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Data-driven discovery of the governing equations for transport in heterogeneous media by symbolic regression and stochastic optimization

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Physical Review E 2023年第1期107卷 L013301-L013301页

作者： Jinwoo Im Felipe P. J. de Barros Sami Masri Muhammad Sahimi Robert M. Ziff Sonny Astani Department of Civil and Environmental Engineering University of Southern California Los Angeles California 90089 USA Mork Family Department of Chemical Engineering and Materials Science University of Southern California Los Angeles California 90089-1211 USA Michigan Center for Theoretical Physics and Department of Chemical Engineering University of Michigan Ann Arbor Michigan 48109 USA

With advances in instrumentation and the tremendous increase in computational power, vast amounts of data are becoming available for many complex phenomena in macroscopically heterogeneous media, particularly those that involve flow and transport processes, which are problems of fundamental interest that occur in a wide variety of physical systems. The absence of a length scale beyond which such systems can be considered as homogeneous implies that the traditional volume or ensemble averaging of the equations of continuum mechanics over the heterogeneity is no longer valid and, therefore, the issue of discovering the governing equations for flow and transport processes is an open question. We propose a data-driven approach that uses stochastic optimization and symbolic regression to discover the governing equations for flow and transport processes in heterogeneous media. The data could be experimental or obtained by microscopic simulation. As an example, we discover the governing equation for anomalous diffusion on the critical percolation cluster at the percolation threshold, which is in the form of a fractional partial differential equation, and agrees with what has been proposed previously.

关键词： Diffusion Percolation Stochastic inference Differential equations Diffusion & random walks Genetic algorithm

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Statistical Approach Based on the Stoner‒Wohlfarth Model for Switching Field in Misoriented Magnets Arrays

SSRN

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SSRN 2023年

作者： Lee, Donghyeon Han, Donghyeon Ippei, Suzuki Yukiko, Takahashi Park, Jungmin Kim, Sanghoon Department of Physics University of Ulsan Ulsan44610 Korea Republic of Materials Science and Engineering KAIST Daejeon34141 Korea Republic of Tsukuba305-0017 Japan Department of Physics KAIST Daejeon34141 Korea Republic of Japan

Stoner‒Wohlfarth model (S‒W model) is appreciate to explain the relationship between the external magnetic field and the magnetization reversal of a single magnetic domain. However, it is inappropriate for inhomogeneous magnetic films or bulk materials, such as granular and defective films, because the magnetization reversal of the films is affected by magnetic particles or grains which could have a different anisotropy for uniaxial magnetic anisotropy (UMA) of the films. In this paper, we propose a model based on the S‒W model to understand the magnetization switching behavior of magnetic films with misoriented grains. Our model considers the distribution effect of different anisotropies originating from magnetic defects or domains against the UMA of a magnetic thin film, and a Gaussian function is employed for the probability distribution of tilted anisotropy. Finally, we experimentally demonstrate that our model describes the magnetic switching behavior of a granular magnetic film (FePt-C) with perpendicular magnetic anisotropy. This study provides a new analytical method for the magnetization reversal in magnetic devices. © 2023, The Authors. All rights reserved.

关键词： Probability distributions

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Analysis of Dirac exceptional points and their isospectral Hermitian counterparts

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Physical Review B 2023年第10期107卷 104106-104106页

作者： Jose H. D. Rivero Liang Feng Li Ge Department of Materials Science and Engineering University of Pennsylvania Philadelphia Pennsylvania 19104 USA Department of Physics and Astronomy College of Staten Island CUNY Staten Island New York 10314 USA The Graduate Center CUNY New York New York 10016 USA

Recently, a Dirac exceptional point (EP) was reported in a non-Hermitian system. Unlike a Dirac point in Hermitian systems, this Dirac EP has coalesced eigenstates in addition to the degenerate energy. Also different from a typical EP, the two energy levels connected at this Dirac EP remain real in its vicinity and display a linear instead of square root dispersion, forming a tilted Dirac cone in the hybrid space consisting of a momentum dimension and a synthetic dimension for the strength of non-Hermiticity. In this paper, we first present simple three-band and two-band matrix models with a Dirac EP, where the linear dispersion of the tilted Dirac cone can be expressed analytically. Importantly, our analysis also reveals that there exist Hermitian and non-Hermitian systems that have the same (real-valued) energy spectrum in their entire parameter space, with the exception that one or more degeneracies in the former are replaced by Dirac EPs in the latter. Finally, we show the existence of an imaginary Dirac cone with an EP at its center.

