Optimal design of a wound rotor synchronous generator using genetic algorithm

International audienceThe manufacturers are tempted to reduce the amount of active materials in the devices in order to lower the material bill. However, reducing the weight of the devices directly affects the energy efficiency. In this paper, a solution to this problem is proposed for the case of synchronous wound rotor generators. The trade-off between cost and efficiency is formulated as a constrained optimization problem and solved using a Genetic Algorithm. The cost optimization of three different machines is carried out through various design approaches. The proposed approach always gives better results than the classical approach concerning the global cost of the range

Modélisation analytique d'un moteur synchro-réluctant assisté d'aimants permanents

L'article présente un modèle analytique électromagnétique pour un Moteur Synchro-Réluctant Assisté d'Aimants Permanents (MSR-AP). Le modèle proposé se base sur les équations de Maxwell : le théorème d'Ampère et la loi de conservation de flux. La saturation magnétique dans le stator et le rotor est prise en considération, ainsi que l'influence des ponts magnétiques des barrières de flux. Le but est de calculer les performances du moteur (couple électromagnétique, tension phase-phase et facteur de puissance) pour plusieurs valeurs de courants et d'angles de calage. Les résultats du modèle analytique sont comparés à ceux des éléments finis (MEF) et sont validés par des essais sur un prototype de moteur

Fibrin monomers evaluation during hospitalization for COVID-19 is a predictive marker of in-hospital mortality

BackgroundCoagulopathy is one of the main triggers of severity and worsening of Coronavirus disease 2019 (COVID-19) particularly in critically ill patients. D-dimer has been widely used to detect COVID-19 coagulation disorders and has been correlated with outcomes such as disease severity and in-hospital mortality. Involvement of other fibrin degradation products, particularly fibrin monomers (FM), remains an ongoing question.MethodsWe performed a monocentric study of adult patients with COVID-19, who were admitted either in the medical ward (MW) or in the intensive care unit (ICU) and who had FM measurements performed on them during the first wave of COVID-19 outbreak. We analyzed the positivity of FM levels (FM > 7 µg/mL) to assess the ability of FM monitoring during the first days of hospitalization to predict COVID-19 outcomes.ResultsIn our cohort, 935 FM measurements were performed in 246 patients during their first 9 days of hospitalization. During patient follow-up, the FM levels were higher in patients admitted directly to the ICU than in those admitted to the MW. Moreover, we observed significantly increased levels of FM in patients when the data were stratified for in-hospital mortality. At hospital admission, only 27 (11%) patients displayed a positive value for FM; this subgroup did not differ from other patients in terms of severity (indicated by ICU referral at admission) or in-hospital mortality. When analyzing FM positivity in the first 9 days of hospitalization, we found that 37% of patients had positive FM at least once during hospitalization and these patients had increased in-hospital mortality (p = 0.001). Thus, we used non-adjusted Kaplan–Meier curves for in-hospital mortality according to FM positivity during hospitalization and we observed a statistically significant difference for in-hospital mortality (hazard ratio = 1.48, 95% CI: 1.25–1.76, p < 0.001). However, we compared the AUC of FM positivity associated with a ratio of D-dimer >70% and found that this combined receiver operating characteristic (ROC) curve was superior to the FM positivity ROC curve alone.ConclusionMonitoring of FM positivity in hospitalized patients with COVID-19 could be a reliable and helpful tool to predict the worsening condition and mortality of COVID-19

Melanocortin-1 Receptor, Skin Cancer and Phenotypic Characteristics (M-SKIP) Project: Study Design and Methods for Pooling Results of Genetic Epidemiological Studies

Background: For complex diseases like cancer, pooled-analysis of individual data represents a powerful tool to investigate the joint contribution of genetic, phenotypic and environmental factors to the development of a disease. Pooled-analysis of epidemiological studies has many advantages over meta-analysis, and preliminary results may be obtained faster and with lower costs than with prospective consortia. Design and methods: Based on our experience with the study design of the Melanocortin-1 receptor (MC1R) gene, SKin cancer and Phenotypic characteristics (M-SKIP) project, we describe the most important steps in planning and conducting a pooled-analysis of genetic epidemiological studies. We then present the statistical analysis plan that we are going to apply, giving particular attention to methods of analysis recently proposed to account for between-study heterogeneity and to explore the joint contribution of genetic, phenotypic and environmental factors in the development of a disease. Within the M-SKIP project, data on 10,959 skin cancer cases and 14,785 controls from 31 international investigators were checked for quality and recoded for standardization. We first proposed to fit the aggregated data with random-effects logistic regression models. However, for the M-SKIP project, a two-stage analysis will be preferred to overcome the problem regarding the availability of different study covariates. The joint contribution of MC1R variants and phenotypic characteristics to skin cancer development will be studied via logic regression modeling. Discussion: Methodological guidelines to correctly design and conduct pooled-analyses are needed to facilitate application of such methods, thus providing a better summary of the actual findings on specific fields

Optimised design of a transformer and an electronic circuit for IGBT drivers signal impulse transmission function based on a virtual prototyping tool

International audienceIn this study, a signal impulse transmission function is investigated which provides high insulation voltage capabilities for IGBT drivers devices. This electrical insulation is achieved with a printed circuit board (PCB) and classical copper windings. Two ferrite cores are added to improve the magnetic coupling effect and thus decrease the impulse current maximum value in the primary side. The electronic circuit involves a series resonant topology in the primary side and a parallel one in the secondary side. The classical electronic components lead potentially to cost-effective solutions. However, so as to optimise the proposed system, a design methodology based on virtual prototyping tools is carried out. The simulation results presented on a Pareto front are analysed with the help of propagation delay and average power consumption. Moreover, measurement results with a 1.6 mm PCB are compared with simulation ones. Finally, the proposed solution and the methodology design are clearly accurate and suitable for power electronic designers and especially for IGBT driver devices designers

Virtual prototyping and pre-sizing methodology for buck DC-DC converters using genetic algorithms

International audienceIn this article, the authors study the pre-sizing approach of DC-DC buck converters useful for electronics and system designers. The pre-sizing step in an industrial process is suitable to obtain a preliminary precise sizing of a sub-system (here a buck DC-DC converter): it permits the system designer to perform a feasibility analysis of an overall system (e.g. that contains a buck DC-DC converter). First, static modelling of power devices is proposed: MOSFET, diode, inductor and heatsink. According to an industrial context, the MOSFETs, diodes and heatsinks fitting curves are issued from the manufacturer-s datasheets. Second, the objective functions are explained in the case of mixed integer programming problems. Then, the optimisation variables and constraints are highlighted. Third, a section describes the choice of a multi-objective optimisation technique that leads to genetic algorithms (GAs). Fourth, the optimisation results are given. The choice of a final solution of the pre-sizing approach is discussed, considering additional constraints such as diode and MOSFET junctions temperatures, switching frequency etc. The authors focus on the general aspect of the optimisation method proposed here. It can also be used by power electronics designers with the help of additional constraints in accordance to their specific applications

How to report and compare quantitative variables in a radiology article

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