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arXiv 2023年

作者： Liu, Gui-Geng Mandal, Subhaskar Zhou, Peiheng Xi, Xiang Banerjee, Rimi Hu, Yuan-Hang Wei, Minggui Wang, Maoren Wang, Qiang Gao, Zhen Chen, Hongsheng Yang, Yihao Chong, Yidong Zhang, Baile Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore637371 Singapore National Engineering Research Center of Electromagnetic Radiation Control Materials State Key Laboratory of Electronic Thin Film and Integrated Devices University of Electronic Science and Technology of China Chengdu610054 China Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen518055 China School of Physics Collaborative Innovation Center of Advanced Microstructures Nanjing University Jiangsu Nanjing210093 China Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Science and Technology Innovation Center College of Information Science and Electronic Engineering Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou310027 China Centre for Disruptive Photonic Technologies The Photonics Institute Nanyang Technological University 50 Nanyang Avenue Singapore639798 Singapore

Quantum Hall systems host chiral edge states extending along the one-dimensional boundary of any two-dimensional sample. In solid state materials, the edge states serve as perfectly robust transport channels that produce a quantised Hall conductance;due to their chirality, and the topological protection by the Chern number of the bulk bandstructure, they cannot be spatially localized by defects or disorder. Here, we show experimentally that the chiral edge states of a lossy quantum Hall system can be localized. In a gyromagnetic photonic crystal exhibiting the quantum Hall topological phase, an appropriately structured loss configuration imparts the edge states’ complex energy spectrum with a feature known as point-gap winding. This intrinsically non-Hermitian topological invariant is distinct from the Chern number invariant of the bulk (which remains intact) and induces mode localization via the "non-Hermitian skin effect". The interplay of the two topological phenomena – the Chern number and point-gap winding – gives rise to a non-Hermitian generalisation of the paradigmatic Chern-type bulk-boundary correspondence principle. Compared to previous realisations of the non-Hermitian skin effect, the skin modes in this system have superior robustness against local defects and disorders. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

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Enhancing the mechanical properties of carbonated CS through coupled carbonation-hydration: Synergistic effects of fiber growth and gel filling

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Construction and Building Materials 2025年 482卷

作者： Wei, Chengbo Tan, Ning Pang, Fangjie Zhu, Ruijian Wang, Zengmei State Key Laboratory of Engineering Materials for Major Infrastructure Jiangsu Key Lab. of Construction Materials School of Materials Science and Engineering Southeast University Nanjing211189 China School of Materials Science and Engineering Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing Institute of Technology Nanjing211167 China

The carbonation of α-CS (CaSiO₃) rapidly enhances its mechanical properties and sequesters CO₂, making it a promising ultra-low calcium CO₂-sequestering binder (LC-CSB). This study investigates the impact of varying amounts of β-C2S (β-Ca₂SiO₄) and C4A3S̅ (4CaO·3Al₂O₃·SO₃) on the mechanical properties and microstructure of α-CS during CO₂ curing and hydration. Mechanical properties, including compressive and flexural strengths, were measured, and the carbonation products and microstructural changes were analyzed using X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR).The results indicate that after 24 hours of carbonation, α-CS reacted with CO₂ to form calcite, while the addition of β-C2S and C4A3S̅ promoted the formation of aragonite whiskers and AFm (monosulfoaluminate), creating a more complex microstructure. After 28 days of standard hydration, AFm transformed into AFt (ettringite), significantly enhancing both compressive and flexural strengths. Specifically, samples containing 2 % and 5 % C4A3S̅ achieved compressive strengths of 126.17 MPa and 79.35 MPa, and flexural strengths of 9.07 MPa and 12.40 MPa, respectively, representing increases of 47.96 % and 102.25 % compared to the control samples. The improvement in strength is primarily attributed to the synergistic effects of carbonation and hydration. The formation of in-situ grown aragonite whiskers and interwoven AFt fibers during the carbonation-hydration coupling process provided a three-dimensional network structure that enhanced toughness and reduced porosity. Additionally, the hydration products of β-C₂S, particularly C-S-H gel, played a critical role in pore filling, further supporting the long-term development of mechanical properties. © 2025 Elsevier Ltd

关键词： Fourier transform infrared spectroscopy

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Analysis of control interaction between D-PMSGs-based wind farm and SVC

Analysis of control interaction between D-PMSGs-based wind f...

