A tree-ring based precipitation reconstruction for the Mohe region in the northern Greater Higgnan Mountains,China, since AD 1724     

Tongwen Zhang  Yujiang YuanWenshou Wei  Shulong YuRuibo Zhang  Feng ChenHuaming Shang  Li Qin 《Quaternary Research》2014

August–July precipitation has been reconstructed back to AD 1724 for the Mohe region in the northern Greater Higgnan Mountains, China, using Pinus sylvestris var. mongolica tree-ring width. The reconstruction explains 39% of the variance in the precipitation observed from AD 1960–2008. Some droughts noted in historical documents are precisely captured in our reconstruction. Wet periods occurred during the periods of AD 1734–1785, AD 1805–1830, AD 1863–1880, AD 1922–1961, and AD 1983–1998; while the periods of AD 1786–1804, AD 1831–1862, AD 1881–1921, and AD 1962–1982 were relatively dry. Power spectral and wavelet analyses demonstrated the existence of significant 24-yr, 12-yr, and 2-yr cycles of variability. The results of the spatial correlations suggest that our reconstruction contains climatic signals for the southern Stanovoy Range and the northern Greater Higgnan Mountains. The positive correlations between the new reconstructed precipitation series and two precipitation reconstructions indicate that our precipitation reconstruction captures broad-scale regional climatic variations. A comparison between the weakening tendency of summer monsoon and the dry period of our reconstruction reveals that the annual precipitation in the Mohe region is partly influenced by the East Asian Summer Monsoon.  相似文献   

断层输导作用与油气充注作用关系分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘震  张旺  曹尚  刘明洁  张威  董冬 《地质科学》2014,49(4):1302-1313

断层是控制油气藏形成的重要因素之一;断层的开启及闭合影响到油气运移与聚集的效率。但油气在断层中的运移与在砂层中的充注存在差异性这一问题长期被忽视。一般认为;只要发育断层;其断开的渗透层就会被油气充注;极少关注地层水和石油的压缩特性对充注的影响。本文提出;地下单断层活动时;深部油气在超压作用下以涌流方式难以快速充注进入中浅层被切割的砂体;因此;单砂体至少要存在一条断层作为泄水出口;石油才能通过其余断层充注进入砂体;即单砂体要发育两条及两条以上断层;石油才能注入砂体。在断层静止期;油气通过渗流方式沿特定深度范围断面垂向运移;对油气垂向运移距离影响较小。本文运用4个大型盆地的典型油气藏与断层分布关系讨论了本文观点。该观点对油气成藏规律研究及成藏目标评价有较重要参考意义。  相似文献   

中国萤石矿床分类   总被引：7，自引：0，他引：7       下载免费PDF全文

王吉平商朋强  熊先孝杨辉艳 唐尧 《中国地质》2014,41(2):315-325

通过对中国萤石矿床的成矿作用研究,综合考虑萤石矿床的成因类型和工业类型,将中国萤石矿床划分为沉积改造型、热液充填型和伴生型3种矿床类型。在全面分析萤石矿典型矿床的成矿条件、控矿因素和成矿作用的基础上,总结成矿要素,以相同或相似的二级成矿必要要素组合确定沉积改造型、热液充填型萤石矿床的亚类型,沉积改造型进一步划分出2个矿床式,热液充填型划分出5个矿床式,伴生型按伴生主矿种划分出4个矿床式。文章分析了每一个矿床式的成矿地质背景,成矿条件、矿床特征、控矿因素和成矿作用,总结了每一个矿床式的二级成矿必要要素。  相似文献   

