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Constructive coupling effect of topological states and topological phase transitions in plumbene

Physical Review B 2019年第19期99卷 195402-195402页

作者： Yue Li Jiayong Zhang Bao Zhao Yang Xue Zhongqin Yang State Key Laboratory of Surface Physics and Key Laboratory for Computational Physical Sciences (MOE) and Department of Physics Fudan University Shanghai 200433 China Ψusts Institute Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application and School of Mathematics and Physics Suzhou University of Science and Technology Suzhou Jiangsu 215009 China School of Physics Science and Information Technology Shandong Key Laboratory of Optical Communication Science and Technology Liaocheng University Liaocheng 252059 China Collaborative Innovation Center of Advanced Microstructures Fudan University Shanghai 200433 China

Combining tight-binding (TB) models with first-principles calculations, we investigate electronic and topological properties of plumbene. ‘‘Constructive’’ coupling effects of topological states are found in the low-buckled plumbene, causing the system being a normal insulator, opposite to topologically nontrivial states formed in other two-dimensional (2D) group IVA monolayers (from graphene to stanene). Local topologic states are found being located not only at the Γ point in the Brillouin zone, but also at the K/K′ points, whose coupling determines the final topological behaviors of the whole system. Based on this mechanism, several schemes are raised to produce a globally topological state in the plumbene. When the plumbene is functionalized with ethynyl (PbC2H), a quantum spin Hall (QSH) state comes out. Very interestingly, when an exchange field is introduced to the pristine plumbene, the system exhibits a quantum anomalous Hall (QAH) effect despite the coupling effect of the topological states.

关键词： Electronic structure Topological phase transition Honeycomb lattice Topological insulators Density functional theory Tight-binding model Wannier function methods

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A formation generation algorithm of multiple agents in naval battlefield environments

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International Journal of Security and Networks 2019年第1期14卷 34-46页

作者： Cui, Yani Ren, Jia Fu, Delong Dong, Chao College of Information Science and Technology Hainan University Haikou570228 China Key Laboratory of Technology and Application for Safeguarding of Marine Rights and Interests Guangzhou510310 China College of Meterology and Oceanography National University of Defense Technology Changsha410073 China Key Laboratory of Technology and Application for Safeguarding of Marine Rights and Interests South China Sea Marine Survey and Technology Center Guangzhou510310 China

This study aims to present a model of the formation generation for multiple agents using a modified binary particle swarm optimisation (MBPSO). The major objective of this study is to maximise the formation combat capability and reduce the formation generation cost. We treat the ratio of the aforementioned two values as a measure of formation combat effectiveness. Additionally, chaos theory is adopted in the initialisation of MBPSO to acquire diversified particle population. Moreover, particle diversity is utilised to dynamically adjust the particle position updating process to guarantee the global convergence. A case study for multi-agent formation generation model in a naval battlefield is conducted. It is shown that the proposed algorithm can accomplish multi-agent formation generation under multiple constraints. Compared with the existing related algorithms, the proposed algorithm has improved search performance and better convergence characteristics. © 2019 Inderscience Enterprises Ltd.

关键词： Chaos theory

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Coupling effect of topological states and Chern insulators in two-dimensional triangular lattices

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Physical Review B 2018年第12期97卷 125430-125430页

作者： Jiayong Zhang Bao Zhao Yang Xue Tong Zhou Zhongqin Yang Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application Ψusts Institute and School of Mathematics and Physics Suzhou University of Science and Technology Suzhou Jiangsu 215009 China State Key Laboratory of Surface Physics and Key Laboratory for Computational Physical Sciences (MOE) and Department of Physics Fudan University Shanghai 200433 China School of Physics Science and Information Technology Shandong Key Laboratory of Optical Communication Science and Technology Liaocheng University Liaocheng 252059 China Collaborative Innovation Center of Advanced Microstructures Fudan University Shanghai 200433 China

We investigate topological states of two-dimensional (2D) triangular lattices with multiorbitals. Tight-binding model calculations of a 2D triangular lattice based on px and py orbitals exhibit very interesting doubly degenerate energy points at different positions (Γ and K/K′) in momentum space, with quadratic non-Dirac and linear Dirac band dispersions, respectively. Counterintuitively, the system shows a global topologically trivial rather than nontrivial state with consideration of spin-orbit coupling due to the “destructive interference effect” between the topological states at the Γ and K/K′ points. The topologically nontrivial state can emerge by introducing another set of triangular lattices to the system (bitriangular lattices) due to the breakdown of the interference effect. With first-principles calculations, we predict an intrinsic Chern insulating behavior (quantum anomalous Hall effect) in a family of the 2D triangular lattice metal-organic framework of Co(C21N3H15) (TPyB-Co) from this scheme. Our results provide a different path and theoretical guidance for the search for and design of new 2D topological quantum materials.

