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An Immersed Peridynamics Model of Fluid-Structure Interaction Accounting for Material Damage and Failure

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SSRN

SSRN 2022年

作者： Kim, Keon Ho Bhalla, Amneet Pal Singh Griffith, Boyce E. Department of Mathematics University of North Carolina Chapel HillNC United States Department of Mechanical Engineering San Diego State University San DiegoCA United States Departments of Mathematics Applied Physical Sciences and Biomedical Engineering University of North Carolina Chapel HillNC United States Carolina Center for Interdisciplinary Applied Mathematics University of North Carolina Chapel HillNC United States Computational Medicine Program University of North Carolina Chapel HillNC United States McAllister Heart Institute University of North Carolina Chapel HillNC United States

This paper develops and benchmarks an immersed peridynamics method to simulate the deformation, damage, and failure of hyperelastic materials within a fluid-structure interaction framework. The immersed peridynamics method describes an incompressible structure immersed in a viscous incompressible fluid. It expresses the momentum equation and incompressibility constraint in Eulerian form, and it describes the structural motion and resultant forces in Lagrangian form. Coupling between Eulerian and Lagrangian variables is achieved by integral transforms with Dirac delta function kernels, as in standard immersed boundary (IB) methods. The major difference between our approach and conventional IB methods is that we use peridynamics, instead of classical continuum mechanics, to determine the structural forces. We focus on non-ordinary state-based peridynamic material descriptions that allow us to use a constitutive correspondence framework that can leverage well characterized nonlinear constitutive models of soft materials. The convergence and accuracy of our approach are compared to both conventional and immersed finite element methods using widely used benchmark problems of nonlinear incompressible elasticity. We demonstrate that the immersed peridynamics method yields comparable accuracy with similar numbers of structural degrees of freedom for several choices of the size of the peridynamic horizon. We also demonstrate that the method can generate grid-converged simulations of fluid-driven material damage growth, crack formation and propagation, and rupture under large deformations. © 2022, The Authors. All rights reserved.

关键词： Fluid structure interaction

DeepAstroUDA: Semi-Supervised Universal Domain Adaptation for Cross-Survey Galaxy Morphology Classification and Anomaly Detection

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arXiv 2023年

作者： Ćiprijanović, A. Lewis, A. Pedro, K. Madireddy, S. Nord, B. Perdue, G.N. Wild, S.M. Fermi National Accelerator Laboratory BataviaIL60510 United States Department of Astronomy and Astrophysics University of Chicago ChicagoIL60637 United States Mathematics and Computer Science Division Argonne National Laboratory LemontIL60439 United States Kavli Institute for Cosmological Physics University of Chicago ChicagoIL60637 United States Laboratory for Nuclear Science MIT CambridgeMA02139 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

Artificial intelligence methods show great promise in increasing the quality and speed of work with large astronomical datasets, but the high complexity of these methods leads to the extraction of dataset-specific, non-robust features. Therefore, such methods do not generalize well across multiple datasets. We present a universal domain adaptation method, DeepAstroUDA, as an approach to overcome this challenge. This algorithm performs semi-supervised domain adaptation and can be applied to datasets with different data distributions and class overlaps. Non-overlapping classes can be present in any of the two datasets (the labeled source domain, or the unlabeled target domain), and the method can even be used in the presence of unknown classes. We apply our method to three examples of galaxy morphology classification tasks of different complexities (3-class and 10-class problems), with anomaly detection: 1) datasets created after different numbers of observing years from a single survey (LSST mock data of 1 and 10 years of observations);2) data from different surveys (SDSS and DECaLS);and 3) data from observing fields with different depths within one survey (wide field and Stripe 82 deep field of SDSS). For the first time, we demonstrate the successful use of domain adaptation between very discrepant observational datasets. DeepAstroUDA is capable of bridging the gap between two astronomical surveys, increasing classification accuracy in both domains (up to 40% on the unlabeled data), and making model performance consistent across datasets. Furthermore, our method also performs well as an anomaly detection algorithm and successfully clusters unknown class samples even in the unlabeled target dataset. © 2023, CC BY.

关键词： Galaxies

Hyperfine structure of Yb+173: Toward resolving the Yb173 nuclear-octupole-moment puzzle

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Physical Review A 2020年第2期102卷 022810-022810页

作者： Di Xiao Jiguang Li (李冀光) Wesley C. Campbell Thomas Dellaert Patrick McMillin Anthony Ransford Conrad Roman Andrei Derevianko Department of Physics University of Nevada Reno Nevada 89557 USA Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Physics and Astronomy and Center for Quantum Science and Engineering University of California Los Angeles California 90095 USA

The hyperfine structure (HFS) of atomic energy levels arises due to interactions of atomic electrons with a hierarchy of nuclear multipole moments, including magnetic dipole, electric quadrupole, and higher rank moments. Recently, a determination of the magnetic octupole moment of the Yb173 nucleus was reported from HFS measurements in neutral Yb173 [A. K. Singh et al., Phys. Rev. A 87, 012512 (2013)] and is four orders of magnitude larger than the nuclear theory prediction. Considering this substantial discrepancy between the spectroscopically extracted value and nuclear theory, here we propose to use an alternative system to resolve this tension—a singly charged ion of the same Yb173 isotope. Utilizing the substantial suite of tools developed around Yb+ for quantum information applications, we propose to extract nuclear octupole and hexadecapole moments from measuring hyperfine splittings in the extremely long-lived first excited state [4f13(Fo2)6s2, J=7/2] of Yb+173. We present results of atomic structure calculations in support of the proposed measurements.

