31 research outputs found
Méthodes scalables de commande par allocation pour le convertisseur modulaire multiniveaux : de la modélisation à l'implémentation temps réel
Dans le cadre de la montĂ©e en puissance des convertisseurs statiques, les diffĂ©rents avantages quâil y a Ă utiliser les Convertisseurs Modulaires Multiniveaux (MMC) ont menĂ© Ă leur popularisation. Cependant, Ă mesure que le nombre de niveaux de tension et le nombre de phase augmentent, ces convertisseurs prĂ©sentent un nombre de plus en plus important de degrĂ©s de libertĂ© pour en effectuer la commande. Ainsi les MMC reprĂ©sentent un dĂ©fi pour la commande car le nombre de variables de commande est alors supĂ©rieur aux contraintes Ă satisfaire, faisant dâeux des systĂšmes redondants ou encore sous-dĂ©terminĂ©s ce qui ouvre la voie de lâoptimisation. Dâabord apparues dans les annĂ©es 1980 dans lâaĂ©ronautique pour tirer profit de la multiplicitĂ© des surfaces aĂ©rodynamiques et des redondances associĂ©es que prĂ©sente un avion afin dâen contrĂŽler sa trajectoire (volets, ailerons, gouvernesâŠ), les mĂ©thodes de commande par allocation ont fait leurs preuves en Ă©tant progressivement appliquĂ©es dans diffĂ©rents domaines technologiques. En parallĂšle ces algorithmes ont fait lâobjet de travaux pour amĂ©liorer les performances obtenues et notamment sâadapter aux systĂšmes commandĂ©s.
Le sujet de la thĂšse concerne donc le dĂ©veloppement et lâimplĂ©mentation en temps rĂ©el de mĂ©thodes de commande par allocation, avec un souci dâoptimisation en ligne, pour un systĂšme de conversion dâĂ©nergie Ă base de MMC.
La premiĂšre partie de la thĂšse portent sur la modĂ©lisation du convertisseur MMC en vue de sa commande Ă partir de mĂ©thodes dâallocation. Ce qui implique le dĂ©veloppement de diffĂ©rents modĂšles de commande avec diffĂ©rents niveaux de dĂ©tails et de complexitĂ©. Un rĂ©sultat fort issu de cette premiĂšre partie est un modĂšle de commande dont la complexitĂ© nâest plus influencĂ©e par le nombre de phases du systĂšme Ă©lectrique considĂ©rĂ©.
La deuxiĂšme Ă©tape des travaux concerne le dĂ©veloppement dâune nouvelle mĂ©thode dâallocation qui met Ă profit les avantages des mĂ©thodes prĂ©sentes dans lâĂ©tat de lâart pour en concevoir une nouvelle plus adaptĂ©e. Ainsi cette dĂ©marche a conduit Ă la programmation dâun nouvel algorithme dâallocation prĂ©sentant des caractĂ©ristiques dynamiques et statiques rĂ©glables et adaptables simplement, son intĂ©gration aux mĂ©thodes dĂ©jĂ existantes est aisĂ©e et presque immĂ©diat.
La troisiĂšme Ă©tape des travaux combine les travaux prĂ©cĂ©dents. Tout dâabord en simulation, la mĂ©thode de commande par allocation du convertisseur est programmĂ©e puis testĂ©e pour finalement ĂȘtre validĂ©e. Pour la commande diffĂ©rentes architectures sont conçues permettant de rĂ©aliser des comparatifs afin dâĂ©valuer leur capacitĂ© Ă atteindre les performances requises pour le bon fonctionnement du systĂšme. Il en dĂ©coule une analyse des diffĂ©rents algorithmes de commande proposĂ©s. Le rĂ©sultat principal de cette partie est la conception dâun nouvel algorithme dâallocation permettant de contrĂŽler les tensions aux bornes des condensateurs ainsi que les tous les courants du convertisseur dans chacune des branches et ce indĂ©pendamment du nombre de phases.
