本文采用文献计量方法,以科学知识图谱为工具,对"Web of Science核心合集"(2007-2017)中与STEM教育研究相关的1016篇文献进行回顾总结。结果显示:时间分布上,STEM教育经历了初步探索期、快速发展期和深化研究期三个阶段;空间...本文采用文献计量方法,以科学知识图谱为工具,对"Web of Science核心合集"(2007-2017)中与STEM教育研究相关的1016篇文献进行回顾总结。结果显示:时间分布上,STEM教育经历了初步探索期、快速发展期和深化研究期三个阶段;空间分布上,美国是STEM教育的发源地且引领该领域的发展热潮,有关此领域的研究机构多集中在大学,研究作者集中在教育领域;研究热点上,基于学业表现、人才培养、课程设计等领域的研究热度始终不减。未来,STEM教育研究体现出更加重视构建完善的STEM教育体系及学习生态系统,重视整合学习和不断扩大STEM教育的学科融合等发展趋势。展开更多
Desertification research plays a key role in the survival and development of all mankind.The Normalized Comprehensive Hotspots Index(NCH)is a comprehensive index that reveals the spatial distribution of research hotsp...Desertification research plays a key role in the survival and development of all mankind.The Normalized Comprehensive Hotspots Index(NCH)is a comprehensive index that reveals the spatial distribution of research hotspots in a given research field based on the number of relevant scientific papers.This study uses Web Crawler technology to retrieve the full text of all Chinese journal articles spanning the 1980s-2018 in the Chinese Academic Journal full-text database(CAJ)from CNKI.Based on the 253,055 articles on desertification that were retrieved,we have constructed a research hotspot extraction model for desertification in China by means of the NCH Index.This model can reveal the spatial distribution and dynamic changes of research hotspots for desertification in China.This analysis shows the following:1)The spatial distribution of research hotspots on desertification in China can be effectively described by the NCH Index,although its application in other fields still needs to be verified and optimized.2)According to the NCH Index,the research hotspots for desertification are mainly distributed in the Agro-Pastoral Ecotone and grassland in Inner Mongolia,the desertification areas of Qaidam Basin in the Western Alpine Zone and the Oasis-Desert Ecotone in Xinjiang(including the extension of the central Tarim Basin to the foothills of the Kunlun Mountains,the sporadic areas around the Tianshan Mountains and the former hilly belt of the southern foothills of the Altai Mountains).Among these three,the Agro-Pastoral Ecotone in the middle and eastern part of Inner Mongolia includes the most prominent hotspots in the study of desertification.3)Since the 1980s,the research hotspots for desertification in China have shown a general downward trend,with a significant decline in 219 counties(10.37%of the study area).This trend is dominated by the projects carried out since 2002.The governance of desertification in the eastern part of the Inner Mongolia-Greater Khingan Range still needs to be strengthened.The distribution of d展开更多
全球创新网络是在科技创新全球化过程中围绕产业创新发展而形成的全球范围内创新主体、创新要素、创新制度之间建立起各类正式和非正式的跨国关系的总体结构。本文针对全球创新网络及相关研究主题,以Web of Science核心合集为数据来源,...全球创新网络是在科技创新全球化过程中围绕产业创新发展而形成的全球范围内创新主体、创新要素、创新制度之间建立起各类正式和非正式的跨国关系的总体结构。本文针对全球创新网络及相关研究主题,以Web of Science核心合集为数据来源,采用社会网络和可视化方法,刻画分析了全球创新网络研究热点、学科及空间分布网络特征;并通过构建活力指标和吸引力指标,评估了主要国家在该领域的研究潜力,包括自身研究的活跃度和在网络中的吸引力。结果表明,全球创新网络研究领域中新兴市场、创新政策等主题正在成为研究热点;该领域的研究主要受到商业与经济交叉相关学科领域学者的关注,其次是地理相关学科;欧美地区的研究工作较多,亚洲新兴经济体也做出了重要贡献。美、德、中、英四国为该领域的主要研究国家,在不同时期其研究潜力和优势领域不同,美国和德国研究实力较强并具有借鉴式合作潜力,中国和英国正在成为重要的研究节点国家并具有开创式合作潜力。展开更多
The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyz...The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyzed based on the risk assessment model of hotspot constructed in this paper.Firstly,approaches for monitoring of the aerodrome movement were compared.The hotspot recognition algorithm taken into account of whether aircrafts'taxi track has spatial and temporal overlap based on the aerodrome surveillance radar(ASR)data was presented,by identifying the hotspots through analyzing whether the aircrafts'time of entering and exiting the same taxiway is overlap or not,and the heading difference and distance of the two aircrafts satisfy the specified threshold constraint condition.Then,the ASR data were divided into several parts,and then airport hotspots were recognized and the spatial and temporal distribution characteristics were analyzed.The risk assessment model of airport safety hotspots was constructed which is taken into account of the conflict probability and its severity consequence.Finally,based on the risk grade assessment criteria and hotspots'risk value,the risk grade ranking of hotspot in one airport of China was evaluated and designated.According to the result,the spatial and temporal distribution characteristics of airport hotspots were varied with the variation of airport traffic flow and operational mode of runway,which shows that the hotspots have the characteristics of dynamic periodicity and diurnal variation.And the risk assessment results were consistent with experts'opinions and actual operation condition,which verified the rationality of the hotspot recognition algorithm,risk assessment model as well as the risk grade ranking criteria.展开更多
