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Regional Finite-Fault Source Model for Development of Ground Motion Attenuation Relationship in Sichuan, China
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作者 Wei Jiang Zelin Cao 《Structural Durability & Health Monitoring》 EI 2023年第1期37-54,共18页
The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the... The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the general characteristics of regional seism-tectonics,including the dip and depth of the fault plane,are emphasized.According to the statistics of regional seism-tectonics and focal mechanisms in Sichuan,China,and the sensitivity of estimated peak ground acceleration(PGA)attenuation is analyzed,and the dip angle is taken as an average of 70°.Based the statistics of the upper crustal structure and the focal depth of regional earthquakes,the bottom boundary of the sedimentary cover can be used as the upper limit for estimating the depth of upper-edge.The analysis shows that this value is sensitive to PGA.Based on the analysis of geometric relations,the corresponding calculation formula is used,and a set of concepts and steps for building the regional finite-fault source model is proposed.The estimation of source parameters takes into account the uncertainty,the geometric relationship among parameters and the total energy conservation.Meanwhile,a set of reasonable models is developed,which lay a foundation for the further study of regional ground motion attenuation based on seismology. 展开更多
关键词 Ground motion attenuation relationship dip angle upper-edge depth of rupture plane source parameter regional finite-fault source model
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Relationships between Regional Indian Summer Monsoon Rainfall and Eurasian Snow Cover 被引量:7
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作者 B. Parthasarathy Song Yang 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 1995年第2期143-150,共8页
In this work,correlation analysis is applied to study the interannual relationships betWeen indian summer monsoon rainfall of different homogeneous regions and Eurasian Snow Cover(ESC) during winter and spring seasons... In this work,correlation analysis is applied to study the interannual relationships betWeen indian summer monsoon rainfall of different homogeneous regions and Eurasian Snow Cover(ESC) during winter and spring seasons for the time period from 1973 to 1992.The monsoon rainfall of the western and central regions of india,as well as the all-India monsoon rainfall,is significantly negatively correlated with the ESC averaged for the monthsDecember-March and with,especially,the ESC of February.This study may provide some useful information for the long-range prediction of the regional indian monsoon rainfall. 展开更多
关键词 regional Indian raipfall Eurasian snow cover Interannual relationship
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Bilateral and Regional Strategic and Security Relationship Between China and the US after the Cold War
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作者 楚树龙 《Contemporary International Relations》 2000年第5期1-13,共13页
