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High-Order Schemes Combining the Modified Equation Approach and Discontinuous Galerkin Approximations for the Wave Equation

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Communications in Computational Physics 2012年第2期11卷 691-708页

作者： Cyril Agut julien Diaz Abdelaaziz Ezziani LMA CNRS UMR 5142Universite de PauFrance INRIA Bordeaux Research Center Project Team Magique3DFrance

We present a new high ordermethod in space and time for solving the wave equation,based on a newinterpretation of the“Modified Equation”***,contrary to most of the works,we consider the time discretization before the space *** the time discretization,an additional biharmonic operator appears,which can not be discretized by classical finite *** propose a new Discontinuous Galerkinmethod for the discretization of this operator,andwe provide numerical experiments proving that the new method is more accurate than the classicalModified Equation technique with a lower computational burden.

关键词： High order schemes discontinuous Galerkin method acoustic wave equation

Impact of Varying Blower Opening Degrees on Indoor Environment and Thermal Comfort

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Fluid Dynamics & Materials Processing 2024年第8期20卷 1703-1716页

作者： Shengqiang Shi Abdelatif Merabtine Rachid Bennacer julien Kauffmann UR LASMIS Universitéde Technologie de Troyes12 Rue Marie CurieTroyes10300France EPF Campus de Troyes Rosière-prés-Troyes10430France Construction Engineering Department École de Technologie Supérieure(ÉTS)University of Québec1100 Rue Notre-Dame OuestMontrealQC H3C 1K3Canada LMT/ENS-Paris-Saclay/CNRS UniversitéParis SaclayGif-sur-Yvette91190France

At present,air handling units are usually used indoors to improve the indoor environment ***,while introducing fresh air to improve air quality,air velocity has a certain impact on the occupants’thermal ***,it is necessary to explore the optimization of air-fluid-body interaction *** this study,the indoor air flow was changed by changing the opening and closing degree of the blower,and the thermal manikin is introduced to objectively evaluate the human thermal comfort under different air *** main experimental results show that the air change rate increases with the increase of the opening and closing degree of the blower considering an ACH(air changes per hour)range between 3.8 and *** a better prediction,a linear correlation with a coefficient of 0.995 is *** the blower’s opening is adjusted to 20%,25%,30%,35%,and 40%,the air velocity sensor positioned directly beneath the air inlet records average velocities of 0.19,0.20,0.21,0.28,and 0.34 m/s over four hours,*** on thermal comfort and the average sensation experienced by individuals indicate an initial increase followed by a decline when the blower’s operation begins,with optimal conditions achieved at a 35%*** findings offer valuable insights for future indoor air ventilation and heat transfer design strategies.

关键词： Air handle unit air velocity thermal comfort thermal sensation

Micro-Differential Boundary Conditions Modelling the Absorption of Acoustic Waves by 2D Arbitrarily-Shaped Convex Surfaces

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Communications in Computational Physics 2012年第2期11卷 674-690页

作者： Helene Barucq julien Diaz Veronique Duprat INRIA Bordeaux-Sud Ouest Team-project MAGIQUE-3D LMA CNRS UMR 5142University of PauFrance

We propose a new Absorbing Boundary Condition(ABC)for the acoustic wave equation which is derived from a micro-local diagonalization process formerly defined by *** and which does not depend on the geometry of the surface bearing the *** considering the principal symbol of the wave equation both in the hyperbolic and the elliptic regions,we show that a second-order ABC can be constructed as the combination of an existing first-order ABC and a Fourier-Robin *** compare the new ABC with other ABCs and we show that it performs well in simple configurations and that it improves the accuracy of the numerical solution without increasing the computational burden.