关键词： Fine & hyperfine structure

General implicit iterative method for unified gas-kinetic scheme

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arXiv 2021年

作者： Xu, Xiaocong Zhu, Yajun Liu, Chang Xu, Kun Department of Mathematics Hong Kong University of Science and Technology Hong Kong Hong Kong Institute of Applied Physics and Computational Mathematics No. 2 FengHao East Road HaiDian District Beijing100094 China HKUST Shenzhen Research Institute Shenzhen518057 China

In order to further enhance the computational efficiency of the implicit unified gas-kinetic scheme (IUGKS, JCP 315 (2016) 16-38) for multi-scale flow simulation, a two-step IUGKS is proposed in this paper. The multiscale solution of the UGKS is determined by the integral solution of the kinetic model equation, which is composed of the Lagrangian integration of the equilibrium and the free particle transport of the nonequilibrium state. With the implicit evaluation of the macroscopic variables in the first iterative step, the integration of the equilibrium can be directly used in the flux calculation of macroscopic flow variables in the second iterative step. This is equivalent to include the viscous flux in the implicit scheme to accelerate the convergence of the solution instead of using the Euler flux in the iterative process of the original IUGKS. In the present IUGKS, the update of macroscopic flow variables are closely coupled with the implicit evolution of the gas distribution function. At the same time, in order to get the more accurate solution, the full Boltzmann collision term is incorporated into the current scheme through the penalty method. Different iterative techniques, such as LU-SGS and multi-grid, are used for solving the linear algebraic system of coupled macroscopic and microscopic equations. The efficiency of the IUGKS has reached a favorable level among all implicit schemes for the kinetic equations in the literature. Several numerical examples are used to validate the performance of the IUGKS. Accurate solutions have been obtained efficiently in all flow regimes from low speed to hypersonic ones. Copyright © 2021, The Authors. All rights reserved.

关键词： Iterative methods

A new global variance reduction technique based on geometry and energy splitting/roulette

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A new global variance reduction technique based on geometry ...

作者： Zheng, Z. Li, R. Zhou, Y. Mei, Q. Deng, L. Reactor Core Design Department Shanghai Nuclear Engineering Research and Design Institute Co. Ltd. Shanghai200233 China Software Center for High Performance Numerical Simulation Institute of Applied Physics and Computational Mathematics Beijing100094 China

With the increase of computer resources and the application of global variance reduction (GVR) method, it is a trend to obtain global distribution using the Monte Carlo (MC) method in deep-penetration shielding calculation. GVR technique uses biased source and weight window to decrease the MC calculation tally error for deep-penetration problems. However, excessive splitting of large weight particles out of the source region is time-consuming for problems with significant fluence rate variation. A new GVR technique, which performs space and energy splitting/roulette based on the importance of the phase space, is proposed in this paper to avoid excessive splitting of large weight particles. The improved GVR technique is applied to the H. B. Robinson Unit 2 (HBR-2) benchmark and CAP1400 dose rate distribution calculation. Numerical results show that the new GVR technique shows excellent performance for deep-penetration shielding calculation. Copyright © 2020 by ASME

关键词： Monte Carlo methods

Quantifying yeast colony morphologies with feature engineering from time-lapse photography

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arXiv 2022年

作者： Goldschmidt, Andy Kunert-Graf, James Scott, Adrian C. Tan, Zhihao Dudley, Aimée M. Nathan Kutz, J. Department of Physics University of Washington SeattleWA98195 United States Pacific Northwest Research Institute SeattleWA98122 United States Molecular and Cellular Biology Graduate Program University of Washington SeattleWA98195 United States Department of Applied Mathematics University of Washington SeattleWA98195 United States

Baker's yeast (Saccharomyces cerevisiae) is a model organism for studying the morphology that emerges at the scale of multi-cell colonies. To look at how morphology develops, we collect a dataset of time-lapse photographs of the growth of different strains of S. cerevisiae. We discuss the general statistical challenges that arise when using time-lapse photographs to extract time-dependent features. In particular, we show how texture-based feature engineering and representative clustering can be successfully applied to categorize the development of yeast colony morphology using our dataset. The Local binary patterns (LBP) from image processing is used to score the surface texture of colonies. This texture score develops along a smooth trajectory during growth. The path taken depends on how the morphology emerges. A hierarchical clustering of the colonies is performed according to their texture development trajectories. The clustering method is designed for practical interpretability;it obtains the best representative colony image for any hierarchical sub-cluster. Copyright © 2022, The Authors. All rights reserved.