The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A'nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ra...The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A'nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ratios and some have Nb depletion and Pb enrichment. The OIB are LREE-enriched with (La/Yb)N =5―20, N-MORB are LREE-depleted with (La/Yb)N = 0.41―0.5. The OIB are featured by incompatible element enrichment and the N-MORB are obviously depleted with some metasomatic ef- fect, and E-MORB are geochemically intermediated. These rocks are distributed around the Majixue- shan OIB and gabbros in a thickness greater than a thousand meters and transitionally change along the ophiolite extension in a west-east direction, showing a symmetric distribution pattern as centered by the Majixueshan OIB, that is, from N-MORB, OIB and E-MORB association in the Dur'ngoi area to OIB in the Majixueshan area and then to N-MORB, OIB and E-MORB assemblage again in the Buqing- shan area. By consideration of the rock association, the rock spatial distribution and the thickness of the mafic rocks in the Majixueshan, coupled with the metasomatic relationship between the OIB and MORB sources, it can be argued that the Majixueshan probably corresponds to an ancient hotspot or an ocean island formed by mantle plume on the A'nyemaqeh ocean ridge, that is the ridge-centered hotspot, tectonically similar to the present-day Iceland hotspot.展开更多
The effective disposal of daily city infrastructure cases is an important issue for urban management. To more effectively utilize a large amount of historical cases data collected and accumulated in the urban grid man...The effective disposal of daily city infrastructure cases is an important issue for urban management. To more effectively utilize a large amount of historical cases data collected and accumulated in the urban grid management system, and to analyze their spatial distribution pattern information for city managers, this study used the comparative kernel density analysis method in two types of cases (i.e. power facilities and traffic guardrail) in Xicheng District, Beijing for the year 2016 and 2017. This research analyzes them at different scales (300 m, 600 m, 1,200 m), and the experiment results show that the method of comparative kernel density analysis is able to provide an intuitively spatial visualization distribution analysis of city infrastructure related cases. The quantitative information of spatial agglomeration degree is helpful for city managers making decision.展开更多
文摘本文采用文献计量方法,以科学知识图谱为工具,对"Web of Science核心合集"(2007-2017)中与STEM教育研究相关的1016篇文献进行回顾总结。结果显示:时间分布上,STEM教育经历了初步探索期、快速发展期和深化研究期三个阶段;空间分布上,美国是STEM教育的发源地且引领该领域的发展热潮,有关此领域的研究机构多集中在大学,研究作者集中在教育领域;研究热点上,基于学业表现、人才培养、课程设计等领域的研究热度始终不减。未来,STEM教育研究体现出更加重视构建完善的STEM教育体系及学习生态系统,重视整合学习和不断扩大STEM教育的学科融合等发展趋势。
基金The National Key Research and Development Program of China(2016YFC0503701,2016YFB0501502)The Strategic Priority Research Program of Chinese Academy of Sciences(XDA19040301,XDA20010202,XDA23100201)The Key Project of the High Resolution Earth Observation System in China(00-Y30B14-9001-14/16)
文摘Desertification research plays a key role in the survival and development of all mankind.The Normalized Comprehensive Hotspots Index(NCH)is a comprehensive index that reveals the spatial distribution of research hotspots in a given research field based on the number of relevant scientific papers.This study uses Web Crawler technology to retrieve the full text of all Chinese journal articles spanning the 1980s-2018 in the Chinese Academic Journal full-text database(CAJ)from CNKI.Based on the 253,055 articles on desertification that were retrieved,we have constructed a research hotspot extraction model for desertification in China by means of the NCH Index.This model can reveal the spatial distribution and dynamic changes of research hotspots for desertification in China.This analysis shows the following:1)The spatial distribution of research hotspots on desertification in China can be effectively described by the NCH Index,although its application in other fields still needs to be verified and optimized.2)According to the NCH Index,the research hotspots for desertification are mainly distributed in the Agro-Pastoral Ecotone and grassland in Inner Mongolia,the desertification areas of Qaidam Basin in the Western Alpine Zone and the Oasis-Desert Ecotone in Xinjiang(including the extension of the central Tarim Basin to the foothills of the Kunlun Mountains,the sporadic areas around the Tianshan Mountains and the former hilly belt of the southern foothills of the Altai Mountains).Among these three,the Agro-Pastoral Ecotone in the middle and eastern part of Inner Mongolia includes the most prominent hotspots in the study of desertification.3)Since the 1980s,the research hotspots for desertification in China have shown a general downward trend,with a significant decline in 219 counties(10.37%of the study area).This trend is dominated by the projects carried out since 2002.The governance of desertification in the eastern part of the Inner Mongolia-Greater Khingan Range still needs to be strengthened.The distribution of d
