Un modèle de lubrification en régime mixte du laminage : Frottement et lubrification en mise en forme = A mixed lubrication model of the cold strip rolling process

Free access articleInternational audienceLe régime de lubrification mixte est le plus fréquemment rencontré en laminage à froid. Sa modélisation est le but de cet article. La lubrification, phénomène interfacial, est fortement couplée à la mécanique de l'opération de laminage. C'est pourquoi le modèle présenté assemble un modèle macroscopique de laminage (méthode des tranches élasto-plastique) et un modèle microscopique de lubrification en régime mixte, lui-même composé d'une équation de Reynolds entre surfaces rugueuses (formation du film lubrifiant) et d'une équation d'évolution de la rugosité, par conformation de la tôle au cylindre. Les principes du modèle sont présentés, comparés à ceux de la bibliographie, ses hypothèses et ses résultats sont discutés, et quelques applications sont évoquées = The mixed regime of lubrication is most frequently encountered in cold strip rolling processes. A model is presented hereafter. The lubrication at the interface is closely coupled with the mechanics of the rolling process. Therefore, the proposed model combines a macroscopic model of rolling (elastic-plastic slab method) with a microscopic mixed lubrication model, consisting of a Reynolds equation for rough surfaces (describing the formation of the lubricant film) and an equation for the evolution of roughness, describing the conformation of the strip surface to the roll. The bases of the model are presented and compared to models in the literature; its hypotheses and results are discussed, a few applications are given

Compréhension et modélisation du régime mixte : synthèse des avancées et perspectives d'applications industrielles : Frottement et lubrification en mise en forme = Understanding and modelling the mixed lubrication regime: summary of achievements and perspectives of industrial applications

Free access articleInternational audienceL'ensemble des travaux décrits précédemment, et résumés ici, a d'ores et déjà fait l'objet de mises en application diverses, qui sont décrites dans cette courte conclusion: explication d'observations sur sites de production, modèles de connaissance, nouvelles idées de formulation de lubrifiants, qui ne demandent qu'à être testées. Bien sûr, l'ensemble des besoins de connaissances et de nouveaux outils n'a pas été satisfait, et quelques pistes de travaux futurs sont dégagées = The works described previously, and summarized here, have already been applied under various forms, to be described hereafter: explanation of industrial observations, knowledge models, new ideas for lubricant formulation, which now have to be tested. Of course, not all the needs of industry have been fulfilled, so that perspectives for further research are highlighted

Acetonitrilo-Agua: estudio y simulación de procesos de separación de una mezcla azeotrópica

