隧道锚杆锚固质量无损检测技术   总被引：2，自引：0，他引：2  

黄华林  朱自强  杨天春  王齐仁  鲁光银 《物探与化探》2005,29(6):551-553

采用声波检测仪,应用声频应力波在不同波阻抗面反射的能量和相位的变化原理,对隧道的锚杆锚固质量进行了无损检测试验研究,并对检测技术进行了探讨.结果表明,作为一种工程质量管理辅助手段,采用应力波对锚杆锚固质量进行无损检测,丰富了隧道围岩锚固质量检测方法,为隧道工程建设提供更好的质量保障.  相似文献   

鄂尔多斯盆地石炭纪中央古隆起形成机制   总被引：1，自引：4，他引：1  

王庆飞  邓军  黄定华  高帮飞  徐浩 《现代地质》2005,19(4):546-550,595

将鄂尔多斯盆地简化为受南北挤压的等厚各向同性弹性薄板模型进行应力—应变场数值模拟,力图揭示鄂尔多斯地区石炭纪出现的细腰状中央古隆起的形成机制。模拟中Z轴方向应变(εz)正值区对应于盆地内部的隆起区,zε正等值线形态对应于隆起形态;单轴挤压条件下,εz正等值线总会呈现沿应力轴方向延伸的细腰状形态;点作用力产生的zε正等值线范围局限,而线作用力产生的εz正值区分布较广。模拟结果表明鄂尔多斯盆地石炭纪细腰状隆起是在南北边界受挤压条件下,应力—应变在盆地内部传递过程中所必然出现的结果,南北向点作用力比南北向线作用力产生的zε等值线形态更接近于鄂尔多斯盆地中央古隆起形态;点作用力可能代表了石炭纪微板块间的点碰撞或者弧—陆碰撞。  相似文献   

某大厦深基坑开挖与施工安全监测实践与体会     

陆锦标 《现代测绘》2005,28(5):17-19

从深基坑安全监测实例出发,介绍了一种简便、易行、稳定、可靠的射线形水平位移基准网,同时适用用小角法高精度位移监测.另外就温度的变化对水平位移值的影响,降水施工对地面沉降,深层土体位移的影响及测斜管埋设的重要性提出了自己的观点、认识与体会,希望对类似工程有一定参考价值.  相似文献   

基于DSM阴影仿真和高度场光线跟踪的影像阴影检测     

李艳  宫鹏 《遥感学报》2005,9(4):357-362

介绍了一个建筑物阴影检测的模型。首先利用摄影测量学原理来计算阴影坐标。即用数字表面模型(digitalsurfacemodel,缩写为DSM)和太阳高度和方位来计算建筑物阴影的空间坐标,并由相机模型计算出每个阴影单元对应的扫描行和相机空间坐标。由高度场光线跟踪判断阴影的可见性,对可见阴影计算出它在投影图像上的坐标。然后在这个结果的基础上再对图像进行阴影的细分割。  相似文献   

基于地表定量参数的沙漠化遥感监测方法     

曾永年  冯兆东  向南平 《国土资源遥感》2005,16(2):40-44

利用野外沙漠化调查的定位数据和ETM+ 遥感数据，在实验分析的基础上，探讨了沙漠化程度与地表参数之间的定量关系，即沙漠化与植被指数（NDVI）、地表辐射温度（LST）之间的关系，提出了综合反映沙漠化土地生物物理特征的遥感监测指数——沙漠化遥感监测差值指数（DDI），为沙漠化遥感监测提供有效的定量化方法。  相似文献   

Outlier detection algorithms and their performance in GOCE gravity field processing   总被引：2，自引：0，他引：2  

M. Kern  T. Preimesberger  M. Allesch  R. Pail  J. Bouman  R. Koop 《Journal of Geodesy》2005,78(9):509-519

The satellite missions CHAMP, GRACE, and GOCE mark the beginning of a new era in gravity field determination and modeling. They provide unique models of the global stationary gravity field and its variation in time. Due to inevitable measurement errors, sophisticated pre-processing steps have to be applied before further use of the satellite measurements. In the framework of the GOCE mission, this includes outlier detection, absolute calibration and validation of the SGG (satellite gravity gradiometry) measurements, and removal of temporal effects. In general, outliers are defined as observations that appear to be inconsistent with the remainder of the data set. One goal is to evaluate the effect of additive, innovative and bulk outliers on the estimates of the spherical harmonic coefficients. It can be shown that even a small number of undetected outliers (<0.2 of all data points) can have an adverse effect on the coefficient estimates. Consequently, concepts for the identification and removal of outliers have to be developed. Novel outlier detection algorithms are derived and statistical methods are presented that may be used for this purpose. The methods aim at high outlier identification rates as well as small failure rates. A combined algorithm, based on wavelets and a statistical method, shows best performance with an identification rate of about 99%. To further reduce the influence of undetected outliers, an outlier detection algorithm is implemented inside the gravity field solver (the Quick-Look Gravity Field Analysis tool was used). This results in spherical harmonic coefficient estimates that are of similar quality to those obtained without outliers in the input data.  相似文献   

