检索结果-南通市图书馆

Multi-dimensional Simulation of Phase Change by a 0D-2D Model Coupling via Stefan Condition

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Communications on Applied Mathematics and Computation 2023年第2期5卷 853-884页

作者： Adrien Drouillet Romain Le Tellier Raphaël Loubère Mathieu Peybernes Louis Viot Institut de Mathématiques de bordeaux Universitéde Bordeaux33405 Talence CedexFrance CEA-deS-IRESNE-DTN CEA Cadarache13108 Saint Paul-lez-DuranceFrance

Considering phase changes associated with a high-temperature molten material cooled down from the outside,this work presents an improvement of the modelling and the numerical simulation of such processes for an application pertaining to the safety of light water nuclear reactors.Postulating a core meltdown accident,the behaviour of the core melt(aka corium)into a steel vessel is of tremendous importance when evaluating the vessel integrity.Evaluating correctly the heat fluxes requires the numerical simulation of the interaction between the liquid material and its solid counterpart which forms during the solidification process,but also may melt back.To simulate this configuration,encoun-tered in various industrial applications,one considers a bi-phase model constituted by a liquid phase in contact and interaction with its solid phase.The liquid phase may solidify in presence of low energetic source,while the solid phase may melt due to an intense heat flux from the high-temperature liquid.In the frame of the in-house legacy code,several simplifying assumptions(0D multi-layer discretization,instantaneous heat transfer via a quadratic temperature profile in solids)are made for the modelling of such phase changes.In the present work,these shortcomings are illustrated and further overcome by solving a 2D heat conduction model in the solid by a mixed Raviart-Thomas finite element method coupled to the liquid phase due to heat and mass exchanges through Stefan condition.The liquid phase is modeled with a 0D multi-layer approach.The 0D-liquid and 2D-solid mod-els are coupled by a Stefan like phase change interface model.Several sanity checks are performed to assess the validity of the approach on 1D and 2D academical configurations for which exact or reference solutions are available.Then more advanced situations(genu-ine multi-dimensional phase changes and an"industrial-like scenario")are simulated to verify the appropriate behavior of the obtained coupled simulation scheme.

关键词： Simulation of phase change Fusion Solidification 0D multi-layer model 2D heat conduction model Model coupling

A Posteriori Stabilized Sixth-Order Finite Volume Scheme with Adaptive Stencil Construction:Basics for the 1D Steady-State Hyperbolic Equations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications on Applied Mathematics and Computation 2023年第2期5卷 751-775页

作者： Gaspar J.Machado Stéphane Clain Raphaël Loubère Centre of Physics and department of Mathematics University of MinhoCampus of Azurém4800-058 GuimaraesPortugal CNRS and Institut de Mathématiques de bordeaux(IMB) Universitéde BordeauxTalenceFrance

We propose an adaptive stencil construction for high-order accurate finite volume schemes a posteriori stabilized devoted to solve one-dimensional steady-state hyperbolic equations.High accuracy(up to the sixth-order presently)is achieved,thanks to polynomial recon-structions while stability is provided with an a posteriori MOOD method which controls the cell polynomial degree for eliminating non-physical oscillations in the vicinity of dis-continuities.We supplemented this scheme with a stencil construction allowing to reduce even further the numerical dissipation.The stencil is shifted away from troubles(shocks,discontinuities,etc.)leading to less oscillating polynomial reconstructions.Experimented on linear,Burgers',and Euler equations,we demonstrate that the adaptive stencil technique manages to retrieve smooth solutions with optimal order of accuracy but also irregular ones without spurious oscillations.Moreover,we numerically show that the approach allows to reduce the dissipation still maintaining the essentially non-oscillatory behavior.

关键词： Finite volume MOOD Adaptive stencil Steady-state solution Euler equations High order

AP2/ERF transcription factors orchestrate very long chain fatty acid biosynthesis during Arabidopsis lateral root development

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Molecular Plant 2021年第2期14卷 205-207页

作者： Soazig Guyomarc'h Yohann Boutte Laurent Laplaze UMR DIAde Universitéde MontpellierIRDMontpellierFrance LBM BordeauxFrance

One key factor defining root system architecture is root branching,i.e.,the process of the formation of new root axes,called lateral roots(LRs),from an existing root.In the model plant Arabidopsis thaliana,LRs originate from preselected pericycle cells that divide to create an LR primordium(LRP)that grows and eventually forms a new root apical meristem(Banda et al.,2019).During this developmental process,cell-fate acquisition is very plastic and depends on positional information rather than on cell lineage(Banda et al.,2019).Importantly,LR formation occurs inside the parent root,and the LRP must grow through overlying tissues before emerging into the soil.This LR emergence process is controlled by dynamic intercellular signaling and involves a tight coordination of cellular responses in the LRP and surrounding tissues(Banda et al.,2019).In particular,the growing LRP rapidly pushes against the overlying endodermis,a layer of cells mechanically reinforced by the Casparian strip.The crossing of the endodermis by the LRP between stagesⅣand V has been proposed as an important developmental checkpoint during LR development(Banda et al.,2019).

