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Extensive reworking of Archaean crust within the Birimian terrane in Ghana as revealed by combined zircon U-Pb and Lu-Hf isotopes

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Geoscience Frontiers 2018年第1期9卷 173-189页

作者： Andreas Petersson anders Scherstén Axel Gerdes Department of Geology Lund UniversitySolvegatan 12SE-223 62 LundSweden Centre for Exploration Targeting School of Earth and EnvironmentUniversity of Western AustraliaCrawleyAustralia Department of Geosciences Swedish Museum of Natural History104 05 StockholmSweden Institut für Geowissenschaften Senckenberganlage 28D-60054 Frankfurt am MainGermany

Located in the southeastern parts of the BaouléMossi domain of the West African Craton,the Birimian terrane in Ghana is known to consist of predominantly juvenile crust emplaced during the Eburnean *** we present novel coupled zircon U-Pb and Lu-Hf isotope data from nine Birimian granitoids intruding different domains from northwestern,western and southeastern ***-chondriticε_(Hf)-values indicating reworking of Archaean crust are recorded in zircon from both northwestern and southeastern *** a conservative estimate 71%of all analysed zircon grains spanning in age from2220 Ma to 2130 Ma require contribution from a reworked Archaean source,contradicting the common belief that the Birimian terrane consist of predominantly juvenile crust.A minimumε_(Hf)-value of-10.5 at2139 Ma suggests a Palaeoarchaean to late Mseoarchaean component as the contributing ancient *** with previously reported heavy zirconδ^(18)O signatures from Birimian river zircon in Ghana,our new data suggests reworking of Archaean aged sediments during subduction initiated crustal growth in the vicinity of one,or possibly in between two Archaean aged cratons.

关键词： Birimian Baoulé Mossi Archaean Crustal growth Zircon

Annual spatio-temporal migration patterns of Hooded Cranes wintering in Izumi based on satellite tracking and their implications for conservation

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Avian Research 2018年第3期9卷 264-272页

作者： Chunrong Mi anders Pape Moller Yumin Guo College of Nature Conservation Beijing Forestry UniversityBeijing 100083China Ecologie Systématique Evolution UniversitéParis-SudCNRSAgroParisTechUniversitéParis-Saclay91405 Orsay CedexFrance

Background: The Hooded Crane(Grus monacha) is listed as a vulnerable species by IUCN. Knowledge about the migration of the Hooded Crane is still limited. Here we reported the spatio-temporal migration patterns of Hooded Cranes wintering in Izumi, Japan, as well as important stopover areas for their ***: Four adult and five subadult cranes, all wintering in Izumi, Japan, were fitted with satellite transmitters(GPS–GSM system) at their stopover sites in northeastern China in 2014 and 2015. We analyzed the time and duration of adults and subadults in spring and autumn migration, as well as the time and duration they stayed in breeding and wintering ground. In addition, we analyzed the land use of the cranes in stopover ***: Adult cranes took much longer time to migrate both north in spring(mean days) compared with subadult cranes(15.3 and 5.2 days, respectively). H= 44.3 days) and south in fall(mean = 54.0 owever, the subadults had longer wintering(mean = 149.8 days) and nomadic(breeding season for adults) seasons(mean d with adults(133.8 and 122.3 days, respectively). Three important stopover areas have been= 196.8 days) compare identified: the region around Muraviovka Park in Russia, the Songnen Plain in China, and the west coast of South Korea, where cranes spent most of their migration time(62.2 and 85.7% in spring and autumn, respectively). During migration, nomadic period and winter, Hooded Cranes usually stay in croplands for resting and feeding. In non-wintering season, less than 6% of stopover sites were located within protected ***: Overall, our results contribute to understanding the annual spatio-temporal migration patterns of Hooded Cranes in the eastern flyway, and planning conservation measures for this species.

关键词： Conservation Eastern migration route Hooded Cranes(Grus monacha) Izumi Satellite tracking Spatiotemporal migration patterns

A Cartesian Embedded Boundary Method for Hyperbolic Conservation Laws

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Communications in Computational Physics 2007年第6期2卷 1199-1219页

作者： Bjorn Sjogreen N.anders Petersson Center for Applied Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA.

