WATER-QUALITY MONITORING AND SPECIOUS DATA: THE EXAMPLE OF GEORGES CREEK,MARYLAND∗

Concurrent water data were collected by the U.S. Geological Survey, the U.S. Corps of Army Engineers, and the Maryland Department of Health and Mental Hygiene at the same site in order to describe present conditions and predict future environmental change in the Georges Creek basin in western Maryland. Evaluation of the data sets reveals measurement errors and weaknesses in sample design so that published complications contain significant errors. Unless these errors can be identified, policy based on such information may have unfortunate results.     

A spatially explicit methodology for a priori estimation of field survey effort in environmental observation networks

When establishing environmental monitoring programmes, it crucial to make reliable cost estimates, especially where a field survey is involved. This paper presents a methodology for creating a spatial measure of a field survey effort (SE). A set of relevant variables affecting a SE (e.g. areas with rough terrain, or distant from the main road network) was classified using fuzzy sets and then combined to produce spatially explicit effort indicators, which were integrated to a single measure using an analytic hierarchy process (AHP). To evaluate this approach and identify the limits for its application, three spatially nested case studies were used to test the spatial expression of SE and the scalable capacity of the method itself. The presented methodology could cope with variations in the scale and data resolution, retrieving a coherent estimate of SE across the different case studies. The presented methodology is therefore useful for (i) testing the network designs for sampling bias related to SE, (ii) comparing alternative sampling designs, (iii) assessing the sampling costs and (iv) supporting the human and logistical resource management.     

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永安地磁台的勘选与建设

介绍地磁台建设中场地勘选、建设方案以及材料的选择与检测、磁场梯度监控的一些方法.实践证明,永安地磁台的台址堪选与建设满足地磁台站建设规范的技术要求,说明方法切实有效,可以为其他地磁台站的新建、改造提供参考.     

Comparison of adaptive structural damage identification techniques in nonlinear hysteretic vibration isolation systems

Early structural damage identification to obtain an accurate condition assessment can assist in the reprioritization of structural retrofitting schedules in order to guarantee structural safety. Nowadays, seismic isolation technology has been applied in a wide variety of infrastructure, such as buildings, bridges, etc., and the health conditions of these nonlinear hysteretic vibration isolation systems have received considerable attention. To effectively detect structural damage in vibration isolation systems based on vibration data, three time-domain analysis techniques, referred to as the adaptive extended Kalman filter （AEKF）, adaptive sequential nonlinear least-square estimation （ASNLSE） and adaptive quadratic sum-sqnares error （AQSSE）, have been investigated. In this research, these analysis techniques are compared in terms of accuracy, convergence and efficiency, for structural damage detection using experimental data obtained through a series of laboratory tests based on a base-isolated structural model subjected to E1 Centro and Kobe earthquake excitations. The capability of the AEKF, ASNLSE and AQSSE approaches in tracking structural damage is demonstrated and compared.     

A frequency response function change method for damage localization and quantification in a shear building under ground excitation

A frequency response function change (FRFC) method to detect damage location and extent based on the change in the frequency response functions of a shear building under the effects of ground excitation was proposed in this paper. The damage identification equation was derived from the motion equations of the system before and after the occurrence of the damage. Efforts to make the FRFC method less model‐dependent were made. Intact system matrices, which could be estimated using the measured data without the need for an analytical model, and the frequency response functions were required for the FRFC method. The effects of measurement noise and model parameter error in the FRFC method were studied numerically. The proposed FRFC method was validated by experimental studies of a six‐story steel building structure with single and multiple damage cases. Copyright © 2012 John Wiley & Sons, Ltd.     

Groundwater monitoring strategies for variable contaminant migration boundaries

Abstract

Detection efficiencies of alternative groundwater monitoring networks were evaluated in relation to distance to a buffer zone (contaminant migration) boundary. This boundary establishes a distance limit within which contaminant plumes should pass through monitoring wells, located on curvilinear segments (monitoring loci) near a waste storage facility. Alternative strategies allocated monitoring wells to loci at specified distances, measured parallel to groundwater flow, from the downgradient boundaries of a landfill. One approach constrained wells to equal spacing, measured perpendicular to groundwater flow. Compressing well locations 10% closer to the downgradient corner of the landfill rendered alternative monitoring configurations. Computations by a monitoring efficiency model indicated: (a) networks largely maintained detection efficiency for different contaminant migration boundaries; (b) one network most efficiently attained a target detection capability for all contaminant migration boundaries; and (c) compressed networks slightly outperformed equal-spaced counterparts. Compressed networks with more wells along closer monitoring loci best maintained the detection efficiency when shifting the contaminant migration boundary closer to the landfill. Procedures described in this paper may be useful for examining trade-offs between monitoring efficiency and distance limits of contaminant travel at landfills posing potential hazards to underlying groundwater.     

GPS在地壳形变和板块运动监测中的应用

简要介绍了GPS在现代板块构造运动中的应用及其进展:GPS对于地球参考框架的建立和维持发挥着重要的作用;大量地壳运动监测网的建立使得GPS成为监测地壳运动强有力的工具;全球性、全天候的GPS卫星测高将在现代板块构造运动的监测中发挥重要作用;高精度的IGS产品为国际动力学服务提供坚实的数据基础。     

3S技术在地理国情监测中的应用

介绍了利用航空航天遥感、地理信息系统、卫星定位等现代测绘技术,在抚顺市林业资源进行动态化、空间化的持续监测中的应用,并初步建立适用的标准体系框架,为地理国情监测工作在全国的推广起到示范和带头作用。     

网络化自动监测预警系统的设计与实现

随着社会科技和信息化测绘的发展,大型工程安全监测的方法和手段也在飞速地发展,体现在了测量机器人、电子水准仪、GPS、网络通讯、传感器等测量技术的综合应用。国内基于物联网技术的工程监测预警系统也是随着安全监测与信息技术发展起来的。本文提出了在以大地测量仪器和物理学传感器为感知层,以GPRS／CDMA和互联网为网络层,以集成化的数据中心软件和网络数据库为应用层的基础上,设计开发了网络化自动监测预警系统。该系统集数据采集、数据处理、数据管理、数据分析和数据发布等功能于一体,是物联网和网络通讯完美结合下的物联网监测信息系统。