Considered to be extensions of the Hipparcos reference system, PPMX and UCAC3 are two of the most important astrometric catalogs released in current years. Extensive analyses of these two large catalogs have been made...Considered to be extensions of the Hipparcos reference system, PPMX and UCAC3 are two of the most important astrometric catalogs released in current years. Extensive analyses of these two large catalogs have been made in order to determine the local and overall systematic biases. The regional and magnitude dependent differences in stellar position and proper motion are comparable to random errors and are even larger in the northern hemisphere. The global orientation bias vector ε between the two systems is also significant （up to 17 mas）, which shows the overall differences of the PPMX and UCAC3 catalogs and their reference systems. On the other hand, the term for the global rotation vector a; is small （tenths of mas per year）： it is reasonable to believe that the PPMX and UCAC3 reference frames do not rotate with respect to each other. Because of plate dependent and field-to-field errors in the UCAC3 catalog, we suggest that positions and proper motions of UCAC3 stars in the northern hemisphere （δ 〉 -20°） should be used with caution.展开更多
Quasars can be used to measure baryon acoustic oscillations at high redshift, which are considered as direct tracers of the most distant large-scale structures in the universe. It is fundamental to select quasars from...Quasars can be used to measure baryon acoustic oscillations at high redshift, which are considered as direct tracers of the most distant large-scale structures in the universe. It is fundamental to select quasars from observations before implementing the above research. This work focuses on creating a catalog of quasar candidates based on photometric data to provide primary priors for further object classification with spectroscopic data in the future, such as the Dark Energy Spectroscopic Instrument(DESI) Survey. We adopt a machine learning algorithm(Random Forest, RF) for quasar identification. The training set includes 651,073 positives and 1,227,172 negatives, in which the photometric information are from DESI Legacy Imaging Surveys(DESI-LIS) and Wide-field Infrared Survey Explore(WISE), and the labels are from a database of spectroscopically confirmed quasars based on Sloan Digital Sky Survey and the Set of Identifications& Measurements and Bibliography for Astronomical Data. The trained RF model is applied to point-like sources in DESI-LIS Data Release 9. To quantify the classifier’s performance, we also inject a testing set into the to-be-applied data.Eventually, we obtained 1,953,932 Grade-A quasar candidates and 22,486,884 Grade-B quasar candidates out of425,540,269 sources(~5.7%). The catalog covers ~99% of quasars in the to-be-applied data by evaluating the completeness of the classification on the testing set. The statistical properties of the candidates agree with that given by the method of color-cut selection. Our catalog can intensely decrease the workload for confirming quasars with the upcoming DESI data by eliminating enormous non-quasars but remaining high completeness. All data in this paper are publicly available online.展开更多
Ancient China recorded a wealth of astronomical observations,notably distinguished by the inclusion of empirical measurements of stellar observations.However,determining the precise observational epochs for these data...Ancient China recorded a wealth of astronomical observations,notably distinguished by the inclusion of empirical measurements of stellar observations.However,determining the precise observational epochs for these datasets poses a formidable challenge.This study employs the generalized Hough transform methodology to analyze two distinct sets of observational data originating from the Song and Yuan dynasties,allowing accurate estimation of the epochs of these stellar observations.This research introduces a novel and systematic approach,offering a scholarly perspective for the analysis of additional datasets within the domain of ancient astronomical catalogs in future investigations.展开更多
The currently used Galactic coordinate system（GalC S） is based on the FK5 system at J2000.0, which was transformed from the FK4 system at B1950.0.The limitations and misunderstandings related to this transformed Gal...The currently used Galactic coordinate system（GalC S） is based on the FK5 system at J2000.0, which was transformed from the FK4 system at B1950.0.The limitations and misunderstandings related to this transformed GalC S can be avoided by defining a new GalC S that is directly connected to the International Celestial Reference System（ICRS）. With more data at various wavelengths released by large survey programs, a more appropriate GalC S consistent with features associated with the Milky Way can be established. We try to find the best orientation of the GalC S using data from two all-sky surveys, AKARI and WISE, at six wavelengths between 3.4 μm and 90 μm, and synthesize results obtained at various wavelengths to define an improved GalC S in the framework of the ICRS. The revised GalC S parameters for defining the new GalC S in the ICRS are summarized as：αp= 192.777°, δp= 26.9298°, for the equatorial coordinates of the north Galactic pole and θ = 122.95017° for the position angle of the Galactic center. As one of the Galactic substructures, the Galactic warp exhibits different forms in different GalC Ss that are constructed with various data and methods, which shows the importance of re-defining the GalC S by the relative commission of the International Astronomical Union that can lead to a better understanding of Galactic structure and kinematics.展开更多
Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Phi...Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Philippine Sea plates.The magnitudes for the same event from these two catalogs of Taiwan and Beijing are different due to diferent data sources selected and different magnitude scales used. To measure sizes of Taiwan events in uniform magnitude scale, the author adopted a catalog of earthquakes with uniform local magnitude scale (Shin, 1993)compiled by Cheng (1996) in compiling a new catalog of Chinese earthquakes. To measure sizes of Taiwan events,we adopted uniform local magnitude scale for events with 5≤M<6. For event with M≥6 we still adopted IASPEI surface wave magnitude scale. Thus the statistic difference between two magnitude values from Taiwan and Beijing in magnitude interval 5≤M<6 reflects difference between Taiwan uniform local magnitode scale and Beijing surface wave magnitude scale. The statistic difference in magnitude interval he6 reflects difference between IASPEI surface wave magnitude scale and Beijing surface wave magnitude scale. Three data sources from "Wang","Cheng" and "Chinese mainland" of Taiwan events with m≥7 are given in this paper, in order to obtain a complete catalog.The statistic result indicates that Taiwan magnitude is slightly larger than Beijing magnitude for 998 events with 5≤M<6. The mean difference is about 0.13 of magnitude unit with deviation 0.32. Similarly, the mean difference is about 0.09 of magnitude unit with deviation 0.23 for 298 eventS with m≥6. We also noted that the difference of magnitude values between Beijing and Taiwan surface wave magnitUdes changed in different time period.Before 1971, most Taiwan magnitude values of the events is larger than Beijing’s. In contrast, most Beijing magnitude values of the events are larger than Taiwan magnitUde values aller 1972. It is probably related to data sources. Three catalogs of events with m≥7 are given in this paper Wang’s catalog (1995) includes 44 events with M≥7, Cheng’s (1996) 39 events and Chinese catalog, before 1911 compiled by Min (1995), 1912-1990 compiled by Wang, et al (1997) and 1991-1998 compiled by Yang, includes 41 events. The variety of these data sources discussed in this paper can be a useful reference for seismologists who use catalog seismic data do their research.However the statistic results and empirical relations presented in this paper can not be used for converting between magnitude scales, since some of them are not the original observation values. In addition, three catalogs of events with M≥ 7 given in this paper can be used for seismicity research comprehensively.展开更多
