Search

The use of surface waves of the Rayleigh type enables the properties of the component materials of a layered structure, such as a pavement, to be determined. The method has the advantage that the measurements are performed dynamically, thus making an allowance for the inertial and frequency dependent response of the pavement. The velocity of the waves is not a constant, but exhibits dispersion. The manner of the variation of the wave velocity is used to determine the properties of the surface and subsurface materials of the structure. Inverse problems are involved in interpreting the results. Wave propagation in elastic plates is analogous to propagation in layered spaces and therefore the free plate system can be used to model the surface layer of a single layered pavement structure. A direct algebraic inverse technique has been developed and used to calculate the thickness of the surface layer of a pavement system employing free plate analysis. To assess the effectiveness and reliability of the proposed technique, the application of the method to a published set of experimental data obtained in the field is presented and discussed. It is shown that the experimental results and the algebraic solutions are in good agreement, indicating that the proposed method can be used to determine the thickness of the pavement surface layer without resorting to excavation and in a very quick and economic manner. [ABSTRACT FROM AUTHOR]

The Stroh formalism is a powerful and elegant mathematical method developed for the analysis of the equations of anisotropic elasticity. The purpose of this exposition is to introduce the essence of this formalism and demonstrate its effectiveness in both static and dynamic elasticity. The equations of elasticity are complicated, because they constitute a system and, particularly for the anisotropic cases, inherit many parameters from the elasticity tensor. The Stroh formalism reveals simple structures hidden in the equations of anisotropic elasticity and provides a systematic approach to these equations. This exposition is divided into three chapters. Chapter 1 gives a succinct introduction to the Stroh formalism so that the reader could grasp the essentials as quickly as possible. In Chapter 2 several important topics in static elasticity, which include fundamental solutions, piezoelectricity, and inverse boundary value problems, are studied on the basis of the Stroh formalism. Chapter 3 is devoted to Rayleigh waves, for long a topic of utmost importance in nondestructive evaluation, seismology, and materials science. There we discuss existence, uniqueness, phase velocity, polarization, and perturbation of Rayleigh waves through the Stroh formalism. [ABSTRACT FROM AUTHOR]

Building on the terms introduced in Chapter 2, in Chapter 3, Rayleigh and Rice processes are dealt with as reference models to describe frequency-nonselective mobile radio channels. These are first described in general in Section 3.1. Then, a description of the most frequently used Doppler power spectral densities (Jakes or Clarke power spectral density and Gaussian power spectral density) and their characteristic quantities, such as the Doppler shift and the Doppler spread, is given (Section 3.2). After that, in Section 3.3, the statistical properties of the first kind (probability density of amplitude and phase) and of the second kind (level-crossing rate and average duration of fades) are investigated. Finally, Chapter 3 ends with an analysis of the statistics of the duration of fades. [ABSTRACT FROM PUBLISHER]

Chapter 2 deals with the fundamentals of radio propagation at VHF and UHF. It covers: Antenna gain and directivity; Propagation in free space and over a reflecting surface; Reflection coefficients for horizontal and vertical polarisation; Surface roughness and the Rayleigh criterion; The effect of the atmosphere, including effective earth radius, refraction and ducting. [ABSTRACT FROM PUBLISHER]