关键词： Morphology

Dynamical Mean Field Studies of Infinite Layer Nickelates: physics Results and Methodological Implications

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arXiv 2022年

作者： Chen, Hanghui Hampel, Alexander Karp, Jonathan Lechermann, Frank Millis, Andrew NYU-ECNU Institute of Physics NYU Shanghai 1555 Century Avenue Shanghai200122 China Department of Physics New York University 726 Broadway New YorkNY10003 United States Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Department of Applied Physics and Applied Mathematics Columbia University 538 West 120th Street New YorkNY10027 United States European XFEL Holzkoppel 4 Schenefeld22869 Germany Department of Physics Columbia University 538 West 120th Street New YorkNY10027 United States

This article summarizes recent work on the many-body (beyond density functional theory) electronic structure of layered rare-earth nickelates, both in the context of the materials themselves and in comparison to the high-temperature superconducting (high-Tc) layered copper-oxide compounds. It aims to outline the current state of our understanding of layered nickelates and to show how the analysis of these fascinating materials can shed light on fundamental questions in modern electronic structure theory. A prime focus is determining how the interacting physics defined over a wide energy range can be estimated and "downfolded" into a low energy theory that would describe the relevant degrees of freedom on the ∼ 0.5 eV scale and that could be solved to determine superconducting and spin and charge density wave phase boundaries, temperature dependent resistivities, and dynamical susceptibilities. © 2022, CC BY.

关键词： Density functional theory

Interplay between breathing-mode distortions and magnetic order in rare-earth nickelates from ab initio magnetic models

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arXiv 2021年

作者： Badrtdinov, Danis I. Hampel, Alexander Dreyer, Cyrus E. Theoretical Physics and Applied Mathematics Department Ural Federal University Yekaterinburg620002 Russia Center for Computational Quantum Physics Flatiron Institute 162 Fifth avenue New YorkNY10010 United States Department of Physics and Astronomy Stony Brook University Stony BrookNY11794-3800 United States

We use density-functional theory calculations to explore the magnetic properties of perovskite rare-earth nickelates, RNiO3, by constructing microscopic magnetic models containing all relevant exchange interactions via Wannierization and Green’s function techniques. These models elucidate the mechanism behind the formation of antiferromagnetic order with the experimentally observed propagation vector, and explain the reason previous DFT plus Hubbard U calculations favored ferromagnetic order. We perform calculations of magnetic moments and exchange-coupling parameters for different amplitudes of the R1+ breathing mode distortion, which results in expanded and compressed NiO6 octahedra. We find that the magnetic moment vanishes for the "short bond" nickels, i.e., the ones in the compressed octahedra. The inclusion of spin-orbit coupling demonstrates that the magnetic anisotropy is very small, while the magnetic moment of the short bond nickel atoms tend to zero even for the noncollinear case. Our results provide a clear picture of the trends of the magnetic order across the nickelate series and give insights into the coupling between magnetic order and structural distortions. © 2021, CC BY.

关键词： Magnetic moments

Kinetic Frustration Effects on Dense Two-Dimensional Packings of Convex Particles and Their Structural Characteristics

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arXiv 2021年

作者： Maher, Charles Emmett Stillinger, Frank H. Torquato, Salvatore Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Physics Princeton University PrincetonNJ08544 United States Princeton Institute for the Science and Technology of Materials Princeton University PrincetonNJ08544 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

The study of hard-particle packings is of fundamental importance in physics, chemistry, cell biology, and discrete geometry. Much of the previous work on hard-particle packings concerns their densest possible arrangements. By contrast, we examine kinetic effects inevitably present in both numerical and experimental packing protocols. Specifically, we determine how changing the compression/shear rate of a two-dimensional packing of noncircular particles causes it to deviate from its densest possible configuration, which is always periodic. The adaptive shrinking cell (ASC) optimization scheme maximizes the packing fraction of a hard-particle packing by first applying random translations and rotations to the particles and then isotropically compressing and shearing the simulation box repeatedly until a possibly jammed state is reached. We use a stochastic implementation of the ASC optimization scheme to mimic different effective time scales by varying the number of particle moves between compressions/shears. We generate dense, effectively jammed, monodisperse, two-dimensional packings of obtuse scalene triangle, rhombus, curved triangle, lens, and "ice cream cone" (a semicircle grafted onto an isosceles triangle) shaped particles, with a wide range of packing fractions and degrees of order. To quantify these kinetic effects, we introduce the kinetic frustration index K, which measures the deviation of a packing from its maximum possible packing fraction. To investigate how kinetics affect short- and long-range ordering in these packings, we compute their spectral densities χV (k) and characterize their contact networks. We find that kinetic effects are most significant when the particles have greater asphericity, less curvature, and less rotational symmetry. This work may be relevant to the design of laboratory packing protocols. Copyright © 2021, The Authors. All rights reserved.

关键词： Kinetic theory