Modified k-mean clustering method of HMM states for initialization of Baum-Welch training algorithm

International audienceHidden Markov models are widely used for recognition algorithms (speech, writing, gesture, ...). In this paper, a classical set of models is considered: state space of hid- den variable is discrete and observation probabilities are modeled as Gaussian distributions. The models parame- ters are generally estimated with training sequences and the Baum-Welch algorithm, i.e. an expectation maxi- mization algorithm. However this kind of algorithm is well known to be sensitive to its initialization point. The problem of this initialization point choice is addressed in this paper: a model with a very large number of states which describe training sequences with accuracy is first constructed. The number of states is then reduced using a k-mean algorithm on the state. This algorithm is com- pared to other methods based on a k-mean algorithm on the data with numerical simulations

Separation of instantaneous mixtures of cyclostationary sources and application to digital communication signals

Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200

Développement et utilisation d’un outil de calcul des coûts indirects des accidents de travail basé sur une cartographie des processus

RÉSUMÉ Les maladies et accidents professionnels infligent un fardeau économique considérable aux systèmes de santé nationaux, aux travailleurs blessés et aux entreprises. Afin de favoriser la prise en charge des situations de travail à risque par les entreprises et de les convaincre d’investir en prévention, les problématiques de santé et sécurité au travail (SST), et notamment l’impact des blessures sur la productivité des milieux de travail, doivent être exprimées dans un langage monétaire. En réponse à ce besoin, de nombreux travaux portant sur l’évaluation du coût des accidents de travail ont été réalisés mais les intervenants en SST utilisent peu cette information. Cette lacune est probablement liée au fait que les chercheurs n’ont pas encore réussi à mettre en place un outil de calcul des coûts des accidents qui réponde aux contraintes de temps et de précision des preneurs de décisions œuvrant au sein des milieux de travail. Cette recherche a pour objectif principal le développement d’un outil de calcul des coûts indirects adapté à une utilisation par les intervenants en SST sur le terrain. Elle s’articule autour de quatre études distinctes : dans la première étude, la littérature scientifique est passée en revue afin d’identifier les limites qui freinent l’utilisation des modèles de calcul du coût indirect dans les entreprises et d’établir des bases et des critères à respecter pour le développement d’un outil de calcul des coûts indirects adapté à une utilisation sur le terrain. En utilisant ces bases et critères ainsi que des données récoltées dans 10 entreprises de tailles et secteurs d’activité variés, un modèle de calcul des coûts indirects utilisant une cartographie de la réponse organisationnelle à un accident de travail a été élaboré et est présenté dans la seconde étude. Dans une troisième étude, cet outil a été utilisé afin de caractériser l’impact de plusieurs variables sur le montant des coûts indirects des accidents de travail en vue de générer des connaissances nouvelles sur leur comportement. Dans la dernière étude, les coûts indirects ont été mis en relation avec les niveaux de risque tels qu’évalués par les méthodes d’analyse de l’exposition aux facteurs de risque de troubles musculo-squelettiques (TMS), et ce, afin que les intervenants en SST puissent bénéficier, au moment de l’évaluation du poste de travail, d’une double indication, à la fois sur les niveaux de risque auxquels sont exposés les travailleurs et sur les coûts reliés à cette exposition au risque. Cette thèse a permis la mise en place d’un outil de calcul des coûts indirects qui semble adapté à une utilisation par les intervenants en SST sur le terrain. La cartographie des processus permet d’identifier aisément la durée et la fréquence des actions prises par les intervenants lorsqu’un accident de travail survient, facilite l’étape de collecte des informations nécessaires au calcul du coût indirect et fournit à l’utilisateur un résultat précis et exploitable. Des connaissances nouvelles sur la structure et le comportement des coûts indirects ont été générées dans la troisième étude : la comparaison de huit scénarios d’événements montre que les coûts indirects varient selon la gravité et la durée de l’accident ; la mise en relation de plusieurs variables au moyen d’analyses statistiques permet de mettre au jour que les coûts indirects varient significativement selon la nature, le siège de la lésion ou l’âge du travailleur ; les régressions linéaires révèlent que le nombre de jours de travaux légers et la productivité du travailleur pendant cette période influencent significativement les coûts indirects. Enfin, les résultats de la quatrième étude indiquent qu’il n’y a pas de corrélation significative entre les niveaux de risque mesurés au moyen de méthodes d’analyse de l’exposition aux facteurs de risque de TMS et les coûts indirects. En définitive, cette étude propose un outil inédit de calcul des coûts indirects qui semble adapté à une utilisation sur le terrain et qui devrait favoriser l’utilisation de l’information essentielle que représente le montant du coût indirect des accidents lors de la prise de décision relative aux investissements en prévention. Les nouvelles connaissances sur le comportement des coûts indirects devraient alimenter de futures recherches afin d’améliorer les outils proposés aux intervenants en SST et de soutenir la prise en charge de la prévention des situations de travail à risque par les entreprises.----------ABSTRACT Occupational injuries and illnesses represent a considerable financial burden for national health organizations, for injured employees and for employers. To foster the support of safe working condition by companies and convince them to invest in prevention, Occupational Health and Safety (OHS) issues, including the impact of injuries on the business productivity, must be expressed in dollar figures. In response to this need, researchers have conducted many studies on the cost of workplace accidents but OHS stakeholders still rarely use this information. The lack of consideration of this key information is related to the fact that the scientific literature has failed to provide OHS stakeholders with a cost-calculation tool that is both sufficiently accurate and does not require a data-collection stage ill-suited to the time constraints of workplace decision-makers. This research’s main objective is to develop an indirect-cost calculation model adapted to field use by OHS stakeholders. Four separate studies were conducted. In the first study, the recent scientific literature is reviewed to identify factors that may limit the use of workplace indirect costs calculation models and to establish basis and criteria to follow for developing an indirect cost model suitable for the work environment. Using these basis and criteria and the data collected in 10 companies of various sizes in different industry sectors, an indirect cost calculation model using process mapping of the organizational response to a workplace accident has been developed and is presented in the second study. In the third one, the calculation model is used to qualify the impact of several variables on the indirect costs of workplace accidents to expand the body of knowledge on their characteristics. In the last study, indirect costs are related to risk levels as assessed by methods for analyzing exposure to risk factors associated with musculoskeletal disorders (MSD) so that OHS stakeholders can benefit, when evaluating workstations, from a dual indication about the risk levels faced by workers and the costs related to this exposure. This thesis has enabled the development of an indirect cost calculation model that seems suitable for field use by OHS stakeholders in the 10 companies in which it was established. Indeed, the process mapping allows easy identification of the duration and frequency of actions taken by stakeholders when a workplace accident occurs, facilitates the collection of the information needed to calculate indirect costs and yields a usable, precise result. New findings on the variables that influence indirect costs are presented in the third study: a comparison of eight event scenarios shows that indirect costs vary depending on the severity and duration of the accident. Statistical analyses indicate that indirect costs vary significantly depending on the type and site of the injury. Linear regressions reveal that the number of days of light work has a major influence on indirect costs. The fourth study results show no significant correlation between risk levels as assessed by methods for analyzing exposure to MSD risk factors and indirect costs. Ultimately, this research presents a new indirect cost calculation model well-adapted to field use that should promote the consideration of the indirect costs of accidents, which are crucial to prevention investment decisions. New findings on indirect costs and their characteristics should stimulate new research and foster the improvement of the tools currently available to OHS stakeholders to help prevent hazardous workplace situations in their companies

