检索结果-南通市图书馆

Journal of Geographical Sciences 2024年第10期34卷 1883-1903页

作者： LUO Yuanbo zhou Yuke zhou chenghu State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchCAsBeijing 100101China

Changes in surface temperature extremes have become a global *** on the daily lowest temperature(TN)and daily highest temperature(TX)data from 2138weather stations in China from 1961 to 2020,we calculated 14 extreme temperature indices to analyze the characteristics of extreme temperature *** widespread changes observed in all extreme temperature indices suggest that China experienced significant warming during this ***,the cold extreme indices,such as cold nights,cold days,frost days,icing days,and the cold spell duration index,decreased significantly by-6.64,-2.67,-2.96,-0.97,and-1.01 days/decade,*** contrast,we observed significant increases in warm extreme *** number of warm nights,warm days,summer days,tropical nights,and warm spell duration index increased by 8.44,5.18,2.81,2.50,and 1.66d/decade,*** addition,the lowest TN,highest TN,lowest TX,and highest TX over the entire period rose by 0.47,0.22,0.26,and 0.16℃/decade,***,using Pearson's correlation and wavelet coherence analyses,this study identified a strong association between extreme temperature indices and atmospheric circulation factors,with varying correlation strengths and resonance periods across different time-frequency domains.

关键词： temperature changes global warming atmospheric circulation wavelet coherence analysis China

VSAN:A new visualization method for super-large-scale academic networks

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2024年第1期18卷 119-137页

作者： Qi LI Xingli WANG Luoyi FU Xinde CAO Xinbing WANG Jing ZHANG chenghu zhou Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai 200240China Department of Computer Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China

As a carrier of knowledge,papers have been a popular choice since ancient times for documenting everything from major historical events to breakthroughs in science and *** the booming development of science and technology,the number of papers has been growing *** like the fact that Internet of Things(IoT)allows the world to be connected in a flatter way,how will the network formed by massive academic papers look like?Most existing visualization methods can only handle up to hundreds of thousands of node size,which is much smaller than that of academic networks which are usually composed of millions or even more *** this paper,we are thus motivated to break this scale limit and design a new visualization method particularly for super-large-scale academic networks(VSAN).Nodes can represent papers or authors while the edges means the relation(e.g.,citation,coauthorship)between *** order to comprehensively improve the visualization effect,three levels of optimization are taken into account in the whole design of VSAN in a progressive manner,i.e.,bearing scale,loading speed,and effect of layout *** main contributions are two folded:(1)We design an equivalent segmentation layout method that goes beyond the limit encountered by state-of-the-arts,thus ensuring the possibility of visually revealing the correlations of larger-scale academic entities.(2)We further propose a hierarchical slice loading approach that enables users to observe the visualized graphs of the academic network at both macroscopic and microscopic levels,with the ability to quickly zoom between different *** addition,we propose a“jumping between nebula graphs”method that connects the static pages of many academic graphs and helps users to form a more systematic and comprehensive understanding of various academic *** our methods to three academic paper citation datasets in the AceMap database confirms the visualization scalability of VSAN in t

关键词： academic networks large graph visualization graph layout graph loading

EvolveKG:a general framework to learn evolving knowledge graphs

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2024年第3期18卷 43-59页

作者： Jiaqi LIU Zhiwen YU Bin GUO Cheng DENG Luoyi FU Xinbing WANG chenghu zhou School of Computer Science Northwestern Polytechnical UniversityXi’an 710129China Department of Computer Science Shanghai Jiao Tong UniversityShanghai 200240China Institute of Geographical Science and Natural Resources Research Chinese Academy of SciencesBejjing 100864China

A great many practical applications have observed knowledge evolution,i.e.,continuous born of new knowledge,with its formation influenced by the structure of historical *** observation gives rise to evolving knowledge graphs whose structure temporally grows over ***,both the modal characterization and the algorithmic implementation of evolving knowledge graphs remain *** this end,we propose EvolveKG–a general framework that enables algorithms in the static knowledge graphs to learn the evolving *** quantifies the influence of a historical fact on a current one,called the effectiveness of the fact,and makes knowledge prediction by leveraging all the cross-time knowledge *** novelty of EvolveKG lies in Derivative Graph–a weighted snapshot of evolution at a certain ***,each weight quantifies knowledge effectiveness through a temporarily decaying function of consistency and attenuation,two proposed factors depicting whether or not the effectiveness of a fact fades away with ***,considering both knowledge creation and loss,we obtain higher prediction accuracy when the effectiveness of all the facts increases with time or remains *** four real datasets,the superiority of EvolveKG is confirmed in prediction accuracy.

