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A Complex Hermitian Positive Definite Manifold Embedding Transformer Network for Time-Varying Direction of Arrival Tracking

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IEEE Transactions on Cognitive Communications and Networking 2025年

作者： Teng, Liping Wang, Qing Wang, Yanhui Guo, Qinghua Li, Wanqing Tianjin University School of Electrical and Information Engineering Tianjin300072 China Nantong University School of Information Science and Technology Nantong226019 China Science and Technology on Space Physics Laboratory Beijing100076 China University of Wollongong School of Electrical Computer and Telecommunications Engineering WollongongNSW2522 Australia University of Wollongong Advanced Multimedia Research Lab WollongongNSW2522 Australia

In this work, we address the challenge of stable and robust time-varying direction-of-arrival (DOA) tracking, where both the DOA trajectory and the number of sources change over time across different scenarios. We formulate the problem as a multi-label classification task and propose a novel solution leveraging Riemannian manifold geometry and advanced neural networks for sequential data processing. Specifically, we introduce the Complex Hermitian Positive Definite embedding Transformer (C-HPD-T) network, which learns statistical representations of covariance matrices. The C-HPD-T consists of an HPD module and a Transformer module. The HPD module learns an appropriate statistical representation and the complex Transformer module models the data temporally. In particular, in the C-HPD-T network, we build a complex singular value decomposition (SVD) module to ensure that complex structure is preserved during the calculation of each layer. Meanwhile, we design a Transformer-based sequential network to capture the temporal relationship of signals and for the time-varying DOAs. Through training the network with varying numbers of moving targets featuring diverse motion trajectories, the network demonstrates excellent performance and robustness against array imperfections. Extensive simulation results demonstrate its superior performance gains compared to existing methods. © 2015 IEEE.

关键词： Covariance matrix

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Roll-to-Roll Prelithiation of Li-Ion Batteries Anodes Using Ultrathin Lithium Strips

SSRN

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SSRN 2024年

作者： Yi, Ruowei Hu, Shoulei Zheng, Lei Li, Yifan Luo, Wenting Zhang, Haiyang Ge, Jun Shen, Yanbin Chen, Liwei i-Lab CAS Center for Excellence in Nanoscience Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Science Suzhou215123 China Nano Science and Technology Institute University of Science and Technology of China Suzhou215123 China School of Nano-Tech and Nano-Bionics University of Science and Technology of China Suzhou215123 China Vacuum Interconnected Nanotech Workstation Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences Suzhou215123 China In-situ Center for Physical Science School of Chemistry and Chemical Engineering Shanghai Jiaotong University Shanghai200240 China

The irreversible formation of solid electrolyte interphase (SEI) reduces lithium-ion batteries' capacity and energy density (LIBs), prompting the prelithiation strategies to compensate for the Li loss. However, the accuracy of the prelithiation degree and the SEI formation under prelithiation conditions remain key issues, especially for practical industrial production. Herein, we demonstrate that roll-to-roll prelithiation of graphite anodes can be done using ultrathin lithium strips (6-μm-thick), and the prelithiation degree can be precisely tuned by the topological distribution. More importantly, the formation of SEI during the prelithiation process and its influence on the long-term cycling performance of the prelithiated LiFePO4 || graphite pouch cells was revealed. Afterward, the prelithiated pouch LiFePO4 || graphite cell at the optimized conditions exhibits the upgraded energy density after even 1200 cycles. This study shall provide an industrial-scale prelithiation technique for high-energy-density LIBs and a pioneering systematic investigation of SEI chemistry during prelithiation. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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Effects of niobium doping on the charge density wave and electronic correlations in the kagome metal Cs(V1−xNbx)3Sb5

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Physical Review B 2023年第12期107卷 125124-125124页

作者： Xiaoxiang Zhou Yongkai Li Zhe Liu Jiahao Hao Yaomin Dai Zhiwei Wang Yugui Yao Hai-Hu Wen National Laboratory of Solid State Microstructures and Department of Physics Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems Beijing Institute of Technology Beijing 100081 China Material Science Center Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing 314011 China

