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Chinese Physics Letters 2001年第12期18卷 1620-1623页

作者： YANG Jing cheng jian-chun State Key Laboratory of Modern Acoustics Nanjing UniversityNanjing 210093

A new inverse method based on the wavelet transform and artificial neural networks (ANN) is presented to recover elastic constants of a fibre-reinforced composite plate from laser-based ultrasonic Lamb waves. The transient waveforms obtained by numerical simulations under different elastic constants are taken as the input of the ANN for training and learning. The wavelet transform is employed for extracting the eigenvectors from the raw Lamb wave signals so as to simplify the structure of the ANN. Then these eigenvectors are input to a multi-layer internally recurrent neural network with a back-propagation algorithm. Finally, the experimental waveforms are used as the input in the whole system to inverse elastic constants of the experimental material.

关键词： material constants inverse

Laser-Generated Transient Lamb Wave in Thin Plates

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Chinese Physics Letters 1996年第1期13卷 24-27页

作者： WU Lei cheng jian-chun ZHANG Shu-yi Institute of Acoustics and Laboratory of Modern Acoustics Nanjing UniversityNanjing 210093

The laser-generated transient Lamb wave in thin isotropic plates is studied theoretically by employing the method of eigenfunction *** thermoelastic displacement field is expressed by symmetric and antisymmetnc Lamb wave modes,so that it is convenient to investigate thg transient excitation of the lowest and higher order Lamb wave *** characteristics of transient Lamb waves in thin materials with different thicknesses are discussed in details.

关键词： expansion transient wave

Thermoelastic Excitation of Transient Lamb Wave in an Orthotropic Thin Plate

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Chinese Physics Letters 1999年第3期16卷 187-189页

作者： cheng jian-chun FU Tao ZHANG Shu-yi Laboratory of Modern Acoustics and Institute of Acoustics Department of Electronic Science and EngineeringNanjing UniversityNanjing 210093

A numerical method to simulate thermoelastic excitation of transient Lamb wave propagating along arbitrary directions in orthotropic plates is presented by employing the expansion method of the Lamb wave *** displacement is expressed by a summation of the symmetric and antisymmetric modes in the surface stress-free orthotropic plate,and it is particularly suitable for waveform analyses of Lamb wave in orthotropic thin plates because one needs only to calculate the lowest few *** characteristics of dispersion and transient wave-forms are analyzed for a transversely isotropic *** results show that this method provides a quantitative analysis to Characterize anisotropic properties and elastic stiffness properties of the orthotropic plates by the laser-generated Lamb wave detection.

关键词： orthotropic wave transient

Nondestructive Characterization of Quantitative Bonding Strength at a Bonded Solid-Solid Interface

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Chinese Physics Letters 2011年第8期28卷 153-156页

作者： CHEN jian-Jun ZHANG De MAO Yi-Wei cheng jian-chun Institute of Acoustics Key Laboratory of Modern AcousticsNanjing UniversityNanjing 210093

We propose a nondestructive method to characterize the quantitative bonding strength at a bonded solid-solid interface by a contact acoustic nonlinearity(CAN)*** principle of the CAN microscope is briefly *** vibration amplitude of the incident focusing wave at the bonded interface is calculated,the standard bonding strength with a complete bonding state is established by the tension test,and the CAN parameter is *** quantitative contour of bonding strength at the interface could be *** experimental contours of two samples are also presented.

关键词： strength bonding interface

Broadband Acoustic Transmission Enhancement through a Structured Stiff Plate with Locally Resonant Elements

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Chinese Physics Letters 2012年第11期29卷 123-126页

作者： LI Yong LIANG Bin ZOU Xin-Ye cheng jian-chun Key Laboratory of Modern Acoustics MOEInstitute of AcousticsDepartment of PhysicsNanjing UniversityNanjing 210093 State Key Laboratory of Acoustics Chinese Academy of SciencesBeijing 100190

Broadband acoustic transmission enhancement(ATE)is realized for a periodically structured stiff plate without any opening that is conventionally thought to be only capable of supporting narrowband ATE,by introducing locally resonant(LR)*** exotic phenomenon is interpreted by analyzing the vibration pattern of the structure-induced LR modes,and is well modeled by a simple"spring-mass"system which reveals the contribution of the LR effect to the important broadband *** findings should help to better understand the physical mechanism of ATE and may have potential impact on ultrasonic applications such as broadband acoustic filters or compact acoustic devices in subwavelength scale.

关键词： Locally resonant stiff

Microstructure Effects of Ultrasonic Waves in a Fiber Reinforced Composite Plate

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Chinese Physics Letters 2000年第10期17卷 740-742页

作者： HAN Jun-Bo TANG Li-guo cheng jian-chun Yves Berthelot The State Key Laboratory of Modern Acoustics Nanjing UniversityNanjing 210093 School of Mechanical Engineering Georgia Institute of TechnologyAtlanta GA30332-0405USA

The microstructure effect of ultrasonic waves in a unidirectional titanium graphite composite is analyzed by the mode energy conversions of the laser-generated ultrasonic Lamb *** carrying energy of each mode in the Lamb wvaves is calculated quantitatively by the time-frequency filtering technique of the Wigner *** found that the energy conversions among modes have happened in the process of propagation of ultrasonic Lamb *** energy conversions are attributed to microstructure scattering of ultrasonic wave by the fibers in a fiber reinforced composite *** work will provide a quantitative method of ultrasonic characterizationof microstructure feature of the composite materials by the laser-generated Lamb wave technique.

