Microstructure, strain fields and flow stress in deformed metal matrix composites

An experimental study of local orientations around whiskers in deformed metal matrix composites has been used to determine the strain gradients existing in the material following tensile deformation. These strain fields have been represented as arrays of geometrically necessary dislocations, and the material flow stress predicted using a standard dislocation hardening model. Whilst the correlation between this and the measured flow stress is reasonable, the experimentally determined strain gradients are lower by a factor of 5-10 than values obtained in previous estimates made using continuum plasticity finite element models. The local orientations around the whiskers contain a large amount of detailed information about the strain patterns in the material, and a novel approach is made to representing some of this information and to correlating it with microstructural observations. © 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.

Vision-based global localization using a visual vocabular

This paper presents a novel coarse-to-fine global localization approach that is inspired by object recognition and text retrieval techniques. Harris-Laplace interest points characterized by SIFT descriptors are used as natural land-marks. These descriptors are indexed into two databases: an inverted index and a location database. The inverted index is built based on a visual vocabulary learned from the feature descriptors. In the location database, each location is directly represented by a set of scale invariant descriptors. The localization process consists of two stages: coarse localization and fine localization. Coarse localization from the inverted index is fast but not accurate enough; whereas localization from the location database using voting algorithm is relatively slow but more accurate. The combination of coarse and fine stages makes fast and reliable localization possible. In addition, if necessary, the localization result can be verified by epipolar geometry between the representative view in database and the view to be localized. Experimental results show that our approach is efficient and reliable. ©2005 IEEE.