160 research outputs found

    Multistable pendula as mechanical analogs of ferroelectricity

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    Magnetically-controlled and elastically-coupled multistable pendula are shown to serve as versatile structural analogs of ferroelectric crystals, mimicking atomic-level phenomena of domain patterning, domain nucleation, and Allen–Cahn-type domain wall motion under an applied bias, as found, e.g., in ferroelectric switching. We demonstrate the quantitative analogy with material-level transitions via a homogenized continuum description, including structural-level realizations of temperature and lattice defects. Existing photonic, phononic, and topological metamaterials are thus complemented by a new mechanical analog of the nonlinear dissipative kinetics of structural transformations.ISSN:2352-431

    De novo genome assembly of the raccoon dog (nyctereutes procyonoides)

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    The raccoon dog, Nyctereutes procyonoides (NCBI Taxonomy ID: 34880, Figure 1a) belongs to the family Canidae, with foxes (genus Vulpes) being their closest relatives (Lindblad-Toh et al., 2005; Sun et al., 2019). Its original distribution in East Asia ranges from south-eastern Siberia to northern Vietnam and the Japanese islands. In the early 20th century, the raccoon dog was introduced into Western Russia for fur breeding and hunting purposes, which led to its widespread establishment in many European countries, Figure 1b. Together with the raccoon (Procyon lotor), it is now listed in Europe as an invasive species of Union concern (Regulation (EU) No. 1143/2014) and member states are required to control pathways of introductions and manage established populations.The present study is a result of the Centre for Translational Biodiversity Genomics (LOEWE-TBG) and was supported through the program LOEWE-Landes-Offensive zur Entwicklung Wissenschaftlich-okonomischer Exzellenz of Hesse's Ministry of Higher Education, Research, and the Arts. This study was also supported by the German Federal Environmental Foundation (DBU, Grant number 35524/01) and by Uniscientia Stiftung Vaduz (P 180-2021). LC was supported by a Post-doctoral Fellowship awarded by the Department of Education, Universities and Research of the Basque Government (Ref.: POS_2018_1_0012)

    On the computation of the exact overall consistent algorithmic tangent moduli for non-linear finite strain homogenization problems using six finite perturbations

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    This work is concerned with the development of a numerically robust two-scale computational approach for the prediction of the local and overall mechanical behavior of heterogeneous materials with non-linear constitutive behavior at finite strains. Assuming scale separation, the macroscopic constitutive behavior is determined by the mean response of the underlying microstructure which is attached to each macroscopic integration point in the form of a periodic unit cell. The algorithmic formulation and numerical solution of the two locally-coupled boundary value problems is based on the FE-FFT method (e.g. [14, 17]). In particular, a numerically robust algorithmic formulation for the computation of the overall consistent algorithmic tangent moduli is presented. The underlying concept is a perturbation method. In contrast to existing numerical tangent computation algorithms the proposed method yields the exact tangent using only six (instead of nine) perturbations (3 in 2d). As an example, the micromechanical fields and effective material behavior of elasto-viscoplastic polycrystals are predicted for representative simulation examples. copyright © Crown copyright (2018).All right reserved

    On Quasi‐Newton methods in fast Fourier transform‐based micromechanics

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    This work is devoted to investigating the computational power of Quasi‐Newton methods in the context of fast Fourier transform (FFT)‐based computational micromechanics. We revisit FFT‐based Newton‐Krylov solvers as well as modern Quasi‐Newton approaches such as the recently introduced Anderson accelerated basic scheme. In this context, we propose two algorithms based on the Broyden‐Fletcher‐Goldfarb‐Shanno (BFGS) method, one of the most powerful Quasi‐Newton schemes. To be specific, we use the BFGS update formula to approximate the global Hessian or, alternatively, the local material tangent stiffness. Both for Newton and Quasi‐Newton methods, a globalization technique is necessary to ensure global convergence. Specific to the FFT‐based context, we promote a Dong‐type line search, avoiding function evaluations altogether. Furthermore, we investigate the influence of the forcing term, that is, the accuracy for solving the linear system, on the overall performance of inexact (Quasi‐)Newton methods. This work concludes with numerical experiments, comparing the convergence characteristics and runtime of the proposed techniques for complex microstructures with nonlinear material behavior and finite as well as infinite material contrast

    Roadmap on multiscale materials modeling

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    Abstract Modeling and simulation is transforming modern materials science, becoming an important tool for the discovery of new materials and material phenomena, for gaining insight into the processes that govern materials behavior, and, increasingly, for quantitative predictions that can be used as part of a design tool in full partnership with experimental synthesis and characterization. Modeling and simulation is the essential bridge from good science to good engineering, spanning from fundamental understanding of materials behavior to deliberate design of new materials technologies leveraging new properties and processes. This Roadmap presents a broad overview of the extensive impact computational modeling has had in materials science in the past few decades, and offers focused perspectives on where the path forward lies as this rapidly expanding field evolves to meet the challenges of the next few decades. The Roadmap offers perspectives on advances within disciplines as diverse as phase field methods to model mesoscale behavior and molecular dynamics methods to deduce the fundamental atomic-scale dynamical processes governing materials response, to the challenges involved in the interdisciplinary research that tackles complex materials problems where the governing phenomena span different scales of materials behavior requiring multiscale approaches. The shift from understanding fundamental materials behavior to development of quantitative approaches to explain and predict experimental observations requires advances in the methods and practice in simulations for reproducibility and reliability, and interacting with a computational ecosystem that integrates new theory development, innovative applications, and an increasingly integrated software and computational infrastructure that takes advantage of the increasingly powerful computational methods and computing hardware.</jats:p