关键词： composite microstructure Microstructure

Anisotropic Behavior Analyzed by Laser-Generated Lamb Waves for Fiber Composite Plates

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Chinese Physics Letters 1999年第7期16卷 518-519页

作者： cheng jian-chun HAN Jun-bo ZHANG Shu-yi Yves Berthelot Laboratory of Modern Acoustics and Institute of Acoustics Nanjing UniversityNanjing 210093 School of Mechanical Engineering Georgia Institute of Technology^AtlantaGA 30332USA

Analyses of the anisotropic behavior of a Uber composite plate from the laser-generated ultrasonic Lamb waveforms propagating in different directions are presented by employing wavelet transform *** time-frequency representation plots of the waveforms clearly exhibit the anisotropic behavior of the composite *** plots also indicate that the waveform mainly consists of three or four lower-order Lamb wave modes,and other higher-order modes can be neglected in extracting elastic stiffness properties by comparison of theory with experimental *** group velocity of each mode is calculated according to the group delay and the source-receiver distance.

关键词： composite anisotropic neglected

Ensemble projections of climate and streamflow in a typical basin of semi-arid steppes in Mongolian Plateau of 2021-2100

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Advances in Climate Change Research 2024年第2期15卷 230-243页

作者： Hang PAN jian-Ping TANG Liang cheng Man-chun LI jiangsu Provincial Key Laboratory of Geographic Information Science and Technology Nanjing UniversityNanjing 210023China School of Geography and Ocean Science Nanjing UniversityNanjing 210023China Key Laboratory of Mesoscale Severe Weather/Ministry of Education Nanjing UniversityNanjing 210023China School of Atmospheric Sciences Nanjing UniversityNanjing 210023China

The Kherlen River is the main water source for Hulun Lake,the largest lake in northern *** to reduced inflow from the Kherlen River,Hulun Lake experienced rapid shrinkage at the beginning of the 21st century,posing a serious threat to the ecological security of northern ***,there is still a significant lack of projections regarding future climate change and its hydrological response in the Kherlen River *** study analyzed the projected climate and streamflow changes in the Kherlen River basin,a vital yet vulnerable international semi-arid steppes type basin.A combination of multi-model ensemble projection techniques,and the soil and water assessment tool(SWAT)model was employed to examine the spatio-temporal changes in precipitation,temperature,streamflow,and the associated uncertainties in the *** temperature(an increase of 1.84-6.42℃)and the precipitation(an increase of 15.0-46.0 mm)of Kherlen River basin are projected to increase by 2100,leading to a rise in streamflow(1.08-4.78 m^(3) s^(-1)).The upstream of the Kherlen River exhibits remarkable increasing trends in precipitation,which has a dominant influence on streamflow of Kherlen *** increases in streamflow are observed in April,August,September,and October compared to the reference period(1971-2000).These findings suggest a partial alleviation of water scarcity in the Kherlen River,but also an increased likelihood of hydrological extreme *** projected temperature increase in the Kherlen River basin exhibits the smallest uncertainty,while more pronounced uncertainties are found in precipitation and *** spread among the results of CMIP6 models is greater than that of CMIP5 models,with lower signal-to-noise ratio(SNR)values for temperature,precipitation,and streamflow.

关键词： Climate change Flow projection Uncertainty SWAT Mongolian Plateau

Concealing a Passive Sensing System with Single-Negative Layers

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Chinese Physics Letters 2012年第1期29卷 109-112页

作者： ZHU Xue-Feng ZOU Xin-Ye ZHOU Xiao-Wei LIANG Bin cheng jian-chun Key Laboratory of Modern Acoustics(MOE) Institute of AcousticsDepartment of PhysicsNanjing UniversityNanjing 210093 Huazhong University of Science and Technology Wuhan 430074

We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped witha transparent protective layer),using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed *** numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak *** may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.

关键词： realization system. protective

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弹性管中泡群内气泡的非线性声响应

物理学报 2014年第13期63卷 209-215页

作者：王成会程建春陕西师范大学陕西省超声重点实验室西安710062 南京大学声学研究所南京210093

将弹性管壁视为膜弹性结构,得到了管径较大弹性管中泡群内气泡弱非线性振动的动力学模型.利用逐级近似法对气泡的非线性共振频率、基频振动响应特性进行了理论分析.结果表明:气泡共振频率主要受泡群内气泡间相互作用的影响;气泡的非线... 详细信息

将弹性管壁视为膜弹性结构,得到了管径较大弹性管中泡群内气泡弱非线性振动的动力学模型.利用逐级近似法对气泡的非线性共振频率、基频振动响应特性进行了理论分析.结果表明:气泡共振频率主要受泡群内气泡间相互作用的影响;气泡的非线性共振频率将发生偏移,其偏移量取决于共振响应振幅;气泡的声响应区存在最大频率值;在声响应的高频率区内声响应幅值有多值性.

关键词：弹性管非线性共振相互作用气泡声响应