International Journal of Applied Electromagnetics and Mechanics - Volume 52, issue 1-2

Article Type: Other

DOI: 10.3233/JAE-162232

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 1-2, 2016

Authors: Banks, H.T. | Catenacci, Jared | Criner, Amanda

Article Type: Research Article

Abstract: Reflectance spectroscopy obtained from thermally treated silicon nitride carbon based ceramic matrix composites is used to quantity the oxidation products SiO_2 and SiN. The data collection is described in detail in order to point out the potential biasing present in the data processing. A probability distribution is imposed on selected model parameters, and then non-parametrically estimated. A non-parametric estimation is chosen since the exact composition of the material is unknown due to the inherent heterogeneity of ceramic composites. The probability distribution is estimated using the Prohorov metric framework in which the infinite dimensional optimization is reduced …to a finite dimensional optimization using an approximating space composed of linear splines. A weighted least squares estimation is carried out, and uncertainty quantification is performed on the model parameters, including a piecewise asymptotic confidence band for the estimated probability density. Our estimation results indicate a distinguishable increase in the SiO_2 present in the samples which were heat treated for 100 hours compared to those treated for 10 hours. Show more

Keywords: Ceramic matrix composites, prohorov metric, reflectance spectroscopy, uncertainty quantification

DOI: 10.3233/JAE-162168

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 3-24, 2016

Authors: Qiu, Jinhao | Cheng, Jun | Zhang, Chao | Ji, Hongli | Takagi, Toshiyuki | Uchimoto, Tetsuya

Article Type: Research Article

Abstract: In this article, two novel NDT methods for composite structures are presented. First, the laser ultrasonic method for visualization of impact damage is introduced. A laser ultrasonic scanning system was developed, and the anomalous incident wave (AIW) energy was obtained from the wave-field data to image the artificial and impact damages. Next, a mid-frequency ECT (eddy current testing) system with the working frequency up to 250 kHz developed by the authors' lab for CFRP inspection is presented. The main features of the system include the weak-signal extraction method using the lock-in amplifier and the C-scan imaging techniques. The location and …size of different damages were visualized in the scan image. With the developed system, the direction of different fiber plies could also be successfully detected. Show more

Keywords: Composite materials, nondestructive testing, laser ultrasonic method, eddy current testing

DOI: 10.3233/JAE-162203

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 25-33, 2016

Authors: Pasadas, Dário | Ribeiro, A. Lopes | Ramos, Helena | Rocha, Tiago

Article Type: Research Article

Abstract: In this paper we present a method to determine the current density inside an aluminum plate using eddy current testing procedure to determine the existence of surface cracks. The general idea consists in generating eddy currents in the plate, which in the case of flawless material, must be of uniform density pointing along a pre-defined direction inside a given area on the plate surface. These currents are produced using a planar coil. The eddy current density is determined by inversion of the data obtained from the measurement of a single component of the resultant magnetic field. Tikhonov regularization is applied …to the inverted data. Show more

Keywords: Eddy current testing, inverse problem, Tikhonov regularization

DOI: 10.3233/JAE-162066

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 35-40, 2016

Authors: Wang, Bin | Da, Yihui | Qian, Zhenghua

Article Type: Research Article

Abstract: The paper proposes an inverse reconstruction method for surface flaws in a 2-D half-space using guided Rayleigh waves. When a guided Rayleigh wave is sent toward the flaw area, the reflected wave signals are observed and recorded at the far field. From wave scattering theory, the displacement field of reflected wave is expressed by an integral over the unknown flaw surface concerning the total wave field. By introduction of Born approximation and far-field expressions of Green's function, it is found that the reflection coefficient in wavenumber domain is related to the unknown shape of the cavity by a spatial Fourier …transform relation. Thus, the location and shape of unknown cavity can be established. Numerical examples are illustrated in the paper. The research can act as a basis for quantitative ultrasonic guided wave non-destructive inspection. Show more

Keywords: Rayleigh wave, flaw reconstruction, scattering theory, inverse problem

DOI: 10.3233/JAE-162172

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 41-48, 2016

Authors: Kojima, Fumio | Banks, H.Thomas

Article Type: Research Article

Abstract: This paper is concerned with material interrogation methods for homogeneous dielectric materials using statistical inversion. Frequency dispersions for homogeneous dielectric materials can be described by a classical Lorentz model. Taking into account that the reflection coefficients are indirectly measurable, the signal response model is given by a complex reflectance at the interface between free space and the dielectric medium. The problem considered here is to quantify uncertainties of the estimated dielectric parameters from the measurements obtained by a reflective interferometer. A computational method using Hamiltonian Monte Carlo sampling based on nonlinear hierarchical models is tested.

Keywords: Inverse problem, nondestructive evaluation, electromagnetic interrogation, polarization

DOI: 10.3233/JAE-162207

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 49-54, 2016

Authors: Honda, Satoshi | Yonekura, Hiromitsu

Article Type: Research Article

Abstract: This paper describes the detection method of the anomalies in signals proposed by Okabe et al. based on their KM_2O-Langevin framework; breakdown points of the stationarity can be detected to give the sign of anomalies. The method was applied to the sound signals to monitor the state of a generator engine and showed its feasibility.

Keywords: Anomaly detection, stationarity test, fluctuation-dissipation principle

DOI: 10.3233/JAE-162102

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 55-60, 2016

Authors: Nara, Takaaki | Takeda, Hirofumi | Ando, Shigeru

Article Type: Research Article

Abstract: In this paper, we propose to use an avalanche beacon with frequency of 457 kHz to search for a rescuer buried in rubble in a secondary earthquake disaster. In an avalanche rescue, a searcher proceeds along the magnetic force lines generated by the victim's beacon, and always reaches the magnetic field `zero point', which is guaranteed to be in the proximity of the victim. In this paper, we show that ferromagnetic objects in rubble do not substantially affect a zero point search by theoretical analyses, numerical simulations, and experiments.

Keywords: Inverse problem, beacon, magnetic dipole, zero point, ferromagnetic objects

DOI: 10.3233/JAE-162194

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 61-66, 2016

Authors: Higuchi, Yusuke | Nara, Takaaki | Ando, Shigeru

Article Type: Research Article

Abstract: It is known that Euler's homogeneity equation provides a system of linear equations for localizing a magnetic dipole from measurements of the magnetic field and its gradients. In this paper, we show that a solution of the equations obtained by Truncated Singular Value Decomposition (TSVD) always gives the true position of the dipole regardless of the singularity of the coefficient matrix. Hence, we can localize a magnetic dipole robustly without estimation bias by TSVD.

Keywords: Inverse problem, magnetic dipole, Euler's equation

DOI: 10.3233/JAE-162202

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 67-72, 2016

Authors: Okawa, Shinpei | Nara, Takaaki

Article Type: Research Article

Abstract: A method to reconstruct the current dipoles in human brain for magnetoencephalography was examined. In the method, a spatial filter provided the initial guess of the current dipole distribution. Then the current dipoles were localized by minimized the entropy calculated with the current dipole distribution. The reconstructed dipole moments were corrected in a post processing. In the numerical simulations the proposed method was compared with the focal underdetermined system solver (FOCUSS) which reconstructed a sparse distribution of the current dipoles. The proposed method was able to reconstruct the current dipoles more robustly than FOCUSS from the measured magnetic fluxes with …low signal-to-noise ratio. Show more

Keywords: Inverse problem, magnetoencephalography, biomedical engineering

DOI: 10.3233/JAE-162192

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 73-78, 2016