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arXiv 2019年

作者： Lam, Fredric Y.K. Mi, XiaoCheng Higgins, Andrew J. Institute for Computational and Mathematical Engineering Stanford University StanfordCA94305 United States Laboratory for Scientific Computing Cavendish Laboratory Department of Physics University of Cambridge CambridgeCB3 0HE United Kingdom Department of Mechanical Engineering McGill University MontrealQCH3A 0C3 Canada

The critical dimension necessary for a flame to propagate in suspensions of fuel particles in oxidizer is studied analytically and numerically. Two types of models are considered: First, a continuum model, wherein the individual particulate sources are not resolved and the heat release is assumed spatially uniform, is solved via conventional finite difference techniques. Second, a discrete source model, wherein the heat diffusion from individual sources is modeled via superposition of the Green’s function of each source, is employed to examine the influence of the random, discrete nature of the media. Heat transfer to cold, isothermal walls and to a layer of inert gas surrounding the reactive medium are considered as the loss mechanisms. Both cylindrical and rectangular (slab) geometries of the reactive medium are considered, and the flame speed is measured as a function of the diameter and thickness of the domains, respectively. In the continuum model with inert gas confinement, a universal scaling of critical diameter to critical thickness near 2:1 is found. In the discrete source model, as the time scale of heat release of the sources is made small compared to the interparticle diffusion time, the geometric scaling between cylinders and slabs exhibits values greater than 2:1. The ability of the flame in the discrete regime to propagate in thinner slabs than predicted by continuum scaling is attributed to the flame being able to exploit local fluctuations in concentration across the slab to sustain propagation. As the heat release time of the sources is increased, the discrete source model reverts back to results consistent with the continuum model. Implications of these results for experiments are discussed. Copyright © 2019, The Authors. All rights reserved.

关键词： Solvents

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π-anisotropy: A nanocarbon route to hard magnetism

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Physical Review B 2020年第6期101卷 060408(R)-060408(R)页

作者： Timothy Moorsom Shoug Alghamdi Sean Stansill Emiliano Poli Gilberto Teobaldi Marijan Beg Hans Fangohr Matt Rogers Zabeada Aslam Mannan Ali B. J. Hickey Oscar Cespedes School of Physics and Astronomy University of Leeds Leeds LS2 9JT United Kingdom Department of Physics Taibah University Medina 42331 Saudi Arabia Scientific Computing Department STFC-UKRI Rutherford Appleton Laboratory OX11 0QX Didcot United Kingdom Beijing Computational Science Research Center 100193 Beijing China Stephenson Institute for Renewable Energy Department of Chemistry University of Liverpool Liverpool L69 3BX United Kingdom School of Chemistry University of Southampton Southampton SO17 1BJ United Kingdom Faculty of Engineering and Physical Sciences University of Southampton Southampton United Kingdom European XFEL GmbH Holzkoppel 4 22869 Schenefeld Germany

High coercivity magnets are an important resource for renewable energy, electric vehicles, and memory technologies. Most hard magnetic materials incorporate rare earths such as neodymium and samarium, but concerns about the environmental impact and supply stability of these materials are prompting research into alternatives. Here, we present a hybrid bilayer of cobalt and the nanocarbon molecule C60 which exhibits significantly enhanced coercivity with minimal reduction in magnetization. We demonstrate how this anisotropy enhancing effect cannot be described by existing models of molecule-metal magnetic interfaces. We outline a form of anisotropy, arising from asymmetric magnetoelectric coupling in the metal-molecule interface. Because this phenomenon arises from π−d hybrid orbitals, we propose calling this effect π-anisotropy. While the critical temperature of this effect is currently limited by the rotational degree of freedom of the chosen molecule, C60, we describe how surface functionalization would allow for the design of room-temperature, carbon-based hard magnetic films.

