GPS vector configuration design for monitoring deformation networks

 The performance of geodetic monitoring networks is heavily influenced by the configuration of the measured GPS vectors. As an effective design of the GPS measurements will decrease GPS campaign costs and increase the accuracy and reliability of the entire network, the identification of the preferred GPS vectors for measurement has been highlighted as a core problem in the process of deformation monitoring. An algorithm based on a sensitivity analysis of the network, as dependent upon a postulated velocity field, is suggested for the selection of the optimal GPS vectors. Relevant mathematical and statistical concepts are presented as the basis for an improved method of vector configuration design. A sensitivity analysis of the geodetic geodynamic network in the north of Israel is presented, where the method is examined against two deformation models, the Simple Transform Fault and the Locked Fault. The proposed method is suggested as a means for the improvement of the design of monitoring networks, a common practice worldwide. Received: 30 July 2001 / Accepted: 3 June 2002 Acknowledgments. It is my pleasant duty to thank the Survey of Israel and Dr. E. Ostrovsky for providing the variance–covariance matrix of the G1 network in northern Israel. I would like to thank the reviewers of this paper for their constructive and helpful remarks.     

Stochastic multimedia risk assessment for a site with contaminated groundwater

 There exist many sites with contaminated groundwater because of inappropriate handling or disposal of hazardous materials or wastes. Health risk assessment is an important tool to evaluate the potential environmental and health impacts of these contaminated sites. It is also becoming an important basis for determining whether risk reduction is needed and what actions should be initiated. However, in research related to groundwater risk assessment and management, consideration of multimedia risk assessment and the separation of the uncertainty due to lack of knowledge and the variability due to natural heterogeneity are rare. This study presents a multimedia risk assessment framework with the integration of multimedia transfer and multi-pathway exposure of groundwater contaminants, and investigates whether multimedia risk assessment and the separation of uncertainty and variability can provide a better basis for risk management decisions. The results of the case study show that a decision based on multimedia risk assessment may differ from one based on risk resulting from groundwater only. In particular, the transfer from groundwater to air imposes a health threat to some degree. By using a methodology that combines Monte Carlo simulation, a rank correlation coefficient, and an explicit decision criterion to identify information important to the decision, the results obtained when uncertainty and variability are separate differ from the ones without such separation. In particular, when higher percentiles of uncertainty and variability distributions are considered, the method separating uncertainty and variability identifies TCE concentration as the single most important input parameter, while the method that does not distinguish the two identifies four input parameters as the important information that would influence a decision on risk reduction.     

Comparison of Large-Eddy Simulation Data with Spatially Averaged Measurements Obtained by Acoustic Tomography – Presuppositions and First Results

An attempt is made to compare results oflarge-eddy simulation (LES) in a convective boundarylayer using the model PALM with experimental data obtained from acoustic travel time tomography.This method provides two-dimensional data arrays, which are considered as more suitable forLES-validation than classical local orline-integrated measurements, because the tomographic data are area- or volume-averaged.For a quantitative comparison with experimental data in general, some prerequisites have to be considered: First of all, the initial and boundary conditions of the LES model have to be provided correctly by the experiment. Considering measurement errors, a sensitivity study was performed to investigate the influence of inaccurate initial and boundary conditions on the simulation results.This showed that for determining some boundary conditions, such as the surface temperature and the roughness length, high measurement accuracies are necessary, which are difficult to reach or which at least require considerable extra measurement efforts.The initial and boundary conditions provided by the Lindenberg experiment in 1999 turned out to be of insufficient accuracy to allow quantitative comparisons.However, a qualitative comparison was performed instead to investigate if the acoustic tomography method is a proper method for comparisons with LES models in general.It showed a good qualitative agreement with some quantitative differences. These differences can partly be explained by the sensitivity of the LES to initial and boundary conditions and by the limitations of the acoustic tomography.     

全球谱模式不同垂直分层对数值预报影响的敏感性试验

本文用σ-坐标原始方程全球谱模式,对1979年1月23日和6月14日两个个例,采用3种不同的垂直分层方案,进行了敏感性试验.通过对高度场均方根误差的分析,发现15层模式对北半球冬季预报效果的改进最明显.当其降低模式最高层高度和减少垂直分辨率时,预报误差首先从模式上层出现,然后影响到对流层中、下层.并指出南、北半球,冬、夏季不同层次上的预报对模式垂直分层的敏感性存在有差异,对南、北半球,冬、夏季的预报可采用不同的垂直分层模式. 南、北半球,冬、夏季预报敏感性差异的产生同行星尺度波动的水平感热通量的垂直分布、行星尺度波动能量的垂直输送特征有关.     