Sino-US relations are complex relations with multi-aspects between the two bigcountries in the world. It has three levels: the global level, the Asia-Pacificlevel and the bilateral level. The critical relationship bet... Sino-US relations are complex relations with multi-aspects between the two bigcountries in the world. It has three levels: the global level, the Asia-Pacificlevel and the bilateral level. The critical relationship between China and the US isembodied in the regional and bilateral levels that are more specific and essential.Beyond the field of economy and trade, their relationship is mainly embodied in thestrategic and security field. 展开更多
关键词 US Bilateral and regional Strategic and Security relationship Between China and the US after the Cold War SECURITY
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An empirical study on impact of high-speed rail on eco-relationship of regional tourist
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作者 HU Bei-ming LI Ya-nan 《Ecological Economy》 2016年第3期215-226,共12页
Study on the eco-relationship of regional tourism is a evaluation about the present situation and potential of regional tourist resources. In order to breaking the situation of the lack of coordination on tourist dest... Study on the eco-relationship of regional tourism is a evaluation about the present situation and potential of regional tourist resources. In order to breaking the situation of the lack of coordination on tourist destination in Guizhou province, understanding it after the opening of the Gui-Guang high-speed rail is beneficial. This paper constructs an evaluation index system about the eco-relationship of the regional tourist from five parts- the resource value, the tourist market, the traffic location, the reception conditions and the resource types. To summarize the changes of the tourist eco-relationship of samples before and after the opening of the high-speed rail,it calculates the weight by the judgment matrix, and then uses the cluster analysis of SPSS and the basis for judging the eco-relationship of regional tourist. To choose the emphasis and to guide the direction on tourism industry in Guizhou Province in the future high-speed rail era, a case study of the regional tourist destination in Guizhou section of the Gui-Guang high-speed rail is carried out. 展开更多
关键词 eco-relationship regional tourist Gui-Guang high-speed rail evaluation index system cluster analysis
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Localization Algorithm of Indoor Wi-Fi Access Points Based on Signal Strength Relative Relationship and Region Division 被引量:4
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作者 Wenyan Liu Xiangyang Luo +3 位作者 Yimin Liu Jianqiang Liu Minghao Liu Yun Q.Shi 《Computers, Materials & Continua》 SCIE EI 2018年第4期71-93,共23页
Precise localization techniques for indoor Wi-Fi access points(APs)have important application in the security inspection.However,due to the interference of environment factors such as multipath propagation and NLOS(No... Precise localization techniques for indoor Wi-Fi access points(APs)have important application in the security inspection.However,due to the interference of environment factors such as multipath propagation and NLOS(Non-Line-of-Sight),the existing methods for localization indoor Wi-Fi access points based on RSS ranging