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Problems and Recommendations for Rural Statistics and Survey Methods
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作者 Chengjun ZHANG 《Asian Agricultural Research》 2014年第8期5-7,共3页
With constant deepening of the reform and opening-up,national economic system has changed from planned economy to market economy,and rural survey and statistics remain in a difficult transition period. In this period,... With constant deepening of the reform and opening-up,national economic system has changed from planned economy to market economy,and rural survey and statistics remain in a difficult transition period. In this period,China needs transforming original statistical mode according to market economic system. All levels of government should report and submit a lot and increasing statistical information. Besides,in this period,townships,villages and counties are faced with old and new conflicts. These conflicts perplex implementation of rural statistics and survey and development of rural statistical undertaking,and also cause researches and thinking of reform of rural statistical and survey methods. 展开更多
关键词 RURAL areas statistics survey METHODS PRObLEMS and
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Travel-Limiting Disabilities in the United States: Why Accessibility Matters?
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作者 Oluwaseun Ibukun Bhuiyan Alam 《Journal of Transportation Technologies》 2024年第3期336-357,共22页
This study evaluates the distribution of travel-limiting disabilities across genders and geographic locations in the United States. This study aims to describe and compare the socioeconomic and demographic variables o... This study evaluates the distribution of travel-limiting disabilities across genders and geographic locations in the United States. This study aims to describe and compare the socioeconomic and demographic variables of the people with and without travel-limiting disabilities across geographic locations and gender. The study further evaluates the trip purpose and impact of Covid-19 fourth wave pandemic on the use of public transit and travel to physical workplace for the people with and without travel-limiting disabilities across gender and geographic locations. The study uses the 2022 weighted National Household Travel Survey dataset and employs descriptive statistics. Results reaffirm the findings from previous literature that there are more people with travel-limiting disabilities in urban areas and among women. Over 50 percent of people aged 65 and above have a form of travel-limiting disabilities. The most trip for people with travel-limiting disabilities is made for shopping and medical purposes. Across all categories, rural areas, urban areas, male and female for the people without travel-limiting disabilities, COVID-19 fourth wave did not change the pattern of trips made to physical workplace as pre-COVID-19 era. This pattern is also observable for the people with travel-limiting disabilities in rural and urban areas. Females with travel-limiting disabilities reported making less trips to physical workplaces while male reported doing the same as before COVID-19 era. The study concludes that the quantification of travel-limiting disabilities across geographic location and gender is vital in disability study and could drive policy implementation for improved accessibility for the vulnerable population. 展开更多
关键词 National Household Travel survey United States Travel-Limiting Disabilities Descriptive statistics Covid-19 Disability Study
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New Composite Indicator for the Business Tendency Survey
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作者 Olga O. Vasyechko Michel Grun-Rehomme 《Journal of Mathematics and System Science》 2011年第1期60-70,共11页
Short-term surveys provide precious information for economic fluctuations analysis. In short-term surveys like the business tendency survey, most of the questions are qualitative and concern the evolution of different... Short-term surveys provide precious information for economic fluctuations analysis. In short-term surveys like the business tendency survey, most of the questions are qualitative and concern the evolution of different economic factors of the business activity. They provide economic information on the present situation and short-term perspectives. Usually, the respondents have to choose between three possible evolutions: increase (improvement, favourable, level higher than the normal), stability (normal) or decrease (unfavourable, level lower than the normal). The balance of opinion is defined as the difference between the proportion of respondents expressing a positive opinion and the proportion expressing a negative opinion. To analyze these types of surveys, the methods are well standardized and use both the multidimensional approach and time series (scoring, dynamic factor analysis, etc.) In this paper, the authors propose a new method of calculating a robust composite indicator based on range median statistics, and on a lexicographical order relation of the individual data. A confidence interval is constructed around these statistics. The indicator's advantage is simplicity of calculation in comparison with the Mitchell, Smith and Weale (2004) index (MSW), while its effectiveness seems to be of the same order. It was used on a Ukrainian dataset for the construction sector. This procedure can be applied to the surveys that contain correlated ordered qualitative answers. 展开更多
关键词 business tendency survey time series balance of opinion robust statistics composite indicators.
