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Dynamical quantum phase transition in XY chains with the Dzyaloshinskii-Moriya and XZY-YZX three-site interactions

Chinese Physics B 2022年第6期31卷 260-266页

作者： Kaiyuan Cao Ming Zhong Peiqing Tong Department of Physics and Institute of Theoretical Physics Nanjing Normal UniversityNanjing 210023China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal UniversityNanjing 210023China

We study the dynamical quantum phase transitions(DQPTs)in the XY chains with the Dzyaloshinskii-Moriya interaction and the XZY-YZX type of three-site interaction after a sudden *** the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form■where the quasiparticle excitation spectraεkmay be smaller than 0 for some k and are asymmetrical■It is found that the factors of Loschmidt echo equal 1 for some k corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfyingε_(k)·ε_(-k)<0,when the quench is from the gapless *** considering the quench from different ground states,we obtain the conditions for the occurrence of DQPTs for the general XY chains with gapless phase,and find 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 *** is different from the DQPTs in the case of quench from the gapped phase to gapped phase,in which the DQPTs will always ***,we analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped *** conclusion can also be extended to the general quantum spin chains.

关键词： dynamical quantum phase transition gapless phase asymmetry excitation spectra

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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

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Impacts of meteorology and emission variations on the heavy air pollution episode in North China around the 2020 Spring Festival

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Science China Earth Sciences 2021年第2期64卷 329-339页

作者： Wenbo XUE Xurong SHI Gang YAN Jinnan WANG Yanling XU Qian TANG Yanli WANG Yixuan ZHENG Yu LEI Center of Air Modeling and Systems Analysis Chinese Academy for Environmental PlanningBeijing 100012China State Environmental Protection Key Laboratory of Environmental Planning and Policy Simulation Chinese Academy for Environmental PlanningBeijing 100012China

Based on the Weather Research and Forecasting model and the Models-3 community multi-scale air quality model(WRF-CMAQ),this study analyzes the impacts of meteorological conditions and changes in air pollutant emissions on the heavy air pollution episode occurred over North China around the 2020 Spring Festival(January to Februray 2020).Regional reductions in air pollutant emissions required to eliminate the PM2.5 heavy pollution episode are also *** results found that meteorological conditions for the Beijing-Tianjin-Hebei and surrounding"2+26"cities are the worst during the heavy pollution episode around the 2020 Spring Festival as compared with two other typical heavy pollution episodes that occurred after ***,because of the substantial reductions in air pollutant emissions in the"2+26"cities in recent years,and the32%extra reduction in emissions during January to February 2020 compared with the baseline emission levels of the autumn and winter of 2019 to 2020,the maximum PM2.5 level during this heavy pollution episode around the 2020 Spring Festival was much lower than that in the other two typical ***,these emission reductions are still not enough to eliminate regional heavy pollution *** with the actual emission levels during January to February 2020,a 20%extra reduction in air pollutant emissions in the"2+26"cities(or a 45%extra reduction compared with baseline emission levels of the autumn and winter of 2019 to 2020)could help to generally eliminate regionwide severe pollution episodes,and avoid heavy pollution episodes that last three or more consecutive days in Beijing;a 40%extra reduction in emissions(or a 60%extra reduction compared with baseline emission levels of the autumn and winter of 2019 to 2020)could help to generally eliminate regionwide and continuous heavy pollution *** analysis finds that during the clean period after the heavy pollution episode around the 2020 Spring Festival,the regionwide

关键词： "2+26"cities 2020 Spring Festival Heavy air pollution episode WRF-CMAQ model

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Hierarchical convolutional features for end-to-end representation-based visual tracking

Hierarchical convolutional features for end-to-end represent...

