A particular analytical solution of a steady-state flow of a groundwater mound

Semi-inverse method with successive conformal mapping are used to obtain a particular solution of the problem of steady-state flow of a groundwater mound. Groundwater flow parameters are evaluated, and examples of calculations are given. The obtained solutions coincide with available exact solutions in particular cases.     

Improvements to Remote Sensing Using Fuzzy Classification, Graphs and Accuracy Statistics

This paper puts together some techniques that have been previously developed by the authors, but separately, relative to fuzzy classification within a remote sensing setting. Considering that each image can be represented as a graph that defines proximity between pixels, certain distances between the characteristic of contiguous pixels are defined on such a graph, so a segmentation of the image into homogeneous regions can be produced by means of a particular algorithm. Such a segmentation can be then introduced as information, previously to any classification procedure, with an expected significative improvement. In particular, we consider specific measures in order to quantify such an improvement. This approach is being illustrated with its application into a particular land surface problem.     

Love waves in a two-layered crust overlying a vertically inhomogeneous halfspace I

Summary The frequency equation is derived for the propagation of Love waves in a two layered crust overlying an inhomogeneous half-space. While exact solutions of the differential equation involved are obtained in some particular cases, both an asymptotic series and the WKBJ approximations are discussed for the solution in the general case. The asymptotic series solution and the WKBJ solution are compared with each other and with the asymptotic expansion of the exact solution. There is a good agreement between various results. It is shown that some of the existing results can be derived as particular cases of the general results obtained in this investigation.     

Ray-centred coordinate systems in anisotropic media

Whereas the ray-centred coordinates for isotropic media by Popov and Pšenčík are uniquely defined by the selection of the basis vectors at one point along the ray, there is considerable freedom in selecting the ray-centred coordinates for anisotropic media. We describe the properties common to all ray-centred coordinate systems for anisotropic media and general conditions, which may be imposed on the basis vectors. We then discuss six different particular choices of ray-centred coordinates in an anisotropic medium. This overview may be useful in choosing the ray-centred coordinates best suited for a particular application. The equations are derived for a general homogeneous Hamiltonian of an arbitrary degree and are thus applicable both to the anisotropic-ray-theory rays and anisotropic common S-wave rays.     

The role of natural E-region plasma turbulence in the enhanced absorption of HF radio waves in the auroral ionosphere:Implications for RF heating of the auroral electrojet

Physical processes which affect the absorption of radio waves passing through the auroral E-region when Farley-Buneman irregularities are present are examined. In particular, the question of whether or not it is legitimate to include the anomalous wave-enhanced collision frequency, which has been used successfully to account for the heating effects of Farley-Buneman waves in the auroral E-region, in the usual expression for the radio-wave absorption coefficient is addressed. Effects also considered are those due to wave coupling between electromagnetic waves and high-frequency electrostatic waves in the presence of Farley-Buneman irregularities. The implications for radio-wave heating of the auroral electrojet of these processes are also discussed. In particular, a new theoretical model for calculating the effects of high-power radio-wave heating on the electron temperature in an electrojet containing Farley-Buneman turbulence is presented.     

Effect of couple-stresses in a semi-infinite elastic medium due to impulsive twist over the surface

Summary Displacement due to impulsive twist in a semi-infinite elastic medium is calculated in the light of Cosserats theory of couple stresses [1, 2]. Numerical results are obtained for a particular     

History of forest hydrology

Hydrology as a science and a technology is examined, as are some of the myths on the role of forests in hydrology and water resources. The history of catchment area research is traced, in Europe, in the USA and in East Africa, with particular reference to forest hydrology and, in the earlier years, to water quantity rather than water quality. The importance of associating physical process studies with hydrological systems' investigations, to enhance understanding of why particular catchments behave as they do, is stressed. Recent advances in hydrochemistry have been exploited to elucidate water flow paths within experimental catchments. Stimulated by requirements for research into acidification of surface waters, research catchments have proved to be valuable outdoor laboratories from which a much improved understanding of the flow processes has been achieved. Conflicting claims about the impacts of forestry are described and discussed.     