关键词： knowledge graph evolution modal characterization algorithmic implementation

Spatio-temporal patterns of temperature extremes and their response to atmospheric circulation factors in China from 1961 to 2020

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 2024年第10期 1883-1910页

作者： LUO Yuanbo zhou Yuke zhou chenghu State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research CAS University of Chinese Academy of Sciences Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research CAS

Changes in surface temperature extremes have become a global concern. Based on the daily lowest temperature(TN) and daily highest temperature(TX) data from 2138weather stations in China from 1961 to 2020, we calculated 14 extreme temperature indices to analyze the characteristics of extreme temperature events. The widespread changes observed in all extreme temperature indices suggest that China experienced significant warming during this period. Specifically, the cold extreme indices, such as cold nights, cold days, frost days, icing days, and the cold spell duration index, decreased significantly by-6.64,-2.67,-2.96,-0.97, and-1.01 days/decade, respectively. In contrast, we observed significant increases in warm extreme indices. The number of warm nights, warm days, summer days,tropical nights, and warm spell duration index increased by 8.44, 5.18, 2.81, 2.50, and 1.66d/decade, respectively. In addition, the lowest TN, highest TN, lowest TX, and highest TX over the entire period rose by 0.47, 0.22, 0.26, and 0.16°C/decade, respectively. Furthermore,using Pearson's correlation and wavelet coherence analyses, this study identified a strong association between extreme temperature indices and atmospheric circulation factors, with varying correlation strengths and resonance periods across different time-frequency domains.

关键词：

A four-band index for both liquid and solid water and its applications in the Aral Sea Basin

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第3期67卷 769-788页

作者： Bing YUE Xi CHEN Saibo LI Zhengping DU John WILSON Junhui YANG Yimen JIAO Shuangyan HUANG chenghu zhou Xinjiang Institute of Ecology and Geography Chinese Academy of SciencesUrumqi 830011China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Institute of Geographical Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China Spatial Sciences Institute University of Southern CaliforniaLos AngelesCA 90089-0374USA

Various investigations have been conducted to analyze the water-coverage area of the Aral Sea and the Aral Sea Basin(ASB). However, the investigations incorporated considerable uncertainty and the used water indices had misclassification problem, which made different research groups present different results. Thus we first ascertain the boundaries of the ASB, the Syr and Amu river basins as well as their upper, middle and lower reaches. Then a four-band index for both liquid and solid water(ILSW) is proposed to address the misclassification problems of the classic water indices. ILSW is calculated by using the reflectance values of the green, red, near infrared, and thermal infrared bands, which combines the normalized difference water index(NDWI) and land surface temperature(LST) together. Validation results show that the ILSW water index has the highest accuracy by far in the Aral Sea Basin. Our results indicate that annual average decline of the water-coverage area was 963 km^(2) in the southern Aral Sea, whereas the northern Aral Sea has experienced little change. In the meanwhile, permanent ice and snow in upper reach of ASB has retreated considerably. Annual retreating rates of the permanent ice and snow were respectively 6233and 3841 km^(2) in upper reaches of Amu river basin(UARB) and Syr river basin(USRB). One of major reasons is that climate has become warmer in ASB. The climate change has caused serious water deficit problem. The water deficit had an increasing trend since the 1990s and its increasing rates was 3.778 billion m^(3) yearly on average. The total water deficit was 76.967 billion m^(3) on average in the whole area of ASB in the 2010s. However, up reaches of Syr river basin(USRB), a component area of ASB, had water surplus of 25.461 billion m^(3). These conclusions are useful for setting out a sustainable development strategy in ASB.

