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arXiv 2022年

作者： Lu, Zhipeng Stern, Miranda Li, Jinqiao Candia, David Yao-Bate, Lorenzo Celenza, Thomas J. Azadi, Mohsen Campbell, Matthew F. Bargatin, Igor Department of Chemistry University of Pennsylvania United States Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania United States Department of Materials Science and Engineering University of Pennsylvania United States Department of Physics University of Pennsylvania United States Singh Center for Nanotechnology University of Pennsylvania United States

Photophoretic levitation is a propulsion mechanism in which lightweight objects can be lifted and controlled through their interactions with light. Since photophoretic forces on macroscopic objects are usually maximized at low pressures, they may be tested in vacuum chambers in close proximity to the chamber floor and walls. We report here experimental evidence that the terrain under levitating microflyers, including the chamber floor or the launchpad from which microflyers lift off, can greatly increase the photophoretic lift forces relative to their free-space (mid-air) values. To characterize this so-called "ground effect" during vacuum chamber tests, we introduced a new miniature launchpad composed of three J-shaped (candy-cane-like) wires that minimized a microflyer's extraneous interactions with underlying surfaces. We compared our new launchpads to previously used wire-mesh launchpads for simple levitating mylar-based disks with diameters of 2, 4, and 8 cm. Importantly, wire-mesh launchpads increased the photophoretic lift force by up to sixfold. A significant ground effect was also associated with the bottom of the vacuum chamber, particularly when the distance to the bottom surface was less than the diameter of the levitating disk. We provide guidelines to minimize the ground effect in vacuum chamber experiments, which are necessary to test photophoretic microflyers intended for high-altitude exploration and surveillance on Earth or on Mars. © 2022, CC BY.

关键词： Floors

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Strain transfer in ferroelectric-ferrimagnetic magnetoelectric composite

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Physical Review B 2021年第14期103卷 L140106-L140106页

作者： Sujoy Saha Ram Prakash Singh Ying Liu Atal Bihari Swain Amritesh Kumar V. Subramanian A. Arockiarajan G. Srinivasan Rajeev Ranjan Department of Materials Engineering Indian Institute of Science Bangalore-560012 India Department of Physics Oakland University Rochester Michigan 48309-4479 USA Department of Materials Science and Engineering Hubei University Wuhan 430062 China Department of Physics Indian Institute of Technology Madras Chennai-600036 India Department of Applied Mechanics Indian Institute of Technology Madras Chennai-600036 India

We show that electrically poled ferroelectric matrix considerably enhances the localized magnetostrictive deformations in a ferroelectric-ferrimagnetic composite. Magnetostrain measurements performed on Dy-free and Dy-modified BiFeO3−PbTiO3 (BF-PT) ferroelectric ceramics revealed no measurable macroscopic strain in poled and unpoled Dy-free nonferromagnetic specimens. Dy-modified BF-PT, on the other hand, exhibit ferrimagnetic dysprosium-iron garnet (DyIG) as precipitates and exhibit a macroscopic strain of −4 ppm in the poled state. Despite the small (6%) volume fraction of DyIG, the macroscopic strain in Dy-modified BF-PT is almost 50% of the strain of pure DyIG. Our results suggest that the amplification of the localized magnetostrictive deformation in the ferrimagnetic islands by the neighboring ferroelectric regions is caused by the magnetostrictive stress-induced motion of ferroelectric-ferroelastic domains of the poled ferroelectric matrix.

关键词： Ferroelectricity Magnetoelectric effect Magnetostriction Piezoelectricity Multiferroics Polycrystalline materials Magnetization measurements Strain engineering

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The challenges of measuring spin Seebeck noise

arXiv

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arXiv 2023年

作者： Luo, Renjie Zhao, Xuanhan Legvold, Tanner J. Chen, Liyang Liu, Changjiang Hong, Deshun Bhattacharya, Anand Natelson, Douglas Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Program Smalley-Curl Institute Rice University HoustonTX77005 United States Materials Science Division Argonne National Laboratory LemontIL60439 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Just as electronic shot noise in driven conductors results from the granularity of charge and the statistical variation in the arrival times of charge carriers, there are predictions for fundamental noise in magnon currents due to angular momentum being carried by discrete excitations. The inverse spin Hall effect as a transduction mechanism to convert spin current into charge current raises the prospect of experimental investigations of such magnon shot noise. Spin Seebeck effect measurements have demonstrated the electrical detection of thermally driven magnon currents and have been suggested as an avenue for accessing spin current fluctuations. Using spin Seebeck structures made from yttrium iron garnet on gadolinium gallium garnet, we demonstrate the technical challenges inherent in such noise measurements. While there is a small increase in voltage noise in the inverse spin Hall detector at low temperatures associated with adding a magnetic field, the dependence on field orientation implies that this is not due to magnon shot noise. We describe theoretical predictions for the expected magnitude of magnon shot noise, highlighting ambiguities that exist. Further, we show that magnon shot noise detection through the standard inverse spin Hall approach is likely impossible due to geometric factors. Implications for future attempts to measure magnon shot noise are discussed. Copyright © 2023, The Authors. All rights reserved.