The use of damage functionals in earthquake engineering: A comparison between different methods

The behaviour of the EPP-SDOF model under seismic actions is analysed herein by different ‘damage functionals’ to define collapse under cyclic loading. In particular, the damage functionals based on the concept of maximum ductility and dissipated plastic energy are first compared. Afterwards the methods of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue are reviewed and extensively analysed. Comparisons in the case of simple cyclic histories and in terms of acceleration collapse spectra are carried out with reference to significant earthquake records. In particular, it is shown in which cases the damage functionals of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue, completely defined by the value of a single parameter, degenerate in the limit methods of ductility or dissipated energy and in which cases they provide similar results.     

Voraussetzung und Grenzen der Qualitätssicherung in der Wasseranalytik

A discussion is presented on the conditions required and limitations of the guaranteeing of quality in water analysis as the basis for the necessary standardization of analytical methods. The following concepts are of particular importance: principle of analysis, method of analysis, technique of analysis, specification for analysis, measured value, analytical value, result of measurement, result of analysis, precision, repeatability, reproducibility, detection limit, determination limit, sensitivity and rate of retrieval. Prequisite for the ensuring of quality proper are the standard addition method and the ring analysis. In the water analysis the guaranteeing of quality is of particular importance due to the multifarious matrix as well as for the interpretation of the analytical results as a basis for important decisions in the national economy.     

大型直流电压发生器塔架结构地震响应分析

本文以某一大型直流电压发生器塔架结构为例,建立有限元计算模型,采用调幅正弦五波、Taft地震波、El-Centro地震波、云南澜沧地震波和正弦三波5种地震动输入,通过数值计算,讨论了不同输入地震波对于结构抗震设计的影响。结果表明,地震作用效应在这类特种结构的组合响应中起重要影响,采用调幅正弦五波、正弦三波作为地震输入,过分夸大了实际的地震作用效应。最后,对这类特种结构的输入地震动提出了相应建议。     

A NUMERICAL STUDY OF LAMB'S PROBLEM*

This paper considers propagation of elastodynamic waves in an imperfectly elastic half-space. Two different excitation modes are investigated: a buried source of compressional waves and a vertically directed areal load applied to the surface. Numerical integration of the analytical solution of the wave equation allows study of the vertical and horizontal components of displacement and/or particle velocity anywhere in the half-space. One case of particular interest concerns the examination of particle displacement and velocity at the surface in a circular area above the source. In another application seismograms generated by an explosive buried source are contrasted with seismograms generated by the transient application of a vertically directed load to the free surface. Still another application of considerable practical interest concerns the study of the nongeometrical pS—wave, in particular its characteristics as functions of range and depth. Finally, in the last application the behavior of a rarely observed wave (denoted here by the letter U) is studied in both elastic and visco-elastic half-spaces.     

Transverse free vibrations of continuous bridges with abutment restraint

This paper analyzes the dynamic behaviour of continuous bridges with transverse abutment restraint. These are a particular class of multi‐span bridges whose transverse motion is restrained at the abutments. The transverse dynamic behaviour of these partially‐restrained bridges is described by a model consisting of a two‐dimensional simply‐supported beam with intermediate visco‐elastic restraints. A minimal set of characteristic problem parameters that completely describe the dynamic response is initially identified and an analytical solution is developed for particular configurations. The influence of these characteristic parameters on the properties of the dynamic systems are analyzed by considering the undamped and the damped free vibrations separately. Successively, in order to cover more general and complex configurations of realistic bridges, an extension of the definition of the characteristic parameters is proposed. The results obtained considering selected case studies are finally presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Seismic risk mitigation technique for art objects: experimental evaluation and numerical modelling of double concave curved surface sliders

