中坝隧道地下分水岭演化的数值模拟分析     

廖晓超  许模  蒋莉  赵瑞  苟敬 《地下水》2014,(1):48-49,52

由于铁路隧道的施工,地下水进入隧道,形成了新的排泄基准面,对区域地下水环境产生较大影响,故对该类问题进行深入研究具有重要的工程实践意义。以中坝岩溶隧道为例,采用Visual modflow对中坝隧道进行三维数值模拟,模拟中坝隧道开挖建设后,地下分水岭的演化过程,以此来探讨分析其对地下水环境的影响。  相似文献   

Analysis of the microclimate and CO2 flux characteristics in arid desert wetland ecosystem in summer: A case study in Xihu desert wetland,Dunhuang, China     

Qian-Qian Gou  Jian-Jun Qu  Zhi-Wen Han 《Journal of Earth System Science》2014,123(7):1491-1499

Xihu desert wetland is an important and unusual environment in China or even in the world. However, until now, little research has been focused on the microclimate and CO₂ flux characteristics in this area. This paper reports the characteristics of daily variations of microclimate and CO₂ flux in the Dunhuang Xihu desert wetland, based on data observed in the desert wetland during a period of continuous fine weather in summer 2012. Results indicate that the characteristics of the micrometeorology were significantly affected by the land–lake breeze during the study period, and updrafts were prevalent in this region. The friction wind speed and the vertical velocity were much greater than those in the Maqu grasslands. The energy budget was strongly imbalanced: the latent heat flux was significantly higher than the sensible flux. The daily mean values of total solar radiation and net radiation were larger than those in Maqu grasslands and Jinta oasis. There was a temperature inversion and inverse humidity gradient in the atmospheric surface layer at night. The desert wetland ecosystem was a carbon sink during the whole of the observation period, and the maximum rate of carbon absorption usually occurred at about 11:00 hr each day in this region.  相似文献   

珠江三角洲地区城中村土地供求的动态均衡分析     

魏开  许学强 《热带地理》2012,32(4):416-422

土地问题是我国城中村研究的核心问题。在对珠江三角洲地区城中村进行实地调研的基础上,就城中村主体的行为特征、城中村土地供应和需求的基本特征进行了总结。以理论推导与现实印证相结合的方法,基于经济学中的供求理论,对城中村土地供求变化进行了动态均衡分析。从村庄"内部人"的视角,考察在各种内外部因素变动(征地与留用地,城中村改造,村民城市化转型)的情况下,城中村主体如何实现土地的供应和需求均衡。总体上,城中村土地变化表现为土地需求被动地追随(因征地而发生的)供应减少而下降,以实现供求均衡。具体而言,在城中村形成阶段,供求均衡借助乡村工业化,即农业用地转为工业用地而实现;在城中村存续阶段,存在土地供求的逐渐失衡;在城中村改造阶段,供求均衡最终必须通过城市化,即村民转为市民而实现。  相似文献   

Precipitation variability during the past 400?years in the Xiaolong Mountain (central China) inferred from tree rings   总被引：3，自引：0，他引：3  

Keyan Fang  Xiaohua Gou  Fahu Chen  David Frank  Changzhi Liu  Jinbao Li  Miklos Kazmer 《Climate Dynamics》2012,39(7-8):1697-1707

We developed the first tree-ring chronology, based on 73 cores from 29 Pinus tabulaeformis trees, for the Xiaolong Mountain area of central China, a region at the boundary of the Asian summer monsoon. This chronology exhibits significant (at 0.01 level) positive correlations with precipitation in May and June, and negative correlations with temperature in May, June and July. Highest linear correlation is observed between tree growth and the seasonalized (April–July) precipitation, suggesting that tree rings tend to integrate the monthly precipitation signals. Accordingly, the April–July total precipitation was reconstructed back to 1629 using these tree rings, explaining 44.7?% of the instrumental variance. A severe drought occurred in the area during the 1630s–1640s, which may be related to the weakened Asian summer monsoon caused by a low land-sea thermal gradient. The dry epoch during the 1920s–1930s and since the late 1970s may be explained by the strengthened Hadley circulation in a warmer climate. The dry (wet) epochs of the 1920s–1930s (the 1750s and 1950s) occurred during the warm (cold) phases of the El Ni?o-Southern Oscillation and the Pacific Decadal Oscillation that are often associated with weakened (strengthened) East Asian summer monsoon. These relationships indicate significant teleconnections operating over the past centuries in central China related to large-scale synoptic features.  相似文献   

Spatial drought reconstructions for central High Asia based on tree rings     

Keyan Fang  Nicole Davi  Xiaohua Gou  Fahu Chen  Edward Cook  Jinbao Li  Rosanne D’Arrigo 《Climate Dynamics》2010,35(6):941-951

