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Search Results: 1 - 10 of 87027 matches for " XU Cheng-dong "
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Flora transitiona and its biogeographical significance
植物区系过渡性及其生物地理意义

FENG Jian-meng,XU Cheng-dong,
冯建孟
,徐成东

生态学杂志 , 2009,
Abstract: 利用野外考察和文献记载资料,结合气候数据,探讨了植物区系过渡性的生物地理意义及其与年平均温度之间的联系,并将区系过渡性的生物地理意义应用于中国东部地区植被的分区。结果表明: 海拔与纬度均与Ttrop/Ttemp(热带区系成分与温带区系成分所占比重之比值)呈明显的负相关关系。区系过渡性可以通过其与纬度、海拔的回归方程进行估算;当区系过渡性为恒值时,出现恒定值的海拔高度,随着纬度的升高呈单调递降格局;区系过渡性随着温度的升高,先增强后减弱,呈偏峰分布格局。通过对区系过渡性与年平均温度之间联系的抛物线方程式的分析,中国东部地区热带雨林北缘与南亚热带季风常绿阔叶林、北亚热带常绿落叶阔叶混交林与暖温带落叶阔叶林、中温带落叶阔叶针叶混交林与北温带针叶林之间的分界线分别在21.5°N以南、34°N—35°N和47.5°N以北,年平均温度分别在23.40 ℃、12.45 ℃和1.51 ℃。这与过去的相关研究比较一致,并为中国东部地区植物区系的变化以及植被地理分布的研究, 提供了一种新的思路和方法。
Geographical distribution patterns of zonal plant community species diversity in West Yunnan, China
云南西部地区地带性植物群落物种多样性的地理分布格局

FENG Jian-meng,XU Cheng-dong,
冯建孟
,徐成东

生态学杂志 , 2009,
Abstract: 利用样方数据和文献资料,探讨了云南西部地区地带性植物群落的物种多样性。结果表明:在纬度梯度上,从南到北,物种密度呈递减趋势;在海拔梯度上,从高海拔到低海拔,物种密度呈递增趋势;在经度梯度上,从东到西,物种密度呈递减格局。总体上,在群落尺度上,南部地区物种密度较高;北部地区,即滇西北地区物种密度相对较低,这可能与研究区域内热量和水分条件的空间分异有关,但热量因子可能扮演着更为重要的角色。海拔梯度上的物种变化速率远高于经度梯度和纬度梯度,这可能与海拔梯度上热量条件的变化速率远高于其他地理梯度有关。区域尺度上单位面积物种多样性的分布格局与群落尺度明显不同,这可能源于群落尺度上单位面积的物种多样性主要受制于能量水平;但在区域尺度上,单位面积的物种多样性可能与区域内的生境异质性有关。表明“尺度效应”在塑造物种多样性地理分布格局中的重要作用。
The Ecological Phytogeography of Pteridophytes in Ailaoshan Mountain National Nature Reserve, Yunnan, China
云南哀牢山国家级自然保护区蕨类植物生态地理研究

XU Cheng-Dong,LU Shu-Gang,
徐成东
,陆树刚

植物科学学报 , 2007,
Abstract: The floristic phytogeography of pteridophytes of 446 species(including varieties and forms) and 118 genera in 48 families were recorded from this region up to now.This paper discussed the pteridophytic ecology of Ailaoshan Mountain National Nature Reserve from uprightness distribution,east and west distribution and ecological types,and the conclusions were as follows:(1)The pteridophytic ecological types are affinitive with different vegetations.There are the most abundant peteridopytes in vegetations of the wet evergreen broad-leaved forest on upper slopes and the mossy dwarf forest on mountain tops among 2000-2800 m,furthermore,the epiphytes accounted for 28.5% in total species of this area.(2)There are 387 and 355 species of pteridophytes from east and west slope,moreover,295 are mutual species between two slopes;(3)The pteridophytic ecological types from Ailaoshan Mountain National Nature Reserve can be divided into 16 types according to the effects of ecological factors.The ecological features are characterized by:diversified ecological types,rich species of sciophytes,submegatherms and mesophytes,high proportions species of epiphytes,lower proportions species of mesotherms and submesotherms,xerophytes and lithophytes.
Altitudinal Patterns of Seed Plants Floristic Composition in Mountain Yao Nature Reserve, Yunnan Province, China
云南药山自然保护区种子植物区系的垂直分布格局