Els processos de separació són una part molt important del sector químic, hi ha un gran nombre de mescles que no es poden separar pels mètodes convencionals pel fet que presenten azeotrops que impedeixen l'obtenció dels productes amb el nivell de puresa requerit per a les diferents aplicacions en les quals siguin necessaris. En aquest projecte es realitza un estudi amb la barreja acetonitril-aigua que s'obté com a subproducte de l'obtenció d’acrilonitril. Per a trobar un mètode eficient de separació d’ acetonitril (compost de gran importància en la indústria farmacèutica i com a solvent) es comparen diferents opcions viables de separació de mescles que presentis un punt azeotròpic. S’han triat les dues més prometedores que en aquest cas són la separació per canvis de pressió i la destil·lació extractiva per a dissenyar uns processos optimitzant tots els elements que conformin el sistema a través del simulador ASPEN PLUS V12. Finalment, s'analitzen diferents opcions per a reduir l'energia requerida per les diferents columnes de destil·lació i bescanviadors de calor i es calculen tant els costos com l'impacte ambiental que puguin tenir cadascuna de les simulacions per a poder discernir quin projecte finalment seria el més adequat per a dur-se a terme.Los procesos de separación son una parte muy importante del sector químico, hay un gran número de mezclas que no se pueden separar por los métodos convencionales debido a que presentan azeotropos que impiden la obtención de los productos con el nivel de pureza requerido para las diferentes aplicaciones en las que sean necesario. En este proyecto se realiza un estudio a con la mezcla acetonitrilo-agua que se obtiene como subproducto de la obtención de acrilonitrilo. Para encontrar un método eficiente de obtención de acetonitrilo (compuesto de gran importancia en la industria farmacéutica y como solvente) se comparan diferentes opciones viables de separación de mezclas que presentes un punto azeotrópico, donde se ha acabado eligiendo las dos más prometedoras que en este caso son la separación por cambios de presión y la destilación extractiva para diseñar unos procesos optimizando todos los elementos que conformen el sistema a través del simulador ASPEN PLUS V12. Finalmente, se analizan diferentes opciones para reducir la energía requerida por las diferentes columnas de destilación e intercambiadores de calor y se calculan tanto los costes como el impacto ambiental que puedan tener cada una de las simulaciones para poder discernir qué proyecto finalmente sería el más adecuado para llevarse a cabo.Separation processes are a key part of the chemical sector. There are a large number of mixtures that cannot be separated by conventional methods because they have azeotropes that prevent products from being obtained with the level of purity required for the different applications in which they are necessary. In this project, a study is realized on the acetonitrile-water mixture that is acquired as a by-product of acrylonitrile synthesis. In order to find an efficient method for obtaining acetonitrile (a compound of great importance in the pharmaceutical industry and as a solvent) different viable options are compared for separating mixtures with an azeotropic point, where the two most promising options in this case are pressure swing and extractive distillation which are design processes optimizing all the elements that make up the system through the ASPEN PLUS V12 simulator. Finally, different options to reduce the energy required by the different distillation columns and heat exchangers are analyzed as same as the costs and environmental impact of each of the simulations in order to discern which project would finally be the most suitable to be carried out

