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Understanding the flat band in 1T−TaS2 using a rotated basis

Physical Review B 2021年第24期104卷 L241114-L241114页

作者： Li Cheng Xuanyu Long Xiaobin Chen Xiaolong Zou Zheng Liu Shenzhen Geim Graphene Center (SGC) Tsinghua-Berkeley Shenzhen Institute (TBSI) and Tsinghua Shenzhen International Graduate School Tsinghua University Shenzhen 518055 China Institute for Advanced Study Tsinghua University Beijing 100084 China School of Science State Key Laboratory on Tunable Laser Technology and Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System Harbin Institute of Technology Shenzhen Shenzhen 518055 China

Electronic flat bands serve as a unique platform to achieve strongly correlated phases. The emergence of a flat band around the Fermi level in 1T−TaS2 accompanied by the development of a 13×13 charge density wave (CDW) superlattice has long been noticed experimentally, but a transparent theoretical understanding remains elusive. We show that without the CDW order, the primary feature of the 1×1 bands can be fitted by a simple trigonometric function, and physically understood by choosing a rotated t2g basis with the principal axes aligning to the tilted TaS6 octahedron. Using this basis, we trace the band evolution in the 13×13 superlattice by progressively including different CDW effects. We point out that the CDW order strongly rehybridizes the three t̃2g orbitals, which leads to the formation of a well-localized molecular orbital and the flat band.

关键词： Charge density waves Electronic structure Strongly correlated systems Transition metal dichalcogenides

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Adaptive Cruise Control of Virtual Coupled High-Speed Trains

Adaptive Cruise Control of Virtual Coupled High-Speed Trains

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Chinese Automation Congress (CAC)

作者： Di Wang Yuan Cao Shuai Su State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University The Center of National Railway Intelligent Transportation System Engineering and Technology China Academy of Railway Sciences Beijing China School of Electric and Information Engineering Beijing Jiaotong University Beijing China Frontiers Science Center for Smart High-Speed Railway System State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China

ISBN: (纸本)9781665426480

The adaptive cruise formation control problem for multiple high-speed trains (MHSTs) with input, speed and minimum tracking distance constraints under virtual coupling (VC) is proposed in this paper. First, the dynamic equation of MHSTs is created based on the law of kinematics. The communication topology is modeled by graph theory. Next, the speed limit, minimum tracking distance with adjacent trains are dealt with by using the ideas of the potential function. The resistance and unknown disturbances are dealt with by using adaptive control. Then, a cruise control protocol for MHSTs to track the expected trajectory is designed. The Lyapunov theory is used to prove the system stability. Finally, numerical experiments are conducted, which illustrates that the control protocol is effective.

关键词： Adaptation models Protocols Mathematical models Stability analysis Graph theory Trajectory Numerical models

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Flight planning system for UAV to collect 3D reconstruction data

Flight planning system for UAV to collect 3D reconstruction ...

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2020 International Conference on Virtual Reality and Visualization, ICVRV 2020

作者： Shi, Chu Luo, Xun Cadavid, Andres Navarro Lozano-Garzon, Carlos Alomia, Gustavo School of Computer Science and Engineering Tianjin University of Technology Tianjin China State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing China Faculty of Engineering Icesi University Cali Colombia Los Andes University Department of System Engineering and Computation Bogota Colombia

ISBN: (纸本)9780738142524

Small unmanned aerial vehicles (UAVs) can use their flexible maneuverability to effectively collect images of urban buildings, and use the current multi-view stereo method to generate advanced 3D urban models. But the quality of the generated 3D model largely depends on a flight plan. This paper proposes a method to automatically generate a rough 3D contour based on the 2D contour of the building extracted from the orthophoto of the drone, and plan a shooting viewpoint for 3D reconstruction based on the contour information. The optimized ant colony algorithm is used to plan the optimal power consumption cost path of the viewpoint, and the UE4 game engine is used to simulate the planning result. This method can effectively simplify the flight planning process and minimize the small UAV in the acquisition process The problem of excessive consumption caused by alternate lifting. © 2020 IEEE.

关键词： Image reconstruction

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Investigating Evolutions of Metro Station Functions in Shenzhen with Long-Term Smart Card Data 7th

Investigating Evolutions of Metro Station Functions in Shenz...

