共查询到20条相似文献,搜索用时 515 毫秒
1.
Most of the structural health monitoring (SHM) methods is either based on vibration-based and contact acoustic emission (AE) techniques. Both vibration-based and acoustic emission techniques require attaching transducers to structure. In many applications, such as those involving hot structural materials for thermal protection purposes or in rotating machines, non-contact measurements would be preferred because the operating environment is prohibitive leading to potential damage in contact sensors or their attachments. In this paper, a new non-contact, acoustic-based damage detection method is proposed and tested with an objective that the proposed method is able to detect the location and extend of damage accurately. The proposed acoustic-based damage detection method is a direct method. In this proposed method, changes in vibro-acoustics flexibility matrices of the damage and health structure are used to predict the location and extend of damage in the structure. A case study involving actual measured date for the case of a fixed–fixed plate structure is used to evaluate the effectiveness of the proposed method. The results have shown that the proposed acoustic-based damage detection method can be used to detect the location and extend of the damage accurately. 相似文献
2.
A numerical-experimental hybrid method for the stress separation in the digital gradient sensing (DGS) method is proposed in this study. In the proposed hybrid method, boundary conditions for a local finite element model, that is, nodal force along boundaries are inversely determined from experimental values obtained by the digital gradient sensing method. The hybrid method follows two stages. In stage 1, the DGS method measures the Cartesian stress gradient components directly and, subsequently, the sum in Cartesian stresses at all interesting points on the surface; stress sum are used to compute the unknown boundary conditions for the local model. In stage 2, the individual stress components are calculated by the direct finite element method using the computed boundary conditions from stage 1. The effectiveness is demonstrated by applying the proposed method to a stress concentration problem involving concentrated load acting on an edge of a large planar sheet. The individual stress components thus determined are summed and compared with analytical stress sum, confirming the effectiveness and accuracy of the proposed technique. 相似文献
3.
Phase unwrapping is one of the most challenging processes in many profilometry techniques. To sidestep the phase unwrapping process, Perciante et al. (2015) proposed a wrapping-free method to retrieve the phase based on the direct integration of the spatial derivatives of the fringe patterns. However, this method is only applicable to objects with phase continuity, so it may fail to handle fringe patterns containing complicated singularities such as noise, shadows, shears and surface discontinuities. In the light of this problems, a robust wrapping-free phase retrieval method is proposed that is based on the combined use of Perciante's method and the weighted least squares method. Two partial derivatives of the desired phase are obtained from the fringe patterns, while the carrier is eliminated using the direct phase difference method. The phase singularities are determined using a derivative variance correlation map (DVCM), and the weighting coefficient is obtained from the binary mask of the reverse DVCM. Simulations and experiments are conducted to prove the validity of the proposed method. The results are analyzed and compared with those of Perciante's method demonstrating that in addition to maintaining the advantage of sidestepping the phase unwrapping process, the proposed method is available for measuring objects with some types of singularities sources. 相似文献
4.
B. S. Ishkhanov A. S. Kurilik D. S. Rudenko K. A. Stopani V. I. Shvedunov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(6):859-862
A multiple-beam method for scanning large objects is proposed, which is based on the use of multiple bremsstrahlung beams with different upper limits. Mathematical modeling is performed to compare the multiple-beam method with the double-beam method, and an advantage of the proposed technique over the double-beam method method is shown. 相似文献
5.
《Journal of computational physics》2008,227(1):264-278
An incompressible multi-phase SPH method is proposed. In this method, a fractional time-step method is introduced to enforce both the zero-density-variation condition and the velocity-divergence-free condition at each full time-step. To obtain sharp density and viscosity discontinuities in an incompressible multi-phase flow a new multi-phase projection formulation, in which the discretized gradient and divergence operators do not require a differentiable density or viscosity field is proposed. Numerical examples for Taylor–Green flow, capillary waves, drop deformation in shear flows and for Rayleigh–Taylor instability are presented and compared to theoretical solutions or references from literature. The results suggest good accuracy and convergence properties of the proposed method. 相似文献
6.
We propose an explicit multi-symplectic method to solve the two-dimensional Zakharov-Kuznetsov equation. The method combines the multi-symplectic Fourier pseudospectral method for spatial discretization and the Euler method for temporal discretization. It is verified that the proposed method has corresponding discrete multi-symplectic conservation laws. Numerical simulations indicate that the proposed scheme is characterized by excellent conservation. 相似文献
7.
Load identification, as a kind of indirect identification method, uses system characteristic and responses to calculate loads. A method based on wavelet multi-resolution analysis is proposed in this paper. By wavelet decomposition and transform at certain resolutions, the proposed method transforms the convolution relation between responses and loads in time domain into the linear multiplicative relation between system responses and wavelet responses in the wavelet domain. Loads can be identified as long as the linear multiplicative relation is solved. Qualitative and quantitative rules are proposed for selecting parameters that affect the accuracy of the proposed method, and are illustrated via numerical investigations. The method is illustrated by a multi-input-multi-output numerical simulation. A multi-input-multi-output laboratory experiment is performed to compare the proposed method with the frequency method on the identification ability. 相似文献
8.
9.
全息声压外推是Patch近场声全息技术的关键步骤.本文提出了全息声压的加权范数外推方法,该方法首先通过实测声压数据的功率谱信息构造频域加权范数,然后通过极小化频域加权范数实现全息声压外推.由于外推过程中同时利用了声压信号的波数域带宽和波数谱形状信息,因此其外推结果优于传统带限外推方法.数值仿真结果表明,该方法无论在外推精度还是计算效率上都明显优于经典的全息声压波数域外推方法.刚性箱体上的声激励固支板声压外推实验进一步验证了该方法的有效性和实用性.
