检索结果-南通市图书馆

Reconstruction of precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2005年第7期48卷 939-949页

作者： SHAO Xuemei1, HUANG Lei1, LIU Hongbin2, LIANG Eryuan1, FANG Xiuqi3.& WANG Lili1 1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 100101, china 2. National Climate Center, beijing 100081, china 3. beijing normal university, beijing 100875, china Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing 100101 China National Climate Center Beijing 100081 China beijing normal university Beijing 100875 China

Using seven well-replicated Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies developed at Zongwulong and Shalike Mts. in the northeastern part of the Qaidam Basin annual precipitation from previous July to current June in the recent 1000 years was re- constructed for Delingha. The reconstruction can capture 63.1% of precipitation variance and the equation was stable over time. For the reconstructed precipitation, wet periods occurred in AD1520—163. and 193.—2001, whereas dry intervals in 1429—1519 and 163.—1741. In ad- dition, the magnitude in precipitation variation was lower before 143. with about 15 mm, but it increased to 3. mm during the period of 143. to 1850. After 1850, the precipitation variance de- creased again. In contrast to the increase in temperature, a decrease in annual precipitation was evident since the 1990s. The agreement in low-frequency variation between the reconstruction and the glacier accumulation and particulate content in Dunde ice cores during the recent several hundred years suggested that the precipitation reconstructed in this study was rather reliable, and represented a regional signal. This 1000-year reconstruction could benefit our understanding of climatic variation in decadal to century-scale in this region, and provide basic data to climate models and to prediction of future climate in the 21st century.

关键词： northeastern part of the Qaidam Basin tree-ring width series of Qilian juniper precipitation reconstruction in 1000 years.

Geographical Agglomeration of Chinese Manufacturing Industries

在线全文

学校读者我要写书评

暂无评论

中国人口·资源与环境：英文版 2007年第2期5卷 3-11页

作者： Zhang Hua 1, 2, Zheng Wei3.1. Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 100101, china 2. Graduate School of the Chinese Academy of Sciences, beijing 10003., china 3. School of Geography, beijing normal university, beijing 100875, china Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China School of Geography Beijing Normal University Beijing 100875 China

Based on the plant level data from the First National Census of Basic Units, the Second National Census of Basic Units, and the First National Economic Census of china, this paper ex- amines the geographical agglomeration of Chinese manufacturing industries at a more disaggregated level both by industrial classi-fication and spatial unit analysis. Applying the agglomeration index proposed by Maurel and Sedillot, studies show that the most agglomerated industries are resource-intensive, and capital and technology intensive while industries demanding localized inputs or serving localized markets or favored by local governments are fairly dispersed. The more disaggregated industries are more spa- tially agglomerated. At the finer spatial scale, industries are more dispersed. Results indicate that within-county spillovers are stronger than nearby-county spillovers, and within-prefecture spillovers are stronger than nearby prefecture spillovers. Local- ized spillovers are still quite substantial at a range beyond that of counties. Comparing the agglomeration index of Chinese manu- facturing industries in 1996, 2001 and 2004, agglomeration seems to be a general tendency. Results also indicate that some industries have experienced remarkable changes in their levels of agglom- eration in the period 1996–2004.

关键词： industrial agglomeration manufacturing industries the MS index

Study on the changes of water cycle and its impacts in the source region of the Yellow River

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2004年第Z1期47卷 142-151页

作者： ZHANG Shifeng1, JIA Shaofeng1, LIU Changming1, CAO Wenbing2, HAO Fanghua3. LIU Jiuyu4 & YAN Huayun5 1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 100101, china 2. china {3. of Geosciences, beijing 100083. china 3. beijing normal university, beijing 100875, china 4. Bureau of Hydrology of Yellow River Conservancy Commission, Zhengzhou 450003. china 5. Bureau of Hydrology and Water Resource Investigation of Qinghai Province, Xining 810001, china Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China china university of Geosciences Beijing China beijing normal university Beijing China Bureau of Hydrology of Yellow River Conservancy Commission Zhengzhou China Bureau of Hydrology and Water Resource Investigation of Qinghai Province Xining China

The water cycle in the source region of the Yellow River underwent great changes in the 1990s. The major features of the changes are as follows: the gauged runoff declined significantly while the precipitation increased slightly, and the runoff process was more concentrated on the flood season. Water balance analyses indicate that the pondage was kept in the status of negative equilibrium, causing eco-environmental problems. The runoff decrement is due to evaporation increment in this region. Studies show that the runoff process in this region is closely related to that of the other hydrological stations in the upper reaches. When the runoff declines in the source regions, the amount of water also declines in the whole upper reaches of the Yellow River, affecting the balance between water demand and supply. Meanwhile changes will take place in the water cycle of the river course system when the eco-environment deteriorates. The trend of water cycle change in the source region is that the runoff will keep declining with the increment of evaporation caused by temperature rise in the northwest of china in the 21st century. But the hydraulic engineering in the source region will help to mitigate the deterioration of local eco-environment system, though the impacts to the lower reaches of this project may not be the case.