Spectral Filtering and Classification of Terrestrial Laser Scanner Point Clouds   总被引：1，自引：0，他引：1  

Derek D.  Lichti 《The Photogrammetric Record》2005,20(111):218-240

A method is presented for filtering and classification of terrestrial laser scanner point clouds. The algorithm exploits the four-channel (blue, green, red and near infrared) multispectral imaging capability of some terrestrial scanners using supervised, parametric classification to assign thematic class labels to all scan cloud points. Its principal advantage is that it is a completely data-driven algorithm and is independent of spatial sampling resolution since the processing is performed in four-dimensional spectral feature space. Its application to two data-sets of different spatial extent and spatial and spectral complexity is reported, for which respective overall classification accuracies of 87·0% and 82·0% were achieved. Analysis of the input data with emphasis on the characteristics pertinent to the anticipated outcomes precedes detailed analysis of the classification results and error sources and their causes. Erroneously classified points are attributed to radiometric errors stemming from both detector hardware and physical effects.  相似文献   

Development of a remotely sensed,historical land-cover change database for rural Chihuahua,Mexico     

《International Journal of Applied Earth Observation and Geoinformation》2005,7(3):232-247

The purpose of this article is to describe the development of a remotely sensed, historical land-cover change database for the northwestern quarter of Chihuahua, Mexico, The database consists of multi-temporal land-cover classifications and change detection images. The database is developed to facilitate future investigations that examine urban–rural linkages as possible drivers of rural land-use and land-cover changes. To develop the needed land-cover change database, this study uses the North American Landsat Characterization (NALC) MSS triplicates because of their temporal depth and spatial breadth. Challenges exist, however, to effective classification and change detection using the NALC triplicates, including illumination differences across multiple scenes and periods caused by topographic and solar variations and the lack of ground reference data for historic periods. Therefore, creation of the database is a four step process. First, extensive pre-processing is performed to enhance comparability of multi-date images. Pre-processing includes topographic correction, mosaic creation and multi-date radiance normalization. Second, ancillary sources of land-cover data are combined with visual interpretations of enhanced images to define reference pixels used to classify the images using the maximum likelihood algorithm. Third, classification accuracy is assessed. Fourth, post-classification change detection is performed. Results indicate significant image improvements after pre-processing that permit very good overall classification (86.26% classified correctly) and change detection. To conclude, findings are presented that indicate significant changes to arid grasslands/shrublands and forest resources in mountainous regions.  相似文献   

时间序列转折突变点检测的线性函数方法   总被引：6，自引：2，他引：6  

曹杰  陶云  田永丽 《高原气象》2002,21(5):518-521

根据转折突变的定义，在引入线性半截多项式的前提下，提出检测时间序列转折突变点的一种新方法。此方法不仅能找出时间序列中存在的多个转折突变点，而且使得检测到的突变点通过统计显著性检验。应用此方法对北半球1851—1990年年平均气温距平及其11年滑动平均序列，1901—1999年昆明5月降水及其11年滑动平均的降水序列分别进行了检测。发现北半球年平均气温距平在1879、1889、1939和1973年附近出现了年际转折突变，在1878、1888和1941年以及1972年出现了年代际尺度的转折突变；昆明5月雨量不存在年际转折突变点，但昆明5月雨量在1918、1966以及1978年附近出现了年代际尺度转折突变。  相似文献   

Particle size dependent response of aerosol counters     

A. Ankilov  A. Baklanov  M. Colhoun  K. -H. Enderle  J. Gras  Yu. Julanov  D. Kaller  A. Lindner  A. A. Lushnikov  R. Mavliev  F. McGovern  T. C. O'Connor  J. Podzimek  O. Preining  G. P. Reischl  R. Rudolf  G. J. Sem  W. W. Szymanski  A. E. Vrtala  P. E. Wagner  W. Winklmayr  V. Zagaynov 《Atmospheric Research》2002,62(3-4)

During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions.The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the specific instrument was found. An enhanced detection efficiency for ultrafine hygroscopic sodium chloride aerosols was observed with water operated systems, an analogous trend was found for n-butanol operated systems with nonhygroscopic silver and tungsten oxide particles.  相似文献