West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete....West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete. In 1991, Bertil studied the seismicity of West Africa based on networks of seismic stations in Ivory Coast and neighboring countries. The reference work of Ambraseys and Adams as well as the recent earthquakes given by the international data centres on the seismicity of West Africa were also used for the computations of earthquake hazard parameters. Different earthquake event data have been compiled and homogenised to moment magnitude (</span><i><span style="font-family:Verdana;">M</span><sub><span style="font-family:Verdana;">w</span></sub></i><span style="font-family:Verdana;">). The obtained catalog covers a period of over four centuries (1615-2021) and contains large historical events and recent complete observations. The complete catalog part has been subdivided into four complete subcatalogs with each a level of completeness. The minimum magnitude and the maximum observed magnitude are equal to 2.89 and 6.8 respectively for the whole catalog. The seismic code software developed by Kijko was used to calculate the earthquake hazard parameters. The results give a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">b</span></i></span></span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">value of 0.83 ± 0.08 for the whole period and preliminary seismic hazards curves are also plotted for re</span><span style="font-family:Verdana;">turn periods 25, 50 and 100 years. This is a good and practical example</span><span style="font-family:Verdana;"> showing that this procedure can be used for seismic hazard assessment in West Africa.展开更多
The increasing availability of government data has prompted efforts to standardize data cataloging practices for enhanced accessibility and usability.The primary aim of this study is to descriptively assess data catal...The increasing availability of government data has prompted efforts to standardize data cataloging practices for enhanced accessibility and usability.The primary aim of this study is to descriptively assess data catalog and referenced dataset volume,metadata utilization,and thematic composition of United States DCAT compliant data catalogs across Federal,State,County,City,and Territory entities.Data collection involved compiling a list of relevant government agencies and data resources to identify data catalogs.DCAT compliance was then assessed,and metadata from compliant catalogs was extracted.Thematic mapping utilized Python packages RegEx and FuzzyWuzzy to categorize themes into eight standard categories.A combination of descriptive statistics and 1-way ANOVA tests were conducted to analyze dataset volume,metadata utilization,and reported themes.Of the 305 data catalogs identified,259 were found to be DCAT compliant.Federal entities exhibited the highest DCAT compliance rates(92.3%),followed by County(88.1%),City(86.9%),and State(77.0%),while Territory(0%)had no compliant data catalogs.Descriptive analysis revealed that federal DCAT compliant data catalogs(n=59)had the highest average number of data assets across their data catalogs(μ=1,133.2)with the predominant themes being transportation at 21.2%(n=14,785)and geospatial at 15.4%(n=10,761).While county data catalogs(n=52)had the lowest average(μ=232.6)with the most referenced themes being geospatial at 77.6%(n=8450)and finance at 2.4%(n=270).After applying thematic mapping to eight standard categories,the three most dominant themes across all entities were transportation at 38.1%(n=16,504),natural resources with 19.6%(n=8,501),and health and safety with 14.7%(n=6,367).These findings underscore the widespread adoption of the DCAT standard across government entities,with notable gaps at the territorial level.Federal and state entities exhibited the highest data catalog and dataset volumes,while metadata utilization remained relatively consistent across all entity levels.The thematic analysis highlights the importance of standardization efforts to enhance thematic consistency and facilitate effective data interpretation.Further collaboration and investment are warranted to address gaps in catalog coverage and establish standardized data cataloging practices to maximize the accessibility and usability of these data catalogs along with their referenced datasets.展开更多
We introduce an algorithm to solve the block-edge problem taking advantage of the two different sky splitting functions： HTM and HEALPix. We make the cross-match with the two functions, and then we obtain the union s...We introduce an algorithm to solve the block-edge problem taking advantage of the two different sky splitting functions： HTM and HEALPix. We make the cross-match with the two functions, and then we obtain the union set of the two different sets. We use the ThreadPool technique to speed up the cross-match. In this way improved accuracy can be obtained on the cross-match. Our experiments show that this algorithm has a remarkable performance superiority compared with the previous ones and can be applied to the cross-match between large-scale catalogs. We give some ideas about solving the many-for-one situation occurred in the cross-match.展开更多
This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE...This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE was conducted using publicly accessible data that concentrated on star formation rates(SFRs)and depletion timescales.By employing the fundamental equation,I determined the SFE in relation to its freefall time,which highlighted variations in efficiencies associated with SFR masses derived from different spectra.The results demonstrated that the highest efficiency value was observed in the analysis of the 1.4 GHz radio continuum,emphasizing the importance of studying star-forming clouds across a range of electromagnetic wavelengths to achieve a comprehensive understanding of star formation mechanisms.The study's findings indicated a peak efficiency of star formation value of approximately 0.9%,while the relative minimum obtained from(O II)was around 0.42%,aligning with the range of SFEs documented in the existing literature.Additionally,investigating the factors that influence the variability in efficiency when examining clouds in BCGs across different wave bands is crucial for deepening our comprehension of the underlying processes of star formation.展开更多