关键词： eventually Arabidopsis branching

INVARIANCE AND STABILITY OF THE PROFILE EQUATIONS OF GEOMETRIC OPTICS

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2011年第6期31卷 2141-2158页

作者： Guy Mtivier Jeffrey Rauch Institut de Mathmatiques de bordeaux Universit de Bordeaux department of Mathematics University of Michigan

The profile equations of geometric optics are described in a form invariant under the natural transformations of first order systems of partial differential equations. This allows us to prove that various strategies for computing profile equations are equivalent. We prove that if L generates an evolution on L2 the same is true of the profile equations. We prove that the characteristic polynomial of the profile equations is the localization of the characteristic polynomial of the background operator at （y, dφ（y）） where φ is the background phase. We prove that the propagation cones of the profile equations are subsets of the propagation cones of the background operator.

关键词： geometric optics profile equation localisation vector bundles propagation cones

Percolation of carbon nanomaterials for high-k polymer nanocomposites

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2017年第11期28卷 2036-2044页

作者： Jinkai Yuan Centre de Recherche Paul Pascal CNRS Université de Bordeaux Pessac 33600 France

High-k polymer composite materials are next-generation dielectrics that show amazing applications in diverse electrical and electronic devices. Establishing near-percolated network of conducting filler in an insulating polymer matrix is a promising approach to develop flexible high-k dielectrics. However, challenges still exist today on fine controlling the network morphology to achieve extremely high k values and low losses simultaneously. The relationship between the network morphology and the dielectric properties of polymer composites is raising a number of fundamental questions. Herein, recent progress towards high-k polymer composites based on carbon nanomaterials is reviewed. Particular attention is paid on the influence of the network morphology on the dielectric properties. Some perspectives that warrant further investigation in the future are also addressed.

关键词： Percolation Carbon nanomaterials Polymer composites Dielectric constant Permittivity

Soil and vegetation water content identify the main terrestrial ecosystem changes

在线全文

学校读者我要写书评

暂无评论

National Science Review 2023年第5期10卷 167-179页

作者： Diego Bueso Maria Piles Philippe Ciais Jean-Pierre Wigneron álvaro Moreno-Martínez Gustau Camps-Valls Image Processing Laboratory Universitat de València Laboratoire des Sciences du Climat et de l'Environnement université Paris Saclay INRA Centre de bordeaux Aquitaine Image Processing Laboratory Universitat deValència

Environmental change is a consequence of many interrelated factors.How vegetation responds to natural and human activity still needs to be well establishe d,quantified and understood.Re cent satellite missions providing hydrologic and ecological indicators enable better monitoring of Earth system changes,yet there is no automatic way to address this issue directly from observations.Here,we develop an observation-based methodology to capture evidence of changes in global terrestrial ecosystems and attribute these changes to natural or anthropogenic activity.We use the longest time record of global microwave L-band soil moisture and vegetation optical depth as satellite data and build spatially explicit maps of change in soil and vegetation water content and biomass reflecting large ecosystem changes during the last decade,2010-20.Regions of prominent trends(from-8% to 9% per year) are observed,especially in humid and semi-arid climates.We further combine such trends with land cover change maps,vegetation greenness and precipitation variability to assess their relationship with major documented ecosystem changes.Several regions emerge from our results.They cluster changes according to human activity drivers,including deforestation(Amazon,Central Africa) and wildfires(East Australia),artificial reforestation(South-East China),abandonment of farm fields(Central Russia) and climate shifts related to changes in precipitation variability(East Africa,North America and Central Argentina).Using the high sensitivity of soil and vegetation water content to ecosystem changes,microwave satellite observations enable us to quantify and attribute global vegetation responses to climate or anthropogenic activities as a direct measure of environmental changes and the mechanisms driving them.

