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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

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 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.

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

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

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

Lumbar interspinous pressure pain threshold values for healthy young men and women and the effect of prolonged fully flexed lumbar sitting posture:An observational study

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World Journal of Orthopedics 2020年第3期11卷 158-166页

作者： Martin petersson Allan Abbott Department of physiotherapy Gripen Värmland Country CouncilKarlstad SE-65224Sweden Department of Medical and Health Sciences Division of PhysiotherapyFaculty of Health SciencesLinköping UniversityLinköping SE-58183Sweden

BACKGROUND Low back pain(LBp)is a common condition with large burden *** to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported *** study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain,despite this being a suggested risk factor for *** To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous *** This is a an observational before and after study of 26 participants(13 men,13 women)between 20-35 years *** was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine *** algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back(Borg CR10=7/10).Wilcoxon signed-rank test was used for analyze values from the before and after test ***-Whitney U test was used to investigate potential gender *** Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%.For all pain pressure threshold locations tested,there was a significant difference for the study population with moderate-large decreased(r=-0.56)pressure pain threshold after exposure to prolonged flexed sitting posture(pparisons between gender did not show any significant *** The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previo

关键词： Low back pain pain pressure threshold Algometer posture Spine pain mechanism

Muco-submucosal elongated polyps of the gastrointestinal tract:A case series and a review of the literature

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World Journal of Gastroenterology 2013年第11期19卷 1845-1849页

作者： Char Loo Tan Sze Hwa Tan Jimmy BY So Fredrik petersson Department of pathology National University Hospital SystemSingapore 119074Singapore Department of Surgery National University Hospital SystemSingapore 119074Singapore

We present three cases of gastrointestinal muco-submucosal elongated polyps,two located in the duodenum and one in the descending *** three cases had a characteristic,"worm-like" endoscopic appearance and were lined by unremarkable *** vascular component was located in the submucosa and was composed of a mixture of variably dilated blood vessels(capillaries and veins) and *** duodenal polyps displayed lipomatous metaplasia of the submucosal *** dual vascular phenotype of the vascular component was confirmed by immunohistochemistry with D2-40 and CD31.

关键词： Muco-submucosal elongated polyp Vascular malformation Endoscopic ultrasonography Angioma Endoscopy

Towards trustworthy multi-modal motion prediction:Holistic evaluation and interpretability of outputs

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CAAI Transactions on Intelligence Technology 2024年第3期9卷 557-572页

作者： Sandra Carrasco Limeros Sylwia Majchrowska Joakim Johnander Christoffer petersson MiguelÁngel Sotelo David Fernández Llorca Computer Engineering Department Polytechnic SchoolUniversity of AlcalaMadridSpain AI Sweden GothenburgSweden Zenseact AB GothenburgSweden Department of Electrical Engineering Linköping UniversityLinköpingSweden Chalmers University of Technology GothenburgSweden European Commission Joint Research CentreSevilleSpain

predicting the motion of other road agents enables autonomous vehicles to perform safe and efficient path *** task is very complex,as the behaviour of road agents depends on many factors and the number of possible future trajectories can be consid-erable(multi-modal).Most prior approaches proposed to address multi-modal motion prediction are based on complex machine learning systems that have limited ***,the metrics used in current benchmarks do not evaluate all aspects of the problem,such as the diversity and admissibility of the *** authors aim to advance towards the design of trustworthy motion prediction systems,based on some of the re-quirements for the design of Trustworthy Artificial *** focus is on evaluation criteria,robustness,and interpretability of ***,the evaluation metrics are comprehensively analysed,the main gaps of current benchmarks are identified,and a new holistic evaluation framework is ***,a method for the assessment of spatial and temporal robustness is introduced by simulating noise in the perception *** enhance the interpretability of the outputs and generate more balanced results in the proposed evaluation framework,an intent prediction layer that can be attached to multi-modal motion prediction models is *** effectiveness of this approach is assessed through a survey that explores different elements in the visualisation of the multi-modal trajectories and *** proposed approach and findings make a significant contribution to the development of trustworthy motion prediction systems for autono-mous vehicles,advancing the field towards greater safety and reliability.

关键词： autonomous vehicles evaluation interpretability multi-modal motion prediction robustness trustworthy AI