新型预制装配式楼盖抗倒塌试验研究

地震及爆炸荷载下的结构连续倒塌问题对人民的生命财产造成重大威胁,是土木工程领域研究的一个热门方向。为了提高新型预应力空心楼板结构的整体性,防止由于竖向支承构件的失效形成楼板的局部或者连续倒塌,对2块新型预应力空心板足尺模型进行四分点静力加载试验,研究新型预制装配式两跨连续楼板的抗连续倒塌能力。试件均由预应力空心短板通过板端伸出U形筋和胡子筋进行对接连接,板侧纵向拼缝通过胡子筋和植筋与边梁的纵筋进行连接,2个试件的计算跨度相同。本文采用在加载过程中突然拆除中间支座,得到楼板破坏形态、裂缝发展、承载能力、应变、最大变形等试验结果。对试件的受力过程、悬索作用机理进行分析,最后得到楼盖拼缝及板侧边梁连接构造的布置合理,新型预制装配式楼盖采用合适的周边连系和横向拼缝连接可以达到理想的抗倒塌能力。     

基于主成分降维的总悬浮物浓度遥感估算模型适用性分析

总悬浮物浓度(C_TSM)是水质评价的重要参数.为了提高内陆Ⅱ类水体总悬浮物浓度估算的精度,利用主成分分析方法对2009年4月太湖水体实测高光谱数据进行降维处理,进而以不同数量的主成分作为变量,分别构建总悬浮颗粒物浓度的多元线性回归估算模型并比较这些模型的效果,从而确定最优的主分量个数;结合近年运行的高光谱传感器,对模型的适用性进行评价.结果表明:①前三个主成分(PC₁、PC₂、PC₃)从不同侧面涵盖了悬浮物浓度信息,它们与ln(C_TSM)的相关系数分别为0.728、0.401和0.403;②当主成分个数为6时,模型达到最优;模型的精度高于4个传统经验模型;③在400~850 nm之间,波段数大于45的高光谱传感器数据都能利用主成分分析的方法构建精度较高的总悬浮物浓度估算模型;此外,MERIS、HJ1-HSI、Hyperion和CHRIS这些常用的高光谱传感器的波段设置,都适合于主成分建模.     

Modeling spatially correlated spectral accelerations at multiple periods using principal component analysis and geostatistics

Regional seismic risk assessments and quantification of portfolio losses often require simulation of spatially distributed ground motions at multiple intensity measures. For a given earthquake, distributed ground motions are characterized by spatial correlation and correlation between different intensity measures, known as cross‐correlation. This study proposes a new spatial cross‐correlation model for within‐event spectral acceleration residuals that uses a combination of principal component analysis (PCA) and geostatistics. Records from 45 earthquakes are used to investigate earthquake‐to‐earthquake trends in application of PCA to spectral acceleration residuals. Based on the findings, PCA is used to determine coefficients that linearly transform cross‐correlated residuals to independent principal components. Nested semivariogram models are then fit to empirical semivariograms to quantify the spatial correlation of principal components. The resultant PCA spatial cross‐correlation model is shown to be accurate and computationally efficient. A step‐by‐step procedure and an example are presented to illustrate the use of the predictive model for rapid simulation of spatially cross‐correlated spectral accelerations at multiple periods.     

Extracting water-related features using reflectance data and principal component analysis of Landsat images

This study aimed to map water features using a Landsat image rather than traditional land cover. We involved the original bands, spectral indices and principal components (PCs) of a principal component analysis (PCA) as input data, and performed random forest (RF) and support vector machine (SVM) classification with water, saturated soil and non-water categories. The aim was to compare the efficiency of the results based on various input data. Original bands provided 93% overall accuracy (OA) and bands 4–5–7 were the most informative in this analysis. Except for MNDWI (modified normalized differenced water index, with 98% OA), the performance of all water indices was between 60 and 70% (OA). The PCA-based approach conducted on the original bands resulted in the most accurate identification of all classes (with only 1% error in the case of water bodies). We therefore show that both water bodies and saturated soils can be identified successfully using this approach.     