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Is There an Improvement of Antibiotic Use in China? Evidence from the Usage Analysis of Combination Antibiotic Therapy for Type Ⅰ Incisions in 244 Hospitals 被引量:5
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作者 周文娟 罗桢妮 +3 位作者 唐昌敏 邹晓旭 赵露 方鹏骞 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2016年第5期772-779,共8页
The improvement of antibiotic rational use in China was studied by usage analysis of combination antibiotic therapy for type Ⅰ incisions in 244 hospitals. Five kinds of hospitals, including general hospital, maternit... The improvement of antibiotic rational use in China was studied by usage analysis of combination antibiotic therapy for type Ⅰ incisions in 244 hospitals. Five kinds of hospitals, including general hospital, maternity hospital, children's hospital, stomatological hospital and cancer hospital, from 30 provinces were surveyed. A systematic random sampling strategy was employed to select outpatient prescriptions and inpatient cases in 2011 and 2012. A total of 29 280 outpatient prescriptions and 73 200 inpatient cases from 244 hospitals in each year were analyzed. Data were collected with regards to the implementation of the national antibiotic stewardship program(NASP), the overall usage and the prophylactic use of antibiotic for type Ⅰ incisions. Univariate analysis was used for microbiological diagnosis rate before antimicrobial therapy, prophylactic use of antibiotics for typeⅠincision operation, and so on. For multivariate analysis, the use of antibiotics was dichotomized according to the guidelines, and entered as binary values into logistic regression analysis. The results were compared with the corresponding criteria given by the guidelines of this campaign. The antibiotic stewardship in China was effective in that more than 80% of each kind of hospitals achieved the criteria of recommended antibiotics varieties. Hospital type appeared to be a factor statistically associated with stewardship outcome. The prophylactic use of antibiotics on type Ⅰ incision operations decreased by 16.22%(P〈0.05). The usage of combination antibiotic therapy for type Ⅰ incisions was also decreased. Region and bed size were the main determinants on surgical prophylaxis for type Ⅰ incision. This national analysis of hospitals on antibiotic use and stewardship allows relevant comparisons for bench marking. More efforts addressing the root cause of antibiotics abuse would continue to improve the rational use of antibiotics in China. 展开更多
关键词 antibiotics Antibiotic outpatient inpatient incision usage multivariate surveyed statistically addressing
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A Preliminary Study on the Calculating Method for the Evolution of Siltation and Erosion of Tidal Flat Based on GIS 被引量:1
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作者 杜景龙 郜昂 +3 位作者 杨世伦 张文祥 赵华云 李鹏 《Marine Science Bulletin》 CAS 2005年第1期45-53,共9页
T he estuary and coast is an area where the land and the sea interact and a place in which human beings frequently move about so that understanding and controlling the change and development modes of the coastal landf... T he estuary and coast is an area where the land and the sea interact and a place in which human beings frequently move about so that understanding and controlling the change and development modes of the coastal landform plays a vital part in exploiting and protecting coastal resources. A model is the generalization and abstraction of objective things. This paper summarizes four methods for the landform development of the tidal shore and underwater delta, mainly discusses the model’s structural elements, and presents their specific application on the basis of the authors’ case study. With the application of the profile model, the dynamic change of coastal landform can be clearly seen by contrasting the different profiles of different years. Through the shrinking, expanding and transformation of the isobath, plane model is used to study the macro-change of the shoal and the coastal landform. Speed model is an efficient means to analyze the trend of erosion and deposition and the local change in a great area of the sea. Statistical survey model is a static analysis, which can be used to establish the relationship between the erosion and deposition of the shoal and the altitude and slope of survey spot. 展开更多
关键词 p rofile model p lane model speed model statistical survey model Yangtze Estuary
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The relative calibration of radial velocity for LAMOST medium resolution stellar spectra
