航空放射性测量标准模型及其应用     

蔡文良  丘汉昌  顾仁康 《铀矿地质》1989,(5)

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。  相似文献   

华东中尺度地形对浙北暴雨影响的模拟研究   总被引：20，自引：2，他引：20  

高坤  翟国庆  俞樟孝  屠彩虹 《气象学报》1994,52(2):157-164

以一次梅雨降水为例，利用中尺度模式进行一系列中尺度地形对降水的增幅影响的敏感性试验。结果表明，中尺度地形对强降水区域的分布和强度有很大的影响，强降水中心位于地形附近，地形引起的１２小时降水增幅高达总降水的９０％以上；中尺度地形作为一种外界迫动，初始在低层形成气旋性辐合和水汽热量的集中，然后通过凝结潜热释放所造成的中高层增温和高层辐散，使得地形垂直环流加强和向上伸展。于是在降水、潜热释放与地形垂直环流之间出现一种正反馈机制，导致地形对降水的强烈增幅；同时午后下垫面加热所形成的不稳定层结也有利于地形垂直环流的不稳定发展，产生新的雨峰；初始场的中尺度扰动似乎在降水的地形性增幅中并不起明显作用。  相似文献   

航空伽玛能谱测量的高度修正及高度曲线拟合     

沈恩开 《铀矿地质》1989,5(5):292-297

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。  相似文献   

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

O. Undheim  H. I. Andersson  E. Berge 《Boundary-Layer Meteorology》2006,120(3):477-495

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.  相似文献   

Evaluation of slurry settling rate using fuzzy rule-based modeling     

Shahid Azam  Rehan Sadiq 《Acta Geotechnica》2006,1(3):149-156

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.  相似文献   

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

Manas K. Mukhopadhyay  Indra N. Sinha 《Environmental Geology》2006,50(5):669-676

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.  相似文献   

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

C. Cekerevac  S. Girardin  G. Klubertanz  L. Laloui   《Computers and Geotechnics》2006,33(8):432-443

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.  相似文献   

Undrained lateral load capacity of piles in clay using artificial neural network   总被引：2，自引：0，他引：2  

Sarat Kumar Das  Prabir Kumar Basudhar 《Computers and Geotechnics》2006,33(8):454-459

This paper describes the application of the artificial neural network model to predict the lateral load capacity of piles in clay. Three criteria were selected to compare the ANN model with the available empirical models: the best fit line for predicted lateral load capacity (Q_p) and measured lateral load capacity (Q_m), the mean and standard deviation of the ratio Q_p/Q_m and the cumulative probability for Q_p/Q_m. Different sensitivity analysis to identify the most important input parameters is discussed. A neural interpretation diagram is presented showing the effects of input parameters. A model equation is presented based on neural network parameters.  相似文献   

中尺度模式中辐射作用的敏感性试验   总被引：1，自引：5，他引：1  

赵鸣  周炜丹  陈潜  汤剑平 《气象科学》2006,26(1):1-9

在中尺度区域气候模式RIEMS中通过考虑和不考虑辐射对大气温度变化的影响来研究中尺度气象过程对辐射的敏感性。结果表明,在月尺度上,辐射可以引起平均约2℃的温度差,从而影响气压形势场和中尺度气象过程,进而影响降水。但在日尺度上,辐射的作用可以不计。  相似文献   

岩质边坡的关键块体稳定性影响因素的敏感性研究   总被引：5，自引：0，他引：5  

朱杰 《工程地质学报》2007,15(2):249-252

岩质边坡的关键块体是边坡安全分析和支护设计的重要方面,影响关键块体稳定性的因素较多,本文结合正交试验设计方法,对影响关键块体稳定的重要因素进行敏感性分析,评价不同物理力学参数对关键块体的安全系数的影响程度,为工程提供合理的意见。  相似文献