tend to have lower accuracy as the RSS(Received Signal Strength)is difficult to accurately measure.Therefore,the localization algorithm of indoor Wi-Fi access points based on the signal strength relative relationship and region division is proposed in this paper.The algorithm hierarchically divide the room where the target Wi-Fi AP is located,on the region division line,a modified signal collection device is used to measure RSS in two directions of each reference point.All RSS values are compared and the region where the RSS value has the relative largest signal strength is located as next candidate region.The location coordinate of the target Wi-Fi AP is obtained when the localization region of the target Wi-Fi AP is successively approximated until the candidate region is smaller than the accuracy threshold.There are 360 experiments carried out in this paper with 8 types of Wi-Fi APs including fixed APs and portable APs.The experimental results show that the average localization error of the proposed localization algorithm is 0.30 meters,and the minimum localization error is 0.16 meters,which is significantly higher than the localization accuracy of the existing typical indoor Wi-Fi access point localization methods. 展开更多
关键词 Wi-Fi access points indoor localization RSS signal strength relative relationship region division.
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Evolutionary relationship of 5′-untranslated regions among Thai dengue-3 viruses,Bangkok isolates,during 24 year-evolution
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作者 Watcharee Attatippaholkun Panyupa Pankhong +1 位作者 Ananda Nisalak Siripen Kalayanarooj 《Asian Pacific Journal of Tropical Medicine》 SCIE CAS 2015年第3期176-184,共9页
Objective:To study evolutionary relationship of the 5'untranslated regions(5'UTRs) in low passage dengue3 viruses(DEN3) isolated from hospitalized children with different clinical manifestations in Bangkok dur... Objective:To study evolutionary relationship of the 5'untranslated regions(5'UTRs) in low passage dengue3 viruses(DEN3) isolated from hospitalized children with different clinical manifestations in Bangkok during 24 year-evolution(1977-2000) comparing to the DEN3prototype(H87).Methods:The 5'UTRs of these Thai DEN3 and the H87 prototype were amplified by RT-PCR and sequenced.Their multiple sequence alignments were done by Codon Code Aligner v 4.0.4 software and their RNA secondary structures were predicted by MFOLD software.Replication of five Thai DEN3 candidates comparing to the 1187 prototype were done in human(HepG2) and the mosquito(C6/36) cell lines.Results:Among these Thai DEN3,the completely identical sequences of their first 89 nucleotides,their high-order secondary structure of 5'UTRs and three SNPs including the predominant C90 T,and two minor SNPs including A109 G and A112 G were found.The C90 T of Thai DEN3.Bangkok isolates was shown predominantly before 1977.Five Thai DEN3 candidates with the predominant C90 T were shown to replicate in human(HepG2) and the mosquito(C6/36) cell lines better than the H87 prototype.However,their highly conserved sequences as well as SNPs of the 5'UTR did not appear to correlate with their disease severity in human.Conclusions:Our findings highlighted evolutionary relationship of the completely identical 89 nucleotide sequence,the high-order secondary structure and the predominant C90 T of the 5'UTR of these Thai DEN3 during 24 year-evolution further suggesting to be their genetic markers and magic targets for future research on antiviral therapy as well as vaccine approaches of Thai DEN3. 展开更多