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作者： Chen, Yahao Huang, Biyue Sun, Haishun Wang, Long State Key Lab of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China

According to an accident analysis report, with regard to sub-synchronous oscillation (SSO) in Xinjiang, China, dynamic reactive compensation devices have great influence on the existence of sub-synchronous harmonics. This paper based on the practical phenomenon for further study, focuses on the interaction between direct-drive permanent synchronous generators (D-PMSGs)-based wind farm and static var compensator (SVC). Detailed electro-magnetic transient simulation model, such as D-PMSGs-based wind farm compensated by SVC, is established in PSCAD/EMTDC. Time-domain simulation results demonstrate that there is interaction between D-PMSGs-based wind farm and SVC, which is closely related with the control parameters of SVC and D-PMSGs-based wind farm. This type of control interaction will lead to sub-synchronous oscillation. Therefore, the influence of above control parameters on the oscillation characteristics is further studied here. The practical significance of this paper is indicating the necessity of coordinating and optimising control parameters in large-scale wind farm. © 2019 Institution of engineering and *** right reserved.

关键词： Static Var compensators

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Robust load frequency control and integration of electric vehicles and renewable energy in the grid 8

Robust load frequency control and integration of electric ve...

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8th Renewable Power Generation Conference, RPG 2019

作者： Khan, Musa Sun, Haishun Xiang, Yingmeng Shi, Di Wang, Yuling State Key Lab of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China San JoseCA95134 United States

ISBN: (纸本)9781839531255

The balancing of generation and demand, known as Load Frequency Control (LFC) is a key challenge as always, and currently it requires further attention due to the intermittent Renewable Energies (RE) and new form of Loads, Electric Vehicles (EV) in the grid. An effort is put forward by proposing a model where these worrisome generation' sources and loads can be integrated in the grid, while exploring their strengths. Beside the Conventional Sources (CS), in this model EVs take part in the LFC and RE provides inertial response. The multi objective LFC problem, is synthesised as a robust mixed H2/H∞ based on static output feedback control problem addressed by iterative linear matrix inequality technique. As a test case, a three-area system having EVs, REs and CSs, is simulated in Matlab.Simulink. The EVs, which pose a challenge as an extra load, would be managed to avoid the need of too much new installation of CS and would help the integration of REs like wind and solar energy in the grid. © 2019 Institution of engineering and technology. All rights reserved.

关键词： Iterative methods

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Type-II Dirac points and topological Fermi arcs in nonlocal metamaterials

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Physical Review B 2022年第23期106卷 235303-235303页

作者： Mingzhu Li Ning Han Liang Peng Shuang Zhang School of Information and Electrical Engineering Zhejiang University City College Hangzhou 310015 China Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China ZJU-Hangzhou Global Science and Technology Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou 310027 China Department of Physics University of Hong Kong Hong Kong China Department of Electrical & Electronic Engineering University of Hong Kong Hong Kong China

Dirac semimetals are topological materials with degenerated Dirac points in their band structures. In particular, the Dirac points play a central role in the topologically protected phases. Recently, it was reported that the peculiar type-II Dirac points could be realized in photonics by means of photonic crystals (PCs). Nevertheless, the practical implementation is rather challenging. In this paper, we demonstrate that the nonlocal effect in the interior of a homogeneous photonic metamaterial (HPM) enables the existence of type-II Dirac points in the HPM's band structure. With theoretical formulations and numerical evaluations, we discuss the evolution of the HPM's band type and present the interesting transition between type-I and type-II Dirac degeneracy of the HPMs. Remarkably, a pair of the type-II Dirac points can be generated at two different frequencies, which is supported by the mode overlapping in the HPMs with weak nonlocality. The Fermi arc surface states connect the projections of the type-II Dirac points at the boundary between the vacuum and HPMs. The topological protection of the Fermi arc surface states is verified by the reflectionless transmission with sharp corners. Our paper provides a fundamental understanding of topological photonics by type-II Dirac points in HPMs.

