Subjects: Astronomy submitted time 2024-04-12 Cooperative journals: 《天文学报》
Abstract： With the rapid development of astronomical detection technology, there will be a huge torrent of incoming galaxy images in the coming years, making the automatic galaxy morphology classification a challenging task. To solve the problem of feature selection, the low speed and low accuracy of traditional galaxy morphology classification models, a galaxy morphology classification model based on Inception-v3 neural network with SE (Squeeze and Excitation Network) channel attention mechanism is introduced. We select galaxy images from Sloan Digital Sky Survey (SDSS) for the SE-Inception-v3 model. The test results show that the accuracy of SE-Inception-v3 model is as high as 99.37\%, and the F1 scores of spiral galaxy, completely round smooth galaxy, in-between smooth galaxy, cigar-shaped smooth galaxy and edge-on galaxy are 99.33\%, 99.58\%, 99.33\%, 99.41\% and 99.16\%, respectively. Compared with the MobileNet (Mobile Neural Network) and ResNet (Residual Neural Network) models, the width and depth advantages of SE-Inception-v3 make the classification model have stronger feature extraction capabilities, which provides a new galaxy morphology classification approach for future large-scale sky survey programs.
Subjects: Astronomy submitted time 2024-04-12 Cooperative journals: 《天文学报》
KANG Zhe
NIU Bing-li
LI Zhen-wei
SUN Jian-nan
LV You
ZHU Cheng-wei
DENG Shi-yu
LIU De-long
YANG Wen-bo
ZHANG Nan
LIU Ming
SUN Ming-guo
LIU Cheng-zhi
Abstract： Ground-based optical astronomical telescopes are one of the most important instruments for human exploration and research of the universe. Monitoring and analysis of the optical observation environment of the existing ground-based optical station can provide a reference for the targeted modification of equipment and the adjustment of observation strategies of observers, which is of great significance for improving the observation efficiency of ground-based optical equipment. Jilin Astronomical Observatory (hereinafter referred to as the ``Base'') is located about 5 kilometers (126.3$^{\circ}$ E, 43.8$^{\circ}$ N, 313 meters above sea level) in Nangou, Xiaosuihe Village, Dasuihe Town, Jilin City, Jilin Province, which is affiliated to the Changchun Observatory, National Astronomical Observatories, Chinese Academy of Sciences. The mean value of seeing of the base is about 1.3$''$--1.4$''$, the night sky brightness in the V band near the zenith is 20.64\;mag\,$\cdot$\,arcsec$^{-2}$, and the maximum number of clear nights is better than 270 days per year, which shows the good astronomical observation conditions. Jilin Astronomical Observatory, which was put into operation in 2016, has several photoelectric telescopes, including the 1.2-meter photoelectric telescope, the Mini Optoelectronic Telescope Array, the large field of view photoelectric telescope array, and the advanced multi-functional array-structured photoelectric detector. With the equipments mentioned above, we have carried out relevant research mainly on space target detection and recognition, precision orbit determination, new photoelectric detection methods and multicolor photometry of variables, and so forth. We have maintained a good cooperative relationship with a number of domestic universities and scientific research institutes.
Subjects: Astronomy submitted time 2024-01-31 Cooperative journals: 《天文学报》
Abstract： A comprehensive time scale calculation method for hydrogen maser and cesium atomic clock based on the improved exponential filtering and Vondrak\_Cepek joint smoothing method is proposed. It is based on the minimum error method, which dynamically estimates the frequency drift parameters of the hydrogen maser and improves the accuracy of predicting the clock bias of the hydrogen atomic clock; With the method of improved quadratic exponential smoothing, the hydrogen masers time scale is generated, and the weighted average method is used to generate the cesium atomic clocks' time scale. At the same time, the Vondrak\_Cepek filter is designed to combine the long-term and short-term stability advantages of the two types of time scales to improve the comprehensive time scale performance. Experimental results show that the proposed method produces hydrogen cesium with a comprehensive time scale stability of up to $1.60 \times 10^{-15}$ h$^{-1}$, stable up to 3 $\times 10^{-15}$ d$^{-1}$, outperforming the time-scale performance generated by three classic methods: ALGOS, AT1, and Kalman filtering.
Subjects: Astronomy submitted time 2024-01-31 Cooperative journals: 《天文学报》
Abstract： BeiDou navigation satellite system (BDS) has been officially built and opened in July 2020. BDS-3 adds new signals B1C and B2a on the basis of old signals B1I and B3I. In order to comprehensively evaluate the positioning performance of new signals B1C and B2a of BDS-3, the positioning performance of GPS (Global Positioning System), BDS-3, BDS-2/BDS-3 old and new signals and the positioning performance of BDS combined with GPS at different frequency points are tested. The positioning performance of BDS (B1I+B3I, B1C/B2a) + GPS (L1+L2) combined static PPP (Precise Point Positioning) is analyzed and compared with that of single satellite system. The experimental results show the positioning accuracy of BDS-3 (B1C/B2a) in E (East), N (North), U (Up) direction is better than 1.25\;cm, 0.89\;cm, 1.67\;cm, respectively. The positioning accuracy of BDS-3 new and old frequency points in E and N directions is the same as that of GPS L1/L2, and the positioning accuracy of new frequency points in U direction is higher than that of GPS L1/L2 and BDS-3 old frequency points, which is 34.2\% higher than that of old frequency points. The convergence time of the new frequency point is 25.9\;min, which is 12.7\% higher than that of the old frequency point. Compared with BDS and GPS single systems, BDS/GPS positioning accuracy and convergence time of the combined system have been significantly improved. BDS-3 (B1C/B2a)+GPS has the same positioning accuracy as BDS-3 (B1I/B3I)+GPS in E and N directions. In the U direction, the positioning accuracy of the former is significantly improved compared with the latter, which is increased by 17.2\%. The convergence time of the new frequency point of the combined system is 20.1\;min, which is 17.6\% higher than that of the old frequency point.
