Heat Diffusion and Random Media
Nowadays random media are structures of paramount importance for physicists and engineers. More and more disordered structures such as glasses, sintered materials, and concrete belong to our everyday world and it is of importance to be able to describe their specific properties when we compare them to homogeneous materials. The first attempt usually consists in replacing the random media by an effective medium whose properties reflect a specific physical behavior (e.g. the thermal or the electric conductivity of a polycrystalline sample). Although very useful, the previous approach has been found to be limited in its ability to describe most of the dynamical processes, other than those occurring in the “long time” or “low frequency” range where the sample behaves like a homogeneous medium. Indeed, between this and the microscopic scale, dealing with the individual entities of the structure, one can find a full range of anomalous behaviors which are more clearly revealed by studying diffusive transport. Among all the diffusion phenomena, that of heat offers certain specific advantages: the ability to operate with various kinds of materials (insulators or conductors), the possibility of repeating an experiment, and nondestructive and noncontact testing. We intend to illustrate how, by following the heat diffusion temporal behavior, rough surfaces and random media which can be mapped on fractal structures may be characterized.
KeywordsLution Acoustics Percolate Congo Line Source
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