The transport and optical properties of Nb-doped Cs(V1−xNbx)3Sb5 with x=0.03 and 0.07 have been investigated and compared with those of undoped CsV3Sb5. Upon Nb doping, the charge density wave (CDW) transition temperature TCDW is suppressed, and the superconducting temperature Tc rises. The residual resistivity ratio decreases with Nb doping, suggesting an increase of disorder. For all compounds, the optical conductivity in the pristine phase reveals two Drude components (D1 and D2). The substitution of Nb causes an increase of D1 alongside a reduction of D2 in weight, which implies a change of the Fermi surface. The total Drude weight is reduced with increasing Nb content, signifying an enhancement of electronic correlations. Below TCDW, while the optical conductivity clearly manifests the CDW gap in all materials, the gapped portion of the Fermi surface shrinks as the Nb content grows. A comprehensive analysis indicates that the change of the Fermi surface, the enhancement of electronic correlations, the shrinkage of the removed Fermi surface by the CDW gap, and the increase of disorder may all have a considerable impact on the interplay between the CDW and superconductivity in Cs(V1−xNbx)3Sb5.

关键词： Charge density waves Electronic structure Optical conductivity Strongly correlated systems Unconventional superconductors Infrared spectroscopy

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Enhanced broadband Cherenkov second-harmonic generation in nonlinear photonic crystals with a spatial chirped pulse

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Physical Review A 2024年第5期109卷 053513-053513页

作者： Bufan Jin Xuemei Wu Weimin Shen Zhi Hong Hang School of Physical Science and Technology and Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215006 China Institute for Advanced Study Soochow University Suzhou 215006 China Jiangsu Key Laboratory of Frontier Material Physics and Devices Suzhou 215006 China Key Lab of Modern Optical Technologies of Education Ministry of China School of Optoelectronic Science and Engineering Soochow University Suzhou 215006 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province School of Optoelectronic Science and Engineering Soochow University Suzhou 215006 China

In this work, we theoretically study the role of the spatial chirped pulse in the Cherenkov second-harmonic generation in one-dimensional nonlinear photonic crystals. We show that the spatial chirped input with narrower spectral peaks but wider angular distribution can be used to cancel the natural dispersion of crystals, fitting the phase-matching condition at wider emission angles. Contrary to popular belief, the phase-matching bandwidth can remain almost unchanged with the growth of interaction length, leading to a substantial increase in the signal strength and bandwidth under long interaction. The improvement ratio of the signal can be as high as needed, if the beam waist and the interaction length are large enough.

关键词： Nonlinear optics Phononic crystals Optical second-harmonic generation

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Laser Rapid Scanning Strategy for Bitmaps Via Image Segmentation Utilizing Grey Wolf Optimizer

SSRN

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SSRN 2023年

作者： Zhang, Tian Rong, Youmin Liu, Xiufeng Cao, Siyang Liang, Yufeng Wu, Congyi Zhang, Guojun Huang, Yu State Key Lab of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan China School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan China School of Physics and Electromechanical Engineering Hubei University of Education Wuhan China HGlaser Engineering Co. Ltd. Wuhan China

This study introduces a novel laser scanning processing methodology for bitmap aimed at reducing time losses arising from multiple galvanometer scanning cycles. The Multi-threshold Otsu method is employed and resolved using the gray wolf optimizer to effectively partition the target image into discernible background and target regions. To accommodate the resolved threshold distribution, four mapping functions with distinct growth trends are optimally selected and employed to modulate pixel gray values within specific regions into varying scanning input powers. An experimental investigation was conducted utilizing a galvanometer scanner and a set of sample images. Comparative analysis of image segmentation outcomes across multiple methodologies highlights the Gray Wolf optimizer's propensity for yielding the most robust segmentation results and solution stability. Coupled with the power mapping function, this new method exhibits notable adaptability to diverse graphical representations. Ultimately, the scanning process duration is reduced by as much as 89% when contrasted with traditional point carving and layer-by-layer scanning. This discovery signifies that the novel strategy holds significant promise for enhancing productivity in laser processing applications. © 2023, The Authors. All rights reserved.

关键词： Image segmentation

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Robust moiré flatbands within a broad band-offset range

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Advanced Photonics Nexus 2023年第6期2卷 7-13页

作者： Peilong Hong Yi Liang Zhigang Chen Guoquan Zhang University of Electronic Science and Technology of China School of Optoelectronic Science and EngineeringChengduChina Anqing Normal University School of Mathematics and PhysicsAnqingChina Nankai University TEDA Applied Physics InstituteSchool of PhysicsThe MOE Key Laboratory of Weak-Light Nonlinear PhotonicsTianjinChina Guangxi University School of Physical Science and TechnologyCenter on Nanoenergy ResearchGuangxi Key Lab for Relativistic AstrophysicsNanningChina

