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Representation of microscale ocean wavenumber spectrum correct to the second order

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Science China Earth Sciences 2005年第4期48卷 549-554页

作者： YUAN Yeli2 & HUA Feng1,2,3 1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China 2. Key Laboratory of Marine Science and Numerical Modeling, State Oceanic Administration, Qingdao 266061, China 3. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China Key Laboratory of Marine Science and Numerical Modeling State Oceanic Administration Qingdao China Institute of Oceanology Chinese Academy of Sciences Qingdao China Graduate School of the Chinese Academy of Sciences Beijing China

In this paper, the analytical representations of four wave source functions in high-frequency spectrum range are given on the basis of ocean wave theory and dimensional analysis, and the perturbation method is used to solve the governing equations of ocean wave high-frequency spectrum on the basis of the temporally stationary and locally homogeneous scale relations of microscale wave. The microscale ocean wavenumber spectrum correct to the second order has an explicit structure, its first order part represents the equilibrium between dif- ferent source functions, and its second order part represents the contribution of microscale wave propagation.

关键词： temporally stationary and locally homogeneous, source function in high-frequency spectrum range, microscale ocean wavenumber spectrum.

Quantitative Rectangular Notch Detection of Laser-induced Lamb Waves in Aluminium Plates with wavenumber Analysis

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 244-255页

作者： Liu Zenghua Feng Xuejian He Cunfu Wu Bin College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing Engineering Research Center of Precision Measurement Technology and Instruments Beijing University of Technology

It is difficult to quantitatively detect defects by using the time domain or frequency domain features of Lamb wave signals due to their dispersion and multimodal characteristics.Therefore,it is important to discover an intrinsical parameter of Lamb waves that could be used as a damage sensitive feature.In this paper,quantitative defect detection in aluminium plates is carried out by means of wavenumber analysis approach.The wavenumber of excited Lamb wave mode is a fixed value,given a frequency,a thickness and material properties of the target plate.When Lamb waves propagate to the structural discontinuity,new wavenumber components are created by abrupt wavefield change.The new wavenumber components can be identified in the frequency-wavenumber domain.To estimate spatially dependent wavenumber values,a short-space two-dimensional Fourier transform(FT)method is presented for processing wavefield data of Lamb waves.The results can be used to determine the location,size and depth of rectangular notch.The analysis techniques are demonstrated using simulation examples of an aluminium plate with a rectangular notch.Then,the wavenumber analysis method is applied to simulation data that are obtained through a range of notch depths and widths.The results are analyzed and rules of the technique with regards to estimating notch depth are determined.Based on simulation results,guidelines for using the technique are developed.Finally,experimental wavefield data are obtained in aluminium plates with rectangular notches by a full noncontact transceiving method,i.e.,laser-laser method.Band-pass filtering combined with continuous wavelet transform is used to extract a certain frequency component from the full laser-induced wavefield with wide band.Shortspace two-dimensional FT method is used for further processing full wavefield data at a certain frequency to estimate spatially dependent wavenumber values.The consistency of simulation and experimental results shows the effectiveness of proposed wavenumber method for quantitative

关键词： wavenumber analysis short space two-dimensional Fourier transform(FT) notch aluminium plate

Modal Wave Number Tomography for South China Sea Front

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海洋工程：英文版 2003年第2期17卷 289-294页

作者：彭临慧王宁邱晓芳田纪伟 Physics Department Ocean University of China College of Physical and Environmental Oceanography Ocean University of China

Monitoring of the South China Sea is always one of the focuses in the field of ocean engineering for its particular geographic position. The modal wave number tomography is proposed for monitoring the front and numerical simulation is performed for the front of the South China Sea. With the empirical orthonormal function (EOF) applied to reduce the parameter search space, the perturbation inversion method is used for inversing sound speed profiles. The 2-D ocean environment used for numerical simulation is selected from the ocean area, located in 20°N, 118°E～20°N, 125°E, near the Luzon Strait in the South China Sea. The ocean environment sound speed distribution in the ocean area under study is obtained from the assimilation of multi-source remote sensing data. The numerical simulation shows that the modal wave number tomography can inverse the average sound speed profile, therefore,it can be used to monitor ocean internal structures such as ocean fronts and eddies which affect sound speed distribution.

