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Efficient conversion of acoustic vortex using extremely anisotropic metasurface

Frontiers of physics 2024年第4期19卷 257-264页

作者： Zhanlei Hao Haojie Chen Yuhang Yin Cheng-Wei Qiu Shan Zhu Huanyang Chen Institute of Electromagnetics and Acoustics and Department of Physics College of Physical Science and TechnologyXiamen UniversityXiamen 361005China Department of Electrical and Computer Engineering National University of Singapore4 Engineering Drive 3117583Singapore Department of Mechanical and Electrical Engineering Xiamen UniversityXiamen 361005China Pen-Tung Sah Institute of Micro-Nano Science and Technology Xiamen UniversityXiamen 361005China

vortex wave and plane wave,as two most fundamental forms of wave propagation,are widely applied in various research ***,there is currently a lack of basic mechanism to enable arbitrary conversion between *** this paper,we propose a new paradigm of extremely anisotropic acoustic metasurface(AM)to achieve the efficient conversion from 2D vortex waves with arbitrary orbital angular momentum(OAM)to plane *** underlying physics of this conversion process is ensured by the symmetry shift of AM medium parameters and the directional compensation of ***,this novel phenomenon is further verified by analytical calculations,numerical demonstrations,and acoustic experiments,and the deflection angle and direction of the converted plane waves are qualitatively and quantitatively confirmed by a simple *** work provides new possibilities for arbitrary manipulation of acoustic vortex,and holds potential applications in acoustic communication and OAM-based devices.

关键词： efficient wave conversion vortex wave plane wave orbital angular momentum acoustic metasurface

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Mode Purity Improvement of High-Order vortex waves

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Chinese Journal of Electronics 2022年第6期31卷 1146-1154页

作者： LIN Jie YANG Guang LI Weiwen AN Cheng Department of Electronic Engineering Xiamen University

vortex electromagnetic waves can carry orbital angular momentum(OAM) modes of different order number, which are mutually orthogonal. Communication technologies multiplexing different OAM topological charges have attracted extensive attention in improving spectrum utilization. In this regard, the efficient generation of OAM modes becomes a key issue. However, it is difficult to generate high-order OAM modes by using a microstrip antenna with a simple structure, and the mode purity is usually not high. Methodologically, the OAM wave of a microstrip antenna is mostly achieved by synthesizing degenerate eigenmodes. In this paper, combined with eigenmode analysis, the construction of high-order and high-purity OAM mode microstrip antennas is carried out from the perspectives of radiating element,ground plane, and structural symmetry. For a regular hexagonal patch antenna of the 4th-order OAM mode,the mode purity is improved from about 40% to over 80%by removing the inner conductor of the patch layer, using a circular ground plane, and adding lug patches on the outside. This method of improving mode purity through the analysis of mode significance and characteristic current distribution also has guiding significance for the design of other high-order OAM mode patch antennas.

关键词： vortex wave Theory of characteristic modes Microstrip antenna Mode purity

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BUOYANCY INSTABILITY IN THE NATURAL CONVECTION BOUNDARY LAYER AROUND A VERTICAL HEATED FLAT PLATE

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Acta Mechanica Sinica 2002年第2期18卷 126-132页

作者：颜大椿张汉勋 Department of Mechanics and Engineering Science Peking UniversityBeijing 100871China

A systematic research on the buoyancy instability in the naturalconvection boundary layer was conducted,including the basic characteristics such asits spectral components,wave length and velocity,the location of its critical layer,and amplitude distributions of the triple independent eigenmodes with the linearinstability theory,the growth rates of its temperature and velocity fluctuations andthe corresponding neutral curves for the buoyancy eigenmode were also *** indicated that the neutral curve of the velocity fluctuation had a nose shapeconsistent with that obtained in the numerical calculation,but for the temperaturefluctuation,a ring-like region could be measured at a lower Grashof number beforethe nose-shaped main portion of the neutral curve.

关键词： buoyancy instability neutral curve vortex wave eigenmode thermal transition

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