关键词： Aral Sea Basin Syr river basin Amu river basin Water indices Water-coverage area Water deficit Climate change

在线全文

学校读者我要写书评

暂无评论

基于生态系统文化服务的人地关系空间重构

地理学报 2024年第7期79卷 1682-1699页

作者：钟敬秋高梦凡韩增林周成虎闫晓露辽宁师范大学海洋可持续发展研究院教育部人文社科重点研究基地大连116029 辽宁省“海洋经济高质量发展”高校协同创新中心大连116029 中国科学院地理科学与资源研究所资源与环境信息系统国家重点实验室北京100101 华东师范大学河口海岸学国家重点实验室上海200241

生态系统文化服务(CESs)作为生态系统为人类所提供的非物质裨益与福祉,具备桥接并诠释自然与人类社会复杂纽带关系的能力,其能够围绕空间需求—空间规划—空间生产,通过自上而下和自下而上的多层次干预,实现可持续发展和人类福祉提高。... 详细信息

生态系统文化服务(CESs)作为生态系统为人类所提供的非物质裨益与福祉,具备桥接并诠释自然与人类社会复杂纽带关系的能力,其能够围绕空间需求—空间规划—空间生产,通过自上而下和自下而上的多层次干预,实现可持续发展和人类福祉提高。准确把握CESs参与人地关系空间重构实践路径,既是实现人类福祉有效提升亟需解决的科学问题,也是实现人与自然和谐共生的重要理论基础。为此,本文基于“理论解析—关联机制—实践应用—发展路径”解构方案,探讨CESs引导人地关系空间重构的内在逻辑体系与可行性。在梳理价值评估—价值权衡—“流”时期CESs研究演进历程基础上,构建CESs指导人地关系空间重构理论框架,探究其指导三生空间重构应用路径。最终,本文在数据收集、方法体系、实践应用等方面展开论述,以期实现CESs研究由理论到实践的转变,为新时期人地关系空间重构提供新视角。

关键词：生态系统文化服务人地关系优化调控空间重构新时代生态文明建设三生空间

非接触功率传输系统超低压软启动方法建模研究

在线全文

学校读者我要写书评

暂无评论

电力系统保护与控制 2024年第19期52卷 108-118页

作者：周成虎唐征宇黄全振张洋张劳模河南工程学院电气信息工程学院河南郑州451191 中国移动通信集团河南有限公司港区分公司河南郑州450000 河南工程学院软件学院河南郑州451191

在直接启动非接触传输系统的过程中,电源输入功率、电流的峰值可达稳态值数倍至数百倍,且变换器开关管易出现单次硬开关现象,导致开关管老化甚至击穿。针对该问题,以三相LCC非接触功率传输系统为研究对象,推导出其等效电路对应微分方程... 详细信息

在直接启动非接触传输系统的过程中,电源输入功率、电流的峰值可达稳态值数倍至数百倍,且变换器开关管易出现单次硬开关现象,导致开关管老化甚至击穿。针对该问题,以三相LCC非接触功率传输系统为研究对象,推导出其等效电路对应微分方程的奇次解和非奇次方程特解及完全解,根据奇次解与电源激励无直接关联且决定暂态特性的结论,提出超低电压的软启动方法。分析表明:软启动方法的理论基础是微分方程的零输入响应和零状态响应具有可分解特性;用数学建模和仿真验证了软启动能降低系统的零输入响应峰值;用电路仿真验证了软启动能有效避免开关管出现单次硬开关的现象;在电路运行过程中如果电源短时断电,且驱动电路因内部储能而持续工作,则要使用软启动方法重新启动,以避免直接启动引起的冲击效应;提出了初始变化率的近似计算方法,得出了初值与电源激励有关的结论。实验证明了上述结论的正确性。

关键词：非接触功率传输数学模型软启动

维普期刊数据库博看期刊

Algebraic encoding scheme for aperture 3 hexagonal discrete global grid system

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2018年第2期61卷 215-227页

作者： BEN Jin LI YaLu zhou chenghu WANG Rui DU LingYu Institute of Surveying and Mapping Information Engineering University State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences College of Earth Science and Surveying Engineering China University of Mining and Technology (Beijing)