La quatriĂšme Ă©tape porte sur la validation expĂ©rimentale des mĂ©thodes dĂ©veloppĂ©es. Pour se faire, le convertisseur MMC disponible au laboratoire LAPLACE est utilisĂ© ainsi quâun ensemble dâoutils de prototypage rapide (OPAL-RT) permettant de tester et mettre au point les algorithmes de façon sĂ»re et efficace.
La cinquiĂšme partie des travaux concerne lâextension, hors de la zone de fonctionnement nominale du convertisseur, des algorithmes de commande dĂ©veloppĂ©s. En effet une ouverture est proposĂ©e mettant en exergue les capacitĂ©s des mĂ©thodes dâallocation Ă reconfigurer le fonctionnement du MMC lorsquâun dĂ©faut apparait dans lâun des sous-modules. Les rĂ©sultats obtenus en simulation montrent une amĂ©lioration de la disponibilitĂ© du convertisseur, câest-Ă -dire une continuitĂ© de fonctionnement en prĂ©sence de dĂ©fauts ce qui justifie lâintĂ©rĂȘt de poursuivre les travaux dans cette direction
Associations of biomechanical properties of the cornea with environmental and metabolic factors in an elderly population : the ALIENOR study
PURPOSE: The purpose of this study was to assess the associations of biomechanical properties of the cornea with metabolic and environmental factors in an elderly population. METHODS: The ALIENOR (Antioxydants, Lipides Essentiels, Nutrition, and Maladies OculaiRes) study is a population-based study. In 2009-2010, 624 subjects, aged 74 years or more, underwent an eye examination, including intraocular pressure (IOP), central corneal thickness (CCT), and biomechanical properties of the cornea measurements using the Ocular Response Analyzer. Socio-demographic, lifestyle, and medical history data were collected using standardized questionnaires. Mean lifetime ambient ultraviolet (UV) exposure was estimated using residential history and statistics of UV radiation at each location using the Eurosun UV database. RESULTS: Mean age was 82.2 ± 4.3 years. Mean corneal hysteresis (CH), corneal resistance factor (CRF), and CCT were 9.4 ± 1.9, 9.8 ± 1.9 mm Hg, and 551.6 ± 36.8 Όm, respectively. In the multivariate analysis, CH and CRF values were significantly lower in subjects older than 80 years (-0.56; 95% confidence interval [CI]: -0.89;-0.24); P < 0.001 and -0.48; 95% CI: -0.75;-0.20; P < 0.001, respectively), in subjects having higher ambient UV exposure (-0.50; 95% CI: -0.88;-0.12; P < 0.01; and -0.46; 95% CI: -0.78;-0.13); P < 0.05, respectively), and in subjects with high plasma LDL cholesterol (CH: -0.46; 95% CI: -0.86;-0.03; P < 0.05; and CRF: -0.37; 95% CI: -0.72;-0.008; P < 0.05). Central corneal thickness was significantly higher in former smokers than in never smokers (+11.01; 95% CI: 0.48;21.55; P < 0.05) and was not significantly associated with age, ambient UV exposure, diabetes, or LDL cholesterol. CONCLUSIONS: Biomechanical properties of the cornea are modified by metabolic and lifetime environmental factors, especially UV exposure. The manner these factors may influence onset and progression of ocular diseases or IOP measurements need further investigation
Electrical spinal cord stimulation must preserve proprioception to enable locomotion in humans with spinal cord injury
Epidural electrical stimulation (EES) of the spinal cord restores locomotion in animal models of spinal cord injury but is less effective in humans. Here we hypothesized that this interspecies discrepancy is due to interference between EES and proprioceptive information in humans. Computational simulations and preclinical and clinical experiments reveal that EES blocks a significant amount of proprioceptive input in humans, but not in rats. This transient deafferentation prevents modulation of reciprocal inhibitory networks involved in locomotion and reduces or abolishes the conscious perception of leg position. Consequently, continuous EES can only facilitate locomotion within a narrow range of stimulation parameters and is unable to provide meaningful locomotor improvements in humans without rehabilitation. Simulations showed that burst stimulation and spatiotemporal stimulation profiles mitigate the cancellation of proprioceptive information, enabling robust control over motor neuron activity. This demonstrates the importance of stimulation protocols that preserve proprioceptive information to facilitate walking with EES
