The analysis and interpretation of some special properties of higher order symmetric lamb waves: the case for plates.

Results derived from exact linear homogeneous elastodynamic theory are used for two-dimensional unloaded plates in order to understand certain features generated by proper symmetric Lamb modes. It is shown that S1 modes for all elastic materials have a phase velocity defined below the usual critical frequency and which initially exhibits anomalous dispersion (has a negative slope with respect to frequency). Over a certain range, it has a phase velocity that is double valued. In addition, there are an infinite number of proper symmetric Lamb modes that have this characteristic for materials with a Poisson ratio equal to 1/3. It also appears that all A3n modes are anomalous when V(L) < or = 2 V(T). The cause and implication of these effects are examined, including an associated negative group velocity over a small frequency zone for these modes. Further, it is noted that all proper symmetric Lamb modes have a plateau region in phase velocity with respect to wave number. It is shown that this always occurs for a phase velocity corresponding to the longitudinal bulk velocity of the elastic material. These issues are examined along with how one may obtain material parameters and possibly plate thickness from their dispersion curves.

Dispersion of circumferential waves on evacuated, water-loaded spherical steel shells.

The phase-velocity dispersion curve of the A0 Lamb wave on a free plate tends to zero at the vanishing frequency while on an evacuated, free spherical shell, it turns upward. On a fluid-loaded shell, and for the analogous circumferential A0 wave, it again tends to zero, however, while a new A-wave (Scholte-Stoneley wave) which gets added due to fluid loading, is the one whose dispersion curve turns upward. This phenomenon is studied here for a thin stainless-steel shell on the basis of dispersion curves calculated from 3D elasticity theory, or obtained from the calculated shell resonances, and is explained by the physical nature (shell-borne or fluid-borne) of appropriate circumferential wave portions. We also establish connections with the previously found partial dispersion curves.

Circumferential waves on an immersed, fluid-filled elastic cylindrical shell.

The existence of various types of circumferential waves, both predominantly shell or fluid borne, and the repulsion of their dispersion curves is discussed here for an infinite, thin elastic, circular-cylindrical shell immersed in a fluid and filled with another fluid. The study is based on an analytic calculation of the partial-wave resonances in the acoustic scattering amplitude of a normally incident plane wave. A large number of cases of repulsion are found in the phase-velocity dispersion curves of the various types of circumferential waves due to the shell-fluid coupling.

Deciphering the scattering code contained in the resonance echoes from fluid-filled cavities in solids.

From the echoes of elastic waves incident on inclusions in solids, one may extract certain resonance features. These "spectral lines" and their widths form a code identifying the material composition of the inclusion in a way that resembles spectroscopy. This idea finds applications in geophysics, materials science, and any field dealing with materials containing inclusions.

Telecommunication with neutrino beams.

Collimated neutrino beams in the energy range 1 to 100 gigaelectron volts, now available from high-energy proton accelerators, are proposed as a potential means for telecommunication over global distances. Quantitative estimates of the feasibility of this proposal based on a particular detector configuration are presented.