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Phononic real Chern insulator with protected corner modes in graphynes

Physical Review B 2022年第8期105卷 085123-085123页

作者： Jiaojiao Zhu Weikang Wu Jianzhou Zhao Cong Chen Qianqian Wang Xian-Lei Sheng Lifa Zhang Y. X. Zhao Shengyuan A. Yang Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore 487372 Singapore Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Co-Innovation Center for New Energetic Materials Southwest University of Science and Technology Mianyang 621010 China School of Physics and Key Laboratory of Micro-nano Measurement-Manipulation and Physics Beihang University Beijing 100191 China NNU-SULI Thermal Energy Research Center (NSTER) & Center for Quantum Transport and Thermal Energy Science (CQTES) School of Physics and Technology Nanjing Normal University Nanjing 210023 China National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Nanjing 210093 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

Higher-order topological insulators have attracted great research interest recently. Different from conventional topological insulators, higher-order topological insulators do not necessarily require spin-orbit coupling, which makes it possible to realize them in spinless systems. Here, we study phonons in 2D graphyne family materials. By using first-principle calculations and topology/symmetry analysis, we find that phonons in both graphdiyne and γ-graphyne exhibit a second-order topology, which belongs to the specific case known as real Chern insulator. We identify the nontrivial phononic band gaps, which are characterized by nontrivial real Chern numbers enabled by the spacetime inversion symmetry. The protected phonon corner modes are verified by the calculation on a finite-size nanodisk. In addition, we show that a 3D real Chern insulator state can be realized for phonons in 3D graphdiyne. Our study extends the scope of higher-order topology to phonons in real materials. The spatially localized phonon modes could be useful for novel phononic applications.

关键词： First-principles calculations Phonons Topological insulators Topological materials

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Facile Preparation of Lightweight and Robust Carbon Aerogel Monoliths For High-Temperature Thermal Insulation and Oil-Water Separation

SSRN

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SSRN 2023年

作者： Li, Jian Sun, Bohui Zuo, Linxuan Qu, Linfeng Luo, Rui Pang, Shengyang Hu, Chenglong Zhao, Rida Liang, Bin Cheng, Hui-Ming Tang, Sufang Shi-Changxu Innovation Center for Advanced Materials Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China Shenyang Aircraft Design & Research Institute The Aviation Industry Corporation of China Ltd. Shenyang110035 China School of Materials Science and Engineering University of Science and Technology of China Shenyang110016 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China

Lightweight carbon aerogels (CAs) are urgently required for thermal insulation and organics absorption. However, a facile preparation method of ambient pressure drying (APD) remains a challenge since the large surface tension causes severe shrinkage, collapse or even cracking of porous network. Herein, a series of lightweight, robust and large-sized CA monoliths (0.240–0.327 g cm-3) are prepared through sol-gel polymerization of resorcinol-formaldehyde (RF) followed by solvent exchange-free APD using cotton fibers as reinforcement precursor. The deliberate tailoring of synthesis parameters and the appropriate introduction of cotton fibers jointly bring the advantages of facilitating sol-gel of RF solution, reducing drying shrinkage of hydrogels, and improving compatibility of carbonization shrinkage between fibers and matrix. Consequently, for instance, the CA composite with a density of 0.283 g cm-3, have high compressive strength (3.66 MPa), low thermal conductivity (0.070 W m-1 K-1), excellent hydrophobicity (water contact angle as high as 145°), and high-volume organic absorption capability (74.8–95.7%). The facile preparation of CA composites through solvent exchange-free APD with monomer polymerization should be a promising approach to their further application in thermal insulation and oil-water separation. © 2023, The Authors. All rights reserved.

