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Neon-concentration dependent retarding effect on the recrystallization of irradiated tungsten:Experimental analysis and molecular dynamics simulation

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Journal of Materials science & Technology 2023年第8期139卷 245-259页

作者： Ting Wang Xiaoyang Wang Xiaolei Ma Long Cheng Yue Yuan Wangguo Guo Ke Xu Mi Liu Ziyang Xie Liping Guo Guang-Hong Lu School of Physics Beihang UniversityBeijing 100191China Beijing Key Laboratory of Advanced Nuclear Materials and Physics Beihang UniversityBeijing 100191China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Institute of Nuclear Materials University of Science&Technology BeijingBeijing 100083China Institute of High Energy Physics Chinese Academy of ScienceBeijing 100049China School of Physics and Technology Wuhan UniversityWuhan 430072China

Recrystallization is a critical issue in ITER and future fusion devices as it strongly deteriorates the prop-erties and serving life of tungsten divertor *** this work,we investigated the influence of neon on the recrystallization behavior of tungsten and its underlying mechanism by both experimental anal-ysis and molecular dynamics *** tungsten was irradiated by neon ion with energies of 10 and 100 keV and fluences of 1×10^(18)-1×10^(20)m^(−2),followed by isochronal annealing at various temperatures(1473-2073 K)for 1 *** results indicate that 10 keV neon ion irradiation slightly in-hibits tungsten recrystallization due to the shallow depth distribution of neon(35 nm),whereas 100 keV neon ion irradiation exerts a significant retarding effect on tungsten recrystallization when neon con-centration reaches∼102 *** boundaries can hardly move with neon concentration reaching 400 appm,above which the retarding effect is very strong and varies *** retarded recrystallization is mainly attributed to the pinning effect of neon clusters/bubbles on the grain boundary movement dur-ing *** neon clusters are found to play a predominant role in the retarding effect and the un-clustered neon atoms show a very limited effect on the grain boundary *** comparing the neon effects on recrystallization in this work and helium effects reported in the literature,we found that helium exhibits a relatively stronger recrystallization retarding effect than *** is because helium is more easily to diffuse into grain boundaries and form larger clusters due to its high diffusivity and low self-trapping energy in tungsten,which can greatly impede the migration of grain *** work provides a fundamental insight into the neon-concentration dependent recrystallization retarding effect in tungsten and the corresponding underlying atomic-level mechanisms.

关键词： Tungsten Recrystallization Neon clusters Neon nano-bubbles Grain boundary

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Learning Graph Representation via Graph Entropy Maximization 41

Learning Graph Representation via Graph Entropy Maximization

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41st International Conference on Machine Learning, ICML 2024

作者： Sun, Ziheng Wang, Xudong Ding, Chris Fan, Jicong School of Data Science The Chinese University of Hong Kong Shenzhen [CUHK-Shenzhen China Shenzhen International Center for Industrial and Applied Mathematics Shenzhen Research Institute of Big Data Shenzhen China

Graph representation learning aims to represent graphs as vectors that can be utilized in downstream tasks such as graph classification. In this work, we focus on learning diverse representations that can capture the graph information as much as possible. We propose quantifying graph information using graph entropy, where we define a probability distribution of a graph based on its nodes’ representations and global-graph representation. However, the computation of graph entropy is NP-hard due to the complex vertex-packing polytope involved in its definition. To address this challenge, we provide an approximation method leveraging orthonormal representations for graph entropy maximization. The proposed method is implemented via graph neural networks, resulting in informative node-level and graph-level representations. Experimental results demonstrate the effectiveness of our method in comparison to many baselines in unsupervised learning and semi-supervised learning tasks. The code of our method is available at https://***/MathAdventurer/GeMax. Copyright 2024 by the author(s)

关键词： Contrastive Learning

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A Parallel Finite-Difference Time-Domain Framework on Heterogeneous Supercomputing Platforms 10

A Parallel Finite-Difference Time-Domain Framework on Hetero...

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10th IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, MAPE 2024

作者： Li, Yue Lu, Qiran Li, Hanyu Zhou, Haijing Li, Mengmeng Ding, Dazhi School of Microelectronics School of Integrated Circuits Nanjing University of Science and Technology Nanjing China Institute of Applied Physics and Computational Mathematics Beijing China

ISBN: (纸本)9798331533922

This paper proposes a parallel framework for the Finite-Difference Time-Domain (FDTD) method on heterogeneous supercomputing platforms. The main content covers MPI parallelism, heterogeneous communication, and heterogeneous parallel acceleration. Compared to traditional MPI-based process parallel frameworks, this framework effectively leverages the characteristics of heterogeneous supercomputers. Numerical simulations validate the efficiency of the proposed method. © 2024 IEEE.

