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Symmetry-adapted graph neural networks for constructing molecular dynamics Force fields

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Science China(Physics,Mechanics & Astronomy) 2021年第11期64卷 118-126页

作者： Zun Wang Chong Wang SiBo Zhao ShiQiao Du Yong Xu Bing-Lin Gu WenHui Duan State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Department of Physics Carnegie Mellon UniversityPittsburgh 15213USA Institute for Advanced Study Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Beijing 100084China RIKEN Center for Emergent Matter Science(CEMS) WakoSaitama 351-0198Japan

Molecular dynamics is a powerful simulation tool to explore material properties.Most realistic material systems are too large to be simulated using first-principles molecular dynamics.Classical molecular dynamics has a lower computational cost but requires accurate Force fields to achieve chemical accuracy.In this work,we develop a symmetry-adapted graph neural network framework called the molecular dynamics graph neural network(MDGNN)to construct Force fields automatically for molecular dynamics simulations for both molecules and crystals.This architecture consistently preserves translation,rotation,and permutation invariance in the simulations.We also propose a new feature engineering method that includes high-order terms of interatomic distances and demonstrate that the MDGNN accurately reproduces the results of both classical and first-principles molecular dynamics.In addition,we demonstrate that Force fields constructed by the proposed model have good transferability.The MDGNN is thus an efficient and promising option for performing molecular dynamics simulations of large-scale systems with high accuracy.

关键词： graph neural networks molecular dynamics Force fields

Five-axis flank milling tool path generation with curvature continuity and smooth cutting Force for pockets

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Chinese Journal of Aeronautics 2020年第2期33卷 730-739页

作者： Changqing LIU Yingguang LI Xin JIANG Wenyao SHAO College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In order to ensure machining stability,curvature continuity and smooth cutting Force are very important so as to meet the constraints of both cutting Force and kinematics of machine tools.For five-axis flank milling,it is difficult to meet both of the constraints because tool path points and tool axis vectors interact with each other.In this paper,multiple relationships between tool path points and tool axis vectors with cutting Force and kinematics of machine tools are established,and the strategies of corner-looping milling and clothoidal spirals are combined so as to find feasible solutions under both of the constraints.Tool path parameters are iterated by considering the maximum cutting Force and the feasible range of the tool axis vector,and eventually a curvature continuity five-axis flank milling tool path with smooth cutting Force is generated.Machining experimental results show that the conditions of cutting Force are satisfied,vibration during the process of machining is reduced,and the machining quality of the surface is improved.

关键词： Curvature continuity Cutting Force Five-axis flank milling Machining Tool path generation

Monitoring film coalescence from aqueous polymeric dispersions using atomic Force microscopy: Surface topographic and nano-adhesion studies

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Asian Journal of Pharmaceutical Sciences 2020年第1期15卷 104-111页

作者： Ziyi Yang Duncan QMCraig School of Pharmaceutical Science Jiangnan University1800 Lihu RoadWuxi 214122China UCL School of Pharmacy 29-39 Brunswick SquareLondon WC1N1AXUK

The aim of the investigation was to develop the use of topographic and nano-adhesion atomic Force microscopy(AFM) studies as a means of monitoring the coalescence of latex particles within films produced from a pharmaceutically relevant aqueous dispersion(Eudragit~?NE30 D). Films were prepared via spin coating and analysed using AFM, initially via tapping mode for topographic assessment followed by Force-distance measurements which allowed assessment of site-specific adhesion. The results showed that colloidal particles were clearly observed topographically in freshly prepared samples, with coalescence detected on curing via the disappearance of discernible surface features and a decrease in roughness indices. The effects of temperature and humidity on film curing were also studied, with the former having the most pronounced effect. AFM Force measurements showed that the variation in adhesive Force reduced with increasing curing time, suggesting a novel method of quantifying the rate of film formation upon curing. It was concluded that the AFM methods outlined in this study may be used as a means of qualitatively and quantitatively monitoring the curing of pharmaceutical films as a function of time and other variables, thereby facilitating rational design of curing protocols.