关键词： Shot noise

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Computational design of anisotropic stealthy hyperuniform composites with engineered directional scattering properties

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Physical Review E 2023年第4期108卷 045306-045306页

作者： Wenlong Shi David Keeney Duyu Chen Yang Jiao Salvatore Torquato Materials Science and Engineering Arizona State University Tempe Arizona 85287 USA Materials Research Laboratory University of California Santa Barbara California 93106 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Institute of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

Disordered hyperuniform materials are an emerging class of exotic amorphous states of matter that endow them with singular physical properties, including large isotropic photonic band gaps, superior resistance to fracture, and nearly optimal electrical and thermal transport properties, to name but a few. Here we generalize the Fourier-space-based numerical construction procedure for designing and generating digital realizations of isotropic disordered hyperuniform two-phase heterogeneous materials (i.e., composites) developed by Chen and Torquato [Acta Mater. 142, 152 (2018)] to anisotropic microstructures with targeted spectral densities. Our generalized construction procedure explicitly incorporates the vector-dependent spectral density function χ̃V(k) of arbitrary form that is realizable. We demonstrate the utility of the procedure by generating a wide spectrum of anisotropic stealthy hyperuniform microstructures with χ̃V(k)=0 for k∈Ω, i.e., complete suppression of scattering in an “exclusion” region Ω around the origin in Fourier space. We show how different exclusion-region shapes with various discrete symmetries, including circular-disk, elliptical-disk, square, rectangular, butterfly-shaped, and lemniscate-shaped regions of varying size, affect the resulting statistically anisotropic microstructures as a function of the phase volume fraction. The latter two cases of Ω lead to directionally hyperuniform composites, which are stealthy hyperuniform only along certain directions and are nonhyperuniform along others. We find that while the circular-disk exclusion regions give rise to isotropic hyperuniform composite microstructures, the directional hyperuniform behaviors imposed by the shape asymmetry (or anisotropy) of certain exclusion regions give rise to distinct anisotropic structures and degree of uniformity in the distribution of the phases on intermediate and large length scales along different directions. Moreover, while the anisotropic exclusion regions

关键词： Amorphous materials Complex materials Simulated annealing

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Artificial neural network approach for turbulence models: A local framework

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Physical Review Fluids 2021年第8期6卷 084612-084612页

作者： Chenyue Xie Xiangming Xiong Jianchun Wang Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China

A local artificial neural network (LANN) framework is developed for turbulence modeling. The Reynolds-averaged Navier-Stokes (RANS) unclosed terms are reconstructed by the artificial neural network based on the local coordinate system which is orthogonal to the curved walls. We verify the proposed model in the flows over periodic hills. The correlation coefficients of the RANS unclosed terms predicted by the LANN model can be made larger than 0.96 in an a priori analysis, and the relative error of the unclosed terms can be made smaller than 18%. In an a posteriori analysis, detailed comparisons are made on the results of RANS simulations using the LANN, global artificial neural network (GANN), Spalart-Allmaras (SA), and shear stress transport (SST) k−ω models. It is shown that the LANN model performs better than the GANN, SA, and SST k−ω models in the prediction of the average velocity, wall-shear stress, and average pressure, which gives the results that are essentially indistinguishable from the direct numerical simulation data. The LANN model trained at low Reynolds number, Re=2800, can be directly applied to the cases of high Reynolds numbers, Re=5600, 10 595, 19 000, and 37 000, with accurate predictions. Furthermore, the LANN model is verified for flows over periodic hills with varying slopes. These results suggest that the LANN framework has a great potential to be applied to complex turbulent flows with curved walls.