“雷霆扫毒”对贩卖毒品犯罪的影响及后续时空分布变化——以ZG市主城区为例     

柳林  刘慧婷  陈建国  肖露子  祝卫莉  孙秋远 《地理学报》2022,77(6):1461-1474

贩卖毒品是实现毒品犯罪经济利益的重要环节,是危害最为严重的毒品犯罪类型之一。现有研究主要关注毒品犯罪与建成环境之间的关系,没有顾及打击后贩卖毒品犯罪空间转移现象以及影响因素的变化。本文基于日常活动理论、犯罪模式理论和社会解组理论,以中国ZG市主城区为例,融合多源时空数据,分别对2013年8月开始的“雷霆扫毒”前后的贩卖毒品犯罪构建负二项回归模型,分析微观尺度下半公共空间、室外公共空间和室内私人空间对贩卖毒品犯罪影响的变化。研究发现“雷霆扫毒”行动后：① 贩卖毒品犯罪案件数量显著下降;② 半公共空间对贩卖毒品犯罪的影响作用减弱;③ 室外公共空间对贩卖毒品犯罪影响作用增强,室内私人空间对贩卖毒品犯罪的影响上升。结果表明：“雷霆扫毒”专项行动开展后一年,贩卖毒品犯罪的“主阵地”发生变化,由城市半公共空间逐渐向室外公共空间和室内私人空间转移。特别的是,“雷霆扫毒”对大毒枭及贩毒团伙的打击成效突出,促使2014年贩毒案件大幅度下降,实现了专项行动开展的目的。后续一系列专项行动进一步提升了对贩卖毒品犯罪的发现和查处能力,显示出专项行动对打击隐性犯罪的明显效果。研究表明公安执法部门必须对毒品贩卖犯罪进行持续的、有针对性的打击,对发生地的变动进行定期的监控,不能一蹴而就。  相似文献   

高浓度气体共振光声光谱信号饱和特性研究     

袁长迎  炎正馨  蒙瑰  李智慧  尚丽平 《海洋学报》2010,32(10):6908-6913

采用恒流驱动耦合机械斩波技术在激光光声光谱装置上系统测量了5%—100%宽浓度范围甲烷气体的共振光声信号,发现在高浓度区共振光声信号呈现异常的饱和特征.基于气体吸收和光声光谱原理定量分析了光声信号饱和的主要原因及影响因素,研究表明,气体样本对入射光强吸收而导致的声源与本征共振模式的耦合系数改变是异常饱和的主要原因,并导出判定光声信号饱和深度的准则以用于判定高浓度气体饱和深度.  相似文献   

2003年北极科考期间一次极涡个例天气学分析     

隋翠娟  孙兰涛  孟上  王咏亮  吴辉碇 《海洋学报》2010,32(4):51-61

2003年9月3日到14日,"雪龙"号考察船进入北冰洋楚科奇海观测期间,正值一次典型的北极极涡环流过程形成和发展。以往研究大多集中于极涡的平均水平环流特征和季节变化,该例为我们研究它的瞬时环流形势和特征提供了条件。利用NCEP全球分析资料及第二次北极科考资料对这次个例进行天气学分析,通过描述极涡个例的发展情况,平流层、对流层的环流特征以及二者之间的关系,并分析卫星遥感图像及"雪龙"号考察船的气象资料,分析结果发现:2003年中国第二次北极科考期间经历的极涡形成和发展,典型地表现出极地冬夏环流型的转换过程。首先在平流层发生,然后向对流层传播,该个例是一次在平流层西退加强,在对流层东移南下的过程。  相似文献   

Simulated various characteristic waves in acoustic full waveform relating to cement bond on the secondary interface     

Hongbing Zhang  Danyan Xie  Zuoping Shang  Xuebing Yang  Hongjian Wang  Honggen Tao 《Journal of Applied Geophysics》2011,73(2):139-154

