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

The 'hidden hypothesis'- approach in evaluation methodology: The Swiss participation in the European INTERREG II- Programme

Regional development, and crossborder cooperation in particular, needs feedbacks on the impacts of public policies. Policy evaluation is one appropriate tool. The ?hidden hypothesis'- approach is characterized by two elements: (1) an emphasis on the invisible goals of an evaluated programme or instrument and (2) a strong orientation towards processes of learning and motivation with the actors involved. (1) The formulation of political programmes tends to integrate as much different interests as possible. Such goal-setting processes simplify political agreement. But to evaluate such programmes with all their different and partly conflicting goals creates problems. The quality of an evaluation cannot be better as the quality of the evaluated goals and conflicting goals lead straight forward to conflicting results. (2) Evaluating the results of a political programme is also confronted with problems of measurement. Evaluation methodology normally distinguishes output, impact and outcome of a programme or a project. In general it is very tricky to evaluate the outcome. Thus the presented approach of evaluation works with different logic. The approach aims at enabling the actors concerned to modify and rearrange their activities. The evaluator acts as moderator and gives inputs for the necessary learning processes. This approach can be used especially in intermediate evaluations and monitoring. The case of the Swiss participation to the European INTERREG II- Programme shows a great complexity concerning political goals and concerning the cooperation in a federalistic political structure. Therefore the casestudy is a good example to demonstrate the advantages of the approach: In 1992 the Swiss population voted against joining the European Economic Market Treaty. The narrow rejection by plebiscite lead to intense discussions about the national cohesion. Afterwards the federal strategy to move the country towards an European integration has been based on a piecemeal approach and small projects of crossborder micro-integration. As an important strategic policy instrument the Swiss government decided to contribute to the INTERREG II- Programme of crossborder cooperation with own ressources of co-financing. In this situation the system of goals connected with the participation in INTERREG II is very complex: The different explicite and implicite goals can be categorized by a double dichotomy: On the one hand the tension between the goal of European integration and the goal of (Swiss) regional development. On the other hand the tension between active policy steering and re-active coordinating. Both relationsships are overlapping and influence the administrative levels between central government and the single local project. To evaluate this policy is a work of great complexity. Key words: evaluation methodology, regional crossborder development, INTERREG, Switzerland

Relativization strategies in Earlier African American Vernacular English

This article, which examines the system of relative markers in Early African American English as documented in the Ex-Slave Recordings (Bailey et al., 1991), is intended as a contribution to two areas of research: African American Vernacular English and the system of relativization in English. We found a significantly higher incidence of zero marking in adverbial relatives than in non-adverbial relatives. Among non-adverbial relatives, a variable rule analysis showed that non-humanness of the head as well as the function of the head as subject complement or subject in an existential sentence strongly favored zero relatives, and that prepositional complement heads disfavored zeroes. The lack of wh-relatives aswell as the frequency of zero subject relatives is interpreted as evidence that African American Vernacular English is a dialect of Englis

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

Basse vallée du Lot

La campagne 2013 a permis la poursuite des prospections inventaires en basse Vallée du Lot, sur les communes de Puy-l'Évêque, Touzac, Vire-sur-Lot, Saint-Vincent-Rive-d’Olt, mais plus particulièrement sur le secteur de Prayssac. Ainsi à Prayssac, le site de La Borie Rouge/Camp del Saltré (référencé 46PR-2-4A) fait partie d'un ensemble d'occupations plus vaste qui occupe la rive gauche du Niaudon et qui ont fourni sur plusieurs zones éparses, des matériels diversifiés pouvant être attribués au..

Basse vallée du Lot

Dans le cadre de la poursuite des investigations en Basse Vallée du Lot et plus particulièrement sur la commune de Prayssac, les champs de prospections inventaires ont été élargis à de nouvelles zones qui pour certaines se sont révélées positives. Commune de Prayssac : le site du Trioulou (référencé : de 46PR-4-1 à 46PR-4-8) Ce site s’étend sur environ 165 000 m2 le long d’un léger coteau versant au dessus du lit d’un ancien ruisseau. Plusieurs zones d’occupation éparses ont fourni des matéri..

Front localization in a ballistic annihilation model

We study the possibility of localization of the front present in a one-dimensional ballistically-controlled annihilation model in which the two annihilating species are initially spatially separated. We construct two different classes of initial conditions, for which the front remains localized.Comment: Using elsart (Elsevier Latex macro) and epsf. 12 Pages, 2 epsf figures. Submitted to Physica