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Towards end-to-end structure determination from x-ray diffraction data using deep learning

npj Computational Materials 2024年第1期10卷 1048-1059页

作者： Gabe Guo Judah Goldfeder Ling Lan Aniv Ray Albert Hanming Yang Boyuan Chen Simon J.L.Billinge Hod Lipson Department of Computer Science Columbia UniversityNew YorkNY10027USA Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY10027USA Department of Mechanical Engineering and Materials Science Duke UniversityDurhamNC27708USA Department of Mechanical Engineering Columbia UniversityNew YorkNY10027USA

Powder crystallography is the experimental science of determining the structure of molecules provided in crystalline-powder form,by analyzing their x-ray diffraction(XRD)*** many materials are readily available as crystalline powder,powder crystallography is of growing usefulness to many ***,powder crystallography does not have an analytically known solution,and therefore the structural inference typically involves a laborious process of iterative design,structural refinement,and domain knowledge of skilled experts.A key obstacle to fully automating the inference process computationally has been formulating the problem in an end-to-end quantitative form that is suitable for machine learning,while capturing the ambiguities around molecule orientation,symmetries,and reconstruction *** we present an ML approach for structure determination from powder diffraction *** works by estimating the electron density in a unit cell using a variational coordinate-based deep neural *** demonstrate the approach on computed powder x-ray diffraction(PXRD),along with partial chemical composition information,as *** evaluated on theoretically simulated data for the cubic and trigonal crystal systems,the system achieves up to 93.4%average similarity(as measured by structural similarity index)with the ground truth on unseen materials,both with known and partially-known chemical composition information,showing great promise for successful structure solution even from degraded and incomplete input *** approach does not presuppose a crystalline structure and the approach are readily extended to other situations such as nanomaterials and textured samples,paving the way to reconstruction of yet unresolved nanostructures.

关键词： structure powder crystalline

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physics guided heat source for quantitative prediction of IN718 laser additive manufacturing processes

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npj Computational Materials 2024年第1期10卷 2854-2867页

作者： Abdullah Al Amin Yangfan Li Ye Lu Xiaoyu Xie Zhengtao Gan Satyajit Mojumder Gregory J.Wagner Wing Kam Liu Department of Mechanical Engineering Northwestern UniversityEvanston 60208 ILUSA Department of Mechanical and Aerospace Engineering University of DaytonDaytonOHUSA Department of Mechanical Engineering University of MarylandBaltimore CountyBaltimoreMD 21250USA Department of Aerospace&Mechanical Engineering University of Texas at El PasoEl PasoTXUSA Theoritical and Applied Mechanics Program Northwestern UniversityEvanston 60208 ILUSA

Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and multiple track laser powder bed fusion process using moving *** in-house developed Additive Manufacturing Computational Fluid Dynamics code(AM-CFD)combined with a cylindrical heat source is implemented to accurately predict these *** heat source calibration is proposed relating volumetric energy density(ψ)based on experiments available in the *** parameters of the heat source of the computational model are initially calibrated based on a Higher Order Proper Generalized Decomposition-(HOPGD)based surrogate *** prediction using the calibrated heat source agrees quantitatively with NIST measurements for different process conditions(laser spot diameter,laser power,and scan speed).A scaling law based on keyhole formation is also utilized in calibrating the parameters of the cylindrical heat source and predicting the challenge *** addition,an improvement on the heat source model is proposed to relate the Volumetric Energy Density(VED_(σ))to the melt pool aspect *** model shows further improvement in the prediction of the experimental measurements for the melt pool,including cases at higher VED_(σ).Overall,it is concluded that the appropriate selection of laser heat source parameterization scheme along with the heat source model is crucial in the accurate prediction of melt pool geometry and thermal measurements while bypassing the expensive computational simulations that consider increased physics equations.

关键词： prediction source additive

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Dual-compressed photoacoustic single-pixel imaging

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National Science Review 2023年第1期10卷 187-195页

作者： Yuning Guo Baowen Li Xiaobo Yin Department of Mechanical Engineering University of Colorado Department of Material Science and Engineering Department of Physics Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Materials Science and Engineering Program University of Colorado

Photoacoustic imaging,an acoustic imaging modality with potentially optical resolution in an optical turbid medium,has attracted great ***,the convergence of wavefront optimization and raster scanning in computational photoacoustic imaging leads to the challenge of fast mapping,especially for a spatial resolution approaching the acoustic deep-subwavelength *** a sparse sampling paradigm,compressive sensing has been applied in numerous fields to accelerate data acquisition without significant quality *** this work,we propose a dual-compressed approach for photoacoustic surface tomography that enables high-efficiency imaging with 3D spatial resolution unlimited by the acoustics in a turbid *** dual-compressed photoacoustic imaging with single-pixel detection,enabled by spatially optical modulation with synchronized temporally photoacoustic coding,allows decoding of the fine optical information from the modulated acoustic signal even when the variance of original photoacoustic signals is *** perform a proof-of-principle numerical demonstration of dual-compressed photoacoustic imaging, that resolves acoustic sub-acoustic-wavelength details with a significantly reduced number of measurements,revealing the potential for dynamic *** dual-compressed concept,which transforms unobtrusive spatial difference into spatio-temporal detectable information,can be generalized to other imaging modalities to re alize efficient,high-spatial-resolution imaging.