关键词： Time domain analysis

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On von Neumann Regularity of Commutators

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Algebra Colloquium 2024年第2期31卷 181-198页

作者： Nam Kyun Kim Tai Keun Kwak Yang Lee Sung Ju Ryu Nanqing Ding School of Basic Sciences Hanbat National UniversityDaejeon 34158Korea Department of Data Science Daejin UniversityPocheon 11159Korea Department of Mathematics Yanbian UniversityYanjiJilin 133002China Institute for Applied Mathematics and Optics Hanbat National University Daejeon 34158Korea Department of Mathematics Pusan National UniversityBusan 46241Korea 不详

We study the structure of rings which satisfy the von Neumann regularity of commutators,and call a ring R C-regularif ab-ba ∈(ab-ba)R(ab-ba)for all a,b in *** a C-regular ring R,we prove J(R[X])=N^(*)(R[X])=N^(*)(R)[X]=W(R)[X]■Z(R[X]),where J(A),N^(*)(A),W(A),Z(A)are the Jacobson radical,upper nilradical,Wedderburn radical,and center of a given ring A,respectively,and A[X]denotes the polynomial ring with a set X of commuting indeterminates over A;we also prove that R is semiprime if and only if the right(left)singular ideal of R is *** provide methods to construct C-regular rings which are neither commutative nor von Neumann regular,from any given ***,for a C-regular ring R,the following are proved to be equivalent:(i)R is Abelian;(ii)every prime factor ring of R is a duo domain;(ii)R is quasi-duo;and(iv)R/W(R)is reduced.

关键词： C-regular ring commutator regular ring commutative ring radical singular ideal

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An Iterative Thresholding Method for the Minimum Compliance Problem

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Communications in Computational physics 2023年第4期33卷 1189-1216页

作者： Luyu Cen Wei Hu Dong Wang Xiaoping Wang Department of Mathematics Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina The Program in Applied and Computational Mathematics Princeton UniversityPrincetonNew JerseyUSA School of Science and Engineering The Chinese University of Hong KongShenzhenGuangdong 518172China Shenzhen International Center for Industrial and Applied Mathematics Shenzhen Research Institute of Big DataGuangdong 518172China

In this paper,we propose a simple energy decaying iterative thresholding algorithm to solve the two-phase minimum compliance *** material domain is implicitly represented by its characteristic function,and the problem is formulated into a minimization problem by the principle of minimum complementary *** prove that the energy is decreasing in each *** effective continuation schemes are proposed to avoid trapping into the local *** results on 2D isotropic linear material demonstrate the effectiveness of the proposed methods.

关键词： Minimum compliance convolution thresholding linear elasticity

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Full-scale ab initio simulations of laser-driven atomistic dynamics

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npj Computational Materials 2023年第1期9卷 190-196页

作者： Qiyu Zeng Bo Chen Shen Zhang Dongdong Kang Han Wang Xiaoxiang Yu Jiayu Dai College of Science National University of Defense Technology410073 ChangshaHunanChina Hunan Key Laboratory of Extreme Matter and Applications National University of Defense Technology410073 ChangshaChina Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics100088 BeijingChina

The coupling of excited states and ionic dynamics is the basic and challenging point for the materials response at extreme *** the laboratory,the intense laser produces transient nature and complexity with highly nonequilibrium states,making it extremely difficult and interesting for both experimental measurements and theoretical *** the inclusion of laser-excited states,we extend an ab initio method into the direct simulations of whole laser-driven microscopic dynamics from solid to *** construct the framework of combining the electron-temperature-dependent deep neural-network potential energy surface with a hybrid atomistic-continuum approach,controlling non-adiabatic energy exchange and atomistic dynamics,which enables consistent interpretation of experimental *** large-scale ab initio simulations,we demonstrate that the nonthermal effects introduced by hot electrons play a dominant role in modulating the lattice dynamics,thermodynamic pathway,and structural *** highlight that the present work provides a path to realistic computational studies of laser-driven processes,thus bridging the gap between experiments and simulations.

关键词： dynamics excited bridging

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New Results on Interval Type-3 Fuzzy Control for Nonlinear Time-Delay Systems Using Convex Relaxation Technique

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IEEE Transactions on Systems, Man, and Cybernetics: Systems 2025年第5期55卷 3630-3641页

作者： Harikaran, B. Harshavarthini, S. Lee, Sangmoon Sakthivel, R. Sathiyaraj, T. School of Advanced Sciences Department of Mathematics Chennai600127 India Kyungpook National University School of Electronic and Electrical Engineering Daegu41566 Korea Republic of Bharathiar University Department of Applied Mathematics Coimbatore641046 India Institute of Actuarial Science and Data Analytics UCSI University Kuala Lumpur56000 Malaysia