关键词： Thermal insulation

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Emergent Anti-ferromagnetism in a Y-Shaped Kekulé Graphene

arXiv

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arXiv 2022年

作者： Wen, Chenyue Han, Wanpeng Feng, Xukun Zhu, Xingchuan Zhao, Weisheng Yang, Shengyuan A. Feng, Shiping Guo, Huaiming School of Physics Beihang University Beijing100191 China Fert Beijing Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and Engineering Beihang University Beijing100191 China Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore487372 Singapore Interdisciplinary Center for Fundamental and Frontier Sciences Nanjing University of Science and Technology Jiangsu Jiangyin214443 China Department of Physics Beijing Normal University Beijing100875 China

Antiferromagnetic (AF) transitions of birefringent Dirac fermions created by a Y-shaped Kekulé distortion in graphene are investigated by the mean-field theory and the determinant quantum Monte Carlo simulations. We show that the quantum critical point can be continuously tuned by the bond-modulation strength, and the universality of the quantum criticality remains in the Gross-Neveu-Heisenberg class. The critical interaction scales with the geometric average of the two velocities of the birefringent Dirac cones, and decreases monotonically between the uniform and the completely depleted limits. Since the AF critical interaction can be tuned to very small values, antiferromagnetism may emerge automatically, realizing the long-sought magnetism in graphene. These results enrich our understanding of the semimetal-AF transitions in Dirac-fermion systems, and open a new route to achieve magnetism in the graphene. Copyright © 2022, The Authors. All rights reserved.

关键词： Graphene

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Differential Evolution-Optimized Multi-Output Support Vector Regression-Based Prediction of Weld Bead Morphology in Wire-Fed Laser-Arc Directed Energy Deposition of 2319 Aluminum Alloy

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Additive Manufacturing Frontiers 2025年第2期4卷

作者： Li, Runsheng Ma, Hui Zeng, Kui Suo, Haoyuan Li, Chenyu Fu, Youheng Zhang, Mingbo Zhang, Maoyuan Fang, Xuewei College of Mechanical and Electronic Engineering China University of Petroleum (East China) Qingdao 266580 China The Ministry of Education Key Lab of Contemporary Design and Integrated Manufacturing Technolgy Northwestern Polytechnical University Xi'an 710072 China The State Key Laboratory for Manufacturing Systems Engineering School of Mechanical Engineering Xi'an Jiaotong University Xi'an 710054 China School of Material Science and Engineering Huazhong University of Science and Technology Wuhan 430070 China

Wire-fed laser-arc directed energy deposition (Wire-fed LA-DED) Technol. improves production speed while maintaining high quality and is particularly suited for manufacturing large, complex aluminum or titanium alloy components. The geometry of the weld bead (height and width) is influenced by multiple intricate parameters and variables during the manufacturing process. Accurately predicting the weld bead shape enables precise control over the surface flatness of the part, helping to prevent defects such as lack of fusion. This significantly reduces dimensional redundancy, enhances printing efficiency, and optimizes material usage. In this study, a quadratic regression prediction model for weld bead geometry was developed using the response surface methodology (RSM), with predictions generated through several machine learning models. These models included the backpropagation neural network (BPNN), support vector regression (SVR), multi-output support vector regression (MOSVR), extreme learning machine (ELM), and a differential evolution-optimized MOSVR (DE-MOSVR) model. Grid search and cross-validation techniques were utilized to identify the optimal parameters for each model to achieve the best predictive performance. A comparison of these models was conducted, followed by an evaluation of their generalization capabilities using an additional 20 sets of test data. The most accurate predictive model was selected based on a comprehensive assessment. The results showed that the DE-MOSVR model outperformed the others, achieving mean squared error, root mean squared error, mean absolute error, and R² values for width (height) predictions of 0.0411 (0.0041), 0.2028 (0.0639), 0.1671 (0.0550), and 0.9434 (0.9433), respectively. It demonstrated the smallest deviation in the validation set, with mean deviations of 1.97 % and 1.68 %, respectively. The model we developed was validated through the production of prototype parts, providing valuable reference and guidance for pred

关键词： 2319 aluminum alloy Differential evolution Geometry prediction Machine learning Wire-fed laser-arc directed energy deposition

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Deformation Mechanisms of Β-Li in Mg-Li Dual-Phase Alloy and Effects of Surface Oxide Layer

SSRN

引用

SSRN 2023年

作者： Li, Jing Jin, Li Yi, Sangbong Zhang, Xin Dong, Jie Luo, Ming Key Laboratory of High Performance Manufacturing for Aero Engine Northwestern Polytechnical University Ministry of Industry and Information Technology Xi’an710072 China Engineering Research Center of Advanced Manufacturing Technology for Aero Engine Ministry of Education Northwestern Polytechnical University Xi’an710072 China National Engineering Research Center of Light Alloy Net Forming State Key Laboratory of Metal Matrix Composite School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Institute of Materials and Process Design Helmholtz-Zentrum Hereon Geesthacht21502 Germany State Key Laboratory of Solidification Processing China

