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In-situ diagnostic of femtosecond laser probe pulses for high resolution ultrafast imaging

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Light(Science & Applications) 2021年第7期10卷 1326-1338页

作者： Chen Xie remi Meyer Luc Froehly Remo Giust Francois Courvoisier Ultrafast Laser Laboratory Key Laboratory of Opto-electronic Information Technology of Ministry of EducationSchool of Precision Instruments and Opto-electronics EngineeringTianjin University300072 TianjinChina FEMTO-ST Institute Univ.Bourgogne Franche-ComtéCNRS15B avenue des Montboucons25030 Besançon CedexFrance

Ultrafast imaging is essential in physics and chemistry to investigate the femtosecond dynamics of nonuniform samples or of phenomena with strong spatial *** relies on observing the phenomena induced by an ultrashort laser pump pulse using an ultrashort probe pulse at a later *** years have seen the emergence of very successful ultrafast imaging techniques of single non-reproducible events with extremely high frame rate,based on wavelength or spatial frequency ***,further progress in ultrafast imaging towards high spatial resolution is hampered by the lack of characterization of weak probe *** pump–probe experiments realized within solids or liquids,because of the difference in group velocities between pump and probe,the determination of the absolute pump–probe delay depends on the sample *** addition,pulse-front tilt is a widespread issue,unacceptable for ultrafast imaging,but which is conventionally very difficult to evaluate for the low-intensity probe *** we show that a pump-induced micro-grating generated from the electronic Kerr effect provides a detailed in-situ characterization of a weak probe *** allows solving the two issues of absolute pump–probe delay determination and pulse-front tilt *** approach is valid whatever the transparent medium with nonnegligible Kerr index,whatever the probe pulse polarization and *** it is nondestructive and fast to perform,this in-situ probe diagnostic can be repeated to calibrate experimental conditions,particularly in the case where complex wavelength,spatial frequency or polarization encoding is *** anticipate that this technique will enable previously inaccessible spatiotemporal imaging in a number of fields of ultrafast science at the micro-and nanoscale.

关键词： pump polarization laser

Development of Residual Distribution Schemes for the Discontinuous Galerkin Method:The Scalar Case with Linear Elements

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Communications in Computational Physics 2009年第2期5卷 376-390页

作者： remi Abgrall Chi-Wang Shu Institut de Mathematiques and INRIA Universite Bordeaux I341 cours de la Liberation33405 Talence cedexFrance Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA

In this paper,we reformulate the piecewise linear discontinuous Galerkin(DG)method for solving two dimensional steady state scalar conservation laws in the framework of residual distribution(RD)*** allows us to propose a new class of nonlinear stabilization that does not destroy the formal accuracy of the *** results are shown to demonstrate the behavior of this approach.

关键词： Discontinuous Galerkin schemes residual distribution schemes high order unstructured meshes

A Nominally Second-Order Cell-Centered Finite Volume Scheme for Simulating Three-Dimensional Anisotropic Diffusion Equations on Unstructured Grids

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Communications in Computational Physics 2014年第9期16卷 841-891页

作者： Pascal Jacq Pierre-Henri Maire remi Abgrall CEA/CESTA 15 Avenue des Sablieres CS 6000133116 Le Barp cedexFrance. Institut fur Mathematik Universitat ZurichCH-8057 ZurichSwitzerland.

We present a finite volume based cell-centered method for solving diffusion equations on three-dimensional unstructured grids with general tensor *** main motivation concerns the numerical simulation of the coupling between fluid flows and heat *** corresponding numerical scheme is characterized by cell-centered unknowns and a local ***,the scheme results in a global sparse diffusion matrix,which couples only the cell-centered *** space discretization relies on the partition of polyhedral cells into sub-cells and on the partition of cell faces into *** is characterized by the introduction of sub-face normal fluxes and sub-face temperatures,which are auxiliary unknowns.A sub-cellbased variational formulation of the constitutive Fourier law allows to construct an explicit approximation of the sub-face normal heat fluxes in terms of the cell-centered temperature and the adjacent sub-face *** elimination of the sub-face temperatures with respect to the cell-centered temperatures is achieved locally at each node by solving a small and sparse linear *** system is obtained by enforcing the continuity condition of the normal heat flux across each sub-cell interface impinging at the node under *** parallel implementation of the numerical algorithm and its efficiency are described and *** accuracy and the robustness of the proposed finite volume method are assessed by means of various numerical test cases.

