Spatial objects have two types of attributes： geometrical attributes and non-geometrical attributes, which belong to two different attribute domains （geometrical and non-geometrical domains）. Although geometrically...Spatial objects have two types of attributes： geometrical attributes and non-geometrical attributes, which belong to two different attribute domains （geometrical and non-geometrical domains）. Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clustering： local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted clustering is obtained based on those features fective and efficient. Second, local features from each site are sent to a central site where global Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.展开更多
With the deepening informationization of Resources & Environment Remote Sensing geological survey conducted,some potential problems and deficiency are:(1) shortage of unified-planed running environment;(2) inconsi...With the deepening informationization of Resources & Environment Remote Sensing geological survey conducted,some potential problems and deficiency are:(1) shortage of unified-planed running environment;(2) inconsistent methods of data integration;and(3) disadvantages of different performing ways of data integration.This paper solves the above problems through overall planning and design,constructs unified running environment, consistent methods of data integration and system structure in order to advance the informationization展开更多
Digital Orthographic Map (DOM) can be used in various applications because it contains both image features and terrain information. Spatial database management systems aim at the effective and efficient management of ...Digital Orthographic Map (DOM) can be used in various applications because it contains both image features and terrain information. Spatial database management systems aim at the effective and efficient management of data related to a space, engineering design and so on. Thereby spatial database provides an efficient solution for managing DOM. According to large amounts of the DOM data in storage, a data compression based on wavelet is introduced into the storage. Another strategy to solve this problem is to decompose the raw image into tiles and store the tiles individually as separate tuples. The metadata of DOM can be used to organize and manage spatial information, especially for spatial data sharing and fast locating. A tool for browsing, zooming and querying the DOM data is also designed. We implemented these ideas in SISP(Spatial Information Sharing System) and applied the subsystem into the DOM management of Beijing City, which is an component of the Beijing Spatial Information Infrastructure.展开更多
This study systematically evaluated the spatial distribution,health risks,and regulation of per-and polyfluoroalkyl substances(PFAS)in global drinking water using the PubMed and Web of Science databases(January 1,2000...This study systematically evaluated the spatial distribution,health risks,and regulation of per-and polyfluoroalkyl substances(PFAS)in global drinking water using the PubMed and Web of Science databases(January 1,2000 to February 25,2025).Among the 122 studies reviewed,perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS)received the greatest research attention(detected in 102 and 100 studies,respectively)and showed the highest detection rates(64.69%and 60.72%,respectively).Several other compounds,including perfluorooctane sulfonamide,perfluorobutanesulfonamide,and perfluoropropane sulfonate,also exhibited high detection rates but remain underregulated,underscoring the need for further research and regulatory oversight.The three countries with the highest concentrations of were the Republic of Korea,the United States,and China.Risk assessments indicated that perfluorohexanoic acid,perfluorobutanoic acid,and perfluorobutanesulfonic acid posed negligible health risks,while perfluorohexane sulfonic acid(PFHxS),PFOA,PFOS,and perfluorononanoic acid(PFNA)showed descending levels of health risk(PFHxS>PFOA>PFOS>PFNA).Regulatory approaches are shifting from compound-specific standards to integrated mixture-based frameworks,reinforced by progressively stringent limits.展开更多
基于关系型数据库的空间数据存储与处理是地理信息系统(geographic information system,GIS)领域的主流模式,但伴随着物联网、移动互联网、云计算及空间数据采集技术的发展,空间数据已从海量特征转变为大数据特征,对空间数据的存储和管...基于关系型数据库的空间数据存储与处理是地理信息系统(geographic information system,GIS)领域的主流模式,但伴随着物联网、移动互联网、云计算及空间数据采集技术的发展,空间数据已从海量特征转变为大数据特征,对空间数据的存储和管理在数据量和处理模式上提出了新的挑战。首先分析了基于传统的集中式存储与管理模式在处理和应用大数据方面的局限性,包括存储对象的适应性、存储能力的可扩展性及高并发处理能力要求;然后在分析当前几大主流NoSQL数据库特点的基础上,指出了空间大数据基于NoSQL数据库的单一存储模式在数据操作方式、查询方式和数据高效管理方面存在的局限性;最后结合GIS领域空间大数据存储对数据库存储能力的可扩展性及数据处理和访问的高并发要求,提出基于内存数据库和NoSQL数据库的空间大数据分布式存储与综合处理策略,并开发了原型系统对提出的存储策略进行可行性和有效性进行了验证。展开更多
基金Funded by the National 973 Program of China (No.2003CB415205)the National Natural Science Foundation of China (No.40523005, No.60573183, No.60373019)the Open Research Fund Program of LIESMARS (No.WKL(04)0303).