SDR4all: a Tool for Making Flexible Radio a Reality

International audienceIn this contribution, we describe the potential of SDR4all (Software Defined Radio for all) to solve the bottlenecks and reduce the innovation cycle related to the design and implementation of flexible radio algorithms. SDR4all is a programmable software tool with radio cards for wireless researchers, students and engineers. It enables to implement in software any wireless scheme between two laptops. Using an flexible orthogonal frequency division multiplexing (OFDM) based implementation example, we describe the tool and show the performance of the transmission on a real wireless channel at 2.4 Ghz ISM band

Heart Rate Estimation from Phonocardiogram Signals Using Non-negative Matrix Factorization

International audienceElectrocardiogram (ECG) is classically considered for heart rate (HR) estimation. However in certain conditions, its use may be difficult and alternative techniques, such as phonocardiograhpy (PCG), are investigated. For PCG signals, in most studies, the challenge is to detect and annotate the heart sounds S 1 and S 2 , which may become quasi-impossible in case of noise. In this paper, we present a novel approach of HR estimation from PCG signals based on non-negative matrix factorization (NMF), applied to the spectrogram of PCG, considered as a source-filter model. Compared to state of the art methods, specific considerations based on the signal properties have been included to ensure the reliability of the decomposition. HR estimations obtained from noise-free and noisy real PCG signals are evaluated by comparison to HR estimation from synchronous ECG

A Wearable Technology Revisited for Cardio-Respiratory Functional Exploration: Stroke Volume Estimation From Respiratory Inductive Plethysmography

International audienceThe objective of the present study is to extract new information from complex signals generated by Respiratory Inductive Plethysmography (RIP). This indirect cardio-respiratory (CR) measure is a well-known wearable solution. The authors applied time-scale analysis to estimate cardiac activity from thoracic volume variations, witnesses of CR interactions. Calibrated RIP signals gathered from 4 healthy volunteers in resting conditions are processed by Ensemble Empirical Mode Decomposition to extract cardiac volume signals and estimate stroke volumes. Averaged values of these stroke volumes (SVRIP) are compared with averaged values of stroke volumes determined simultaneously by electrical impedance cardiography (SVICG). There is a satisfactory correlation between SVRIP and SVICG (r=0.76, p<0.001) and the limits of agreement between the 2 types of measurements (±23%) satisfies the required criterion (±30%). The observed under-estimation (-58%) is argued. This validates the use of RIP for following stroke volume variations and suggests that one simple transducer can provide a quantitative exploration of both ventilatory and cardiac volumes