关键词： Compressible boundary layers Turbulence Artificial neural networks

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Intelligent Prediction and Analysis of Mechanical Properties of Magnesium Alloys Using Interpretable Machine Learning

SSRN

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SSRN 2023年

作者： Moses, Atwakyire Gui, Ying Michael, Marembo Chen, Buzhuo Chen, Ding State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China Faculty of Engineering Technology Applied Design and Fine Art Department of Mechanical Engineering Kabale University P.O. Box 317 Kabale Uganda CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics University of Science and Technology of China Hefei230027 China Department of Material Science and Engineering The Ohio State University ColumbusOH43210 United States

The Magnesium-rare earth alloy dataset was compiled by collecting data from the experiment and utilizing machine learning (ML) models to predict the mechanical properties of 348 sample tests. The proportion between the predicted and experimental results produced by different ML models demands more advanced regression methods to obtain better results. Utilizing magnesium chemical compositions at elevated temperatures as input variables and mechanical properties as output variables, four different machine learning (ML) models were employed namely (i.e.) Random Forest (RF), Extra Tree (ET), Gradient Boost (GB), and XG Boost (XGB) to resolve this difficult problem. Each single algorithm aimed to predict the mechanical properties of Mg-rare earth alloy i.e. ultimate tensile strength (UTS), yield strength (YS), and elongation (EL). Subsequently, the data-driven intelligent prediction modeling technique called Super learner (SL) was employed to integrate the single models into the stacked model approach to enhance prediction accuracy. The results obtained using SL models demonstrated enhanced prediction accuracy for UTS, YS, and EL. The findings further demonstrate enhanced prediction ability by outperforming other approaches as demonstrated by lower RMSE and higher R2 compared to previous studies. The reason to choose SL is because of its robustness, less prone to overfitting, and is also widely known for its better scalability, simplicity, and ability to handle noisy. The SL model is an optimal approach for predicting the properties of Mg-rare earth alloys. The proposed SL approach can serve as a tool for predicting the properties of Mg alloys. © 2023, The Authors. All rights reserved.

关键词： Magnesium alloys

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Challenges in Developing materials for Microreactors: A Case-Study of Yttrium Dihydride in Extreme Conditions

SSRN

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SSRN 2023年

作者： Tunes, Matheus Araujo Parkison, Darren Huang, Yuqing Chancey, M.R. Vogel, Sven C. Mehta, Vedant K. Torrez, Michael A. Luther, E.P. Valdez, James A. Wang, Yongqiang Yu, Jianguo Cinbiz, Mahmut Nedim Shivprasad, Aditya P. Kohnert, Cailtin A. Montanuniversität Leoben Austria Materials Science and Technology Division Los Alamos National Laboratory United States Department of Nuclear Engineering University of California Berkeley United States Department of Nuclear Engineering North Carolina State University United States Irradiated Fuels and Materials Idaho National Laboratory United States Program Project Interface Division Los Alamos National Laboratory United States Sigma Division Los Alamos National Laboratory United States Computational Mechanics and Materials Idaho National Laboratory United States Materials Science and Technology Division Oak Ridge National Laboratory United States

The development of microreactor technology presents an efficient solution for providing portable electricity, catering to both human space exploration needs within our solar system and supplying power to remote Earth-bound areas. The miniaturization of nuclear reactors poses immediate new challenges for materials science with respect to the capability for controlling nuclear reactions via thermalization of highly-energetic neutrons. In a microreactor, neutron moderation takes place in compact geometries, therefore new moderator materials are required to exhibit high moderating power per unit of volume. This challenge is currently being addressed through the advancement of hydrogen technology and materials science, particularly focusing on development of transition metal hydrides, but to date, research on their irradiation response, specifically regarding phase stability, hydrogen in-lattice retention, and their dependence on irradiation temperature and dose, is limited. Herein, we present a detailed investigation on the response of yttrium dihydride (\ce{YH2}) - the most suitable moderator candidate with respect to its high operational temperature - to heavy ion irradiation. A combination of multiple experimental techniques indicate that \ce{YH2} is stable up to an irradiation dose of 2 dpa and below 800$^{\circ}$C, identified as a critical temperature for \ce{YH2}. Our study unravels that voids emerge as the major form of radiation damage. Below the critical temperature no phase change, precipitation or amorphization was observed to occur. Experimental results from ion beam and neutron scattering techniques with concomitant density functional theory calculations have allowed us to elaborate and propose new strategies to enhance the metal hydride performance in extreme environments. © 2023, The Authors. All rights reserved.