关键词： PT-symmetric quantum mechanics Non-Hermitean systems Optical microcavities

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Magnetic dynamics of two-dimensional itinerant ferromagnet Fe_(3)GeTe_(2)

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Chinese physics B 2021年第9期30卷 506-512页

作者： Lijun Ni Zhendong Chen Wei Li Xianyang Lu Yu Yan Longlong Zhang Chunjie Yan Yang Chen Yaoyu Gu Yao Li Rong Zhang Ya Zhai Ronghua Liu Yi Yang Yongbing Xu Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and EngineeringNanjing UniversityNanjing 210093China Jiangsu Provincial Key Laboratory for Nanotechnology School of PhysicsNanjing UniversityNanjing 210093China Department of Physics Southeast UniversityNanjing 211189China York-Nanjing Joint Centre for Spintronics and NanoEngineering Department of Electronic EngineeringUniversity of YorkYork YO105DDUnited Kingdom Jiangsu Key Laboratory of Opto-Electronic Technology Center for Quantum Transport and Thermal Energy ScienceSchool of Physics and TechnologyNanjing Normal UniversityNanjing 210023China

Among the layered two-dimensional ferromagnetic materials(2D FMs),due to a relatively high T_(C),the van der Waals(vdW)Fe_(3)GeTe_(2)(FGT)crystal is of great importance for investigating its distinct magnetic ***,we have carried out static and dynamic magnetization measurements of the FGT crystal with a Curie temperature TC≈204 *** M-H hysteresis loops with in-plane and out-of-plane orientations show that FGT has a strong perpendicular magnetic anisotropy with the easy axis along its ***,we have calculated the uniaxial magnetic anisotropy constant(K_(1))from the SQUID *** dynamic magnetic properties of FGT have been probed by utilizing the high sensitivity electron-spin-resonance(ESR)spectrometer at cryogenic *** on an approximation of single magnetic domain mode,the K_(1)and the effective damping constant(αeff)have also been determined from the out-of-plane angular dependence of ferromagnetic resonance(FMR)spectra obtained at the temperature range of 185 K to T_(C).We have found large magnetic damping with the effective damping constantαeff~0.58 along with a broad linewidth(ΔH_(pp)>1000 Oe at 9.48 GHz,H||c-axis).Our results provide useful dynamics information for the development of FGT-based spintronic devices.

关键词： two-dimensional ferromagnet ferromagnetic resonance magnetic anisotropy magnetic damping

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Synaptic-Like Plasticity in 2D Nanofluidic Memristor from Competitive Bicationic Transport

arXiv

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arXiv 2024年

作者： Noh, Yechan Smolyanitsky, Alex Department of Physics University of Colorado Boulder BoulderCO80309 United States Applied Chemicals and Materials Division National Institute of Standards and Technology BoulderCO80305 United States Department of Materials Science and Engineering University of California Berkeley BerkeleyCA94720 United States

Synaptic plasticity, the dynamic tuning of signal transmission strength between neurons, serves as a fundamental basis for memory and learning in biological organisms. This adaptive nature of synapses is considered one of the key features contributing to the superior energy efficiency of the brain. In this study, we utilize molecular dynamics simulations to demonstrate synaptic-like plasticity in a subnanoporous 2D membrane. We show that a train of voltage spikes dynamically modifies the membrane’s ionic permeability in a process involving competitive bicationic transport. This process is shown to be repeatable after a given resting period. Due to a combination of sub-nm pore size and the atomic thinness of the membrane, this system exhibits energy dissipation of 0.1–100 aJ per voltage spike, which is several orders of magnitude lower than 0.1–10 fJ per spike in the human synapse. We reveal the underlying physical mechanisms at molecular detail and investigate the local energetics underlying this apparent synaptic-like behavior. Copyright © 2024, The Authors. All rights reserved.

关键词： Molecular dynamics

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Charge-Induced Aggregation of Emulsified Oil Droplets in Water with Presence of Functionalized Stainless Steel Felt

SSRN

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SSRN 2024年

作者： Li, Qian-Ru Wang, Xin-Yi Yasin, Akram Qi, Ting-Yong Liu, Xuqing Mao, Zhexin Ma, Peng-Cheng Laboratory of Environmental Science and Technology The Xinjiang Technical Institute of Physics and Chemistry Key Laboratory of Functional Materials and Devices for Special Environments Chinese Academy of Sciences Urumqi830011 China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Science Beijing100049 China School of Materials Science and Engineer Xinjiang University Urumqi830017 China State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal Materials School of Materials Science and Engineering Northwestern Polytechnical University Shanxi Xi’an710072 China Department of Materials University of Manchester ManchesterM13 9PL United Kingdom

