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Topological properties of Sb(111)surface:A first-principles study

Chinese physics B 2022年第4期31卷 603-607页

作者： Shuangxi Wang Ping Zhang Department of Materials Science and Engineering China University of PetroleumBeijing 102249China Institute of Applied Physics and Computational Mathematics Beijing 100088China Center for Applied Physics and Technology Peking UniversityBeijing 100871China

First-principles calculations based on the density functional theory were performed to systematically study the electronic properties of the thin film of antimony in(111)*** considering the spin-orbit interaction,for stoichiometric surface,the topological states keep robust for six-bilayer case,and can be recovered in the three-bilayer film,which are guaranteed by time-reversal symmetry and inverse *** reduced surface doped by non-magnetic Bi or magnetic Mn atom,localized three-fold symmetric features can be ***,band structures show that the non-trivial topological states stand for non-magnetic substitutional Bi atom,while can be eliminated by adsorbed or substitutional magnetic Mn atom.

关键词： first-principles study antimony topological states

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Predator Prey Scavenger Model using Holling’s Functional Response of Type III and physics-Informed Deep Neural Networks

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International Journal of applied and Computational mathematics 2025年第2期11卷 1-32页

作者： Panchal, Aneesh Beniwal, Kirti Kumar, Vivek Department of Computational and Data Sciences Indian Institute of Science Karnataka Bangalore 560012 India Department of Applied Mathematics Delhi Technological University Delhi New Delhi 110042 India

Nonlinear mathematical models introduce the relation between various physical and biological interactions present in nature. One of the most famous models is the Lotka–Volterra model which defined the interaction between predator and prey species present in nature. However, predators, scavengers, and prey populations coexist in a natural system where scavengers can additionally rely on the dead bodies of predators present in the system. Keeping this in mind, the formulation and simulation of the predator–prey scavenger model is introduced in this paper. For the predation response, respective prey species are assumed to have Holling’s functional response of type III. The proposed model is tested for various simulations and is found to be showing satisfactory results in different scenarios. After simulations, the American forest dataset is taken for parameter estimation which imitates the real-world case. For parameter estimation, a physics-informed deep neural network is used with the Adam backpropagation method which prevents the avalanche effect in trainable parameters updation. For neural networks, mean square error and physics-informed informed error are considered. After the neural network, the hence-found parameters are fine-tuned using the Broyden–Fletcher–Goldfarb–Shanno algorithm. Finally, the hence-found parameters using a natural dataset are tested for stability using Jacobian stability analysis. © The Author(s), under exclusive licence to Springer Nature India Private Limited 2025.

关键词： Broyden–Fletcher–Goldfarb–Shanno optimization physics-informed deep neural network Predator prey scavenger model Stability analysis

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Pretraining of attention-based deep learning potential model for molecular simulation

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npj Computational Materials 2024年第1期10卷 2297-2304页

作者： Duo Zhang Hangrui Bi Fu-Zhi Dai Wanrun Jiang Xinzijian Liu Linfeng Zhang Han Wang AI for Science Institute Beijing 100080China DP Technology Beijing 100080China Academy for Advanced Interdisciplinary Studies Peking UniversityBeijing 100871China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100094China HEDPS CAPTCollege of EngineeringPeking UniversityBeijing 100871China

Machine learning-assisted modeling of the inter-atomic potential energy surface(PES)is revolutionizing the field ofmolecular *** the accumulation of high-quality electronic structure data,a model that can be pretrained on all available data and finetuned on downstream tasks with a small additional effort would bring the field to a new *** we propose DPA-1,a Deep Potentialmodel with a gated attentionmechanism,which is highly effective for representing the conformation and chemical spaces of atomic systems and learning the *** tested DPA-1 on a number of systems and observed superior performance compared with existing *** pretrained on large-scale datasets containing 56 elements,DPA-1 can be successfully applied to various downstream tasks with a great improvement of sample ***,for different elements,the learned type embedding parameters form a spiral in the latent space and have a natural correspondence with their positions on the periodic table,showing interesting interpretability of the pretrained DPA-1 model.

关键词： potential representing positions

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Multi-armed bandits for resource efficient, online optimization of language model pre-training: the use case of dynamic masking 61

Multi-armed bandits for resource efficient, online optimizat...

