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REGULARIZATION METHODS FOR THE NUMERICAL SOLUTION OF THE DIVERGENCE EQUATION △. u = f＊

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Journal of Computational Mathematics 2012年第4期30卷 354-380页

作者： alexandre Caboussat Roland Glowinski University of Houston Department of Mathematics Houston Texas USA

The problem of finding a L^∞-bounded two-dimensional vector field whose divergence is given in L2 is discussed from the numerical viewpoint. A systematic way to find such a vector field is to introduce a non-smooth variational problem involving a L^∞-norm. To solve this problem from calculus of variations, we use a method relying on a well- chosen augmented Lagrangian functional and on a mixed finite element approximation. An Uzawa algorithm allows to decouple the differential operators from the nonlinearities introduced by the L^∞-norm, and leads to the solution of a sequence of Stokes-like systems and of an infinite family of local nonlinear problems. A simpler method, based on a L2- regularization is also considered. Numerical experiments are performed, making use of appropriate numerical integration techniques when non-smooth data are considered; they allow to compare the merits of the two approaches discussed in this article and to show the ability of the related methods at capturing L^∞bounded solutions.

关键词： Divergence equation Bounded solutions Regularization methods AugmentedLagrangian Uzawa algorithm Nonlinear variational problems.

A Pseudo-Kinetic Approach for Helmholtz Equation

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Chinese Annals of Mathematics,Series B 2013年第3期34卷 319-332页

作者： Radjesvarane alexandre Jie LIAO Department of Mathematics Shanghai Jiao Tong University IRENAV Research Institute French Naval AcademyBrest-Lanvoc 29290 France School of Science East China University of Science and Technology

A lattice Boltzmann type pseudo-kinetic model for a non-homogeneous Helmholtz equation is derived in this paper. NumericM results for some model problems show the robustness and efficiency of this lattice Boltzmann type pseudo-kinetic scheme. The computation at each site is determined only by local parameters, and can be easily adapted to solve multiple scattering problems with many scatterers or wave propagation in nonhomogeneous medium without increasing the computational cost.

关键词： Lattice Boltzmann scheme Non-homogeneous Helmholtz equation Discrete velocity

Effects of Andrade and Burgers rheologies on glacial isostatic adjustment modeling in Antarctica

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Geodesy and Geodynamics 2024年第5期15卷 429-440页

作者： alexandre Boughanemi Anthony Mémin UniversitéCôte d'Azur CNRSObservatoire de la Côte d'AzurIRDGéoazur250 rue Albert EinsteinSophia Antipolis 06560 ValbonneFrance

Variations in ice mass deform the Earth and modify its gravity field,a process known as Glacial Isostatic Adjustment(GIA).GIA in Antarctica remains poorly constrained due to the cumulative effect of past and present ice-mass changes,the unknown history of the past ice-mass change,and the uncertainties on the mechanical properties of the *** paper investigates the effect of using Andrade and Burgers viscoelastic rheologies,rather than the commonly used Maxwell rheology,to model GIA-induced deformation in *** Love number and Green's function formalism are used to compute the radial surface displacements and the gravity changes induced by the past and present ice-mass *** consider an Earth model whose elastic properties and radial structure are averaged from the Preliminary Reference Earth Model and two viscosity profiles to account for the recently published results on the present ice-mass *** the three rheological laws affects the temporal response of the Earth differently,leading to smaller discrepancies than those induced by the two viscosity *** differences are the largest between Maxwell and Burgers rheologies during the 100-1000 years following the beginning of the surface-mass *** show that using the Andrade and Burgers rheologies allows the Earth to respond on decennial to centennial time scales,up to 10 m more than *** only the recent ice-mass changes,the deformation rates derived from Burgers and Andrade rheologies are several times larger than those estimated by Maxwell rheology.

关键词： GIA Antarctica Modeling Rheology Displacement Viscosity GNSS

Online hybrid test using a finite element program and an explicit integration scheme

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Science China(Technological Sciences) 2015年第1期58卷 163-173页

作者： alexandre LAM PAN Peng DENG KaiLai Department of Civil Engineering Tsinghua University Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry Department of Civil Engineering Tsinghua University

A new online hybrid test system combined with substructuring techniques and incorporating finite element methods is *** the proposed system,numerical substructure analysis is conducted by ABAQUS/*** ABAQUS user subroutine is used as the interface between the main control program and ABAQUS to impose the target displacements and determine the reaction *** iteration is needed in this system,making it suitable for physical *** the approach also avoids the need to modify source code,it will be appealing to a number of real engineering *** proposed system adopts a separated-model framework,operator-splitting integration scheme,and data exchange through a socket *** earthquake responses of a simple steel moment-resisting frame are simulated,and the results obtained from the new system are compared to those obtained from the conventional *** is found that the results obtained from the new system are accurate,demonstrating the applicability and efficiency of the proposed *** optimal test parameters are also studied to gain the most accurate results in the minimum time.