关键词： photoacoustic imaging compressive sensing single-pixel imaging surface tomography

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RGB Color-Discriminable Photonic Synapse for Neuromorphic Vision System

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Nano-Micro Letters 2025年第4期17卷 39-62页

作者： Bum Ho Jeong Jaewon Lee Miju Ku Jongmin Lee Dohyung Kim Seokhyun Ham Kyu-Tae Lee Young-Beom Kim Hui Joon Park Department of Organic and Nano Engineering&Human-Tech Convergence Program Hanyang UniversitySeoul 04763Korea Department of Semiconductor Engineering Hanyang UniversitySeoul 04763Korea Department of Mechanical Engineering Hanyang UniversitySeoul 04763Korea Department of Physics Inha UniversityIncheon 22212Korea

To emulate the functionality of the human retina and achieve a neuromorphic visual system,the development of a photonic synapse capable of multispectral color discrimination is of paramount ***,attaining robust color discrimination across a wide intensity range,even irrespective of medium limitations in the channel layer,poses a significant ***,we propose an approach that can bestow the color-discriminating synaptic functionality upon a three-terminal transistor flash memory even with enhanced discriminating *** incorporating the strong induced dipole moment effect at the excitation,modulated by the wavelength of the incident light,into the floating gate,we achieve outstanding RGB color-discriminating synaptic functionality within a remarkable intensity range spanning from 0.05 to 40 mW cm^(-2).This approach is not restricted to a specific medium in the channel layer,thereby enhancing its *** effectiveness of this color-discriminating synaptic functionality is demonstrated through visual pre-processing of a photonic synapse array,involving the differentiation of RGB channels and the enhancement of image contrast with noise ***,a convolutional neural network can achieve an impressive inference accuracy of over 94%for Canadian-Institute-For-Advanced-Research-10 colorful image recognition task after the *** proposed approach offers a promising solution for achieving robust and versatile RGB color discrimination in photonic synapses,enabling significant advancements in artificial visual systems.

关键词： Organic field-effect transistor Photonic synapse Excited-state dipole moment RGB color discrimination Neuromorphic visual system

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Self-consistent Clustering Analysis-Based Moving Morphable Component(SMMC)Method for Multiscale Topology Optimization

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Acta Mechanica Solida Sinica 2023年第6期36卷 884-898页

作者： Yangfan Li Jiachen Guo Hengyang Li Huihan Chen Department of Mechanical Engineering Northwestern UniversityEvanstonIL 60208USA Theoretical and Applied Mechanics Program Northwestern UniversityEvanstonIL 60208USA Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

Current multiscale topology optimization restricts the solution space by enforcing the use of a few repetitive microstructures that are predetermined,and thus lack the ability for structural concerns like buckling strength,robustness,and ***,in this paper,a new multiscale concurrent topology optimization design,referred to as the self-consistent analysis-based moving morphable component(SMMC)method,is *** with the conventional moving morphable component method,the proposed method seeks to optimize both material and structure simultaneously by explicitly designing both macrostructure and representative volume element(RVE)-level *** examples with transducer design requirements are provided to demonstrate the superiority of the SMMC method in comparison to traditional *** proposed method has broad impact in areas of integrated industrial manufacturing design:to solve for the optimized macro and microstructures under the objective function and constraints,to calculate the structural response efficiently using a reduced-order model:self-consistent analysis,and to link the SMMC method to manufacturing(industrial manufacturing or additive manufacturing)based on the design requirements and application areas.

关键词： Topology optimization Moving morphable component method Multiscale concurrent design Reduced-order model

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Machine learning potential assisted exploration of complex defect potential energy surfaces

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npj Computational Materials 2024年第1期10卷 3017-3023页

作者： Chao Jiang Chris A.Marianetti Marat Khafizov David H.Hurley Computational Mechanics and Materials Department Idaho National LaboratoryIdaho FallsID 83415USA Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY 10027USA Department of Mechanical and Aerospace Engineering The Ohio State UniversityColumbusOH 43210USA Materials Science and Engineering Department Idaho National LaboratoryIdaho FallsID 83415USA

Atomic-scale defects generated in materials under both equilibrium and irradiation conditions can significantly impact their physical and mechanical *** the energetically most favorable ground-state configurations of these defects is an important step towards the fundamental understanding of their influence on the performance of materials ranging from photovoltaics to advanced nuclear ***,using fluorite-structured thorium dioxide(ThO_(2))as an exemplar,we demonstrate how density functional theory and machine learning interatomic potential can be synergistically combined into a powerful tool that enables exhaustive exploration of the large configuration spaces of small point defect *** study leads to several unexpected discoveries,including defect polymorphism and ground-state structures that defy our physical *** physical origins of these unexpected findings are elucidated using a local cluster expansion model developed in this work.

