Etude des mécanismes physiques et de leur influence sur la cinétique de méthanisation en voie sèche (essais expérimentaux et modélisation)

La méthanisation est un procédé biologique au cours duquel la matière organique est convertie en un gaz riche en méthane (biogaz). Parmi les technologies industrielles, les procédés de digestion par voie sèche (taux de matière sèche supérieur à 15 %) sont de plus en plus utilisés car ils présentent des avantages concurrentiels important par rapport aux procédés classiques par voie humide. Cependant, la nature très pâteuse du milieu de digestion lui confère des propriétés mal connues et non étudiées (comportement rhéologique, équilibres, transferts, cinétiques biologiques). Cette thèse comporte deux axes de recherche : i) la nature des équilibres chimiques (sorption, diffusion) intervenant dans les milieux de digestion, ii) la mise en place et l application d un modèle cinétique adapté à l étude des milieux secs. Sur le premier volet, nous avons mis en évidence que le transfert diffusionnel est fortement réduit avec l augmentation de la teneur en matière sèche des milieux en absence d agitation. Une des conséquences est l importance du transfert liquide-gaz pour la production de biogaz. Sur le deuxième volet, nous avons développé un modèle cinétique dédié qui nous a permis, par comparaison avec l expérience, de mieux cerner la variabilité de la cinétique en fonction de la teneur en matière sèche des milieux. Les répercussions de ce travail se situent aussi bien à l échelle du laboratoire, en particulier pour l exploitation des essais d activité méthanogène, qu à l échelle industrielle, avec la nécessité de contrôler le taux de matière sèche des procédés pour une efficacité optimale, et d adapter l agitation à ce taux pour améliorer les rendements de dégradation. Le modèle développé pourra constituer une base pour le dimensionnement et la conduite des installations.Anaerobic digestion is a biological process that converts organic matter into a methane rich gas (biogas). Among industrial technologies, dry processes (above 15 % total solid content) are more and more used because of their advantages in comparison with conventional wet processes. However, dry anaerobic digestion processes are poorly known and studied because of the pasty nature of digestion media (rheological behavior, equilibria, transfers, biological kinetics). This thesis focuses on two major aspects: i) the nature of the chemical equilibria (sorption, diffusion) involved in digestion media, ii) the establishment and application of a kinetic model adapted to dry media. We first demonstrated that the diffusional mass transfer is highly reduced with increasing total solid without any agitation. One of the consequences is the importance of the liquid-gas transfer for the production of biogas. Then, we have developed a dedicated kinetic model that enables to understand the variability of the kinetic with total solid content. The impacts of this work are both at the laboratory scale, especially for the operation of Specific Methanogenic Activity tests, and at industrial scale, with the need to control total solid content for optimal efficiency, and to adapt the agitation to improve degradation yields. The developed model can be useful for the design and operation of biomethanization facilities.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Use of path algebra tools for a unified description of a large class of pull control policies

International audienceMany pull policies can be found in the literature for controlling multistage production/inventory systems. In this paper, we present a framework that enables us to describe the dynamics of a large class of pull control policies, using the same set of canonical functions. The class of policies we consider here include well known pull policies, like kanban, CONWIP, basestock, generalized kanban, extended kanban, but also many other hybrid policies, and their extensions to systems producing batches. Each of these policies is characterized by the values of some parameters. These parameters values are calculated thanks to a computational algorithm that relies on the use of path algebra tools, especially (min,+) algebra tools. This canonical formulation allows to identify under which values of the control parameters, two different policies have the same dynamics behavior. It also enables to derive methods for evaluating and comparing the performance of several pull control policies, as we illustrate it in the paper

EEG Error-Related Potentials Detection With A Bayesian Filter

International audienceSeveral studies describe evoked EEG potentials elicited when a subject is aware of an erroneous decision either taken by him or by an external interface. This paper try to detect Error-related potentials (ErrP) elicited when a human user want to monitors an external system upon which he has no control whatsoever. To this end we use a Bayesian filter to classify erroneous or correct events. On average over three subjects, the proposed probabilistic classifier achieves single-trial classification of 85% for correct trials and 71% for erroneous trials

Interpersonal trust to enhance cyber crisis management

International audienceIn the field of cyber-security, software performance optimization is a major focus of research to better prevent cyber threats. However, once threats are detected, they have to be managed by a human operator or more often by human operators' joint actions. The purpose of this study is to show that in these collaborative situations, the interpersonal trust level between these actors shapes their handling of the threat. Forty-five participants performed, with twenty-eight different fictive teammates, a collaborative counting task that included aleatory phases of jamming. Each fictive teammate was described through two adjectives selected to induce a predefined level of interpersonal trust (low or high). The subject and his collaborator worked on different systems with different objects to count and different jamming phases. Nevertheless, each participant had the possibility of supervising his teammate's work by checking out his task and modifying his answers (number of targets and jamming events reported) if required. The subject was responsible for validating the team's final result. The experimental data show that, in this type of collaborative task, the interpersonal trust level has indeed an influence on the supervision strategy used and the team performance

Effect of Asbestos Consumption on Malignant Pleural Mesothelioma in Italy: Forecasts of Mortality up to 2040.