文摘全球创新网络是在科技创新全球化过程中围绕产业创新发展而形成的全球范围内创新主体、创新要素、创新制度之间建立起各类正式和非正式的跨国关系的总体结构。本文针对全球创新网络及相关研究主题,以Web of Science核心合集为数据来源,采用社会网络和可视化方法,刻画分析了全球创新网络研究热点、学科及空间分布网络特征;并通过构建活力指标和吸引力指标,评估了主要国家在该领域的研究潜力,包括自身研究的活跃度和在网络中的吸引力。结果表明,全球创新网络研究领域中新兴市场、创新政策等主题正在成为研究热点;该领域的研究主要受到商业与经济交叉相关学科领域学者的关注,其次是地理相关学科;欧美地区的研究工作较多,亚洲新兴经济体也做出了重要贡献。美、德、中、英四国为该领域的主要研究国家,在不同时期其研究潜力和优势领域不同,美国和德国研究实力较强并具有借鉴式合作潜力,中国和英国正在成为重要的研究节点国家并具有开创式合作潜力。
基金the Joint Funds of the National Science Foundation of China and the Civil Aviation Administration(Nos.U1733105 and U1733203)the Sichuan Science and Technology Program(No.2019YFG0308)
文摘The hotspot recognition algorithm is proposed based on a potential collision in order to study the aircraft taxi conflicts in large airports.The spatial and temporal distribution characteristics of hotspots are analyzed based on the risk assessment model of hotspot constructed in this paper.Firstly,approaches for monitoring of the aerodrome movement were compared.The hotspot recognition algorithm taken into account of whether aircrafts'taxi track has spatial and temporal overlap based on the aerodrome surveillance radar(ASR)data was presented,by identifying the hotspots through analyzing whether the aircrafts'time of entering and exiting the same taxiway is overlap or not,and the heading difference and distance of the two aircrafts satisfy the specified threshold constraint condition.Then,the ASR data were divided into several parts,and then airport hotspots were recognized and the spatial and temporal distribution characteristics were analyzed.The risk assessment model of airport safety hotspots was constructed which is taken into account of the conflict probability and its severity consequence.Finally,based on the risk grade assessment criteria and hotspots'risk value,the risk grade ranking of hotspot in one airport of China was evaluated and designated.According to the result,the spatial and temporal distribution characteristics of airport hotspots were varied with the variation of airport traffic flow and operational mode of runway,which shows that the hotspots have the characteristics of dynamic periodicity and diurnal variation.And the risk assessment results were consistent with experts'opinions and actual operation condition,which verified the rationality of the hotspot recognition algorithm,risk assessment model as well as the risk grade ranking criteria.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40234041 and 40572138)
文摘The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A'nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ratios and some have Nb depletion and Pb enrichment. The OIB are LREE-enriched with (La/Yb)N =5―20, N-MORB are LREE-depleted with (La/Yb)N = 0.41―0.5. The OIB are featured by incompatible element enrichment and the N-MORB are obviously depleted with some metasomatic ef- fect, and E-MORB are geochemically intermediated. These rocks are distributed around the Majixue- shan OIB and gabbros in a thickness greater than a thousand meters and transitionally change along the ophiolite extension in a west-east direction, showing a symmetric distribution pattern as centered by the Majixueshan OIB, that is, from N-MORB, OIB and E-MORB association in the Dur'ngoi area to OIB in the Majixueshan area and then to N-MORB, OIB and E-MORB assemblage again in the Buqing- shan area. By consideration of the rock association, the rock spatial distribution and the thickness of the mafic rocks in the Majixueshan, coupled with the metasomatic relationship between the OIB and MORB sources, it can be argued that the Majixueshan probably corresponds to an ancient hotspot or an ocean island formed by mantle plume on the A'nyemaqeh ocean ridge, that is the ridge-centered hotspot, tectonically similar to the present-day Iceland hotspot.
文摘The effective disposal of daily city infrastructure cases is an important issue for urban management. To more effectively utilize a large amount of historical cases data collected and accumulated in the urban grid management system, and to analyze their spatial distribution pattern information for city managers, this study used the comparative kernel density analysis method in two types of cases (i.e. power facilities and traffic guardrail) in Xicheng District, Beijing for the year 2016 and 2017. This research analyzes them at different scales (300 m, 600 m, 1,200 m), and the experiment results show that the method of comparative kernel density analysis is able to provide an intuitively spatial visualization distribution analysis of city infrastructure related cases. The quantitative information of spatial agglomeration degree is helpful for city managers making decision.