关键词： properties defect potential

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Our Role in Solving Global Challenges: An Opinion

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JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 2024年第31期146卷 21193-21195页

作者： Carter, Emily A. Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics and the Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544-5263 United States Princeton Plasma Physics Laboratory Princeton New Jersey 08540-6655 United States

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Oscillatory Hall effect from magnetoelectronic coupling in flexoelectronic silicon

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Physical Review B 2024年第8期109卷 L081113-L081113页

作者： Paul C. Lou Ravindra G. Bhardwaj Anand Katailiha W. P. Beyermann Sandeep Kumar Department of Mechanical Engineering University of California Riverside California 92521 USA Department of Physics and Astronomy University of California Riverside California 92521 USA Materials Science and Engineering Program University of California Riverside California 92521 USA

Magnetoelectronic coupling can be defined as cross-domain coupling between electronic and magnetic properties, where modulation in magnetic properties changes the electronic properties. In this Letter, explicit experimental evidence of magnetoelectronic coupling is presented, which is uncovered from the oscillatory Hall effect response in Hall measurement. The strain gradient in a MgO (1.8 nm)/p-Si (∼400 nm) freestanding sample leads to transfer of electrons (∼5×1018cm−3) from valence to conduction band due to flexoelectronic charge separation in the p-Si layer. The resulting flexoelectronic polarization gives rise to the temporal magnetic moment from dynamical multiferroicity. The external magnetic field changes the net temporal magnetic moment, which causes modulations in charge carrier concentration and oscillatory Hall effect. The period of oscillatory Hall response is 1.12 T, which is attributed to the magnitude of the temporal magnetic moment. The discovery of the oscillatory Hall effect adds another member to the family of Hall effects.

关键词： Hall effect Doped semiconductors Electronically polarized systems Flexoelectrics Multiferroics Hall bar

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Translation of a sphere towards a rigid plane in an Oldroyd-B fluid

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Physical Review Fluids 2024年第8期9卷 083303页

作者： Tachin Ruangkriengsin Rodolfo Brandão Bimalendu Mahapatra Evgeniy Boyko Howard A. Stone Program in Applied and Computational Mathematics Department of Mechanical and Aerospace Engineering Faculty of Mechanical Engineering

We analyze the low-Reynolds-number translation of a sphere towards or away from a rigid plane in an Oldroyd-B fluid under two scenarios: prescribing the sphere's translational velocity, and prescribing the force on the sphere. Leveraging the lubrication approximation and a perturbation expansion in powers of the Deborah number, we develop a comprehensive theoretical analysis that yields analytical approximations for velocity fields, pressures, and forces acting on the sphere. Our framework aids in understanding temporal microstructural changes as the particle-wall gap evolves over time. In particular, we show that alterations in the polymer conformation tensor in response to geometric changes induce additional forces on the sphere. For cases with prescribed velocity, we present a theoretical approach for calculating resistive forces at any order in the Deborah number and utilize a reciprocal theorem to obtain higher-order corrections based on velocity fields in the previous orders. When the sphere translates with a constant velocity, the fluid viscoelasticity decreases the resistive force at the first order. However, at the second-order correction, the direction of the sphere's movement determines whether viscoelasticity increases or decreases the resistive force. For cases with prescribed force, we show that understanding the influence of viscoelasticity on the sphere's translational velocity necessitates a more intricate analysis even at low Deborah numbers. Specifically, we introduce an ansatz for constant force scenarios, and we derive solution forms for general prescribed forces using the method of multiple scales. We find that when a sphere undergoes sedimentation due to its own weight, the fluid viscoelasticity results in a slower settling process, reducing the leading-order sedimentation rate.

关键词： Complex fluids Low Reynolds number flows Lubrication theory Polymer conformation changes Rheology

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Hydrodynamics of molecular rotors in lipid membranes

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Physical Review Fluids 2025年第4期10卷 L041101-L041101页

作者： Vinny Chandran Suja Naomi Oppenheimer Howard A. Stone School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA School of Physics and Astronomy and the Center for Physics and Chemistry of Living Systems Tel Aviv University Tel Aviv 6997801 Israel Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA

Molecular rotors form twisted conformations upon photoexcitation, with their fluorescence relaxation time serving as a measure of viscosity. They have been used to assess membrane viscosities but yield higher values compared to other methods. Here, we show that the rotor's relaxation time is influenced by a combination of membrane viscosity and interleaflet friction. We present a theory for the relaxation time and obtain a correction factor that accounts for the discrepancy. If the membrane's viscosity is known, molecular rotors may enable the extraction of the elusive interleaflet friction.

关键词： Viscosity

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