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Construction of Conservative Numerical Fluxes for the Entropy Split Method

Communications on Applied Mathematics and Computation 2023年第2期5卷 653-678页

作者： björn sjögreen H.C.Yee Multid Analyses AB GothenburgSweden NASA Ames Research Center Moffett FieldCA 94035USA

The entropy split method is based on the physical entropies of the thermally perfect gas Euler *** Euler flux derivatives are approximated as a sum of a conservative portion and a non-conservative portion in conjunction with summation-by-parts(SBP)difference boundary closure of(Gerritsen and Olsson in J Comput Phys 129:245-262,1996;Olsson and Oliger in RIACS Tech Rep 94.01,1994;Yee et *** J Comp Phys 162:33-81,2000).sj?green and Yee(J Sci Comput)recently proved that the entropy split method is entropy conservative and ***-ard high-order spatial central differencing as well as high order central spatial dispersion relation preserving(DRP)spatial differencing is part of the entropy stable split methodol-ogy *** current work is our first attempt to derive a high order conservative numerical flux for the non-conservative portion of the entropy splitting of the Euler flux *** to the construction,this conservative numerical flux requires higher oper-ations count and is less stable than the original semi-conservative split ***,the Tadmor entropy conservative(EC)method(Tadmor in Acta Numerica 12:451-512,2003)of the same order requires more operations count than the new *** the entropy split method is a semi-conservative skew-symmetric splitting of the Euler flux derivative,a modified nonlinear filter approach of(Yee et *** J Comput Phys 150:199-238,1999,J Comp Phys 162:3381,2000;Yee and sj?green in J Comput Phys 225:910934,2007,High Order Filter Methods for Wide Range of Compressible flow *** of the ICOSAHOM09,June 22-26,Trondheim,Norway,2009)is proposed in conjunction with the entropy split method as the base method for problems containing shock ***-time integration of 2D and 3D test cases is included to show the com-parison of these new approaches.

关键词： Finite-difference method Entropy conservation Entropy splitting Shock capturing

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Stability of Finite Difference Discretizations of Multi-Physics Interface Conditions

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Communications in Computational Physics 2013年第2期13卷 386-410页

作者： björn sjögreen Jeffrey W.Banks Center for Applied Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA

We considermulti-physics computationswhere theNavier-Stokes equations of compressible fluid flow on some parts of the computational domain are coupled to the equations of elasticity on other parts of the computational *** different subdomains are separated by well-defined *** consider time accurate computations resolving all time *** such computations,explicit time stepping is very *** address the issue of discrete interface conditions between the two domains of different physics that do not lead to instability,or to a significant reduction of the stable time step *** such interface conditions is *** discretize the problem with high order centered difference approximations with summation by parts boundary *** derive L2 stable interface conditions for the linearized one dimensional discretized ***,we generalize the interface conditions to the full non-linear equations and numerically demonstrate their stable and accurate performance on a simple model *** energy stable interface conditions derived here through symmetrization of the equations contain the interface conditions derived through normal mode analysis by Banks and sj¨ogreen in[8]as a special case.

关键词： Fluid-structure interaction finite difference method summation by parts multiphysics interface condition

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Variable High-Order Multiblock Overlapping Grid Methods for Mixed Steady and Unsteady Multiscale Viscous Flows,Part II:Hypersonic Nonequilibrium Flows

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Communications in Computational Physics 2013年第2期13卷 583-602页

作者： Andrea Lani björn sjögreen H.C.Yee William D.Henshaw NASA Ames/Stanford Centre for Turbulence Research Palo AltoCAUSA Lawrence Livermore National Laboratory LivermoreCAUSA MS 258-5 NASA Ames Research CenterMoffett FieldCAUSA

The variable high-order multiblock overlapping(overset)grids method of sj¨ogreen&Yee[CiCP,Vol.5,2009]for a perfect gas has been extended to nonequilibrium *** work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts[Wang et al.,***.,2009,2010]that exactly preserve certain non-trivial steady state solutions of the chemical nonequilibrium governing *** turbulence with strong shocks and flows containing both steady and unsteady components is best treated by mixing of numerical methods and switching on the appropriate scheme in the appropriate subdomains of the flow fields,even under the multiblock grid or adaptive grid refinement *** low dissipative sixth-or higher-order shock-capturing filter methods are appropriate for unsteady turbulence with shocklets,second-and thirdorder shock-capturing methods are more effective for strong steady or nearly steady shocks in terms of *** is anticipated that our variable high-order overset grid framework capability with its highly modular design will allow for an optimum synthesis of these new algorithms in such a way that the most appropriate spatial discretizations can be tailored for each particular region of the *** this paper some of the latest developments in single block high-order filter schemes for chemical nonequilibrium flows are applied to overset grid *** numerical approach is validated on a number of test cases characterized by hypersonic conditions with strong shocks,including the reentry flow surrounding a 3D Apollo-like NASA Crew Exploration Vehicle that might contain mixed steady and unsteady components,depending on the flow conditions.