关键词 THAI dengue-3 viruses Evolutionary relationship 5’untranslated regions 24 Year-evolution
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The Study on the Strong Ground Motion Attenuation Relationship in the Pishan Area,Xinjiang Uygur Autonomous Region
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作者 Li Wenqian Tao Zhengru +1 位作者 Wei Bin He Jingang 《Earthquake Research in China》 CSCD 2018年第1期40-52,共13页
Small earthquake data from the Pishan MS6.5 aftershocks is collected by the Xinjiang Regional Digital Seismic Observation Network.Five parameters of the focal region are obtained by micro genetic inversion:stress dro... Small earthquake data from the Pishan MS6.5 aftershocks is collected by the Xinjiang Regional Digital Seismic Observation Network.Five parameters of the focal region are obtained by micro genetic inversion:stress dropΔσof 75.95 bars,quality factor parameters Q0of 186.33 andηof 0.26,geometric attenuation parameters R1of 72.18km and R2of 139.70km.We calculate the Fourier spectrum and combine it with the random phase spectrum to get the ground motion time history,and build the strong motion acceleration attenuation relationship.The strong ground motion acceleration attenuation of the Pishan area is thus obtained.Because of the insufficiency of strong ground motion records,we added the records from the Wuqia MS6.9 earthquake on October 5,2008,the Akto MS6.2 earthquake on October 6,2008,and the Lop MS6.0 earthquake on March 9,2012 to the data.The comparison of the calculation results and the empirical attenuation relationships with strong ground motion records reveal that the strong motion data of Pishan and Lop earthquakes is higher than the empirical attenuation relationships.The Wuqia MS6.9 earthquake strong motion data is consistent with Yu Yanxiangs(2013)short axis result,and lower than the present result. 展开更多
关键词 Small EARTHQUAKE data Parameters of FOCAL region Micro GENETIC INVERSION Ground motion acceleration ATTENUATION relationship
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Development of Qinba Mountainous Area in the Historical Period from the Perspective of Man-Land Relationship
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作者 Siyu YOU Zhimin FAN 《Asian Agricultural Research》 2018年第5期85-88,共4页
Taking agricultural development as the starting point,this paper explored the dynamic mechanism and implementation path of agricultural development in Qinba Mountainous Area from the perspective of man-land relationsh... Taking agricultural development as the starting point,this paper explored the dynamic mechanism and implementation path of agricultural development in Qinba Mountainous Area from the perspective of man-land relationship. It found the regular understanding of ecological changes in Qinba Mountains. It is a comprehensive review and exploration on agricultural development and environmental evolution,and aims to provide a historical reference for the development of the contemporary Qinba Mountains. 展开更多