The opportunity and the advantages of applying base isolation technologies developed for civil structures to small objects are investigated and some considerations related to the scale effects are discussed. A series of experimental tests carried out at SRMD facility in San Diego are presented with the aim to investigate the dynamic response of a system designed to simulate a sculpture isolated by means of Double Concave Curved Surface Sliders. Such devices are specifically re-designed to fit the peculiar situation of light weight objects. In particular the samples used in the experimentation are designed with geometric and inertia characteristics fit for representing the Michelangelo’s sculptures exposed at the “Galleria dell’Accademia” in Florence, Italy. Finally, the main aspects concerning the numerical simulation of the seismic response of the proposed isolated system are discussed, also to investigate the efficiency of the existing numerical models, which are developed for traditional devices, when they are applied on such small and particular objects. The results of the experimental/numerical campaign show a general efficiency of the isolation system in terms of limiting the transferred action. Further study is needed to understand more clearly some local unexpected phenomena emerged from the experimental tests.     

Some exact solutions of unsteady boundary layer equations-I

Summary Unsteady boundary layer flows generated in a homogeneous, non-rotating viscous fluid are considered. The method of Laplace transform is used to obtain exact solutions of the unsteady boundary layer equations in a more general situation. The structures of the unsteady velocity field and the associated boundary layers are determined. Several particular solutions are recovered as special cases of the present general theory. The physical implications of the mathematical results are investigated.     

Two-dimensional scattering of SH waves due to a discontinuity in bedrock

The direct boundary integral equation technique is applied to determine the impact on surface amplification caused by an inhomogeneity in a bedrock half-space. The particular soil-rock configuration studied is one in which a soil layer rests on a rock half-space which includes a rock inclusion. The particular rock inclusion considered for this study is a semi-infinite rock layer with its upper boundary bordering the soil layer. Materials are considered viscoelastic except for the section of the rock half-space below the level of the rock inclusion which is considered elastic. A parametric study is performed to determine controlling factors for surface displacement due to a vertically incident shear wave. The study includes varying the stiffness and the thickness of the inclusion for a range of frequencies. Solutions from a one-dimensional analysis are compared with the results of a two-dimensional analysis in order to establish limits inside of which a two-dimensional analysis is required. Copyright © 1999 John Wiley & Sons, Ltd.     

Nonlinear aspects of long shelf waves

Abstract

Continental shelf waves are examined in the long wavelength limit, and the effects of weak topographic dispersion calculated. These dispersive effects are then balanced against nonlinear terms and a Korteweg-de Vries equation is derived to describe the evolution of the wave amplitude. Two particular cases are worked in detail.     

Electromagnetic research in the ocean

The results of electromagnetic researches at sea and in the oceans are considered. Those in the U.S.S.R. are given particular attention.     

The decay of gravity waves

Summary The decay of waves of small amplitude in a viscous liquid of finite depth is investigated. It is shown that the various modes may be conveniently classified and that in many limiting cases the modes of aperiodic decay are of particular importance. Detailed numerical results are given for these modes.     

Admissible nested covariance models over spheres cross time

Nested covariance models, defined as linear combinations of basic covariance functions, are very popular in many branches of applied statistics, and in particular in geostatistics. A notorious limit of nested models is that the constants in the linear combination are bound to be nonnegative in order to preserve positive definiteness (admissibility). This paper studies nested models on d-dimensional spheres and spheres cross time. We show the exact interval of admissibility for the constants involved in the linear combinations. In particular, we show that at least one constant can be negative. One of the implications is that one can obtain a nested model attaining negative correlations. We provide characterization theorems for arbitrary linear combinations as well as for nonconvex combinations involving two covariance functions. We illustrate our findings through several examples involving nonconvex combinations of well-known parametric families of covariance functions.     

Wave-propagation in uniaxially-stressed elastic media

Summary The propagation of waves of small amplitude in an elastic medium, with a particular form of strain-energy function, and subjected to a large homogeneous uniaxial stress, is considered in detail. The main characteristics, including speed and polarisation, of these waves in an unbounded medium are calculated numerically, and the existence and general properties of Rayleigh waves on the surface of a semi-infinite medium are investigated.