Oil-water mixtures, especially the surfactant-stabilized oil-in-water emulsions with high stability, are causing great difficulties for effective separation. In this work, a modification strategy was proposed to prepare functionalized stainless steel felt for emulsion separation by coating the felt with 3-triethoxysilylpropylamine, followed by the introduction of silica nanoparticles using a sulfur-based three-component coupling reaction. To satisfy the pore size requirement for effective emulsion separation, the developed felt was processed using a compression molding. With special wettability, optimized pore size, and electrostatic demulsification mechanism, the positive charged felt delivered outstanding separation capabilities for oil-in-water emulsions stabilized by various surfactants. Specifically, the flux and COD removal efficiency for the anionic-stabilized emulsion were up to 3911 L/m2/h and 95.3%, while for cationic-stabilized emulsions, which were 1305 L/m2/h and 93.1%. The results indicated that surface charges played an important role in governing the separation performance of the felt, and the electrostatic attraction demulsification demonstrated better separation capabilities than that from the electrostatic repulsion process. © 2024, The Authors. All rights reserved.

关键词： Electrostatics

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Accurate and precise quantum computation of valence two-neutron systems

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Physical Review C 2024年第6期109卷 064305-064305页

作者： Sota Yoshida (吉田聡太) Takeshi Sato (佐藤健) Takumi Ogata (緒方拓巳) Tomoya Naito (内藤智也) Masaaki Kimura (木村真明) Institute for Promotion of Higher Academic Education School of Data Science and Management for Accelerator-based Science RIKEN Wako 351-0198 Japan Graduate School of Engineering Photon Science Center School of Engineering Research Institute for Photon Science and Laser Technology RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) RIKEN 2-1 Hirosawa Wako 351-0198 Japan Department of Physics Graduate School of Science

Developing methods to solve nuclear many-body problems with quantum computers is an imperative pursuit within the nuclear physics community. Here, we introduce a quantum algorithm to accurately and precisely compute the ground state of valence two-neutron systems leveraging presently available noisy intermediate-scale quantum devices. Our focus lies on the nuclei having a doubly magic core plus two valence neutrons in the p, sd, and pf shells, i.e., He6, O18, and Ca42, respectively. Our ansatz, quantum circuit, is constructed in the pair-wise form, taking into account the symmetries of the system in an explicit manner, and enables us to reduce the number of qubits and the number of CNOT gates required. The results on a real quantum hardware by IBM Quantum Platform show that the proposed method gives very accurate results of the ground-state energies, which are typically within 0.1% error in the energy for He6 and O18 and at most 1% error for Ca42. Furthermore, our experiments using real quantum devices also show the pivotal role of the circuit layout design, attuned to the connectivity of the qubits, in mitigating errors.

关键词： Nuclear many-body theory Quantum simulation Shell model

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Power-efficient optical bottle-beam traps

Power-efficient optical bottle-beam traps

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CLEO: science and Innovations, S and I 2022

作者： Xiao, Yuzhe Yu, Zhaoning Wambold, Raymond A. Mei, Hongyan Hickman, Garrett Goldsmith, Randall H. Saffman, Mark Kats, Mikhail A. Department of Electrical and Computer Engineering University of Wisconsin-Madison MadisonWI53706 United States Department of Physics University of Wisconsin-Madison MadisonWI53706 United States Department of Chemistry University of Wisconsin-Madison MadisonWI53706 United States Materials Science and Engineering University of Wisconsin-Madison MadisonWI53706 United States

We introduced a figure of merit for optical bottle-beam traps, and identified optical bottle-beam traps based on metasurfaces illuminated by a Gaussian beam that are superior in terms of power efficiency compared to e... 详细信息

ISBN: (纸本)9781557528209

关键词： Gaussian beams

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Second harmonic Bessel-Gauss beam shaping with elliptic axicon aberrations

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Physical Review Research 2025年第1期7卷 013012-013012页

作者： Tianhong Wang Finn Buldt Pascal Bassène Saad Bin Ali Reza Edwin Fohtung Thomas A. Searles Chiu Tai Law Moussa N'Gom Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute (RPI) Troy New York 12180 USA The Shirley Ann Jackson Ph.D. Center for Biotechnology and Interdisciplinary Studies RPI Troy New York 12180 USA Center for Materials Devices and Integrated Systems (CMDIS) Low center RPI Troy New York 12180 USA Electrical Computer and Systems Engineering Department RPI Troy New York 12180 USA Department of Materials Science and Engineering RPI Troy New York 12180 USA Department of Electrical and Computer Engineering University of Illinois Chicago Chicago Illinois 60607 USA Electrical Engineering and Computer Science Department University of Wisconsin Milwaukee Wisconsin 53201 USA Center for Ultrafast Optical Science University of Michigan Ann Arbor Michigan 48109-2102 USA

