A Web-based resource discovery facility for a Geo-Data Server

This article deals with the design of a resource discovery system, based on a Web interface, for searching and downloading data stored in a Geo-Data Server. The main features of the Geo-Data Server are the design of a cartographic and image database, following international standards, a relational catalogue, containing meta-information on the archived data, and a high-level interface to access the system. The Geo-Data Server implements a distributed system where data are appropriately organised for remote consultation.     

基于生态用水的地下水系统模拟与优化管理模型

通过对地下水系统与生态用水相互作用过程的研究，把生态用水作为重要的用水项目纳入到地下水系统模型考虑范畴，兼顾地下水的经济、环境和生态功能三者统一，在吉林省大安试验区建立了基于生态用水的地下水系统三维模拟与优化管理模型，采用该模型，分别模拟出试验区1998年和1999年地下水系统水资源各项均衡量，并确定了2000年地下水最佳开采利用方案，实现了地下水资源持续讥效利用，取得了良好的经济、生态和社会效益     

基于混沌时间序列的Volterra自适应滤波极移预报方法

针对极移复杂的时变特性, 根据混沌相空间坐标延迟重构理论, 提出一种基于Volterra自适应滤波的极移预报方法. 首先, 利用最小二乘拟合算法分离极移序列中的线性趋势项、钱德勒项和周年项, 获得线性极移、钱德勒极移和周年极移的外推值; 其次, 通过C-C关联积分法对最小二乘拟合残差序列进行相空间重构, 并利用小数据量法计算残差序列的最大Lyapunov指数验证其混沌特性, 在此基础上, 构建Volterra自适应滤波器对残差序列进行预测; 最后, 将线性极移、钱德勒极移和周年极移的外推值以及最小二乘拟合残差的预测值相加获得极移最终预报值. 利用国际地球自转服务局(International Earth Rotation and Reference Systems Service, IERS)提供的极移数据进行1--60d跨度预报, 并将预报结果分别与国际地球定向参数预报比较竞赛(Earth Orientation Parameters Prediction Comparison Campaign, EOP PCC)结果和IERS A公报发布的极移预报产品进行对比, 结果表明: 对于1--30d的短期预报, 该方法的预报精度与EOP PCC最优预报方法相当, 当预报跨度超过30d时, 该方法的预报精度低于EOP PCC最优预报方法, 优于参与EOP PCC的其他方法; 与IERS A公报相比, 该方法的短期预报效果较好, 当预报跨度增加时预报精度低于IERS A公报. 预报结果表明该方法更适合于极移短期预报.     

Identification of linear structural systems using earthquake-induced vibration data

This paper addresses the issue of system identification for linear structural systems using earthquake induced time histories of the structural response. The proposed methodology is based on the Eigensystem Realization Algorithm (ERA) and on the Observer/Kalman filter IDentification (OKID) approach to perform identification of structural systems using general input–output data via Markov parameters. The efficiency of the proposed technique is shown by numerical examples for the case of eight-storey building finite element models subjected to earthquake excitation and by the analysis of the data from the dynamic response of the Vincent-Thomas cable suspension bridge (Long Beach, CA) recorded during the Whittier and the Northridge earthquakes. The effects of noise in the measurements and of inadequate instrumentation are investigated. It is shown that the identified models show excellent agreement with the real systems in predicting the structural response time histories when subjected to earthquake-induced ground motion. Copyright © 1999 John Wiley & Sons, Ltd.     