关键词： Anisotropic magnetoresistance Exchange bias Magnetic anisotropy Magnetism Bilayer films Fullerenes Interfaces Density functional calculations Magnetization measurements Micromagnetic modeling

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Spatial proteomics in three-dimensional intact specimens

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四川生理科学杂志 2022年第12期44卷 2202-2202页

作者： Harsharan Singh Bhatia Insititute for Tissue Engineering and Regenerative Medicine (iTERM) Helmholtz Zentrum München 85764 Neuherberg Germany Institute for Stroke and Dementia Research Klinikum der Universität München Ludwig-Maximilians University Munich 81377 Munich Germany Department for Proteomics and Signal Transduction Max Planck Institute of Biochemistry 82152 Martinsried Germany Boehringer Ingelheim Pharma GmbH & Co. KG Drug Discovery Sciences Birkendorfer Str. 65 D-88400 Biberach Riss Germany Graduate School of Neuroscience (GSN) 82152 Munich Germany Munich Cluster for Systems Neurology (SyNergy) 81377 Munich Germany Center for Translational Cancer Research (TranslaTUM) of the TUM 81675 Munich Germany Image-Based Biomedical Modeling Department of Informatics Technical University of Munich 85748 Garching Germany Helmholtz AI Helmholtz Zentrum München 85764 Neuherberg Germany Biomedical Image Analysis Group Department of Computing Imperial College London London SW7 2AZ UK Department for Quantitative Biomedicine University of Zurich 8006 Zurich Switzerland Department of Neuroradiology Klinikum rechts der Isar 81675 Munich Germany Munich Medical Research School (MMRS) 80336 Munich Germany Institute for Diabetes and Cancer Helmholz Zentrum München 85764 Neuherberg Germany Institute for Diabetes and Obesity Helmholz Zentrum München 85764 Neuherberg Germany German Center for Diabetes Research Helmholz Zentrum München 85764 Neuherberg Germany German Center for Neurodegenerative Diseases (DZNE) 81377 Munich Germany Neuroproteomics School of Medicine Klinikum Rechts der Isar Technical University of Munich 81675 Munich Germany Institute of Anatomy University of Leipzig 04109 Leipzig Germany Institute of Computational Biology Helmholz Zentrum München 85764 Neuherberg Germany TUM School of Life Sciences Weihenstephan Technical University of Munich 85354 Freising Germany Department of Mathematics Technical University of Munich 85748 Garching Germany NNF Center for Protein Res

Spatial molecular profiling of complex tissues is essential to investigate cellular function in physiological and pathological ***,methods for molecular analysis of large biological specimens imaged in 3D are ***,we present DISCO-MS,a technology that combines whole-organ/whole-organism clearing and imaging,deep-learning-based image analysis,robotic tissue extraction,and ultra-high-sensitivity mass spectrometry.

关键词： Spatial combine analysis

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Regularity results for the time-harmonic maxwell equations with impedance boundary condition

arXiv

引用

arXiv 2018年

作者： Lu, Peipei Wang, Yun Xu, Xuejun Department of Mathematics Soochow University SuZhou215006 China LSEC Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and System Sciences Chinese Academy of Sciences People's Republic of China School of Mathematical Sciences Tongji University Shanghai China

This paper considers the time-harmonicMaxwell equationswith impedance boundary condition. We present H2-norm bound and other high-order norm bounds for strong solutions. The H2-estimate have been derived in [M. Dauge, M. Costabel and S. Nicaise, Tech. Rep. 10-09, IRMAR (2010)] for the case with homogeneous boundary condition. Unfortunately, their method can not be applied to the inhomogeneous case. The main novelty of this paper is that we follow the spirit of the H1- estimate in [R. Hiptmair, A. Moiola and I. Perugia, Math. Models Methods Appl. Sci., 21(2011), pp. 2263-2287] and modify the proof by applying two inequalities of Friedrichs' type to make the H1-estimate move into H2-estimate and Wm,p-estimate. Finally, the dependence of the regularity estimates on the wave number is obtained, which will play an important role in the convergence analysis of the numerical solutions for the time-harmonicMaxwell equations. Copyright © 2018, The Authors. All rights reserved.