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作者 Jian-Ping Xiong Bo Zhang +3 位作者 Chao Liu Jiao Li Yong-Heng Zhao Yong-Hui Hou 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第10期239-249,共11页
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)started a medianresolution spectroscopic(MRS,R~7500)survey since October 2018.The main scientific goals of MRS,including binary stars,pulsators and ... The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)started a medianresolution spectroscopic(MRS,R~7500)survey since October 2018.The main scientific goals of MRS,including binary stars,pulsators and other variable stars,were launched with a time-domain spectroscopic survey.However,the systematic errors,including the bias induced from wavelength calibration and the systematic difference between different spectrographs,have to be carefully considered during radial velocity measurement.In this work,we provide a technique to correct the systematics in the wavelength calibration based on the relative radial velocity measurements from LAMOST MRS spectra.We show that,for the stars with multi-epoch spectra,the systematic bias which is induced from the exposures on different nights can be corrected well for LAMOST MRS in each spectrograph.In addition,the precision of radial velocity zero-point of multi-epoch time-domain observations reaches below 0.5 km s^(-1).As a by-product,we also give the constant star candidates^(**),which can be the secondary radial-velocity standard star candidates of LAMOST MRS time-domain surveys. 展开更多
关键词 methods:data analysis techniques:radial velocities stars:statistics catalogs surveys
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LAMOST MRS-N Observation of the W80 Region
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作者 Yao Li Chao-Jian Wu +12 位作者 Yong-Qiang Yao Wei Zhang Jia Yin Juan-Juan Ren Chih-Hao Hsia Rui Zhuang Jian-Jun Chen Yu-Zhong Wu Hui Zhu Bin Li Yong-Hui Hou Meng-Yuan Yao Hong Wu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第7期161-175,共15页
The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(... The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST).A total of 2982 high-quality nebular spectra have been obtained in the 20 square degree field of view which covers the W80 complex,and the largest sample of spectral data has been established for the first time.The relative intensities,radial velocities(RVs),and full widths at half maximum(FWHMs) are measured with the high spectral resolution of LAMOST MRS-N,for Ha λ6563?,[NⅡ] λλ6548 A,6584 A,and [SⅡ] λλ6716A,6731 A emission lines.In the field of view of the whole W80 region,the strongest line emissions are found to be consistent with the bright nebulae NGC 7000,IC 5070,and LBN 391,and weak line emissions also exist in the Middle Region,where no bright nebulae are detected by the wide-band optical observations.The large-scale spectral observations of the W80 region reveal the systematic spatial variations of RVs and FWHMs,and several unique structural features.A "curved feature" to the east of NGC 7000,and a "jet feature" to the west of LBN 391 are detected to be showing larger RVs.A "wider FWHM region" is identified in the eastern part of NGC 7000.The variations of[S Ⅱ]/Ha ratios display a gradient from southwest to northeast in the NGC 7000 region,and manifest a ring shape around the "W80 bubble" ionized by an O-type star in L935.Further spectral and multi-band observations are guaranteed to investigate in detail the structural features. 展开更多
关键词 surveys (ISM:)HII regions ISM:molecules ISM:bubbles methods:statistical
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Forecasts of cosmological constraints from HI intensity mapping with FAST,BINGO and SKA-I
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作者 Elimboto Yohana Yi-Chao Li Yin-Zhe Ma 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2019年第12期343-360,共18页
We forecast the cosmological constraints of the neutral hydrogen(HI) intensity mapping(IM)technique with radio telescopes by assuming 1-year of observational time. The current and future radio telescopes that we consi... We forecast the cosmological constraints of the neutral hydrogen(HI) intensity mapping(IM)technique with radio telescopes by assuming 1-year of observational time. The current and future radio telescopes that we consider here are Five-hundred-meter Aperture Spherical radio Telescope(FAST), Baryon acoustic oscillations In Neutral Gas Observations(BINGO), and Square Kilometre Array phase Ⅰ(SKA-Ⅰ) single-dish experiments. We also forecast the combined constraints of the