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Findings of the Association for Computational Linguistics, ACL 2023

作者： Urteaga, Iñigo Lancewicki, Tomer Draïdia, Moulay-Zaïdane Khadivi, Shahram Applied Physics and Applied Mathematics Data Science Institute Columbia University New YorkNY United States Walmart Global Tech United States Data Science Institute Columbia University New YorkNY United States eBay Inc. Aachen Germany

ISBN: (纸本)9781959429623

We design and evaluate a Bayesian optimization framework for resource efficient pretraining of Transformer-based language models (TLMs). TLM pre-training requires high computational resources and introduces many unresolved design choices, such as selecting its pre-training hyperparameters. We propose a multi-armed bandit framework for the sequential selection of pre-training hyperparameters, aimed at optimizing language model performance, in a resource efficient manner. We design a Thompson sampling algorithm, with a surrogate Gaussian process reward model of the Masked Language Model (MLM) pretraining objective, for its sequential minimization. Instead of MLM pre-training with fixed masking probabilities, the proposed Gaussian process-based Thompson sampling (GP-TS) accelerates pre-training by sequentially selecting masking hyperparameters that improve performance. We empirically demonstrate how GP-TS pre-trains language models efficiently, i.e., it achieves lower MLM loss in fewer epochs, across a variety of settings. In addition, GP-TS pre-trained TLMs attain competitive downstream performance, while avoiding expensive hyperparameter grid search. GP-TS provides an interactive framework for efficient and optimized TLM pre-training that, by circumventing costly hyperparameter selection, enables substantial computational savings. © 2023 Association for Computational Linguistics.

关键词： Gaussian distribution

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A Nonlocal Stokes Systemwith Volume Constraints

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Numerical mathematics(Theory,Methods and Applications) 2022年第4期15卷 903-937页

作者： Qiang Du Zuoqiang Shi Department of Applied Physics and Applied Mathematics and Data Science InstituteColumbia UniversityNew YorkNY 10027USA Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China Yanqi Lake Beijing Institute of Mathematical Sciences and Applications Beijing 101408China

In this paper,we introduce a nonlocal model for linear steady Stokes system with physical no-slip boundary *** use the idea of volume constraint to enforce the no-slip boundary condition and prove that the nonlocal model is *** also show that and the solution of the nonlocal system converges to the solution of the original Stokes system as the nonlocality vanishes.

关键词： Nonlocal Stokes system nonlocal operators smoothed particle hydrodynamics incompressible flows well-posedness local limit

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Analysis of Network State by RIPE Atlas Distributed Measurement System 26

Analysis of Network State by RIPE Atlas Distributed Measurem...

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26th International Conference on Digital Signal Processing and its Applications, DSPA 2024

作者： Izyumov, Pavel S. Ivchenko, Alexander V. Moscow Institute of Physics and Technology Dolgoprudny Department of Multimedia Technologies and Telecommunications Russia Laboratory of Big Data and Information Systems Keldysh Institute of Applied Mathematics Moscow Russia

ISBN: (纸本)9798350361728

The paper describes the issues of setting up an experiment, limitations, and features of the platform, primarily focusing on the influence of hardware and software versions of probes, network types, and cross-traffic. The impact of new versions of software and hardware requires analysis and con-sideration in further data work. Additionally, the nature of the global network is evolving over time due to technological ad-vancements. The outcome of this work includes recommendations for calibrating measurements and reducing systematic sampling errors. © 2024 IEEE.

关键词： Systematic errors

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Newtonian limit of Einstein equation with a cosmological constant

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Chinese physics C 2024年第10期48卷 264-274页

作者： Li-Fang Li Zhoujian Cao Xiaokai He Institute of Mechanics Chinese Academy of SciencesBeijing 100190China Institute of Applied Mathematics Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China School of Mathematics and Statistics Hunan First Normal UniversityChangsha 410205China

Traditionally,the cosmological constant has been viewed as dark energy that mimics matter with negative *** that matter with negative energy provides a repulsive force,which fundamentally differs from typical gravitational forces,it has been believed that the cosmological constant effectively contributes a repulsive ***,it is important to note that the concept of gravitational force is valid only within the framework of Newtonian *** this study,we demonstrate that the traditional understanding of the gravitational force contributed by the cosmological constant is not entirely *** approach involves investigating the Newtonian limit of the Einstein equation with a cosmological *** subtleties involved in this analysis are discussed in ***,we find that the effect of the cosmological constant on Newtonian gravity is an attractive force rather than a repulsive one for ordinary *** expected,this corrective force is negligibly ***,our findings may offer a way to distinguish between dark energy and the cosmological constant,as one contributes a repulsive force while the other contributes an attractive force.