The second harmonic (SH) of an axicon generated Bessel-Gauss beam is created through the nonlinear interaction of photons with a crystal, resulting in the energy doubling of the output photons. In this work, we show experimentally that in addition to frequency doubling, the SH of Bessel-Gauss beams under asymmetric aberrations from an elliptic axicon exhibit intriguing beam formation. Particularly, the central region of the SH beam profile is composed of two central spots of various geometries surrounded by nested ellipses; one of which is the configuration of two central gamma dots with similar radius knotted by nested ellipses for a zeroth-order Bessel-Gauss pump. These SH beams consistently maintain their spatial profile throughout propagation, reminiscing the behavior of screw dislocations in wave patterns. Our numerical simulations produce beam dynamics consistent with that of experiments and further implicate the remarkable interweaving of bright spots with dark vortices. This is especially noticeable when the beams dynamically oscillate along the optical axis, resulting in the genesis of spatially polarized beams with a knotted framework. The insights gained from our study establish a novel paradigm for exploring interactions of Bessel-like beams with vortex dynamics. This, in turn, has the potential to spark innovations in optical applications, fostering new methodologies to harness and manipulate complex light structures. Our experimental findings could spur new methods of generating logical states of light and new opportunities for material processing control.

关键词： Aberrations

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From Micropores to Ultra-micropores inside Hard Carbon: Toward Enhanced Capacity in Room-/ Low-Temperature Sodium-Ion Storage

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Nano-Micro Letters 2021年第6期13卷 297-310页

作者： Jinlin Yang Xiaowei Wang Wenrui Dai Xu Lian Xinhang Cui Weichao Zhang Kexin Zhang Ming Lin Ruqiang Zou Kian Ping Loh Quan-Hong Yang Wei Chen Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityBinhai New CityFuzhou 350207People’s Republic of China Department of Chemistry National University of Singapore3 Science Drive 3Singapore 117543Singapore National University of Singapore(Suzhou)Research Institute 377 Lin Quan StreetSuzhou Industrial ParkSuzhou 215123JiangsuChina Department of Physics National University of Singapore2 Science Drive 3Singapore 117542Singapore Nanoyang Group State Key Laboratory of Chemical EngineeringSchool of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350People’s Republic of China Beijing Key Laboratory for Theory and Technology of Advanced Battery Materials Department of Materials Science and EngineeringCollege of EngineeringPeking UniversityBeijing 100871People’s Republic of China Institute of Materials Research and Engineering(IMRE) Agency of ScienceTechnologyand Research(A*STAR)3 Research LinkSingapore 117602Singapore

Pore structure of hard carbon has a fundamental influence on the electrochemical properties in sodium-ion batteries(SIBs).Ultra-micropores(1 nm)inside carbon into ultra-micropores(<0.5 nm).Consequently,the designed... 详细信息

Pore structure of hard carbon has a fundamental influence on the electrochemical properties in sodium-ion batteries(SIBs).Ultra-micropores(<0.5 nm)of hard carbon can function as ionic sieves to reduce the diffusion of slovated Na+but allow the entrance of naked Na^(+) into the pores,which can reduce the interficial contact between the electrolyte and the inner pores without sacrificing the fast diffusion ***,a molten diffusion-carbonization method is proposed to transform the micropores(>1 nm)inside carbon into ultra-micropores(<0.5 nm).Consequently,the designed carbon anode displays an enhanced capacity of 346 mAh g^(−1) at 30 mA g^(−1) with a high ICE value of~80.6%and most of the capacity(~90%)is below 1 ***,the high-loading electrode(~19 mg cm^(−2))exhibits a good temperature endurance with a high areal capacity of 6.14 mAh cm^(−2) at 25℃ and 5.32 mAh cm^(−2) at −20℃.Based on the in situ X-ray diffraction and ex situ solid-state nuclear magnetic resonance results,the designed ultra-micropores provide the extra Na+storage sites,which mainly contributes to the enhanced *** proposed strategy shows a good potential for the development of high-performance SIBs.

关键词： Carbon anode Ultra-micropores Extra sodium-ion storage sites Low-voltage capacity High areal capacity

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