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transientâs position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
Ophthalmology
PURPOSE: To investigate systemic and ocular determinants of peripapillary retinal nerve fiber layer thickness (pRNFLT) in the European population. DESIGN: Cross-sectional meta-analysis. PARTICIPANTS: A total of 16 084 European adults from 8 cohort studies (mean age range, 56.9+/-12.3-82.1+/-4.2 years) of the European Eye Epidemiology (E3) consortium. METHODS: We examined associations with pRNFLT measured by spectral-domain OCT in each study using multivariable linear regression and pooled results using random effects meta-analysis. MAIN OUTCOME MEASURES: Determinants of pRNFLT. RESULTS: Mean pRNFLT ranged from 86.8+/-21.4 mum in the Rotterdam Study I to 104.7+/-12.5 mum in the Rotterdam Study III. We found the following factors to be associated with reduced pRNFLT: Older age (beta = -0.38 mum/year; 95% confidence interval [CI], -0.57 to -0.18), higher intraocular pressure (IOP) (beta = -0.36 mum/mmHg; 95% CI, -0.56 to -0.15), visual impairment (beta = -5.50 mum; 95% CI, -9.37 to -1.64), and history of systemic hypertension (beta = -0.54 mum; 95% CI, -1.01 to -0.07) and stroke (beta = -1.94 mum; 95% CI, -3.17 to -0.72). A suggestive, albeit nonsignificant, association was observed for dementia (beta = -3.11 mum; 95% CI, -6.22 to 0.01). Higher pRNFLT was associated with more hyperopic spherical equivalent (beta = 1.39 mum/diopter; 95% CI, 1.19-1.59) and smoking (beta = 1.53 mum; 95% CI, 1.00-2.06 for current smokers compared with never-smokers). CONCLUSIONS: In addition to previously described determinants such as age and refraction, we found that systemic vascular and neurovascular diseases were associated with reduced pRNFLT. These may be of clinical relevance, especially in glaucoma monitoring of patients with newly occurring vascular comorbidities
Scalable Control Allocation Methods for the Modular Multilevel Converter : from Modelling to Real Time Implementation
Dans le cadre de la montĂ©e en puissance des convertisseurs statiques, les diffĂ©rents avantages quâil y a Ă utiliser les Convertisseurs Modulaires Multiniveaux (MMC) ont menĂ© Ă leur popularisation. Cependant, Ă mesure que le nombre de niveaux de tension et le nombre de phase augmentent, ces convertisseurs prĂ©sentent un nombre de plus en plus important de degrĂ©s de libertĂ© pour en effectuer la commande. Ainsi les MMC reprĂ©sentent un dĂ©fi pour la commande car le nombre de variables de commande est alors supĂ©rieur aux contraintes Ă satisfaire, faisant dâeux des systĂšmes redondants ou encore sous-dĂ©terminĂ©s ce qui ouvre la voie de lâoptimisation. Dâabord apparues dans les annĂ©es 1980 dans lâaĂ©ronautique pour tirer profit de la multiplicitĂ© des surfaces aĂ©rodynamiques et des redondances associĂ©es que prĂ©sente un avion afin dâen contrĂŽler sa trajectoire (volets, ailerons, gouvernesâŠ), les mĂ©thodes de commande par allocation ont fait leurs preuves en Ă©tant progressivement appliquĂ©es dans diffĂ©rents domaines technologiques. En parallĂšle ces algorithmes ont fait lâobjet de travaux pour amĂ©liorer les performances obtenues et notamment sâadapter aux systĂšmes commandĂ©s.Le sujet de la thĂšse concerne donc le dĂ©veloppement et lâimplĂ©mentation en temps rĂ©el de mĂ©thodes de commande par allocation, avec un souci dâoptimisation en ligne, pour un systĂšme de conversion dâĂ©nergie Ă base de MMC.La premiĂšre partie de la thĂšse portent sur la modĂ©lisation du convertisseur MMC en vue de sa commande Ă partir de mĂ©thodes dâallocation. Ce qui implique le dĂ©veloppement de diffĂ©rents modĂšles de commande avec diffĂ©rents niveaux de dĂ©tails et de complexitĂ©. Un