This study investigates the deformation mechanisms of β-Li micropillar prepared from a Mg-7Li dual-phase alloy with or without surface oxide layer. The oxide layer improves the strength of micropillar due to the dislocation trapping effect. As the oxide layer having a nanoporous structure becomes relatively thinner with increasing the micropillar size, the strengthening effect resulting from the oxide layer decreases with increasing the micropillar size. Regardless of the existence of the surface oxide layer, all β-Li micropillars show continuous deformation characteristics. This is ascribed to the interactions between pre-existing dislocations and non-planar dislocations activated during compression, which induces low-angle grain boundary and effectively traps the dislocations at the central area. © 2023, The Authors. All rights reserved.

关键词： Grain boundaries

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An optimized design method of three-point support for precision horizontal machining center with T-shape bed

Research Square

引用

Research Square 2021年

作者： Lin, Zixin Tian, Wenjie Zhang, Dawei Gao, Weiguo Wang, Lina Key Laboratory of Mechanism Theory Equipment Design of Ministry of Education Tianjin University Tianjin China School of Marine Science and Technology Tianjin University Tianjin China

The support point layout of the machine tool has an important influence on the working performance of the machine tool, when the material, manufacturing process and internal structure of machine bed are determined. In order to ensure that the precision machine tool has good leveling performance, stability and anti-interference, this paper presents an optimized design method of three-point support for T-shape bed of precision horizontal machining center. This article first establishes the statics model of the T-shape bed and analyzes grillage beam model used to characterize the main static deformation trend of the bed based on the singular function method. After verifying the rationality of the model through simulation, the optimized three-point support position can be obtained. Then this paper measured the deformation of the upper surface of a simple bed due to gravity. The deviation between the experimental results and the simulation results is less than 20%, which verifies the reliability of the simulation and theoretical results. Based on the ISIGHT multi-disciplinary optimization platform, this paper completes the multi-objective optimization of the support point layout of the bed, and the optimization results prove the accuracy of the theoretical model. This paper takes the bed of M800H precision horizontal machining center as an example to illustrate the application process of the proposed method. Finally, this paper compares the optimization effect of the static characteristics of the bed and the whole machine. The maximum deformation of the bed has reduced by 27.1%. In the whole machine status, the deformation of the spindle end has reduced by 50.8%, and the maximum deformation of the workpiece end have reduced by 50.0%. © 2021, CC BY.

关键词： Deformation

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Optimal scheduling in probabilistic imaginary-time evolution on a quantum computer

arXiv

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arXiv 2023年

作者： Nishi, Hirofumi Hamada, Koki Nishiya, Yusuke Kosugi, Taichi Matsushita, Yu-Ichiro Laboratory for Materials and Structures Institute of Innovative Research Tokyo Institute of Technology Yokohama226-8503 Japan Quemix Inc. Taiyo Life Nihombashi Building 2-11-2 Nihombashi Chuo-ku Tokyo103-0027 Japan Advanced course in Social Design Engineering National Institute of Technology Kochi College 200-1 Monobe Otsu Kochi Nankoku783-8508 Japan Quantum Material and Applications Research Center National Institutes for Quantum Science and Technology 2-12-1 Ookayama Meguro-ku Tokyo152-8552 Japan

Ground-state preparation is an important task in quantum computation. The probabilistic imaginary-time evolution (PITE) method is a promising candidate for preparing the ground state of the Hamiltonian, which comprises a single ancilla qubit and forward- and backward-controlled real-time evolution operators. The ground state preparation is a challenging task even in the quantum computation, classified as complexity-class quantum Merlin-Arthur. However, optimal parameters for PITE could potentially enhance the computational efficiency to a certain degree. In this study, we analyze the computational costs of the PITE method for both linear and exponential scheduling of the imaginary-time step size for reducing the computational cost. First, we analytically discuss an error defined as the closeness between the states acted on by exact and approximate imaginary-time evolution operators. The optimal imaginary-time step size and rate of change of imaginary time are also discussed. Subsequently, the analytical discussion is validated using numerical simulations for a one-dimensional Heisenberg chain. From the results, we find that linear scheduling works well in the case of unknown eigenvalues of the Hamiltonian. For a wide range of eigenstates, the linear scheduling returns smaller errors on average. However, the linearity of the scheduling causes problems for some specific energy regions of eigenstates. To avoid these problems, incorporating a certain level of nonlinearity into the scheduling, such as by inclusion of an exponential character, is preferable for reducing the computational costs of the PITE method. The findings of this study can make a significant contribute to the field of ground-state preparation of many-body Hamiltonians on quantum computers. Copyright © 2023, The Authors. All rights reserved.