关键词： cosmological constant dark matter Einstein equation Newtonian limit dark energy

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Monolithic Convex Limiting for Legendre-Gauss-Lobatto Discontinuous Galerkin Spectral-Element Methods

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Communications on applied mathematics and Computation 2024年第3期6卷 1860-1898页

作者： Andrés M.Rueda-Ramírez Benjamin Bolm Dmitri Kuzmin Gregor J.Gassner Department of Mathematics and Computer Science University of CologneWeyertal 86-90Cologne 50931Germany Institute of Applied Mathematics(LS Ⅲ) TU Dortmund UniversityVogelpothsweg 87Dortmund 44227Germany Center for Data and Simulation Science University of CologneWeyertal 86-90Cologne 50931Germany

We extend the monolithic convex limiting(MCL)methodology to nodal discontinuous Galerkin spectral-element methods(DGSEMS).The use of Legendre-Gauss-Lobatto(LGL)quadrature endows collocated DGSEM space discretizations of nonlinear hyperbolic problems with properties that greatly simplify the design of invariant domain-preserving high-resolution *** to many other continuous and discontinuous Galerkin method variants,a particular advantage of the LGL spectral operator is the availability of a natural decomposition into a compatible subcellﬂux *** a highorder spatial semi-discretization in terms of intermediate states,we performﬂux limiting in a manner that keeps these states and the results of Runge-Kutta stages in convex invariant *** addition,local bounds may be imposed on scalar quantities of *** contrast to limiting approaches based on predictor-corrector algorithms,our MCL procedure for LGL-DGSEM yields nonlinearﬂux approximations that are independent of the time-step size and can be further modiﬁed to enforce entropy *** demonstrate the robustness of MCL/DGSEM schemes for the compressible Euler equations,we run simulations for challenging setups featuring strong shocks,steep density gradients,and vortex dominatedﬂows.

关键词： Structure-preserving schemes Subcellﬂux limiting Monolithic convex limiting(MCL) Discontinuous Galerkin spectral-element methods(DGSEMS) Legendre-Gauss-Lobatto(LGL)nodes

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CONVERGENCE ANALYSIS OF SOME FINITE ELEMENT PARALLEL ALGORITHMS FOR THE STATIONARY INCOMPRESSIBLE MHD EQUATIONS

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Journal of Computational mathematics 2024年第1期42卷 49-70页

作者： Xiaojing Dong Yinnian He Hunan Key Laboratory for Computation and Simulation in Science and Engineering Key Laboratory of Intelligent Computing&Information Processing of Ministry of EducationSchool of Mathematics and Computational ScienceXiangtan UniversityXiangtan 411105China Institute of Applied Physics and Computational Mathematics Beijing 100088China School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China

By combination of iteration methods with the partition of unity method(PUM),some finite element parallel algorithms for the stationary incompressible magnetohydrodynamics(MHD)with different physical parameters are presented and *** algorithms are highly *** first,a global solution is obtained on a coarse grid for all approaches by one of the iteration *** parallelized residual schemes,local corrected solutions are calculated on finer meshes with overlapping *** subdomains can be achieved flexibly by a class of *** proposed algorithm is proved to be uniformly stable and ***,one numerical example is presented to confirm the theoretical findings.

关键词： Partition of unity method Local and parallel algorithm Finite element method Iteration methods Magnetohydrodynamics

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Impacts of gravitational-wave background from supermassive black hole binaries on the detection of compact binaries by LISA

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Chinese physics C 2024年第6期48卷 198-203页

作者：黄帆毕研晨曹周键黄庆国 CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Institute of Applied Mathematics Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China

In the frequency band of the Laser Interferometer Space Antenna(LISA),extensive research has been conducted on the impact of foreground confusion noise generated by galactic binaries within the Milky Way ***,recent evidence of a stochastic signal,announced by the NANOGrav,EPTA,PPTA,CPTA,and InPTA,indicates that the stochastic gravitational-wave background(SGWB)generated by supermassive black hole binaries(SMBHBs)can contribute strong background noise within the LISA *** the presence of such strong noise,it is expected to have significant impacts on LISA's scientific *** this study,we investigate the impacts of the SGWB generated by SMBHBs on the detection of individual massive black hole binaries,verified galactic binaries,and extreme mass ratio inspirals in the context of *** find it essential to resolve and eliminate the excess noise from the SGWB to guarantee the success of LISA's missions.

关键词： gravitational-wave background supermassive black hole binaries LISA

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