关键词 man-land relationship Qinba Mountainous Area Agricultural development
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MVCE-Net: Multi-View Region Feature and Caption Enhancement Co-Attention Network for Visual Question Answering
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作者 Feng Yan Wushouer Silamu Yanbing Li 《Computers, Materials & Continua》 SCIE EI 2023年第7期65-80,共16页
Visual question answering(VQA)requires a deep understanding of images and their corresponding textual questions to answer questions about images more accurately.However,existing models tend to ignore the implicit know... Visual question answering(VQA)requires a deep understanding of images and their corresponding textual questions to answer questions about images more accurately.However,existing models tend to ignore the implicit knowledge in the images and focus only on the visual information in the images,which limits the understanding depth of the image content.The images contain more than just visual objects,some images contain textual information about the scene,and slightly more complex images contain relationships between individual visual objects.Firstly,this paper proposes a model using image description for feature enhancement.This model encodes images and their descriptions separately based on the question-guided coattention mechanism.This mechanism increases the feature representation of the model,enhancing the model’s ability for reasoning.In addition,this paper improves the bottom-up attention model by obtaining two image region features.After obtaining the two visual features and the spatial position information corresponding to each feature,concatenating the two features as the final image feature can better represent an image.Finally,the obtained spatial position information is processed to enable the model to perceive the size and relative position of each object in the image.Our best single model delivers a 74.16%overall accuracy on the VQA 2.0 dataset,our model even outperforms some multi-modal pre-training models with fewer images and a shorter time. 展开更多
关键词 Bottom-up attention spatial position relationship region feature self-attention
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区域水平衡及失衡程度度量方法 被引量:2
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作者 左其亭 吴青松 +2 位作者 纪义虎 邱曦 陶洁 《水利学报》 EI CSCD 北大核心 2024年第1期1-12,共12页
区域水平衡量化及诊断是水网工程建设优化和水资源均衡调控的基础,对提升水安全保障能力、支撑经济社会稳定发展、实现人水和谐具有重要意义。本文从空间、时间、结构、过程、总量五个维度解构了区域人水系统的四大平衡,即反映水收入项... 区域水平衡量化及诊断是水网工程建设优化和水资源均衡调控的基础,对提升水安全保障能力、支撑经济社会稳定发展、实现人水和谐具有重要意义。本文从空间、时间、结构、过程、总量五个维度解构了区域人水系统的四大平衡,即反映水收入项和支出项定量关系的水收支平衡、体现经济社会供水量与需水量匹配关系的经济社会供需水平衡、结合经济社会-生态系统发展与用水定量关系的经济社会与生态用水平衡、表征人水系统发展状态的人水关系和谐平衡,并提出相应的水平衡度量方法。多角度解析了区域水平衡的失衡状态,提出四大平衡的失衡程度度量方法及区域水平衡的失衡程度综合度量方法。以沁河流域为实例应用和检验了上述方法,结果表明:提出的度量方法具有科学性和适用性,能够应用于区域水平衡研究实践;2019年沁河流域水平衡的失衡度为0.327,处于蓄水量减少、水资源短缺、生态端亏水、水系统受损的中度失衡状态,后续应注重人类涉水行为的管控。研究成果可为区域水平衡评估与调控提供理论支撑,服务国家或区域水平衡策略制定和水网工程规划。 展开更多
关键词 区域水平衡 失衡程度 度量方法 人水关系 人水系统
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数字金融与区域经济发展的耦合协调性测度及其动态演进 被引量:1
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作者 姚登宝 俞旭海 《兰州财经大学学报》 2024年第1期101-112,共12页
