Twenty‐seven sets of elastic modulus‐porosity data spanning ranges > 20% in porosity were fitted by linear, exponential, Hasselman, and 2/3‐power relations. The fits were tested for goodness of fit, for extrapolation to zero‐porosity moduli, and for consistency in determining zero‐porosity Poisson's ratios and bulk moduli. On the whole, the linear relation appears to give a superior fit. This result is seen as supportive of self‐consistent theoretical calculations of moduli in porous media. Nonlinear data sets are attributed to a tendency for the spheroidicity of pores to increase with porosity.

Nuclei colliding at energies in the MeV's break into fragments in a process that resembles a liquid-togas phase transition of the excited nuclear matter. If this is the case, phase changes occurring near the critical point should yield a "droplet" mass distribution of the form ≈A −τ , with τ (a critical exponent universal to many processes) within 2 ≤ τ ≤ 3. This critical phenomenon, however, can be obscured by the finiteness in space of the nuclei and in time of the reaction. With this in mind, this work studies the possibility of having critical phenomena in small "static" systems (using percolation of cubic and spherical grids), and on small "dynamic" systems (using molecular dynamics simulations of nuclear collisions in two and three dimensions). This is done investigating the mass distributions produced by these models and extracting values of critical exponents. The specific conclusion is that the obtained values of τ are within the range expected for critical phenomena, i.e. around 2.3, and the grander conclusion is that phase changes and critical phenomena appear to be possible in small and fast breaking systems, such as in collisions between heavy ions.

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