Natural earthquakes and micro-seismicity resulting from hydraulic fracturing or other engineering practices display distinctively different spatial-temporal features,like mixed burst-and swarm-like features or predomi...Natural earthquakes and micro-seismicity resulting from hydraulic fracturing or other engineering practices display distinctively different spatial-temporal features,like mixed burst-and swarm-like features or predominantly swarm-like features.The mechanism(s)contributing to such observations can be diverse.We present the inspections on the dynamic formation process of the single swarm-like tree in laboratory acoustic emission(AE)catalogs.Such largest swarm-like trees can contain>97%AE events from the entire catalog within a test;and all catalogs under investigation display scale-invariance features.The formation of the largest swarm-like tree correlates with the rock fracture process analogue of the source pervasive process,where its AE releases exhibit significant spatial well-organization.Comparison to other laboratory catalogs under different laboratory settings helps us identify the spatial continuity of the rock fracture process as the primary factor in forming the largest swarm-like trees at laboratory scale.The stress transfer process is involved in the rock fracture process for the tests having pre-existing spatial discontinuity.Artificial perturbations on the spatial information induced by the stress transfer process further confirm that stress transfer also serves to shift the pure swarm-like catalog into a mixed burst-and swarm-like catalog.These laboratory observations may provide inspirational insights for understanding the field-scale mechanism(s)shaping the spatial-temporal energy release features.展开更多
In the task of classifying massive celestial data,the accurate classification of galaxies,stars,and quasars usually relies on spectral labels.However,spectral data account for only a small fraction of all astronomical...In the task of classifying massive celestial data,the accurate classification of galaxies,stars,and quasars usually relies on spectral labels.However,spectral data account for only a small fraction of all astronomical observation data,and the target source classification information in vast photometric data has not been accurately measured.To address this,we propose a novel deep learning-based algorithm,YL8C4Net,for the automatic detection and classification of target sources in photometric images.This algorithm combines the YOLOv8 detection network with the Conv4Net classification network.Additionally,we propose a novel magnitude-based labeling method for target source annotation.In the performance evaluation,the YOLOv8 achieves impressive performance with average precision scores of 0.824 for AP@0.5 and 0.795 for AP@0.5:0.95.Meanwhile,the constructed Conv4Net attains an accuracy of 0.8895.Overall,YL8C4Net offers the advantages of fewer parameters,faster processing speed,and higher classification accuracy,making it particularly suitable for large-scale data processing tasks.Furthermore,we employed the YL8C4Net model to conduct target source detection and classification on photometric images from 20 sky regions in SDSS-DR17.As a result,a catalog containing about 9.39 million target source classification results has been preliminarily constructed,thereby providing valuable reference data for astronomical research.展开更多
The Stellar Abundances and Galactic Evolution Survey(SAGES)is a multi-band survey that covers the northern sky area of~12,000 deg2.The Nanshan One-meter Wide-field Telescope(NOWT)of the Xinjiang Astronomical Observato...The Stellar Abundances and Galactic Evolution Survey(SAGES)is a multi-band survey that covers the northern sky area of~12,000 deg2.The Nanshan One-meter Wide-field Telescope(NOWT)of the Xinjiang Astronomical Observatory carried out observations on g/r/i bands.Here,we present the survey strategy,data processing,catalog construction,and database schema.The observations of NOWT started in 2016 August and were completed in2018 January,a total of 17,827 frames were obtained and~4600 deg2 sky areas were covered.In this paper,we release the catalog of the data in the g/r/i bands observed by NOWT.In total,there are 109,197,578 items of source records.The catalog is the supplement for the SDSS for the bright end,and the combination of our catalog and these catalogs could be helpful for source selections for other surveys and Milky Way sciences,e.g.,white dwarf candidates and stellar flares.展开更多
We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent...We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent region in the rest-frame UVJ diagram. Comparing the five HSC bands and the subsample with HST F160W images, consistent with the decreasing effective radius re, Sérsic index n shows an increasing trend indicating a more bulge-dominant morphology towards the infrared. Even for our massive, quiescent galaxies,which are dominated by typical elliptical galaxies with bulges, the reand n values still vary with the wavelengths.For instance, there is a systematic drop in n of ~0.4 going from y band to F160W, making 20% of the HSC “disklike” galaxies appear “bulge-like” in the HST images. We suggest to use caution when comparing galaxy morphological types based on images at different resolutions or at different wavelengths, and whenever possible,to apply a reor n correction. More massive quiescent galaxies are systematically larger than the less massive ones,though no mass dependence is found for n measurements. The size–mass relation based on our sample and lowerz control samples show a monotonic increase of rewith M*, with a power-law of 0.61 ± 0.01, lower than previously found in similar samples of smaller sizes. Future high-resolution space-based surveys like NGRST will help confirm the possible n evolution, and if the flattening at the low-mass end is a genuine physical trend or limited by the image resolutions.展开更多
Ancient stellar observations are a valuable cultural heritage,profoundly influencing both cultural domains and modern astronomical research.Shi’s Star Catalog(石氏星经),the oldest extant star catalog in China,faces c...Ancient stellar observations are a valuable cultural heritage,profoundly influencing both cultural domains and modern astronomical research.Shi’s Star Catalog(石氏星经),the oldest extant star catalog in China,faces controversy regarding its observational epoch.Determining this epoch via precession assumes accurate ancient coordinates and correspondence with contemporary stars,posing significant challenges.This study introduces a novel method using the Generalized Hough Transform to ascertain the catalog’s observational epoch.This approach statistically accommodates errors in ancient coordinates and discrepancies between ancient and modern stars,addressing limitations in prior methods.Our findings date Shi’s Star Catalog to the 4th century BCE,with 2nd-century CE adjustments.In comparison,the Western tradition’s oldest known catalog,the Ptolemaic Star Catalog(2nd century CE),likely derives from the Hipparchus Star Catalog(2nd century BCE).Thus,Shi’s Star Catalog is identified as the world’s oldest known star catalog.Beyond establishing its observation period,this study aims to consolidate and digitize these cultural artifacts.展开更多