three radio telescopes with Planck. We find that the 1σ errors of(w0, wa) for BINGO, FAST and SKA-Ⅰ with respect to the fiducial values are respectively,(0.9293, 3.5792),(0.4083, 1.5878) and(0.3158, 0.4622). This is equivalent to(56.04%, 55.64%) and(66.02%, 87.09%) improvements in constraining(w0, wa) for FAST and SKA-Ⅰ respectively relative to BINGO. Simulations further show that SKA-Ⅰ will put more stringent constraints than both FAST and BINGO when each of the experiments is combined with Planck measurements. The 1σ errors for(w0, wa), BINGO + Planck, FAST + Planck and SKA-Ⅰ + Planck covariance matrices are respectively(0.0832, 0.3520),(0.0791, 0.3313) and(0.0678, 0.2679) implying there is an improvement in(w0, wa) constraints of(4.93%, 5.88%) for FAST + Planck relative to BINGO + Planck and an improvement of(18.51%, 23.89%) in constraining(w0, wa) for SKA-Ⅰ + Planck relative to BINGO + Planck. We also compared the performance of Planck data plus each single-dish experiment relative to Planck alone,and find that the reduction in(w0, wa) 1σ errors for each experiment plus Planck, respectively, imply the(w0, wa) constraints improvement of(22.96%, 8.45%),(26.76%, 13.84%) and(37.22%, 30.33%) for BINGO + Planck, FAST + Planck and SKA-Ⅰ + Planck relative to Planck alone. For the nine cosmological parameters in consideration, we find that there is a trade-off between SKA-Ⅰ and FAST in constraining cosmological parameters, with each experiment being more superior in constraining a particular set of parameters. 展开更多
关键词 surveys galaxies:statistics cosmology:observations large-scale structure of Universe galaxies:kinematics and dynamics
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Series Statistics Data of Non-ferrous Metals of China──Ⅰ Surveying
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《中国有色金属学会会刊:英文版》 CSCD 1996年第2期152-153,共2页
SeriesStatisticsDataofNon-ferrousMetalsofChinaⅠ2ASurveyingofTheChinaNationalNon-ferrousMetalsIndustryCorpcra... SeriesStatisticsDataofNon-ferrousMetalsofChinaⅠ2ASurveyingofTheChinaNationalNon-ferrousMetalsIndustryCorpcration(CNNC)Bycourt... 展开更多
关键词 Series statistics Data of Non-ferrous Metals of China surveyING
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Preliminary survey on animal research statistics in Sri Lanka from 2010 onwards
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作者 Chedliya Ishak Sahabdeen Mangala Gunatilake 《Animal Models and Experimental Medicine》 2018年第2期79-81,共3页
Background: Animal research is conducted in many countries across the world.However, concepts of recording and reporting the numbers of animals used vary. In the context of animal studies, inadequate reporting raises ... Background: Animal research is conducted in many countries across the world.However, concepts of recording and reporting the numbers of animals used vary. In the context of animal studies, inadequate reporting raises both ethical and scientific concerns. Sri Lanka has yet to publish data on animal research statistics.Methods: The objective of this survey was to present the number and types of vertebrate animals used for research and establish the species used for different types of research studies. All facilities/personnel engaged in animal research were invited to participate and a web-based survey was performed.Results: Based on the data collected, rats and mice were the most widely used animals in Sri Lankan laboratories. Of these, the most reported model were rats of the Wistar strain(42%) and mice of the BALB/c strain(15%). The highest number of animals used in laboratory research occurred in 2011, with a 12% decrease observed in 2012. 展开更多
关键词 ANIMAL research SRI Lanka statistics survey WISTAR rats
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Candidate members of star clusters from LAMOST DR2
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作者 Bo Zhang Xiao-Yan Chen +10 位作者 Chao Liu Li Chen Li-Cai Deng Jin-Liang Hou Zheng-Yi Shao Fan Yang Yue Wu Ming Yang Yong Zhang Yong-Hui Hou Yue-Fei Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第8期1197-1208,共12页
