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The dispersive wave motion in solids with microstructure is considered in the one-dimensional setting in order to understand better the mechanism of dispersion. It is shown that the variety of dispersive wave propagation models derived by homogenization, continualisation, and generalization of continuum mechanics can be unified in the framework of dual internal variables theory.

The Mindlin-type model is used for describing longitudinal waves in microstructured solids. This model involves explicitly the internal parameters and therefore tends to be rather complicated. An hierarchical approximation is derived, which is able to grasp the main effects of dispersion with wide variety of parameters. Attention is paid to the internal degrees of freedom of the microstructure and their influence on the dispersion effects. It is shown how the internal degrees of freedom can change the effects of dispersion.

The CELL-tainer™ is a novel wave-motion bioreactor characterized by very high mass-transfer capacities (kLa up to 200 h−1) due to an optimized wave motion. By comparison, this mass-transfer capacity is at least a factor 5 higher than that of stirred tank cell-culture bioreactors. As such, no oxygen supplementation of the overlay is required for oxygenation and the carbon dioxide stripping capacity is sufficient to prevent pCO2 build-up.

The objective of this study is to add prototype data for estimating the performance of a coastal drain system. Small-scale model experiments aimed at understanding the mechanisms that make coastal drain systems effective were carried out. The model experiments gave us qualitative information on the relevant mechanisms, as well as encougaring results. However, our experiments were done under conditions in which the role of the drain in sediment movement was magnified compared to the effect of wave motion. Some caution is thus advisable when the experimental results are extended to estimate the performance of prototype-scale coastal drain systems. In order to be able to evaluate the performance of a coastal drain system and establish the designing procedures, prototype scale-detailed data that includes information on waves, sediments, beach profiles, drainage and so forth, together with the development of numerical models, is necessary. This paper, firstly briefly discusses where to install drainpipes, then discusses the experimental results.

The concepts of the theory of nonlinear waves are briefly analyzed. Two examples are given characterizing the nonlinear effects in wave propagation. The first deals with short-living solitary waves in a dispersive medium and the second with interaction of two-dimensional nonlinear waves.

After presenting the ideas on modelling nonlinear waves, some selected case studies and general concepts of complexity, one should sum up what is said in a more concise form.

The small ion-neutral drift speeds attained in MHD waves lead to a significant increase in the rates of several important ion-molecule reactions. The effect on the deuterium chemistry of dark clouds could allow MHD wave motion to be observed directly. The results of some recent observations to test this theory are outlined.

Whole-field kinematic measurements are presented for steep, steady waves travelling on strongly sheared currents, concentrating on the region between trough and crest level. For slab currents, the crest kinematics and wave parameters were found to be correctly obtained by using Doppler shifting and standard wave theories. When the current was sheared, the crest kinematics were found to be well predicted by adding the results of an irrotational model to the stretched current profile, although this approach did not yield good predictions in the trough. The average shear was found to be reduced, in the presence of waves, from the undisturbed value, in agreement with the findings and predictions of other authors.

The proceedings of the workshop held in La Spezia, Italy, June 1990, consist of five parts reflecting the sessions held at the workshop: experimental results relating acoustic and oceanographic variability; wave motion and fine structure affecting acoustic propagation small scale variability; stocha

Using the reductive perturbation method, wave propagation in fluid-filled nonlinear viscoelastic thin tubes is investigated in the long wave approximation. For different scales of the relaxation constant τ the Korteweg-de Vries (KdV), Burgers and Korteweg-de Vries-Burgers (KdVB) equations are obtained.

The purpose of this general discussion on e.m. scattering after the formal scientific presentations at the workshop was to ascertain the present state of knowledge in the field, assess the quality of the predictions, and to arrive at some specific recommendations for future research. Frank and active discussions took place in regard to the status of e.m. scattering theories/models for the ocean surface (see Table I). During the formal presentations it was clear that the two-scale model (Wright, 1968; Bass and Fuks, 1979) when properly applied, (Thompson, 1988; Thompson et al., 1988) yields just as good agreement (within a couple of decibels) as the Kirchhoff approximation (Holliday et al., 1986, 1987) when applied to the SARSEX data on SAR imagery (L and X band) for internal waves in the New York Bight. Both of these comparisons only deal with cross section effects, the distortion in the image intensity from wave motion and current variations affecting the phase of the e.m. backscattered fields is not included. To match the theoretical predictions with the measurements, the enhancement in slopes by the internal waves of both the long (greater than 1 m length) and intermediate (of the order of 1 m length) gravity waves should be included in the tilting of the Bragg resonant waves of wave number 2ko sinθ, ko is the wavenumber of the e.m. radiation in free space and θ is the angle of incidence.

Before studying wave motion in a magnetoplasma, it is convenient to study a simpler problem. This is one in which the applied electric field, although oscillatory, is uniform in space. We are then considering a homogeneous plasma that is simultaneously subject to a uniform steady magnetic field of flux density B 0 and to a uniform electric field E that oscillates with angular frequency ω