Geometric morphology of cellular solids Geometric morphology of cellular solids

ABSTRACT We demonstrate how to derive morphological information from micrographs, i.e., grey-level images, of polymeric foams. The segmentation of the images is performed by applying a pulse-coupled neural network. This processing generates blobs of the foams walls/struts and voids, respectively. The contours of the blobs and their corresponding points form the input to a constrained Delaunay tessellation, which provides an unstructured grid of the material under consideration. The subsequently applied Chordal Axis Transform captures the intrinsic shape characteristics, and facilitates the identification and localization of key morphological features. While stochastic features of the polymeric foams struts/walls such as areas, aspect ratios, etc., already can be computed at this stage, the foams voids require further geometric processing. The voids are separated into single foam cells. This shape manipulation leads to a refinement of the initial blob contours, which then requires the repeated application of the constrained Delaunay tessellation and Chordal Axis Transform, respectively. Using minimum enclosing rectangles for each foam cell, finally the stochastic features of the foam voids are computed

What Invariant One-Particle Multiplicity Distributions And Two-Particle Correlations Are Telling Us About Relativistic Heavy-Ion Collisions

INTRODUCTION Many of you are vigorously searching for the quark-gluon plasma---a predicted new phase of nuclear matter where quarks roam almost freely throughout the medium instead of being confined to individual nucleons. 1,2 Such a plasma is believed to have existed in the first 10 ¯s of the universe during the big bang and could be produced in the laboratory during the little bang of a relativistic heavy-ion collision. When nuclei collide head-on at relativistic speeds, the nuclear matter is initially compressed and excited from normal nuclear density and zero temperature to some maximum values---during which pions, kaons, and other particles are produced---and then expands, with a decrease in density and temperature. The early stages of the process are often treated in terms of nuclear fluid dynamics, but at some late stage the expanding matter freezes out into a collection of noninteracting hadrons. To sample the density, temperature, co