关键词： Wave equation micro-local diagonalization absorbing boundary condition finite element formulation

A high-order SPH method by introducing inverse kernels

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Chinese Journal of Aeronautics 2017年第1期30卷 1-14页

作者： Fang Le Marongiu Jean Christophe Leduc julien Amicarelli Andrea Caro Joёlleb LMP Ecole centrale de Pekin Beihang University Co-Innovation Center for Advanced Aero-Engine 100083 Beijing China LMFA Ecole centrale de Lyon 69130 Ecully BP 163 France Laboratoire International Associe Beihang University 100083 Beijing China ANDRITZ HYDRO AG Rue des Deux-Gares 6 1800 Vevey Switzerland

The smoothed particle hydrodynamics（SPH） method is usually expected to be an efficient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by introducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square（LS） and Moving-Least-Square（MLS） methods. Then detailed analysis in spectral space is presented for people to better understand this method. Finally we show three test examples to verify the method behavior.

关键词： Consistency High-order method Inverse method Numerical dissipation Numerical instability Smoothed particle hydrodynamics

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Sediment load calculations from point measurements in sand-bed rivers

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International Journal of Sediment Research 2015年第1期30卷 1-12页

作者： Seema C.SHAH-FAIRBANK Pierre Y julien Department of Civil Engineering California State Polytechnic University Department of Civil and Environmental Engineering Colorado State University

Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed *** with the Series Expansion of the Modified Einstein Point Procedure（SEMEPP） depend on grain diameter d;and settling velocity ω,flow depth h,shear velocity u*,and sampling depth h;.This procedure extends the applicability of the Modified Einstein Procedure（MEP） by using point sediment concentration and velocity *** procedure is tested using the laboratory data from Coleman,and field measurements from the Enoree,Middle Rio Grande and Mississippi *** on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L;,the accuracy of the calculations depends on u*/ω and h;/d;.Point measurement techniques like SEMEPP are well-suited when u*/ω> 5 where at least 60%of the total sediment load is measured when 90%of the flow depth is *** determination of sediment discharge from point measurements is most accurate in deep rivers when h;/d;> *** u*/ω>*** measurements are not well-suited for shallow rivers and laboratory flumes where h< 0.5 m and when u*/ω< 2.

关键词： Point measurements Concentration profiles Velocity profiles Total sediment load Modified Einstein Procedure

Estimating Compositions and Nutritional Values of Seed Mixes Based on Vision Transformers

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Plant Phenomics 2023年第4期5卷 805-815页

作者： Shamprikta Mehreen Hervé Goëau Pierre Bonnet Sophie Chau julien Champ Alexis Joly Inria LIRMMUniversity MontpellierCNRSMontpellierFrance CIRAD UMR AMAPMontpellierOccitanieFrance Chambre d'Agriculture-Haute Vienne LimogesNouvelle-AquitaineFrance

The cultivation of seed mixtures for local pastures is a traditional mixed cropping technique of cereals and legumes for producing,at a low production cost,a balanced animal feed in energy and protein in livestock *** considerably improving the autonomy and safety of agricultural systems,as well as reducing their impact on the environment,it is a type of crop that responds favorably to both the evolution of the European regulations on the use of phytosanitary products and the expectations of consumers who wish to increase their consumption of organic ***,farmers find it difficult to adopt it because cereals and legumes do not ripen synchronously and the harvested seeds are heterogeneous,making it more difficult to assess their nutritional *** efforts therefore remain to be made to acquire and aggregate technical and economical references to evaluate to what extent the cultivation of seed mixtures could positively contribute to securing and reducing the costs of herd *** work presented in this paper proposes new Artificial Intelligence techniques that could be transferred to an online or smartphone application to automatically estimate the nutritional value of harvested seed mixes to help farmers better manage the yield and thus engage them to promote and contribute to a better knowledge of this type of *** this purpose,an original open image dataset has been built containing 4,749 images of seed mixes,covering 11 seed varieties,with which 2 types of recent deep learning models have been *** results highlight the potential of this method and show that the best-performing model is a recent state-of-the-art vision transformer pre-trained with self-supervision(Bidirectional Encoder representation from Image Transformer).It allows an estimation of the nutritional value of seed mixtures with a coefficient of determination R^(2)score of 0.91,which demonstrates the interest of this type of approach,for its possible use