关键词： Boundary conditions

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STABILITY ANALYSIS FOR NONLINEAR SCHRODINGER EQUATIONS WITH NONLINEAR ABSORBING BOUNDARY CONDITIONS

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Journal of computational mathematics 2017年第1期35卷 1-18页

作者： Jiwei Zhang Zhenli Xu Xiaonan Wu Desheng Wang Applied and Computational Mathematics Division Beijing Computational Science Research Center China Department of Mathematics Institute of Natural Sciences and MOE Key Lab of Scientific and Engineering Computing Shanghai Jiao Tong University Shanghai 200240 China Department of Mathematics Hong Kong Baptist University Kowloon Hong Kong China Division of Mathematical Sciences School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore

Local absorbing boundary conditions （LABCs） for nonlinear Schr6dinger equations have been constructed in papers [PRE 78（2008） 026709; and PRE 79 （2009） 046711] using the so-called unified approach. In this paper, we present stability analysis for the reduced problem with LABCs on the bounded computational domain by the energy estimate, and discuss a class of modified versions of LABCs. To prove the stability analysis of the re- duced problem, we turn to the technique of some auxiliary variables which reduces the higher-order derivatives in LABCs into a family of equations with lower-order derivatives. Furthermore, we extend the strategy to the stability analysis of two-dimensional problems by carefully dealing with the LABCs at corners. Numerical examples are given to demon- strate the effectiveness of our boundary conditions and validate the theoretical analysis.

关键词： Nonlinear SchrSdinger equations Energy estimates Absorbing boundaryconditions.

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Construction of Symplectic Runge-Kutta Methods for Stochastic Hamiltonian Systems

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Communications in computational Physics 2017年第1期21卷 237-270页

作者： Peng Wang Jialin Hong Dongsheng Xu Institute of Mathematics Jilin UniversityChangchun 130012P.R.China State Key Laboratory of Scientific and Engineering Computing Institute of ComputationalMathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of Sciences100080 BeijingP.R.China University of Chinese Academy of Sciences P.R.China

We study the construction of symplectic Runge-Kutta methods for stochastic Hamiltonian systems(SHS).Three types of systems,SHS with multiplicative noise,special separable Hamiltonians and multiple additive noise,respectively,are considered in this *** Runge-Kutta(SRK)methods for these systems are investigated,and the corresponding conditions for SRK methods to preserve the symplectic property are *** on the weak/strong order and symplectic conditions,some effective schemes are *** particular,using the algebraic computation,we obtained two classes of high weak order symplectic Runge-Kutta methods for SHS with a single multiplicative noise,and two classes of high strong order symplectic Runge-Kutta methods for SHS with multiple multiplicative and additive noise,*** numerical case studies confirm that the symplectic methods are efficient computational tools for long-term simulations.

关键词： Stochastic differential equation Stochastic Hamiltonian system symplectic integration Runge-Kutta method order condition

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FAIR for AI: An interdisciplinary and international community building perspective

arXiv

引用

arXiv 2022年

作者： Huerta, E.A. Blaiszik, Ben Brinson, L. Catherine Bouchard, Kristofer E. Diaz, Daniel Doglioni, Caterina Duarte, Javier M. Emani, Murali Foster, Ian Fox, Geoffrey Harris, Philip Heinrich, Lukas Jha, Shantenu Katz, Daniel S. Kindratenko, Volodymyr Kirkpatrick, Christine R. Lassila-Perini, Kati Madduri, Ravi K. Neubauer, Mark S. Psomopoulos, Fotis E. Roy, Avik Rübel, Oliver Zhao, Zhizhen Zhu, Ruike Data Science and Learning Division Argonne National Laboratory LemontIL60439 United States Department of Computer Science University of Chicago ChicagoIL60637 United States Globus University of Chicago ChicagoIL60637 United States Department of Mechanical Engineering and Materials Science Duke University DurhamNC27708 United States Scientific Data Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Biological Systems & Engineering Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Helen Wills Neuroscience Institute University of California Berkeley BerkeleyCA94720 United States Department of Physics University of California La Jolla San DiegoCA92093 United States Lund University Department of Physics Box 118 Lund221 00 Sweden School of Physics & Astronomy The University of Manchester ManchesterM13 9PL United Kingdom Leadership Computing Facility Argonne National Laboratory LemontIL60439 United States Biocomplexity Institute Department of Computer Science University of Virginia CharlottesvilleVA22904 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Technical University Munich Arcisstraße 21 München80333 Germany Computational Science Initiative Brookhaven National Laboratory UptonNY11973 United States Electrical and Computer Engineering Rutgers The State University of New Jersey PiscatawayNJ08854 United States National Center for Supercomputing Applications University of Illinois Urbana-Champaign UrbanaIL61801 United States Department of Computer Science University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Electrical & Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States School of Information Sciences University of Illinois at Urbana-Champaign UrbanaIL61801 United States San Diego Supercomputer Center University of California La Jolla San DiegoCA