Photonic analogs of the moirésuperlattices mediated by interlayer electromagnetic coupling are expected to give rise to rich phenomena,such as nontrivial flatband ***,we propose and demonstrate a scheme to tune the flatbands in a bilayer moirésuperlattice by employing a band *** band offset is changed by fixing the bands of one slab while shifting those of the other slab,which is accomplished by modifying the thickness of the latter *** results show that the band-offset tuning not only makes some flatbands emerge and disappear but also leads to two sets of flatbands that are robustly formed even with the change of band offset over a broad *** robust flatbands form either at the AA-stack site or at the AB-stack site,and as a result,a single-cell superlattice can support a pair of high-quality localized modes with tunable ***,we develop a diagrammatic model to provide an intuitive insight into the formation of the robust *** work demonstrates a simple yet efficient way to design and control complex moiréflatbands,providing new opportunities to utilize photonic moirésuperlattices for advanced light–matter interaction,including lasing and nonlinear harmonic generation.

关键词： moirésuperlattice robust flatbands doubly resonant superlattice diagrammatic model

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Prediction of Electronic parameters of Carbon Nanotube random network Field-effect Transistors under liquid gated conditions using a machine learning approach

Prediction of Electronic parameters of Carbon Nanotube rando...

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2022 IEEE International Conference on Nanoelectronics, Nanophotonics, Nanomaterials, Nanobioscience and Nanotechnology, 5NANO 2022

作者： Murugathas, Thanihaichelvan Veena, R. Plank, Natalie O.V. Keerththinaathan, Pirunthan Petra, I. Mohandas, Prabu University of Jaffna Faculty of Science Department of Physics Jaffna40000 Sri Lanka Universiti Brunei Darussalam Faculty of Integrated Technologies BE1410 Brunei Victoria University of Wellington School of Chemical and Physical Sciences Wellington6021 New Zealand University of Jaffna Faculty of Technology Department of Electrical Technology Kilinochchi40000 Sri Lanka National Institute of Technology Calicut Intelligent Computing Lab Department of Computer Science and Engineering Kerala India

ISBN: (纸本)9781665437288

In this work, we employed a machine learning approach to predict the performance parameters of CNT bundle network field-effect transistors (FETs). The CNT bundle network FETs are complex system not only due to the random nature of the network but also due to the conductivity and work functions of bundles with both metallic and semiconducting tubes. It is difficult to model a whole network of CNT bundles with unknown conductivity and work function. In a recent work we examined 119 devices for investigate the role of CNT junctions in the electrical conduction and gating of CNT network FETs under liquid gated conditions. In this work we used the experimental data to train and predict the performance using the Support vector machine (SVM) technique. The CNT bundle density of the film measured by atomic force microscope images was used as the input parameter and the on-current, off-current and threshold voltage were the target. We were able to estimate the on current with an accuracy better than 90 percentage. However OFF current and threshold voltage prediction has an accuracy about 82 and 77 percent respectively. The 90-percentage accuracy for the on-current prediction can be attributed to the strong dependency of on-current with the CNT bundle density. However, the off-current and threshold voltage are depending on other parameters namely the presence of metallic CNTs within the bundles and the overall variations in the composition of network. Based on the experimental results, despite the unknown variables, we managed to predict the electronic parameters of a CNT network FETs with using the SVM techniques with significantly high accuracy. © 2022 IEEE.

关键词： Threshold voltage

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Quantum Tunneling Enhanced Hydrogen Desorption from Graphene Surface: Atomic versus Molecular Mechanism

arXiv

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arXiv 2025年

作者： Tong, Yangwu Yang, Yong Science Island Branch of Graduate School University of Science and Technology of China Hefei230026 China Key Lab of Photovoltaic and Energy Conservation Materials Institute of Solid State Physics HFIPS Chinese Academy of Sciences Hefei230031 China

We study the desorption mechanism of hydrogen isotopes from graphene surface using first-principles calculations, with focus on the effects of quantum tunneling. At low temperatures, quantum tunneling plays a dominant role in the desorption process of both hydrogen monomers and dimers. In the case of dimer desorption, two types of mechanisms, namely the traditional one-step desorption in the form of molecules (molecular mechanism), and the two-step desorption in the form of individual atoms (atomic mechanism) are studied and compared. For the ortho-dimers, the dominant desorption mechanism is found to switch from the molecular mechanism to the atomic mechanism above a critical temperature, which is respectively ~ 300 K and 200 K for H and D. © 2025, CC BY.