关键词： Film curing Atomic Force microscopy Spin coating Aqueous dispersion AFM pull-off Force measurement

Uniform texture in Al-Zn-Mg alloys using a coupled Force field of electron wind and external load

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Journal of Materials Science & Technology 2020年第1期36卷 149-159页

作者： Hexiong Zhang Xinfang Zhang State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological EngineeringUniversity of Science and Technology BeijingBeijing 100083China

Cylindrical Al-Zn-Mg alloys were processed by electroplastic compression with Forced air cooling.Compared to a simple compression process,an unequal intensity of {110} was obtained,and other textures were eliminated by electroplastic compression,that is,electroplastic compression can promote a uniform texture.The various textures formed in different regions along the radial direction under a simple compression process were illuminated by analyzing the relationship between the crystal rotation and stress state.Furthermore,the interaction between the electrons and dislocations was studied in electroplastic compression.The electrons enhanced {110} by promoting slipping of the dislocations when the Burgers vectors of the dislocations were parallel to the drift direction of the electrons.However,the electrons also inhibited crystal rotation by pinning the dislocations with the Burgers vectors perpendicular to the drift direction of the electrons.Therefore,textures other than {110} have difficulty forming under electroplastic compression.The effect of the current energy on the texture(enhancement or attenuation) was in accordance with the law of conservation.The results provided reasonable explanations for the test phenomena.

关键词： Electroplastic Compression Electron wind Coupled Force field Texture

Influence of fluoroethylene carbonate on the solid electrolyte interphase of silicon anode for Li-ion batteries:A scanning Force spectroscopy study

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Chinese Physics B 2020年第4期29卷 58-66页

作者：郑杰允刘家亮王绥军罗飞贲留斌李泓 Beijing National Laboratory for Condensed Matter Physics.Institute of Physics.Chinese Academy of Sciences Beijing 100190China State Key Laboratory of Operation and Control of Renewable Energy&Storage Systems China Electric Power Research InstituteBeijing 100192China

Silicon is an important high capacity anode material for the next generation Li-ion batteries.The electrochemical performances of the Si anode are influenced strongly by the properties of the solid electrolyte interphase(SEI).It is well known that the addition of flouroethylene carbonate(FEC)in the carbonate electrolyte is helpful to improve the cyclic performance of the Si anode.The possible origin is suggested to relate to the modification of the SEI.However,detailed information is still absent.In this work,the structural and mechanical properties of the SEI on Si thin film anode in the ethylene-carbonate-based(EC-based)and FEC-based electrolytes at different discharging and charging states have been investigated using a scanning atomic Force microscopy Force spectroscopy(AFMFS)method.Single-layered,double-layered,and multi-layered SEI structures with various Young’s moduli have been visualized three dimensionally at nanoscale based on the hundreds of Force curves in certain scanned area.The coverage of the SEI can be obtained quantitatively from the two-dimensional(2D)project plots.The related analysis indicates that more soft SEI layers are covered on the Si anode,and this could explain the benefits of the FEC additive.

关键词： Si fluoroethylene carbonate solid electrolyte interphase atomic Force microscopy Force spectroscopy

Advances in atomic Force microscopy for single-cell analysis

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Nano Research 2019年第4期12卷 703-718页

作者： Mi Li Ning Xi Yuechao Wang Lianqing Liu State Key Laboratory of Robotics Shenyang Institute of Automation Chinese Academy of Sciences Shenyang 110016 China Institutes for Robotics and Intelligent Manufacturing Chinese Academy of Sciences Shenyang 110016 China Department of Industrial and Manufacturing Systems Engineering The University of Hong Kong Hong Kong 999077 China

Single-cell analysis has been considered as a promising way to uncover the underlying mechanisms guiding the mysteries of life activities, which con siderably complements traditio nal en semble assays and yields novel in sights into cell biology. The adve nt of atomic Force microscopy (AFM) provides a potent tool for investigati ng the structures and properties of n ative biological samples at the micro/na no scale un der near-physiological conditions, which promotes the studies of single-cell behaviors. In the past decades, AFM has achieved great success in single-cell observation and manipulation for biomedical applications, demonstrating the excellent capabilities of AFM in addressing biological issues at the single-cell level with unprecedented spatiotemporal resolution. In this article, we review the recent advances in single-cell analysis that has been made with the utilization of AFM, and provide perspectives for future progression.

