Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the ...Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.展开更多
中国是世界上水土流失最为严重的国家之一。准确掌握既有水土流失研究的空间分布格局是一项基础性工作。以中国知网学术期刊数据库作为数据源,应用自然语言处理方法,对1980-2017年中国水土流失研究地区进行了地名信息提取及研究热点建模...中国是世界上水土流失最为严重的国家之一。准确掌握既有水土流失研究的空间分布格局是一项基础性工作。以中国知网学术期刊数据库作为数据源,应用自然语言处理方法,对1980-2017年中国水土流失研究地区进行了地名信息提取及研究热点建模;继而应用RUSLE模型模拟,得到全国土壤侵蚀强度的空间分布;在上述研究基础上,对研究热点地区与侵蚀强度之间的空间耦合关系进行了对比分析。结果表明:(1)1980年以来,中国水土流失研究热点区主要分布在黄土高原及贵州高原,涉及陕西、宁夏、内蒙古、甘肃、贵州以及黑龙江等省区;中等及以上热度的县(区、市)共171个,占全国国土总面积的5.33%。(2)RUSLE模型模拟表明,严重的土壤侵蚀主要分布在黄土高原及云贵高原,涉及陕西、宁夏、甘肃、山西、贵州、云南、四川等省区;侵蚀模数大于20 t hm-2 a-1的县(区、市)共251个,占全国国土总面积的7.04%。(3)研究热点地图与水土流失强度模型模拟地图之间存在空间差异。对特定空间耦合模式的分析有助于判断科研资源配置的合理性。展开更多
移动轨迹数据的热点区域挖掘在城市交通管理、道路规划和基于位置的服务中具有重要的作用。传统数据挖掘方法K-means、DBSCAN等算法,其参数选择困难、易影响聚类效果,针对在非凸数据集或密度不均匀、聚类间距差相差很大的数据集上聚类...移动轨迹数据的热点区域挖掘在城市交通管理、道路规划和基于位置的服务中具有重要的作用。传统数据挖掘方法K-means、DBSCAN等算法,其参数选择困难、易影响聚类效果,针对在非凸数据集或密度不均匀、聚类间距差相差很大的数据集上聚类表现较差等问题,提出了基于改进谱聚类的热点区域挖掘算法(hot region mining algorithm based on improved spectral clustering,ISCRM)。实验结果表明:对比传统方法,ISCRM算法优势在于自适应选取参数,避免人工调试参数环节,且其适用于任意形状的样本空间,聚类质量更高。可准确获得各个聚类中心,从而识别出用户出行热点区域。展开更多
The BeijingeTianjineHebei(BTH)region is the political center and one of the largest and most dynamic economic centers in China.Relative to other regions of China,it faces greater challenges from increasing hot extreme...The BeijingeTianjineHebei(BTH)region is the political center and one of the largest and most dynamic economic centers in China.Relative to other regions of China,it faces greater challenges from increasing hot extremes.However,future projections of regional changes in hot extremes based on multi-model ensembles carry huge uncertainty.To improve the reliability of regional projections,we used the latest highresolution outputs from nine GCMs in CMIP6-HighResMIP and constrained the projection of hot extremes in this region.In the BTH,the historical scaling of the annual maximum temperature with the mean summer(JuneeAugust)temperatures(TXx scaling)showed a significant linear relationship with the future TXx scaling in the multi-model ensemble.By comparing the observed and simulated historical TXx scaling we identified an observational constraint that could reduce the uncertainty of TXx scaling.We believed that the simulations of EC-Earth3P,ECEarth3P-HR,MPI-ESM1-2-HR and MPI-ESM1-2-XR show advantages in simulating surface air temperature and related hot extremes in this region.Verification demonstrated that surface air temperature projection in the BTH region constrained by observational constraint is more reliable.In constrained projections,by the 2040s,the increase in summer surface air temperatures is projected to exceed 1C compared to 2010s.Also,the estimated number of days of compound(sequential hot day-night)hot extremes(HND),independent hot nights(HNi)and independent hot days(HDi)was found to increase by 0.3,0.3,and-0.03 d per year during 2015-2049,respectively.The growth in numbers of days of HND,HNi and HDi was slower after observational constraint.Furthermore,the estimated increase in surface air temperature variables after constraint also reduced.This study provides support for adaptation policy-making and as a reference for the use of observational constraint in other regions of China.展开更多
The authors use a web crawler to retrieve all periodical articles from CNKI between the 1950 s and 2016 and then parse the abstracts of 293368 articles about grassland deterioration by word segmentation, location matc...The authors use a web crawler to retrieve all periodical articles from CNKI between the 1950 s and 2016 and then parse the abstracts of 293368 articles about grassland deterioration by word segmentation, location matching and other methods. The authors also construct a research hot regions extraction model of grassland deterioration in China based on a comprehensive research hot regions index of toponyms and then analyze the spatial pattern and dynamic change in research hot regions of grassland deterioration in China. The research shows the following：（1） The spatial heterogeneity of grassland deterioration in China can be effectively described by a model of grassland deterioration based on the comprehensive research hot regions index.（2） The research hot regions of grassland deterioration are mainly distributed in most regions of Inner Mongolia, Xinjiang, Qinghai, Tibet, Gansu and other provinces. The northeastern region of Inner Mongolia（such as Hulunbeier） and the eastern region of Inner Mongolia（such as Xilin Gol, Chifeng and Wulanchabu） are significant hot regions in the study of grassland deterioration.（3） The number of high research hot regions increases from 81 in the 1950 s to 99 in the 2000s; the area increases from 1.038 million km2 to 1.146 million km2. The degree of hot for grassland deterioration research in 197 counties showed an upward trend. This paper also discusses the relationship between the region of research hot regions and the region of grassland deterioration and then indicates the differences between them in time matching, space matching and concept matching.展开更多
基金Under the auspices of National Natural Science Foundation of China (No. 40901009)National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (No. 2008BAD98B02, 2006BAC01A11)+1 种基金the Western Light Program of Talents Cultivating of Chinese Academy of Sciences (2008)the Foundation of Key Laboratory of Mountain Hazards and Surface Process, Chinese Academy of Sciences
文摘Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.