多通道带乘性噪声系统的分部滤波算法

针对多通道观测环境下带乘性噪声系统的最优滤波问题,提出了1种状态最优滤波的分部算法。分部估计方法将状态估计分解为标称滤波估计和余项估计2项相加的形式。该算法在线性最小方差意义下是最优的。仿真实例表明,分部算法的鲁棒性更强,对系统初值的改变具有更强的适应能力。     

金沙江下游水文泥沙信息系统设计与实现

采用了ArcEngine组件,建立了金沙江下游水文泥沙信息系统,实现了以GIS为基础的水文泥沙数据、河道地形数据、河道水质数据的查询、编辑、二维三维数据表现、水文泥沙基础分析等功能。     

Application of the geographical information systems approach to watershed mass balance studies

This study was undertaken to test the utility of a geographical information systems (GIS) approach to problems of watershed mass balance. This approach proved most useful in exploring the effects that watershed scale, lithology and land use have on chemical weathering rates, and in assessing whether mass balance calculations could be applied to large multilithological watersheds. Water quality data from 52 stations were retrieved from STORET and a complete GIS database consisting of the watershed divide, lithology and land use was compiled for each station. Water quality data were also obtained from 7 experimental watersheds to develop a methodology to estimate annual fluxes from incomplete data sets. The methodology consists of preparing a composite of daily flux data, calculating a best fit sinusoid and integrating the equation to obtain an annual flux. Comparison with annual fluxes calculated from high resolution data sets suggests that this method predicts fluxes within about 10% of the true annual flux. Annual magnesium fluxes (moles km⁻² yr⁻¹) were calculated for all stations and adjusted for fluxes from atmospheric deposition. Magnesium flux was found to be a strong function of the amount of carbonate in the watershed, and silica fluxes were found to increase with the fraction of sandstone present in the watershed. All fluxes were strongly influenced by mining practices, with magnesium fluxes from affected watersheds being 6–10 times higher than fluxes from comparable pristine watersheds. Mining practices enhance chemical weathering by increasing the surface area of unweathered rock to which water has access and by increasing acidity and rate of mineral weathering. Fluxes were also found to increase with watershed size. This scale dependence is most likely caused by the sensitivity of weathering fluxes to even minor quantities of carbonates, which are likely to be found in all lithologies at larger scales. Mass balances were carried out in watersheds where gauged sub-watersheds made up more than 95% of the area. The calculations show large magnesium flux and water balance discrepancies. These errors may be a result of significant groundwater inputs to streams between gauges. The results suggest that improvements in how we measure discharge and estimate fluxes may be required before we can apply mass balance techniques to larger scales. © 1997 John Wiley & Sons, Ltd.     

考虑耦联影响的二次结构体系减震分析

建立了基础隔震的主次结构体系耦联运动方程,开发了动力分析程序PS—BASE．FOR,对一典型结构的二次结构绝对加速度反应谱与相对位移反应谱计算分析表明,主体结构隔震或同时增大二次结构阻尼,是取得二次结构较好抗震性能的有效途径,增大主体结构的隔震阻尼对二次结构略有不利影响。     

ESTIMATION OF SOIL PARAMETERS FOR ASSESSING POTENTIAL WETNESS: COMPARISON OF MODEL RESPONSES THROUGH GIS

A geographic information system (GIS) is utilized to model wetness potential for a portion of Uwharrie National Forest, North Carolina. The wetness index is derived from TOPMODEL, a hillslope-scale runoff simulation model. The wetness index is a distributed-parameter model, with the input parameters obtained from a digital elevation model (DEM) and Soil Conservation Service (SCS) soils data. The primary objectives of the research are to: (1) compare methods of estimating soil parameters for input into the wetness potential model; and (2) determine how the model outputs vary spatially as a consequence of different methods of estimating soil parameters. Three methods of estimating soil parameters are used: (a) assuming uniform soil properties; (b) using SCS data presented as ranges; and (c) using alternative literature-based estimates of soil parameters. Results indicate that the wetness model responds similarly regardless of how the soil parameters are estimated, but differences in the spatial variability of the wetness potentials occur as a result of estimating soil parameters through alternative approaches. Correlation, pair-wise regression and analysis of regression residuals are used to compare model responses within a GIS environment.     

Dynamical bispherical separability and physical realizability

The Stäckel form of potential required for separability of the equations of motion is examined in relation to Poisson's equation for a finite mass gravitational system whose mass is spatially concentrated with a density which is everwhere finite.