关键词： Surface states Topological phases of matter Dirac semimetal Topological materials

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Characteristics of sub-synchronous interaction among D-PMSG-based wind turbines

Characteristics of sub-synchronous interaction among D-PMSG-...

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作者： Liu, Yuming Wang, Long Sun, Haishun Huang, Biyue State Key Lab of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China

With the development of wind energy conversion system (WECS), sub-synchronous oscillations (SSO) phenomena have occurred in direct-drive permanent magnetic synchronous generators (D-PMSGs)-based wind farms. There are several studies on the analysis of the SSO worldwide. However few researchers are concern about the interaction among D-PMSGs. Considering the interaction among D-PMSGs, especially in the weak grid condition, some researches are conducted in this study. The model of D-PMSG is shown firstly. Then the simulations are carried out to research the characteristics of interaction among D-PMSGs. Control parameters of grid side converter and wind turbine (WT) operating conditions are taken into consideration. At last, a proper mitigation method is introduced. Meanwhile, the impact of interaction among WTs on the effect of mitigation method is studied. The simulation result shows that there are distinct interactions among D-PMSGs. The interactions among D-PMSGs need to be considered when coordinating the SSO mitigation control among D-PMSGs. © 2019 Institution of engineering and *** right reserved.

关键词： Synchronous generators

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Observation of Dirac hierarchy in three-dimensional acoustic topological insulators

arXiv

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arXiv 2022年

作者： Yang, Linyun Wang, Yin Meng, Yan Zhu, Zhenxiao Xi, Xiang Yan, Bei Lin, Shuxin Chen, Jingming Shi, Bin-Jie Ge, Yong Yuan, Shou-Qi Sun, Hong-Xiang Liu, Gui-Geng Yang, Yihao Gao, Zhen Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen518055 China Research Center of Fluid Machinery Engineering and Technology Faculty of Science Jiangsu University Zhenjiang212013 China State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences Beijing100190 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore Interdisciplinary Center for Quantum Information State Key Lab. of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China ZJU-Hangzhou Global Science and Technology Innovation Center Key Lab. of Advanced Micro Nano Electronic Devices & Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou310027 China

Dirac cones (DCs) play a pivotal role in various unique phenomena ranging from massless electrons in graphene to robust surface states in topological insulators (TIs). Recent studies have theoretically revealed a full Dirac hierarchy comprising an eightfold bulk DC, a fourfold surface DC, and a twofold hinge DC, associated with a hierarchy of topological phases including first-order to third-order three-dimensional (3D) topological insulators, using the same 3D base lattice. Here, we report the first experimental observation of the Dirac hierarchy in 3D acoustic TIs. Using acoustic measurements, we unambiguously reveal that lifting of multifold DCs in each hierarchy can induce two-dimensional (2D) topological surface states with a fourfold DC in a first-order 3D TI, one-dimensional (1D) topological hinge states with a twofold DC in a second-order 3D TI, and zero-dimensional (0D) topological corner states in a third-order 3D TI. Our work not only expands the fundamental research scope of Dirac physics, but also opens up a new route for multidimensional robust wave manipulation. Copyright © 2022, The Authors. All rights reserved.