Statistical models used to forecast malignant pleural mesothelioma (MPM) trends often do not take into account historical asbestos consumption, possibly resulting in less accurate predictions of the future MPM death toll. We used the distributed lag non-linear model (DLNM) approach to predict future MPM cases in Italy until 2040, based on past asbestos consumption figures. Analyses were conducted using data on male MPM deaths (1970-2014) and annual asbestos consumption using data on domestic production, importation, and exportation. According to our model, the peak of MPM deaths is expected to occur in 2021 (1122 expected cases), with a subsequent decrease in mortality (344 MPM deaths in 2039). The exposure-response curve shows that relative risk (RR) of MPM increased almost linearly for lower levels of exposure but flattened at higher levels. The lag-specific RR grew until 30 years since exposure and decreased thereafter, suggesting that the most relevant contributions to the risk come from exposures which occurred 20-40 years before death. Our results show that the Italian MPM epidemic is approaching its peak and underline that the association between temporal trends of MPM and time since exposure to asbestos is not monotonic, suggesting a lesser role of remote exposures in the development of MPM than previously assumed

Quelques brefs commentaires sur l'article « Fiscalité de l'épargne en Europe »

Brief Comments on the Article « Taxation of Savings in Europe » We still do not possess the means for deliberations and the data enabling us to « think » in a European way on savings. On the subject of taxation of savings, more than a decade after the first European harmonisation efforts, the state of ignorance is all the more serious since the Commission, the Council and the European Parliament might adopt from 2002 onwards a directive on savings taxation. Therefore the least one can say is that the pioneer work carried out at the request of the European Savings Institute (Observatoire de l’Épargne Européenne) by Thierry Laurent and Yannick L’Horty is welcome. Certainly, it is a first attempt ; perhaps the authors have not sufficiently emphasised its very real limits and « academic » character, but it is extremely useful and opens the way for further indispensable work. JEL classifications : E21, E62, H20, H30, H87Nous ne disposions pas encore des outils de réflexion et des données nous permettant de « penser » de façon européenne en matière d’épargne. Plus précisément, en matière de fiscalité de l’épargne, plus d’une décennie après les premiers efforts européens d’harmonisation cette situation d’ignorance est d’autant plus grave que la Commission, le Conseil et le Parlement européens risquent d’adopter dès 2002 une directive sur l’imposition de l’épargne. C’est donc peu dire que le travail pionnier réalisé à la demande de l’Observatoire de l’Épargne Européenne (OEE) par Thierry Laurent et Yannick L’Horty est le bienvenu. Bien sûr, il s’agit d’une première tentative, dont les auteurs n’ont peut-être pas suffisamment souligné les limites et le caractère « académique », mais elle est extrêmement utile, et ouvre la voie à d’indispensables travaux ultérieurs. Classification JEL : E21, E62, H20, H30, H87Bollon Pierre. Quelques brefs commentaires sur l'article « Fiscalité de l'épargne en Europe » . In: Revue d'économie financière, n°64, 2001. Epargne et investissement en Europe. pp. 127-130

Bien gérer, c’est aussi bien voter

Good Management, Good Vote Since few years, French OPCVM managers have decided to take part in corporate governance. This evolution is based on the implementation of a collective process facilitating the exercise of voting rights. Four years after the beginning of this policy, author estimates first results. JEL classifications : G23, G30Depuis peu de temps, les gestionnaires français d’OPCVM ont décidé de jouer un rôle actif en matière de gouvernance des entreprises dans lesquelles ils investissent. Cette évolution, progressive mais résolue, s’est appuyée sur la mise en place, au niveau de l’ensemble de leur profession, d’un dispositif collectif leur facilitant l’exercice des droits de vote. Quatre ans après le lancement de cette politique, le premier bilan qui peut en être tiré, indubitablement positif, montre aussi qu’un long chemin reste à parcourir et que toutes les questions qu’elle pose ne sont pas résolues. Classification JEL : G23, G30Bollon Pierre. Bien gérer, c’est aussi bien voter . In: Revue d'économie financière, n°63, 2001. Le gouvernement d'entreprise . pp. 153-166