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7th International Conference on Geoinformatics in Sustainable Ecosystem and Society, GSES 2019, and 1st International Conference on Geospatial Artificial Intelligence for Urban Computing, GeoAI 2019

作者： Zhang, Fan Liu, Kang Yin, Ling Zhang, Fan Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen518055 China University of Chinese Academy of Sciences Beijing100049 China State Key Laboratory of Resources and Environmental Information System Beijing100101 China Shenzhen Institute of Beidou Applied Technology Shenzhen518055 China

ISBN: (纸本)9789811561054

The significances of urban metro stations are far more transport nodes in a city. Their surroundings are usually well developed and attract plentiful human activities, which support various functions in cities such as living and working. Investigating evolutions of metro station functions can help understand the developments of the stations as well as the whole city in a quick, low-cost, continuable and effective way. Using long-term smart card data collected from 2014 to 2018 of Shenzhen, China, this study identifies the functions of metro stations in different years, and reveals the evolution patterns of the functions over years, which is the first attempt as far as we know. The analytical results indicate that the function differentiations among stations have enlarged during those years;the cores of workplaces has shifted from Luohu to Futian and Nanshan district;the cores of residences have shifted to relatively peripheral districts such as Bao’an District, Longhua District and Longgang District;in general, the functions have evolved toward a more home-work-separation pattern. Those findings can help understand the changes of metro station functionalities, which are important clues for the governments to make better and sustainable public-transport and land-use policies. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Smart cards

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A hybrid-integrated external cavity laser with ultra-wide wavelength tuning range and high side-mode suppression

A hybrid-integrated external cavity laser with ultra-wide wa...

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Optical Fiber Communication (OFC) Conference

作者： Yuyao Guo Xinhang Li Weihan Xu Chuxin Liu Minhui Jin Liangjun Lu Jingya Xie Anton Stroganov Jianping Chen Linjie Zhou State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University Shanghai China SJTU-Pinghu Institute of Intelligent Optoelectronics Pinghu China Terahertz Technology Innovation Research Institute Terahertz Spectrum and Imaging Technology Cooperative Innovation Center Shanghai Key Lab of Modern Optical System University of Shanghai for Science and Technology Shanghai China LIGENTEC SA EPFL Innovation Park Bâtiment L Ecublens Switzerland

We present a III-V/Si 3 N 4 hybrid-integrated tunable laser. The laser shows a record of ~170-nm tuning range with a side mode suppression ratio above 64 dB and an intrinsic linewidth below 2.8 kHz. © 2022 The A... 详细信息

ISBN: (纸本)9781557524669

关键词： Performance evaluation Couplings Laser modes Optics Optical fiber communication Broadband communication Laser tuning

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The Impact Failure and Energy Dissipation Mechanism of Polyethylene Laminates

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Journal of Wuhan University of technology(Materials Science) 2019年第3期34卷 723-727页

作者： SHU Zaiqin ZHANG Jinyong State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Institute of Material Science and EngineeringWuhan University of TechnologyWuhan430070China System Design Institute of Hubei Aerospace Technology Academy Wuhan430040China

The damage mechanism and energy dissipation of the Polyethylene (PE) laminates in impacting was investigated. It was found that the dissipated energy of the impacting sphere bullet by the 1-mmthick PE plate firstly increased with the impacting velocity increasing from 50 to about 300 m/s, and then decreased with the impacting velocity increasing up to 600 m/s. According to the measured deformation and damage degree, a numerical simulation of the dissipated energy was made and obvious offset was found with the experimental results. The quasi-static properties of the PE fibers, decreasing with increase in tensile velocity, may be the main reason for the offset.

关键词： polyethylene ballistic impact energy dissipation strain rate

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10-Hertz quantum light source generation on the cesium D2 line using single photon modulation

arXiv

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arXiv 2022年

作者： Zuo, Guan-Hua Zhang, Yu-Chi Li, Gang Zhang, Peng-Fei Yang, Peng-Fei Guo, Yan-Qiang Zhu, Shi-Yao Zhang, Tian-Cai State Key Laboratory of Quantum Optics and Quantum Optics Devices Collaborative Innovation Center of Extreme Optics Institute of Opto-Electronics Shanxi University Taiyuan030006 China College of Physics and Electronic Engineering Shanxi University Taiyuan030006 China Department of Physics Zhejiang University Hangzhou310027 China Key Laboratory of Advanced Transducers and Intelligent Control System Ministry of Education and Shanxi Province College of Physics and Optoelectronics Taiyuan University of Technology Taiyuan030024 China

Generation of quantum light source is a promising technique to overcome the standard quantum limit in precision measurement. Here, we demonstrate an experimental generation of quadrature squeezing resonating on the cesium D2 line down to 10 Hz for the first time. The maximum squeezing in audio frequency band is 5.57 dB. Moreover, we have presented a single-photon modulation locking to control the squeezing angle, while effectively suppressing the influence of laser noise on low-frequency squeezing. The whole system operates steadily for hours. The generated low-frequency quantum light source can be applied in quantum metrology, light-matter interaction investigation and quantum memory in the audio frequency band and even below. Copyright © 2022, The Authors. All rights reserved.