关键词： Unstructured mesh hypersonic flows thermo-chemical nonequilibrium residual distribution schemes double cone

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Violent collisions can reveal hexadecapole deformation of nuclei

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Nuclear Science and Techniques 2024年第7期35卷 1-3页

作者： björn Schenke Physics Department Brookhaven National LaboratoryUptonNY 11973USA

A new observable in heavy ion collision experiments was identified to be sensitive to the hexadecapole deformation of the colliding *** deformation is difficult to measure in traditional nuclear electric transition measurements,as it is often overwhelmed by the nuclear quadrupole *** opens the door to gain new insight into nuclear structure with experiments that were designed to study hot and dense nuclear matter.

关键词： deformation collision insight

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Audio Enhancement for Computer Audition—An Iterative Training Paradigm Using Sample Importance

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Journal of Computer Science & Technology 2024年第4期39卷 895-911页

作者： Manuel Milling Shuo Liu Andreas Triantafyllopoulos Ilhan Aslan björn W.Schuller Chair of Embedded Intelligence for Health Care and Wellbeing University of AugsburgAugsburg 86159Germany Chair of Health Informatics München rechts der IsarTechnical University of MunichMunich 81675Germany Munich Center for Machine Learning Munich 80333Germany Huawei Technologies MunichMunich 80992Germany Munich Data Science Institute Garching 85748Germany Group on Language Audio and MusicImperial College LondonLondon SW72AZU.K.

Neural network models for audio tasks,such as automatic speech recognition(ASR)and acoustic scene classification(ASC),are susceptible to noise contamination for real-life *** improve audio quality,an enhancement module,which can be developed independently,is explicitly used at the front-end of the target audio *** this paper,we present an end-to-end learning solution to jointly optimise the models for audio enhancement(AE)and the subsequent *** guide the optimisation of the AE module towards a target application,and especially to overcome difficult samples,we make use of the sample-wise performance measure as an indication of sample *** experiments,we consider four representative applications to evaluate our training paradigm,i.e.,ASR,speech command recognition(SCR),speech emotion recognition(SER),and *** applications are associated with speech and nonspeech tasks concerning semantic and non-semantic features,transient and global information,and the experimental results indicate that our proposed approach can considerably boost the noise robustness of the models,especially at low signal-to-noise ratios,for a wide range of computer audition tasks in everyday-life noisy environments.

关键词： audio enhancement computer audition joint optimisation multi-task learning voice suppression

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Violent collisions can reveal hexadecapole deformation of nuclei

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Nuclear Science and Techniques 2024年第7期 70-72页

作者： bj?rn Schenke Physics Department Brookhaven National Laboratory

A new observable in heavy ion collision experiments was identified to be sensitive to the hexadecapole deformation of the colliding nuclei. Such deformation is difficult to measure in traditional nuclear electric transition measurements, as it is often overwhelmed by the nuclear quadrupole deformation. This opens the door to gain new insight into nuclear structure with experiments that were designed to study hot and dense nuclear *** structures are determined by the nuclear force, providing fundamental insight into the laws of nature. Deformations,quantifiedbydeviationsfromasphericalshape,area consequence of the interaction between the nuclear shell structure and the residual valence nucleons, whose detailed knowledge is crucial for understanding for example nucleosynthesis,nuclearfission,andneutrinolessdouble-beta decay.

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Accelerated design of high-performance Mg-Mn-based magnesium alloys based on novel bayesian optimization

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Journal of Magnesium and Alloys 2024年第2期12卷 750-766页

作者： Xiaoxi Mi Lili Dai Xuerui Jing Jia She bjørn Holmedal Aitao Tang Fusheng Pan College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Southwest Technology and Engineering Research Institute Chongqing 400039China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)Trondheim 7051Norway

Magnesium(Mg),being the lightest structural metal,holds immense potential for widespread applications in various *** development of high-performance and cost-effective Mg alloys is crucial to further advancing their commercial *** the rapid advancement of machine learning(ML)technology in recent years,the“data-driven''approach for alloy design has provided new perspectives and opportunities for enhancing the performance of Mg *** paper introduces a novel regression-based Bayesian optimization active learning model(RBOALM)for the development of high-performance Mg-Mn-based wrought *** employs active learning to automatically explore optimal alloy compositions and process parameters within predefined ranges,facilitating the discovery of superior alloy *** model further integrates pre-established regression models as surrogate functions in Bayesian optimization,significantly enhancing the precision of the design *** RBOALM,several new high-performance alloys have been successfully designed and ***,after mechanical property testing of the designed alloys,the Mg-2.1Zn-2.0Mn-0.5Sn-0.1Ca alloy demonstrates exceptional mechanical properties,including an ultimate tensile strength of 406 MPa,a yield strength of 287 MPa,and a 23%fracture ***,the Mg-2.7Mn-0.5Al-0.1Ca alloy exhibits an ultimate tensile strength of 211 MPa,coupled with a remarkable 41%fracture elongation.

