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基于非厄米声学超材料的宽带相干完美吸收

仪器仪表学报 2024年第6期45卷 54-62页

作者：严雨婷杨京梁彬程建春南京大学物理学院近代声学教育部重点实验室人工微结构科学与技术协同创新中心南京210093

相干完美吸收只能在特定共振频率处或窄带实现完美吸收,这极大地限制了其在实际应用中发挥作用。近年来,非厄米调制和声学超材料的引入为复杂声波操控提供了全新的研究思路,并由此产生了许多在天然结构中难以实现的新颖的波与物质的相... 详细信息

相干完美吸收只能在特定共振频率处或窄带实现完美吸收,这极大地限制了其在实际应用中发挥作用。近年来,非厄米调制和声学超材料的引入为复杂声波操控提供了全新的研究思路,并由此产生了许多在天然结构中难以实现的新颖的波与物质的相互作用。本文提出一种非厄米声学亚波长腔管耦合模型,理论推导并展示了相干完美吸收的演化过程。通过调控系统的非厄米参数实现了两个相干完美吸收的简并,简并处带宽平均因子为12.825,且在输出谱图上观测到与之相应的宽带完美吸收特性。本文工作为基于非厄米声学超材料实现宽带相干完美吸收提供了一种新的途径,同时也为开发用于宽带声吸收、声检测等工程应用领域的新型功能性器件奠定了理论基础。

关键词：非厄米声超材料相干完美吸收宽带简并

Ultrasound focusing with metamaterial

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 125-126页

作者： jianchun cheng Key Laboratory of Modern Acoustics Ministry of EducationInstitute of AcousticsDepartment of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

Ultrasonic waves,although not audible,naturally exist at high *** can be controlled and unitized in various ***-known examples are bats and dolphins,which produce ultrasound and detect the reflected signal for navigat... 详细信息

关键词： reflected Ultrasound detect

The velocity field around two interacting cavitation bubbles in an ultrasound field

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1246-1252页

作者： WANG chengHui cheng jianchun Institute of Acoustics Nanjing University Institute of Applied Acoustics Shaanxi Normal University

A model is developed to calculate the distribution of first-order velocity field caused by the coupled bubbles in an ultrasound field. Using this model, numerical investigations of velocity field have been made when the two identical bubbles are driven well below resonance by an acoustic field with pressure amplitude exceeding cavitation threshold. Three representative kinestates of the coupled bubbles were chosen for analyzing the velocity distribution of surrounding liquid. The results show that the nonlinear oscillations of a bubble pair affect violently the radial velocity distribution of surrounding liquid, especially in the expanding phase. Symmetry of the tangential velocity distribution implies a possibility of attraction or repulsion of the bubble pairs.

关键词： cavitation bubbles bubble pairs velocity distribution

Experimental demonstration of a three-dimensional omnidirectional and broadband acoustic concentrator using an anisotropic metamaterial

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Science China(Physics,Mechanics & Astronomy) 2021年第4期64卷 17-24页

作者： chengBo Hu Bin Liang Jing Yang jianchun cheng Key Laboratory of Modern Acoustics Ministry of EducationInstitute of AcousticsDepartment of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

We report the theoretical design and experimental demonstration of a three-dimensional(3D)omnidirectional and broadband metamaterial-based concentrator for airborne *** proposed mechanism uses a homogeneous anisotropic acoustic metamaterial with an ellipsoidal equifrequency contour to efficiently redirect the acoustic energy impinging on its outer surface into the central region,regardless of the incident direction.A design of the metamaterial unit cell is proposed as a practical implementation of our strategy,which is simply realized by perforating a solid spherical shell with a linearly shrinking cross section in the radial *** analytically and numerically prove that the non-resonant anisotropic effective acoustic parameters required for building the concentrator are produced with such a *** agreement is observed between the theoretical predictions and experimental *** effective concentration of the incident acoustic energy is observed within a broadband that ranges 1000-1600 *** experimental realization of this 3D acoustic concentrator with a simple design,low energy loss,replaceable constituent material,and omnidirectional and broadband functionality offers new possibilities for acoustic manipulations and may have important applications in a plethora of scenarios ranging from energy harvesting to noise mitigation.

