夏季东北亚阻塞高压年际变化的一个物理机制

根据实际观测资料反演获得描述大气环流演变的空间谱函数后,从改进的高截断谱模式途径出发研究了夏季东北亚阻塞高压年际变化的物理机制.结果表明,前期外部热源强迫的空间分布大致为El Nio型分布时,外部热力强迫导致大气环流演变中波波相互作用主要表现为纬向2波的相互作用;波流相互作用主要表现为经向2波和3波与反映基本流中的经向1波的相互作用.这样使得500 hPa高度场上东北亚地区为一相对正异常区,为夏季东北亚阻塞的频繁发生提供了有利的大气环流背景.而前期外部热源强迫大致为La Nia型分布时,外部热力强迫则导致大气环流演变中波波相互作用主要表现为纬向1波的相互作用;波流相互作用主要表现为经向2波和4波与反映基本流中的经向2波的相互作用.从而使得500 hPa高度场上帆北亚地区出现相对负异常,抑制了夏季东北亚阻塞的发生.     

关于VTI介质中多分量转换波地震数据采集的最佳接收时窗

以P_P波时窗和P_SV波时窗的交叉部分作为VTI介质中P_P波、P_SV波联合采集的最佳时窗,在有效时窗内通过基于VTI介质的射线追踪法确定每个反射点的P_P波、P_SV波射线路径和相角,求解Zoeppritz方程得出P_SV波与P_P波反射系数(或透射系数)的比值,并将该比值的绝对值定义为控制因子G. 以G值作为控制VTI介质中P_P波、P_SV波联合采集观测系统设计的主要参数,通过分析G值确定检波器位置的最佳接收时窗,得出优化VTI介质中多分量转换波地震数据采集的接收时窗的方法.     

地下水氮污染治理的探索试验

太行山前石家庄平原区地下水多存在氮污染问题,该文应用已优化制备的生物脱氮菌剂并结合工业乙醇碳源的一同使用,在由一现场渗流区概化制作的多孔介质模型--中细砂箱中,作了一定水流条件下的生物脱氮除污模拟试验探索.结果显示,以一定时段作考察,在投源点位置附近及水流下游的一定范围内,该实施方法可高效去除地下水中的氮污染.为指导野外现场地下水污染的治理,提供科学依据.     

多云多雨环境遥感研究与应用分析

云、雾、雨往往导致获取同步观测陆面-大气或海面-大气的遥感数据的复杂性,使得多圈层探测的遥感数据缺乏连续性、实时性、准确性和可用性。所以,多云、多雨环境一直成为遥感对陆面和海面探测与研究的瓶颈。对我国来说,只有实现在多云、多雨地区的全天候、全天时地对地观测,我国的遥感应用才能形成一个较为完整的体系。我们提出了多云、多雨地区遥感这个概念,介绍这方面的研究进展。为解决这一瓶颈问题,通过多云、多雨环境下对地观测系统数据获取与信息处理的多学科研究,提出发展适用于多云、多雨环境的对地观测系统的科学思路与方案。     

不同实验条件下软质岩石地基承载力分析

现行《岩土工程勘察规范》(GB50021-2001)及《建筑地基基础设计规范》(GB50007-2002)规定,确定岩石地基承载力特征值常用方法有取岩样作室内试验和现场原位载荷试验等。软质岩的岩石试样作室内试验时,因环境条件与实地有明显的差异,试验结果多不理想,现场静载试验在实际环境条件下进行,能更好地挖掘软质岩石地基承载力特征值的潜力,减少基础工程造价。     

重力坝大孔口坝段抗震试验研究

以景洪水电站重力坝大孔口坝段为研究对象,通过输入没特性地震波的振动台模型试验和三维有限元分析,定量、定性地研究了大孔口坝段地震反应的特性。结果表明,对于大孔口坝段使用现行抗震规范反应谱曲线乍得的结果偏小;用振型迭加计算大孔坝段地震响应,参与迭加的振型不应少于五阶;应充分考虑不同地震特性的影响。     