以中国八大综合经济区为例,运用耦合协调度模型分析数字金融对区域经济发展的耦合协调关系,并基于Dagum基尼系数与Kernel核密度揭示数字金融与区域经济发展之间协调关系的地区差异及动态演进规律。结果表明:八大综合经济区的经济发展水... 以中国八大综合经济区为例,运用耦合协调度模型分析数字金融对区域经济发展的耦合协调关系,并基于Dagum基尼系数与Kernel核密度揭示数字金融与区域经济发展之间协调关系的地区差异及动态演进规律。结果表明:八大综合经济区的经济发展水平总体呈现稳定增长态势,具有“东高西低”阶梯形的异质性和阶段性特征;数字金融与区域经济发展之间协调发展水平逐年提升,八大综合经济区普遍由失调阶段跨入协调阶段;数字金融与区域经济发展之间协调关系存在明显的地区差异,沿海经济区的协调水平明显高于内陆经济区,但地区间协调程度的差距呈现逐渐缩小的演进态势。 展开更多
关键词 数字金融 区域经济发展 协调关系 地区差异 动态演进
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石家庄市县域科技创新与经济发展耦合协调关系时空演变 被引量:1
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作者 冯晓淼 贺军亮 《石家庄学院学报》 2024年第1期63-75,共13页
选取石家庄市13个县域单元作为研究区域,构建科技创新能力和经济发展水平评价指标体系,计算评价指数,测算两者的耦合协调度,使用ArcGIS绘制空间分布图,深入剖析科技创新能力、经济发展水平以及两者耦合协调关系的时空演变特征。研究发现... 选取石家庄市13个县域单元作为研究区域,构建科技创新能力和经济发展水平评价指标体系,计算评价指数,测算两者的耦合协调度,使用ArcGIS绘制空间分布图,深入剖析科技创新能力、经济发展水平以及两者耦合协调关系的时空演变特征。研究发现:全市县域科技创新能力和经济发展水平呈现较强的正相关性,且都在2010—2017年间提升速度较快,而在2019年之后提升速度呈减慢的趋势。2010—2021年经济发展水平指数均高于科技创新能力指数,但后者提升速度高于前者,表明石家庄市各县域科技创新能力滞后于经济发展水平,但科技创新能力的发展势头较好。2010年以来,全市县域耦合协调度呈现上升趋势,但耦合协调度与科技创新能力和经济发展水平的变化趋势相似,即2018年之前的提升速度要快于2018年之后。2021年,全市县域耦合协调度等级为“勉强协调发展”,协调发展水平较低,有待进一步提升。 展开更多
关键词 石家庄市 县域 科技创新 经济发展 耦合协调关系
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1990-2020年长三角地区生境质量与夜间灯光的空间关系
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作者 彭建 吕俭 杨灿灿 《环境科学与技术》 CAS CSCD 北大核心 2024年第1期155-165,共11页
基于1990-2020年长三角地区的土地利用数据和夜间灯光数据,运用InVEST生境质量评估模型、双变量空间自相关、相关系数对生境质量与夜间灯光的时空关系进行研究,并应用地理加权回归和归纳法分析两者的响应规律,结果表明:(1)浙江省总体上... 基于1990-2020年长三角地区的土地利用数据和夜间灯光数据,运用InVEST生境质量评估模型、双变量空间自相关、相关系数对生境质量与夜间灯光的时空关系进行研究,并应用地理加权回归和归纳法分析两者的响应规律,结果表明:(1)浙江省总体上生境最优且城镇发展最快,安徽省在城镇快速发展的同时生境相对下降最少,生境质量和夜间灯光空间分布格局呈现出与区位、地形等因素的空间耦合性。(2)长三角地区生境质量与夜间灯光指数随着时间的发展空间上的依赖性越来越强,聚类模式主要为高-低、低-高及低-低3种。高-低聚类区域主要分布在浙江省和安徽省的南部、西部的山地丘陵,研究期内呈现缩小的趋势;低-高聚类区域在长三角东部平原区呈集聚分布、北部平原丘陵区呈零散分布,呈现扩张趋势。(3)不同年份各省份生境质量与夜间灯光指数呈显著负相关,且经济越发达的省份,生境质量与夜间灯光指数的负相关关系越强;生境质量与夜间灯光指数呈高度负相关的区县主要分布在长江下游沿岸和浙江省东部,相关性不显著的区县主要分布在安徽省、江苏省的北部,变化类型以负相关关系持续增强型占比最高。(4)生境质量与夜间灯光指数的相关关系随着城市发展呈U型变化,即随着城市发展,生境质量与夜间灯光指数的负相关关系先增强后下降。研究结果可为长三角城市可持续发展、生境调控提供前期基础。 展开更多
关键词 生境质量 夜间灯光影像 空间关系 演变规律 地理加权回归 长三角地区
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自然地理学与人文地理学整合之我见
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作者 汤茂林 《热带地理》 CSCD 北大核心 2024年第1期36-41,共6页
在当代地理学中,自然地理学与人文地理学两个分支学科分裂严重,从论题到发表乃至对话对象。因此两者的关系值得讨论。维持地理学的综合性有助于发挥地理学的优势,应对综合性问题、全球性问题。人地关系和区域地理学是避免地理学分裂的... 在当代地理学中,自然地理学与人文地理学两个分支学科分裂严重,从论题到发表乃至对话对象。因此两者的关系值得讨论。维持地理学的综合性有助于发挥地理学的优势,应对综合性问题、全球性问题。人地关系和区域地理学是避免地理学分裂的具体途径,GIS可以成为弥合两者的工具。大众对地理学的科普需求是区域地理,这是地理学满足社会需求需要的重要方式。着眼于科学普及的区域地理学著作有助于提高学科的社会认同度。 展开更多
关键词 专业化 综合性 区域地理学 人地关系 科学普及
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区域协调、央地关系和基本权利的中央化
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作者 宣晓伟 《经济与管理评论》 北大核心 2024年第1期5-14,共10页
区域协调发展本质上是个中央和地方关系的议题,要促进“效率”和“公平”兼顾的区域协调发展,根本上有赖于建立合理的央地关系。改革开放以来,我国中央和地方关系的制度安排呈现出“效率优先、兼顾公平”的总体取向,在地区竞争模式下试... 区域协调发展本质上是个中央和地方关系的议题,要促进“效率”和“公平”兼顾的区域协调发展,根本上有赖于建立合理的央地关系。改革开放以来,我国中央和地方关系的制度安排呈现出“效率优先、兼顾公平”的总体取向,在地区竞争模式下试图通过缩小地区增长差距来推动区域之间协调发展。当我国逐渐进入第三产业占主导、经济空间集聚程度不断提高的新阶段,区域协调发展战略面临着由“推动地区经济增长”向“居民基本公共服务均等化”的转型。根据事务属性合理划分中央和地方权限,推动“公民基本权利的中央化”,落实中央政府基本公共服务均等化供给的责任,是推动区域协调发展战略真正做到“公平”和“效率”兼顾的制度保障。 展开更多
关键词 区域协调 央地关系 基本权利 中央化
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经济社会与生态用水平衡计算规则与方法