In this article, the interval type-3 fuzzy-based state feedback control is proposed for the stabilization problem of interval type-3 fuzzy systems (IT3FSs) subject to time-varying delay. Specifically, to improve the model accuracy and control capabilities, we proposed a nonparallel distributed compensation-based controller approach, be precise, the system and controller adopts the distinct membership functions. Moreover, the stability analysis of IT3FSs in the state space form is studied newly in this article. Besides the primary membership function that exists for interval type-2 fuzzy systems (IT2FSs), the IT3FSs possess the secondary membership function to handle the overall uncertainty which enacts the superiority of the proposed work. Notably, the adequate stability criteria are derived in the form of linear matrix inequality (LMI) using the Lyapunov stability theorem. Additionally, the convex relaxation technique is used to strengthen the design flexibility and achieve the faster convergence rate, which converts an optimization problem with a vector variable to a convex program with a matrix variable, via a lifting technique. A noteworthy aspect is that the application of the convex relaxation technique in the context of IT3FSs is proposed for the first time in literature. Finally, the comparative results between IT2FSs and IT3FSs are shown via two illustrative examples, including the inverted-pendulum model, to underscore the efficacy and practical implementations of the developed control methodology. © 2013 IEEE.

关键词： Membership functions

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Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains

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Chinese physics B 2023年第3期32卷 205-211页

作者：梁畅通张晶晶李鹏程 Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of the Ministry of Education Shantou UniversityShantou 515063China Institute of Applied Physics and Computational Mathematics Beijing 100088China

Frequency-comb emission via high-order harmonic generation(HHG)provides an alternative method for the coherent vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)radiation at ultrahigh repetition *** particular,the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission *** we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse *** find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG,leading to suppression and enhancement of frequency-comb *** results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via *** dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in *** results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV–XUV regimes.

关键词： high-order harmonic generation frequency comb time-dependent Schro¨dinger equation intense laser field systems

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Multiphase equation of state for magnesium based on first-principles simulations

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Physical Review B 2024年第22期110卷 224107-224107页

作者： Li-Ting Li Xing-Yu Gao Hai-Feng Liu Jia-Wei Xian Fu-Yang Tian Hai-Feng Song National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China Institute for Applied Physics University of Science and Technology Beijing Beijing 100083 China

We perform first-principles simulations to construct a multiphase equation of state (EOS) for magnesium (Mg) up to a pressure-temperature (P−T) range of 600 GPa and 8000 K. The phases considered include the solid hexagonal close-packed (hcp) and body-centered cubic (bcc) phases and the liquid phase. The effects of lattice anharmonicity on the free energies of the solid phases are considered using the phonon quasiparticle method, which is a hybrid approach that combines first-principles molecular dynamics (FPMD) and harmonic phonons to address lattice anharmonicity. These effects are found to significantly increase the calculated hcp-bcc transition pressure at high temperatures by >10% at T>1000 K and >20% at T>1250 K, leading to an hcp-bcc phase line in good overall agreement with static measurements. The free energies of the liquid phase are fitted using the results of FPMD simulations of this phase and constrained by our previous melting curve calculated from FPMD using the solid-liquid coexistence method. The resulting melting curve from our EOS reproduces the anomalous behavior of reentrant melting above ∼300 GPa from our previous calculations and shows better agreement with the results from shock experiments than with static measurements at high pressures. Our EOS places the hcp-bcc-liquid triple point at 25 GPa and 2030 K, higher in pressure and temperature than those from previous first-principles studies based on the quasiharmonic approximation (QHA). Comparisons are also made with other experimental data, including those from various static and shock experiments and generally indicate a high level of consistency.

关键词： Free energy

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A continuous symmetry breaking measure for finite clusters using Jensen-Shannon divergence

arXiv

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arXiv 2024年

作者： Lan, Ling Du, Qiang Billinge, Simon J.L. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Department of Applied Physics and Applied Mathematics Data Science Institute Columbia University NY10027 United States

A quantitative measure of symmetry breaking is introduced that allows the quantification of which symmetries are most strongly broken due to the introduction of some kind of defect in a perfect structure. The method uses a statistical approach based on the Jensen-Shannon divergence. The measure is calculated by comparing the transformed atomic density function with its original. Software code is presented that carries the calculations out numerically using Monte Carlo methods. The behavior of this symmetry breaking measure is tested for various cases including finite size crystallites (where the surfaces break the crystallographic symmetry), atomic displacements from high symmetry positions, and collective motions of atoms due to rotations of rigid octahedra. The approach provides a powerful tool for assessing local symmetry breaking and offers new insights that can help researchers understand how different structural distortions affect different symmetry operations. © 2024, CC BY.

关键词： Atoms

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