The spatiotemporal distribution and magnitude of seismicity collected over decades are crucial for understanding the stress interactions underlying large earthquakes.In this study,machine learning(ML)explainers identi...The spatiotemporal distribution and magnitude of seismicity collected over decades are crucial for understanding the stress interactions underlying large earthquakes.In this study,machine learning(ML)explainers identify and rank the features that distinguish Large Earthquake Occurrence(LEO)from non-LEO spatiotemporal windows.Seventy-eight statistics related to time,latitude,longitude,depth,and magnitude were extracted from the earthquake catalog(Global Centroid Moment Tensor)to produce 202,706 spatiotemporally discretized windows.ML explainers trained on these windows revealed the maximum magnitude(Mmax)as the most influential feature.Classification performance improved when the maximum inter-event time,the average interevent time,and the minimum ratio of focal depth to magnitude were jointly trained with Mmax.The top five features showed weak-to-moderate correlations,providing complementary information to the ML explainers.Our explainable ML framework can be extended to different earthquake catalogs,including those with focal mechanisms and smallmagnitude events.展开更多
Dentistry is a profession with a high prevalence of work-related musculoskeletal disorders(WMSDs),with symptoms often appearing very early in one’s career[1].WMSDs are conditions affecting the muscles,bones,and nervo...Dentistry is a profession with a high prevalence of work-related musculoskeletal disorders(WMSDs),with symptoms often appearing very early in one’s career[1].WMSDs are conditions affecting the muscles,bones,and nervous system due to occupational factors.In 2002,the International Labor Organization included musculoskeletal diseases in the International List of Occupational Diseases.China’s recently updated Classification and Catalog of Occupational Diseases has introduced two new categories of occupational illnesses,including occupational musculoskeletal disorders.WMSDs significantly impact the health and work of dentists,reducing their quality of life and causing economic losses.These disorders are multifactorial in nature,influenced by personal,psychosocial,biomechanical,and environmental factors.Dentists frequently maintain static or awkward postures during procedures,which leads to musculoskeletal strain and discomfort;additionally,long working hours contribute to psychological stress,further increasing the risk of WMSDs[2].展开更多
On the afternoon of September 29,2025,as part of the Beijing-Tianjin-Hebei Outstanding Popular Science Book Catalog Release and Popular Science Creation&Publishing Exchange Conference,the launch event for the Engl...On the afternoon of September 29,2025,as part of the Beijing-Tianjin-Hebei Outstanding Popular Science Book Catalog Release and Popular Science Creation&Publishing Exchange Conference,the launch event for the English edition of Hi,I'm China was held at the Beijing Library.Xie Gang,vice president of China International Communications Group,and Nie Zhenning,head of the national reading committee at the Publishers Association of China,attended the event and officially unveiled the new book.Representatives of readers from multiple countries,along with experts and scholars from various fields,were invited to participate.展开更多
Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avo...Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avoidance. Laser ranging is a kind of real-time measuring technology with high precision for space debris observation. The first space-debris laser-ranging experiment in China was performed at the Shanghai Observatory in July 2008 with a ranging precision of about 60-80 cm. The experi- mental results showed that the return signals from the targets with a range of 900 km were quite strong, with a power of 40W （2J at 20 Hz） using a 10ns pulse width laser at 532 nm wavelength. The performance of the preliminary laser ranging system and the observed results in 2008 and 2010 are also introduced.展开更多
We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle(θ_0) and coherence time(Τ_0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of ...We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle(θ_0) and coherence time(Τ_0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of short exposure images of selected stars were recorded with a high-speed, frame-transfer CCD mounted on the Cassegrain focus of a newly commissioned 1.3 m telescope. The estimated median seeing is ≈ 1.85 " at wavelength of ～ 600 nm, the image motion correlation between different pairs of stars is ～44% for θ0≈ 36" and mean Τ_0 is ≈ 2.4 ms. This work was motivated by the design considerations and expected performance of an adaptive optics system that is currently being planned for the telescope.展开更多
We combine K-nearest neighbors(KNN)with a genetic algorithm(GA)for photometric redshift estimation of quasars,short for GeneticKNN,which is a weighted KNN approach supported by a GA.This approach has two improvements ...We combine K-nearest neighbors(KNN)with a genetic algorithm(GA)for photometric redshift estimation of quasars,short for GeneticKNN,which is a weighted KNN approach supported by a GA.This approach has two improvements compared to KNN:one is the feature weighted by GA;the other is that the predicted redshift is not the redshift average of K neighbors but the weighted average of median and mean of redshifts for K neighbors,i.e.p×zmedian+(1-p)×zmean.Based on the SDSS and SDSS-WISE quasar samples,we explore the performance of GeneticKNN for photometric redshift estimation,comparing with the other six traditional machine learning methods,i.e.the least absolute shrinkage and selection operator(LASSO),support vector regression(SVR),multi-layer perceptrons(MLP),XGBoost,KNN and random forest.KNN and random forest show their superiority.Considering the easy implementation of KNN,we make improvement on KNN as GeneticKNN and apply GeneticKNN on photometric redshift estimation of quasars.Finally the performance of GeneticKNN is better than that of LASSO,SVR,MLP,XGBoost,KNN and random forest for all cases.Moreover the accuracy is better with the additional WISE magnitudes for the same method.展开更多
基金funded by the National Natural Science Foundation of China(Grant No. 10973009)This research makes use of data products UCAC3 (U.S. Naval Observatory)
文摘Considered to be extensions of the Hipparcos reference system, PPMX and UCAC3 are two of the most important astrometric catalogs released in current years. Extensive analyses of these two large catalogs have been made in order to determine the local and overall systematic biases. The regional and magnitude dependent differences in stellar position and proper motion are comparable to random errors and are even larger in the northern hemisphere. The global orientation bias vector ε between the two systems is also significant （up to 17 mas）, which shows the overall differences of the PPMX and UCAC3 catalogs and their reference systems. On the other hand, the term for the global rotation vector a; is small （tenths of mas per year）： it is reasonable to believe that the PPMX and UCAC3 reference frames do not rotate with respect to each other. Because of plate dependent and field-to-field errors in the UCAC3 catalog, we suggest that positions and proper motions of UCAC3 stars in the northern hemisphere （δ 〉 -20°） should be used with caution.
