2D Bubble Research Articles

Particle normal stress distribution around a rising bubble in a fluidized bed

Abstract The classical hydrodynamic approach has been examined regarding the issue of particle pressure in fluidized beds. The particle-pressure distribution around an isolated Davidson's bubble is derived for the constant-voidage case. It is found that the bed expansion stress appears in the upper region and the bed compression in the lower half region around a bubble. The maximum particle pressure is ( 5 4 )ϱ p (1−ϵ mf )gR b for a 2D bubble and ( 3 2 )ϱ p (1−ϵ mf )gR b for a 3D bubble. The negative pressure region which exists right above a bubble has a maximum pressure of (−1)ϱp(1−ϵmfgRb for a 2D bubble and (−0.843)ϱp(1−emf)gRb for a 3D bubble. The theoretical prediction is successfully validated experimentally by a particle-pressure probe developed in the present work.

Volumetric Segmentation of Medical Images by Three-Dimensional Bubbles

The segmentation of structure from images is an inherently difficult problem in computer vision and a bottleneck to its widespread application, e.g., in medical imaging. This paper presents an approach for integrating local evidence such as regional homogeneity and edge response to form global structure for figure–ground segmentation. This approach is motivated by a shock-based morphogenetic language, where the growth of four types of shocks results in a complete description of shape. Specifically, objects are randomly hypothesized in the form of fourth-order shocks (seeds) which then grow, merge, split, shrink, and, in general, deform under physically motivated “forces,” but slow down and come to a halt near differential structures. Two major issues arise in the segmentation of 3D images using this approach. First, it is shown that the segmentation of 3D images by 3D bubbles is superior to a slice-by-slice segmentation by 2D bubbles or by “212D bubbles” which are inherently 2D but use 3D information for their deformation. Specifically, the advantages lie in an intrinsic treatment of the underlying geometry and accuracy of reconstruction. Second, gaps and weak edges, which frequently present a significant problem for 2D and 3D segmentation, are regularized by curvature-dependent curve and surface deformations which constitute diffusion processes. The 3D bubbles evolving in the 3D reaction–diffusion space are a powerful tool in the segmentation of medical and other images, as illustrated for several realistic examples.