关键词： Ground state

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An Intelligent Plant Landscape design Method Driven by Knowledge-graph

An Intelligent Plant Landscape Design Method Driven by Knowl...

引用

Networking Systems of AI (INSAI), International Conference on

作者： Jingwei Zhang Zhenping Xie School of Artificial Intelligence and Computer Science Jiangnan University Wuxi China Jiangsu Key Laboratory of Media Design and Software Technology Jiangnan University Wuxi China

ISBN: (纸本)9781665408608

With the general development of social economy, the quality of people's lives is constantly improving. Plant landscape is indispensable in urban gathering areas such as public parks and community squares. However, unreasonable design problems will cause a negative impact on the urban environment. Also, different scenes cause different requirements in the design concept and ecological setting technology for landscape designers. The intelligent landscape design method driven by the knowledge base proposed in this paper attempts to intelligently generate the layout of landscape plants and plant communities in a given scene. We build the knowledge base using the plant database, and take the data provided in the knowledge base as the basis and judgment condition for the plants' requirements for the environment. A rational inference and rule construction, in combination with the design principles of landscape architecture, is created to facilitate the arrangement of landscape plants.

关键词： Knowledge engineering Databases design methodology Knowledge based systems Urban areas Layout

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Topological hinge modes in Dirac semimetals

arXiv

引用

arXiv 2022年

作者： Zeng, Xu-Tao Chen, Ziyu Chen, Cong Liu, Bin-Bin Sheng, Xian-Lei Yang, Shengyuan A. School of Physics Beihang University Beijing100191 China Department of Physics The University of Hong Kong Hong Kong Hong Kong Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore487372 Singapore Center for Quantum Transport and Thermal Energy Science School of Physics and Technology Nanjing Normal University Nanjing210023 China

Dirac semimetals (DSMs) are an important class of topological states of matter. Here, focusing on DSMs of band inversion type, we investigate their boundary modes from the effective model perspective. We show that in order to properly capture the boundary modes, k-cubic terms must be included in the effective model, which would drive an evolution of surface degeneracy manifold from a nodal line to a nodal point. Using first-principles calculations, we demonstrate that this feature and the topological hinge modes can be clearly exhibited in β-CuI. We further extend the discussion to magnetic DSMs and show that the time-reversal symmetry breaking can gap out the surface bands and hence help to expose the hinge modes in the spectrum, which could be beneficial for the experimental detection of hinge modes. © 2022, CC BY.

关键词： Topology

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Influences of blade stiffness on structural natural frequencies of offshore wind turbine with monopile foundation

Influences of blade stiffness on structural natural frequenc...

引用

science and technology Innovation (IAECST), International Academic Exchange Conference on

作者： Shigang Shi Endi Zhai Chenshun Xu Yilong Sun Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of Technology Beijing China Offshore wind power design and Research Institute Goldwind Science and Technology Co. Ltd Beijing China

ISBN: (纸本)9781665402682

An elaborated structural numerical model of NREL 5MW offshore wind turbine (OWT) with monopile foundation is established by using the code of ABAQUS. The blade stiffness is adjusted by changing the elastic modulus of blade, and the influences of blade stiffness change on the natural frequency of the wind turbine (WT) structure are analyzed. The results show that the change of blade stiffness can significantly change the dynamic property of blade itself and supporting structure for WT in the FA (Fore-Aft) direction. For the 1st bending mode of supporting structure, the natural frequencies in the FA and SS (Side-to-Side) direction increase monotonically with the increasement of blade stiffness; in terms of the 2nd~5th bending modes of the supporting structure, the FA natural frequencies are more sensitive to the change of blade stiffness, while the SS natural frequencies are basically independent on blade stiffness.

关键词： Vibrations Technological innovation Codes Blades Bending Wind turbines Numerical models

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