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作者： Zhu, Suguo Fang, Zhenying Gao, Fei Key Laboratory of Complex Systems Modeling and Simulation School of Computer Science and Technology Hangzhou Dianzi University Hangzhou310018 China State Key Laboratory of Integrated Services Networks Xidian University Xian710071 China

Recently, deep learning is widely developed in computer vision applications. In this paper, a novel simple tracker with deep learning is proposed to complete the tracking task. A simple fully convolutional Siamese network is applied to capture the similarity between different frames. Nevertheless, the detailed information from lower layers, which is also important for locating the target object, is not considered into the tracking task. In this paper, the detailed information from two lower layers is considered into the response map to improve the performance and not to increase much time spent. This leads more significant improvement for feature representation and localization of the target object. The experimental results demonstrate that the proposed algorithm is efficient and robust compared with the baseline and the state-of-the-art trackers. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

关键词： Deep neural networks

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A Model for the Visual Effect Evaluation of a Urban Road Indicating Device 29

A Model for the Visual Effect Evaluation of a Urban Road Ind...

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第29届中国控制与决策会议

作者： Guang-yu Zhu Xin-ming Yu Lei Zhao Li Wang Peng Zhang MOE Key Laboratory for Transportation Complex Systems Theory and Technology Beijing Jiaotong University Beijing Municipality Key Laboratory of Urban Traffic Operation Simulation and Decision Support

ISBN: (纸本)9781509046584

For an urban road indicating device,Variable Message Signs(VMS) screen system is used to publish and display all kinds of traffic information,including the condition of current and nearby roads and the useful travel advice,which leads to the topic that the VMS screen visual effect is a crucial ***,a model for the visual effect evaluation of VMS screen with the simulation method is studied in this ***,establish a reasonable evaluation index system;secondly,build a VMS screen dynamic evaluation model based on Analytic Hierarchy Process(AHP) method and two-level fuzzy comprehensive evaluation method;in addition,select one VMS screen in Beijing as an example,then evaluate the visual effect comprehensively by ***,optimize simulation parameters by field driving,which makes the model more effective and more *** provides an innovative way to improve VMS design standards.

关键词： Variable Message Sign Visual Effect Fuzzy Comprehensive Evaluation simulation

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Discovering API Directives from API Specifications with Text Classification

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Journal of Computer Science & Technology 2021年第4期36卷 922-943页

作者： Jing-Xuan Zhang Chuan-Qi Tao Zhi-Qiu Huang Xin Chen College of Compute Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Safety-Critical Software(Nanjing University of Aeronautics and Astronautics) Ministry of Industry and Information TechnologyNanjing 210016China Key Laboratory of Complex Systems Modeling and Simulation(Hangzhou Dianzi University) Ministry of Education Hangzhou 310018China School of Computer Science and Technology Hangzhou Dianzi UniversityHangzhou 310018China

Application programming interface(API)libraries are extensively used by *** correctly program with APIs and avoid bugs,developers shall pay attention to API directives,which illustrate the constraints of ***,API directives usually have diverse morphologies,making it time-consuming and error-prone for developers to discover all the relevant API *** this paper,we propose an approach leveraging text classification to discover API directives from API ***,given a set of training sentences in API specifications,our approach first characterizes each sentence by three groups of ***,to deal with the unequal distribution between API directives and non-directives,our approach employs an under-sampling strategy to split the imbalanced training set into several subsets and trains several *** a new sentence in an API specification,our approach synthesizes the trained classifiers to predict whether it is an API *** have evaluated our approach over a publicly available annotated API directive *** experimental results reveal that our approach achieves an F-measure value of up to 82.08%.In addition,our approach statistically outperforms the state-of-the-art approach by up to 29.67%in terms of F-measure.

关键词： Application programming interface(API)directive API specification imbalanced learning text classification

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Machine Learning Security Analysis Framework Based on Threat Matrix 8

Machine Learning Security Analysis Framework Based on Threat...