航空放射性测量标准模型及其应用

本文对我国建成的第一个航空放射性测量标准模型的场地、规格、含量、均匀性、密度等主要参数作了简略说明,并就应用模型标定航空伽玛能谱测量系统进行了讨论。     

航空伽玛能谱测量的高度修正及高度曲线拟合

本文对航空伽玛能谱测量中的高度修正和高度曲线拟合等问题做了一些新的探讨,给出了准确进行高度修正和高度曲线拟合的实用方法,可提高航空伽玛能谱测量的精确度,并能实现地面和空中灵敏度的换算。     

Non-Linear, Microscale Modelling of the Flow Over Askervein Hill

The flow solver “3DWind” is used to explore new aspects of the Askervein hill flow case. Previous work has investigated sensitivities to the grid, the inflow boundary profile, the roughness and the turbulence model. Several different linear and non-linear numerical models have also been validated by means of the Askervein hill case. This analysis focuses on the flow sensitivity to the grid spacing, the incident wind direction and the vertical resolution of topographic data. The horizontal resolution is found to be fine enough to cause only minor differences compared to a grid where every second node is removed. The vertical resolution dependence is mainly attributed to the wall functions. Simulations are performed for wind directions 200°, 205°, 210° and 215° at the reference station. The smallest directional biases compared to experimental values along a line through the hilltop are found for the directions 200° and 205°. There are larger wind direction changes along this line through the hilltop in the 200° case than in the 215° case. Still the simulation results give less veering than found in the experimental results, and this is maybe caused by a slightly stable atmosphere. The sensitivity to the vertical resolution of the topographical data is found to be particularly high close to the ground at the top of the hill; this is where the speed-up is most important. Differences decrease with the height from the ground. At higher levels the speed-ups are smaller and caused by terrain formations with larger scales.     

Evaluation of slurry settling rate using fuzzy rule-based modeling

The pressure acid leach process is the most widely used method of metal extraction from laterite ores. The self-weight settling rate of the ore slurries governs the throughput of the process and is improved by adding synthetic polymers. The charge density, molecular weight, and dosage of the polymers are the key factors influencing the settling rate of the slurries. This interdisciplinary paper uses the geotechnical understanding of hindered sedimentation for a mining engineering application. A conceptual fuzzy rule-based model was developed to evaluate the initial hydraulic conductivity of polymer-modified laterite ore slurries. Identification of control parameters and selection of the model architecture (fuzzy rule-base) were based on expert judgment. The developed model was trained and validated using bench-scale settling test data. The model reasonably predicts the initial hydraulic conductivity of polymer-added laterite ore slurry with a coefficient of determination of 0.75. Rank correlation coefficient-based sensitivity analyses indicated that charge density was the most significant polymer parameter followed by molecular weight and then by dosage. Charge density accounted for more than 97% of variability in the initial hydraulic conductivity estimates for both anionic and cationic polymers.     

A techno-economic model for optimum regeneration of surface mined land

The recent global scenario in the mineral sector may be characterized by rising competitiveness, increasing production costs and a slump in market price. This has pushed the mineral sector in general and that in the developing countries in particular to a situation where the industry has a limited capacity to sustain unproductive costs. This, more often than not, results in a situation where the industry fails to ensure environmental safeguards during and after mineral extraction. The situation is conspicuous in the Indian coal mining industry where more than 73% production comes from surface operations. India has an ambitious power augmentation projection for the coming 10 years. A phenomenal increase in coal production is proposed from the power grade coalfields in India. One of the most likely fall-outs of land degradation due to mining in these areas would be significant reduction of agricultural and other important land-uses. Currently, backfilling costs are perceived as prohibitive and abandonment of land is the easy way out. This study attempts to provide mine planners with a mathematical model that distributes generated overburden at defined disposal options while ensuring maximization of backfilled land area at minimum direct and economic costs. Optimization has been accomplished by linear programming (LP) for optimum distribution of each year’s generated overburden. Previous year’s disposal quantity outputs are processed as one set of the inputs to the LP model for generation of current year’s disposal output. From various geo-mining inputs, site constants of the LP constraints are calculated. Arrived value of economic vectors, which guide the programming statement, decides the optimal overburden distribution in defined options. The case example (with model test run) indicates that overburden distribution is significantly sensitive to coal seam gradient. The model has universal applicability to cyclic system (shovel–dumper combination) of opencast mining of stratified deposits.     

Calibration of an elasto-plastic constitutive model by a constrained optimisation procedure

The presented paper deals with a constrained optimisation technique for the calibration of elasto-plastic model parameters in a rational and objective manner. The procedure consists in finding a set of model parameters which minimise the difference between the experimental data and the numerical simulations defined by an objective function. For this purpose, an optimisation routine, termed ParaID, has been developed which combines the quasi-Newton and stochastic methods. The optimisation technique was employed to calibrate a multi-mechanism elasto-plastic constitutive model. Using the results of three isotropically consolidated drained triaxial compression tests, a comparison between numerical and experimental results clearly shows the capability of the optimisation procedure to determine the model parameters correctly.