关键词： Finite volume methods unstructured grids anisotropic diffusion parallel computing

Inferring topological transitions in pattern-forming processes with self-supervised learning

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npj Computational Materials 2022年第1期8卷 1970-1981页

作者： Marcin Abram Keith Burghardt Greg Ver Steeg Aram Galstyan remi Dingreville Department of Physics and Astronomy University of Southern CaliforniaLos AngelesCA90089USA Information Sciences Institute University of Southern CaliforniaMarina del ReyCA90292USA Center for Integrated Nanotechnologies Nanostructure Physics DepartmentSandia National LaboratoriesAlbuquerqueNM87185USA

The identification of transitions in pattern-forming processes are critical to understand and fabricate microstructurally precise materials in many application *** supervised methods can be useful to identify transition regimes,they need labels,which require prior knowledge of order parameters or relevant microstructures describing these ***,we develop a self-supervised,neural-network-based approach that does not require predefined labels about microstructure classes to predict process parameters from observed *** show that assessing the difficulty of solving this inverse problem can be used to uncover microstructural *** demonstrate our approach by automatically discovering microstructural transitions in two distinct pattern-forming processes:the spinodal decomposition of a two-phase mixture and the formation of binary-alloy microstructures during physical vapor deposition of thin *** approach opens a path forward for discovering unseen or hard-to-discern transitions and ultimately controlling complex pattern-forming processes.

关键词： alloy microstructure transitions

Quadratic mean-field reflected BSDEs

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Probability, Uncertainty and Quantitative Risk 2022年第3期7卷 169-194页

作者： Ying Hu remi Moreau Falei Wang CNRS IRMAR-UMR 6625Univ.RennesF-35000RennesFrance School of Mathematical Sciences Fudan UniversityShanghai 200433China Zhongtai Securities Institute for Financial Studies Shandong UniversityJinan 250100China School of Mathematics Shandong UniversityJinan 250100China

In this paper,we analyze mean-field reflected backward stochastic differential equations when the driver has quadratic growth in the second unknown *** a linearization technique and the BMO martingale theory,we first apply a fixed-point argument to establish the uniqueness and existence result for the case with bounded terminal condition and ***,with the help of theθ-method,we develop a successive approximation procedure to remove the boundedness condition on the terminal condition and obstacle when the generator is concave(or convex)with respect to the second unknown.

关键词： Mean-field Reflected BSDEs Linearization technique θ-method

Cryptic diversity within three South American whip spider species(Arachnida, Amblypygi)

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Zoological Research 2020年第5期41卷 595-598页

作者： Florian Reveillion remi Wattier Sophie Montuire Leonardo Sousa Carvalho Loic Bollache Universite de Bourgogne Franche Comte Dijon 21000France Laboratoire Chrono-Environnement UMR CNRS 6249Universite de Bourgogne Franche-ComteBesangon Cedex 25030France Laboratoire Biogeosciences UMR CNRS 6282Universite de Bourgogne Franche-ComteDijon 21000France EPHE PSL UniversityParis 75014France Universidade Federal do Piaui Campus Amilcar Ferreira SobralFlorianoPiaui 64800-606Brazil

DEAR EDITOR,Cryptic diversity(CD),the presence of highly divergent phylogenetic lineages within closed morphological species,has been documented for many *** arachnid orders such as Araneae or Scorpiones are well studied and many cases of CD have been described therein;to date,however,related research on smaller arachnid orders,such as whip spiders(Amblypygi),remains lacking.