关键词： Electronic structure Topological insulators 2-dimensional systems Topological materials Density functional theory First-principles calculations Tight-binding model Wannier function methods

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Kinetic energy and speed powers vn of a heavy quark inside S wave and P wave heavy-light mesons

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Physical Review D 2024年第7期110卷 076002页

作者： Wei Li Tianhong Wang Tai-Fu Feng Guo-Li Wang Chao-Hsi Chang Department of Physics Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China College of Science School of Physics CAS Key Laboratory of Theoretical Physics School of Physical Sciences

The average values of the powers of |q→|n¯≡qn and |v→|n¯≡vn are commonly used physical quantities, where q→ and v→ are the three-dimensional momentum and velocity of a quark inside a meson, respectively. For example, the average kinetic energy μπ2=q2 is an important quantity in the heavy quark effective theory, and the expansion of vn is commonly used in the nonrelativistic quantum chromodynamics. In this paper, based on the instantaneous Bethe-Salpeter equation method, we calculate the average values qn and vn (n=1, 2, 3, 4) of a heavy quark inside S wave and P wave heavy-light mesons. We obtain the kinetic energy μπ2=0.455 GeV2 for the B meson, which is consistent with the experimental result 0.464±0.076 GeV2. For the Bs, D, and Ds mesons, the μπ2 are 0.530, 0.317, and 0.369 GeV2, respectively, and v2=0.0185, 0.0215, 0.121, and 0.140 for B, Bs, D, and Ds, respectively. We obtain some relationships, for example, q0−n(mS)≈q1−n(mS), q0+n(mP)≈q1+′n(mP′)>q1+n(mP)≈q2+n(mP), and qn(mS)

关键词： Bethe-Salpeter equation Bound states Heavy quark effective theory Quark model

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Topologically trivial states induced by strong spin-orbit coupling and Chern insulators in doped X(C21N3H15) (X=Ta, Hf) metal-organic frameworks

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Physical Review B 2019年第3期99卷 035409-035409页

作者： Jiayong Zhang Bao Zhao Tong Zhou Yang Xue Yu Fang Chunlan Ma Zhongqin Yang Ψusts Institute Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Mathematics and Physics Suzhou University of Science and Technology Suzhou Jiangsu 215009 China State Key Laboratory of Surface Physics Key Laboratory for Computational Physical Sciences (MOE) Department of Physics Fudan University Shanghai 200433 China School of Physics Science and Information Technology Shandong Key Laboratory of Optical Communication Science and Technology Liaocheng University Liaocheng 252059 China Collaborative Innovation Center of Advanced Microstructures Fudan University Shanghai 200433 China

We study topological properties of two-dimensional (2D) bi-triangular lattices with multiple p and d orbitals. Tight-binding (TB) model calculations show that the multiple p (px/py) and d (dxy/dx2−y2 or dxz/dyz) bands in the 2D bi-triangular lattices, with C3 symmetry, are all degenerate at the Γ point with quadratic non-Dirac band dispersions and gapped at the K/K′ points. Spin-orbit coupling (SOC) is found not only resulting in the topologically nontrivial states, but also the topologically trivial states. In the 2D bi-triangular lattices, a topological phase transition from a topologically nontrivial state to a trivial state can be triggered by increasing the atomic SOC strength. Our first-principles calculations predict a large band-gap quantum anomalous Hall state (about 30 meV) and topological phase transitions in a 2D metal-organic frameworks X(C21N3H15) (X=Ta, Hf), rationalized well by the TB model built above. Our results are helpful to deeply understand the topological states and provide theoretical guidance for the search of 2D topological materials based on the multiple p and d orbitals.

