Quantifying Uncertainty in Mineral Resources by Use of Classification Schemes and Conditional Simulations

Mineral inventory determination consists of estimating the amount of mineral resources on a block-by-block basis and classifying individual blocks into categories with increasing level of geologic confidence. Such classification is a crucial issue for mining companies, investors, financial institutions, and authorities, but it remains subject to some confusion because of the wide variations in methodologies and the lack of standardized procedures. The first part of this paper considers some of the criteria used to classify resources in practice and their impact through a sensitivity study using data from a Chilean porphyry copper deposit. Five classification criteria are compared and evaluated, namely: Search neighborhoods, absolute and relative kriging variances, absolute and relative conditional simulation variances. It is shown that some classification criteria either favor or penalize the high-grade areas if the grade distribution presents a proportional effect. In the second part of the paper, conditional simulations are used to quantify the uncertainty on the overall mineral resources. This approach is promising for risk analysis and decision-making. Unlike linear kriging, simulations allow inclusion of a cutoff grade in the calculation of the resources and also provide measures of their joint uncertainty over production volumes.     

Morphological development of the retention basin “Hartheim”: A case study

Flow in rivers and on floodplains is complex as it is affected by several interconnected factors such as topography, sediment transport and vegetation characteristics. The resulting processes are explained by the measure “Hartheim” planned for retention purposes at the Upper Rhine river. On the basis of existing formulas and instruments it is demonstrated that a good estimation of the development of the measure is possible. The proposed procedure is a useful tool for estimating morphological developments of restored river sections.     

Block-effective macrodispersion for numerical simulations of sorbing solute transport in heterogeneous porous formations

Heterogeneity is prevalent in aquifers and has an enormous impact on contaminant transport in groundwater. Numerical simulations are an effective way to deal with heterogeneity directly by assigning different hydraulic property values to each numerical grid block. Because hydraulic properties vary on different scales, but they cannot be sampled exhaustively and the number of numerical grid blocks is limited by computational considerations, the dispersive effects of unmodeled heterogeneity need to be accounted for. Dispersion tensors can be used to model the dispersion caused by unmodeled heterogeneity. The concept of block-effective macrodispersion tensors for modeling the effects of small-scale variability on solute transport introduced by Rubin et al. [Rubin Y, Sun A, Maxwell R, Bellin A. The concept of block-effective macrodispersivity and a unified approach for grid-scale- and plume-scale-dependent transport. J Fluid Mech 1999;395:161–80] is extended in this paper for use with reactive solutes. The tensors are derived for reactive solutes with spatially variable retardation factors and for solutes experiencing spatially uniform rate-limited sorption. The longitudinal block-effective macrodispersion coefficient is largest for perfect negative correlation between the log-hydraulic conductivity and the retardation factor. Because dispersion tensors, as they are usually implemented in numerical simulations, produce symmetric spreading, the applicability of the concept depends on the portion of the plume asymmetry caused by small-scale variability. The presented results show that the concept is applicable for rate-limited sorption for block sizes of one and two integral scales.     

Geospatial–temporal dependence among weekly precipitation extremes with applications to observations and climate model simulations in South America

A quantification of the spatio-temporal dependence among precipitation extremes is important for investigating the properties of intense storms as well as flood or flash-flood related hazards. Extreme value theory has been widely applied to the hydrologic sciences and hydraulic engineering. However, rigorous approaches to quantify dependence structures among extreme values in space and time have not been reported in the literature. Previous researchers have quantified the dependence among extreme values through the concept of (pairwise bivariate) tail dependence coefficients. For estimation of the tail dependence coefficients, we apply a recently developed method [Kuhn G. On dependence and extremes. PhD thesis (Advisor: C. Klüppelberg), Munich University of Technology, 2006] which utilized the multivariate tail dependence function of a subclass of elliptical copulas. This study extends the previous approach in the context of space and time by considering pairs of spatial grids in South America and quantifying the dependence among precipitation extremes based on the time series at each spatial grid. In addition, Kendall’s τ is used to estimate the pairwise copula correlation (for an elliptical copula) of precipitation between all grids in South America. The geospatial–temporal dependence measures are applied to precipitation observations from 1940 to 2005 as well as simulations from the Community Climate System Model version 3 (CCSM3) for 1940–2099. New insights are obtained regarding the spatio-temporal dependence structures for precipitation over South America both with regard to correlation as well as tail dependence.     

