广州地铁沉降监测方法及数据处理

广州是轨道交通工程在建项目较多的城市,沉降监测对地铁工程的安全施工有着重要意义,同时监测数据能够直接用来评价地铁施工对地表环境的影响.重点论述了广州地铁沉降监测的方法与技术要求,阐述了数据处理和统计分析;并给出了变形预报分析的数学方法,说明了其现实意义.     

Impact of the El Nino on the Variability of the Antarctic Sea Ice Extent

1　IntroductionManymeteorologistsandoceanographerspaidmuchattentiontothestudyofthemechanismofENSOformanyyears,suchasBjerknes(1 966) ,Wyrtki(1 975) ,McCreary(1 983 ) ,Philander(1 984) ,ZhangandChao(1 993 )andMcCPhaden(1 998)havemadegreatdevelopmentinthestudyofENSO .Especiallyinthe 1 990’s,withtheincreasingofthedatainthedeepocean ,thesomeonearguedthattheENSOepisodehadcloserelation shipwiththeeasterntransportationoftheanomalousseasurfacetemperatureinthewestPacific(LiandMu 1 999;Huang 2…     

内蒙古白乃庙铜矿区含矿中酸性侵入岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及成矿时代

为了限定白乃庙铜矿的成矿时代和成矿环境,对含矿中酸性岩类进行同位素年龄和岩石地球化学研究。获得的3个含矿花岗闪长岩样品的LA-MC-ICP-MS锆石U-Pb年龄分别为421.5±1.8Ma、438.6±3.4Ma和459.3±3.6Ma。含矿中酸性岩类属于过铝质钙碱性系列岩石,稀土元素曲线显示为轻稀土元素富集型,具有弱正Eu异常,微量元素曲线表现为明显的Ta、Nb亏损。综合含矿中酸性岩类时代、地球化学特征及区域构造背景,认为白乃庙铜矿总体形成于早古生代,具有多期成矿的特点,成矿作用与古蒙古洋早古生代俯冲消减事件有关。     

Impacts of riparian zone plant water use on temporal scaling of groundwater systems

In this work, we study groundwater system temporal scaling in relation to plant water use and near‐river‐stage fluctuations in riparian zones where phreatophytes exist. Using detrended fluctuation analysis (DFA), we investigate the influence of regular diurnal fluctuations due to phreatophyte water use on temporal scaling properties of groundwater level variations. We found that groundwater use by phreatophytes, at the field site on the Colorado River, USA, results in distinctive crossovers (slope changes when the plots are fitted with straight lines) in the logarithm plots of root‐mean‐square fluctuations of the detrended water level time series versus time scales of groundwater level dynamics. For groundwater levels monitored at wells close to the river, we identified one crossover at ～1 day in the scaling characteristics of groundwater level variations. When time scale exceeds 1 day, the scaling properties decrease from persistent to close to 1/f noise, where f is the frequency. For groundwater levels recorded at wells further away from the river, the slope of the straight line fit (i.e. scaling exponent) is smallest when the time scale is between 1 and 3 days. When the time scale is < 1 day, groundwater variations become persistent. When the time scale is between 1 and 3 days, the variations are close to white noise, but return to persistent when the time scale is > 3 days. Copyright © 2011 John Wiley & Sons, Ltd.     

地理信息网络共享的研究和应用进展

地学信息对地学研究具有非常重要的作用。本文结合目前互联网上地学信息共享的现状探讨了地理信息网络共享的意义,对基于元数据和网络地理信息系统的地学数据共享的两种机制做了综述,认为地学元数据的可视化查询检索和网络数据融合服务是地理信息网络共享的重要发展方向,最后探讨了将来地理信息网络共享的主要特点。     

Multiple Wavelet Coherence to Evaluate Local Multivariate Relationships in a Groundwater System

Groundwater level fluctuations are affected by surface properties due to complex correlations of groundwater-surface water interaction and/or other surface processes, which are usually hard to be accurately quantified. Previous studies have assessed the relationship between groundwater level fluctuations and specific controlling factors. However, few studies have been conducted to explore the impact of the combination of multiple factors on the groundwater system. Hence, this paper tries to explore the localized and scale-specific multivariate relationships between the groundwater level and controlling factors (such as hydrologic and meteorological factors) using bivariate wavelet coherence and multiple wavelet coherence. The groundwater level fluctuations of two wells in areas covered by different plant densities (i.e., the riparian zone of the Colorado River, USA) are analyzed. Main findings include three parts. First, barometric pressure and river stage are the best factors to interpret the groundwater level fluctuations at small scales (<1 day) and large scales (>1 day) at the well of low-density plants stand, respectively. Second, at the well of high-density plants stand, the best predictors to control the groundwater level fluctuations include barometric pressure (<1 day), the combination of barometric pressure and temperature (1-7 days), temperature (7-30 days), and the combination of barometric pressure, temperature, and river stage (>30 days). The best predictor of groundwater head fluctuations depends on the variance of the vegetation coverage and hydrological processes. Third, these results provide a suite of factors to explain the groundwater level variations, which is an important topic in water-resource prediction and management.     

北半球大气环流异常与广西夏季高温天气

利用1951~2003年北半球500 hPa月平均高度场资料,对广西多高温年份和少高温年份的大尺度环流场进行对比分析,发现多高温年和少高温年500 hPa位势高度距平场差异明显,主要表现在:北太平洋阿留申群岛到副热带地区在冬春季和前汛期都呈现相反的南北距平分布结构;盛夏,多高温年在乌拉尔山至贝加尔湖地区及孟加拉湾至我国西南地区是正距平区,而少高温年在上述地区为负距平中心。典型相关分析表明,7~8月500 hPa高度场与前期1月、4~6月的高度场有密切的联系,高空槽脊的强弱分布及西太平洋副高等大尺度天气系统的变化本身具有一定的内相关,从而揭示了高温天气形成的大尺度环流变化的一些事实。     

人工智能和专家系统在地学中的应用综述

本文所指的地学是以地理学为主包括地质、气象、水文等以地球表层为研究对象的学科,其研究对象具有多因素相互作用的复杂性。本文在回顾了地理学／地学研究方法发展过程的基础上,分析了人工智能、专家系统、地理信息系统的相互关系,综述了专家系统在地学中的应用实例,最后分析了地学专家系统的发展趋势。     

民勤盆地地下水供需分析及对策

本文分析了民勤盆地水文地质条件和地下水资源的特点、开发现状,阐述了地下水开发利用中存在的主要问题.在此基础上提出了民勤盆地地下水开发利用的对策与建议.