We develop an embedded boundary finite difference technique for solving the compressible two-or three-dimensional Euler equations in complex geometries on a Cartesian *** method is second order accurate with an explicit time step determined by the grid size away from the *** limiters are used on the embedded boundary to avoid non-physical oscillations near shock *** show computed examples of supersonic flow past a cylinder and compare with results computed on a body fitted ***,we discuss the implementation of the method for thin geometries,and show computed examples of transonic flow past an airfoil.

关键词： Embedded boundary hyperbolic conservation law finite difference scheme shock wave.

Super-Grid Modeling of the Elastic Wave Equation in Semi-Bounded Domains

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Communications in Computational Physics 2014年第9期16卷 913-955页

作者： N.anders Petersso Bjorn Sjogreen Center for Applied Scientific Computing L-422LLNLP.O.Box 808LivermoreCA 94551USA

We develop a super-grid modeling technique for solving the elastic wave equation in semi-bounded two-and three-dimensional spatial *** this method,waves are slowed down and dissipated in sponge layers near the far-field ***,this is equivalent to a coordinate mapping that transforms a very large physical domain to a significantly smaller computational domain,where the elastic wave equation is solved numerically on a regular *** damp out waves that become poorly resolved because of the coordinate mapping,a high order artificial dissipation operator is added in layers near the boundaries of the computational *** prove by energy estimates that the super-grid modeling leads to a stable numerical method with decreasing energy,which is valid for heterogeneous material properties and a free surface boundary condition on one side of the *** spatial discretization is based on a fourth order accurate finite difference method,which satisfies the principle of summation by *** show that the discrete energy estimate holds also when a centered finite difference stencil is combined with homogeneous Dirichlet conditions at several ghost points outside of the far-field ***,the coefficients in the finite difference stencils need only be boundary modified near the free *** allows for improved computational efficiency and significant simplifications of the implementation of the proposed method in multi-dimensional *** experiments in three space dimensions show that the modeling error from truncating the domain can be made very small by choosing a sufficiently wide super-grid damping *** numerical accuracy is first evaluated against analytical solutions of Lamb’s problem,where fourth order accuracy is observed with a sixth order artificial *** then use successive grid refinements to study the numerical accuracy in the more complicated motion due to a point moment tensor source in a

关键词： Far field boundary conditions higher order methods elastic wave equation summation by parts.

Stable Grid Refinement and Singular Source Discretization for Seismic Wave Simulations

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Communications in Computational Physics 2010年第10期8卷 1074-1110页

作者： N.anders Petersson Bjorn Sjogreen Center for Applied Scientific Computing L-422Lawrence Livermore National LaboratoryPO Box 808LivermoreCA 94551.

An energy conserving discretization of the elastic wave equation in second order formulation is developed for a composite grid,consisting of a set of structured rectangular component grids with hanging nodes on the grid refinement *** developed summation-by-parts properties are generalized to devise a stable second order accurate coupling of the solution across mesh refinement *** discretization of singular source terms of point force and point moment tensor type are also *** on enforcing discrete moment conditions that mimic properties of the Dirac distribution and its gradient,previous single grid formulas are generalized to work in the vicinity of grid refinement *** source discretization formulas are shown to give second order accuracy in the solution,with the error being essentially independent of the distance between the source and the grid refinement *** numerical examples are given to illustrate the properties of the proposed method.

关键词： Elastic wave equation mesh refinement stability summation by parts singular source term

An Energy Absorbing Far-Field Boundary Condition for the Elastic Wave Equation

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Communications in Computational Physics 2009年第8期6卷 483-508页

作者： N.anders Petersson Bjorn Sjogreen Center for Applied and Scientific Computing L-550 Lawrence Livermore National LaboratoryLivermoreCA 94551USA

We present an energy absorbing non-reflecting boundary condition of Clayton-Engquist type for the elastic wave equation together with a discretization which is stable for any ratio of compressional to shear wave *** prove stability for a second-order accurate finite-difference discretization of the elastic wave equation in three space dimensions together with a discretization of the proposed non-reflecting boundary *** stability proof is based on a discrete energy estimate and is valid for heterogeneous *** proof includes all six boundaries of the computational domain where special discretizations are needed at the edges and *** stability proof holds also when a free surface boundary condition is imposed on some sides of the computational domain.

