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On the Half-Space Matching Method for Real Wavenumber
No full textInternational audienceThe Half-Space Matching (HSM) method has recently been developed as a new method for the solution of 2D scattering problems with complex backgrounds, providing an alternative to Perfectly Matched Layers (PML) or other artificial boundary conditions. Based on half-plane representations for the solution, the scattering problem is rewritten as a system coupling (1) a standard finite element discretisation localised around the scatterer and (2) integral equations whose unknowns are traces of the solution on the boundaries of a finite number of overlapping half-planes contained in the domain. While satisfactory numerical results have been obtained for real wavenumbers, well-posedness and equivalence of this HSM formulation to the original scattering problem have been established only for complex wavenumbers. In the present paper we show, in the case of a homogeneous background, that the HSM formulation is equivalent to the original scattering problem also for real wavenumbers, and so is well-posed, provided the traces satisfy radiation conditions at infinity analogous to the standard Sommerfeld radiation condition. As a key component of our argument we show that, if the trace on the boundary of a half-plane satisfies our new radiation condition, then the corresponding solution to the half-plane Dirichlet problem satisfies the Sommerfeld radiation condition in a slightly smaller half-plane. We expect that this last result will be of independent interest, in particular in studies of rough surface scattering
Acoustic passive cloaking using thin outer resonators
No full textInternational audienceWe consider the propagation of acoustic waves in a 2D waveguide unbounded in one direction and containing a compact obstacle. The wavenumber is fixed so that only one mode can propagate. The goal of this work is to propose a method to cloak the obstacle. More precisely, we add to the geometry thin outer resonators of width ε and we explain how to choose their positions as well as their lengths to get a transmission coefficient approximately equal to one as if there were no obstacle. In the process we also investigate several related problems. In particular, we explain how to get zero transmission and how to design phase shifters. The approach is based on asymptotic analysis in presence of thin resonators. An essential point is that we work around resonance lengths of the resonators. This allows us to obtain effects of order one with geometrical perturbations of width ε. Various numerical experiments illustrate the theory
From OCL-based model static analysis to quick fixes
No full textInternational audienceGiving accurate and relevant static analysis feedback to modeling tool users significantly helps them design useful models. This feedback is even more valuable when it comes with completion proposals, called quick fixes, which users can apply to automatically resolve specific issues. However, implementing such static analysis and quick fix tooling is tedious and error prone. For instance, providing accurate messages typically requires decomposing complex model queries into simpler ones, while suitably handling their dependencies. Moreover, each quick fix should actually resolve the issue it is supposed to fix, which is not always easy to ensure. This paper presents an approach that leverages reverse propagation of OCL-like boolean expressions to provide correct-by-construction quick fixes. It only requires adding specific annotations to expressions in order to guide quick fix computation. A proof-of-concept implementation of this approach on the AnimUML partial modeling tool is described. It is able to automatically construct messages, to report different messages depending on which part of a predicate fails, and to provide quick fixes
A Fuzzy Set Estimation Using Interval Contractors: Application to Localization
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A fast hybrid approach to model roughness effects for the 2D tropospheric maritime long-range propagation
No full textInternational audienceThis paper studies the long-range tropospheric electromagnetic wave propagation over the sea. An asymptotic model based on the parabolic wave equation is considered. This latter is solved using a fast and memory-efficient wavelet-based method. The roughness effects of the sea are introduced through a hybrid approach. Numerical experiments (in X-band) are provided to highlight the advantages of the wavelet-based method in the context of maritime propagation
TousEnsemble, un site internet interactif pour les parties prenantes de l'inclusion scolaire de jeunes avec TSA : une conception itérative incluant des tests utilisateurs
No full textSchool inclusion of children with Autism Spectrum Disorder (ASD) represents a challenge forall parties involved (family, school and out-of-school actors such as medico-socialprofessionals). To the best of our knowledge, existing tools focus either on the pupil, or therelationships between two parties, always including parents. Considering a systemic approachand knowing that collaboration among stakeholders of school inclusion allows the latter tosucceed, we decided to create a tool to enhance and facilitate communication and informationsharing among them. For a better usability and to ensure satisfaction of the need expressed bythose stakeholders, we used participatory design to create the web-based app ToGather. Weused (fictitious) realistic cases to create scenarios that contain tasks to do on the webapplication, adapted to each participant role (parent, teacher and external actors). We usedobjective (interaction annotations, website navigation inspection) and subjective(questionnaires) measures to assess the design of ToGather, with regards to usability, userexperience, cognitive load and elicited self-determination. Results indicated that ToGather wasvery usable, with an excellent user experience, and a relatively low cognitive demand. Somedesign mistakes have been identified and corrected for the enhanced final release
Conception centrée-utilisateur de l'application web TousEnsemble : un outil de soutien à la collaboration famille-professionnels et interprofessionnelle pour la scolarisation des collégiens avec TSA
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Selecting Better Samples from Pre-trained LLMs: A Case Study on Question Generation
No full textLarge Language Models (LLMs) have in recent years demonstrated impressive prowess in natural language generation. A common practice to improve generation diversity is to sample multiple outputs from the model. However, there lacks a simple and robust way of selecting the best output from these stochastic samples. As a case study framed in the context of question generation, we propose two prompt-based approaches to selecting high-quality questions from a set of LLM-generated candidates. Our method works under the constraints of 1) a black-box (non-modifiable) question generation model and 2) lack of access to human-annotated references -- both of which are realistic limitations for real-world deployment of LLMs. With automatic as well as human evaluations, we empirically demonstrate that our approach can effectively select questions of higher qualities than greedy generation
Intrinsically Motivated Goal Exploration Processes with Automatic Curriculum Learning
No full textPublished at JMLR 2022International audienceIntrinsically motivated spontaneous exploration is a key enabler of autonomous developmental learning in human children. It enables the discovery of skill repertoires through autotelic learning, i.e. the self-generation, self-selection, self-ordering and self-experimentation of learning goals. We present an algorithmic approach called Intrinsically Motivated Goal Exploration Processes (IMGEP) to enable similar properties of autonomous learning in machines. The IMGEP architecture relies on several principles: 1) self-generation of goals, generalized as parameterized fitness functions; 2) selection of goals based on intrinsic rewards; 3) exploration with incremental goal-parameterized policy search and exploitation with a batch learning algorithm; 4) systematic reuse of information acquired when targeting a goal for improving towards other goals. We present a particularly efficient form of IMGEP, called AMB, that uses a population-based policy and an object-centered spatio-temporal modularity. We provide several implementations of this architecture and demonstrate their ability to automatically generate a learning curriculum within several experimental setups. One of these experiments includes a real humanoid robot exploring multiple spaces of goals with several hundred continuous dimensions and with distractors. While no particular target goal is provided to these autotelic agents, this curriculum allows the discovery of diverse skills that act as stepping stones for learning more complex skills, e.g. nested tool use