Simulation of orthogonal horizontal ground motion components for specified earthquake and site characteristics

A method for generating an ensemble of orthogonal horizontal ground motion components with correlated parameters for specified earthquake and site characteristics is presented. The method employs a parameterized stochastic model that is based on a time‐modulated filtered white‐noise process with the filter having time‐varying characteristics. Whereas the input white‐noise excitation describes the stochastic nature of the ground motion, the forms of the modulating function and the filter and their parameters characterize the evolutionary intensity and nonstationary frequency content of the ground motion. The stochastic model is fitted to a database of recorded horizontal ground motion component pairs that are rotated into their principal axes, a set of orthogonal axes along which the components are statistically uncorrelated. Model parameters are identified for each ground motion component in the database. Using these data, predictive equations are developed for the model parameters in terms of earthquake and site characteristics and correlation coefficients between parameters of the two components are estimated. Given a design scenario specified in terms of earthquake and site characteristics, the results of this study allow one to generate realizations of correlated model parameters and use them along with simulated white‐noise processes to generate synthetic pairs of horizontal ground motion components along the principal axes. The proposed simulation method does not require any seed recorded ground motion and is ideal for use in performance‐based earthquake engineering. Copyright © 2011 John Wiley & Sons, Ltd.     

主成分分析法在我国海洋资源承载力变化趋势研究中的应用

如何更加合理有效地评价我国海洋资源承载力是我国海洋经济发展和海域经济发展的重要问题。基于主成分分析法的海洋资源承载力研究方法克服了专家打分法的缺陷,它以实际数据为支撑,更为客观的评价出了我国海洋资源承载力近年来的变化趋势,为我国海洋资源承载力的可持续发展提供理论支持。     

可扩展性桌面搜索引擎的设计与实现

为了使桌面搜索引擎具有良好的可扩展性和执行效率,满足用户对信息的全文检索要求,在研究桌面搜索引擎基本构件的基础上,架构出可扩展性桌面搜索引擎的系统体系结构,探讨了在Visual C++环境中如何基于组件编程的方法设计各关键构件、采用倒排索引和多线程处理等关键技术。结果表明该桌面搜索引擎可扩展性强并具有良好的效率和效果。     

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基于CT胸部图像肺结核球的定位

随着医学图像处理的快速发展,病灶区定位在医学应用中越来越引起人们的关注。以CT图像为研究对象,针对肺结核球的定位问题,先对预处理过的CT图像利用阈值技术二值化,采用形态滤波去除小桥,然后将每个连通区域标记出来。最终通过包括面积、周长、位置参数及形状参数等特征的决策器来判断确定肺结核球区域,并且定位出病灶区位置。     

What Depth Should Deep-Sea Water be Pumped up from in the South China Sea for Medicinal Research?

In this study, seawater was pumped up from 150, 200, 300, 500 and 1000 m in the South China Sea and analyzed to make certain what depth should deep-sea water (DSW) be pumped up for medicinal usage. The pumping depth of DSW was determined on the basis of chemical ingredients. The analyses of inorganic elements and dissolved organic matter (DOM) were performed by inductively coupled plasma mass spectrometry (ICP-MS) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) respectively. The raw data were used for hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results showed that seawater pumped up from 500 m and 1000 m was similar in their chemical ingredients, and was different from the seawater pumped up from other depths. These results indicated that seawater from more than 500 m depth had relatively stable chemical ingredients and could be used as DSW in the South China Sea.     

An Enhanced Remote Sensing Procedure for Material Mapping in the Western Desert of Egypt: A Tool for Managing Urban Development

Recently, both the Egyptian government and private sector have been interested in developing low desert zone areas. The low desert zones are located between the recent Nile flood plain and the limestone plateau, from the east and west sides, and represent an important source of aggregate materials. The development of these areas, however, will reduce the supply of aggregate materials so that new sources must be identified. This study describes several processing methods, applied to a Landsat Enhanced Thematic Mapper Plus image of 2001, to develop a reliable method to map the aggregate materials. By using different enhancement techniques with the help of a supervised classification method, it was found that decorrelation stretch and principal component analysis are the most suitable methods to discriminate between different types of aggregates, as well as to isolate these aggregates from the surrounding materials. Field and laboratory investigations indicated that two types of aggregates were recognized, confirming the remote sensing findings.     

基于微结构参数主成分的黄土湿陷性评价

黄土的湿陷性与其微观结构特征密切相关,它的微结构又受其应力状态和所处的含水状态影响。通过改变含水率与固结压力,对西安原状黄土进行了湿陷性试验,由此分析了不同含水率与固结压力条件下湿陷性的差异与联系,同时通过电镜扫描（SEM）获取了湿陷前、后黄土试样的微结构照片,进而获取了相应条件下的SEM照片的简单微结构参数。分析了湿陷前、后微结构参数的变化,探讨了简单微结构参数间相关关系,基于主成分分析法构建了合成微结构参数。研究表明：随着固结压力的增大,颗粒体所占比重越来越大,第1主成分近似线性增大,黄土湿陷系数与其累积主成分呈线性关系。根据这一重要认识,建立了主成分得分的湿陷系数计算方法,进而建立了黄土湿陷性评价方法。该研究对定量研究黄土湿陷性的微结构效应做了有益的探索。     

Assessment of Compressibility Behavior of Naturally Cemented Soft Clays

It Naturally cemented soft clays have components of strength and stiffness, which cannot be accounted for by classical soil mechanics (Leroueil and Vaughan 1990). This stems from the influence of structure caused by cementation due to environmental factors. It is necessary to evaluate the cementation bond strength at preyield and postyield stress levels of loading, to understand comprehensively the observed response from micromechanic considerations. This helps to better understand and evolve approaches to model the constitutive behavior in a consistent manner, according to the physical phenomenon of formation of cementation as an additional component to what is otherwise normally regarded as frictional behavior arising only from particulate nature of clays. Comparing the behavior of deep deposits of Pusan soft clays under stress with corresponding response of the same clay in its remolded state, it has been possible to take into account particulate and nonparticulate responses. The evolution of cementation bonding is modeled for different Pusan clays with the yield stress in oedometer compression as a normalizing parameter for obtaining the generalized relationship of cementation bonding with increase in stress. The already established model for determining the remolded behavior is appropriately modified to assess the behavior influenced by cementation. The model proposed consists of parameters, which are determined in routine investigations.     

民勤绿洲农田生态系统能值空间分异特征

利用能值分析方法对2011年民勤绿洲18个乡镇农田生态系统的环境资源条件、投入产出结构和可持续性进行了系统分析,构建了反映民勤绿洲农田生态系统综合水平的能值指标体系,运用主成分分析方法对其进行了综合评价和排序。结果表明：民勤绿洲农田生态系统可持续性强的是夹河乡,其他乡镇农田生态系统为消费型生态经济系统,可持续性弱;民勤绿洲农田生态系统能值综合水平存在着明显的地域差异,呈现东北片高于西南片、绿洲边缘带高于中心带的地理分布特征;民勤绿洲农田生态系统总体上不具有可持续性,不协调发展型区域和极不协调发展型区域农田面积占民勤绿洲农田总面积的73.68%,强、中、弱协调发展型区域只占26.32%。因此,目前民勤绿洲农田生态系统面临的不可持续性应当引起相关部门的高度重视。