Mesure de la perception de la qualité audiovisuelle par analyse conjointe de signaux physiologiques

National audienceL'influence de la qualité audiovisuelle (AV) sur l'utilisateur a été étudiée à partir de l'analyse de mesures physiologiques complétant les mesures subjectives habituellement utilisées. Le présent papier propose une méthode d'analyse de ces signaux basée sur l'extraction d'indicateurs et la définition d'un modèle empirique de détection automatique (par fusion de données hétérogènes) des modifications éventuelles de l'activité physiologique en réaction à la présence de dégradations de qualité et plus globalement, à la présentation de stimuli AV. Abstract - The influence of the video quality (AV) assessment was studied upon the basis of physiological measurements in addition to subjectives measurements usually used. In this paper, we propose new indicators extracted from these signals and an empirical method (with heterogenous data fusion) for automatic detection of physiological reaction due to quality degradation or more generally in response of stimuli

Binaural sound rendering improves immersion in a daily usage of a smartphone video game

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Une mesure d'expertise pour le crowdsourcing

International audienceCrowdsourcing, a major economic issue, is the fact that the firm outsources internal task to the crowd. It is a form of digital subcontracting for the general public.The evaluation of the participants work quality is a major issue in crowdsourcing. Indeed, contributions must be controlled to ensure the effectiveness and relevance of the campaign. We are particularly interested in small, fast and not automatable tasks. Several methods have been proposed to solve this problem, but they are applicable when the "golden truth" is not always known. This work has the particularity to propose a method for calculating the degree of expertise in the presence of gold data in crowdsourcing. This method is based on the belief function theory and proposes a structuring of data using graphs. The proposed approach will be assessed and applied to the data.Le crowdsourcing, un enjeu économique majeur, est le fait d'exter-naliser une tâche interne d'une entreprise vers le grand-public, la foule. C'est ainsi une forme de sous-traitance digitale destinée à toute personne susceptible de pouvoir réaliser la tâche demandée généralement rapide et non automatisable. L'évaluation de la qualité du travail des participants est cependant un problème majeur en crowdsourcing. En effet, les contributions doivent être contrôlées pour assurer l'efficacité et la pertinence d'une campagne. Plusieurs méthodes ont été proposées pour évaluer le niveau d'expertise des participants. Ce travail a la par-ticularité de proposer une méthode de calcul de degrés d'expertise en présence de données dont l'ordre de classement est connu. Les degrés d'expertise sont en-suite considérés sur des données sans ordre pré-établi. Cette méthode fondée sur la théorie des fonctions de croyance tient compte des incertitudes des réponses et est évaluée sur des données réelles d'une campagne réalisée en 2016

The reduction of 4-nitrobenzene diazonium electrografted layer: An electrochemical study coupled to in situ sum-frequency generation spectroscopy

This work describes an electrochemical study of 4-nitrobenzene diazonium (4-NBD) reduction onto glassy carbon (GC) electrode coupled to in situ sum-frequency generation (SFG) spectroscopy. After 4-NBD grafting at 0.3 V vs. saturated calomel electrode (SCE) onto GC, SFG allowed a clear signal assigned to the symmetrical vibration mode of the nitro (NO2) groups to be observed at 1349 cm-1 or 1353 cm-1 depending on whether the spectrum was recorded in air or inside the solution. This result proved that 4-NBD grafting actually occurs at a potential as high as 0.3 V vs. SCE. The combination of SFG data and cyclic voltammetry (CV) also indicated that at such a potential, NO2 groups did not experience reduction process into hydroxylamine (NHOH) or amine (NH2) groups. The electrolysis of grafted NO2 moieties at -0.1 V was followed by CV and in situ by SFG. The exponential decay of the NO2 signal located at 1353 cm-1 vs. electrolysis time was in accordance with a charge transfer-limited reaction rate for a species immobilized at the electrode surface, and allowed a first order kinetic rate constant for NO2 reduction to be estimated k = 0.006 s-1. The integration of the peaks observed on the corresponding cyclic voltammograms (CVs) which were attributed to the NO/NHOH reversible system showed that the NO2 reduction produced both hydroxylamine and amine groups and was not quantitative. The fact that SFG spectroscopy was silent for long electrolysis time values suggested the remaining nitro groups to be located far from the electrode surface, as a consequence of an electron tunneling efficiency which decreased throughout the film thickness. Further electrolysis at -0.8 V allowed the remaining nitro groups to be reduced into NH2 with almost quantitative yields. All these results suggest the existence of a stratified layer during the electrolysis process, in which there is no limitation due to H+ diffusion in the organic film

Measuring the Expertise of Workers for Crowdsourcing Applications

International audienceCrowdsourcing platforms enable companies to propose tasks to a large crowd of users. The workers receive a compensation for their work according to the serious of the tasks they managed to accomplish. The evaluation of the quality of responses obtained from the crowd remains one of the most important problems in this context. Several methods have been proposed to estimate the expertise level of crowd workers. We propose an innovative measure of expertise assuming that we possess a dataset with an objective comparison of the items concerned. Our method is based on the definition of four factors with the theory of belief functions. We compare our method to the Fagin distance on a dataset from a real experiment, where users have to assess the quality of some audio recordings. Then, we propose to fuse both the Fagin distance and our expertise measure

Nanoscale Stiffness Distribution in Bone Metastasis

Nanomechanical heterogeneity is expected to have an effect on elasticity, injury and bone remodelling. In normal bone, we have two types of cells (osteoclasts and osteoblasts) working together to maintain existing bone. Bone cancers can produce factors that make the osteoclasts work harder. This means that more bone is destroyed than rebuilt, and leads to weakening of the affected bone. We report here the first demonstration of the nanoscale stiffness distribution in bone metastases before and after treatment of animals with the bisphosphonate Risedronate, a drug which is currently used for the treatment of bone metastases in patients with advanced cancers. The strategy used here is applicable to a wide class of biological tissues and may serve as a new reflection for biologically inspired scaffolds technologies

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Combination of physiological and subjective measures to assess quality of experience for audiovisual technologies

International audienceThe competitive context in which the number of new audiovisual services increases requires taking user preferences into account to maintain the best possible quality of experience. The aim of the experiment presented in this paper is to study how the standardized ITU subjective measures may be supplemented by physiological measurements. Subjective assessments (ITU-T P.920, P.911) and physiological measurements (BVP, temperature, skin conductance and eye tracking) are collected from 34 subjects viewing three different 2D audiovisual contents. For each content, three different quality conditions are considered: reference one and two audio and/or video degraded ones (temporal asynchrony or bitrates variations). The results didn’t show an impact of the quality variation on the physiological measures but an effect was observed, as expected, on subjective data. However, results do not permit to conclude a lack of degradations’ effect on measures of physiological

Impact of the Content on Subjective Evaluation of Audiovisual Quality: What dimensions influence our perception?

International audienceSeveral studies have shown a test material dependency on perceived quality. Consequently, methods for evaluating AV quality should take account of influence of content corpus (regarding influence of audio, video and relationship between audio and video) to avoid uncontrolled effects. In this paper, technical, semantic and hedonic dimensions (including different descriptors) were used to characterize a corpus of AV contents. Results have showed significant effects of modality, dynamic and interest descriptors on the viewer AV quality perception. It also seems that verbal sequences and diegesis interact with asynchrony perception. As a result, these descriptors should be considered when selecting test sequences