A foundational set of findable, accessible, interoperable, and reusable (FAIR) principles were proposed in 2016 as prerequisites for proper data management and stewardship, with the goal of enabling the reusability of scholarly data. The principles were also meant to apply to other digital assets, at a high level, and over time, the FAIR guiding principles have been reinterpreted or extended to include the software, tools, algorithms, and workflows that produce data. FAIR principles are now being adapted in the context of AI models and datasets. Here, we present the perspectives, vision, and experiences of researchers from different countries, disciplines, and backgrounds who are leading the definition and adoption of FAIR principles in their communities of practice, and discuss outcomes that may result from pursuing and incentivizing FAIR AI research. The material for this report builds on the FAIR for AI Workshop held at Argonne National Laboratory on June 7, 2022. Copyright © 2022, The Authors. All rights reserved.

关键词： Information management

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Linear Stability of Hyperbolic Moment Models for Boltzmann Equation

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高等学校计算数学学报（英文版） 2017年第2期10卷 255-277页

作者： Yana Di Yuwei Fan Ruo Li Lingchao Zheng LSEC Institute of Computational Mathematics and Scientific/Engineering Computing NCMIS AMSS Chinese Academy of Sciences Beijing 100190China School of Mathematical Sciences Peking University Beijing 100871 China HEDPS & CAPT LMAM & School of Mathematical SciencesPeking University Beijing 100871 China

Grad's moment models for Boltzmann equation were recently regularized to globally hyperbolic systems and thus the regularized models attain local wellposedness for Cauchy *** hyperbolic regularization is only related to the convection term in Boltzmann *** in this paper studied the regularized models with the presentation of collision *** is proved that the regularized models are linearly stable at the local equilibrium and satisfy Yong's first stability condition with commonly used approximate collision terms,and particularly with Boltzmann's binary collision model.

关键词： Boltzmann equation Grad's moment method hyperbolic moment equation linear stability

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Plane wave methods for quantum eigenvalue problems of incommensurate systems

arXiv

引用

arXiv 2018年

作者： Zhou, Yuzhi Chen, Huajie Zhou, Aihui Institute of Applied Physics and Computational Mathematics Bejing100088 China School of Mathematical Sciences Beijing Normal University Beijing100875 China LSEC Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing100049 China

We propose a novel numerical algorithm for computing the electronic structure related eigenvalue problem of incommensurate systems. Unlike the conventional practice that approximates the system by a large commensurate supercell, our algorithm directly discretizes the eigenvalue problem under the framework of a plane wave method. The emerging ergodicity and the interpretation from higher dimensions give rise to many unique features compared to what we have been familiar with in the periodic system. The numerical results of 1D and 2D quantum eigenvalue problems are presented to show the reliability and efficiency of our scheme. Furthermore, the extension of our algorithm to full Kohn-Sham density functional theory calculations are discussed. Copyright © 2018, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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Versatile stabilized finite element formulations for nearly and fully incompressible solid mechanics

arXiv

引用

arXiv 2019年

作者： Karabelas, Elias Haase, Gundolf Plank, Gernot Augustin, Christoph M. Institute for Mathematics and Scientific Computing NAWI Graz University of Graz Graz Austria Gottfried Schatz Research Center Division of Biophysics Medical University of Graz Graz Austria BioTechMed-Graz Graz Austria Department of Mechanical Engineering University of California Berkeley BerkeleyCA United States /IV Graz8010 Austria

computational formulations for large strain, polyconvex, nearly incompressible elasticity have been extensively studied, but research on enhancing solution schemes that offer better tradeoffs between accuracy, robustness, and computational efficiency remains to be highly relevant. In this paper, we present two methods to overcome locking phenomena, one based on a displacement-pressure formulation using a stable finite element pairing with bubble functions, and another one using a simple pressure-projection stabilized P1 − P1 finite element pair. A key advantage is the versatility of the proposed methods: with minor adjustments they are applicable to all kinds of finite elements and generalize easily to transient dynamics. The proposed methods are compared to and verified with standard benchmarks previously reported in the literature. Benchmark results demonstrate that both approaches provide a robust and computationally efficient way of simulating nearly and fully incompressible materials. Copyright © 2019, The Authors. All rights reserved.

关键词： Finite element method

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