Bad cement bond with water channeling or low strength cement is usually generated on the first and/or secondary interfaces which lie between the cement and casing, and the cement and formation, respectively. It is an inherently complicated problem to evaluate cement bond on the secondary interface (SICB) in a cased borehole. So we need to find a useful wave for evaluating SICB and provide its propagation features. To achieve this, we simulated the acoustic full waveform, 2-D spectrum and dispersion curves in cased boreholes based on the real axis integration method, and a propagator matrix. Simulation results indicated that “casing-cement mode” wave can be utilized to evaluate SICB, as it is most sensitive to water channeling on the secondary interface. Velocity of this mode wave is in between that of the casing wave and the formation wave, so that it is easy to extract it in time. The dispersion curves showed that the casing-cement wave is a dispersion wave, but not a pseudo-Rayleigh wave. Its velocity is obviously larger than v_s of cement. Simulation results further indicated that the amplitude of casing-cement wave is decreasing with increasing cement sheath thickness, but not water channeling thickness, and its travel time is influenced by casing and cement together. Moreover, we investigated factors influencing the casing–cement wave and found that casing diameter and peak frequency are major factors influencing the amplitude and the travel time, while other factors, such as P-wave velocities of cement and wall thickness of casing, are minor factors. But none of these factors greatly influence bond index which is computed from the amplitude. So the bond index has an advantage over the amplitude during evaluating SICB. Formation wave is a helpful signal to evaluate low strength cement without water channeling, and its amplitude is mainly related to the velocities (or impedances) of both cement and formation except for formation attenuation and disturbance wave. Experimental data in calibration pits and field data detecting channeling demonstrated the simulation results.  相似文献   

Integration of optical and Synthetic Aperture Radar (SAR) imagery for delivering operational annual crop inventories     

Heather McNairn  Catherine Champagne  Jiali Shang  Delmar Holmstrom  Gordon Reichert 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(5):434-449

Agriculture plays a critical role within Canada’s economy and, as such, sustainability of this sector is of high importance. Targeting and monitoring programs designed to promote economic and environmental sustainability are a vital component within Canada’s agricultural policy. A hierarchy of land information, including up to date information on cropping practices, is needed to measure the impacts of programs on land use decision-making and to gauge the environmental and economic benefits of these investments. A multi-year, multi-site research activity was completed to develop a robust methodology to inventory crops across Canada’s large and diverse agricultural landscapes. To move towards operational implementation the methodology must deliver accurate crop inventories, with consistency and reliability. In order to meet these operational requirements and to mitigate risk associated with reliance on a single data source, the methodology integrated both optical and Synthetic Aperture Radar (SAR) imagery. The results clearly demonstrated that multi-temporal satellite data can successfully classify crops for a variety of cropping systems present across Canada. Overall accuracies of at least 85% were achieved, and most major crops were also classified to this level of accuracy. Although multi-temporal optical data would be the preferred data source for crop classification, a SAR-optical dataset (two Envisat ASAR images and one optical image) provided acceptable accuracies and will mitigate risk associated with operational implementation. The preferred dual-polarization mode would be VV–VH. Not only were these promising classification results repeated year after year, but the target accuracies were met consistently for multiple sites across Canada, all with varying cropping systems.  相似文献   

基于ArcGIS的土地利用现状图的编制   总被引：1，自引：0，他引：1  

韩尚 《地理空间信息》2009,7(6):130-132

提出了基于ArcGIS的土地利用现状图编制的整体思路,对其中关键技术的实现进行了详细的阐述。  相似文献   

THE CORRESPONDING ANALYSIS OF HEAVY-METAL POLLUTION OF SOIL IN ZHUZHOU CITY   总被引：1，自引：0，他引：1  

尚金城  龙爱民  李斌  姜建祥 《中国地理科学(英文版)》1996,6(2):177-184

ＴＨＥ ＣＯＲＲＥＳＰＯＮＤＩＮＧ ＡＮＡＬＹＳＩＳ ＯＦ ＨＥＡＶＹ－ＭＥＴＡＬ ＰＯＬＬＵＴＩＯＮ ＯＦ ＳＯＩＬ ＩＮ ＺＨＵＺＨＯＵ ＣＩＴＹ ＳｈａｎｇＪｉｎｃｈｅｎｇ（尚金城）；ＬｏｎｇＡｉｍｉｎ（龙爱民）ＬｉＢｉｎ（李斌）；ＪｉａｎｇＪ...  相似文献