关键词： transferred cultivation harvest

A simple model for COVID-19

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Infectious Disease Modelling 2020年第1期5卷 309-315页

作者： julien Arino Stéphanie Portet Department of Mathematics&Data Science NEXUS University of ManitobaCanada Centre for Disease Modelling Canada Canadian COVID-19 Mathematical Modelling Task Force Canada

An SL1L2I1I2A1A2R epidemic model is formulated that describes the spread of an epidemic in a *** model incorporates an Erlang distribution of times of sojourn in incubating,symptomatically and asymptomatically infectious *** properties of the model are explored,with focus on properties important in the context of current COVID-19 pandemic.

关键词： COVID-19 Mathematical model Erlang distribution Asymptomatic infections

A visual analytics workflow for probabilistic modeling

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Visual Informatics 2023年第2期7卷 72-84页

作者： julien Klaus Mark Blacher Andreas Goral Philipp Lucas Joachim Giesen Friedrich Schiller University Jena Germany

Probabilistic programming is a powerful means for formally specifying machine learning *** inference engine of a probabilistic programming environment can be used for serving complex queries on these *** of the current research in probabilistic programming is dedicated to the design and implementation of highly efficient inference *** less research aims at making the power of these inference engines accessible to non-expert *** programming means writing *** many potential users from promising application areas such as the social sciences lack programming *** prompted recent efforts in synthesizing probabilistic programs directly from ***,working with synthesized programs still requires the user to read,understand,and write some code,for instance,when invoking the inference engine for answering ***,we present an interactive visual approach to synthesizing and querying probabilistic programs that does not require the user to read or write code.

关键词： Probabilistic inference Bayesian network Structured query language Table-based visualization

Variation in mantle lithology and composition beneath the Ngao Bilta volcano,Adamawa Massif,Cameroon volcanic line,West-central Africa

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Geoscience Frontiers 2020年第2期11卷 665-677页

作者： Robert Temdjim Merlin Patrick Njombie Wagsong Arnold julien Nzakou Tsepeng Stephen Foley Department of Earth Sciences Faculty of SciencesUniversity of Yaounde IP.O.Box.812 YaoundeCameroon Department of Earth and Planetary Sciences and ARC Centre of Excellence for Core to Crust Fluid Systems Macquarie UniversityNorth RydeNSW2109Australia

Mantle peridotites entrained as xenoliths in the lavas of Ngao Bilta in the eastern branch of the continental Cameroon Line were examined to constrain mantle processes and the origin and nature of melts that have modified the upper mantle beneath the Cameroon *** xenoliths consist mainly of lherzolite with subordinate harzburgite and *** commonly contain olivine,orthopyroxene,clinopyroxene and spinel although the dunite is *** is an essential constituent in the *** chemistry differs between the three types of peridotite:olivines have usual mantle-like Mg#of around 90 in lherzolites,but follow a trend of decreasing Mg#(to 82)and NiO(to 0.06 wt.%)that is continuous in the *** also contain orthopyroxenes and/or clinopyroxenes with low-Mg#,indicating a reaction that removes Opx and introduces Cpx,olivine,amphibole and *** is attributed to reaction with a silica-undersaturated silicate melt such as nephelinite or basanite,which originated as a low-degree melt from a depleted source as indicated by low Al2O3 and Na2O in Cpx and high Na2O/K2O in *** estimates place the xenoliths at pressures of 11–15 kbar(35–50 km)and temperatures of 863–957C,along a dynamic rift geotherm and shallower than the region where carbonate melts may *** melt/rock reactions exhibited by the Ngao Bilta xenoliths are consistent with their peripheral position in the eastern branch of the Cameroon Volcanic Line in an area of thinned crust and lithosphere beneath the Adamawa Uplift.

关键词： Cameroon volcanic line Adamawa volcanic massif Peridotite xenoliths Partial melting Melt-rock reactions

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