Hyperboliity versus partial-hyperbolicity and the transversality-torsion phenomenon

In this paper, we describe a process to create hyperbolicity in the neighbourhood of a homoclinic orbit to a partially hyperbolic torus for three degrres of freedom Hamiltonian systems: the transversality-torsion phenomenon.Comment: 10 page

A predictive approach for a real-time remote visualization of large meshes

Déjà sur HALRemote access to large meshes is the subject of studies since several years. We propose in this paper a contribution to the problem of remote mesh viewing. We work on triangular meshes. After a study of existing methods of remote viewing, we propose a visualization approach based on a client-server architecture, in which almost all operations are performed on the server. Our approach includes three main steps: a first step of partitioning the original mesh, generating several fragments of the original mesh that can be supported by the supposed smaller Transfer Control Protocol (TCP) window size of the network, a second step called pre-simplification of the mesh partitioned, generating simplified models of fragments at different levels of detail, which aims to accelerate the visualization process when a client(that we also call remote user) requests a visualization of a specific area of interest, the final step involves the actual visualization of an area which interest the client, the latter having the possibility to visualize more accurately the area of interest, and less accurately the areas out of context. In this step, the reconstruction of the object taking into account the connectivity of fragments before simplifying a fragment is necessary.Pestiv-3D projec

Motion sickness evaluation and comparison for a static driving simulator and a dynamic driving simulator

This paper deals with driving simulation and in particular with the important issue of motion sickness. The paper proposes a methodology to evaluate the objective illness rating metrics deduced from the motion sickness dose value and questionnaires for both a static simulator and a dynamic simulator. Accelerations of the vestibular cues (head movements) of the subjects were recorded with and without motion platform activation. In order to compare user experiences in both cases, the head-dynamics-related illness ratings were computed from the obtained accelerations and the motion sickness dose values. For the subjective analysis, the principal component analysis method was used to determine the conflict between the subjective assessment in the static condition and that in the dynamic condition. The principal component analysis method used for the subjective evaluation showed a consistent difference between the answers given in the sickness questionnaire for the static platform case from those for the dynamic platform case. The two-tailed Mann–Whitney U test shows the significance in the differences between the self-reports to the individual questions. According to the two-tailed Mann–Whitney U test, experiencing nausea (p = 0.019 < 0.05) and dizziness (p = 0.018 < 0.05) decreased significantly from the static case to the dynamic case. Also, eye strain (p = 0.047 < 0.05) and tiredness (p = 0.047 < 0.05) were reduced significantly from the static case to the dynamic case. For the perception fidelity analysis, the Pearson correlation with a confidence interval of 95% was used to study the correlations of each question with the x illness rating component IRx, the y illness rating component IRy, the z illness rating component IRz and the compound illness rating IRtot. The results showed that the longitudinal head dynamics were the main element that induced discomfort for the static platform, whereas vertical head movements were the main factor to provoke discomfort for the dynamic platform case. Also, for the dynamic platform, lateral vestibular-level dynamics were the major element which caused a feeling of fear

Prediction of cybersickness in virtual environments using topological data analysis and machine learning

Recent significant progress in Virtual Reality (VR) applications and environments raised several challenges. They proved to have side effects on specific users, thus reducing the usability of the VR technology in some critical domains, such as flight and car simulators. One of the common side effects is cybersickness. Some significant commonly reported symptoms are nausea, oculomotor discomfort, and disorientation. To mitigate these symptoms and consequently improve the usability of VR systems, it is necessary to predict the incidence of cybersickness. This paper proposes a machine learning approach to VR’s cybersickness prediction based on physiological and subjective data. We investigated combinations of topological data analysis with a range of classifier algorithms and assessed classification performance. The highest performance of Topological Data Analysis (TDA) based methods was achieved in combination with SVMs with Gaussian RBF kernel, indicating that Gaussian RBF kernels provide embeddings of physiological time series data into spaces that are rich enough to capture the essential geometric features of this type of data. Comparing several combinations with feature descriptors for physiological time series, the performance of the TDA + SVM combination is in the top group, statistically being on par or outperforming more complex and less interpretable methods. Our results show that heart rate does not seem to correlate with cybersickness

Museum augmented interface for historical scale models: towards a new way for cultural heritage promotion

International audienceIn this paper, we describe an interactive museum application dedicated to historical scale models. This comes from a joint work between multidisciplinary teams: industrial engineering researchers, historians, museum curators and interactive interface designers. We present here theresult of the project, based on scientific methodology. Results include system architecture, hardware and software, some use cases and user evaluation figures. This paper also underlines some methodology issues that illustrate future possibilities