巷道围岩动态工程分类技术研究

基于围岩质量计算、柱状图数字化和重组、结构面诊断、围岩结构装配、采动应力作用后围岩结构演化等研究成果,采用工程要求、基本结构、演化结构为一级指标,提出了围岩的动态工程分类技术、分类结果的表式表达技术,并指出了分类结果的应用方法。     

Review: The International Sediment Initiative case studies of sediment problems in river basins and their management

Management of sediment in river basins and waterways has been an important issue for water managers throughout history. The changing nature of sediment issues has meant that water managers today face many complex technical and environmental challenges in relation to sediment management. UNESCO's International Hydrological Programme(IHP) launched the International Sediment Initiative(ISI) in 2002.ISI aims to further advance sustainable sediment management on a global scale. This is achieved through the delivery of a decision support framework for sediment management that provides guidance on legislative and institutional solutions, applicable across a range of socio-economic and physiographic settings in the context of global change. ISI mobilizes international experience on sediment problems and their management through the compilation of a series of case studies representative of a broad range of physiographic and socio-economic conditions, which are made available as guidance for policy makers dealing with water and river basin management. Case studies prepared to date include the basins of the Nile, Mississippi, Rhine, Volga, Yellow, and Haihe and Liaohe rivers. Available in full from the ISI website,these detailed case studies are briefly introduced in this review articles.     

Field measurements for calibration of simplified models of the stiffening effect of infill masonry walls in high-rise RC framed and shear-wall buildings

As a type of nonstructural component, infill walls play a significant role in the seismic behavior of high-rise buildings. However, the stiffness of the infill wall is generally either ignored or considered by simplified empirical criteria that lead to a period shortening. The difference can be greatly decreased by using a structural identification methodology. In this study, an ambient vibration test was performed on four on-site reinforced concrete high-rise buildings, and the design results were compared with the PKPM models using corresponding finite element(FE) models. A diagonal strut model was used to simulate the behavior of the infill wall, and the identified modal parameters measured from the on-site test were employed to calibrate the parameters of the diagonal strut in the FE models. The SAP2000 models with calibrated elastic modulus were used to evaluate the seismic response in the elastic state. Based on the load-displacement relationship of the infill wall, nonlinear dynamic analysis models were built in PERFORM-3 D and calibrated using the measured modal periods. The analysis results revealed that the structural performance under small/large earthquake records were both strengthened by infill walls, and the contribution of infill walls should be considered for better accuracy in the design process.     

The dynamic and thermodynamic processes dominating the reduction of global land monsoon precipitation driven by anthropogenic aerosols emission

Changes in monsoon precipitation have profound social and economic impacts as more than two-thirds of the world's population lives in monsoon regions. Observations show a significant reduction in global land monsoon precipitation during the second half of the 20 th century. Understanding the cause of this change, especially possible anthropogenic origins, is important.Here, we compare observed changes in global land monsoon precipitation during 1948–2005 with those simulated by 5 global climate models participating in the Coupled Model Inter-comparison Project-phase 5(CMIP5) under different external forcings.We show that the observed drying trend is consistent with the model simulated response to anthropogenic forcing and to anthropogenic aerosol forcing in particular. We apply the optimal fingerprinting method to quantify anthropogenic influences on precipitation and find that anthropogenic aerosols may have contributed to 102%(62–144% for the 5–95% confidence interval)of the observed decrease in global land monsoon precipitation. A moisture budget analysis indicates that the reduction in precipitation results from reduced vertical moisture advection in response to aerosol forcing. Since much of the monsoon regions,such as India and China, have been experiencing rapid developments with increasing aerosol emissions in the past decedes, our results imply a further reduction in monsoon precipitation in these regions in the future if effective mitigations to reduce aerosol emissions are not deployed. The observed decline of aerosol emission in China since 2006 helps to alleviate the reducing trend of monsoon precipiptaion.