关键词： Atoms

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Probing angle-dependent thermal conductivity in twisted bilayer MoSe2

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Physical Review B 2023年第11期108卷 115439-115439页

作者： Manab Mandal Nikhilesh Maity Prahalad Kanti Barman Ashutosh Srivastava Abhishek K. Singh Pramoda K. Nayak Kanikrishnan Sethupathi Low temperature physics lab Department of Physics Indian Institute of Technology Madras Chennai 600 036 India Department of Physics Indian Institute of Technology Madras Chennai 600 036 India Materials Research Centre Indian Institute of Science Bangalore-560012 India 2D Materials Research and Innovation Group Indian Institute of Technology Madras Chennai-600036 India Centre for Nano and Material Sciences Jain (Deemed-to-be University) Jain Global Campus Kanakapura Bangalore 562112 India

Twisted bilayer (t-BL) transition-metal dichalcogenides (TMDCs) have attracted considerable attention in recent years due to their distinctive electronic properties, which arise due to the moiré superlattices that lead to the emergence of flat bands and correlated electron phenomena. Also, these materials can exhibit interesting thermal properties, including a reduction in thermal conductivity. In this paper, we report the thermal conductivity of monolayer (1L) and t-BL MoSe2 at some specific twist angles around two symmetric stacking AB (0∘) and AB′ (60∘) and one intermediate angle (31∘) using the optothermal Raman technique. The observed thermal conductivity values are found to be 13±1, 23±3, and 30±4Wm−1K−1 for twist angle [θ]=58∘, 31∘, and 3∘, respectively, which are well supported by our first-principles calculation results. The reduction in thermal conductivity in t-BL MoSe2 compared to monolayer (38±4Wm−1K−1) can be explained by the occurrence of phonon scattering caused by the formation of a moiré superlattice. Herein, the emergence of multiple folded phonon branches and modification in the Brillouin zone caused by in-plane rotation are also accountable for the decrease in thermal conductivity observed in t-BL MoSe2. The theoretical phonon lifetime study and electron localization function analysis further reveals the origin of angle-dependent thermal conductivity in t-BL MoSe2. This work paves the way towards tuning the angle-dependent thermal conductivity for any bilayer TMDCs system.

关键词： Density of states Excitons Phonons Thermal conductivity Thermal properties Thermoelectric effects Trions Twistronics 2-dimensional systems Energy applications Layered crystals Thermoelectrics Transition metal dichalcogenides Twisted heterostructures Atomic force microscopy Crystal growth Density functional theory First-principles calculations Optical microscopy Photoluminescence Raman spectroscopy

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Recent progress on photoactive nonprecious transition-metal complexes

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science China Chemistry 2025年第1期68卷 46-95页

作者： Zhong-Liang Gong Hong-Jie Zhang Yan Cheng Jianxun Liu Yuhan Ai Yaqin Li Zhihui Feng Qiong Zhang Shaolong Gong Yong Chen Chang-Jiang Yao Yuan-Yuan Zhu Liang-Jin Xu Yu-Wu Zhong CAS Key Laboratory of Photochemistry Institute of ChemistryChinese Academy of SciencesBeijing 100190China State Key Laboratory of Structural Cemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction EngineeringHefei University of TechnologyHefei 230009China State Key Laboratory of Explosion Science and Safety Protection School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China College of Chemistry and Molecular Sciences Hubei Key Lab on Organic and Polymeric Optoelectronic MaterialsWuhan UniversityWuhan 430072China School of Chemistry and Chemical Engineering Anhui UniversityHefei 230601China Key Laboratory of Photochemical Conversion and Optoelectronic Materials&CAS-HKU Joint Laboratory on New Materials Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Photoactive complexes of nonprecious transition metals,mainly including those in the first-row and partially the second-row of the Periodic table of elements,have received increasing attention in view of their low cost and long-term *** are recognized as promising alternatives to noble transition metal complex congeners that have been extensively studied in optoelectronic devices,artificial photosynthesis,photocatalysis,biodiagnostics,and therapeutics,*** review is devoted to a comprehensive summary on the classical and recent advances on photoactive nonprecious transition metal complexes,including photoactive Zr,V,Cr,Mo,and W complexes,Mn complexes and hybrids,Fe,Co,Ni,and Cu complexes,and Zn and Cd complexes and hybrids.A particular focus is given on the molecular design,modulation of photophysical and photochemical properties,and applications of the representative and lately-developed nonprecious metal *** addition,a perspective on the future development in this field is provided at the end of this review.

关键词： photoactive metal complexes earth-abundant metals nonprecious metal complexes luminescence photochemistry

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