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A grain level model for deformation and failure of ultrafine-grained tungsten

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Science China(Technological Sciences) 2019年第5期62卷 755-761页

作者： REN Ke CHEN LiRong CHENG YangYang WANG JianXiang DUAN HuiLing State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science College of EngineeringPeking University Key Laboratory of High Energy Density Physics Simulation Center of Applied Physics and Technology BIC-ESAT and IFSA Collaborative Innovation Center of MoE Peking University

Ultrafine-grained tungsten(UFG W) produced by severe plastic deformation technology has many potential applications due to its high strength and ductility. To reveal the mechanism for the high ductility of UFG W, the deformation and failure behaviors of coarse-grained tungsten(CG W) and UFG W have been compared based on a three-dimensional crystal plastic finite element method(CPFEM) simulation. Cohesive element method has been utilized to model the behavior of grain boundaries(GBs). Both plastic deformation in grain interiors and grain boundary opening have been observed in different periods of deformation in UFG W. It is concluded that the high GB density and elongated microstructure in the UFG W suppress crack propagation, decrease the stress concentration and impurity concentration on GBs, therefore enhance the ductility of the material.

关键词： ultrafine grain(UFG) tungsten crystal plasticity interface failure

Bottomoniumlike tetraquarks in a chiral quark model

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Physical Review D 2022年第1期106卷 014021-014021页

作者： Gang Yang Jialun Ping Jorge Segovia Department of Physics Zhejiang Normal University Jinhua 321004 China Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People’s Republic of China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide E-41013 Sevilla Spain

The low-lying bottomoniumlike tetraquarks bb¯qq¯ (q=u, d, s) with spin-parity JP=0+, 1+, and 2+, and isospin I=0, 1, or 12, are systematically investigated within the theoretical framework of real- and complex-scaling range of a chiral quark model, which has already been successfully applied in analysis of several multiquark systems. A complete four-body S-wave function, which includes meson-meson, diquark-antidiquark and K-type arrangements of quarks, along with all possible color configurations are considered. In the bb¯qq¯ (q=u, d) tetraquark system, we found resonance states of B(*)B¯(*), ϒω, ϒρ, and ηbρ nature with all possible I(JP) quantum numbers. Their masses are generally located in the energy range 11.0–11.3 GeV and their widths are less than 10 MeV. In addition, extremely narrow resonances, with two-meson strong decay widths less than 1.5 MeV, are obtained in both bb¯us¯ and bb¯ss¯ tetraquark systems. Particularly, four radial excitations of ϒK* and ηbK* are found at ∼11.1 GeV in JP=0+, 1+, and 2+ channels of bb¯us¯ system. One ϒ(1S)ϕ(2S) resonance state is obtained at 11.28 GeV in the JP=1+ sector.

关键词： Quantum chromodynamics Quark model Strong interaction

A Fast Algorithm for Solving a Class of the Linear Complementarity Problem in a Finite Number of Steps

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Abstract and Applied Analysis

Abstract and Applied Analysis 2020年第none期2020卷 1-8页

作者： Achik, Yamna Idmbarek, Asmaa Nafia, Hajar Agmour, Imane El Foutayeni, Youssef Analysis Modeling and Simulation Laboratory Hassan II University Morocco Unit for Mathematical and Computer Modeling of Complex Systems IRD France

The linear complementarity problem is receiving a lot of attention and has been studied extensively. Recently, El foutayeni et al. have contributed many works that aim to solve this mysterious problem. However, many results exist and give good approximations of the linear complementarity problem solutions. The major drawback of many existing methods resides in the fact that, for large systems, they require a large number of operations during each iteration;also, they consume large amounts of memory and computation time. This is the reason which drives us to create an algorithm with a finite number of steps to solve this kind of problem with a reduced number of iterations compared to existing methods. In addition, we consider a new class of matrices called the E-matrix. © 2020 Yamna Achik et al.