关键词： Electronic structure Topological materials Topological phase transition 2-dimensional systems Topological insulators First-principles calculations Tight-binding model Wannier function methods

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Monitoring vegetation water content using microwave vegetation indices

Monitoring vegetation water content using microwave vegetati...

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2008 IEEE International Geoscience and Remote Sensing Symposium - Proceedings

作者： Tao, Jing Shi, Jiancheng Jackson, Tom Du, Jinyang Bindlish, Rajat Zhang, Lixin School of Geography and Remote Sensing Science Beijing Normal University Beijing China State Key Laboratory of Remote Sensing Science Beijing Normal University and the Institute of Remote Sensing Applications CAS Beijing China USDA ARS Hydrology and Remote Sensing Lab MD United States Institute for Computational Earth System Science University of California Santa Barbara CA United States Institute of Remote Sensing Application Chinese Academy of Sciences Beijing China

ISBN: (纸本)9781424428083

Effectively monitoring vegetation water is essential to improve our understanding of agriculture and hydrology. Vegetation water content is often estimated using vegetation indices derived from optical satellite sensors. In this study, we introduced the new microwave vegetation indices (MVIs) and derived the new MVIs using observation from the Advanced Microwave Scanning Radiometer (AMSR-E). To demonstrate the potential of the proposed MVIs, we compared them with vegetation water content which were obtained using ground based observations of vegetation water content and reflectance from a MultiSpectral Radiometer (MSR) during the National Airborne Field Experiment 2006 (NAFE'06), as well as the coincident Landsat 5 TM data. The estimated vegetation water content were averaged and compared with daily MVIs derived from AMSR-E on EASE-GRID pixels. The results of comparison between the MVIs and crop water content on EASE-GRID pixels demonstrated that the MVIs could be used to monitor the vegetation water content, which suggests additional all weather information and a potential linkage of the two data sources. In combination with vegetation indices derived from conventional optical sensor, MVIs provide a possible complementary dataset for monitoring global vegetation from space. © 2008 IEEE.

关键词： Vegetation

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Multi-dimensional Graph Linear Canonical Transform

arXiv

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arXiv 2024年

作者： Li, Na Zhang, Zhichao Han, Jie Chen, Yunjie Cao, Chunzheng School of Mathematics and Statistics Center for Applied Mathematics of Jiangsu Province Jiangsu International Joint Laboratory on System Modeling and Data Analysis Nanjing University of Information Science and Technology Nanjing210044 China Key Laboratory of System Control and Information Processing Ministry of Education Shanghai200240 China Key Laboratory of Computational Science and Application of Hainan Province Haikou571158 China School of Remote Sensing and Geomatics Engineering Nanjing University of Information Science and Technology Nanjing210044 China

Many multi-dimensional (M-D) graph signals appear in the real world, such as digital images, sensor network measurements and temperature records from weather observation stations. It is a key challenge to design a transform method for processing these graph M-D signals in the linear canonical transform domain. This paper proposes the two-dimensional graph linear canonical transform based on the central discrete dilated Hermite function (2-D CDDHFs-GLCT) and the two-dimensional graph linear canonical transform based on chirp multiplication-chirp convolution-chirp multiplication decomposition (2-D CM-CC-CM-GLCT). Then, extending 2-D CDDHFs-GLCT and 2-D CM-CC-CM-GLCT to M-D CDDHFs-GLCT and M-D CM-CC-CM-GLCT. In terms of the computational complexity, additivity and reversibility, M-D CDDHFs-GLCT and M-D CM-CC-CM-GLCT are compared. Theoretical analysis shows that the computational complexity of M-D CM-CC-CM-GLCT algorithm is obviously reduced. Simulation results indicate that M-D CM-CC-CM-GLCT achieves comparable additivity to M-D CDDHFs-GLCT, while M-D CM-CC-CM-GLCT exhibits better reversibility. Finally, M-D GLCT is applied to data compression to show its application advantages. The experimental results reflect the superiority of M-D GLCT in the algorithm design and implementation of data compression. Copyright © 2024, The Authors. All rights reserved.