关键词： source region of the Yellow River, water cycle, evaporation, negative equilibrium.

Key points on temperature change of the past 2000 years in china

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2004年第8期 82-89页

作者： GE Quansheng 1, ZHENG Jingyun 1*, MAN Zhimin 2, FANG Xiuqi 3.1 and ZHANG Piyuan 1(1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 100101, china 2. Institute of Chinese History Geography, Fudan university, Shanghai 20043., china 3. School of Geography, beijing normal university, beijing 100875, china) Institute of Geographic Sciences and Natural Resources Research，Chinese Academy of Sciences，beijing 100101，china Institute of Chinese History Geography，Fudan university，Shanghai 20043.，china School of Geography，beijing normal university，beijing 100875，china Institute of Geographic Sciences and Natural Resources Research，Chinese Academy of Sciences，beijing 100101，china

Temperature change of the past 2000 years in china is discussed based on the winter half-year temperature series of the past 2000 years in eastern china reconstructed recently, and other related studies. The main conclusions are as follows: (1) The Little Ice Age (LIA) in china began in the early of the 14th century (13.0s) and ended in the beginning of the 20th century (1910s), which was composed of four evident cold stages and three short warming stages. The cold period in the Wei, Jin and South-North dynasties (210s～560s) was the only one comparable with LIA for the past 2000 years. (2) The Medieval Warm Period (MWP) in china began in the 93.s and ended in the 13.0s, which was composed of two warm stages over 100 years and a cold stage less than 100 years. (3. The climate in the Sui and Tang dynasties should be divided into two stages: the climate in the 570s～770s was as warm as that in the 20th century; while the temperature in the 780s～920s was lower than that in the 1950s～1970s. (4) In eastern china as a whole, winter half-year temperature variation with over 1 ℃ occurred between the cold and warm stages on centennial scale, while the changing rate exceeded 1.0 ℃ per century. (5) There exists an about 13.0-year periodicity in the historical temperature change. Inferred from the periodicity, the most likely historical analogue for the warming in the 20th century is the warm stage of the Sui and Tang dynasties (570s～770s), instead of the Medieval Warm Period. (6) Although it was critically warm, the temperature of the 20th century in eastern china is still within the threshold of the variability of the last 2000 years.

关键词： eastern china past 2000 years temperature change.

Quasi-periodicity of temperature changes on the millennial scale

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2003年第8期 43-48页

作者： GE Quansheng, FANG Xiuqi and ZHENG Jingyun (1. Department of Geography, Lanzhou university, Lanzhou 73.000, china 2. Institute of Geographical Science and Resources Research, Chinese Academy of Sciences, beijing 100101, china 3. Department of Geography, beijing normal university, beijing 100875, china)

Quasi-periodicity of temperature changes on the millennial scale is found according to the proxy data both from historicaldocuments and natural evidence in china. The auto-correlation of the temperature changes series for the last 2000 years is most significanton the 13.0 a time lag. The period of 13.0 a includes 4 warm/cold stages: 200～250 a warm stage, 150～200 a cold stage, 3.0～3.0 awarm stage, and 550～600 a cold stage. In contrast to the 550～600 a cold stage, the other three stages can be united in one warm domi-nant stage. Inferred from the 13.0 a period, the 20th century warm stage belongs to the 200～250 a warm stage, which is similar to thewarm stage occurring during the 570's～770's. The process of temperature change in the 20th century warm stage is similar to that ofthe 570's～770's. But the warming rate in the 20th century is more rapid. The temperature anomaly in the 1980's～1990's shows agreater departure from the regression equation of that between 1500' s～1900's and 150's～650' s. W

关键词： quasi-periodicity temperature change millennial scale the period of 13.0a.