2012年江苏扬州M 4.9地震前地磁垂直分量日变双低点异常

2012年6月13日和7月10日华东地区部分地磁台垂直分量日变形态出现双低点异常,首次异常出现后37天,于7月20日发生江苏扬州M 4.9地震,震中位于低点位移分界线附近。分析认为,在强震前由于应力变化,引起孕震体环境中介质电导率等电磁性质发生改变,区域地磁场垂直分量日变曲线出现相位和幅度变化,说明地磁垂直分量日变双低点异常与地震的孕育和发生相关。     

地质专业图书馆的藏书建设与发展浅论

对地质专业图书馆的藏书建设与发展进行了浅显的论述。指出地质专业图书馆目前藏书和组织存在的一些问题,并根据实际情况提出了地质专业图书馆的发展对策。     

选主元矩阵原位替换解算方法

矩阵行列式、矩阵方程未知数和矩阵逆阵元素,可采用矩阵原位替换解算方法,利用矩阵元素约化值进行解算,但矩阵元素约化值计算过程中要求矩阵主元约化值不能等于零,在没有确认矩阵是否满秩的情况下,其值等于零有可能由矩阵元素排列结构引起,也有可能由矩阵秩亏引起,如何判别矩阵主元约化值为零的成因,在排除矩阵秩亏的情况下,如何利用选主元矩阵原位替换解算方法继续完成相应矩阵解算,是本文研究的内容。该研究可使矩阵原位替换解算方法得到更加广泛的应用。     

越南中部Kontum地块前寒武纪地壳组成和构造演化

越南中部的Kontum 地块是印支地块中前寒武纪变质岩最重要的出露地区之一。该地块由不同时代不同变质程度的岩石组成。该研究通过对该地区主要变质岩的岩石学、地球化学和锆石U-Pb 年代学分析,探讨了Kontum 地块的物质组成以及其形成的构造背景。岩相学和化学成分分析结果表明,这些基底变质岩主要由变质沉积岩和少量的变质火成岩组成。变质沉积岩的原岩主要是硬砂岩和页岩。锆石U-Pb 定年结果显示,这些沉积岩形成于古元古代晚期到新元古代晚期,并大致可以划分为五期沉积盆地的形成和演化,分别对应岛弧环境、被动大陆边缘环境、活动大陆边缘或大陆弧环境、活动大陆边缘-被动大陆边缘过渡环境和活动大陆边缘的构造背景。二个变质火成岩的原岩分别是拉斑玄武岩和S 型花岗岩,它们分别形成于1424 Ma 和1485 Ma。拉斑玄武岩显示富集Rb、Ba、Sr 等大离子亲石元素,亏损Nb、Ta、Zr、Ti 等高场强元素,符合典型岛弧玄武质岩石的地球化学特征。其锆石的εHf(t)值主要为正值（-1.68~+14.2）, 表明其岩浆起源于亏损的岩石圈地幔。地球化学特征表明其形成于岛弧环境,与第三期沉积沉积作用环境相符。S 型花岗岩具有较高的SiO2、ALK和A/CNK（>1.1）,以及中等的稀土含量和中等的Eu 负异常。其原岩岩浆锆石的εHf (t)值变化于+5.97~+12.1,表明源区沉积岩的碎屑主要来自新生地壳。对比显示Kontum 地块与海南岛在中元古代时期很可能曾经相连,在Columbia 超大陆裂解时期处于超大陆的边缘。     

基于主成分分析和因子分析的宁夏水资源承载力研究

为了探求宁夏水资源承载力状况,利用主成分分析法和因子分析法,在分析宁夏2004~2014年水资源承载力状况的基础上,对宁夏5市2013年水资源承载力分水资源支持力、社会经济技术水平和社会生活水平3个方面进行综合考虑,得到宁夏5市的水资源利用状况指数和分级标准。具体得到以下几个结论:(1)2004~2014年间,宁夏水资源承载力仅在2005~2006年有所波动,其余年份两种方法结果一致,11年间保持稳定上升;(2)对于宁夏5市2013年水资源承载力状况,主成分分析结果由大到小排序为吴忠市、银川市、石嘴山市、固原市和中卫市,因子分析结果由大到小排序为吴忠市、银川市、固原市、石嘴山市和中卫市;(3)建立宁夏5市水资源承载力状况分级阈值,主成分分析下吴忠市和银川市的水资源利用状况高,石嘴山市的水资源利用状况中等,固原市和中卫市的水资源利用状况低;因子分析下吴忠市和银川市的水资源利用状况高,其余3市水资源利用状况都较低。     

Assessing model of highway slope stability based on optimized SVM

Considering the geological hazards attributed to the highway slope, using a common simple model cannot accurately assess the stability of the slope. First, principal component analysis (PCA) was conducted to extract the principal components of six factors (namely, bulk density, cohesion, internal friction angle, slope angle, slope height, and pore water pressure ratio) affecting the slope stability. Second, four principal components were adopted as input variables of the support vector machine (SVM) model optimized by genetic algorithm (GA). The output variable was slope stability. Lastly, the assessing model of highway slope stability based on PCA-GA-SVM is established. The maximal absolute error of the model is 0.0921 and the maximal relative error is 9.21% by comparing the assessment value and the practical value of the test sample. The above studies are conducive to enrich the assessing model of highway slope stability and provide some reference for highway slope engineering treatment.