Spatial reconstructions of drought for central High Asia based on a tree-ring network are presented. Drought patterns for central High Asia are classified into western and eastern modes of variability. Tree-ring based reconstructions of the Palmer drought severity index (PDSI) are presented for both the western central High Asia drought mode (1587–2005), and for the eastern central High Asia mode (1660–2005). Both reconstructions, generated using a principal component regression method, show an increased variability in recent decades. The wettest epoch for both reconstructions occurred from the 1940s to the 1950s. The most extreme reconstructed drought for western central High Asia was from the 1640s to the 1650s, coinciding with the collapse of the Chinese Ming Dynasty. The eastern central High Asia reconstruction has shown a distinct tendency towards drier conditions since the 1980s. Our spatial reconstructions agree well with previous reconstructions that fall within each mode, while there is no significant correlation between the two spatial reconstructions.  相似文献   

Machine-Learning-Aided Determination of Post-blast Ore Boundary for Controlling Ore Loss and Dilution     

Yu  Zhi  Shi  Xiuzhi  Zhou  Jian  Gou  Yonggang  Rao  Dijun  Huo  Xiaofeng 《Natural Resources Research》2021,30(6):4063-4078

Natural Resources Research - In the process of open-pit bench blasting for many mines, rock fragments move in the direction of loose space after fragmentation under explosive energy, leading to ore...  相似文献   

Identification of paralytic shellfish toxin-producing microalgae using machine learning and deep learning methods     

Xu  Wei  Niu  Jie  Gan  Wenyu  Gou  Siyu  Zhang  Shuai  Qiu  Han  Jiang  Tianjiu 《中国海洋湖沼学报》2022,40(6):2202-2217

Journal of Oceanology and Limnology - Paralytic shellfish poisoning (PSP) microalgae, as one of the harmful algal blooms, causes great damage to the offshore fishery, marine culture, and marine...  相似文献   

即墨地区莱阳群底部止凤庄组地质特征及其碎屑锆石LA-ICP-MS U-Pb年龄地质意义          下载免费PDF全文

朱学强  杨仕鹏  任天龙 《山东国土资源》2016,32(2)

为了了解盆地沉积初期的物源特征,对位于胶莱盆地东缘即墨地区早白垩世莱阳群止凤庄组沉积特征、物质组成及碎屑锆石进行了U-Pb同位素测年研究。野外调查表明,止凤庄组为一套陆源碎屑沉积,具有近源沉积的特点。南泊一带止凤庄组底部碎屑岩碎屑锆石LA-ICP-MS U-Pb年龄介于233~734 Ma,年龄分布于5个区间,呈现明显的幕式特征,至少记录了2次重要的构造热事件。侵入于止凤庄组石英二长岩的锆石U-Pb加权平均年龄为(123.50±0.95)Ma,限定了止凤庄组地层沉积上限年龄为123.50 Ma。综合分析认为,止凤庄组物源主要来自苏鲁造山带,部分来自扬子板块。这有助于了解胶莱盆地沉积初期其物源区苏鲁造山带的地体情况。  相似文献   

浅析张集矿立井地面预注浆堵水效果     

王秀河  张学强  姚南山 《安徽地质》1999,(1)

介绍了张集矿立井基岩段水文地质和基岩地面预注浆的有关情况。根据井简实测资料,分析基岩裂隙的发育规律、裂隙层界面的浆波充填情况、实际浆液有效扩散半径及堵水效果。认为：立井基岩地面预注浆,不仅能成功地起到堵水的自的．从而缩短工期、降低造价、提高质量,而且还有利于井筒安全揭穿突出谋层,达到安全施工。  相似文献   

Pacific decadal oscillation impact on East China precipitation and its imprint in new geological documents     

Jiahui Yao  Linxiang Xiao  Mengmeng Gou  Chao Li  Ergang Lian  Shouye Yang 《中国科学:地球科学(英文版)》2018,61(4):473-482

This paper briefly introduces the history of the study of the Pacific decadal oscillation (PDO) and explores the relationship between the PDO and sediment grain size from two typical sediment cores from the lower Changjiang (Yangtze River) and Huanghe (Yellow River) estuaries. It is found that the median grain sizes of both cores exhibit relatively high correlation with the PDO. This is because the PDO causes interdecadal variability of precipitation in the East Asia Monsoon region, thus changing the hydrodynamics in both the Changjiang and Huanghe catchments, eventually resulting in variation of sediment grain size. Our analysis also revealed that during different phases of the PDO, the sediment grain size of the Changjiang and Huanghe estuaries showed different variations in cold and warm PDO phases. This is related to movement of the precipitation center driven by the shift in different PDO phases. Moreover, we compared more high resolution geological proxies with the PDO, including stalagmites and tree rings, in East China over the past century. The results indicate that variations of studied geological proxies are generally well correlated with the PDO but have some differences. Finally, longer variations of sediment grain sizes in the Changjiang and Huanghe estuaries are compared with a reconstructed PDO over the last 200 years; sediment grain sizes were still correlated with the PDO, implying that sediment grain size may be used as a new proxy for studying the long-term behavior of the PDO. This result supports previous knowledge of the PDO impact on East China climate evolution and offers a new proxy for further PDO study. Our study will improve paleoenvironment reconstruction in East China on a decadal time scale and benefit future climatic predictions.  相似文献