Subjects: Biology >> Ecology submitted time 2017-11-29 Cooperative journals: 《中国生态农业学报》
Abstract： Cultivated lands are among the most fundamental resources for national food security and sustainable social development. Scientific analysis of the spatial distribution patterns and evolutionary characteristics of cultivated land quality is significant for the protection and layout optimization of cultivated lands. Analysis of the spatial distribution of cultivated land quality at different scales is the basis of cultivated land quality improvement and strengthening cultivated land protection. This paper was based on cultivated land quality monitoring experimental unit in Lichuan County in Jiangxi Province and then used weighted average; variation coefficient; and spatial autocorrelation to analyze spatial disparity characteristics of cultivated land quality. Multi-scale spatial autocorrelation analysis of cultivated land quality research is a hot research area. The innovation in this paper was the introduction of natural land grade index; use of the grade index and economic grade index as the space variable to separately explore and discuss the degree of spatial correlation and spatial disparity of cultivated land quality at county-scale; township-scale and village-scale in GIS environment. The results of the research showed that: 1) Cultivated land quality index was high in the south and north and low in the west and east in Lichuan County. When the threshold distance was 400 m; there was a significant spatial autocorrelation in cultivated land quality. The Moran’s I value of natural land grade index was highest; followed by economical land grade index; and land use grade index was the lowest. The Moran’s I value of cultivated land quality from county to township and then to village scales decreased systematically. Multi-scale spatial autocorrelation analysis of cultivated land quality exhibited a significant aggregation of global spatial distribution in Lichuan County. 2) It was found that different types of cultivated land quality indexes had remarkably different spatial correlations at different spatial scales. For the influence degree of spatial scale; land use grade index was greatly affected by spatial scale; followed by natural land index; and the economic land grade index was the weakest. For the coefficient of variation of cultivated land quality index; fluctuation in Moran’s I value for cultivated land at village-scale was far greater than that at township scale. While at the same spatial scale; the coefficient of variation of natural land index was strongest; followed by economic land index and then land use index. 3) The results based on local indicators of spatial association (LISA) showed that positive spatial autocorrelation of cultivated land quality; included the high-high type and the low-low type; emerged as the shape of the cluster and in the form of group; while the negative spatial autocorrelation contained the high-low type and low-high type was fragmented in space. The results of the study showed that spatial disparity in cultivated land quality was sensitive to spatial scale. Therefore; for cultivated land quality improvement and protection; there was the need to pay more attention to spatial disparity of cultivated land quality at town scale and village scale. Also based on the difference in spatial correlation degree among the natural conditions; utilization conditions and economic benefits; it was possible to explore cultivated land quality improvement and protection measures that met actual ground situations in the study area. The results of the study provided the needed references for the construction of high-standard basic farmlands; land reclamation; regional cultivated land quality monitoring; cultivated land protection; partitioning and management of cultivated lands; cultivated land quality improvement and spatial optimization of cultivated land quality.
Subjects: Physics >> Nuclear Physics submitted time 2016-09-14
Abstract： The diquark-triquark model is used to explain charmonium-pentaquark states, i.e., Pc(4380) and Pc(4450), which were observed recently by the LHCb collaboration. For the first time, we investigate the properties of the color attractive configuration of a triquark and we define a nonlocal light cone distribution amplitude for pentaquark states, where both diquark and triquark are not pointlike, but they have nonzero size. We establish an effective diquark-triquark Hamiltonian based on spin-orbital interaction. According to the Hamiltonian, we show that the minimum mass splitting between 52+ and 32− is around 100~MeV, which may naturally solve the challenging problem of small mass splitting between Pc(4450) and Pc(4380). This helps to understand the peculiarities of Pc(4380) with a broad decay width whereas Pc(4450) has a narrow decay width. Based on the diquark-triquark model, we predict more pentaquark states, which will hopefully be measured in future experiments.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2016-09-13
Abstract： If dark matter (DM) is composed by particles which are non-gravitationally coupled to ordinary matter, their annihilations or decays in cosmic structures can result in detectable radiation. We show that the most powerful technique to detect a particle DM signal outside the Local Group is to study the angular cross-correlation of non-gravitational signals with low-redshift gravitational probes. This method allows to enhance signal-to-noise from the regions of the Universe where the DM-induced emission is preferentially generated. We demonstrate the power of this approach by focusing on GeV-TeV DM and on the recent cross-correlation analysis between the 2MASS galaxy catalogue and the Fermi-LAT gamma-ray maps. We show that this technique is more sensitive than other extragalactic gamma-ray probes, such as the energy spectrum and angular autocorrelation of the extragalactic background, and emission from clusters of galaxies. Intriguingly, we find that the measured cross-correlation can be well fitted by a DM component, with thermal annihilation cross section and mass between 10 and 100 GeV, depending on the small-scale DM properties and gamma-ray production mechanism. This solicits further data collection and dedicated analyses.
Peer Review Status:Awaiting Review
Hits
YES
Hits
Downloads
Comment