A statistical analysis of exploration geochemical data for uranium

This paper describes a statistical analysis of reconnaissance exploration geochemical data for uranium. Three sets of data were analyzed, as they related to: (a) Charlotte-Winston-Salem and (b) Charlotte two-degree NTMS quadrangles of the south-eastern U.S.A. The coefficient of variation for uranium in each of the three sets of data was less than unity and hence no transformation of the original variable was needed. These data were subjected to correlogram analysis. A first-order Markovian model of the type: Y₀ exp (-a |p|) was fit by the least-squares method to serial correlation coefficients of these data using the method proposed by Deming (1948). The model was tested by computing the variance-volume relationship for assumed individual blocks of unit length. The noise in the input (record) was eliminated by the application of an optimum bilateral exponential smoothing technique developed by Agterberg. A comparison of spectral density estimates obtained by a maximum entropy method employing Yule-Walker equations and the Burg algorithm was also made. The prediction error coefficients needed to determine the order of the autoregressive process and hence the spectral densities were determined in both cases for the three sets of data.On leave from National Geophysical Research Institute, Hyderabad-7, India.     

On the efficiency and predictability of strain energy for the evaluation of liquefaction potential: A numerical study

Strain energy concept has been employed by the researchers for the assessment of liquefaction phenomenon which is a disastrous type of earthquake-induced failure in saturated soils. The efficiency and predictability conditions of strain energy concept for liquefaction potential assessment are investigated herein using effective stress numerical analyses. Several earthquake ground motions were introduced to the base of a calibrated numerical model using an advanced fully coupled constitutive model. Results of the numerical analyses indicate that earthquake-induced excess pore pressure is more rigorously proportional to strain energy compared with the other examined intensity measures. Subsequently, a simple relationship was derived using the results of dynamic analyses to predict cumulative strain energy density in terms of magnitude, source to site distance, and effective overburden pressure. This relationship, which tries to guarantee the predictability condition of strain energy demand, has demonstrated a successful capability in discrimination between the liquefied and non-liquefied case histories recorded after several well-known earthquakes. This study has provided a practical linkage between numerical analysis and field observations. Finally, it is concluded that although strain energy approach possesses a great conceptual efficiency in liquefaction potential assessment, its precise prediction in actual field conditions involves some difficulties.     

A comparative review of commercially-available software for soil slope stability analysis

Summary The main purpose of this paper is to carry out a comparative review of four commercial computer programs for the stability analysis of soil slopes. The review is carried out in two parts and should prove useful for potential users of the software. Part I reviews the facilities offered in terms of the range of limit equilibrium methods, the geotechnical modelling abilities, the operational features and the supporting documentation, and includes a general impression of friendliness. Part II assesses the use, accuracy and validity of each program by presenting and discussing the results of a number of model tests. Also included is a brief discussion of slope stability analysis, in particular the limit equilibrium method. The requirements of a practical computer program for soil slope stability analysis are defined and then used as a means of assessing the effectiveness of each program.     

The use of water-extractable Cu,Mo, Zn,As, Pb concentrations and automated mineral analysis of flue dust particles as tools for impact studies in topsoils exposed to past emissions of a Cu-smelter

An exploratory study has been conducted to test the utility of automated mineral analysis observations to identify flue dust particles in topsoils exposed for several decades to emissions of a copper smelter. The methods used are readily available in mining countries. To identify the most impacted sites, the Cu, Zn, Pb, Mo and As levels in water and diluted sulphuric acid extractions of four topsoil size fractions (833–495 μm, 246–148 μm; 74–38 μm; <38 μm) were analysed. X-ray diffraction analyses were used to demonstrate the mineralogical degradation of smectite phases when approaching the smelter. Flue dust particles in different states of conservation in topsoils were directly observed by scanning electron microscopy (SEM) aided by energy dispersive detection of X-rays. Qemscan^® scanning of dispersed topsoil preparations (10,000 particles) pinpoints smelter particles by their density; flue dust pearls can be tracked by sorting particles according to their sphericity, clearly identifying them as pyrometallurgical products. When sorting soil particles by mineral groups (e.g. sulphides), an increase in this phase group can be observed when approaching the smelter. SEM resolution limits observations to particles larger than 2–3 μm. Smaller particles can be observed by transmission electron microscopy, although observer experience and the availability of equipment time are essential as is the case for SEM.     

航空伽玛射线全能谱数据分析方法的理论研究

通过航空伽玛能谱测量的源项分析和测量模型建立,发现航空伽玛能谱测量谱是各种源项能谱成分的合成谱。对航空伽玛射线全能谱分析方法给出了其数学分析式,其通用式可表示为矩阵式,对于矿产勘查和核环境与核应急等不同的应用领域能表达成相应的展开式。理论研究表明,航空伽玛全谱法不需要附加的上测探测器,就可直接解决大气氡修正问题,还将具有较好的经济效益。     

The statistical study of hydraulic geometry: A new direction for compositional data analysis

Hydraulic exponents and unit hydraulic exponents are unit-sum constrained, which requires that they be analyzed by statistical methods designed for compositional data. Though uncertainties remain regarding selection of the best constraining operation and method of handling departures from the unit-sum constraint, neither category of uncertainty should be an impediment to the selection of the appropriate statistical methodology. In a small sample study, the hydraulic geometry of different types of streams were compared: (1) semi-arid: perennial vs. ephemeral; (2) tropical: Puerto Rico vs. West Malaysia; and (3) semi-arid vs. tropical (by pooling the previous data sets). All three comparisons revealed statistically significant differences in either logratio mean vectorsor logratio covariance matrices but not both. All six categories of data had logistic normal distributions. Because the derivatives at a given discharge of curvilinear hydraulic geometry relationships and hydraulic exponents on either side of the breakpoints of piecewise linear relationships are unit-sum constrained, they also can be studied by compositional methods. However, the compositional approach is limited in cases where distributions have large departures from logistic normality and for streams that have negative hydraulic exponents.     

Hybrid time integration and coupled solution methods for nonlinear finite element analysis of partially saturated deformable porous media at small strain

The goal of the paper is to determine the most efficient, yet accurate and stable, finite element nonlinear solution method for analysis of partially saturated deformable porous media at small strain. This involves a comparison between fully implicit, semi‐implicit, and explicit time integration schemes, with monolithically coupled and staggered‐coupled nonlinear solution methods and the hybrid combination thereof. The pore air pressure p_a is assumed atmospheric, that is, p_a=0 at reference pressure. The solid skeleton is assumed to be pressure‐sensitive nonlinear isotropic elastic. Coupled partially saturated ‘consolidation’ in the presence of surface infiltration and traction is simulated for a simple one‐dimensional uniaxial strain example and a more complicated plane strain slope example with gravity loading. Three mixed plane strain quadrilateral elements are considered: (i) Q4P4; (ii) stabilized Q4P4S; and (iii) Q9P4; “Q” refers to the number of solid skeleton displacement nodes, and “P” refers to the number of pore fluid pressure nodes. The verification of the implementation against an analytical solution for partially saturated pore water flow (no solid skeleton deformation) and comparison between the three time integration schemes (fully implicit, semi‐implicit, and explicit) are presented. It is observed that one of the staggered‐coupled semi‐implicit schemes (SIS(b)), combined with the fully implicit monolithically coupled scheme to resolve sharp transients, is the most efficient computationally. Copyright © 2015 John Wiley & Sons, Ltd.