关键词： Chirp modulation

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Biogeography-based optimization for motif discovery problem

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Journal of computational Information Systems 2013年第17期9卷 6999-7010页

作者： Feng, Siling Zhu, Qingxin Gong, Xiujun Zhong, Sheng School of Computer Science and Engineering University of Electronic Science and Technology of China Chengdu 610054 China College of Information Science and Technology Hainan University Haikou 570228 China School of Computer Science and Technology Tianjin University Tianjin 30072 China Tianjin Key Laboratory of Cognitive Computing and Application Tianjin 30072 China

The computational discovery of DNA motifs for previously uncharacterized transcription factors in groups of co-regulated genes is a well-studied problem with a great deal of practical relevance to the biologist. As a NP-hard Problem, evolutionary computation approaches are gaining more attractions from articial intelligence communities in recent years. In this paper, we applied a Biogeography-Based Optimization (BBO) approach, a relatively new evolutionary global optimization technique based on the science of biogeography, to predict motifs from DNA sequences. The migration and mutation operators of BBO were modied to meet motif discovery requirements. Furthermore, an integrated mechanism for the generation of initial populations was designed. The proposed algorithm can gain meaningful motifs with a fast convergence rate. The experimental results on two commonly used datasets demonstrated the validity and effectiveness for motif discovery problems. © 2013 Binary Information Press.

关键词： DNA sequences

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Integrability of Kerr-Newman spacetime with cloud strings, quintessence and electromagnetic field

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Physical Review D 2022年第12期105卷 124039-124039页

作者： Wenfu Cao Wenfang Liu Xin Wu School of Mathematics Physics and Statistics Shanghai University of Engineering Science Shanghai 201620 China Center of Application and Research of Computational Physics Shanghai University of Engineering Science Shanghai 201620 China Guangxi Key Laboratory for Relativistic Astrophysics Guangxi University Nanning 530004 China

The dynamics of charged particles moving around a Kerr-Newman black hole surrounded by cloud strings, quintessence and electromagnetic field is integrable due to the presence of a fourth constant of motion like the Carter constant. The fourth motion constant and the axial symmetry of the spacetime give a chance to the existence of radial effective potentials with stable circular orbits in two-dimensional planes, such as the equatorial plane and other nonequatorial planes. They also give a possibility of the presence of radial effective potentials with stable spherical orbits in the three-dimensional space. The dynamical parameters play important roles in changing the graphs of the effective potentials. In addition, variations of these parameters affect the presence or absence of stable circular orbits, innermost stable circular orbits, stable spherical orbits, and marginally stable spherical orbits. They also affect the radii of the stable circular or spherical orbits. It is numerically shown that the stable circular orbits and innermost stable circular orbits can exist not only in the equatorial plane but also in the nonequatorial planes. Several stable spherical orbits and marginally stable spherical orbits are numerically confirmed too. In particular, there are some stable spherical orbits and marginally stable spherical orbits with vanishing angular momenta which cover the whole range of latitudinal coordinates.

关键词： Classical black holes

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Elemental noncentrosymmetric superconductors

arXiv

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arXiv 2024年

作者： Zhang, Hu Research Center for Computational Physics of Hebei Province Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory College of Physics Science and Technology Hebei University Baoding071002 China

Superconductivity has been discovered in many materials including elements, cuprates and nickelates. Noncentrosymmetric superconductors get attention due to their physical properties results from spatial inversion symmetry breaking. Here we propose the existence of elemental noncentrosymmetric superconductors which needs to break spatial inversion symmetry in single element phases realized by occupations of more than one Wyckoff positions. Elemental noncentrosymmetric superconductors allow us to study the admixture of spin-singlet and spin-triplet pairing states in elements with simple crystal structures and chemical conditions. We find that four-layer La thin films coming from bulk α-La with a double hexagonal close-packed structure are elemental noncentrosymmetric superconductors since the dimension reduction breaks the spatial inversion symmetry. In the normal state, four-layer La is a polar rare-earth metal with a spontaneous polarization having a polar layer group like ferroelectrics. Hence, to be more precise, four-layer La can also be called the elemental polar superconductor in the superconductivity state. Based on this method of breaking inversion symmetry, we discovery polar rare-earth metals, polar transition metals, polar alkali metals and polar alkali earth metals. Other candidate materials are bulk polar materials formed with group 15 elements, Bi thin films with polar stacking, polar double layer plumbene and Al thin films. The question of building the periodic table of elemental noncentrosymmetric superconductors is raised. © 2024, CC BY.

关键词： Rare earths

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