rĂ©sultat fort issu de cette premiĂšre partie est un modĂšle de commande dont la complexitĂ© nâest plus influencĂ©e par le nombre de phases du systĂšme Ă©lectrique considĂ©rĂ©.La deuxiĂšme Ă©tape des travaux concerne le dĂ©veloppement dâune nouvelle mĂ©thode dâallocation qui met Ă profit les avantages des mĂ©thodes prĂ©sentes dans lâĂ©tat de lâart pour en concevoir une nouvelle plus adaptĂ©e. Ainsi cette dĂ©marche a conduit Ă la programmation dâun nouvel algorithme dâallocation prĂ©sentant des caractĂ©ristiques dynamiques et statiques rĂ©glables et adaptables simplement, son intĂ©gration aux mĂ©thodes dĂ©jĂ existantes est aisĂ©e et presque immĂ©diat.La troisiĂšme Ă©tape des travaux combine les travaux prĂ©cĂ©dents. Tout dâabord en simulation, la mĂ©thode de commande par allocation du convertisseur est programmĂ©e puis testĂ©e pour finalement ĂȘtre validĂ©e. Pour la commande diffĂ©rentes architectures sont conçues permettant de rĂ©aliser des comparatifs afin dâĂ©valuer leur capacitĂ© Ă atteindre les performances requises pour le bon fonctionnement du systĂšme. Il en dĂ©coule une analyse des diffĂ©rents algorithmes de commande proposĂ©s. Le rĂ©sultat principal de cette partie est la conception dâun nouvel algorithme dâallocation permettant de contrĂŽler les tensions aux bornes des condensateurs ainsi que les tous les courants du convertisseur dans chacune des branches et ce indĂ©pendamment du nombre de phases.La quatriĂšme Ă©tape porte sur la validation expĂ©rimentale des mĂ©thodes dĂ©veloppĂ©es. Pour se faire, le convertisseur MMC disponible au laboratoire LAPLACE est utilisĂ© ainsi quâun ensemble dâoutils de prototypage rapide (OPAL-RT) permettant de tester et mettre au point les algorithmes de façon sĂ»re et efficace. La cinquiĂšme partie des travaux concerne lâextension, hors de la zone de fonctionnement nominale du convertisseur, des algorithmes de commande dĂ©veloppĂ©s. En effet une ouverture est proposĂ©e mettant en exergue les capacitĂ©s des mĂ©thodes dâallocation Ă reconfigurer le fonctionnement du MMC lorsquâun dĂ©faut apparait dans lâun des sous-modules. Les rĂ©sultats obtenus en simulation montrent une amĂ©lioration de la disponibilitĂ© du convertisseur, câest-Ă -dire une continuitĂ© de fonctionnement en prĂ©sence de dĂ©fauts ce qui justifie lâintĂ©rĂȘt de poursuivre les travaux dans cette direction.In the context of a rise in the use of static power converters, the beneficial features of Multilevel Modular Converters (MMCs) have led to their popularization. However, as the number of voltage levels and the number of phases increases, these converters have an increasing number of degrees of freedom to handle. Thus, MMCs represent a challenge for control because the number of control variables is higher than the constraints to be satisfied, making them overactuated systems and opening the way to optimization. Having first appeared in the 1980s in aeronautics to take advantage of the multiplicity of aerodynamic and redundant surfaces that an aircraft presents in order to control its trajectory (flaps, ailerons, control surfaces...), the control allocation methods have proven their worth and were progressively applied in different technologic fields. At the same time, control allocation has been the topic of research works leading to the integration of optimization algorithms in these control methods.The thesis concerns the development and implementation of real-time control allocation methods, with a focus on online optimization, for an MMC-based power conversion system.The first part of the thesis focuses on the control-oriented modelling of the MMC converter for the application of allocation methods. This step involves the development of different control models with different levels of detail and complexity. A strong result of this first part is a control model whose complexity is no longer impacted by the number of phases of the considered electrical system.The second part of the work concerns the development of a new allocation method for MMCs