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Controlling shapes is a challenging problem in a multi-phase fluid simulation. Bubble particles enable the details of air bubbles to be represented within a simulation based on an Euler grid. We control the target shapes of bubbles by the gradient vectors of the signed distance field and attraction forces associated with control particles. Our hybrid approach enables to simulate physically plausible movements of bubbles while preserving the details of a target shape. Furthermore, we control the paths of moving bubbles using user-defined curves and the shape of an air bubbles by drag force. An accurate model of the drag force near the fluid surface means that bubbles have realistic ellipsoidal shapes. [ABSTRACT FROM AUTHOR]

The article describes the crystal structure of a two-dimensional network in the molecular salt 2-methyllimidazolium hydrogen glutarate, and three-dimensional networks in the salts 2-methyl-imidazolium hydrogen succinate and 2-methyllimidazolium hydrogen adipate monohydrate. It shows the formation of the networks which are built from hydrogen bonded rings, with atom numbering and probability displacement ellipsoids. Also calculated are the values of the diacids and bases in an aqueous medium to identify the existence of 1:2 salt of an aliphatic diacid.

Finite element calculation is applied to assess elasticity parameters of random cellular structures with anisotropy. Cellular structure is generated using Random Sequential Addition algorithm. Anisotropy is considered by introducing elongation and orientation of ellipsoid voids. Structures are meshed using a regular mesh scheme. A uniaxial compression test is simulated under solid phase isotropy conditions. Effective Young's modulus and Poisson ratio are calculated and related to structural anisotropy parameters. Finite element results show a mesh-independence of elasticity parameters against scale and underline the large dependence of elasticity parameters to anisotropy and to the relative density of the cellular material: rigidity is increased in the anisotropy direction and mechanical instability in the other directions. Structures with large random population of ellipsoids contribute to lower such effect. [ABSTRACT FROM AUTHOR]

The distance of closest approach of particles with hard cores is a key parameter in statistical theories and computer simulations of liquid crystals and colloidal systems. In this paper, we provide a new algorithm to calculate the distance of closest approach of two ellipsoids of arbitrary shape and orientation. This algorithm is based on our previous analytic result for the distance of closest approach of 2D ellipses. The method consists of determining the intersection of the ellipsoids with the plane containing the line joining their centers and rotating the plane. The distance of closest approach of the two ellipses formed by the intersection is a periodic function of the plane orientation, whose maximum corresponds to the distance of closest approach of the two ellipsoids. [ABSTRACT FROM AUTHOR]

The ultimate state of granular material was investigated by the discrete element method. This paper discusses a series of numerical triaxial tests on samples of two kinds of ellipsoids. Samples of three different densities were loaded along various stress paths. The ellipsoids were mixed in the proportions 50:50 by weight. The longer particles have an aspect ratio (major length/minor length) of 1.5 and the other particles have an aspect ratio of 1.2. The samples were generated by deposition under gravity to simulate the air-pluviation sample preparation technique. Then they were consolidated isotropically. Fourteen stress-path controlled triaxial tests were conducted numerically for each sample. They are sheared to the ultimate state to determine the friction angle and void ratio at the ultimate state. When samples of different densities were sheared along the same loading path, a unique ultimate state was observed. The initial density does not affect the ultimate state. However, when different loading paths are applied to the same numerical specimen, they do not always arrive at the same critical state in the void-mean stress space. [ABSTRACT FROM AUTHOR]