关键词： Elastic wave equation far-field boundary condition finite differences stability energy estimate

A Stable Finite Difference Method for the Elastic Wave Equation on Complex Geometries with Free Surfaces

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Communications in Computational Physics 2009年第1期5卷 84-107页

作者： Daniel Appelo N.anders Petersson Department of Mechanical Engineering California Institute of TechnologyPasadenaCA 91125USA Center for Applied and Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA

A stable and explicit second order accurate finite difference method for the elastic wave equation in curvilinear coordinates is *** discretization of the spatial operators in the method is shown to be self-adjoint for free-surface,Dirichlet and periodic boundary *** fully discrete version of the method conserves a discrete energy to machine precision.

关键词： Elastic wave equation curvilinear grids finite differences stability energy estimate seismic wave propagation

Ammonia borane-enabled hydrogen transfer processes:Insights into catalytic strategies and mechanisms

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Green Energy & Environment 2023年第4期8卷 948-971页

作者： Wenfeng Zhao Hu Li Heng Zhang Song Yang anders Riisager State Key Laboratory Breeding Base of Green Pesticide&Agricultural Bioengineering Key Laboratory of Green Pesticide&Agricultural BioengineeringMinistry of EducationState-Local Joint Laboratory for Comprehensive Utilization of BiomassCenter for Research&Development of Fine ChemicalsGuizhou UniversityGuiyang550025China Centre for Catalysis and Sustainable Chemistry Department of ChemistryKemitorvet Building 207Technical University of DenmarkDK-2800 Kgs.LyngbyDenmark

Transfer hydrogenation(TH) with in situ generated hydrogen donor is of great importance in reduction reactions, and an alternative strategy to traditional hydrogenation processes involving pressurized molecular hydrogen. Ammonia borane(NH3BH3, AB) is a promising material of hydrogen storage, and it has attracted much attention in reductive organic transformations owing to its high activity, good atom economy, nontoxicity, sustainability, and ease of transport and storage. This review focuses on summarizing the recent progress of AB-mediated TH reactions of diverse substrates including nitro compounds, nitriles, imines, alkenes, alkynes, carbonyl compounds(ketones and aldehydes), carbon dioxide,and N-and O-heterocycles. Syntheses protocols(metal-containing and metal-free), the effect of reaction parameters, product distribution, and variation of reactivity are surveyed, and the mechanism of each reaction involving the action mode of AB as well as structure-activity relationships is discussed in detail. Finally, perspectives are presented to highlight the challenges and opportunities for AB-enabled TH reactions of unsaturated compounds.

关键词： Transfer hydrogenation Ammonia borane Hydrogen donor Reaction mechanism Catalytic strategies

Stable and Efficient Modeling of Anelastic Attenuation in Seismic Wave Propagation

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Communications in Computational Physics 2012年第6期12卷 193-225页

作者： N.anders Petersson Bjorn Sjogreen Center for Applied Scientific Computing L-422Lawrence Livermore National LaboratoryP.O.Box 808LivermoreCA 94551USA

We develop a stable finite difference approximation of the three-dimensional viscoelastic wave *** material model is a super-imposition of N standard linear solid mechanisms,which commonly is used in seismology to model a material with constant quality factor *** proposed scheme discretizes the governing equations in second order displacement formulation using 3N memory variables,making it significantly more memory efficient than the commonly used first order velocitystress *** new scheme is a generalization of our energy conserving finite difference scheme for the elastic wave equation in second order formulation[SIAM ***.,45(2007),pp.1902–1936].Our main result is a proof that the proposed discretization is energy stable,even in the case of variable material *** proof relies on the summation-by-parts property of the *** newscheme is implemented with grid refinement with hanging nodes on the *** experiments verify the accuracy and stability of the new ***-analytical solutions for a half-space problem and the LOH.3 layer over half-space problem are used to demonstrate how the number of viscoelastic mechanisms and the grid resolution influence the *** find that three standard linear solid mechanisms usually are sufficient to make the modeling error smaller than the discretization error.

关键词： Viscoelastic standard linear solid finite difference summation by parts