西安地铁隧道穿越地裂缝带的计算模型探讨

通过对西安地铁隧道穿越地裂缝带的大型物理模型试验成果的分析,提出在地裂缝活动时,穿越地裂缝带的地铁隧道有以下两个方面的变化特征：一是作用于隧道的荷载发生改变;二是在隧道底部产生脱空现象。这种脱空现象无论在整体式隧道还是盾构隧道中都会出现。造成隧道在界面上与土体脱空的原因是隧道和周围地层的变形不协调。脱空区域的大小对地铁隧道的变形与内力计算会产生明显影响。在对隧道变形特征分析的基础上,总结得出了西安地铁穿越地裂缝带隧道变形的4种计算模型：对于整体式长隧道,可以采用一端固定而另一端简支,或一端固定而另一端定向支承的计算模型;对于整体式短隧道,可以采用外伸梁模型;对于盾构隧道,可以采用一端固定而另一端定向支承的计算模型。最后,对脱空条件下隧道数值分析的建模问题进行了讨论。算例分析表明：在数值计算中,对于隧道与土体接触面的界面处理非常关键,否则将造成计算结果的重大误差。     

浅谈GPS静态相对定位与PTK定位在煤田勘探中的应用

分析实时GPS误差的来源,并用RTK测量技术来检核GPS静态相对定位所测设的E级控制点,对其测量精度做出相应的比较分析,阐述GPS静态相对定位和RTK定位技术在煤田勘探测量中的应用.     

Compared performances of different algorithms for estimating annual nutrient loads discharged by the eutrophic River Loire

Good estimates of pollutant fluxes are required for Earth systems sciences and water quality management. The gradual accumulation of water quality data records over the past few decades has increased the value of these data for examining long‐term trends. On many major rivers, however, infrequent sampling of most pollutants makes flux estimates and their analysis difficult. This paper explores the performance of different methods for estimating nutrient fluxes. The objective is to assess the accuracy (bias) and precision (dispersion) of annual nutrient fluxes based on monthly sampling, which is the frequency with which 80% of French water quality surveys have been carried out since 1971. The study is based on a data set of nutrient concentrations surveyed at high frequency during a 5 year pilot study (1981–85) at the Orléans station in the middle reaches of the River Loire, France. The mean specific fluxes were 641 (nitrate‐N), 96 (total‐P) and 37 kg year⁻¹ km⁻² (orthophosphate‐P). For each year, the data set was then ‘resampled’ by randomly simulating 12 sampling dates. 100 simulated monthly samplings were generated, upon which seven estimation methods were tested. The evaluations indicate that, when concentrations of specific substances in large rivers exhibit seasonal variation, a simple method based on linear interpolation between samples taken at approximately monthly intervals is advocated. With the monthly sampling interval, the precision (confidence level of 95%) of annual nutrient fluxes obtained by the appropriate methods was 13% for nitrates, 20% for total‐P, 26% for orthophosphates, and 34% for particulate‐P. The frequency of water quality surveys required to obtain an annual nutrient flux with 10% precision was around 15 days for nitrate, 10 days for orthophosphate‐P and total‐P, and about 5 days in the case of particulate‐P. Copyright © 2004 John Wiley & Sons, Ltd.     

中国地壳运动观测网络基本网观测精度研究

“中国地壳运动观测网络”于1998～2002年开展过5次基本网GPS联测。利用GIPSY软件处理结果进行的统计分析表明：基线定位水平分量精度为2～5mm，垂直分量为7～15mm；基线变化的水平分量测定精度为0．5mm／a，达到了流动观测的最高水平。分析基线定位误差发现：固定误差是目前相对定位的主要误差；与基线长度有关的比例误差对于水平分量而言，基本可以忽略。对速率的统计分析说明：至少4年观测间隔，才有可能获得比较精确、可靠的测站速率结果。     

A MULTIDISCIPLINARY AND INTEGRATED STUDY OF RICE PRECISION FARMING

In terms of demands of rice farming in the southern China,the information processing system and the yield measurement system that is installed in combine harvester,are designed and completed.Now the systems have been used in demonstration site in the Experiment Base of Shanghai Precision Agriculture.Based on the idea of spa-tial-oriented,object-oriented,user-oriented,the Farm Geographic Information System for precision farming of rice was developed,which is characterized by intelligence and visualized.The Decision-making Management System is integrated with rice growth model,expert model for rice cultivation.The DGPS,RS,GIS and intelligence sensors and computer technique were adopted in building the artificial intelligence system for measuring grain yield that is installed in combine har-vester,so the combine harvester could provide the grain yield distribution map real-timely.The environmental and econom-ic assessment shows that the precision rice farming applied in the demonstration site will benfit the society,economy and ecology greatly.     

GSM-18型高精度磁力仪在寻找隐伏金伯利岩管中的应用及效果

ＧＳＭ－１８型高精度磁力仪用于地质找矿已受到普遍关注和重视，特别是应用于覆盖区金刚石地质找矿、区分中低磁性异常具有高灵敏度、高分辩率特点。目前复县地区很难再发现地表裸露的金刚石原生矿，寻找隐伏金刚石原生矿已成为重要的研究课题。１１０号金伯利岩管的发现就是由于注重了对原始资料二次开发及综合信息提取研究工作，利用高精度磁力仪，采用新技术方法及不断结合传统的地质找矿方法，取得的较好的地质找矿成果的。     

地磁场时空差异对磁测精度影响的探讨

在辽南、辽西综合测网范围内，依赖于世界时变化的变化磁场比依赖于地方时变化的变化磁场对通化精度的影响更大一些。通化距离、经度方向距离、纬度方向距离对通化精度的影响不显著。磁情指数K在通化距离较大时对通化精度影响显著，但如果按世界时进行日变改正则可以消除磁情指数K的影响。     

高分辨率无人机低空影像DEM的建立及其精度研究

本文结合生产实践,介绍了基于无人机低空影像处理方法,生成比例尺1∶1000正射影像时构建的数字高程模型(DEM),利用检查点法对其所能达到的分辨率尺度范围进行实验讨论,得到无人机低空影像DEM合适的分辨率大小的结论,并且对无人机低空影像生成的DEM的精度进行评价.     

机载LiDAR系统定位方程、误差分析与精度评定

本文从机载LiDAR系统几何定位方程出发、基于误差传播规律推导了机载LiDAR系统的综合误差计算公式,分别研究了IMU测角、GPS、激光测距、扫描角等多种误差源对激光脚点定位精度的影响规律,从理论上分析了机载LiDAR系统定位精度.本文的结果对实际应用具有重要的参考价值.     

免棱镜全站仪在建筑物倾斜监测中应用与分析

随着科学技术的发展,现代高层建筑物日益呈现出结构的复杂性和风格的多样性,对高层建筑物的倾斜监测精度和方法也提出了新的要求.免棱镜全站仪具有对空间目标"所瞄即所测"快捷、高效的特性,应用于高层建筑物的倾斜监测,并经实际工程测试与分析,得出有益的结论.