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作者 左其亭 全志淼 +3 位作者 吴青松 邱曦 秦西 张羽 《水资源保护》 EI CAS CSCD 北大核心 2024年第3期1-10,共10页
从平衡的概念出发,针对经济社会与生态用水竞争问题,提出了经济社会与生态用水平衡的概念,并论述了其内涵及特性;构建了经济社会与生态用水平衡计算规则框架,包括遵循四大规律、基于六大理论、考虑六大因素、符合三大准则;提出了经济社... 从平衡的概念出发,针对经济社会与生态用水竞争问题,提出了经济社会与生态用水平衡的概念,并论述了其内涵及特性;构建了经济社会与生态用水平衡计算规则框架,包括遵循四大规律、基于六大理论、考虑六大因素、符合三大准则;提出了经济社会与生态用水平衡的计算思路,包括资料处理、量化计算、结果检验3个步骤,并给出了其计算方法和计算结果表征方式。以2019年沁河流域为例,量化了流域经济社会与生态用水平衡;在求解一次平衡点以及经济社会用水刚性约束、生态用水刚性约束、综合效益刚性约束条件下平衡结果的基础上,综合考虑六大因素以及总需水量与水资源总量关系,确定了沁河流域经济社会与生态用水平衡点,即经济社会用水与生态用水的比例为0.71∶0.29。 展开更多
关键词 经济社会与生态用水平衡 区域水平衡 计算规则 人水关系 沁河流域
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伊朗与也门胡塞武装的准联盟关系探析
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作者 金良祥 曹燕媚 《阿拉伯世界研究》 北大核心 2024年第3期131-156,160,共27页
将伊朗与也门胡塞武装关系视为“代理人”关系的观点过于强调伊朗对胡塞武装的影响力;将两者视为战略联盟关系的观点则过于强调双方关系的约束性,低估了两者之间关系的灵活性;而将两者关系视为伊朗宣传作秀的观点,又忽视了两者所存在的... 将伊朗与也门胡塞武装关系视为“代理人”关系的观点过于强调伊朗对胡塞武装的影响力;将两者视为战略联盟关系的观点则过于强调双方关系的约束性,低估了两者之间关系的灵活性;而将两者关系视为伊朗宣传作秀的观点,又忽视了两者所存在的战略合作现实。本文认为,伊朗与胡塞武装是基于共同的反美、反以和反对地区亲美政权意识形态,且具有阶段性共同战略利益的准联盟。灵活性的战略合作是伊朗与胡塞武装双方关系的基本特点,具体而言:一是纵观双方关系的历史,战略合作集中体现在两个时间段,其他时段双方战略合作并不突出;二是双方合作以共同的战略利益为动力,包括钳制沙特以及反美和反以等;三是双方的合作内容多为伊朗对胡塞武装提供军事和政治支持,具有很强的政治性。未来,双方仍将基于共同的战略利益开展合作,但签订正式且高约束性的合作条约的可能性较小。综合来看,伊朗与胡塞武装的联系与合作会因形势和战略利益的变化而表现出灵活性:在面对共同的地缘政治威胁和有利的战略时机之时,双方会加强合作的紧密性;而在利益分歧较大、需要改善周边安全环境等情况下,双方的联系则会淡化。 展开更多
关键词 胡塞武装 准联盟 伊朗地区战略 伊朗—沙特关系
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中美博弈:近昔和当今及对中国战略的意涵
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作者 时殷弘 《亚太安全与海洋研究》 北大核心 2024年第3期19-35,I0002,共18页
过去15年里,中美关系的首要特征是博弈而非协调。两国博弈先在战略阵线开启,继而在战略、经贸、高技术和意识形态四条主要阵线展开。就中美博弈总体而言,美国处于“防守型”战略态势,美国认为它长时期拥有的重大优势地位一个又一个地丧... 过去15年里,中美关系的首要特征是博弈而非协调。两国博弈先在战略阵线开启,继而在战略、经贸、高技术和意识形态四条主要阵线展开。就中美博弈总体而言,美国处于“防守型”战略态势,美国认为它长时期拥有的重大优势地位一个又一个地丧失或被侵蚀,首要动能在中国一边。中共十八大以来,中国逐渐成为一个急剧腾升的强国。大为增强的国力,使中国更加坚定了自信和抱负。中国内外发力,争取在世界政治经济和全球治理的某些问题领域参与引领甚或单独引领,实现在亚洲大陆以及发展中世界的经济和外交优势,大致取得在西太平洋的对美战略和军事优势,进一步地,对第一至第二岛链之间的战略空间的控扼能力愈益被视为必要。回顾奥巴马、特朗普和拜登三届美国政府的对华态势和政策,对未来中美关系应做好准备应对可能的疾风暴雨。 展开更多
关键词 中美关系 中美博弈 战略博弈 中国战略 亚太地区 南海
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Regional features of pollen R-values in China 被引量:1
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作者 Jie XIA Jian NI 《Science China Earth Sciences》 SCIE EI CAS CSCD 2024年第1期295-308,共14页
Establishing a quantitative relationship between modern pollen and vegetation remains a pivotal but intricate pursuit within the field of Quaternary palynology.The R-value,a well-established and traditional metric cha... Establishing a quantitative relationship between modern pollen and vegetation remains a pivotal but intricate pursuit within the field of Quaternary palynology.The R-value,a well-established and traditional metric characterized by its simplicity and direct applicability,serves to calibrate the nonlinear disparities between surface pollen and modern vegetation.This study entails the construction of a comprehensive pollen R-value dataset for China derived from R-values published between 1987 and 2021.The dataset,compiled after rigorous screening,calibration,and standardization processes,encompasses 898 modern pollen sampling sites and 2115 pollen R-value data entries,encapsulating 152 pollen taxa spanning 65 families and 113 genera.Synthesizing the extracted R-values yielded the