that takes advantage of the beneficial features of state-of-the-art methods. This approach leads to the programming of a new allocation algorithm with dynamic and static characteristics that can be easily adjusted and adapted. Its integration with existing methods is readily and seamlessly achieved.The third part of the work combines the two previous steps. First in simulation, the control allocation method of the converter is programmed and then tested and validated. For control, different architectures are designed and compared in order to evaluate their ability to achieve the performance required for the proper operation of the system. An analysis of the different control algorithms is then carried out. The main result of this part is the design of a new allocation algorithm allowing one to control the voltages across the capacitors as well as all the currents in each branch of the converter, achieving this result independently of the number of phases.The fourth step is about the experimental validation of the developed methods. To do so, the MMC converter available at the LAPLACE laboratory is used as well as a set of rapid prototyping tools (OPAL-RT) allowing to test and develop the algorithms in a safe and efficient way using a Hardware-In-the-Loop (HIL) technique.The fifth part of the work concerns the extension of the control algorithms outside the nominal operating zone of the converter. An approach is considered highlighting the capabilities of the allocation methods to reconfigure the operation of the MMC when a fault appears in one of the sub-modules. The results obtained in simulations show an improvement of the resilience of the converter, i.e., a continuity of operation in the presence of faults that justifies a future continuation of the work in that direction.The proposed contributions then conclude with perspectives for future exploration and investigation on the topic of allocation methods in electrical engineering
Skin autofluorescence of Advanced Glycation End-products and mortality in older adults: The roles of chronic kidney disease and diabetes
BACKGROUND AND AIM: Advanced glycation end products are involved in age-related multisystem decline. They accumulate in body tissues with age, diabetes and chronic kidney disease (CKD), and can be measured non-invasively by the skin autofluorescence (SAF). We studied the relation between SAF and later mortality in old adults. METHODS AND RESULTS: The SAF was measured using an AGE-Reader in 451 individuals from the general population aged over 75 years, and all-cause mortality was assessed during an average follow-up of 6.4 years. The association between SAF and mortality was analyzed using a multivariate Cox survival model, adjusted for age and gender. Analyses were further adjusted for diabetes and stratified on the presence of CKD due to its interaction with SAF for the risk of mortality. Participants were 82 years old on average (SD 4.1). Their mean SAF was 2.8 AU (SD 0.6). One hundred and forty-four individuals (31.9%) died during the follow-up. Adjusted for age and gender, SAF was associated with an increased risk of all-cause mortality (HR 1.44, 95%CI: 1.14-1.82 for a one-AU increase of SAF). The association was no longer significant after adjustment for diabetes. However, after stratification for the presence of CKD, higher SAF was associated with an increased risk of all-cause mortality in the participants with CKD at baseline (HR 1.68, 95%CI: 1.11-2.55), whereas there was no association among participants without CKD (HR 0.95, 95%CI: 0.63-1.44). CONCLUSION: Skin autofluorescence is associated with increased all-cause mortality in older adults already suffering from CKD
JAMA Ophthalmol