关键词:
近场声全息
全息声压外推
加权范数 相似文献
10.
A novel image fusion algorithm based on wavelet-based contourlet transform (WBCT) and principal component analysis (PCA) is proposed. The PCA method is adopted for the low-frequency components. Using the proposed algorithm to choose the greater of the active measures, the region consistency test is performed for the high-frequency components. Experiments show that the proposed method works better in preserving the edge and texture information than wavelet transform method and Laplacian pyramid (LP) method do in image fusion. Four indicators for the fusion image are given to compare the proposed method with other methods. 相似文献
11.
In a color-to-gray conversion, which only considers lightness components, difference of colors are not appropriately reflected in monochrome images. Gooch et al. have proposed a color removal method that considers the differences of colors. Although the method can obtain good results in many cases, there is room for improvement. In this paper, a new color removal method that introduces a weight to Gooch’s algorithm is proposed. In the proposed method, for combinations of colors of each pixel in an input image, weights are determined by distance in color space. In the proposed method, unimportant color combinations are not considered by weight and color information in an input image is appropriately reflected in a monochrome image. The validity of the proposed method is shown by experiments using some images. 相似文献
12.
13.
14.
Science China Physics, Mechanics & Astronomy - A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using... 相似文献
15.
Color transfer originally proposed by Reinhard et al. is a method to change the color appearance of an input image by using the color information of a reference image. The purpose of this study is to modify color transfer so that it works well even when the scenes of the input and reference images are not similar. Concretely, a color transfer method with lightness correction and color gamut adjustment is proposed. The lightness correction is applied to preserve the perceived lightness which is explained by the Helmholtz–Kohlrausch (H–K) effect. This effect is the phenomenon that vivid colors are perceived as brighter than dull colors with the same lightness. Hence, when the chroma is changed by image processing, the perceived lightness is also changed even if the physical lightness is preserved after the image processing. In the proposed method, by considering the H–K effect, color transfer that preserves the perceived lightness after processing is realized. Furthermore, color gamut adjustment is introduced to address the color gamut problem, which is caused by color space conversion. The effectiveness of the proposed method is verified by performing some experiments. 相似文献
16.
A new method is proposed to simulate the Kolmogorov phase screen. A hybrid phase screen is achieved by linearly combining two phase screens simulated by both spectral and Zernike polynomials methods. Unlike the imperfection of phase structure function existing at some spatial frequencies in each of the two methods, the mean structure function of the hybrid phase screens coincides remarkably well with theory in the whole spatial frequency domain. Apart from advantage on accuracy, the proposed method also saves considerable computational time. For a phase screen with certain accuracy, the new method is ten times and seven times faster compared with the spectral method and Zernike polynomials method, respectively. 相似文献
17.
The ability of measuring colors of objects, independent of light source illumination, is called color constancy which is an
important problem in machine vision and image processing fields. In this paper, we propose a new combinational method that
is based on fuzzy measures and integrals to estimate the chromaticity of the light source as the major step of color constancy.
The basic idea of the proposed method is that there are color constancy methods with some similarities in their structure
and the way they are applied. The proposed method works with the help of assigning fuzzy measures to these methods and their
combinations and computing the Choquet fuzzy integral. To approve the proposed method, we selected four well known algorithms
and their results were combined by the proposed approach. In selecting these methods, it was tried to choose the ones which
had better performance in compare to other methods, however the proposed method can be applied on any other methods just by
adjusting its parameters. It is shown in this article that proposed approach performs better than other proposed methods for
color constancy most of the time. 相似文献
18.
《中国物理 B》2015,(6)
A novel two-dimensional(2D) simulation method of positive corona current pulses is proposed.A control-volumebased finite element method(CV-FEM) is used to solve continuity equations,and the Galerkin finite element method(FEM) is used to solve Poisson's equation.In the proposed method,photoionization is considered by adopting an exact Helmholtz photoionization model.Furthermore,fully implicit discretization and variable time step are used to ensure the time-efficiency of the present method.Finally,the method is applied to a positive rod-plane corona problem.The numerical results are in agreement with the experimental results,and the validity of the proposed method is verified. 相似文献
19.
In the paper, a multiframe blind image deconvolution method based on total variation and framelet regularizer is proposed. An adapted version of the split Bregman method is proposed to efficiently solve the resulting minimization problems. In each iteration, four sub-problems need to be solved, one of which can be very efficiently and easily solved via fast Fourier transform implementation or closed form solution. Both simulated noisy and blurred frames and real degraded frames are used to verify the effectiveness of the proposed method. Comparative experimental results show that the proposed method can efficiently remove the blur and noises and restore high quality sharp image. 相似文献
20.
Potentialities of passive acoustic thermal tomography in reconstructing the 2D temperature distribution in a human body are studied. Special attention is given to the estimation of the maximal temperature value. A method for its exact reconstruction is proposed. The method uses the assumption that the temperature distribution is formed by a local heat source and is based on the selection of the parameters of such a source by the minimization of the residual of the measured and hypothetical values of the acoustic brightness temperature. The accuracy of the determination of the maximal in-depth temperature by different methods is analyzed by numerical simulation. It is demonstrated that the proposed method provides a higher accuracy than Tikhonov’s methods of global and local regularization, especially with a heat source at great depth. The proposed method is shown to cause no systematic error in the reconstruction of temperature peaks at great depth. The possibility of reconstructing a two-peak temperature distribution by the proposed method is demonstrated. 相似文献