FENG Jian-Meng,XU Cheng-Dong,
冯建孟
,徐成东

植物科学学报 , 2008,
Abstract: 通过野外植被调查,结合文献资料,探讨了云南药山自然保护区种子植物区系的垂直分布格局.结果表明,温带区系成分所占比重,随着海拔的升高,总体上呈单调递增趋势,而热带区系成分所占比重呈单调递减格局;区系平衡点出现在海拔2000 m 左右.在平衡点之下,植物区系以热带、亚热带区系成分为主,而在此之上,则以温带区系成分为主.区系成分的聚类分析表明,研究区域内植被垂直带谱主要由1500 m以下的干热河谷植被、1500~2000 m左右的云南松林、2000~2600 m的常绿阔叶林、2600~3100 m的硬叶常绿阔叶林、3100~3600 m的亚高山灌丛和3600 m以上的高寒草甸构成,这与传统的植被类型划分方法的结果基本一致.
Estimation of Citywide Air Pollution in Beijing
Jin-Feng Wang, Mao-Gui Hu, Cheng-Dong Xu, George Christakos, Yu Zhao
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053400
Abstract: There has been discrepancies between the daily air quality reports of the Beijing municipal government, observations recorded at the U.S. Embassy in Beijing, and Beijing residents’ perceptions of air quality. This study estimates Beijing’s daily area PM2.5 mass concentration by means of a novel technique SPA (Single Point Areal Estimation) that uses data from the single PM2.5 observation station of the U.S Embassy and the 18 PM10 observation stations of the Beijing Municipal Environmental Protection Bureau. The proposed technique accounts for empirical relationships between different types of observations, and generates best linear unbiased pollution estimates (in a statistical sense). The technique extends the daily PM2.5 mass concentrations obtained at a single station (U.S. Embassy) to a citywide scale using physical relations between pollutant concentrations at the embassy PM2.5 monitoring station and at the 18 official PM10 stations that are evenly distributed across the city. Insight about the technique’s spatial estimation accuracy (uncertainty) is gained by means of theoretical considerations and numerical validations involving real data. The technique was used to study citywide PM2.5 pollution during the 423-day period of interest (May 10, 2010 to December 6, 2011). Finally, a freely downloadable software library is provided that performs all relevant calculations of pollution estimation.
Application of Neural Network and Genetic Algorithm in Dynamic Route Guidance
神经网络和遗传算法在动态路径诱导中的应用*

WU Cheng-dong,YANG Li-ying,XU Ke,
吴成东
,杨丽英,许可

计算机应用研究 , 2006,
Abstract: In order to solve the problem of bad real-time and seeking answer ineffectively,which exist in route guidance of intelligent traffic system,a dynamic route guidance method based on Neural Network(NN) and Genetic Algorithm(GA) is presented.The NN forecasting method for traffic information has been studied deeply and the time-varied road weight has composed to matrixes,which solve the limitation problem in traditional static road weight.The GA for optimal route choice is discussed,the corresponding selection,crossover and mutation operators are given.The quality and the efficient of seeking the answer have been balanced.It is indicated by simulation that the presenting method of route guidance has achieve the right, real-time and quick guidance.
Spatial Patterns of Floristic Composition of Invasive Alien Plants in Large Scale and Their Climatic Interpretation
中国外来入侵植物区系组成的大尺度格局及其气候解释

