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International audience; Graphical notations designed by committees in the context of standardization bodies, like Object Management Group (OMG), are widely used in the industry and academia. Naive users of these notations have limited background on visualization, documentation and specification of workflows, data or software systems. Several studies have pointed out the fact that these notations do not convey any particular semantics and their understanding is not perceptually immediate. As reported in these studies, this lack of semantic transparency increases the cog-nitive load to differentiate between concepts, slows down the learning and comprehension of the language constructs. This paper reports on a set of experiments that confirm the lack of semantic transparency of the Unified Modeling Language (UML) as designed by OMG and compares this standard to alternative solutions where naive users are involved in the design of the notations to speed-up the learning of these languages to new users.

International audience; We present in this paper a CHR based parsing methodology for parsing Property Grammars. This approach constitutes a flexible parsing technology in which the notions of derivation and hierarchy give way to the more flexible notion of constraint satisfaction between categories. It becomes then possible to describe the syntactic characteristics of a category in terms of satisfied and violated constraints.Different applications can take advantage of such flexibility, in particular in the case where information comes from part of the input and requires the identification of selected phrases such as NP, PP, etc. Our method presents two main advantages: first, there is no need to build an entire syntactic structure, only the selected phrases can be extracted. Moreover, such extraction can be done even from incomplete or erroneous text: indication of possible kinds of error or incompleteness can be given together with the proposed analysis for the phrases being sought.

International audience

International audience; We reexamine the modular clock algorithm for distributed blind rendezvous in cognitive radio networks. It proceeds in rounds. Each round consists of scanning twice a block of generated channels. The modular clock algorithm inspired the creation of the jump-stay rendezvous algorithm. It augments the modular clock with a stay-on-one-channel pattern. This enhancement guarantees rendezvous in one round. We make the observation that as the number of channels increases, the significance of the stay-on-one-channel pattern decreases. We revisit the performance analysis of the two-user symmetric case of the modular clock algorithm. We compare its performance with a random and the jump-stay rendezvous algorithms. Let m be the number of channels. Let p be the smallest prime number greater than m. The expected time-to-rendezvous of the random and jump-stay algorithms are m and p, respectively. Theis et al.'s analysis of the modular clock algorithm concludes a maximum expected time-to-rendezvous slightly larger than 2p time slots. Our analysis shows that the expected time-to-rendezvous of the modular clock algorithm is no more than 3p/4 time slots

International audience

We introduce a new basis of the non-commutative symmetric functions whose elements have Schur functions as their commutative images. Dually, we build a basis of the quasi-symmetric functions which expand positively in the fundamental quasi-symmetric functions and decompose Schur functions according to a signed combinatorial formula. Nous introduisons une nouvelle base des fonctions syméetriques non commutatives dont les images commutatives sont des fonctions de Schur. Nous construisons la base duale des fonctions quasi-symétriques qui s’expriment de façon positive en fonction de la base fondamentale et décomposent les fonctions de Schur.

International audience; The vibratory response of a periodically-forced generic mechanical system undergoing a unilateral contact condition is addressed. The unilateral contact constraint is reformulated as a nonsmooth Lipschitz continuous function. This allows the use of the so-called semismooth Newton method capable of solving the equations governing the dynamics and the unilateral contact constraints simultaneously. The assumed periodic solution and the contact force are approximated by truncated Fourier series before being incorporated in the solver after projection of the equations on the Fourier basis. Continuation of the solution harmonics with respect to the forcing frequency is performed. For a medium size system of 20 degrees-of-freedom, it is shown that convergence is achieved by comparing with the reference time-marching solution.

International audience; We present a geometric representation of a tetrahedral mesh that is solely based on dihedral angles. We first show that the shape of a tetrahedral mesh is completely defined by its dihedral angles. This proof leads to a set of angular constraints that must be satisfied for an immersion to exist in R 3. This formulation lets us easily specify conditions to avoid inverted tetrahedra and multiply-covered vertices, thus leading to locally injective maps. We then present a constrained optimization method that modifies input angles when they do not satisfy constraints. Additionally, we develop a fast spectral reconstruction method to robustly recover positions from dihedral angles. We demonstrate the applicability of our representation with examples of volume parameterization, shape interpolation, mesh optimization, connectivity shapes, and mesh compression.

In structural engineering, seismic vulnerability reduction of existing structures is a crucial issue. External reinforcement with fiber-reinforced polymer (FRP) holds interest in achieving this aim. Its use as a retrofitting method is limited, however, for a number of reasons, including the lack of numerical tools for predicting cyclic loading. This paper presents a simplified stress-strain model suitable for monotonic and cycling loading capable of predicting the FRP's effect on reinforced-concrete col umns. The model is inspired by two well-known concrete constitutive laws: one based on damage mechanics (La Borderie's concrete-damage model, 1991); the other on extensive experimental studies (Eid & Paultre's confined-concrete model, 2008). Validation is provided using experimental results on reinforced concrete columns subjected to axial and flexural cyclic loading. All the simulations were conducted with multifiber Timoshenko beam elements.

International audience; Ultraviolet-written Long Period Fibre Gratings are demonstrated to be affective tools when measuring thermal gradients of a thermally conductive material. More specifically, variations in the thermal system of a substrate are detected through transmission spectrum responses. While it is well known that uniform temperature leads to pure wavelength shifts of the transmission spectrum minimum, observed changes in transmission loss lead to predictions of thermal gradients. Since Fourier's law of heat conduction implies that heat flux measurements of known conductive materials can be predicted with knowledge of the temperature gradient, the present work demonstrates that optical fibres may be used to develop photonic heat flux sensors. Such an advancement would have a significant impact in industries, such as building materials, in which embedded sensors are used to predict surface thermal boundary layer conditions.