关键词： soil moisture vegetation water content ecosystem trend remote sensing soil moisture and ocean salinity satellite

Dynamics of a rigid body in a two-dimensional incompressible perfect fluid and the zero-radius limit dedicated to Professor Jean-Yves Chemin on the Occasion of His 60th Birthday

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2019年第6期62卷 1205-1218页

作者： Franck Sueur Institut de Mathématiques de bordeaux CNRS UMR 5251 Université de Bordeaux

In this survey we report some recent results on the dynamics of a rigid body immersed in a twodimensional incompressible perfect fluid, with an emphasis on the zero-radius limit.

关键词： fluid-structure interaction point vortex perfect incompressible fluid

Sexual audience affects male's reproduction investment without consequences on reproductive outputs

在线全文

学校读者我要写书评

暂无评论

Insect Science 2022年第4期29卷 1170-1180页

作者： Philippe Louâpre Karen Muller Soline Bettencourt-Amarante denis Thiery Jérôme Moreau UMR CNRS 6282 Biogeosciences UniversitéBourgogne Franche-ComtéDijonFrance INRA UMR 1065 Santéet Agroecologie du Vignoble Institut des Science de la Vigne et du VinVillenave d'OrnonCedexFrance INRA UMR 1065 SaveUniversitéde BordeauxBordeaux Sciences AgroVillenave d'OrnonCedexFrance

Males evolved plastic strategies to respond to male-male competition and exhibit adaptive traits and behaviors maximizing their access to the females and limiting sperm competition.Mating behaviors allow males to express quick responses to current sexual audience,that is,the number of nearby conspecifics prone to mate.In contrast,physiological responses are frequently delayed because they are constrained by the time and resources having to be mobilized to produce and export sperm and associated products.This is especially critical in species for which males produce spermatophores.Here we investigated in what extend moth males(the tortricid moth Lobesia botrana)producing spermatophores exhibit plastic behavioral and physiological responses to different sexual audiences before and during mating and the consequences for their reproductive output.We found that males adjusted their mating behaviors and spermatophore size to a potentially elevated risk of sperm competition perceived before mating.In addition,males responded to the closed presence of females during mating by reducing their mating duration.Surprisingly,the various behavioral and physiological responses we highlighted here were not fully reflected in their reproductive performance as we did not reveal any effect on fecundity and fertility of their mate.The selective pressure exerted on males experiencing male-male competition could thus be sufficient to trigger adjustment in male mating behaviors but constrains physiological responses according to the perception of competition.

关键词： Lobesia borrund male-male compeition mating behavior sexual conflict sexual scletion sperm competition

Magnetic resonance imaging under isoflurane anesthesia alters cortical cyclooxygenase-2 expression and glial cell morphology during sepsis-associated neurological dysfunction in rats

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Animal Models and Experimental Medicine 2021年第3期4卷 249-260页

作者： Ibtihel Dhaya Marion Griton Jan Pieter Konsman INCIA Institut de Neurosciences Cognitives et Intégratives d'AquitaineCNRS UMR 5287BordeauxFrance Univ.bordeaux INCIAUMR 5287BordeauxFrance Laboratoire de Neurophysiologie Fonctionnelle et Pathologies UR/11ES09Facultédes Sciences MathématiquesPhysiques et NaturellesUniversitéde Tunis El ManarTunisTunisie Service de Réanimation Anesthésie Neurochirurgicale Centre Hospitalier Universitaire(CHU)de BordeauxBordeauxFrance

Background:Magnetic resonance imaging(MRI)of rodents combined with histol-ogy allows to determine what mechanisms underlie functional and structural brain changes during sepsis-associated encephalopathy.However,the effects of MRI per-formed in isoflurane-anesthetized rodents on modifications of the blood-brain bar-rier and the production of vasoactive prostaglandins and glia cells,which have been proposed to mediate sepsis-associated brain dysfunction,are unknown.Methods:This study addressed the effect of MRI under isoflurane anesthesia on blood-brain barrier integrity,cyclooxygenase-2 expression,and glial cell activation during cecal ligature and puncture-induced sepsis-associated brain dysfunction in rats.Results:Cecal ligature and puncture reduced food intake and the righting reflex.MRI under isoflurane anesthesia reduced blood-brain barrier breakdown,decreased cir-cularity of white matter astrocytes,and increased neuronal cyclooxygenase-2 immu-noreactivity in the cortex 24 hours after laparotomy.In addition,it annihilated cecal ligature and puncture-induced increased circularity of white matter microglia.MRI under isoflurane anesthesia,however,did not alter sepsis-associated perivascular cyclooxygenase-2 induction.Conclusion:These findings indicate that MRI under isoflurane anesthesia of rodents can modify neurovascular and glial responses and should,therefore,be interpreted with caution.

关键词： anesthesia astrocyte blood-brain barrier magnetic resonance imaging microglia sepsis