关键词： Hydrides

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A First-Principles and Calphad-Assisted Phase-Field Model for Microstructure Evolution: Application to Mo-V Binary Alloy Systems

SSRN

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SSRN 2023年

作者： Thakur, Abhishek Kumar Kovacevic, Sasa Manga, Venkateswara Rao Deymier, Pierre Alix Muralidharan, Krishna Department of Materials Science and Engineering University of Arizona TucsonAZ85721 United States Department of Civil and Environmental Engineering Imperial College London LondonSW7 2AZ United Kingdom Lunar and Planetary Laboratory University of Arizona TucsonAZ85721 United States Graduate Interdisciplinary Program in Applied Mathematics India

A multiscale computational framework combining the first-principles calculations and the CALPHAD approach with the phase-field method is presented to simulate the microstructure evolution in multicomponent steel alloys. We demonstrate the potential of the framework by predicting the microstructural evolution in elastically periodic arrays of the Mo-V binary sub-system. The framework utilizes the first-principles calculations using special quasi-random structures. Hitherto unavailable thermodynamic and material properties of the alloy are obtained by employing the first-principles calculations and the CALPHAD approach and fed into the phase-field model to predict the microstructure evolution at different temperatures within the miscibility gap region. In addition to the temperature and cooling rates, the model incorporates the role of mechanical fields in decomposition kinetics in the Mo-V binary alloy system. Regimes for temperatures and cooling rates at which spinodal decomposition occurs are identified. Applying external loading leads to directional phase separation in the Mo-V binary system. The elastic inhomogeneity in terms of material properties between the two phases initiates the directional alignment while eigenstrains and applied external loading control the degree of alignment. The framework developed is general and extendable to higher multicomponent sub-systems in steel alloys. © 2023, The Authors. All rights reserved.

关键词： Temperature

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Parity-time symmetry breaking enables swarming motility in Caenorhabditis elegans

arXiv

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arXiv 2024年

作者： Basaran, Mustafa Yüce, Tevfik Can Keçebaş, Ali Altın, Baha Yaman, Yusuf Ilker Demir, Esin Kocabaş, Coşkun Özdemir, Şahin K. Kocabaş, Aşkın Department of Physics Koç University Sarıyer Istanbul34450 Turkey Bio-Medical Sciences and Engineering Program Koç University Sarıyer Istanbul34450 Turkey Sciences and Engineering Program Harvard University CambridgeMA02138 United States Department of Engineering Science and Mechanics The Pennsylvania State University University ParkPA16802 United States Department of Materials University of Manchester ManchesterM13 9PL United Kingdom Koç University Surface Science and Technology Center Koç University Sarıyer Istanbul34450 Turkey Koç University Research Center for Translational Medicine Koç University Sarıyer Istanbul34450 Turkey

Nonreciprocal interactions break action-reaction symmetry in systems of interacting bodies. This process inevitably introduces non-Hermitian dynamics which with its hallmark signature called exceptional points (EPs) has been a subject of intense research across different disciplines ranging from photonics to metamaterials. Whether non-Hermiticity and EPs are a fundamental property of nature and if so, how nature utilizes them to gain competitive advantage have remained largely unanswered. Although biological systems feature many examples of non-reciprocal interactions with the potential to drive non-Hermitian dynamics, these are often theoretically overlooked and not experimentally investigated. Here, we demonstrate in an active matter composed of social animal Caenorhabditis elegans and bacteria, non-Hermitian dynamics, and the emergence of EPs owing to the nonreciprocal nature of oxygen sensing, nonequilibrium interfacial current, and bacterial consumption. We observed that when driven through the EP, the system collectively breaks parity-time (PT) symmetry leading to traveling waves and arrested phase separation. We further find that these features enable the collective ability to localize interfaces between broken and exact PT-phases. Remarkably, this ability provides a strong evolutionary advantage to animals living in soil. Altogether our results provide mechanistic insights into the detailed symmetries controlling the collective response of biological systems;answer a long-standing problem;and give an example of the EP-enabled dynamics in a biological system. © 2024, CC BY.

关键词： Dynamics

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Reversible Actuation of α-Borophene Nanoscrolls

arXiv

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arXiv 2023年

作者： Fabris, Guilherme S.L. Galvão, D.S. Paupitz, Ricardo Postgraduate Program in Materials Science and Engineering Federal University of Pelotas RS Pelotas96010-610 Brazil Applied Physics Department State University of Campinas SP Campinas13083-970 Brazil Sao Paulo State University - Unesp Physics Department SP Rio ClaroCEP-13506-900 Brazil

In this work, we proposed and investigated the structural and electronic properties of boron-based nanoscrolls (armchair and zigzag) using the DFTB+ method. We also investigated the electroactuation process (injecting and removing charges). A giant electroactuation was observed, but the results show relevant differences between the borophene and carbon nanoscrolls. The molecular dynamics simulations showed that the scrolls are thermally and structurally stable for a large range of temperatures (up to 600K) and the electroactuation process can be easily tuned and can be entirely reversible for some configurations. © 2023, CC BY.

关键词： Molecular dynamics

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