关键词： acoustic concentrator anisotropic metamaterial perforated hemispherical shell

High-efficiency unidirectional wavefront manipulation for broadband airborne sound with a planar device

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Chinese Physics B 2022年第3期31卷 342-349页

作者： Yang Tan Bin Liang jianchun cheng Key Laboratory of Modern Acoustics(Ministry of Education) Institute of AcousticsDepartment of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

In the past decade, one-way manipulation of sound has attracted rapidly growing attention with application potentials in a plethora of scenarios ranging from ultrasound imaging to noise control. Here we propose a design of a planar device capable of unidirectionally harnessing the transmitted wavefront for broadband airborne sound. Our mechanism is to use the broken spatial symmetry to give rise to different critical angles for plane waves incident along opposite *** the positive direction, the incoming sound is allowed to pass with high efficiency and be arbitrarily molded into the desired shape while any reversed wave undergoes a total reflection. We analytically derive the working bandwidth and incident angle range, and present a practical implementation of our strategy. The performance of our proposed device is demonstrated both theoretically and numerically via distinct examples of production of broadband anomalous refraction,acoustic focusing and non-diffractive beams for forward transmitted wave while virtually blocking the reversed *** advantages of simple design, planar profile, broad bandwidth and high efficiency, our design opens the possibility for novel one-way acoustic device and may have important impact on diverse applications in need of special control of airborne sound.

关键词： acoustic metamaterials one-way wavefront manipulation broadband planar device

MSEs Credit Risk Assessment Model Based on Federated Learning and Feature Selection

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Computers, Materials & Continua 2023年第6期75卷 5573-5595页

作者： Zhanyang Xu jianchun cheng Luofei cheng Xiaolong Xu Muhammad Bilal School of Computer and Software Nanjing University of Information Science&TechnologyNanjing210044China State Key Laboratory Novel Software Technology Nanjing UniversityNanjing210023China Department of Computer and Electronics Systems Engineering Hankuk University of Foreign StudiesYongin-siGyeonggi-do17035Korea

Federated learning has been used extensively in business inno-vation scenarios in various *** research adopts the federated learning approach for the first time to address the issue of bank-enterprise information asymmetry in the credit assessment ***,this research designs a credit risk assessment model based on federated learning and feature selection for micro and small enterprises(MSEs)using multi-dimensional enterprise data and multi-perspective enterprise *** proposed model includes four main processes:namely encrypted entity alignment,hybrid feature selection,secure multi-party computation,and global model ***,a two-step feature selection algorithm based on wrapper and filter is designed to construct the optimal feature set in multi-source heterogeneous data,which can provide excellent accuracy and *** addition,a local update screening strategy is proposed to select trustworthy model parameters for aggregation each time to ensure the quality of the global *** results of the study show that the model error rate is reduced by 6.22%and the recall rate is improved by 11.03%compared to the algorithms commonly used in credit risk research,significantly improving the ability to identify ***,the business operations of commercial banks are used to confirm the potential of the proposed model for real-world implementation.

关键词： Federated learning feature selection credit risk assessment MSEs

Controlling acoustic orbital angular momentum with artificial structures:From physics to application

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Chinese Physics B 2022年第9期31卷 41-55页

作者： Wei Wang Jingjing Liu Bin Liang jianchun cheng Key Laboratory of Modern Acoustics MOEInstitute of AcousticsDepartment of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

Acoustic orbital angular momentum(OAM)associated with helicoidal wavefront recently attracts rapidly-growing attentions,offering a new degree of freedom for acoustic *** to the unique dynamical behavior and inherent mode orthogonality of acoustic OAM,its harnessing is of fundamental interests for wave physics,with great potential in a plethora of *** recent advance in materials physics further boosts efforts into controlling OAM-carrying acoustic vortices,especially acoustic metasurfaces with planar profile and subwavelength *** to their un-conventional acoustic properties beyond attainable in the nature,acoustic artificial structures provide a powerful platform for new research paradigm for efficient generation and diverse manipulation of OAM in ways not possible before,enabling novel applications in diverse scenarios ranging from underwater communication to object *** this article,we present a comprehensive view of this emerging field by delineating the fundamental physics of OAM-metasurface interac-tion and recent advances in the generation,manipulation,and application of acoustic OAM based on artificial structures,followed by an outlook for promising future directions and potential practical applications.

关键词： acoustic orbital angular momentum acoustic metamaterials acoustic metasurfaces acoustic communications

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Editorial

Science China(Physics,Mechanics & Astronomy) 2021年第4期64卷 1-1页

Acoustic metamaterials are artificial materials composed of subwavelength building blocks with rationally-designed shape,geometry, size, and arrangement. They have emerged as excellent platforms for manipulating acous... 详细信息

关键词： arrangement rational geometry

NONLINEAR SCATTERING AND ATTENUATION OF FIRST SOUND IN SUPERFLUID ^(4)He AT HIGH FREQUENCY AND TEMPERATURE NEAR T_(λ)

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Chinese Physics Letters 1988年第6期5卷 261-264页

作者： cheng jianchun WEI Rongjue Institute of Acoustics Nanjing UniversityNanjing

The attenuation coefficient of the impressed first sound due to the scattering of random background of the second sound is *** result shows that this is an important factor which gives rise the attenuation of the first sound in the vicinity of transition temperature T_(λ) at very high frequencies of GHz *** predicted value agrees with the measured data in order of magnitude.

关键词： magnitude vicinity sound