FENG Jian-Meng,DONG Xiao-Dong,XU Cheng-Dong,
冯建孟
,董晓东,徐成东

植物科学学报 , 2009,
Abstract: 外来入侵物种的空间分布格局及其影响因子的研究是外来物种管理和控制的基础.本研究利用文献数据和气候资料,探讨了中国外来入侵植物(属)区系组成的大尺度格局及其与气候因子之间的联系.从植物区系的总体构成来看,热带区系成分所占比重较大,其次为温带成分和世界分布成分,说明研究区域内外来入侵植物主要起源于热带地区,其次为温带地区.从空间格局来看,从南到北,热带区系成分所占比重呈递减趋势,而温带区系成分所占比重则呈递增趋势.这说明,在南部区域,外来入侵植物更多的来自于热带地区,但在北部区域,来自于温带地区的外来入侵植物可能占据主导地位.热量水平显著影响外来入侵植物的空间格局,随着热量水平的提高,热带区系比重呈递增趋势,而温带区系成分所占比重则呈递减趋势,这可能与不同区系成分植物的生态特性有关.
The Spatial Patterns of Species Diversity of Seed Plants and Its Differentiation in Yunnan, China
云南地区种子植物多样性分布格局和多样性分化特点研究

FENG Jian-meng,XU Cheng-dong,DONG Xiao-dong,
冯建孟
,徐成东,董晓东

热带亚热带植物学报 , 2010,
Abstract: The spatial patterns and differentiation of species diversity of seed plants in Yunnan, China, were investigated based on distribution datasets of plant species at large scale, geographical information system and statistic methods. The results indicated that the discreteness of datasets of plant diversity and flora differentiation increased from families to genera and species. Compared with genera and species, the spatial variation and diversity centers of families were not obvious, which may be due to different historical periods in geology reflected by families, genera and species. The diversities of genera and species in southern Yunnan were richer than those of other areas except northwest Yunnan. The diversity centers of species were mainly observed in northwest Yunnnan, southern Yunnan, regions of Ailao Mountain, Wuliang Mountain, and Kunming region, which may be related to the geographical patterns of habitat heterogeneity and energy. Compared with families, the spatial variation of genera differentiation was more easily observed and showed similar patterns with species diversity, indicating significant correlation between plant diversity and flora differentiation. Compared with families, the centers of genera differentiation were obvious. On the whole, the spatial patterns of species diversity of seed plants and its differentiation were jointly shaped by habitat heterogeneity, energy and geological history.
Moving object detection and tracking based on geodesic active contour model
采用测地线活动轮廓模型检测与跟踪运动目标

XU Yang,WU Cheng-dong,CHEN Dong-yue,ZHAO Ji,WANG Li,
徐杨
,吴成东,陈东岳,赵骥,王力

控制理论与应用 , 2012,
Abstract: The geometric-active contour model based on the level set can better handle the variations of the curve topology. In order to track a rigid or non-rigid moving object and extract its contour information, we propose a combination method of the improved geodesic active contour (GAC) model and Kalman filter. In this method, the moving regions of the object are determined by using Gaussian mixture model and the background difference method; the GAC model with a distance regularization term is used to perform the curve evolution in the moving region, making the evolving curve approaching to the true contours of the object. The tracking of the moving object is realized by using Kalman filter to predict the object position of the next frame. Experimental results show that the proposed method is applicable to both rigid and non-rigid objects, achieving good detection and tracking effect even in the case of partial occlusion.
Problems and Reform of Administrative Law of the Private Sector
民营经济的行政法问题及其改革

JIN Cheng-dong,
金承东

浙江大学学报(人文社会科学版) , 2006,
Abstract: 2004年修宪后,中国民营经济面临的行政法问题及其改革方案可概述为:第一,针对我国长期以来公私财产区别保护的问题,行政主体应牢固树立私有财产也神圣的理念,并重点规范其征收征用行为;第二,针对所有制的歧视问题,行政主体必须牢固树立各种所有制平等理念,并在市场准入、财税金融支持等方面对民营经济采取鼓励措施;第三,针对行业协会严重行政化的问题,为给民营经济创造良好的市民社会基础,我们要在行业协会的性质定位、社会资源配置方式和社会文化的养成等方面进行改革;第四,针对民营经济中社会保障不充分的问题,行政主体应将民营经济成员的社会保险工作作为今后社会保障工作的重点,并使其更具有可操作性。
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