基金science research grants from the China Manned Space Project with No.CMS-CSST-2021-A01。
文摘Quasars can be used to measure baryon acoustic oscillations at high redshift, which are considered as direct tracers of the most distant large-scale structures in the universe. It is fundamental to select quasars from observations before implementing the above research. This work focuses on creating a catalog of quasar candidates based on photometric data to provide primary priors for further object classification with spectroscopic data in the future, such as the Dark Energy Spectroscopic Instrument(DESI) Survey. We adopt a machine learning algorithm(Random Forest, RF) for quasar identification. The training set includes 651,073 positives and 1,227,172 negatives, in which the photometric information are from DESI Legacy Imaging Surveys(DESI-LIS) and Wide-field Infrared Survey Explore(WISE), and the labels are from a database of spectroscopically confirmed quasars based on Sloan Digital Sky Survey and the Set of Identifications& Measurements and Bibliography for Astronomical Data. The trained RF model is applied to point-like sources in DESI-LIS Data Release 9. To quantify the classifier’s performance, we also inject a testing set into the to-be-applied data.Eventually, we obtained 1,953,932 Grade-A quasar candidates and 22,486,884 Grade-B quasar candidates out of425,540,269 sources(~5.7%). The catalog covers ~99% of quasars in the to-be-applied data by evaluating the completeness of the classification on the testing set. The statistical properties of the candidates agree with that given by the method of color-cut selection. Our catalog can intensely decrease the workload for confirming quasars with the upcoming DESI data by eliminating enormous non-quasars but remaining high completeness. All data in this paper are publicly available online.
文摘Ancient China recorded a wealth of astronomical observations,notably distinguished by the inclusion of empirical measurements of stellar observations.However,determining the precise observational epochs for these datasets poses a formidable challenge.This study employs the generalized Hough transform methodology to analyze two distinct sets of observational data originating from the Song and Yuan dynasties,allowing accurate estimation of the epochs of these stellar observations.This research introduces a novel and systematic approach,offering a scholarly perspective for the analysis of additional datasets within the domain of ancient astronomical catalogs in future investigations.
基金Supported by the National Natural Science Foundation of China
文摘The currently used Galactic coordinate system（GalC S） is based on the FK5 system at J2000.0, which was transformed from the FK4 system at B1950.0.The limitations and misunderstandings related to this transformed GalC S can be avoided by defining a new GalC S that is directly connected to the International Celestial Reference System（ICRS）. With more data at various wavelengths released by large survey programs, a more appropriate GalC S consistent with features associated with the Milky Way can be established. We try to find the best orientation of the GalC S using data from two all-sky surveys, AKARI and WISE, at six wavelengths between 3.4 μm and 90 μm, and synthesize results obtained at various wavelengths to define an improved GalC S in the framework of the ICRS. The revised GalC S parameters for defining the new GalC S in the ICRS are summarized as：αp= 192.777°, δp= 26.9298°, for the equatorial coordinates of the north Galactic pole and θ = 122.95017° for the position angle of the Galactic center. As one of the Galactic substructures, the Galactic warp exhibits different forms in different GalC Ss that are constructed with various data and methods, which shows the importance of re-defining the GalC S by the relative commission of the International Astronomical Union that can lead to a better understanding of Galactic structure and kinematics.
文摘Taiwan is a region with very high seismicity where hundreds of earthquakes with ms occurred per year and more than 40 with m≥7 since 1900 due to it is located at the boundary of collision between Eurasian and the Philippine Sea plates.The magnitudes for the same event from these two catalogs of Taiwan and Beijing are different due to diferent data sources selected and different magnitude scales used. To measure sizes of Taiwan events in uniform magnitude scale, the author adopted a catalog of earthquakes with uniform local magnitude scale (Shin, 1993)compiled by Cheng (1996) in compiling a new catalog of Chinese earthquakes. To measure sizes of Taiwan events,we adopted uniform local magnitude scale for events with 5≤M<6. For event with M≥6 we still adopted IASPEI surface wave magnitude scale. Thus the statistic difference between two magnitude values from Taiwan and Beijing in magnitude interval 5≤M<6 reflects difference between Taiwan uniform local magnitode scale and Beijing surface wave magnitude scale. The statistic difference in magnitude interval he6 reflects difference between IASPEI surface wave magnitude scale and Beijing surface wave magnitude scale. Three data sources from "Wang","Cheng" and "Chinese mainland" of Taiwan events with m≥7 are given in this paper, in order to obtain a complete catalog.The statistic result indicates that Taiwan magnitude is slightly larger than Beijing magnitude for 998 events with 5≤M<6. The mean difference is about 0.13 of magnitude unit with deviation 0.32. Similarly, the mean difference is about 0.09 of magnitude unit with deviation 0.23 for 298 eventS with m≥6. We also noted that the difference of magnitude values between Beijing and Taiwan surface wave magnitUdes changed in different time period.Before 1971, most Taiwan magnitude values of the events is larger than Beijing’s. In contrast, most Beijing magnitude values of the events are larger than Taiwan magnitUde values aller 1972. It is probably related to data sources. Three catalogs of events with m≥7 are given in this paper Wang’s catalog (1995) includes 44 events with M≥7, Cheng’s (1996) 39 events and Chinese catalog, before 1911 compiled by Min (1995), 1912-1990 compiled by Wang, et al (1997) and 1991-1998 compiled by Yang, includes 41 events. The variety of these data sources discussed in this paper can be a useful reference for seismologists who use catalog seismic data do their research.However the statistic results and empirical relations presented in this paper can not be used for converting between magnitude scales, since some of them are not the original observation values. In addition, three catalogs of events with M≥ 7 given in this paper can be used for seismicity research comprehensively.