关键词： Cry whip Great

Phosphine-phosphonium ylides as ligands in palladium-catalysed C2-H arylation of benzoxazoles

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Chinese Chemical Letters 2020年第12期31卷 3250-3254页

作者： Zhenyu Yao Xing Lin remi Chauvin Lianhui Wang Emmanuel Gras Xiuling Cui Engineering Research Centre of Molecular Medicine of Ministry of Education Key Laboratory of Fujian Molecular MedicineKey Laboratory of Precision Medicine and Molecular Diagnosis of Fujian UniversitiesKey Laboratory of Xiamen Marine and Gene DrugsSchool of Biomedical SciencesHuaqiao UniversityXiamen 361021China Laboratory of Coordination Chemistry(LCC) CNRS&Universite'de Toulouse(UPSINP)Toulouse 31077 Cedex 4France

As balanced electron-rich P,C-chelating ligands,phosphine-phosphonium-ylides are considered for their ability to in situ promote palladium-catalysed direct C(sp^2)—H *** methyl phosphonium salts of 2,2’-bis(diphenylphosphino)-1,1’-binaphtyl("methyl-BINAPIUM")as ylide precursors under optimized reaction conditions,arylation of benzoxazole was found to proceed in moderate to high yield to give functional 2-aryl benzoxazoles.A strong anion effect of the non-salt free ylide was evidenced(TfO^->I^->PF6^-≈salt-free).This first example of phosphonium ylides as ligands in catalytic C-H activation extends the prospect of their general implementation in homogeneous transition metal catalysis.

关键词： Electron-rich Ligands Phosphine-phosphonium-ylides Benzixazole C-H activation

Capturing Near-Equilibrium Solutions: A Comparison between High-Order Discontinuous Galerkin Methods and Well-Balanced Schemes

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Communications in Computational Physics 2019年第6期26卷 1-34页

作者： Maria Han Veiga David A.Velasco-Romero remi Abgrall Romain Teyssier Institute of Computational Science University of ZurichSwitzerland Institute of Mathematics University of ZurichSwitzerland Universidad Autonoma del Estado de Morelos Mexico Instituto de Ciencias Fisicas Universidad Nacional Aut́onoma de ḾexicoMexico

Equilibrium or stationary solutions usually proceed through the exact balance between hyperbolic transport terms and source terms. Such equilibrium solutions are affected by truncation errors that prevent any classical numerical scheme from capturing the evolution of small amplitude waves of physical significance. In order to overcome this problem, we compare two commonly adopted strategies: going to very high order and reduce drastically the truncation errors on the equilibrium solution, or design a specific scheme that preserves by construction the equilibrium exactly, the so-called well-balanced approach. We present a modern numerical implementation of these two strategies and compare them in details, using hydrostatic but also dynamical equilibrium solutions of several simple test cases. Finally, we apply our methodology to the simulation of a protoplanetary disc in centrifugal equilibrium around its star and model its interaction with an embedded planet, illustrating in a realistic application the strength of both methods.

关键词： Numerical methods benchmark well-balanced methods discontinuous Galerkin methods

Versatile synthesis of cadalene and iso-cadalene from himachalene mixtures:Evidence and application of unprecedented rearrangements

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Chinese Chemical Letters 2020年第7期31卷 1851-1854页

作者： Mustapha Ait El Had Abdelouahd Oukhrib Mohamed Zaki Martine Urrutigoity Ahmed Benharref remi Chauvin Laboratoire de Chimie Biomoleculaire Substances Naturelies et Reactivite(URAC 16)Faculte des Sciences SemlaliaUniversite Cadi AyyadB.P.2390MarrakechMorocco CNRS LCC(Laboratoire de Chimie de Coordination)BP 4409931077Toulouse Cedex 4France INP-ENSIACET 4 allee Emile Monso31030Toulouse CedexFrance Universite de Toulouse UPSICT-FR 259931062Toulouse Cedex 9France

From a mixture of α-,β-and y-himachalenes extracted from waste wood of Atlas cedar(Cedrus atlantica),cadalene(1,6-dimethyl-4-isopropylnaphthalene)and iso-cadalene(1,6-dimethyl-3-isopropylnaphthalene)were produced in two steps with up to 71%±5%yield through the ar-himachalene intermediate using I2 and/or AlCl3 as *** selectivity is shown to sharply depend on the operating conditions:while I2/AlCl3 in dichloromethane promotes the formation of cadalene,the formation of iso-cadalene is favored in the presence of AlCl3 in *** bicyclic aromatic compounds were thus obtained through unique rearrangements involving sequential C—C bond cleavage/fo rmation and hydride transfer *** the absence of AlCl3 or I2,dihydrocurcumene was also found to be formed with up to 70%selectivity.A tentative mechanism is proposed and discussed.

关键词： Aromatic reactivity Cadalenes Dihydrocurcumene Himachalenes Rearrangements