In this work, we provide 2189 photometrically- and kinematically-selected candidate members of 24 star clusters from the LAMOST DR2 catalog. We perform two-step membership identification: selection along the stellar ... In this work, we provide 2189 photometrically- and kinematically-selected candidate members of 24 star clusters from the LAMOST DR2 catalog. We perform two-step membership identification: selection along the stellar track in the colormagnitude diagram, i.e., photometric identification, and selection from the distribution of radial velocities, i.e. the kinematic identification. We find that the radial velocities from the LAMOST data are very helpful in the membership identification. The mean probability of membership is 40% for the sample selected with radial velocity. With these 24 star clusters, we investigate the performance of the radial velocity and metallicity estimated with the LAMOST pipeline. We find that the systematic offsets in radial velocity and metallicity are 0.85 ± 1.26 km s-1and-0.08 ± 0.04 dex, with dispersions of 5.47+1.16-0.71 km s-1and 0.13+0.04-0.02 dex, respectively. Finally, we propose that the photometrically-selected candidate members of the clusters covered by the LAMOST footprint should be assigned higher priority so that more candidate stars can be observed. 展开更多
关键词 open clusters and associations: general—stars: statistics—catalogs—surveys—methods: data analysis
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Statistics of China Annual Oil-gas Production, Petroleum Drilling and Geophysical Survey
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《China Oil & Gas》 CAS 1997年第1期62-63,共2页
关键词 Petroleum Drilling and Geophysical survey statistics of China Annual Oil-gas Production
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Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China
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作者 Jun-jian Sun Jia-yue Shi +2 位作者 Qi Zhang Xiao-tao Shi Jun-jun Tan 《Water Science and Engineering》 EI CAS CSCD 2024年第1期83-91,共9页
To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse importa... To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China.Therefore,a vertical slot fishway(VSF)and a nature-like fishway(NLF)were built near the backwater area of the reservoir to connect the upstream and downstream habitats.Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways.The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species.During the survey,149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF,respectively,while 1263 fish from 27 species were found in the downstream area.Some species captured in the VSF were not found in the NLF,and vice versa,which implied the different preferences of fish.Meanwhile,3789 signals including 2099 upward ones and 1690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF.These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSFandNLF. 展开更多
关键词 Vertical slot fishway Nature-like fishway Aguatic ecological survey Fishwaymonitoring Statistical analysis
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Statistics of Chinese Oil-gas Production Petroleum Drilling and Geophysical Survey
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《China Oil & Gas》 CAS 1998年第1期61-61,共1页
关键词 statistics of Chinese Oil-gas Production Petroleum Drilling and Geophysical survey
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Statistics of Chinese Oil/Gas Production,Petroleum Drilling and Geophysical Survey
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《China Oil & Gas》 2000年第1期19-19,共1页
关键词 statistics of Chinese Oil/Gas Production Petroleum Drilling and Geophysical survey
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Survey on the Magnetic Structure of the Neutral Sheets in Earth's Magnetotail
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作者 XIAO Chao SHEN Chao +3 位作者 CHENG Guosheng ZHANG Hua ZHANG Ting CARR C M 《空间科学学报》 CAS CSCD 北大核心 2016年第6期837-848,共12页
Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is s... Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is selected to reveal the relation between y(GSM) and positional parameter z.The relation between y and magnetic field values indicates that the magnetic field is weak at midnight region and strengthens gradually at the duskside and dawnside.The relation between y and curvature radius is expressed by a quadratic function.And R_c of flattened CS is less than that of the normal CS.B_y determines the orientation of MFLs' configuration.The polar angle of the curvature vector is affected by the NS configuration.In addition,the correlation between the polar angle of the curvature vector and z is higher.The polar angle of the normal of the osculating plane is uncertain in the center area.The relation between the azimuthal angles of the curvature vector(the normal of the osculating plane) and y is negatively correlated.An empirical model applied to yz plane of the three-dimensional structure of the magnetic field lines in the NS are developed,and it is represented as a function of the positional parameter y.Finally,the current density is also statistically surveyed. 展开更多
