Comparing Feature Detectors: A bias in the repeatability criteria, and how to correct it

Most computer vision application rely on algorithms finding local correspondences between different images. These algorithms detect and compare stable local invariant descriptors centered at scale-invariant keypoints. Because of the importance of the problem, new keypoint detectors and descriptors are constantly being proposed, each one claiming to perform better (or to be complementary) to the preceding ones. This raises the question of a fair comparison between very diverse methods. This evaluation has been mainly based on a repeatability criterion of the keypoints under a series of image perturbations (blur, illumination, noise, rotations, homotheties, homographies, etc). In this paper, we argue that the classic repeatability criterion is biased towards algorithms producing redundant overlapped detections. To compensate this bias, we propose a variant of the repeatability rate taking into account the descriptors overlap. We apply this variant to revisit the popular benchmark by Mikolajczyk et al., on classic and new feature detectors. Experimental evidence shows that the hierarchy of these feature detectors is severely disrupted by the amended comparator.Comment: Fixed typo in affiliation

Thermo-mechanical FE model with memory effect for 304L austenitic stainless steel presenting microstructure gradient

The main purpose of this study is to determine, via a three dimensions Finite Element analysis (FE), the stress and strain fields at the inner surface of a tubular specimen submitted to thermo-mechanical fatigue. To investigate the surface finish effect on fatigue behaviour at this inner surface, mechanical tests were carried out on real size tubular specimens under various thermal loadings. X ray measurements, Transmission Electron Microscopy observations and micro-hardness tests performed at and under the inner surface of the specimen before testing, revealed residual internal stresses and a large dislocation microstructure gradient in correlation with hardening gradients due to machining. A memory effect, bound to the pre-hardening gradient, was introduced into an elasto-visco-plastic model in order to determine the stress and strain fields at the inner surface. The temperature evolution on the inner surface of the tubular specimen was first computed via a thermo-elastic model and then used for our thermo-mechanical simulations. Identification of the thermo-mechanical model parameters was based on the experimental stabilized cyclic tension-compression tests performed at 20^{\circ}C and 300^{\circ}C. A good agreement was obtained between numerical stabilized traction-compression cycle curves (with and without pre-straining) and experimental ones. This 3 dimensional simulation gave access to the evolution of the axial and tangential internal stresses and local strains during the tests. Numerical results showed: a decreasing of the tangential stress and stabilization after 40 cycles, whereas the axial stress showed weaker decreasing with the number of cycles. The results also pointed out a ratcheting and a slightly non proportional loading at the inner surface. The computed mean stress and strain values of the stabilized cycle being far from the initial ones, they could be used to get the safety margins of standard design related to fatigue, as well as to get accurate loading conditions needed for the use of more advanced fatigue analysis and criteria

Context-aware Authorization in Highly Dynamic Environments

Highly dynamic computing environments, like ubiquitous and pervasive computing environments, require frequent adaptation of applications. Context is a key to adapt suiting user needs. On the other hand, standard access control trusts users once they have authenticated, despite the fact that they may reach unauthorized contexts. We analyse how taking into account dynamic information like context in the authorization subsystem can improve security, and how this new access control applies to interaction patterns, like messaging or eventing. We experiment and validate our approach using context as an authorization factor for eventing in Web service for device (like UPnP or DPWS), in smart home security

Aspects of Assembly and Cascaded Aspects of Assembly: Logical and Temporal Properties

Highly dynamic computing environments, like ubiquitous and pervasive computing environments, require frequent adaptation of applications. This has to be done in a timely fashion, and the adaptation process must be as fast as possible and mastered. Moreover the adaptation process has to ensure a consistent result when finished whereas adaptations to be implemented cannot be anticipated at design time. In this paper we present our mechanism for self-adaptation based on the aspect oriented programming paradigm called Aspect of Assembly (AAs). Using AAs: (1) the adaptations process is fast and its duration is mastered; (2) adaptations' entities are independent of each other thanks to the weaver logical merging mechanism; and (3) the high variability of the software infrastructure can be managed using a mono or multi-cycle weaving approach.Comment: 14 pages, published in International Journal of Computer Science, Volume 8, issue 4, Jul 2011, ISSN 1694-081

Probe size study of apatite irradiation in stem

The effect of electron beam irradiation of stoichiometric hydroxyapatite (Ca10(PO4)6(OH)2, HAP) is investigated using electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) mode equipped with a LaB6 gun. Initial irradiation at 160 A cm −2 dose rate shows no modification of the low loss spectra. No difference of mass loss for Ca, O and P is observed for two different probe diameters: 4 nm (dose rate = 160 A cm −2) and 24 nm (dose rate = 70 A cm −2). Furthermore no formation of CaO is observed for both experimental conditions. It is proposed that the low values of both electron dose rates and doses (from 350 to 2400 C cm −2) avoid mass loss. At the higher dose rate obtained with a field emission gun (FEG), transformations are observed for the lowloss signal as well as for the Ca, P and O signals. These results might be very useful for the future studies of apatite particles at the nanoscale

Context-sensitive authorization for asynchronous communications

Main requirement of recent computing environments, like mobile and then ubiquitous computing, is to adapt applications to context. On the other hand, access control generally trust users once they have authenticated, despite the fact that they may reach unauthorized situations. We analyse how dynamic information can be used to improve security in the authorization process, especially in the case of asynchronous communications, like messaging or eventing. We experiment and validate our approach using context as an authorization factor for eventing in Web service for device (like UPnP or DPWS)

Le contrôle de l’érosion des sols forestiers par la végétation face aux changements globaux

L’érosion constitue un risque pour la fertilité du sol, mais les forestiers sont habituellement attentifs à la prévenir par des pratiques de gestion adaptées. La politique de restauration des terrains en montagne (RTM) a fait ses preuves durant les deux derniers siècles. Grâce à l’expérience acquise ainsi par les anciens et à la poursuite des recherches jusqu’à nos jours, les forestiers disposent d’une panoplie relativement complète de méthodes et d’espèces adaptées à la lutte contre l’érosion des sols sous toutes ses formes. Des guides techniques mettent ces connaissances à disposition de tous. Mais de nouveaux éléments liés aux changements globaux, notamment le changement climatique, le changement de pratiques et la demande énergétique, accroissent ou modifient le risque érosif et nécessitent de nouvelles approches qui sont détaillées dans cet article. Nous concluons qu’il est nécessaire d’adapter les savoirs traditionnels dans les régions où le risque érosif est ancien, et d’anticiper son accroissement dans les régions où il était habituellement faible

Toward a Behavioral Decomposition for Context-awareness and Continuity of Services

International audienceMany adaptative context-aware middleware exist and most of them rely on so-called vertical architectures that offer a functional decomposition for contextawareness. This architecture has a weak point: it does not allow the system handling both dynamics of the changing environment and applications. To avoid this, we propose an approach for context-awareness based on a behavioral decomposition, and because each behavior must complete all functionalities necessary for contextawareness, we introduce an hybrid decomposition. It consists in a functional decomposition into a behavioral decomposition. This approach derives benefits from both decomposition, first allowing to handle environment and application's dynamics, second introducing reusability and modularity into behaviors