method for photoelectric theodolite data fusion (EI CONFERENCE) 会议论文 OAI收割
10th World Congress on Intelligent Control and Automation, WCICA 2012, July 6, 2012 - July 8, 2012, Beijing, China
Yang H.-T.; Gao H.-B.

收藏 | 浏览/下载：18/0 | 提交时间：2013/03/25

In range measurement theodolite and radar constitute a real-time tracking system at different sites to track the same target in the air and get useful information exactly and timely. As the optical theodolite and radar have different sampling frequency and measurement system the data is sent to the fusion center is asynchronous. This paper proposed a time registration method based on multi-sensor data using Wavelet neural network algorithm which not only better solved the basic problems of theodolite fusion tracking but also improve the efficiency of data fusion. Simulation experiment and comparison with other time registration method have shown the advantage of this method. 2012 IEEE.

Space camera dynamic image quality measurement and evaluation (EI CONFERENCE) 会议论文 OAI收割
3rd International Conference on Measuring Technology and Mechatronics Automation, ICMTMA 2011, January 6, 2011 - January 7, 2011, Shanghai, China
作者: Zhang X.; Zhang X.; Zhang X.

收藏 | 浏览/下载：21/0 | 提交时间：2013/03/25

By using analysis of the infinity image of the space camera we intend to obtain the curve of the dynamic modulation transfer function. We extract the pixel gray values at the image edge which distribute as a knife-edge function and make differential calculation and Fourier transformation of it and then we can obtain the dynamic MTF curve of the optical system. The value of the curve at the Nyquist frequency is the most important parameter that reflects the image quality. We add push-scanning imaging and environmental effects to the static MTF of space camera and compare the MTF value with the dynamic MTF at Nyquist frequency. The comparison result can help us verify the accuracy of the calculating results and the feasibility of our method. (2011) Trans Tech Publications.

The Research of real time auto-recognition of the moire fringe (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Advances in Imaging Detectors and Applications, May 24, 2011 - May 26, 2011, Beijing, China
Wang M.-J.; Wu Z.-G.

收藏 | 浏览/下载：19/0 | 提交时间：2013/03/25

Measuring the movement of raster by the method of moire fringe has the advantage of high sensitivity high resolution and non-contacted measurement. The characteristic of moire fringe is that the image is white alternate with black the angle of the stripes is uniform the width of the stripes is uniform the terminators of the stripes aren't clear. A fast method that can figure out the width and angle of the moire fringe precisely is put forward in this paper. It calculates the angle the stripes firstly. According to the principle of the minimum mean squared error (MMSE) the closer a series of data is the smaller the value of the MMSE will be. The method is described as follows: It takes the image's center as the origin 180 beelines pass through the origin with the same angle interval. it calculates the value of the minimum mean squared error of the 180 beelines and find out the least one among those then the angle of the moire fringe comes out primarily. In order to improving the calculating precision of moire fringe 60 equal angles are divided in the neighborhood of the angle then a precise angle of moire fringe is calculated according to the principle of the MMSE. After getting out the angle of the moire fringe we begin to calculate the width of moire fringe. A line vertical with the moire fringe is drawn and we can get the width of the moire fringe by the vertical line. In order to get over the influence of the noise an effective area with the shape of diamond is selected in the image. The data of area is accumulated and projected according to the direction of moire fringe and a sine curve come out. The width of moire fringe can be obtained by getting the position of the first wave crest the position of the last wave crest and the number of wave crest. Experiments prove that the precision of the method put forward in this paper is enhanced in comparison with the traditional frequency method the precision of width calculation achieves to 99.6% according to the evaluation indicators of width detection error. The computing speed is boosted largely compared with traditional method and it can achieve with 15 ms that satisfying the demand of real time. 2011 SPIE.

DIFFERENCES AMONG DIFFERENT DATABASES IN THE NUMBER OF TROPICAL CYCLONES FORMING OVER THE WESTERN NORTH PACIFIC 期刊论文 OAI收割
JOURNAL OF TROPICAL METEOROLOGY, 2010, 卷号: 16, 期号: 4, 页码: 341-347
Wu, SA; Kong, HJ; Wu, H

收藏 | 浏览/下载：16/0 | 提交时间：2011/07/03

statistical characters difference comparison tropical cyclone frequency non-homogeneity

The analysis and design of low velocity estimation based on observer (EI CONFERENCE) 会议论文 OAI收割
2009 IEEE International Conference on Automation and Logistics, ICAL 2009, August 5, 2009 - August 7, 2009, Shenyang, China
作者: Wang D.; Zhang S.

收藏 | 浏览/下载：34/0 | 提交时间：2013/03/25

Low velocity servo system needs precision velocity estimation. An observer for low velocity estimation was proposed in this paper. First the source of low velocity estimation errors and the shortcomings of the single period difference were analyzed. The relationship between the estimation accuracy and estimator's frequency characteristics was concluded. Then the structure of the observer was proposed. Frequency characteristics were used to design the compensator which can stabilize the observer. The stability of the observer was also discussed. At last the observer's estimation accuracy was evaluated through a quantitative comparison. The results of simulation and experiment have shown that the quantized error in velocity estimation decreases dramatically when a velocity observer is used. Compared with some commonly-used estimators the phase lag accompanying the observer is much less. 2009 IEEE.

Compression of remote sensing image based on Listless Zerotree Coding and DPCM (EI CONFERENCE) 会议论文 OAI收割
ICO20: Remote Sensing and Infrared Devices and Systems, August 21, 2005 - August 26, 2005, Changchun, China
Chen S.-L.; Huang L.-Q.

收藏 | 浏览/下载：32/0 | 提交时间：2013/03/25

The data quantity of remote sensing image is very large. Furthermore the lowest frequency subband contains the main energy of original image and reflects the coarse of original image after remote sensing image is transformed by wavelet so it is very important to the reconstructed image. Therefore a hybrid image compression method based on Listless Zerotree Coding (LZC) and DPCM is presented namely the lowest frequency subband is compressed by DPCM and others are compressed by LZC. LZC is a kind of zerotree coding algorithm for hardware implementation which is based on SPIHT and substitutes two significant bit maps for three lists in SPIHT algorithm. Thereby LZC significantly reduces the memory requirement and complexity during encoding and decoding procedure. But LZC doesn't recognize the significance of grandchild sets so the PSNR values of LZC are lower than SPIHT's and the compression speed drops. It is improved by adding a significant bit map that recognizes the significance of grandchild sets. A comparison reveals that the PSNR results of the hybrid compression method are 2 dB higher than those of LZC and the compression speed is also improved.