关键词 Magnetic structure Statistical survey Neutral sheet Developing model
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Mapping the Milky Way with LAMOSTⅠ:method and overview 被引量:5
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作者 Chao Liu Yan Xu +8 位作者 Jun-Chen Wan Hai-Feng Wang Jeffrey L.Carlin Li-Cai Deng Heidi Jo Newberg Zi-Huang Cao Yong-Hui Hou Yue-Fei Wang Yong Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2017年第9期81-100,共20页
We present a statistical method to derive the stellar density profiles of the Milky Way from spectroscopic survey data, taking into account selection effects. We assume the selection function, which can be altered dur... We present a statistical method to derive the stellar density profiles of the Milky Way from spectroscopic survey data, taking into account selection effects. We assume the selection function, which can be altered during observations and data reductions, of the spectroscopic survey is based on photometric colors and magnitude. Then the underlying selection function for a line-of-sight can be recovered well by comparing the distribution of the spectroscopic stars in a color-magnitude plane with that of the photometric dataset. Subsequently, the stellar density profile along a line-of-sight can be derived from the spectroscopically measured stellar density profile multiplied by the selection function. The method is validated using Galaxia mock data with two different selection functions. We demonstrate that the derived stellar density profiles reconstruct the true ones well not only for the full set of targets, but also for sub-populations selected from the full dataset. Finally, the method is applied to map the density pro- files for the Galactic disk and halo, using the LAMOST RGB stars. The Galactic disk extends to about R = 19 kpc, where the disk still contributes about 10% to the total stellar surface density. Beyond this radius, the disk smoothly transitions to the halo without any truncation, bending or breaking. Moreover, no over-density corresponding to the Monoceros ring is found in the Galactic anti-center direction. The disk shows moderate north-south asymmetry at radii larger than 12 kpc. On the other hand, the R-Z tomographic map directly shows that the stellar halo is substantially oblate within a Galactocentric radius of 20 kpc and gradually becomes nearly spherical beyond 30 kpc. 展开更多
关键词 methods: statistical -- Galaxy structure -- Galaxy disk - Galaxy halo - surveys LAMOST
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Exploration of SDSS stellar database by AutoClass 被引量:1
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作者 YAN TaiSheng ZHANG YanXia +1 位作者 ZHAO YongHeng LI Ji 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2011年第9期1717-1726,共10页
AutoClass is an unsupervised Bayesian classification approach which seeks a maximum posterior probability classification for determining the optimal classes in large data sets. Using stellar photometric data from the ... AutoClass is an unsupervised Bayesian classification approach which seeks a maximum posterior probability classification for determining the optimal classes in large data sets. Using stellar photometric data from the Sloan Digital Sky Survey (SDSS) data release 7 (DR7), we utilize AutoClass to select non-stellar objects from this sample in order to build a pure stellar sample. For this purpose, the differences between PSF (point spread function) magnitudes and model magnitudes in five wavebands are taken as the input of AutoClass. Through clustering analysis of this sample by AutoClass, 617 non-stellar candidates are found. These candidates are identified by NED and SIMBAD databases. Most of the identified sources (13 from SIMBAD and 28 from NED respectively) are extragalactic sources (e.g., galaxies, HII, radio sources, infrared sources), some are peculiar stars (e.g., supernovas), and very few are normal stars. The extragalactic sources and peculiar stars of the identified objects occupy 94.1%. The result indicates that this method is an effective and robust clustering algorithm to find non-stellar objects and peculiar stars from the total stellar sample. 展开更多
关键词 data analysis statistical method CATALOGUES surveys STAR
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Automated estimation of stellar fundamental parameters from low resolution spectra: the PLS method 被引量:1
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作者 Jian-Nan Zhang A-Li Luo Yong-Heng Zhao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2009年第6期712-724,共13页