关键词： atomic Force microscopy single-cell analysis cellular morphology cellular mechanics cellular manipulation

Electron Force-induced dislocations annihilation and regeneration of a superalloy through electrical in-situ transmission electron microscopy observations

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Journal of Materials Science & Technology 2020年第1期36卷 79-83页

作者： Xina Zhang Hongwei Li Mei Zhan Zebang Zheng Jia Gao Guangda Shao State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi'an 710072China

What effect does electric current do on dislocation evolution of metals keeps being a confusing question to be answered and proved. To this end, the dislocation evolution of a superalloy with electric current was directly observed by electrical in-situ transmission electron microscopy in this work. Dislocations annihilation at first and then regeneration was found for the first time, which directly proves the existence of electron Force during the electrically-assisted manufacturing. Dislocations regeneration would be driven by the electron Force and the resistance softening by the local Joule heating effect. Resultantly,a base could be provided for future electrically-assisted research.

关键词： Electron Force Electrical in-situ TEM Local Joule heating effect Dislocation structure evolution

FEM analysis and experimental investigation of Force and chip formation on hot turning of Inconel 625

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Defence Technology（防务技术） 2019年第6期15卷 853-860页

作者： Asit Kumar Parida Kalipada Maity Indian Institute of Technology Delhi Department of Mechanical EngineeringIndia National Institute of Technology Rourkela Department of Mechanical EngineeringIndia

This study investigates the hot machining of Inconel 625 alloy by using flame heating under different machining conditions using finite element analysis(FEM).Turning tests are performed at different cutting speeds and heating temperatures using uncoated carbide insert by DEFORM software.Significant reduction in cutting Force and tool wear has achieved at heating conditions compared to room temperature.Highest tool life is achieved at the highest cutting speed and higher heating temperature condition.At heating conditions of the 600℃ continuous chip is formed whereas at room temperature saw-tooth chip formation is observed.A significant agreement is achieved between simulated and experimental cutting Forces and chip morphology.The effect of feed rates and depth of cuts are also studied experimentally during turning of Inconel 625 in a systematic manner.

关键词： Hot machining Force Inconel 625 Surface roughness Chip morphology

Numerical study of the turbulent channel flow under space-dependent electromagnetic Force control at different Reynolds numbers

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Applied Mathematics and Mechanics(English Edition) 2019年第4期40卷 435-448页

作者： Daiwen JIANG Hui ZHANG Baochun FAN Zijie ZHAO Jian LI Mingyue GUI Science and Technology on Transient Physics Laboratory Nanjing University of Science and Technology Department of Mathematics Imperial College London

In this paper, the control of turbulent channel flow by space-dependent electromagnetic Force and the mechanism of drag reduction are investigated with the direct numerical simulation(DNS) methods for different Reynolds numbers. A formulation is derived to express the relation between the drag and the Reynolds shear stress. With the application of optimal electromagnetic Force, the in-depth relations among characteristic structures in the flow field, mean Reynolds shear stress, and the effect of drag reduction for different Reynolds numbers are discussed. The results indicate that the maximum drag reductions can be obtained with an optimal combination of parameters for each case of different Reynolds numbers. The regular quasi-streamwise vortex structures, which appear in the flow field, have the same period with that of the electromagnetic Force.These structures suppress the random velocity fluctuations, which leads to the absolute value of mean Reynolds shear stress decreasing and the distribution of that moving away from the wall. Moreover, the wave number of optimal electromagnetic Force increases,and the scale of the regular quasi-streamwise vortex structures decreases as the Reynolds number increases. Therefore, the rate of drag reduction decreases with the increase in the Reynolds number since the scale of the regular quasi-streamwise vortex structures decreases.

关键词： flow control drag reduction electromagnetic Force turbulent channel flow