关键词： online hybrid test substructuring ABAQUS/Explicit separated-model framework operator-splitting method

Do algae blooms dilute the risk of trematode infections in threespine sticklebacks？

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Current Zoology 2015年第6期61卷 991-995页

作者： alexandre BUDRIA Ulrika CANDOLIN Department of Biosciences University of Helsinki EO. Box 65 FI-00014 Helsinki Finland

Human-induced growth of macro-algae is often assumed to increase trematode infections in fishes by increasing the abtmdanee and condition of the parasite＇s intermediate host - snails - as this can boost the release of trematode larvae, cercariae, from the intermediate hosts. However, macro-algae can also impose barriers to the transmission of cercariae and reduce infections. We investigated whether an increased growth of filamentous algae affects the transmission of Diplostomum pseudospathaceum cercariae to the threespine stickleback Gasterosteus aculeatus, a common fish in eutrophied shallow waters. We exposed stickle- backs to trematode cercariae in the absence and presence of artificial filamentous algae, and recorded effects on the proportion of sticklebacks infected and the number of encysted metacercariae per fish. No significant effect of artificial algae on cercariae transmission was detected. However, the body size and the sex of the sticklebacks were strongly correlated with the number of encysted metacercariae per infected fish, with females and larger individuals being more infected. We discuss different factors that could have caused the difference in parasite transmission, including sex-related differences in body size and behaviour of sticklebacks .

关键词： Anthropogenic disturbance Cercariae Dilution effect Diplostomum pseudospathaceum Eutrophication Filament-ous algae Parasites Physical interference

Influence of manufacturing process-induced geometrical defects on the energy absorption capacity of polymer lattice structures

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Defence Technology（防务技术） 2024年第5期35卷 47-59页

作者： alexandre Riot Enrico Panettieri Antonio Cosculluela Marco Montemurro Universite de Bordeaux Arts et Metiers Institute of TechnologyCNRSINRABordeaux INPHESAM UniversiteI2M UMR 5295F-33405 TalenceFrance French Atomic Energy Commission Route des GargailsCedexF-33114Le BarpFrance

Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different *** them,lattice structures are increasingly used in applications requiring a compromise among lightness and suited mechanical properties,like improved energy absorption capacity and specific stiffness-to-weight and strength-to-weight ratios.A dedicated modeling strategy to assess the energy absorption capacity of lattice structures under uni-axial compression loading is presented in this *** numerical model is developed in a non-linear framework accounting for the strain rate effect on the mechanical responses of the lattice *** geometries,i.e.,cubic body centered cell,octet cell,rhombic-dodecahedron and truncated cuboctahedron 2+,are ***,the influence of the relative density of the representative volume element of each geometry,the strain-rate dependency of the bulk material and of the presence of the manufacturing process-induced geometrical imperfections on the energy absorption capacity of the lattice structure is *** main outcome of this study points out the importance of correctly integrating geometrical imperfections into the modeling strategy when shock absorption applications are aimed for.

关键词： Lattice structures Architected cellular materials Dynamic simulation Energy absorption Geometrical imperfection Additive manufacturing

Simple Classical Lie Algebras in Characteristic 2 and Their Gradations, II

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Algebra Colloquium 2014年第2期21卷 207-214页

作者： alexandre N. Grishkov Marines Guerreiro Instituto de Matematica e Estatfstica Universidade de Sao Paulo Sao Paulo-SP Brazil Departamento de Matematica Universidade Federal de Vicosa Vicosa-MG Brazil

This paper is a continuation of [2]. We prove Conjecture 5.1 of [2] which gives a characterization of simple Lie algebras of finite dimension of type B2e, C2e, D2e＋1, E7 and Es in terms of some gradations of these al... 详细信息

关键词： Lie algebras characteristic 2 gradations

Transient Ablation Regime in Circuit Breakers

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Plasma Science and Technology 2007年第6期9卷 653-656页

作者： alexandre MARTIN Jean-Yves TREPANIER Marcelo REGGIO Ecole Polytechnique MontrealQuebecCanada

Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers. The simplified ablation model used in litterature has been updated to take into account the unsteady state of ablation. Ablation rate and velocity are now calculated by a kinetic model using two layers of transition, between the bulk plasma and the ablating wall. The first layer （Knudsen layer）, right by the wall, is a kinetic layer of a few mean-free path of thickness. The second layer is collision dominated and makes the transition between the kinetic layer and the plasma bulk. With this new coupled algorithm, it is now possible to calculate the temperature distribution inside the wall, as well as more accurate ablation rates.

关键词： circuit breakers electric arc ablation Teflon radiation

Provisioning of Inter-Domain QoS-Aware Services

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Journal of Computer Science & Technology 2015年第2期30卷 404-420页

作者： Fernando Matos alexandre Matos Paulo Simoes Edmundo Monteiro Department of Computer Systems Federal University of Paraba Jodo Pessoa 58051-900 Brazil Department of Information Systems State University of Santa Catarina Sao Bento do Sul 89283-081 Brazil Department of Informatics Engineering University of Coimbra Coimbra 3030-290 Portugal Centre for Informatics and Systems University of Coimbra Coimbra 3030-290 Portugal

Cooperation among service providers, network providers, and access providers in the Internet allows the creation of new services to offer to customers that are in other domains, thus increasing revenue. However, the Internet heterogeneous environment, where each provider has its own policies, infrastructure and business goals, hinders the deployment of more advanced communication services. This paper presents a Quality of Service （QoS） for Inter-Domain Services （QIDS） model that allows inter-domain QoS-aware services to be defined, configured, and adapted in a dynamic and on-demand fashion, among service providers. This is accomplished by： 1） the use of a common communication channel （business layer） where service providers publish and search for services, and interact with each other to contract and manage these services; 2） the templates to specify the business and technical characteristics of the services; 3） the automatic composition of services using service dements （smaller services） a^cording to performance and service-specific QoS parameters; and 4） the creation and enforcement of configuration rules for the underlying infrastructure. A prototype was implemented to validate QIDS and performance tests were conducted on an inter-domain Border Gateway Protocol （BGP）/Multiprotocol Label Switching （MPLS） Virtual Private Network （VPN） scenario.

关键词： service provisioning inter-domain QoS service composition