Rotating 5D-Kaluza-Klein Space-Times from Invariant Transformations

Using invariant transformations of the five-dimensional Kaluza-Klein (KK) field equations, we find a series of formulae to derive axial symmetric stationary exact solutions of the KK theory starting from static ones. The procedure presented in this work allows to derive new exact solutions up to very simple integrations. Among other results, we find exact rotating solutions containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar and to gravitational multipole fields.Comment: 24 pages, latex, no figures. To appear in Gen. Rel. Grav., 32, (2000), in pres

Scalar Field (Wave) Dark Matter

Recent high-quality observations of dwarf and low surface brightness (LSB) galaxies have shown that their dark matter (DM) halos prefer flat central density profiles. On the other hand the standard cold dark matter model simulations predict a more cuspy behavior. Feedback from star formation has been widely used to reconcile simulations with observations, this might be successful in field dwarf galaxies but its success in low mass galaxies remains uncertain. One model that have received much attention is the scalar field dark matter model. Here the dark matter is a self-interacting ultra light scalar field that forms a cosmological Bose-Einstein condensate, a mass of $10^{-22}$eV/c$^2$ is consistent with flat density profiles in the centers of dwarf spheroidal galaxies, reduces the abundance of small halos, might account for the rotation curves even to large radii in spiral galaxies and has an early galaxy formation. The next generation of telescopes will provide better constraints to the model that will help to distinguish this particular alternative to the standard model of cosmology shedding light into the nature of the mysterious dark matter.Comment: 6 pages, to appear in: Proceedings of the Fourteenth Marcel Grossman Meeting on General Relativit

Nonlinear Analysis of Thin Fracture Specimens Using Solid, Isoparametric Finite Elements

This report examines the performance of various "solid" finite elements for the analysis of thin shell structures often encountered in nonlinear fracture mechanics studies. Such models require solid elements in the crack front region to capture strong through-thickness effects; modeling of the entire test specimen-structural element with solid elements then proves convenient. Unfortunately, the standard 8-node "brick" element with full integration exhibits strong shear-locking under bending deformations and thus overly stiff behavior. Three alternative elements are examined here: the 8-node element with single-point integration, the 8-node element with enhanced (incompatible) modes and the 20-node (quadratic) element. Element performance is assessed through analyses of a thin M(T) fracture specimen loaded in remote tension. This specimen generates strong compressive (T- )stresses parallel to the crack growth direction which leads to out-of-plane bending in the crack front region (triggered by a small normal force). The displacements obtained with a refined mesh of thin shell elements provide the reference solution for evaluation of the solid element performance. The analyses include large-displacement effects, but linear material response for simplicity, and are performed with Abaqus 5.6 and Warp3D. The results show clearly that both the 8-node element with enhanced modes and the 20-node element with conventional reduced integration provide solutions of accuracy comparable to the thin shell element. Mixed 8 and 20-node element meshes for ductile fracture analyses with transition elements to maintain displacement compatibility are demonstrated to provide an accurate and efficient modeling strategy.NASA-AMES Research CenterNASA-Langley Research CenterContract Nos. NCC 2-5126 and NAG 2-112

Solutions in Self-Dual Gravity Constructed Via Chiral Equations

The chiral model for self-dual gravity given by Husain in the context of the chiral equations approach is discussed. A Lie algebra corresponding to a finite dimensional subgroup of the group of symplectic diffeomorphisms is found, and then use for expanding the Lie algebra valued connections associated with the chiral model. The self-dual metric can be explicitly given in terms of harmonic maps and in terms of a basis of this subalgebra.Comment: Plain Latex, 13 Pages, major revisions of style in the above proof, several Comments added. Version to appear in Physical Review

Analysis of process variables via CFD to evaluate the performance of a FCC riser

Feedstock conversion and yield products are studied through a 3D model simulating the main reactor of the fluid catalytic cracking (FCC) process. Computational fluid dynamic (CFD) is used with Eulerian-Eulerian approach to predict the fluid catalytic cracking behavior. The model considers 12 lumps with catalyst deactivation by coke and poisoning by alkaline nitrides and polycyclic aromatic adsorption to estimate the kinetic behavior which, starting from a given feedstock, produces several cracking products. Different feedstock compositions are considered. The model is compared with sampling data at industrial operation conditions. The simulation model is able to represent accurately the products behavior for the different operating conditions considered. All the conditions considered were solved using a solver ANSYS CFX 14.0. The different operation process variables and hydrodynamic effects of the industrial riser of a fluid catalytic cracking (FCC) are evaluated. Predictions from the model are shown and comparison with experimental conversion and yields products are presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process