关键词： Photons

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Peak and Valley Periods Partitioning Based on Improved K-medoids Algorithm

Peak and Valley Periods Partitioning Based on Improved K-med...

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Sustainable Power and Energy Conference (iSPEC)

作者： Wei Huang Lvbin Peng Yue Sun Jiahao Yan Kaibin Sun Xuan Li Xin Cheng Bo Hu Kaigui Xie State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing China

ISBN: (数字)9781728191645

ISBN: (纸本)9781728191652

The time of use (TOU) electricity pricing is one of the electric demand response (DR) strategies and has been widely used in the electrical power systems. The reasonable partitioning of peak, flat and valley periods is the prerequisite for setting the price of TOU. This paper proposes a peak-flat-valley (PFV) period partitioning model based on improved K-medoids algorithm. To address the instability problem of the divided periods caused by the random selection of initial centers in conventional clustering methods like k-means algorithm, the proposed model employs the maximum distance method to determine the initial center of each period. Then, the variation range for the center of each period can be obtained by the continuous nearest neighbor searching (CNNS) strategy, while improving the computation efficiency. A new criterion of partitioning is established based on Hausdorff distance and Euclidean distance, which is used in the particle swarm optimization (PSO) to optimize the period partitioning. Finally, case studies on IEEE reliability test system (RTS) demonstrate the effectiveness of the proposed model.

关键词： Computational modeling Clustering algorithms Pricing Power system stability Partitioning algorithms Power system reliability Reliability

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Enhancing Strength and Ductility of Mg-Gd-Zn Alloy by Trace Ti and Al Additions

SSRN

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SSRN 2022年

作者： Ding, Zhibing Zhang, Shuai Liu, Bin Hou, Hua Zhi, Xuanle Guo, Wenmin Chen, Dongrui Zhao, Yuhong College of Mechanical and Energy Engineering Shaoyang University Shaoyang422000 China Key Laboratory of Hunan Province for Efficient Power System and Intelligent Manufacturing Shaoyang University Shaoyang422000 China State Key Lab of Powder Metallurgy Central South University Changsha410083 China College of Materials Science and Engineering North University of China Taiyuan030051 China University of Science and Technology Beijing China

The effects of trace additions of Ti and Al on the microstructure and mechanical properties of Mg-Gd-Zn alloy were investigated. Trace Al addition can promote the generation of LPSO in Mg-Gd-Zn(-Ti) alloys. Trace Ti addition can not only effectively refine the microstructure of as-cast alloys, but also inhibit the growth of DRXed grains in as-rolled alloys. The maximum texture intensity of the as-rolled alloy is slightly weakened by the addition of trace Ti and Al. The aging hardening response can be improved by adding Ti, but decreased by adding Al. The fibrous 14H LPSO phases, refined DRXed grains, basal texture and fine precipitates endow the peaked-aged Mg-Gd-Zn-Al-Ti alloy with superior mechanical performance, its UTS, YTS and elongation are 486MPa, 402MPa and 8.7%, respectively. © 2022, The Authors. All rights reserved.

关键词： Gadolinium alloys

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Material state Identification of the Conveyor Belt based on Inception-v4

Material State Identification of the Conveyor Belt based on ...

引用

Chinese Automation Congress (CAC)

作者： Jinliang Tang Zhenyu Cai Chao Xu Tehuan Chen School of Mechanical Engineering and Mechanics Ningbo University Ningbo China System Integration Center Huzhou Institute of Zhejiang University Huzhou China State Key Laboratory of Industrial Control Technology Zhejiang University Hangzhou China

ISBN: (纸本)9781665426480

For the uneven phenomenon of materials during material transportation on the factory assembly line, this paper proposes an improved model based on Inception-v4 to realize the identification and classification of three material states (more materials, normal materials, and fewer materials). In the image processing stage, the Farneback algorithm is used to capture the moving area, which makes the training of the model focus on effective information. In addition, considering the color bias of materials, the RGB enhancement strategy is proposed. By processing the image data in RGB channels, different weights are given to realize the enhancement of image features. In the network training and testing stage, we use Inception-v4 as the baseline model. The output of the model is modified for the classification task, and a new loss function is designed. In addition, considering the limited sample size, we pre-trained the model on ImageNet. Through experimental comparison, the improved algorithm proposed in this paper has better performance.

关键词： Training Transfer learning Transportation Belts Feature extraction Production facilities Classification algorithms

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