Tuning, Impedance Matching, and Temperature Regulation during High-Temperature Microwave Sintering of Ceramics

International audienceOver the years, microwave radiation has emerged as an efficient source of energy for material processing. This technology provides a rapid and a volumetric heating of material. However, the main issues that prevent microwave technology from being widespread in material processing are temperature control regulation and heating distribution within the sample. Most of the experimental works are usually manually monitored, and their reproducibility is rarely evaluated and discussed. In this work, an originally designed 915MHz microwave single-mode applicator for high-temperature processing is presented. The overall microwave system is described in terms of an equivalent electrical circuit. This circuit has allowed to point out the different parameters which need to be adjusted to get a fully controlled heating process. The basic principle of regulation is then depicted in terms of a block function diagram. From it, the process has been developed and tested to sinter zirconia-and spinel-based ceramics. It is clearly shown that the process can be successfully used to program multistep temperature cycles up to similar to 1550 degrees C, improving significantly the reproducibility and the ease of use of this emerging high-temperature process technology

A topological approach for human movement classification and anticipation

The motion capture systems are increasingly used for biomedical purposes. In order to recognize and classify the movements, however whole-body movements using passive markers, generate a huge amount of data. Can topological data analysis methods improve the recognition of movements? Can we use the results of this analysis combined with particular types of neural networks to anticipate the continuation of a movement

Nantes 1900 - la maquette du port: Une valorisation scientifique et musicographique innovante

National audienceLe plan-relief du port de Nantes, présenté à l’Exposition universelle de 1900 à Paris, intègre à la fin des années 1920 les collections des musées nantais : objet promotionnel pendant deux décennies au service de l’excellence des aménagements portuaires, il devient dès lors un objet patrimonial d’exception.Son insertion dans le parcours scénographique du musée d’histoire de Nantes amène rapidement les équipes de la conservation à porter un nouveau regard sur cette maquette, à la questionner et à imaginer une médiation pour « la faire parler ».Très vite, une collaboration entre l’Université, l’École Centrale de Nantes et le musée voit le jour afin de mettre en place un outil numérique issu de champs de recherches variés.Désormais, par ce dispositif innovant mis à la disposition du public, le plan-relief devient, au-delà d’un précieux indicateur de l’histoire de l’architecture industrielle et des paysages nantais du début du 20e siècle, un support dynamique à la compréhension du territoire actuel, au cœur de la réflexion sur le devenir de Nantes et de son rapport à la Loire

Blind Separation of Cyclostationary Sources Sharing Common Cyclic Frequencies Using Joint Diagonalization Algorithm

We propose a new method for blind source separation of cyclostationary sources, whose cyclic frequencies are unknown and may share one or more common cyclic frequencies. The suggested method exploits the cyclic correlation function of observation signals to compose a set of matrices which has a particular algebraic structure. The aforesaid matrices are automatically selected by proposing two new criteria. Then, they are jointly diagonalized so as to estimate the mixing matrix and retrieve the source signals as a consequence. The nonunitary joint diagonalization (NU-JD) is ensured by Broyden-Fletcher-Goldfarb-Shanno (BFGS) method which is the most commonly used update strategy for implementing a quasi-Newton technique. The efficiency of the method is illustrated by numerical simulations in digital communications context, which show good performances comparing to other stateof-the-art methods

Experimental and Finite Element Analysis of the Tensile Behavior of Architectured Cu-Al Composite Wires

The present study investigates, experimentally and numerically, the tensile behavior of copper-clad aluminum composite wires. Two fiber-matrix configurations, the conventional Alcore/ Cu-case and a so-called architectured wire with a continuous copper network across the crosssection, were considered. Two different fiber arrangements with 61 or 22 aluminum fibers were employed for the architectured samples. Experimentally, tensile tests on the two types of composites show that the flow stress of architectured configurations is markedly higher than that of the linear rule of mixtures’ prediction. Transverse stress components and processing-induced residual stresses are then studied via numerical simulations to assess their potential effect on this enhanced strength. A set of elastic-domain and elastoplastic simulations were performed to account for the influence of Young’s modulus and volume fraction of each phase on the magnitude of transverse stresses and how theses stresses contribute to the axial stress-strain behavior. Besides, residual stress fields of different magnitude with literature-based distributions expected for cold-drawn wires were defined. The findings suggest that the improved yield strength of architectured Cu-Al wires cannot be attributed to the weak transverse stresses developed during tensile testing, while there are compelling implications regarding the strengthening effect originating from the residual stress profile. Finally, the results are discussed and concluded with a focus on the role of architecture and residual stresses