following insights:(1)A macrospatial analysis validates previously established knowledge at a site-specific scale.Evidently,pollen R-value variations across China are statistically significant.Approximately two-thirds of pollen taxa exhibit underrepresentation(e.g.,Taxodiaceae,Corylus,Nitraria,Tamarix,Cyperaceae,Poaceae,and Fabaceae),while the remaining one-third display overrepresentation(e.g.,Pinus,Picea,Betula,Ephedra,Chenopodiaceae,and Artemisia).The degree of underrepresentation surpasses that of overrepresentation,and the representation patterns of Castanea,Quercus,Polygonaceae,and Asteraceae are contingent upon vegetation types.(2)Pollen R-values follow distinct spatial distribution patterns within China.In the woody vegetation region of eastern China,R-values progressively decline from north to south,correlating with rising temperatures and precipitation.Conversely,in herbaceous vegetation regions of northern and western China,R-values decrease from east to west and from northeast to southwest,corresponding to increased aridity.Nevertheless,pollen R-values manifest variation contingent on pollen taxa,vegetation types,and climatic regions,even differing for the same taxa across varying vegetation types and climatic conditions.This highlights the intricate nature of pollen R-values and their interpretation of pollen-vegetation relationships.(3)Pollen R-values and relative pollen production estimates exhibit resemblances and a modest positive correlation.However,adjudicating between them as representatives of vegetation requires nuanced consideration,as both metrics convey pollen representation within vegetation,demonstrating the multifaceted relationships they share with modern vegetation.Further recommendations suggest that when assessing pollen representation in modern vegetation,fossil pollen content should be weighted using either the median or log-transformed R-value.This approach underscores the necessity of comprehensively accounting for divergences and convergences across various spatial scales and vegetation types,particularly the disparities observed within identical pollen taxa across dissimilar regions. 展开更多
关键词 Pollen R-value Modern pollen-vegetation relationship regional pattern VARIABILITY Paleovegetation reconstruction
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结合区域结构关系和自注意力的边卷积点云分类分割网络
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作者 吕志玮 杨家志 +1 位作者 周国清 沈露 《计算机工程与应用》 CSCD 北大核心 2024年第13期171-179,共9页
针对深度学习点云网络中区域内上下文和关系特征捕获不充分问题,提出了一种新的网络框架ISEC-Net(inter-region structure relations and self-attention edge convolution network)。该网络由IrConv(inter-region convolution)模块和Sa... 针对深度学习点云网络中区域内上下文和关系特征捕获不充分问题,提出了一种新的网络框架ISEC-Net(inter-region structure relations and self-attention edge convolution network)。该网络由IrConv(inter-region convolution)模块和SaConv(self-attention convolution)模块组成,SaConv模块可以提取到更细粒的边特征,而IrConv可以动态地将局部结构信息集成到点特征中,然后自适应地捕获区域间关系。在ModelNet40数据集和ShapeNet数据集上分别对点云分类和部件分割进行了大量实验,实验结果表明,在ModelNet40数据集上,ISEC-Net模型的总体精度(OA)达到了93.5%,平均精度(mAcc)达到了90.7%;而在ShapeNet数据集上,平均并交比(mIoU)达到了86.1%,并且在单类并交比(IoU)实验中吉他、耳机、杯子等部件分割精度表现优异,说明ISEC-Net与传统的动态图卷积相比,能够精确地捕捉点云的局部特征和精细结构并加强全局特征的聚合,具有出色的有效性和泛化能力。 展开更多
关键词 边卷积 区域上下文 区域关系 自注意力 深度学习
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