Neutron activation analysis and Mdssbauer spectroscopy research on coloring mechanism of ancient Chinese Guan porcelain

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2000年第20期45卷 1840-1844页

作者： ZHAO Weijuan, LI Guoxia, GAO Zhengyao, ZHANG bin, LI Rongwu, WU Xiaoli, YAO Guifang, JIA Xiuqin, HAN Song & HUANG Zhongxiang1. Department of Physics, Zhengzhou university, Zhengzhou 450052, china 2. Department of Architecture, Zhengzhou Technology university, Zhengzhou 450002, china 3. Department of Physics, beijing normal university, beijing 100875, china 4. Hangzhou Museum of Guan kiln, Hangzhou 3.0008, china 5. Institute of High Energy Physics, Chinese Academy of Sciences, beijing 100080, china

The content of 3. kinds of coloring elements in Guan porcelain in the Southern Song Dynasty has been determined by neutron activation analysis (NAA). Iron is the major coloring element. Mossbauer spectroscopy has shown that the iron of the glaze exists in the form of structural iron (Fe2+, Fe3.). The quantitative relationship between the main wavelength of every color glaze and the relative content (Fe2+/Fe3.) of structural iron has been determined. Thus the coloring mechanism of Guan porcelain in the Southern Song Dynasty has been revealed entirely.

关键词： coloring mechanism of Guan porcelain in Southern Song Dynasty characteristic spectrum NAA Mossbauer spectroscopy.

Recommendation Method for Contrastive Enhancement of Neighborhood Information

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第1期78卷 453-472页

作者： Hairong Wang beijing Zhou Lisi Zhang He Ma School of Computer Science and Engineering North Minzu UniversityNingxia750021China

Knowledge graph can assist in improving recommendation performance and is widely applied in various person-alized recommendation ***,existing knowledge-aware recommendation methods face challenges such as weak user-item interaction supervisory signals and noise in the knowledge *** tackle these issues,this paper proposes a neighbor information contrast-enhanced recommendation method by adding subtle noise to construct contrast views and employing contrastive learning to strengthen supervisory signals and reduce knowledge ***,first,this paper adopts heterogeneous propagation and knowledge-aware attention networks to obtain multi-order neighbor embedding of users and items,mining the high-order neighbor informa-tion of users and ***,in the neighbor information,this paper introduces weak noise following a uniform distribution to construct neighbor contrast views,effectively reducing the time overhead of view *** paper then performs contrastive learning between neighbor views to promote the uniformity of view information,adjusting the neighbor structure,and achieving the goal of reducing the knowledge noise in the knowledge ***,this paper introduces multi-task learning to mitigate the problem of weak supervisory *** validate the effectiveness of our method,experiments are conducted on theMovieLens-1M,MovieLens-20M,Book-Crossing,and Last-FM *** results showthat compared to the best baselines,our method shows significant improvements in AUC and F1.

关键词： Contrastive learning knowledge graph recommendation method

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

内蒙古农牧业系统的能值动态分析与评价

生态经济(学术版) 2008年第1期 171-174页

作者：董云杨凌志张玉芳董孝斌云南国土资源职业学院中国农业大学区域农业研究中心北京师范大学资源学院北京师范大学资源学院昆明6502173 北京100094 北京100875

内蒙古1985年、1995年和2003.不同年份的农牧业系统能值分析表明,环境资源对内蒙古农牧业的发展影响巨大。不可更新的工业辅助能值呈较大幅度增长,但仍处于较低水平。农牧业系统的净能值产出率呈逐年递减的趋势,环境负载率呈不断升高... 详细信息

内蒙古1985年、1995年和2003.不同年份的农牧业系统能值分析表明,环境资源对内蒙古农牧业的发展影响巨大。不可更新的工业辅助能值呈较大幅度增长,但仍处于较低水平。农牧业系统的净能值产出率呈逐年递减的趋势,环境负载率呈不断升高的趋势,农牧业系统目前发展的可持续性比较差。内蒙古农牧业系统的农畜产品产出能值有较大的提高。以耗粮为主的猪肉产出能值的比重虽然呈下降的趋势,但依然占了总畜产品产出能值的一半左右。内蒙古奶类的能值产出呈较快增长趋势。建议将农业结构的调整与生态环境建设结合起来,形成以草为中心的战略调整,加强政府的宏观调控和管理水平。

关键词：内蒙古能值农牧系统分析评价

Functional central limit theorem for super α-stable processes

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 Mathematics 2004年第6期47卷 874-881页

作者： HONG WenmingDepartment of Mathematics, beijing normal university,{3., china Department of Mathematics Beijing Normal University Beijing China

A functional central limit theorem is proved for the centered occupation time process of the super α-stable processes in the finite dimensional distribution sense. For the intermediate dimensions α < d < 2α (0 < α ≤ 2), the limiting process is a Gaussian process, whose covariance is specified; for the critical dimension d= 2α and higher dimensions d < 2α, the limiting process is Brownian motion.

关键词： super α-stable processes occupation time central limit theorem evolution equation