关键词： front wavenumber tomography monitoring

SOLUTION OF ARBITRARY CROSS-SECTION WAVEGUIDE USING METHOD OF EIGEN WEIGHTED BOUNDARY INTEGRAL EQUATION

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Journal of Electronics(China) 1990年第3期7卷 258-262页

作者：祝雷章文勋 Southeast University Nanjing

Based on the second kind of Green’s identity,a boundary integral equation forarbitrary cross-section waveguide is transformed to a system of linear homogeneous algebraicequations by means of expansion of boundary bases and by using the eigenfunctions of a fictitiousregular boundary as weighting functions,which corresponds to less algebraic equations than BEMand simpler coefficients than the modified BEM.The numerical results for some typical metallicwaveguides are given by using the method of eigen-weighted boundary integral equation,and theyare accurate enough with fast convergence.

关键词： Boundary integral method Metallic waveguide Eigenvalue problem Cut-off wavenumber Boundary value problem

起伏面磁场及其梯度张量快速三维正演方法（英文）

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Applied Geophysics 2018年第3期15卷 500-512页

作者：李昆陈龙伟陈轻蕊戴世坤张钱江赵东东凌嘉宣 Hunan Key Laboratory of Nonferrous Resources and Geological Hazards Exploration Changsha 410083China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring of Ministry of Education Central South UniversityChangsha 410083China School of Geosciences and Info-Physics of Central South University Changsha 410083China School of College of Earth Sciences of Guilin University of Technology Guilin 541004China

随着磁梯度张量测量技术迅速发展,为实现精细反演地下磁化率分布提供了数据保障。基于航空和陆地磁测数据的三维磁化率反演需要计算起伏面上的磁场,因此研究起伏面磁场及其梯度张量快速三维正演方法具有重要实际应用价值。针对任意磁化... 详细信息

随着磁梯度张量测量技术迅速发展,为实现精细反演地下磁化率分布提供了数据保障。基于航空和陆地磁测数据的三维磁化率反演需要计算起伏面上的磁场,因此研究起伏面磁场及其梯度张量快速三维正演方法具有重要实际应用价值。针对任意磁化率分布、起伏面磁场及其梯度张量三维正演问题,本文提出了一种快速波数域三维正演方法,其关键环节包括:(1)结合棱柱体组合模型波数域表达式和Gauss-FFT算法,提出一种任意磁化分布情况下平面磁场及其梯度张量快速三维正演算法;(2)利用平面三维正演算法,计算多个高度平面磁场及其梯度张量,结合三次样条插值方法,实现起伏面磁场及其梯度张量三维正演。在此过程中,提出一种多个高度面情况下波数域加权系数快速计算方法,进一步提高了起伏面情况下三维正演的计算效率。通过设计不同模型算例,验证了新方法的计算精度和效率。

关键词： Undulated surface magnetic fi eld gradient tensor 3D forward modeling Gauss– FFT algorithm wavenumber domain

A Semi-Analytical Method for the Solution of Helmholtz Equation

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Journal of Applied Mathematics and Physics 2013年第5期1卷 54-57页

作者： M. Tadi Department of Mechanical Engineering University of Colorado at Denver Denver USA

This note is concerned with a semi-analytical method for the solution of 2-D Helmholtz equation in unit square. The method uses orthogonal functions to project the problem down to finite dimensional space. After the projection, the problem simplifies to that of obtaining solutions for second order constant coefficient differential equations which can be done analytically. Numerical results indicate that the method is particularly useful for very high wave numbers.

关键词： Helmholtz Equation Elliptic Systems High wavenumber

0.14 THz imaging system for security and surveillance

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太赫兹科学与电子信息学报 2017年第4期15卷 539-542页

作者： ZHAO Yujiao DENG Xianjin CHENG Binbin LIU Jie Microsystem and Terahertz Research Center China Academy of Engineering Physics Institute of Electronic Engineering China Academy of Engineering Physics

Active terahertz-wave imaging systems play a significant role in security and surveillance applications.A 0.14 THz near-field imaging system is described,which consists of a signal generator and acquisition unit,a transceiver front end,a digital signal process unit and a motor control unit.Based on the two-dimensional synthetic aperture technique and the image reconstruction algorithm,this system is capable of producing three-dimensional images of 2 mm lateral resolution and 3 cm range resolution in concealed weapon detection experiments.

关键词： terahertz-wave personnel surveillance reconstruction wavenumber