Discrete Global Grid Systems(DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. They provide an organizational structure that permits fast integration between multiple sources of large and variable geospatial data sufficient for visualization and analysis. Despite a significant body of research supporting hexagonal DGGSs as the superior choice, the application thereof has been hindered owing in part to the lack of a rational hierarchy with an efficient addressing system. This paper presents an algebraic model of encoding scheme for the Aperture 3 Hexagonal(A3H) DGGS. Firstly, the definition of a grid cell, which is composed of vertices, edges, and a center, is introduced to describe fundamental elements of grids. Secondly, by identifying the grid cell with its center, this paper proves that cell centers at different levels can be represented exactly using a mixed positional number system in the complex plane through the recursive geometric relationship between two successive levels, which reveals that grid cells are essentially special complex radix numbers. Thirdly, it is shown that through the recursive geometric relationship of successive odd or even levels, the mixed positional number system can also be applied to uniquely represent cell centers at different levels under specific constraint conditions, according to which the encoding scheme is designed. Finally, it is shown that by extending the scheme to 20 triangular faces of the regular icosahedron,multi-resolution grids on closed surfaces of the icosahedron are addressed perfectly. Contrast experiments show that the proposed encoding scheme has the advantages of theoretical rigor and high programming efficiency and that the efficiency of cross-face adjacent cell searching is 242.9 times that of a similar scheme. Moreover, the proposed complex radix number representation is an ideal formalized description tool for grid systems. The research i

关键词： Discrete Global Grid System Hexagon Positional number system Algebraic encoding

The Generic Annular Bucket Histogram for Estimating the Selectivity of Spatial Selection and Spatial Join

在线全文

学校读者我要写书评

暂无评论

Geo-Spatial Information Science 2011年第4期14卷 262-273页

作者： Changxiu Cheng chenghu zhou Rongguo Chen State Key Laboratory of Resources and Environmental Information Systems Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences

Selectivity estimation is crucial for query optimizers choosing an optimal spatial execution plan in a spatial database management *** paper presents an Annular Bucket spatial histogram(AB histogram)that can estimate the selectivity in finer spatial selection and spatial join operations even when the spatial query has more operators or more *** AB histogram is represented as a set of bucket-range,bucket-count value *** bucket-range often covers an annular region like a sin-gle-cell-sized photo *** bucket-count is the number of objects whose Minimum Bounding Rectangles(MBRs)fall between outer rectangle and inner rectangle of the *** that all MBRs in each a bucket distribute evenly,for every buck-et,we can obtain serial probabilities that satisfy a certain spatial selection or join conditions from the operations' semantics and the spatial relations between every bucket-range and query ***,according to some probability theories,spatial selection or join selectivity can be estimated by the every bucket-count and its *** paper also shows a way to generate an updated AB histogram from an original AB histogram and those *** tests show that the AB histogram not only supports the selectivity estimation of spatial selection or spatial join with "disjoint","intersect","within","contains",and "overlap" operators but also provides an approach to generate a reliable updated histogram whose spatial distribution is close to the distribution of ac-tual query result.

关键词： selectivity estimation AB histogram annular bucket spatial selection spatial join

Comparision of Methods for Polarimetric SAR Tomography with Small Number of Baselines in Forested Areas

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2019年第5期28卷 1073-1079页

作者： LIANG Lei zhou chenghu LI Xinwu GAO Xizhang WU Wenjin State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Key Laboratory of Digital Earth Sciences Institute of Remote Sensing and Digital Earth (RADI) Chinese Academy of Sciences

Synthetic aperture radar Tomography(TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. However, the more multi-baselines acquisition, the longer the time span of acquisition, which will result in serious temporal decorrelation in forested area. In this way, we expect to use as smaller number of baselines as possible to obtain high estimation accuracy in elevation direction. We thus investigate the performance of Polarimetric SAR tomography(Pol-TomoSAR) with small number of baselines in forested areas. The results show that compressive sensingbased Pol-TomoSAR has higher estimation accuracy in elevation direction than conventional Pol-TomoSAR with small number of baselines.

关键词： Synthetic aperture radar(SAR) Polarimetric SAR SAR tomography Compressive sensing