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Dynamical quantum phase transition in quantum spin chains with gapless phases

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arXiv 2021年

作者： Cao, Kaiyuan Ming, Zhong Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

The dynamical quantum phase transitions (DQPTs) in quantum spin chains with gapless phases after a sudden quench are studied. We mainly consider the general systems with asymmetrical quasiparticle excitation spectra and obtain the general expression of the Loschmidt echo as well as the general conditions for the occurrence of DQPTs. As two examples, we study the DQPTs in the XY chains with Dzyaloshinskii-Moriya interaction and XZY-YZX type of three-site interaction. It's found that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Besides, we also analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. © 2021, CC BY.

关键词： Phase transitions

SOME REMARKS ON LIOUVILLE TYPE THEOREMS FOR THE 3D STEADY TROPICAL CLIMATE MODEL

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arXiv 2025年

作者： Dong, Yanyan Zhang, Zhibing School of Mathematics and Physics Anqing Normal University Anqing246133 China School of Mathematics and Physics Key Laboratory of Modeling Simulation and Control of Complex Ecosystem in Dabie Mountains Anhui Higher Education Institutes Anqing Normal University Anqing246133 China

Observing the special structure of the system and using the Poincaré-Sobolev inequality, we establish Liouville type theorems for the 3D steady tropical climate model under certain conditions on u, v, ∇θ. Our results extend and improve a Liouville type result of Cho-In-Yang (arXiv:2312.17441).MSC Codes 35B53, 35Q35, 35A02 © 2025, CC BY.

关键词： Climate models

Relaxation dynamics in the alternating XY chain following a quantum quench

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arXiv 2023年

作者： Cao, Kaiyuan Hu, Yayun Tong, Peiqing Yang, Guangwen Liu, Peng Zhejiang Lab Hangzhou311100 China Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Department of Computer Science and Technology Tsinghua University Haidian District Beijing100084 China College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China

We investigate the relaxation dynamics of the fermion two-point correlation function Cmn(t) = 〈ψ(t)|c†mcn|ψ(t)〉 in the XY chain with alternating nearest-neighbor hopping interaction after a quench. We find that the deviation δCmn(t) = Cmn(t) − Cmn(∞) decays with time following the power law behavior t−µ, where the exponent µ depends on whether the quench is to the commensurate phase (µ = 1) or incommensurate phase (µ = 1/2). This decay of δCmn(t) arises from the transient behavior of the double-excited quasiparticle occupations and the transitions between different excitation spectra. Furthermore, we find that the steady value Cmn(∞) only involves the average fermion occupation numbers (i.e. the average excited single particle) over the time-evolved state, which are different from the ground state expectation values. We also observe nonanalytic singularities in the steady value Cmn(∞) for the quench to the critical points of the quantum phase transitions (QPTs), suggesting its potential use as a signature of QPTs. Copyright © 2023, The Authors. All rights reserved.

关键词： Ground state

A Comprehensive Evaluation Framework for Deep Model Robustness

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arXiv 2021年

作者： Guo, Jun Bao, Wei Wang, Jiakai Ma, Yuqing Gao, Xinghai Xiao, Gang Liu, Aishan Dong, Jian Liu, Xianglong Wu, Wenjun State Key Lab of Software Development Environment Beihang University Beijing China China Electronics Standardization Institute Beijing China Zhongguancun Laboratory Beijing China Institute of Unmanned System Beihang University Beijing China National Key Laboratory for Complex Systems Simulation Beijing China

Deep neural networks (DNNs) have achieved remarkable performance across a wide range of applications, while they are vulnerable to adversarial examples, which motivates the evaluation and benchmark of model robustness. However, current evaluations usually use simple metrics to study the performance of defenses, which are far from understanding the limitation and weaknesses of these defense methods. Thus, most proposed defenses are quickly shown to be attacked successfully, which results in the "arm race" phenomenon between attack and defense. To mitigate this problem, we establish a model robustness evaluation framework containing 23 comprehensive and rigorous metrics, which consider two key perspectives of adversarial learning (i.e., data and model). Through neuron coverage and data imperceptibility, we use data-oriented metrics to measure the integrity of test examples;by delving into model structure and behavior, we exploit model-oriented metrics to further evaluate robustness in the adversarial setting. To fully demonstrate the effectiveness of our framework, we conduct large-scale experiments on multiple datasets including CIFAR-10, SVHN, and Im-ageNet using different models and defenses with our open-source platform. Overall, our paper provides a comprehensive evaluation framework, where re-searchers could conduct comprehensive and fast evaluations using the open-source toolkit, and the analytical results could inspire deeper understanding and further improvement to the model robustness. Copyright © 2021, The Authors. All rights reserved.