Sexual behaviour in Drosophila is irreversibly programmed during a critical period

AbstractSexual differentiation in Drosophila is controlled by a short cascade of regulatory genes, the expression pattern of which determines all aspects of maleness and femaleness, including complex behaviours displayed by males and females [1–3]. One sex-determining gene is transformer (tra), the activity of which is needed for female development. Flies with a female karyotype (XX) but which are mutant for tra develop and behave as males. In such flies, a female phenotype can be restored by a transgene that carries the female-specific cDNA of tra under the control of a heat-shock promoter. This transgene, called hs[trafem], also transforms XY animals into sterile females [4]. When we raised these XX and XY ‘females’ at 25°C, however, they displayed vigorous male courtship while at the same time, as a result of their female pheromone pattern, they were attractive to males. Intriguingly, their male courtship behaviour was indiscriminately directed towards both females and males. When we forced expression of tra by heat shock, applied during a limited period around puparium formation, male behaviour was abolished and replaced by female behaviour. We conclude that sexual behaviour is irreversibly programmed during a critical period as a result of the activity or inactivity of a single control gene

Modeling Quasi-Periodic Signals by a Non-Parametric Model: Application on Fetal ECG Extraction

International audience— Quasi-periodic signals can be modeled by their second order statistics as Gaussian process. This work presents a non-parametric method to model such signals. ECG, as a quasi-periodic signal, can also be modeled by such method which can help to extract the fetal ECG from the maternal ECG signal, using a single source abdominal channel. The prior information on the signal shape, and on the maternal and fetal RR interval, helps to better estimate the parameters while applying the Bayesian principles. The values of the pa-rameters of the method, among which the R-peak instants, are accurately estimated using the Metropolis-Hastings algorithm. This estimation provides very precise values for the R-peaks, so that they can be located even between the existing time samples

Sexual selection on song and cuticular hydrocarbons in two distinct populations of Drosophila montana

Sexual selection has the potential to contribute to population divergence and speciation. Most studies of sexual selection in Drosophila have concentrated on a single signaling modality, usually either courtship song or cuticular hydrocarbons (CHCs), which can act as contact pheromones. We have examined the relationship between both signal types and reproductive success using F1–3 offspring of wild- collected flies, raised in the lab. We used two populations of the Holarctic species Drosophila montana that represent different phylogeographic clades that have been separate for ca. 0.5 million years (MY), and differ to some extent in both traits. Here, we characterize the nature and identify the targets of sexual selection on song, CHCs, and both traits combined within the populations. Three measures of courtship outcome were used as fitness proxies. They were the probability of mating, mating latency, and the production of rejection song by females, and showed patterns of association with different traits that included both linear and quadratic selection. Courtship song predicted courtship outcome better than CHCs and the signal modalities acted in an additive rather than synergistic manner. Selection was generally consistent in direction and strength between the two populations and favored males that sang more vigorously. Sexual selection differed in the extent, strength, and nature on some of the traits between populations. However, the differences in the directionality of selection detected were not a good predictor of population differences. In addition, a character previously shown to be important for species recognition, interpulse interval, was found to be under sexual selection. Our results highlight the complexity of understanding the relationship between within-population sexual selection and population differences. Sexual selection alone cannot predict differences between populations.Publisher PDFPeer reviewe

Risk assessment for long and short range airborne transmission of SARS-CoV-2, indoors and outdoors

Preventive measures to reduce infection are needed to combat the COVID-19 pandemic and prepare for a possible endemic phase. Current prophylactic vaccines are highly effective to prevent disease but lose their ability to reduce viral transmission as viral evolution leads to increasing immune escape. Long term proactive public health policies must therefore complement vaccination with available nonpharmaceutical interventions (NPI) aiming to reduce the viral transmission risk in public spaces. Here, we revisit the quantitative assessment of airborne transmission risk, considering asymptotic limits that considerably simplify its expression. We show that the aerosol transmission risk is the product of three factors: a biological factor that depends on the viral strain, a hydrodynamical factor defined as the ratio of concentration in viral particles between inhaled and exhaled air, and a face mask filtering factor. The short range contribution to the risk, both present indoors and outdoors, is related to the turbulent dispersion of exhaled aerosols by air drafts and by convection (indoor), or by the wind (outdoors). We show experimentally that airborne droplets and CO$_2$ molecules present the same dispersion. As a consequence, the dilution factor, and therefore the risk, can be measured quantitatively using the CO$_2$ concentration, regardless of the room volume, the flow rate of fresh air and the occupancy. We show that the dispersion cone leads to a concentration in viral particles, and therefore a short range transmission risk, inversely proportional to the squared distance to an infected person and to the flow velocity. The aerosolization criterion derived as an intermediate result, which compares the Stokes relaxation time to the Lagrangian time scale, may find application for a broad class of aerosol-borne pathogens and pollutants.Comment: 12 pages, 4 figures; updated manuscrip