The decomposition and simulation of the longitudinal circulation in a coastal lagoon

Current measurements during a 32-day study period in late spring, 1977, are used to quantify the magnitude and relative importance of tidal and wind-driven motion in the interior of the Indian River lagoon, on the Atlantic coast of Florida. Harmonic analysis of the total longitudinal flow along the axis of the lagoon isolates the tidal component of the current; non-tidal flow is revealed by subtracting the tidal current from the total current, and making corrections for non-linear relationships between the current and both surface wind stress and bottom friction. A one-layer, one-dimensional model is developed to simulate wind drift. A quadratic bottom friction term with a drag coefficient of 15 × 10^?3 gives results which compare most favourably with observations. Results indicate that tidal forcing explains approximately 45% of the total variance at the study site, 25 km from the nearest inlet. Local wind forcing accounts for 44% of the non-tidal flow. The remainder of the variance is attributed to freshwater outflow through the lagoon and non-local forcing.     

基于Fluent的空气射流切削式反循环钻头参数优化

针对黄土地层,提出利用空气代替钻井液的反循环气体喷射技术。但现有技术对反循环气体喷射钻头切削土体的能力没有具体优化讨论。利用fluent软件,优化反循环喷射钻头结构参数,对不同底喷孔直径、底喷孔数量、底喷孔扩大段直径、底喷孔扩大段数量、喷射孔数量5个结构参数进行模拟分析。分析结果表明,在进风流量一定的情况下,增加底喷孔的数量或增大底喷孔的直径会削弱钻头的空气射流切削能力和反循环能力。底喷孔直径为3 mm,底喷孔个数为2个,底喷孔扩大段直径为8 mm,底喷孔扩大段长度为5 mm,内喷孔数量为5个时,反循环喷射钻头喷射能力和反循环能力最优。     

金融领域的随机建模与基于软件R的Monte Carlo模拟(2):Cox-Ross-Rubinstein模型

主要讨论了 Cox-Ross-Rubinstein (CRR) 模型和广义的CRR模型,并研究了如何基于CRR模型和广义的CRR模型利用Monte Carlo模拟计算资产价格以及期权价值.     

金融领域的随机建模与基于软件R的Monte Carlo模拟(5):Black-Scholes的世界

主要研究了Black-Scholes模型.与Black-Scholes期权定价公式相比,将再次强调和证实利用R软件Monte Carlo模拟的强大作用.     

A Taylor basis for kinematic nonlinear real-time simulations. Part I: The complete modal derivatives

Despite todays computational power, only small nonlinear numerical substructures may be simulated in real time. The size restriction on the substructures in nonlinear finite element analysis is primarily due to the time-consuming evaluation of the internal restoring forces, which is performed element-by-element in every iteration step. The present work constitutes the first of two papers presenting a method to simulate kinematic nonlinear structures more efficiently. It involves applying a reduced basis with modal derivatives representing the nonlinearities of the system in an efficient way. Previously, the modal derivatives have been determined from a set of approximate governing equations. In the present paper, a novel set of equations governing the complete modal derivatives is derived. This is done by introducing a Taylor series into the free undamped kinematic nonlinear equations of motion. Also, the approximate governing equations are improved by introducing a novel geometric restriction. By way of an example, it is shown that only the modal derivatives determined from the complete set of equations are consistent with the Taylor series. In the second paper, it is shown that the novel modal derivatives may be used in a so-called Taylor basis and that they improve the computational time and stability significantly.     

多级可分离式AUV系统设计与仿真分析

多级可分离式自主水下航行器(MS-AUV)可搭载多种不同功能的载荷舱,并在目标海域完成载荷舱布放。其在海洋探测,海防等领域具有较高的应用价值。对MS-AUV进行了主体结构和分离机构的设计和研究,其中功能载荷舱与航行器本体采用真空连接方式,实现多级连接,降低了机构的复杂性,提高了载荷舱分离运动的稳定性和安全性。为了研究载荷舱与航行器分离的安全性,采用CFD和六自由度(6-DOF)刚体运动学的耦合方法来模拟其在水下的分离运动。在仿真过程中,采用弹簧光顺和局部重构混合网格生成方法的非结构化动态网格可以很好地适应大距离多体分离运动。仿真结果表明,在一定工况条件下,提高MS-AUV初始航行速度V0和分离机构弹簧刚度K有利于载荷与航行器本体分离。通过上述研究工作,验证了载荷分离方法的可行性,缩短研制周期,降低设计成本,对多级可分离式AUV样机的设计制造具有重要的参考价值。