Implementació de la pila d'hidrogen als vehicles comercials

El futur de l'automoció depèn de les energies sostenibles. No es contempla un escenari sense el cotxe elèctric, però no necessàriament ha d'estar basat en vehicles amb grans bateries de liti que depenguin d'un endoll per funcionar. En aquest projecte s'exposa el paper de l'hidrogen com una font alternativa de combustible en el sector de l'automoció. S'han analitzat des de les seves propietats fins a la seva usabilitat actual a empreses líders del mercat. En primer lloc, l'estudi reflecteix les fonts actuals d'obtenció de l'hidrogen i la infraestructura necessària per assumir la migració de l'actual parc de combustió cap a aquesta nova font d'energia. Per altra banda, compta amb una comparació dels diferents tipus de pila de combustible, així com les possibles millores que es plantegen. El fet d'analitzat els prototips en els quals ja treballen les marques punteres de l'automoció ha sigut un factor clau per poder estudiar a fons l'aplicació de l'hidrogen en casos reals i exitosos. Per acabar, el projecte inclou un estudi pràctic de l'impacte ambiental de la implementació de la pila d'hidrogen als vehicles. Es contrasta amb l'observació de l'empremta de la resta de tecnologies del mercat, com el cotxe elèctric, híbrid o de combustió interna. L'objectiu d'aquest estudi és constatar la viabilitat de crear una infraestructura capaç de proveir als automòbils d'hidrogen verd, raó per la qual també s'ha elaborat l'anàlisi econòmica d'una hidrogenera a Barcelona. Així, ha estat possible estudiar el comportament del preu de l'hidrogen verd i els factors que comprèn una inversió d'aquestes característiques. Finalment, el projecte conclou, a través de les línies estudiades, amb els pros i contres de la pila d'hidrogen –respecte a altres energies– i la viabilitat d'aquesta a curt termini.El futuro de la automoción depende de las energías sostenibles. No se contempla un escenario sin el coche eléctrico, pero no necesariamente debe estar basado en vehículos con grandes baterías de litio que dependan de un enchufe para funcionar. En este proyecto se expone el papel del hidrógeno como fuente alternativa de combustible en el sector de la automoción. Se han analizado desde sus propiedades hasta su usabilidad actual en empresas líderes del mercado. En primer lugar, el estudio refleja las actuales fuentes de obtención del hidrógeno y la infraestructura necesaria para asumir la migración del actual parque de combustión hacia esta nueva fuente de energía. Por otra parte, cuenta con una comparación de los distintos tipos de pila de combustible, así como las posibles mejoras que se plantean. El hecho de analizar los prototipos en los que ya trabajan las marcas punteras de la automoción ha sido un factor clave para poder estudiar a fondo la aplicación del hidrógeno en casos reales y exitosos. Por último, el proyecto incluye un estudio práctico del impacto ambiental de la implementación de la pila de hidrógeno en los vehículos. Se contrasta con la observación de la impronta del resto de tecnologías del mercado, como el coche eléctrico, híbrido o de combustión interna. El objetivo de este estudio es constatar la viabilidad de crear una infraestructura capaz de abastecer a los automóviles de hidrógeno verde, por lo que también se ha elaborado el análisis económico de una hidrogenera en Barcelona. Así, ha sido posible estudiar el comportamiento del precio del hidrógeno verde y los factores que abarca una inversión de estas características. Por último, el proyecto concluye, a través de las líneas estudiadas, con los pros y contras de la pila de hidrógeno –respecto a otras energías– y la viabilidad de ésta a corto plazo.The future of the automotive industry depends on sustainable energy. A scenario is not contemplated without the electric car, but it does not necessarily have to be based on vehicles with large lithium batteries that depend on a plug to operate. This project discusses the role of hydrogen as an alternative source of fuel in the automotive sector. They have been analyzed from their properties to their current usability in market-leading companies. First, the study reflects current sources of hydrogen and the infrastructure needed to take on the migration of the current fuel park to this new energy source. On the other hand, it has a comparison of the different types of fuel cell, as well as the possible improvements that are proposed. Analyzing the prototypes in which the leading brands in the automotive industry are already working has been a key factor in being able to study in depth the application of hydrogen in real and successful cases. Finally, the project includes a practical study of the environmental impact of the implementation of the hydrogen battery in vehicles. It contrasts with the observation of the footprint of other technologies on the market, such as the electric, hybrid or internal combustion car. The aim of this study is to ascertain the feasibility of creating an infrastructure capable of supplying cars with green hydrogen, which is why the economic analysis of a hydrogen plant in Barcelona has also been carried out. Thus, it has been possible to study the behavior of the price of green hydrogen and the factors that comprise an investment of this nature. Finally, the project concludes, through the lines studied, with the pros and cons of the hydrogen battery - with respect to other energies - and its short-term viability

Quantitative Analysis of the Cervical Texture by Ultrasound and Correlation with Gestational Age

Objectives: Quantitative texture analysis has been proposed to extract robust features from the ultrasound image to detect subtle changes in the textures of the images. The aim of this study was to evaluate the feasibility of quantitative cervical texture analysis to assess cervical tissue changes throughout pregnancy. Methods: This was a cross-sectional study including singleton pregnancies between 20.0 and 41.6 weeks of gestation from women who delivered at term. Cervical length was measured, and a selected region of interest in the cervix was delineated. A model to predict gestational age based on features extracted from cervical images was developed following three steps: data splitting, feature transformation, and regression model computation. Results: Seven hundred images, 30 per gestational week, were included for analysis. There was a strong correlation between the gestational age at which the images were obtained and the estimated gestational age by quantitative analysis of the cervical texture (R = 0.88). Discussion: This study provides evidence that quantitative analysis of cervical texture can extract features from cervical ultrasound images which correlate with gestational age. Further research is needed to evaluate its applicability as a biomarker of the risk of spontaneous preterm birth, as well as its role in cervical assessment in other clinical situations in which cervical evaluation might be relevant

Neonatal Neurobehavior and Diffusion MRI Changes in Brain Reorganization Due to Intrauterine Growth Restriction in a Rabbit Model

