Diseño de un controlador de seguimiento para un sistema SISO de servoposicionamiento neumático

Pneumatic systems have many advantages, such as simplicity, reliability, low-cost, long life, etc. making them attractive for rapid development and widespread application, but the complexity of the airflow through the valve port and the friction between the cylinder and piston make it difficult to establish an exact mathematical model and control the pneumatic system with high precision. Experiments were conducted with a 25 mm bore rod-less pneumatic cylinder and a 5/3 way proportional control valve. In this contribution, I propose a nonlinear robust tracking control strategy to solve the tracking problem of the servo pneumatic positioning system. The approach is novel in the sense that it takes into account the nonlinearities inherent to pneumatic servo positioning systems and considers position, velocity and pressure difference in the chambers of the pneumatic cylinder as feedback states. The suggested control strategy is implemented in simulation and on the real system. Experimental results from an implementation on a test ring show a high position tracking control performance.Los sistemas neumáticos tienen varias ventajas que permitieron su rápido desarrollo y uso generalizado, tales como: simplicidad, confiabilidad, bajo costo, larga vida etc. Sin embargo, la complejidad del flujo de aire a través de los orificios de la válvula y la naturaleza de la fuerza de fricción entre las paredes del cilindro y el pistón, dificultan la obtención de modelos matemáticos exactos y el control de los sistemas neumáticos con alta precisión. Experimentos fueron llevados a cabo con un cilindro sin vástago de 25 mm de diámetro y una válvula de control proporcional de 5 puertos -3 vías. En este artículo, proponemos una estrategia de control de posicionamiento robusta para solucionar el problema de un sistema de servo posicionamiento neumático. El enfoque es novedoso en el sentido de que tiene en cuenta las no linealidades inherentes a los sistemas de servo posicionamiento neumático y considera posición, velocidad y diferencia de presiones en las cámaras del cilindro neumático como estados de retroalimentación.  La estrategia de control propuesta es implementada en simulación y sobre el sistema real. Los resultados experimentales de la implementación de la estrategia en el sistema de servo-posicionamiento  neumático muestran un alto desempeño en el control de seguimiento de posición

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Modélisation de la diversité microbienne dans les procédés de digestion anaérobie

Thèse sur articles soutenue le 18 décembre Diplôme : Dr. d'UniversitéThis new century addresses several environmental challenges among which distribution of drinking water, global warming and availability of new in substitution of fossil fuels are of the most importance. Among other renewable sources, biogas production from wastes is particularly interesting. Moreover, a techno-economical comparison demonstrated the benefits of a two-step process (H2+CH4) compared to the classical one-step methane production. Economic evaluation of biogas plants has revealed that many plants can only survive economically if special incentives are applied. Nowadays, it is thus necessary to find ways to optimize the biogas production in order to make biogas plants economically viable with decreased or no subsidies. Optimization of the biogas process by advanced monitoring and control can undoubtedly lead to better economy. Such strategies require, in general, the development of appropriate mathematical models, which adequately represent the main biological processes that take place. Moreover, experimental evidence is available suggesting that the structure and properties of a microbial community may be influenced by process operation and on their turn also determine the reactor functioning. In order to adequately describe these phenomena, more detailed microbial diversity should be taken up in mathematical models. This was demonstrated in this work by extending the ADM1 model to describe microbial diversity between organisms of the same functional group. The developed model was further shown useful in assessing the relationship between reactor performance and microbial community structure in different conditions: difference in reactor configurations, influents and load regimes, both in normal and abnormal situations. As engineered systems are often more manageable than large-scale ecosystems, and because parallels between engineered environments and other ecosystems exist, we showed in this work that the former was used to elucidate some unresolved microbial ecological issues.Le XXIème siècle sera pour l’Homme le siècle de grands enjeux environnementaux tels que l’amélioration de l’accès à une eau potable, la lutte contre le réchauffement climatique et le développement de nouvelles sources d’énergie afin de substituer les énergies fossiles. Une source d’énergie renouvelable très prometteuse est la production de biogaz à partir de déchets organiques. De plus, une étude technico-économique des filières de production de méthane et de biohydrogène a permis de démontrer les avantages d’un procédé en deux étapes (H2+CH4) comparé à un procédé classique en une étape (CH4). Cependant, la viabilité économique des unités de production de biogaz dépend fortement des encouragements réalisés par les pouvoirs politiques en faveur de cette nouvelle source d’énergie. Il est donc nécessaire d’élaborer des méthodes d’optimisation de la production de biogaz pour améliorer la viabilité économique de ces procédés. Le suivi et le contrôle avancé des procédés est une méthode capable d’optimiser les performances et donc le gain économique des unités de production. Cette technique nécessite de concevoir des modèles mathématiques appropriés, intégrant les processus biologiques présents au sein du réacteur. En effet, les études expérimentales ont montré que la structure et la diversité des communautés microbiennes peuvent influencer le fonctionnement du réacteur, mais elles peuvent aussi être influencées par les conditions opératoires du procédé. Ainsi, les modèles mathématiques doivent décrire de façon plus détaillée la biodiversité de ces systèmes afin de mieux représenter les phénomènes existants. Notre étude a permis de mettre en évidence ces relations à travers le modèle ADM1 modifié, qui est capable de décrire la diversité microbienne entre les micro-organismes d’un même groupe fonctionnel. Le modèle développé a été utilisé pour estimer la relation entre les performances du réacteur et la structure des communautés microbiennes dans différentes conditions : utilisation de différentes configurations de réacteurs, différents substrats d’alimentation, différentes charges d’alimentation, en fonctionnement normal et en présence de perturbations. Etant donné que les systèmes industriels sont bien souvent plus contrôlables que les écosystèmes grandeur nature, et parce que les parallèles entre les environnements industriels et les autres écosystèmes existent, nous démontrons dans ce travail qu’il est possible de les utiliser afin d’élucider certaines interrogations de l’écologie encore non résolues

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2