PLS (Partial Least Squares regression) is introduced into an automatic estimation of fundamental stellar spectral parameters. It extracts the most correlative spectral component to the parameters (Teff, log g and [... PLS (Partial Least Squares regression) is introduced into an automatic estimation of fundamental stellar spectral parameters. It extracts the most correlative spectral component to the parameters (Teff, log g and [Fe/H]), and sets up a linear regression function from spectra to the corresponding parameters. Considering the properties of stellar spectra and the PLS algorithm, we present a piecewise PLS regression method for estimation of stellar parameters, which is composed of one PLS model for Teff, and seven PLS models for log g and [Fe/H] estimation. Its performance is investigated by large experiments on flux calibrated spectra and continuum normalized spectra at different signal-to-noise ratios (SNRs) and resolutions. The results show that the piecewise PLS method is robust for spectra at the medium resolution of 0.23 nm. For low resolution 0.5 nm and 1 nm spectra, it achieves competitive results at higher SNR. Experiments using ELODIE spectra of 0.23 nm resolution illustrate that our piecewise PLS models trained with MILES spectra are efficient for O ~ G stars: for flux calibrated spectra, the systematic offsets are 3.8%, 0.14 dex, and -0.09 dex for Teff, log g and [Fe/H], with error scatters of 5.2%, 0.44 dex and 0.38 dex, respectively; for continuum normalized spectra, the systematic offsets are 3.8%, 0.12dex, and -0.13 dex for Teff, log g and [Fe/H], with error scatters of 5.2%, 0.49 dex and 0.41 dex, respectively. The PLS method is rapid, easy to use and does not rely as strongly on the tightness of a parameter grid of templates to reach high precision as Artificial Neural Networks or minimum distance methods do. 展开更多
关键词 METHODS data analysis -- methods statistical -- stars fundamental param- eters (classification temperatures metallicity) -- techniques spectroscopic -- surveys
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Investigation of Homogeneity and Matter Distribution on Large Scales Using Large Quasar Groups
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作者 李明华 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第12期758-772,共15页
We use 20 large quasar group(LQG) samples in Park et al.(2015) to investigate the homogeneity of the0.3 ≤z≤1.6 Universe(z denotes the redshift).For comparison,we also employ the 12 LQGs samples at 0.5 ≤z≤2in Kombe... We use 20 large quasar group(LQG) samples in Park et al.(2015) to investigate the homogeneity of the0.3 ≤z≤1.6 Universe(z denotes the redshift).For comparison,we also employ the 12 LQGs samples at 0.5 ≤z≤2in Komberg et al.(1996) to do the analysis.We calculate the bias factor b and the two-point correlation functionξ_(LQG) for such groups for three different density profiles of the LQG dark matter halos,i.e.the isothermal profile,the Navarro Frenk White(NFW) profile,and the(gravitational) lensing profile.We consider the ACDM(cold dark matter plus a cosmological constant A) underlying matter power spectrum with Ω_m = 0.28,Ω_∧= 0.72,the Hubble constant H_0 = 100 h·km·s^(-1)·Mpc^(-1) with h = 0.72.Dividing the samples into three redshift bins,we find that the LQGs with higher redshift are more biased and correlated than those with lower redshift.The homogeneity scale R_h of the LQG distribution is also deduced from theory.It is defined as the comoving radius of the sphere inside which the number of LQGs N(< r) is proportional to r^3 within 1%,or equivalently above which the correlation dimension of the sample D_2 is within 1%of D_2 = 3.For Park et al.'s samples and the NFW dark matter halo profile,the homogeneity scales of the LQG distribution are R_H■247 h^(-1)·Mpc for 0.2 < z ≤ 0.6,R_H■360 h^(-1)·Mpc for 0.6 < z ≤ 1.2,and R_H■480 h^(-1)·Mpc for 1.2 < z ■1.6.The maximum extent of the LQG samples are beyond Rh in each bin,showing that the LQG samples are not homogeneously distributed on such a scale,i.e.a length range of ~500 h^(-1) Mpc and a mass scale of ~10^(14)M⊙.The possibilities of a top-down structure formation process as was predicted by the hot/warm dark matter(WDM)scenarios and the redshift evolution of bias factor b and correlation amplitude ξ_(LQG) of the LQGs as a consequence of the cosmic expansion are both discussed.Different results were obtained based on the LQG sample in Komberg et al.(1996)and the possible reasons for such differences were discussed. 展开更多
关键词 surveys QUASARS statistics COSMOLOGY observations
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