文摘Spatial objects have two types of attributes： geometrical attributes and non-geometrical attributes, which belong to two different attribute domains （geometrical and non-geometrical domains）. Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clustering： local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted clustering is obtained based on those features fective and efficient. Second, local features from each site are sent to a central site where global Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.
文摘With the deepening informationization of Resources & Environment Remote Sensing geological survey conducted,some potential problems and deficiency are:(1) shortage of unified-planed running environment;(2) inconsistent methods of data integration;and(3) disadvantages of different performing ways of data integration.This paper solves the above problems through overall planning and design,constructs unified running environment, consistent methods of data integration and system structure in order to advance the informationization
基金This work is supported by the National High Technology Research and Development Program ofChina(2 0 0 2 AA135 2 30 ) and the Major Project of National Natural Science Foundation of Beijing(4 0 110 0 2 )
文摘Digital Orthographic Map (DOM) can be used in various applications because it contains both image features and terrain information. Spatial database management systems aim at the effective and efficient management of data related to a space, engineering design and so on. Thereby spatial database provides an efficient solution for managing DOM. According to large amounts of the DOM data in storage, a data compression based on wavelet is introduced into the storage. Another strategy to solve this problem is to decompose the raw image into tiles and store the tiles individually as separate tuples. The metadata of DOM can be used to organize and manage spatial information, especially for spatial data sharing and fast locating. A tool for browsing, zooming and querying the DOM data is also designed. We implemented these ideas in SISP(Spatial Information Sharing System) and applied the subsystem into the DOM management of Beijing City, which is an component of the Beijing Spatial Information Infrastructure.
基金supported by the School of Public Health,Shanxi Medical University“233”Cooperation Project(No.2024002 to Y.W.)the Medical Scientific Research Project Plan of Hebei Province(No.20260935 to J.M.).
文摘This study systematically evaluated the spatial distribution,health risks,and regulation of per-and polyfluoroalkyl substances(PFAS)in global drinking water using the PubMed and Web of Science databases(January 1,2000 to February 25,2025).Among the 122 studies reviewed,perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS)received the greatest research attention(detected in 102 and 100 studies,respectively)and showed the highest detection rates(64.69%and 60.72%,respectively).Several other compounds,including perfluorooctane sulfonamide,perfluorobutanesulfonamide,and perfluoropropane sulfonate,also exhibited high detection rates but remain underregulated,underscoring the need for further research and regulatory oversight.The three countries with the highest concentrations of were the Republic of Korea,the United States,and China.Risk assessments indicated that perfluorohexanoic acid,perfluorobutanoic acid,and perfluorobutanesulfonic acid posed negligible health risks,while perfluorohexane sulfonic acid(PFHxS),PFOA,PFOS,and perfluorononanoic acid(PFNA)showed descending levels of health risk(PFHxS>PFOA>PFOS>PFNA).Regulatory approaches are shifting from compound-specific standards to integrated mixture-based frameworks,reinforced by progressively stringent limits.
文摘基于关系型数据库的空间数据存储与处理是地理信息系统(geographic information system,GIS)领域的主流模式,但伴随着物联网、移动互联网、云计算及空间数据采集技术的发展,空间数据已从海量特征转变为大数据特征,对空间数据的存储和管理在数据量和处理模式上提出了新的挑战。首先分析了基于传统的集中式存储与管理模式在处理和应用大数据方面的局限性,包括存储对象的适应性、存储能力的可扩展性及高并发处理能力要求;然后在分析当前几大主流NoSQL数据库特点的基础上,指出了空间大数据基于NoSQL数据库的单一存储模式在数据操作方式、查询方式和数据高效管理方面存在的局限性;最后结合GIS领域空间大数据存储对数据库存储能力的可扩展性及数据处理和访问的高并发要求,提出基于内存数据库和NoSQL数据库的空间大数据分布式存储与综合处理策略,并开发了原型系统对提出的存储策略进行可行性和有效性进行了验证。