关键词： Deep neural networks

Multi-task Paired Masking with Alignment modeling for Medical Vision-Language Pre-training

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arXiv 2023年

作者： Zhang, Ke Yang, Yan Yu, Jun Jiang, Hanliang Fan, Jianping Huang, Qingming Han, Weidong The Key Laboratory of Complex Systems Modeling and Simulation School of Computer Science and Technology Hangzhou Dianzi University Hangzhou310018 China Regional Medical Center for National Institute of Respiratory Diseases Sir Run Run Shaw Hospital College of Medicine Zhejiang University Hangzhou310016 China AI Lab at Lenovo Research 100094 China The School of Computer Science and Technology University of Chinese Academy of Sciences Beijing101408 China The Department of Medical Oncology at Sir Run Run Shaw Hospital College of Medicine Zhejiang University Hangzhou China The College of Mathematical Medicine Zhejiang Normal University Jinhua China

In recent years, the growing demand for medical imaging diagnosis has placed a significant burden on radiologists. As a solution, Medical Vision-Language Pre-training (Med-VLP) methods have been proposed to learn universal representations from medical images and reports, benefiting downstream tasks without requiring fine-grained annotations. However, existing methods have overlooked the importance of cross-modal alignment in joint image-text reconstruction, resulting in insufficient cross-modal interaction. To address this limitation, we propose a unified Med-VLP framework based on Multi-task Paired Masking with Alignment (MPMA) to integrate the cross-modal alignment task into the joint image-text reconstruction framework to achieve more comprehensive cross-modal interaction, while a Global and Local Alignment (GLA) module is designed to assist self-supervised paradigm in obtaining semantic representations with rich domain knowledge. Furthermore, we introduce a Memory-Augmented Cross-Modal Fusion (MA-CMF) module to fully integrate visual information to assist report reconstruction and fuse the multi-modal representations adequately. Experimental results demonstrate that the proposed unified approach outperforms previous methods in all downstream tasks, including uni-modal, cross-modal, and multimodal tasks. Copyright © 2023, The Authors. All rights reserved.

关键词： Alignment

Bottomonium-like tetraquarks in a chiral quark model

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arXiv 2022年

作者： Yang, Gang Ping, Jialun Segovia, Jorge Department of Physics Zhejiang Normal University Jinhua321004 China Department of Physics Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide SevillaE-41013 Spain

The low-lying bottomonium-like tetraquarks b(Equation presented)q(Equation presented) (q = u, d, s) with spin-parity JP = 0+, 1+ and 2+, and isospin I = 0, 1 or 1/2, are systematically investigated within the theoretical framework of real- and complex-scaling range of a chiral quark model, which has already been successfully applied in analysis of several multiquark systems. A complete four-body S-wave function, which includes meson-meson, diquark-antidiquark and K-type arrangements of quarks, along with all possible color configurations are considered. In the b(Equation presented)q(Equation presented) (q = u, d) tetraquark system, we found resonance states of B(*)(Equation presented)(*), Υω, Υρ and ηbρ nature with all possible I(JP) quantum numbers. Their masses are generally located in the energy range 11.0 − 11.3 GeV and their widths are less than 10 MeV. In addition, extremely narrow resonances, with two-meson strong decay widths less than 1.5 MeV, are obtained in both b(Equation presented)u(Equation presented) and b(Equation presented)s(Equation presented) tetraquark systems. Particularly, four radial excitations of ΥK∗ and ηbK∗ are found at ∼ 11.1 GeV in JP = 0+, 1+ and 2+ channels of b(Equation presented)u(Equation presented) system. One Υ(1S)φ(2S) resonance state is obtained at 11.28 GeV in the JP = 1+ sector. Copyright © 2022, The Authors. All rights reserved.

关键词： Hadrons