Stresses due to vertical subsurface loading for an inhomogeneous cross‐anisotropic half‐space

In this article, we present the solutions for the stresses induced by four different loads associated with an axially loaded pile in a continuously inhomogeneous cross‐anisotropic half‐space. The planes of cross‐anisotropy are parallel to the horizontal surface of the half‐space, and the Young's and shear moduli are assumed to vary exponentially with depth. The four loading types are: an embedded point load for an end‐bearing pile, uniform skin friction, linear variation of skin friction, and non‐linear parabolic variation of skin friction for a friction pile. The solutions for the stresses due to the pile load are expressed in terms of the Hankel integral and are obtained from the point load solutions of the same inhomogeneous cross‐anisotropic half‐space which were derived recently by the authors (Int. J. Rock Mech. Min. Sci. 2003; 40 (5):667–685). A numerical procedure is proposed to carry out the integral. For the special case of homogeneous isotropic and cross‐anisotropic half‐space, the stresses predicted by the numerical procedure agree well with the solutions of Geddes and Wang (Geotechnique 1966; 16 (3):231–255; Soils Found. 2003; 43 (5):41–52). An illustrative example is also given to investigate the effect of soil inhomogeneity, the type and degree of soil anisotropy, and the four different loading types on the vertical normal stress. The presented solutions are more realistic in simulating the actual stratum of loading problem in many areas of engineering practice. Copyright © 2004 John Wiley & Sons, Ltd.     

A hybrid Bayesian back‐propagation neural network approach to multivariate modelling

There is growing interest in the use of back‐propagation neural networks to model non‐linear multivariate problems in geotehnical engineering. To overcome the shortcomings of the conventional back‐propagation neural network, such as overfitting, where the neural network learns the spurious details and noise in the training examples, a hybrid back‐propagation algorithm has been developed. The method utilizes the genetic algorithms search technique and the Bayesian neural network methodology. The genetic algorithms enhance the stochastic search to locate the global minima for the neural network model. The Bayesian inference procedures essentially provide better generalization and a statistical approach to deal with data uncertainty in comparison with the conventional back‐propagation. The uncertainty of data can be indicated using error bars. Two examples are presented to demonstrate the convergence and generalization capabilities of this hybrid algorithm. Copyright © 2003 John Wiley & Sons, Ltd.     

Repeat Ground Track Orbits of the Earth Tesseral Problem as Bifurcations of the Equatorial Family of Periodic Orbits

Orbits repeating their ground track on the surface of the earth are found to be members of periodic-orbit families (in a synodic frame) of the tesseral problem of the Earth artificial satellite. Families of repeat ground track orbits appear as vertical bifurcations of the equatorial family of periodic orbits, and they evolve from retrograde to direct motion throughout the 180 degrees of inclination. These bifurcations are always close to the resonances of the Earth's rotation rate and the mean motion of the orbiter.     

MULTICOMPONENT DETERMINATIONS BY A MEMBRANE-DISCRIMINATED GAS PHASE ANALYZER AND SUCCESSIVE REGRESSION IN THE FIDUCIARY REGION

A membrane-discriminated gas phase analyzer is proposed for multicomponent determinations. Nitrogengas flows countercurrent through outer and inner channels in a tube-in-tube arrangement. The onlycommunication between the two channels occurs through a 500μm aperture covered by a porous PTFEmembrane. A mixture of organic compounds (up to four components) is injected into the inner channelby a heated backflushed injector and the sample components diffusing into the outer channel aremonitored by a flame ionization detector (FID). A calibration set, consisting of pure components, binary,ternary and quaternary mixtures (a total of 64 samples), provides the known data base: temporal profilesof the FID output as a function of sample composition, Although the overall response behavior is nota linearly additive function of individual analyte concentrations, the use of successive inverse multiplelinear regression (while continually altering the choice of the calibration samples considered for theforward regression, on the basis of the most recent values of the predicted unknown sample composition)is shown to yield analytical results for unknown samples that are in good agreement with their true values.     

Meixner functions for derivation of the unit hydrograph

The Meixner functions are utilized to relate the effective rainfall, the direct runoff and the unit hydrograph through linkage equations. The linkage equations are then employed to derive the unit hydrograph for given rainfall-runoff data on a small agricultural watershed. These functions are tested with regard to their ability to reproduce and predict the direct runoff hydrograph. The Meixner functions are found to be an effective analytical tool for hydrograph synthesis. Further, they compare well with the least squares and linear programming methods of the unit hydrograph derivation.     

Variation of chemical composition of alkaline granitic rocks in the central part of the Kola Peninsula

Chemical composition and origin of alkaline granitic rocks in the Keivy area on the Kola Peninsula were investigated. Linear correlation analysis and principal-component analysis were used to determine the interrelation of major petrogenetic elements in alkaline granite and surrounding alkaline metasomatites. Estimates of linear correlation coefficients turned out to be different, and principal-component analysis of the chemical data revealed that there were three main components influencing variation of chemical composition. These factors can be interpreted in terms of petrological processes, which are different for alkaline granite and for the surrounding metasomatites, indicating a different origin of the rocks.     

The extent of desertification on Saudi Arabia

Desertification is the process that turns productive deserts into non-productive deserts as a result of poor land-management. Desertification reduces the ability of land to support life, affecting wild species, domestic animals, agricultural crops and humans. The reduction in plant cover that accompanies desertification leads to accelerated soil erosion by wind and water. South Africa is losing approximately 300–400 million tons of topsoil every year. As vegetation cover and soil layer are reduced, rain fall impact and run-off increases. This paper discusses the extent of desertification, its potential threat to sustained irrigated agriculture and possible measures adopted to control ongoing desertification processes to minimize the loss of agricultural productivity in an arid country such as the Kingdom of Saudi Arabia.     

在空间抽象中线状目标间拓扑关系的等价转换

拓扑关系在抽象过程中的等价转换是维护多尺度空间关系一致性的基础。本文以空间拓扑关系组合推理所描述的线状目标之间的拓扑关系为例,采用成分抽象的等价转换方法,研究了线之间拓扑关系等价转换的原则,并绘出了相应的等价转换图。     

面向分类的高光谱影像局部线性嵌入算法研究

局部线性嵌入算法(LLE)能很好保存数据点的局部性质,因此有很好的数据可视化效果,但它不是一种很好的面向分类的特征提取方法。因为它存在样本外点学习能力差和忽略了样本类别信息的缺点。对此,本文提出一种分类型局部线性嵌入算法。所提方法通过计算重构误差来判定样本类别,并引进平移向量和缩放因子对距离修正,显著提高类别可分性。在对高光谱影像进行分类的试验中验证了该方法的有效性。