文摘West Africa is considered a region of low seismicity. However, the monitoring of earthquake activity by local seismic arrays began very early (as early as 1914) in West Africa but seismic catalogs are very incomplete. In 1991, Bertil studied the seismicity of West Africa based on networks of seismic stations in Ivory Coast and neighboring countries. The reference work of Ambraseys and Adams as well as the recent earthquakes given by the international data centres on the seismicity of West Africa were also used for the computations of earthquake hazard parameters. Different earthquake event data have been compiled and homogenised to moment magnitude (</span><i><span style="font-family:Verdana;">M</span><sub><span style="font-family:Verdana;">w</span></sub></i><span style="font-family:Verdana;">). The obtained catalog covers a period of over four centuries (1615-2021) and contains large historical events and recent complete observations. The complete catalog part has been subdivided into four complete subcatalogs with each a level of completeness. The minimum magnitude and the maximum observed magnitude are equal to 2.89 and 6.8 respectively for the whole catalog. The seismic code software developed by Kijko was used to calculate the earthquake hazard parameters. The results give a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">b</span></i></span></span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">value of 0.83 ± 0.08 for the whole period and preliminary seismic hazards curves are also plotted for re</span><span style="font-family:Verdana;">turn periods 25, 50 and 100 years. This is a good and practical example</span><span style="font-family:Verdana;"> showing that this procedure can be used for seismic hazard assessment in West Africa.
文摘The increasing availability of government data has prompted efforts to standardize data cataloging practices for enhanced accessibility and usability.The primary aim of this study is to descriptively assess data catalog and referenced dataset volume,metadata utilization,and thematic composition of United States DCAT compliant data catalogs across Federal,State,County,City,and Territory entities.Data collection involved compiling a list of relevant government agencies and data resources to identify data catalogs.DCAT compliance was then assessed,and metadata from compliant catalogs was extracted.Thematic mapping utilized Python packages RegEx and FuzzyWuzzy to categorize themes into eight standard categories.A combination of descriptive statistics and 1-way ANOVA tests were conducted to analyze dataset volume,metadata utilization,and reported themes.Of the 305 data catalogs identified,259 were found to be DCAT compliant.Federal entities exhibited the highest DCAT compliance rates(92.3%),followed by County(88.1%),City(86.9%),and State(77.0%),while Territory(0%)had no compliant data catalogs.Descriptive analysis revealed that federal DCAT compliant data catalogs(n=59)had the highest average number of data assets across their data catalogs(μ=1,133.2)with the predominant themes being transportation at 21.2%(n=14,785)and geospatial at 15.4%(n=10,761).While county data catalogs(n=52)had the lowest average(μ=232.6)with the most referenced themes being geospatial at 77.6%(n=8450)and finance at 2.4%(n=270).After applying thematic mapping to eight standard categories,the three most dominant themes across all entities were transportation at 38.1%(n=16,504),natural resources with 19.6%(n=8,501),and health and safety with 14.7%(n=6,367).These findings underscore the widespread adoption of the DCAT standard across government entities,with notable gaps at the territorial level.Federal and state entities exhibited the highest data catalog and dataset volumes,while metadata utilization remained relatively consistent across all entity levels.The thematic analysis highlights the importance of standardization efforts to enhance thematic consistency and facilitate effective data interpretation.Further collaboration and investment are warranted to address gaps in catalog coverage and establish standardized data cataloging practices to maximize the accessibility and usability of these data catalogs along with their referenced datasets.
基金supported by the National Natural Science Foundation of China(Grant Nos.10973021,11078013 and 11233004)
文摘We introduce an algorithm to solve the block-edge problem taking advantage of the two different sky splitting functions： HTM and HEALPix. We make the cross-match with the two functions, and then we obtain the union set of the two different sets. We use the ThreadPool technique to speed up the cross-match. In this way improved accuracy can be obtained on the cross-match. Our experiments show that this algorithm has a remarkable performance superiority compared with the previous ones and can be applied to the cross-match between large-scale catalogs. We give some ideas about solving the many-for-one situation occurred in the cross-match.
文摘This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE was conducted using publicly accessible data that concentrated on star formation rates(SFRs)and depletion timescales.By employing the fundamental equation,I determined the SFE in relation to its freefall time,which highlighted variations in efficiencies associated with SFR masses derived from different spectra.The results demonstrated that the highest efficiency value was observed in the analysis of the 1.4 GHz radio continuum,emphasizing the importance of studying star-forming clouds across a range of electromagnetic wavelengths to achieve a comprehensive understanding of star formation mechanisms.The study's findings indicated a peak efficiency of star formation value of approximately 0.9%,while the relative minimum obtained from(O II)was around 0.42%,aligning with the range of SFEs documented in the existing literature.Additionally,investigating the factors that influence the variability in efficiency when examining clouds in BCGs across different wave bands is crucial for deepening our comprehension of the underlying processes of star formation.