Background: Intrauterine growth restriction (IUGR) affects 5–10 % of all newborns and is associated with a high risk of abnormal neurodevelopment. The timing and patterns of brain reorganization underlying IUGR are poorly documented. We developed a rabbit model of IUGR allowing neonatal neurobehavioral assessment and high resolution brain diffusion magnetic resonance imaging (MRI). The aim of the study was to describe the pattern and functional correlates of fetal brain reorganization induced by IUGR. Methodology/Principal Findings: IUGR was induced in 10 New Zealand fetal rabbits by ligation of 40–50 % of uteroplacental vessels in one horn at 25 days of gestation. Ten contralateral horn fetuses were used as controls. Cesarean section was performed at 30 days (term 31 days). At postnatal day +1, neonates were assessed by validated neurobehavioral tests including evaluation of tone, spontaneous locomotion, reflex motor activity, motor responses to olfactory stimuli, and coordination of suck and swallow. Subsequently, brains were collected and fixed and MRI was performed using a high resolution acquisition scheme. Global and regional (manual delineation and voxel based analysis) diffusion tensor imaging parameters were analyzed. IUGR was associated with significantly poorer neurobehavioral performance in most domains. Voxel based analysis revealed fractional anisotropy (FA) differences in multiple brain regions of gray and white matter, including frontal, insular, occipital and temporal cortex, hippocampus, putamen, thalamus, claustrum, medial septa

Structural coronary artery remodelling in the rabbit fetus as a result of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a fetal condition that affects up to 10% of all pregnancies and is associated with cardiovascular structural and functional remodelling that persists postnatally. Some studies have reported an increase in myocardial coronary blood flow in severe IUGR fetuses which has been directly associated to the dilatation of the coronary arteries. However, a direct measurement of the coronaries’ lumen diameter in IUGR has not been reported before. The aim of this paper is to perform, for the first time, a quantitative analysis of the effects of IUGR in cardiac geometry and coronary vessel size in a wellknown rabbit model of IUGR using synchrotron-based X-ray Phase Contrast Tomography Imaging (X-PCI). Eight rabbit fetal hearts were imaged non-destructively with X-PCI. 3D reconstructions of the coronary arterial tree were obtained after semi-automatic image segmentation. Different morphometric features including vessel lumen diameter of the three main coronaries were automatically quantified. IUGR fetuses had more globular hearts and dilated coronary arteries as compared to controls. We have quantitatively shown that IUGR leads to structural coronary vascular tree remodelling and enlargement as an adaptation mechanism in response to an adverse environment of restricted oxygen and nutrients and increased perfusion pressure

Quantitative ultrasound texture analysis of fetal lungs to predict neonatal respiratory morbidity

Objective To develop and evaluate the performance of a novel method for predicting neonatal respiratory morbidity based on quantitative analysis of the fetal lung by ultrasound. Methods More than 13¿000 non-clinical images and 900 fetal lung images were used to develop a computerized method based on texture analysis and machine learning algorithms, trained to predict neonatal respiratory morbidity risk on fetal lung ultrasound images. The method, termed ‘quantitative ultrasound fetal lung maturity analysis’ (quantusFLM™), was then validated blindly in 144 neonates, delivered at 28¿+¿0 to 39¿+¿0¿weeks' gestation. Lung ultrasound images in DICOM format were obtained within 48¿h of delivery and the ability of the software to predict neonatal respiratory morbidity, defined as either respiratory distress syndrome or transient tachypnea of the newborn, was determined. Results Mean (SD) gestational age at delivery was 36¿+¿1 (3¿+¿3) weeks. Among the 144 neonates, there were 29 (20.1%) cases of neonatal respiratory morbidity. Quantitative texture analysis predicted neonatal respiratory morbidity with a sensitivity, specificity, positive predictive value and negative predictive value of 86.2%, 87.0%, 62.5% and 96.2%, respectively. Conclusions Quantitative ultrasound fetal lung maturity analysis predicted neonatal respiratory morbidity with an accuracy comparable to that of current tests using amniotic fluid.Peer ReviewedPostprint (published version