Importance Although retinal multimodal imaging is needed for diagnosing reticular pseudodrusen (RPD), the incidence of RPD in the general population typically has been assessed only using fundus photographs, which may underestimate their incidence. Objectives To describe the incidence of RPD using retinal color photographs, spectral-domain optical coherence tomography scans, fundus autofluorescence, and near-infrared reflectance images among individuals 77 years of age or older and to analyze the associated risk factors of RPD. Design, Setting, and Participants The ALIENOR (Antioxydants, Lipides Essentiels, Nutrition et Maladies Oculaires) Study is a cohort of French individuals 77 years of age or older. Data for this study were collected between February 22, 2011, and February 15, 2017, with a mean (SD) follow-up of 3.7 (1.0) years (range, 1.2-5.6 years). At baseline, 501 individuals were eligible to participate. Of 1002 eyes, 197 had prevalent RPD, advanced age-related macular degeneration, or ungradable images. Of the remaining 805 eyes, 333 were missing follow-up data; therefore, the statistical analyses included data from 472 eyes. Data management and statistical analyses were performed between March 15, 2017, and April 5, 2019. Main Outcomes and Measures Reticular pseudodrusen were considered as present if detected by at least 2 of the following imaging methods: color fundus photographs, fundus autofluorescence, near-infrared reflectance, and spectral-domain optical coherence tomography images. Results Of the 472 eyes analyzed, 263 (55.7%) were from female participants, and the mean (SD) age was 81.9 (3.2) years. Forty-three eyes developed RPD, corresponding to an annual incidence rate of 2.9% (95% CI, 1.9%-4.4%) per participant and an estimated 5-year risk of 13.5%. In multivariable analysis, 4 risk factors of incident RPD were identified: subfoveal choroidal thinning (hazard ratio [HR], 0.99; 95% CI, 0.99-1.00 per 10-ÎŒm decrease in thickness; Pâ=â.02) and the presence of the minor allelic variants rs10490924 for ARMS2 (HR, 3.57; 95% CI, 1.80-7.10; Pâ<â.001), rs1061170 for CFH (HR, 2.12; 95% CI, 1.02-4.41; Pâ=â.04), and rs10468017 for LIPC (HR, 2.57; 95% CI, 1.37-4.82; Pâ=â.003). Lipophilic statin therapy was associated with a lower incidence of RPD (HR, 0.13; 95% CI, 0.02-0.74; Pâ=â.02). Conclusions and Relevance With the use of multimodal imaging, the RPD incidence rate was higher than previously reported in other population-based studies using fundus color images. Individuals with subfoveal choroidal thinning or carrying minor allelic variants for ARMS2, CFH, or LIPC had an increased risk for RPD, whereas lipophilic statin therapy was associated with a lower incidence
Kinetics of Cardiac Remodeling and Fibrosis Biomarkers During an Extreme Mountain Ultramarathon
ObjectivesThe effects of ultra-distance on cardiac remodeling and fibrosis are unclear. Moreover, there are no data reporting the kinetics of cardiac alterations throughout the event and during recovery. Our aim was to investigate the kinetics of biological markers including new cardiac fibrosis biomarkers suppression of tumorigenicity 2 (ST2) and galectin-3 (Gal-3) during and after an extreme mountain ultramarathon.MethodsFifty experienced runners participating in one of the most challenging mountain ultramarathons (330 km, D+ 25,000 m) were enrolled in our study. Blood samples were collected at four time points: before (Pre-), at 148 km (Mid-), at the finish line (Post-), and 3 days after the recovery period (Recov-).ResultsThe cardiac fibrosis biomarkers (ST2 and Gal-3) increased from Pre- to Mid-. During the second half, ST2 remained higher than pre-values as opposed to Gal-3. Necrosis, ischemia, and myocyte injury biomarkers increased until Mid- then decreased but remained higher at Recov- than Pre-values. Oxidative stress appeared at Mid-. Lipid peroxides remained higher at Recov- compared to Pre-. The maximal value in most of these biomarkers was observed at Mid- and not at Post-.ConclusionsThe present study supports biphasic kinetics of cardiac fibrosis biomarkers, with a relative recovery during the second half of the event that seems specific to this extreme event. Overall, performing at such an extreme ultramarathon seems less deleterious for the heart than shorter events