文摘Natural earthquakes and micro-seismicity resulting from hydraulic fracturing or other engineering practices display distinctively different spatial-temporal features,like mixed burst-and swarm-like features or predominantly swarm-like features.The mechanism(s)contributing to such observations can be diverse.We present the inspections on the dynamic formation process of the single swarm-like tree in laboratory acoustic emission(AE)catalogs.Such largest swarm-like trees can contain>97%AE events from the entire catalog within a test;and all catalogs under investigation display scale-invariance features.The formation of the largest swarm-like tree correlates with the rock fracture process analogue of the source pervasive process,where its AE releases exhibit significant spatial well-organization.Comparison to other laboratory catalogs under different laboratory settings helps us identify the spatial continuity of the rock fracture process as the primary factor in forming the largest swarm-like trees at laboratory scale.The stress transfer process is involved in the rock fracture process for the tests having pre-existing spatial discontinuity.Artificial perturbations on the spatial information induced by the stress transfer process further confirm that stress transfer also serves to shift the pure swarm-like catalog into a mixed burst-and swarm-like catalog.These laboratory observations may provide inspirational insights for understanding the field-scale mechanism(s)shaping the spatial-temporal energy release features.
基金supported by the National Natural Science Foundation of China (NSFC, Grant No. U1731128)
文摘In the task of classifying massive celestial data,the accurate classification of galaxies,stars,and quasars usually relies on spectral labels.However,spectral data account for only a small fraction of all astronomical observation data,and the target source classification information in vast photometric data has not been accurately measured.To address this,we propose a novel deep learning-based algorithm,YL8C4Net,for the automatic detection and classification of target sources in photometric images.This algorithm combines the YOLOv8 detection network with the Conv4Net classification network.Additionally,we propose a novel magnitude-based labeling method for target source annotation.In the performance evaluation,the YOLOv8 achieves impressive performance with average precision scores of 0.824 for AP@0.5 and 0.795 for AP@0.5:0.95.Meanwhile,the constructed Conv4Net attains an accuracy of 0.8895.Overall,YL8C4Net offers the advantages of fewer parameters,faster processing speed,and higher classification accuracy,making it particularly suitable for large-scale data processing tasks.Furthermore,we employed the YL8C4Net model to conduct target source detection and classification on photometric images from 20 sky regions in SDSS-DR17.As a result,a catalog containing about 9.39 million target source classification results has been preliminarily constructed,thereby providing valuable reference data for astronomical research.
基金supported by the National Natural Science Foundation of China(NSFC)under grant Nos.12261141689,12090044,and 12090040sponsored by the Xinjiang Uygur Autonomous Region“Tianchi Talent”Introduction Plan。
文摘The Stellar Abundances and Galactic Evolution Survey(SAGES)is a multi-band survey that covers the northern sky area of~12,000 deg2.The Nanshan One-meter Wide-field Telescope(NOWT)of the Xinjiang Astronomical Observatory carried out observations on g/r/i bands.Here,we present the survey strategy,data processing,catalog construction,and database schema.The observations of NOWT started in 2016 August and were completed in2018 January,a total of 17,827 frames were obtained and~4600 deg2 sky areas were covered.In this paper,we release the catalog of the data in the g/r/i bands observed by NOWT.In total,there are 109,197,578 items of source records.The catalog is the supplement for the SDSS for the bright end,and the combination of our catalog and these catalogs could be helpful for source selections for other surveys and Milky Way sciences,e.g.,white dwarf candidates and stellar flares.
基金sponsored by the National Key R&D Program of China(MOST)with grant No.2022YFA1605300the National Natural Science Foundation of China(NSFC,grant Nos.12273051 and 11933003)Support for this work is also partly provided by the Chinese Academy of Sciences(CAS)through a grant to the South America Center for Astronomy(CASSACA)。
文摘We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent region in the rest-frame UVJ diagram. Comparing the five HSC bands and the subsample with HST F160W images, consistent with the decreasing effective radius re, Sérsic index n shows an increasing trend indicating a more bulge-dominant morphology towards the infrared. Even for our massive, quiescent galaxies,which are dominated by typical elliptical galaxies with bulges, the reand n values still vary with the wavelengths.For instance, there is a systematic drop in n of ~0.4 going from y band to F160W, making 20% of the HSC “disklike” galaxies appear “bulge-like” in the HST images. We suggest to use caution when comparing galaxy morphological types based on images at different resolutions or at different wavelengths, and whenever possible,to apply a reor n correction. More massive quiescent galaxies are systematically larger than the less massive ones,though no mass dependence is found for n measurements. The size–mass relation based on our sample and lowerz control samples show a monotonic increase of rewith M*, with a power-law of 0.61 ± 0.01, lower than previously found in similar samples of smaller sizes. Future high-resolution space-based surveys like NGRST will help confirm the possible n evolution, and if the flattening at the low-mass end is a genuine physical trend or limited by the image resolutions.
基金supported by China National Astronomical Data Center(NADC),CAS Astronomical Data Center and Chinese Virtual Observatory(China-VO)supported by Astronomical Big Data Joint Research Center,co-founded by National Astronomical Observatories,Chinese Academy of Sciences and Alibaba Cloud。
文摘Ancient stellar observations are a valuable cultural heritage,profoundly influencing both cultural domains and modern astronomical research.Shi’s Star Catalog(石氏星经),the oldest extant star catalog in China,faces controversy regarding its observational epoch.Determining this epoch via precession assumes accurate ancient coordinates and correspondence with contemporary stars,posing significant challenges.This study introduces a novel method using the Generalized Hough Transform to ascertain the catalog’s observational epoch.This approach statistically accommodates errors in ancient coordinates and discrepancies between ancient and modern stars,addressing limitations in prior methods.Our findings date Shi’s Star Catalog to the 4th century BCE,with 2nd-century CE adjustments.In comparison,the Western tradition’s oldest known catalog,the Ptolemaic Star Catalog(2nd century CE),likely derives from the Hipparchus Star Catalog(2nd century BCE).Thus,Shi’s Star Catalog is identified as the world’s oldest known star catalog.Beyond establishing its observation period,this study aims to consolidate and digitize these cultural artifacts.