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8th International Conference on Data Science in Cyberspace, DSC 2023

作者： Li, Hu Ma, Qiongmin Zhang, Ming Kuang, Xiaohui National Key Laboratory of Science and Technology on Information System Security Beijing China National Key Laboratory for Complex Systems Simulation Beijing China

ISBN: (纸本)9798350331035

Machine Learning and Artificial Intelligence technology accelerates technological progress and promotes social development, but also brings many security problems. Machine learning models may be affected, deceived, controlled or destroyed at different stages, e.g. training and inference, which may lead to serious consequences. In view of the main stages of the life cycle of machine learning, we summarizes the related attack and defense technologies based on threat matrix, makes a comprehensive and systematic analysis on the security issues of machine learning, and puts forward several security protection suggestions for intelligent information systems. © 2023 IEEE.

关键词： Artificial Intelligence Machine Learning Security Analysis Threat Matrix

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Energy efficiency analysis of heterogeneous platforms: Early experiences 7

Energy efficiency analysis of heterogeneous platforms: Early...

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7th International Green and Sustainable Computing Conference, IGSC 2016

作者： Li, Youhuizi Shi, Weisong Jiang, Congfeng Zhang, Jilin Wan, Jian Key Laboratory of Complex Systems Modeling and Simulation Hangzhou Dianzi University China Mobile and Internet Systems Laboratory Wayne State University United States School of Information and Electronic Engineering Zhejiang University of Science and Technology China

ISBN: (纸本)9781509051175

Heterogeneous multi-core platforms, e.g., ARM's ***, are a promising trend to improve the performance and energy efficiency of future mobile systems. However, the immediate benefits and the challenges to take advantage of the heterogeneity are still not clear. In this paper, we present our early experiences about the energy efficiency of the two *** heterogeneous platforms: ODROID XU+E and ODROID XU3. We quantified compared them with homogeneous platforms through multiple benchmarks which include popular mobile applications and high-performance parallel benchmarks. Besides, we analyzed the scheduling impact on the energy consumption of the heterogeneous platforms and the migration cost is also discussed. Based on the results, several insights, such as fine-granularity power control and thread level parallelism, related to hardware, application and system design are derived. © 2016 IEEE.

关键词： Energy utilization

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Research on information capability based high-performance information sharing in the simulation grid

Research on information capability based high-performance in...

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2010 International Conference on Computer modeling and simulation, ICCMS 2010

作者： Zhang, Ying-Chao Zhang, Jing Chen, Xin Yu, Qin-Zhang Zhang, Hao Beijing Institute of System Engineering National Key Laboratory of Science and Technology on Complex Systems Simulation Beijing China

ISBN: (纸本)9780769539416

For the purpose of achieving high-performance information sharing in the simulation grid, an information capability-based Three Phase High-performance Information Sharing Approach (TPHPISA for short) is advanced. The main idea of TPHPISA is selecting those information sources with highest information capability and executing the best query plan. To illustrate how TPHPISA works, an application example of implementing high-performance information sharing in the stock market simulation grid is thoroughly analyzed. At last, the searching efficiency and accuracy of TPHPISA are demonstrated through comparing with other similar method. © 2010 IEEE.

关键词： Information analysis

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modeling and simulation of international politics evolution in crisis

Modeling and simulation of international politics evolution ...

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2010 International Conference on Computer modeling and simulation, ICCMS 2010

作者： Yu, Qin-Zhang Zhang, Jing Zhang, Ying-Chao Beijing Institute of System Engineering National Key Laboratory of Science and Technology on Complex Systems Simulation Beijing China

ISBN: (纸本)9780769539416

Under the guidance of the theories of complex Adaptive System and Artificial Societies, modeling and simulation of international politics evolution in crisis was studied. The Model of International Politics Evolution (IPEM) in crisis based on Agent was built. The function and architecture of IPEM were introduced. Individual Agent , including Nation Agent, International Organization Agent and Environment Agent, was described in detail. A simulation experiment was executed to prove the effectiveness of the method proposed in the paper. © 2010 IEEE.

关键词： Adaptive systems

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