关键词： Electric insulators

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Broadband electromagnetic Wave Tunneling with Transmuted Material Singularity

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Physical Review Letters 2020年第20期125卷 207401-207401页

作者： Yichao Liu Fei Sun Yibiao Yang Zhihui Chen Jianzhong Zhang Sailing He Yungui Ma Key Lab of Advanced Transducers and Intelligent Control System Ministry of Education and Shanxi Province College of Physics and Optoelectronics Taiyuan University of Technology Taiyuan 030024 China State Key Lab of Modern Optical Instrumentation Centre for Optical and Electromagnetic Research College of Optical Science and Engineering International Research Center for Advanced Photonics Zhejiang University Hangzhou 310058 China Department of Electromagnetic Engineering School of Electrical Engineering Royal Institute of Technology (KTH) S-100 44 Stockholm Sweden

Subwavelength channels filled with near-zero-index (NZI) media can realize extraordinary optical functionalities, for example, tunneling electromagnetic wave without reflections, but usually confined in a narrow wavelength band due to the material singularity (refractive index n≈0), which seriously limits the practical potentials. In this Letter, we show this limit can be fundamentally overcome by an alternative, named near-zero-index-featured (NZIF) structure, with the singularity transmuted via a controlled optical conformal mapping, enabling the device implementation with nonmagnetic normal dielectrics (i.e., relative permittivity >1). Their equivalence is strictly examined through a subwavelength tunneling waveguide. Classic wave tunneling features in a broad frequency range are revealed in various confined geometries. These properties are robust against the disturbance of several kinds of structural defects benefited from the infinite effective local wavelength. The broadband and lossless NZIF medium proposed here provides a promising way to pursue the fascinating light controlling functionalities as initially enabled by singular NZI materials.

关键词： Transformation optics Waveguides

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A New GaN Hybrid Resonant-Clamping Gate driver For High Frequency SiC MOSFETs

A New GaN Hybrid Resonant-Clamping Gate driver For High Freq...

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European Conference on Power Electronics and Applications

作者： Ziyue Dang Han Peng Hao Peng Yong Kang Yu Chen Xudan Liu Maojun He State Key Lab of Advanced Electromagnetic Engineering Technology Huazhong University of Science and Technology Wuhan Hubei State China Bosch (China) Investment Ltd. Changning Shanghai China

ISBN: (数字)9789075815368

ISBN: (纸本)9781728198071

Conventional resonant gate driver suffers from significant reverse recovery loss due to the usage of Si devices, especially at high frequencies. A novel hybrid resonant gate driver is proposed in this design composed by two hybrid GaN HEMT and Schottky diode half bridges. The hybrid topology merges the merits of efficient resonant turn on and ultra-fast turn off by GaN. The GaN based hybrid resonant-clamping gate driver achieves 29% reduction in gate driver active area. It also has 49.3% reduction in power loss is achieved compared with Si full bridge resonant gate driver.

关键词： Gallium nitride Gate drivers Silicon Silicon carbide Clamps Transient analysis

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Topological acoustics

arXiv

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arXiv 2023年

作者： Xue, Haoran Yang, Yihao Zhang, Baile Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering ZJU-Hangzhou Global Science and Technology Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang ZJU-UIUC Institute Zhejiang University Hangzhou310027 China Centre for Disruptive Photonic Technologies Nanyang Technological University Singapore637371 Singapore

Topological acoustics is an emerging field that lies at the intersection of condensed matter physics, mechanical structural design and acoustics engineering. It explores the design and construction of novel artificial structures, such as acoustic metamaterials and phononic crystals, to manipulate sound waves robustly, taking advantage of topological protection. Early work on topological acoustics was limited to duplicating topological phases that have been understood in condensed matter systems, but recent advances have shifted the paradigm to exploring novel topological concepts that are difficult to realize in other physical systems, such as various topological semimetal phases, and topological phases associated with Floquet engineering, fragile topology, non-Hermiticity and synthetic dimensions. These developments demonstrate the unique advantages of topological acoustic systems and their role in developing topological physics. In this Review, we survey the fundamental mechanisms, basic designs and practical realizations of topological phases in acoustic systems, and provide an overview of future directions and potential applications. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

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