基金supported by the National Research Foundation of Korea(RS-2025-02293161,NRF-2022R1A2C1009742,and No.2019R1A6A1A03033167)awarded to B.So.J.Jang is supported by the Ministry of the Interior and Safety,as the Human Resource Development Project in Disaster Managementsupported by Korea Institute of Marine Science&Technology Promotion(KIMST)funded by the Ministry of Oceans and Fisheries(RS-2023-00254680 and RS-2023-00259686).
文摘The spatiotemporal distribution and magnitude of seismicity collected over decades are crucial for understanding the stress interactions underlying large earthquakes.In this study,machine learning(ML)explainers identify and rank the features that distinguish Large Earthquake Occurrence(LEO)from non-LEO spatiotemporal windows.Seventy-eight statistics related to time,latitude,longitude,depth,and magnitude were extracted from the earthquake catalog(Global Centroid Moment Tensor)to produce 202,706 spatiotemporally discretized windows.ML explainers trained on these windows revealed the maximum magnitude(Mmax)as the most influential feature.Classification performance improved when the maximum inter-event time,the average interevent time,and the minimum ratio of focal depth to magnitude were jointly trained with Mmax.The top five features showed weak-to-moderate correlations,providing complementary information to the ML explainers.Our explainable ML framework can be extended to different earthquake catalogs,including those with focal mechanisms and smallmagnitude events.
基金supported by the 2021 Shandong Province Higher Education Institutions“Youth Innovation Talent Introduction and Cultivation Plan”(Public Health Safety Risk Assessment and Response Innovation Team)National Traditional Chinese Medicine Comprehensive Reform Demonstration Zone Science and Technology Co construction Project(No.GZYKJSSD-2024-106)Research Project of Shandong Educational Supervision Society(No.SDJYDDXH2023-2159).
文摘Dentistry is a profession with a high prevalence of work-related musculoskeletal disorders(WMSDs),with symptoms often appearing very early in one’s career[1].WMSDs are conditions affecting the muscles,bones,and nervous system due to occupational factors.In 2002,the International Labor Organization included musculoskeletal diseases in the International List of Occupational Diseases.China’s recently updated Classification and Catalog of Occupational Diseases has introduced two new categories of occupational illnesses,including occupational musculoskeletal disorders.WMSDs significantly impact the health and work of dentists,reducing their quality of life and causing economic losses.These disorders are multifactorial in nature,influenced by personal,psychosocial,biomechanical,and environmental factors.Dentists frequently maintain static or awkward postures during procedures,which leads to musculoskeletal strain and discomfort;additionally,long working hours contribute to psychological stress,further increasing the risk of WMSDs[2].
文摘On the afternoon of September 29,2025,as part of the Beijing-Tianjin-Hebei Outstanding Popular Science Book Catalog Release and Popular Science Creation&Publishing Exchange Conference,the launch event for the English edition of Hi,I'm China was held at the Beijing Library.Xie Gang,vice president of China International Communications Group,and Nie Zhenning,head of the national reading committee at the Publishers Association of China,attended the event and officially unveiled the new book.Representatives of readers from multiple countries,along with experts and scholars from various fields,were invited to participate.
基金supported by the Chinese Space Agency and the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. 2920100701)
文摘Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avoidance. Laser ranging is a kind of real-time measuring technology with high precision for space debris observation. The first space-debris laser-ranging experiment in China was performed at the Shanghai Observatory in July 2008 with a ranging precision of about 60-80 cm. The experi- mental results showed that the return signals from the targets with a range of 900 km were quite strong, with a power of 40W （2J at 20 Hz） using a 10ns pulse width laser at 532 nm wavelength. The performance of the preliminary laser ranging system and the observed results in 2008 and 2010 are also introduced.
文摘We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle(θ_0) and coherence time(Τ_0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of short exposure images of selected stars were recorded with a high-speed, frame-transfer CCD mounted on the Cassegrain focus of a newly commissioned 1.3 m telescope. The estimated median seeing is ≈ 1.85 " at wavelength of ～ 600 nm, the image motion correlation between different pairs of stars is ～44% for θ0≈ 36" and mean Τ_0 is ≈ 2.4 ms. This work was motivated by the design considerations and expected performance of an adaptive optics system that is currently being planned for the telescope.
基金the National Key R&D Program of China(Grant No.2018YFB 1702703)funded by the National Natural Science Foundation of China(Grant Nos.11873066,U1531122 and U1731109)+3 种基金Funding for the Sloan Digital Sky Survey(SDSS)Ⅳhas been provided by the Alfred P.Sloan Foundationthe U.S.Department of Energy Office of Science,and the Participating Institutionssupport and resources from the Center for High-Performance Computing at the University of UtahThe Wide-field Infrared Survey Explorer(WISE)is a joint project of the University of California,Los Angeles,and the Jet Propulsion Laboratory/California Institute of Technology,funded by the National Aeronautics and Space Administration。
文摘We combine K-nearest neighbors(KNN)with a genetic algorithm(GA)for photometric redshift estimation of quasars,short for GeneticKNN,which is a weighted KNN approach supported by a GA.This approach has two improvements compared to KNN:one is the feature weighted by GA;the other is that the predicted redshift is not the redshift average of K neighbors but the weighted average of median and mean of redshifts for K neighbors,i.e.p×zmedian+(1-p)×zmean.Based on the SDSS and SDSS-WISE quasar samples,we explore the performance of GeneticKNN for photometric redshift estimation,comparing with the other six traditional machine learning methods,i.e.the least absolute shrinkage and selection operator(LASSO),support vector regression(SVR),multi-layer perceptrons(MLP),XGBoost,KNN and random forest.KNN and random forest show their superiority.Considering the easy implementation of KNN,we make improvement on KNN as GeneticKNN and apply GeneticKNN on photometric redshift estimation of quasars.Finally the performance of GeneticKNN is better than that of LASSO,SVR,MLP,XGBoost,KNN and random forest for all cases.Moreover the accuracy is better with the additional WISE magnitudes for the same method.
