基于2003—2019年GRACE陆地水储量变化数据和全球陆地水文模型(global land data assimilation system,GLDAS)数据反演京津冀地下水储量变化,运用时空分析方法对地下水等效水高变化进行时空演变特征分析。在空间变化上,整个京津冀地下...基于2003—2019年GRACE陆地水储量变化数据和全球陆地水文模型(global land data assimilation system,GLDAS)数据反演京津冀地下水储量变化,运用时空分析方法对地下水等效水高变化进行时空演变特征分析。在空间变化上,整个京津冀地下水等效水高变化速率约为-51.77 mm/a,其中:北京市变化速率最低,约为-38.15 mm/a;天津市变化速率最高,约为-62.85 mm/a;河北省变化速率与区域平均变化水平相当,约为-52.42 mm/a。基于Sen Slope和Mann-Kendall非参数检验法分析得出西部、西南部和中部地区地下水等效水高下降趋势最明显,东北部下降趋势最小。在时间变化上,地下水等效水高变化具有一定的季节性规律:夏季变化速率最大,约为-75.99 mm/a;冬季变化速率最小,约为-37.24 mm/a;春秋两季的变化速率大致相同,分别为-52.34 mm/a和-48.21 mm/a。在影响因素分析中,人类活动是引起京津冀地区地下水等效水高变化的主要因素。研究结果可为科学掌握京津冀地下水储量时空变化规律提供数据支撑。展开更多
Cities are the key areas for human beings to achieve sustainable development goals in the future.Estuarine cities are a special type of coastal city in urgent need of a clear definition.This paper proposed that estuar...Cities are the key areas for human beings to achieve sustainable development goals in the future.Estuarine cities are a special type of coastal city in urgent need of a clear definition.This paper proposed that estuarine cities are cities developed on the coast where rivers and oceans meet and defined four connotations,including the intersection of rivers and marine water systems,the coordinated development of land and oceans,the location advantages of connecting rivers and seas,and the important fragility of the ecological environment.We used Hydro SHEDS,OSM,GPW,and urban socioeconomic statistics and selected 50 estuarine cities with large rivers as representatives to summarize the main geographical basis and socioeconomic characteristics.Cities are primarily found in low-altitude,flat regions with average annual temperatures that mainly vary from 10℃to 25℃,relatively abundant precipitation,and extensive biological resources.There are substantial variations in the socioeconomic features of estuarine cities.We proposed eight development patterns,including open and inclusive city spirit,high-quality livable cities,high-quality development driven by innovation,integration of internal and external communication with ports and cities,construction of an international financial center,ecological environment protection and restoration,active promotion of cultural tourism,and positive international exchanges.展开更多
无人机高光谱遥感是低成本、高精度获取精细尺度农作物生物物理参数和生物化学参数的新型手段,以此快速反演叶面积指数(Leaf Area Index,LAI)对作物长势评价、产量预测具有重要意义。以山东禹城市玉米为研究对象,利用PROSAIL辐射传输模...无人机高光谱遥感是低成本、高精度获取精细尺度农作物生物物理参数和生物化学参数的新型手段,以此快速反演叶面积指数(Leaf Area Index,LAI)对作物长势评价、产量预测具有重要意义。以山东禹城市玉米为研究对象,利用PROSAIL辐射传输模型模拟玉米冠层反射率获取LAI特征响应波段结合相关性定量分析获取对LAI变化最为敏感的波段,并以此计算6种植被指数(Vegetation Index,VI),利用6种回归模型分别对单一特征波段和VI进行反演建模,以实测LAI评定模型精度。研究表明,光谱反射率中516、636、702、760和867 nm等波段对LAI变化最为敏感,以此建立的单一特征波段反演模型预测LAI精度R^2为0.44~0.58;RMSE为0.16~0.18,其中636 nm建立的模型(LAI=21.86exp(-29.47R636))相比其他反演模型预测精度较高(R^2=0.58,RMSE=0.16);6种植被指数与LAI高度相关,相关性系数R2为0.85~0.86,以此建立的反演模型相比单一特征波段反演模型精度有所提高,R^2为0.66~0.72,RMSE为0.12~0.14;其中mNDVI构建的LAI估算模型(LAI=exp(2.76~1.77/mNDVI))精度最高(R^2=0.72,RMSE=0.13)。无人机高光谱遥感是快速、无损监测农作物生长信息的有效手段,为指导精细化尺度作物管理提供依据。展开更多
The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study...The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study the problem in a serial environment. However, in GIS, a spatial object is much more complicated and is considered to be always composed of multiple line segments, and one line segment connects another line segment at its endpoint. On the other hand, along with the advances made in computer hardware, more and more personal computers have multiple cores or CPUs equipped. Thus, to make full use of the increasing computing resources, parallel technique is applied as one of the most available methods. Apparently, the traditional algorithms should be improved to take advantage of the technologies. Under these circumstances, based on the modified uniform grid algorithm, which is adapted to dealing with spatial objects in GIS, this paper proposes a parallel strategy in a shared memory architecture. Also, experimental results are given in the final part of this paper to demonstrate the efficiency this strategy brings.展开更多
基金The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA23100301The Chinese Academy of Sciences Basic Frontier Science Research Program from 0 to 1 Original Innovation Project,No.ZDBS-LYD-QC005National Natural Science Foundation of China,No.42171204。
文摘Cities are the key areas for human beings to achieve sustainable development goals in the future.Estuarine cities are a special type of coastal city in urgent need of a clear definition.This paper proposed that estuarine cities are cities developed on the coast where rivers and oceans meet and defined four connotations,including the intersection of rivers and marine water systems,the coordinated development of land and oceans,the location advantages of connecting rivers and seas,and the important fragility of the ecological environment.We used Hydro SHEDS,OSM,GPW,and urban socioeconomic statistics and selected 50 estuarine cities with large rivers as representatives to summarize the main geographical basis and socioeconomic characteristics.Cities are primarily found in low-altitude,flat regions with average annual temperatures that mainly vary from 10℃to 25℃,relatively abundant precipitation,and extensive biological resources.There are substantial variations in the socioeconomic features of estuarine cities.We proposed eight development patterns,including open and inclusive city spirit,high-quality livable cities,high-quality development driven by innovation,integration of internal and external communication with ports and cities,construction of an international financial center,ecological environment protection and restoration,active promotion of cultural tourism,and positive international exchanges.
文摘The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study the problem in a serial environment. However, in GIS, a spatial object is much more complicated and is considered to be always composed of multiple line segments, and one line segment connects another line segment at its endpoint. On the other hand, along with the advances made in computer hardware, more and more personal computers have multiple cores or CPUs equipped. Thus, to make full use of the increasing computing resources, parallel technique is applied as one of the most available methods. Apparently, the traditional algorithms should be improved to take advantage of the technologies. Under these circumstances, based on the modified uniform grid algorithm, which is adapted to dealing with spatial objects in GIS, this paper proposes a parallel strategy in a shared memory architecture. Also, experimental results are given in the final part of this paper to demonstrate the efficiency this strategy brings.
