Logic against Ghosts: Comparison of Two Proof Approaches for a List Module

International audienceModern verification projects continue to offer new challenges for formal verification. One of them is the linked list module of Contiki, a popular open-source operating system for the Internet of Things. It has a rich API and uses a particular list representation that make it different from the classical linked list implementations. Being widely used in the OS, the list module is critical for reliability and security. A recent work verified the list module using ghost arrays. This article reports on a new verification effort for this module. Realized in the Frama-C/Wp tool, the new approach relies on logic lists. A logic list provides a convenient high-level view of the linked list. The specifications of all functions are now proved faster and almost all automatically, only a small number of auxiliary lemmas and a couple of assertions being proved interactively in Coq. The proposed specifications are validated by proving a few client functions manipulating lists. During the verification, a more efficient implementation for one function was found and verified. We compare the new approach with the previous effort based on ghost arrays, and discuss the benefits and drawbacks of both techniques

La médiation christologique chez Hans Urs van Balthasar. Eléments pour une théologie de la chair.

status: publishe

Experimental investigation of the seabed roughness effect on the hydrodynamical behavior of a submarine cable under current and wave conditions.

Submarine cable behaviour is experimentally studied in the frame of the France Energies Marines project STHYF. In order to evaluate on-bottom stability of cables placed on rocky seabed with high roughness and submitted to combined wave and strong current, hydrodynamic loads are measured on a fixed slender cylinder closely fixed to a horizontal plate, with or without large roughness. A specified set of load cases (forced oscillations, current, forced oscillation + current) is considered to assess the hydrodynamic loads acting on the cylinder placed near a wall for varying gap-to-diameter ratios. The roughness effects on cylinder loads and on the flow are studied in detail. The result show a significant difference between rough and smooth bottom configurations. Indeed, the loads measurements and hydrodynamic coefficients are significantly lower with the presence of a rough plate near the cylinder. Especially for drag and oscillatory drag coefficients, however the inertia coefficient presents less differences between the different studied gaps.Le comportement des câbles sous-marins est étudié expérimentalement dans le cadre du projet France Energies Marines STHYF. Dans le but d’évaluer la stabilité des câbles lorsqu’ils sont placés sur des fonds avec de grandes rugosités et soumis à de fortes conditions de vagues et de courants, les efforts hydrodynamiques qui se produisent sur un cylindre fixe placé à proximité d’une plaque sur laquelle est positionné ou non des éléments de rugosités ont été mesurés. Des sollicitations spécifiques (courant, oscillations forcées et oscillations + courant) sont imposées afin de quantifier les efforts hydrodynamiques exercés sur le cylindre placé à différents distances de la plaque (avec ou sans rugosité). Les effets de la rugosité sur les efforts appliqués au cylindre et sur l’écoulement sont étudiés et mettent en évidence des différences importantes entre la configuration fond rugueux et fond lisse. Les efforts hydrodynamiques qui s’appliquent sur le cylindre sont notamment plus faibles lorsque celui est proche d’un fond rugueux que d’un fond lisse. De plus les coefficients de traı̂née statique et oscillante sont largement plus faibles dans le cas rugueux que dans le cas lisse. Les coefficients d’inertie présentent moins de différences significatives entre les différents écartements étudiés

Ambacia, la gauloise : 100 objets racontent la ville antique d'Amboise: Catalogue de l'exposition présentée à Amboise (Indre-et-Loire), Musée Hôtel Morin et église Saint-Florentin du 17 juin au 17 septembre 2017

National audienc

Ambacia, la gauloise : 100 objets racontent la ville antique d'Amboise: Catalogue de l'exposition présentée à Amboise (Indre-et-Loire), Musée Hôtel Morin et église Saint-Florentin du 17 juin au 17 septembre 2017

National audienc

OC6 project Phase IV: Validation of numerical models for novel floating offshore wind support structures

This paper provides a summary of the work done within Phase IV of the Offshore Code Comparison Collaboration, Continued with Correlation and unCertainty (OC6) project, under International Energy Agency Wind Technology Collaboration Programme Task 30. This phase focused on validating the loading on and motion of a novel floating offshore wind system. Numerical models of a 3.6MW horizontal-axis wind turbine atop the TetraSpar floating support structure were compared using measurement data from a 1:43-Froude-scale test performed in the University of Maine's Alfond Wind-Wave (W2) Ocean Engineering Laboratory. Participants in the project ran a series of simulations, including system equilibrium, surge offsets, free-decay tests, wind-only conditions, wave-only conditions, and a combination of wind and wave conditions. Validation of the models was performed by comparing the aerodynamic loading, floating support structure motion, tower base loading, mooring line tensions, and keel line tensions. The results show a relatively good estimation of the aerodynamic loading and a reasonable estimation of the platform motion and tower base fore-aft bending moment. However, there is a significant dispersion in the dynamic loading for the upwind mooring line. Very good agreement was observed between most of the numerical models and the experiment for the keel line tensions