地表覆盖分类成果质量特征分析

自我国全面建成地理国情普查成果库之后,工作重心由全面普查变为重点监测。不论普查还是监测,准确地对地表覆盖进行分类一直是工作的重点和难点。在常态化监测阶段,把握地表覆盖分类成果的主要质量指标,归纳其诸如变化率、变化区域分布、变化类型,分析影响其成果质量的主要因素,对监测生产组织及质量控制具有非常重要的作用。     

基于多模GNSS接收机的卫星系统完好性监测

为了满足多卫星系统完好性监测的需要,本文通过对比不同卫星系统定位结果的方法来监测各个卫星系统的可用性。利用上述方法对实测的三模(GPS、GLONASS和COMPASS)数据进行了处理,结果表明该方法具有可行性,可为多模GNSS接收机的自主完好性监测提供参考信息。     

滑动窗口的普通克立格方法在降水量插值中的应用

利用2009年全国2200个观测站降水量资料,使用滑动窗口的普通克立格方法对降水量资料进行格点化估计。针对滑动窗口的普通克立格方法在降水量格点化应用中存在的问题,设计了3种技术处理的试验方案。比较了全局搜索与方位邻近方法的误差,讨论了最大影响半径及屏蔽效应对插值效果的作用。提出了方位邻近法的样本点选择策略,结果表明,相对传统滑动窗口的普通克立格方法较常使用的全局搜索法而言,方位邻近法显著降低了计算资源的耗用,同时又具有较高的插值精度,特别是在站点密集地区有突出的优势;试验结果也表明:变程为4°～5°的经(纬)线弧长时,在方位邻近法下,我国大部分区域有较好的插值效果;屏蔽效应弱,ε取值为0.1时,降水量插值准确率较高,随着ε增大,插值误差也逐渐增大。     

岩土压力传感器匹配误差的特性

在介绍了岩土压力传感器匹配误差概念的基础上,论述了匹配误差的稳定性、等效性、真实性和实用性以及各特性之间的相关性。通过研究得出：匹配误差特性的核心是稳定性;传感器刚性饼状设计是保证稳定性的必要条件;等效匹配误差不一定是真实的,但即使是不真实,也不影响实用性。     

Roughness effect on the correction factor of surface velocity for rill flows

Flow velocity is one of the most important hydrodynamic variables for both channelized (rill and gullies) and interrill erosive phenomena. The dye tracer technique to measure surface flow velocity V_s is based on the measurement of the travel time of a tracer needed to cover a known distance. The measured V_s must be corrected to obtain the mean flow velocity V using a factor α_v = V/V_s which is generally empirically deduced. The V_s measurement can be influenced by the method applied to time the travel of the dye-tracer and α_v can vary in different flow conditions. Experiments were performed by a fixed bed small flume simulating a rill channel for two roughness conditions (sieved soil, gravel). The comparison between a chronometer-based (CB) and video-based (VB) technique to measure V_s was carried out. For each slope-discharge combination, 20 measurements of V_s, characterized by a sample mean V_m, were carried out. For both techniques, the frequency distributions of V_s/V_m resulted independent of slope and discharge. For a given technique, all measurements resulted normally distributed, with a mean equal to one, and featured by a low variability. Therefore, V_m was considered representative of surface flow velocity. Regardless of roughness, the V_m values obtained by the two techniques were very close and characterized by a good measurement precision. The developed analysis on α_v highlighted that it is not correlated with Reynolds number for turbulent flow regime. Moreover, α_v is correlated neither with the Froude number nor with channel slope. However, the analysis of the empirical frequency distributions of the correction factor demonstrated a slope effect. For each technique (CB, VB)-roughness (soil, gravel) combination, a constant correction factor was statistically representative even if resulted in less accurate V estimations compared to those yielded by the slope-specific correction factor.     

兰州新一代天气雷达数据误差来源分析

新一代天气雷达目前已经成为对兰州市及周边地区短时强烈天气进行监测的主要手段之一。为了方便资料的处理和分析,提高观测资料准确度,为预报员和科研人员分析资料提供方便,通过对雷达数据前端生成和后端处理传输2个过程的分析,找出兰州新一代多普勒天气雷达数据误差的来源,并进行分析,发现地物回波、雷达天线增益、测量距离等因素和数据插值、坐标转换、远距离多终端传输等因素分别是前端数据产生过程中和后端数据处理传输过程中数据误差的主要来源。     

GPS在地面沉降监测中的应用探讨

利用GPS进行地面沉降监测能够解决传统测量方法工作量大、周期长的问题。该文结合实例，论述了GPS在地面沉降监测中的应用，分析了GPS测量方法的优点和误差，提出了GPS测量地面沉降的适用条件。     

西部山地复杂地震资料处理技术研究

在山地地震资料处理中,由于地震条件和地质条件复杂,使得资料的静校正问题严重,资料的信噪比偏低.通过采用配套的静校正技术和串联叠前去噪技术,较好地解决了这两个问题.     

Towards error‐free hybrid simulation using mixed variables

Two procedures are developed and implemented in a hybrid simulation system (HSS) with the aim of enhancing the accuracy and reliability of the online, i.e. pseudo‐dynamic, test results. The first procedure aims at correcting the experimental systematic error in executing the displacement command signal. The error is calculated as the difference between command and feedback signals and correlated to the actuator velocity using the least‐squares method. A feed‐forward error compensation scheme is devised leading to a more accurate execution of the test. The second procedure employs mixed variables with mode switching between displacement and force controls. The newly derived force control algorithm is evaluated using a parametric study to assess its stability and accuracy. The implementation of the mixed variables procedure is designed to adopt force control for high stiffness states of the structural response and displacement control otherwise, where the resolution of the involved instruments may favour this type of mixed control. A simple pseudo‐dynamic experiment of steel cantilever members is used to validate the HSS. Moreover, two experiments as application examples for the two developed procedures are presented. The two experiments focus on the seismic response of (a) timber shear walls and (b) reinforced concrete frames with and without unreinforced masonry infill wall. Copyright © 2007 John Wiley & Sons, Ltd.     

陀螺全站仪在隧道测量中的应用研究

随着我国经济和科技的蓬勃发展,隧道工程建设也呈现出规模化和多元化的趋势。本文首先总结了我国公路隧道、铁路隧道和水下隧道的增长状况;然后归纳了隧道测量中平面控制网的布设方法;最后通过分析发现:通过陀螺全站仪加测陀螺边来传递方位基准,可有效提高隧道贯通精度。