关键词： Mg-Mn-based alloys High-performance Alloy design Machine learning Bayesian optimization

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Skeletal microstructures of cheilostome bryozoans(phylum Bryozoa,class Gymnolaemata):crystallography and secretion patterns

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Marine Life Science & Technology 2024年第3期6卷 405-424页

作者： Christian Grenier Erika Griesshaber Wolfgang Schmahl björn Berning Antonio G.Checa Departamento de Estratigrafía y Paleontología Universidad de Granada18071 GranadaSpain Instituto Andaluz de Ciencias de La Tierra CSIC-Universidad de Granada18100 ArmillaSpain Department of Earth and Environmental Sciences Ludwig-Maximilians Universität80333 MunichGermany Institute for Geology University of Hamburg20146 HamburgGermany

Gymnolaemata bryozoans produce CaCO3 skeletons of either calcite,aragonite,or *** extensive research,their crystallography and biomineralization patterns remain *** present a detailed study of the microstructures,min-eralogy,and crystallography of eight extant cheilostome species using scanning electron microscopy,electron backscatter diffraction,atomic force microscopy,and micro-computed *** distinguished five basic microstructures,three calcitic(tabular,irregularly platy,and granular),and two aragonitic(granular-platy and fibrous).The calcitic microstruc-tures consist of crystal aggregates that transition from tabular or irregularly platy to granular *** aragonite consists of fibers arranged into *** all cases,the crystallographic textures are axial,and stronger in aragonite than in calcite,with the c-axis as the fiber *** reconstruct the biomineralization sequence in the different species by considering the distribution and morphology of the growth fronts of crystals and the location of the secretory *** bimineralic species,calcite formation always predates aragonite *** interior compound walls,growth proceeds from the cuticle toward the zooecium *** conclude that,with the exception of tabular calcite,biomineralization is remote and occurs within a relatively wide extrapallial space,which is consistent with the inorganic-like appearance of the *** biomineralization mode is rare among invertebrates.

关键词： Biomineralization Bryozoan Skeleton Calcite Aragonite Electron backscatter diffraction

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Induction System for a Fusion Reactor: Quantum Mechanics Chained up

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Journal of High Energy Physics, Gravitation and Cosmology 2024年第1期10卷 158-166页

作者： Friedrich björn Grimm CEO of RES-Institute Stuttgart Germany

In the quest for a sustainable and abundant energy source, nuclear fusion technology stands as a beacon of hope. This study introduces a groundbreaking quantum mechanically effective induction system designed for magnetic plasma confinement within fusion reactors. The pursuit of clean energy, essential to combat climate change, hinges on the ability to harness nuclear fusion efficiently. Traditional approaches have faced challenges in plasma stability and energy efficiency. The novel induction system presented here not only addresses these issues but also transforms fusion reactors into integrated construction systems. This innovation promises compact fusion reactors, marking a significant step toward a clean and limitless energy future, free from the constraints of traditional power sources. This revolutionary quantum induction system redefines plasma confinement in fusion reactors, unlocking clean, compact, and efficient energy production.

关键词： Fusion Reactor Plasma Confinement Quantum Mechanics Clean Energy

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Two-year longitudinal change in choroidal and retinal thickness in school-aged myopic children:exploratory analysis of clinical trials for myopia progression

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Eye and Vision 2024年第4期10卷 1-10页

作者： Meiping Xu Xinping Yu Minghui Wan Kemi Feng Junxiao Zhang Meixiao Shen bjÖrn Drobe Hao Chen Jia Qu Jinhua Bao Eye Hospital and School of Ophthalmology and Optometry Wenzhou Medical UniversityWenzhouZhejiangChina National Clinical Research Center for Ocular Diseases WenzhouZhejiangChina. WEiRC WMU-Essilor International Research CenterWenzhouZhejiangChina R&D Vision Sciences AMERA EssilorInternationalSingaporeSingapore

Background:With increasing axial length(AL)and myopia progression,the micro-structure of the retina and choroid gradually *** study describes the longitudinal changes in retinal and choroidal thickness in school-aged children with myopia and explores the relationship between changes in choroidal thickness and myopia ***:An exploratory analysis of a randomized trial was ***(n=168,aged 7 to 12 years)with myopia from-0.75 diopter(D)to-4.00 D were enrolled in this prospective longitudinal *** refraction,AL,retinal and choroidal thicknesses were measured at baseline and at 1-and 2-year follow-ups."Rapid progression myopia"was defined as increasing in myopia>1.00 D and'"stable progression myopia"was≤1.00 D during the 2-year *** affecting the changes in choroidal thickness were analysed using linear mixed ***:AL significantly increased by 0.67±0.24 mm with a myopic shift of-1.50±0.64 D over the 2 *** overall retinal thickness increased from 251.12±15.91μm at baseline to 253.47±15.74μm at the 2-year followup(F=23.785,Pbjects with rapid progression(F=92.06,P<0.001)but not in those with steady progression(F=2.23,P=0.119).Conclusion:Significant choroidal thinning was observed and was associated with rapid progression and *** findings indicate a need to understand the role of the choroid in eye growth and myopia ***/Precis:The macular choroidal thickness of myopic children is relevant to different degrees of myopic progression in this 2-year longitudinal *** findings suggest that control of choroidal thickness might work to regulate human ocular growth.

关键词： Axial length Choroidal thickness Children Myopia Spectral-domain optical coherence tomography

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