文摘中国是世界上水土流失最为严重的国家之一。准确掌握既有水土流失研究的空间分布格局是一项基础性工作。以中国知网学术期刊数据库作为数据源,应用自然语言处理方法,对1980-2017年中国水土流失研究地区进行了地名信息提取及研究热点建模;继而应用RUSLE模型模拟,得到全国土壤侵蚀强度的空间分布;在上述研究基础上,对研究热点地区与侵蚀强度之间的空间耦合关系进行了对比分析。结果表明:(1)1980年以来,中国水土流失研究热点区主要分布在黄土高原及贵州高原,涉及陕西、宁夏、内蒙古、甘肃、贵州以及黑龙江等省区;中等及以上热度的县(区、市)共171个,占全国国土总面积的5.33%。(2)RUSLE模型模拟表明,严重的土壤侵蚀主要分布在黄土高原及云贵高原,涉及陕西、宁夏、甘肃、山西、贵州、云南、四川等省区;侵蚀模数大于20 t hm-2 a-1的县(区、市)共251个,占全国国土总面积的7.04%。(3)研究热点地图与水土流失强度模型模拟地图之间存在空间差异。对特定空间耦合模式的分析有助于判断科研资源配置的合理性。
文摘移动轨迹数据的热点区域挖掘在城市交通管理、道路规划和基于位置的服务中具有重要的作用。传统数据挖掘方法K-means、DBSCAN等算法,其参数选择困难、易影响聚类效果,针对在非凸数据集或密度不均匀、聚类间距差相差很大的数据集上聚类表现较差等问题,提出了基于改进谱聚类的热点区域挖掘算法(hot region mining algorithm based on improved spectral clustering,ISCRM)。实验结果表明:对比传统方法,ISCRM算法优势在于自适应选取参数,避免人工调试参数环节,且其适用于任意形状的样本空间,聚类质量更高。可准确获得各个聚类中心,从而识别出用户出行热点区域。
基金This work was supported by the National Natural Science Foundation of China(41905082).
文摘The BeijingeTianjineHebei(BTH)region is the political center and one of the largest and most dynamic economic centers in China.Relative to other regions of China,it faces greater challenges from increasing hot extremes.However,future projections of regional changes in hot extremes based on multi-model ensembles carry huge uncertainty.To improve the reliability of regional projections,we used the latest highresolution outputs from nine GCMs in CMIP6-HighResMIP and constrained the projection of hot extremes in this region.In the BTH,the historical scaling of the annual maximum temperature with the mean summer(JuneeAugust)temperatures(TXx scaling)showed a significant linear relationship with the future TXx scaling in the multi-model ensemble.By comparing the observed and simulated historical TXx scaling we identified an observational constraint that could reduce the uncertainty of TXx scaling.We believed that the simulations of EC-Earth3P,ECEarth3P-HR,MPI-ESM1-2-HR and MPI-ESM1-2-XR show advantages in simulating surface air temperature and related hot extremes in this region.Verification demonstrated that surface air temperature projection in the BTH region constrained by observational constraint is more reliable.In constrained projections,by the 2040s,the increase in summer surface air temperatures is projected to exceed 1C compared to 2010s.Also,the estimated number of days of compound(sequential hot day-night)hot extremes(HND),independent hot nights(HNi)and independent hot days(HDi)was found to increase by 0.3,0.3,and-0.03 d per year during 2015-2049,respectively.The growth in numbers of days of HND,HNi and HDi was slower after observational constraint.Furthermore,the estimated increase in surface air temperature variables after constraint also reduced.This study provides support for adaptation policy-making and as a reference for the use of observational constraint in other regions of China.
基金National Key Research and Development Plan Program(2016YFC0503701,2016YFB0501502)Key Project of High Resolution Earth Observation System(00-Y30B14-9001-14/16)
文摘The authors use a web crawler to retrieve all periodical articles from CNKI between the 1950 s and 2016 and then parse the abstracts of 293368 articles about grassland deterioration by word segmentation, location matching and other methods. The authors also construct a research hot regions extraction model of grassland deterioration in China based on a comprehensive research hot regions index of toponyms and then analyze the spatial pattern and dynamic change in research hot regions of grassland deterioration in China. The research shows the following：（1） The spatial heterogeneity of grassland deterioration in China can be effectively described by a model of grassland deterioration based on the comprehensive research hot regions index.（2） The research hot regions of grassland deterioration are mainly distributed in most regions of Inner Mongolia, Xinjiang, Qinghai, Tibet, Gansu and other provinces. The northeastern region of Inner Mongolia（such as Hulunbeier） and the eastern region of Inner Mongolia（such as Xilin Gol, Chifeng and Wulanchabu） are significant hot regions in the study of grassland deterioration.（3） The number of high research hot regions increases from 81 in the 1950 s to 99 in the 2000s; the area increases from 1.038 million km2 to 1.146 million km2. The degree of hot for grassland deterioration research in 197 counties showed an upward trend. This paper also discusses the relationship between the region of research hot regions and the region of grassland deterioration and then indicates the differences between them in time matching, space matching and concept matching.
