• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.213-236
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• 2015

The paper presents an investigation into the mode conversion and scattering characteristics of guided waves at delaminations in laminated composite beams. A three-dimensional (3D) finite element (FE) model, which is experimentally verified using data measured by 3D scanning laser vibrometer, is used in the investigation. The study consists of two parts. The first part investigates the excitability of the fundamental anti-symmetric mode ($A_0$) of guided wave in laminated composite beams. It is found that there are some unique phenomena, which do not exist for guided waves in plate structures, make the analysis become more complicated. The phenomena are observed in numerical study using 3D FE simulations. In the second part, several delaminated composite beams are studied numerically to investigate the mode conversion and scattering characteristics of the $A_0$ guided wave at delaminations. Different sizes, locations and through-thickness locations of the delaminations are investigated in detail. The mode conversion and scattering phenomena of guided waves at the delaminations are studied by calculating reflection and transmission coefficients. The results show that the sizes, locations and through-thickness locations of the delaminations have significant effects on the scattering characteristics of guided waves at the delaminations. The results of this research would provide better understanding of guided waves propagation and scattering at the delaminations in the laminated composite beams, and improve the performance of guided wave damage detection methods.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.403-406
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• 1991

Light scattering phenomena are discussed for a nonpolar binary liquid mixture composed of an optically active solute and an optically nonactive solvent in the critical region, using the Fisher theory. Comparing them with those in the case that the Ornstein-Zernike theory is satisfied, the appropriate analytic results are obtained and discussed.

• Journal of the Korean Society of Visualization
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• v.2 no.1
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• pp.52-56
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• 2004

Several visualization techniques of laser diagnostics are presented for combustion phenomena, including Mie scattering for flow, Rayleigh and Raman scattering spectroscopy for major species, laser-induced fluorescence for minor species, and laser-induced incandescence for soot. These techniques have been applied to understand the various combustion phenomena more clearly, including buoyancy-dominant flow system, diffusion flam oscillation, laminar and turbulent lifted flames, flame propagation along a vortex ring, and soot zone characteristics. The usefulness of laser diagnostics on a better understanding of physical mechanism is demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.622-628
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• 1998

The SONAR(SOund NAvigation and Ranging) is the system that detects objects and finds their locations in water by using the echo ranging technique. In this paper, the scattering phenomena for a rigid spherical scatterer will be analyzed using closed form solution, Boundary Element Method and Finite Element Method. Scattering analysis for an elastic spherical scatterer will be analyzed, later. In oder to analyzing the sound wave scattering phenomena for an elastic scatterer in water coupled problem between acoustic and vibration must be considered.

• Laser Solutions
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• v.15 no.4
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• pp.6-11
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• 2012

Laser beam can be either absorbed or scattered in porous ceramic material and its optical characteristics need to be understood. Electro-magnetic multiphysics software was used to simulate and understand the actual scattering phenomena in porous materials. 785nm femtosecond laser was irradiated on the surface of ceramic material and strong scattering occurred in drilling process. The computer results showed the scattering and absorption phenomena of Aluminum oxide were a mixture of dielectric and metallic material. The computer simulation showed the laser beam was almost extinct at the aspect rate of 5 approximately.

• Honam Mathematical Journal
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• v.41 no.2
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• pp.403-420
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• 2019

The Helmholtz equation represents acoustic or electromagnetic scattering phenomena. The Method of Lines are known to have many advantages in simulation of forward and inverse scattering problems due to the usage of angle rays and Bessel functions. However, the method does not account for the jump phenomena on obstacle boundary and the approximation includes many high order Bessel functions. The high order Bessel functions have extreme blow-up or die-out features in resonance region obstacle boundary. Therefore, in particular, when we consider shape reconstruction problems, the method is suffered from severe instabilities due to the logical confliction and the severe singularities of high order Bessel functions. In this paper, two approximation formulas for the Helmholtz equation are introduced. The formulas are new and powerful. The derivation is based on Method of Lines, Huygen's principle, boundary jump relations, Addition Formula, and the orthogonality of the trigonometric functions. The formulas reduce the approximation dimension significantly so that only lower order Bessel functions are required. They overcome the severe instability near the obstacle boundary and reduce the computational time significantly. The convergence is exponential. The formulas adopt the scattering jump phenomena on the boundary, and separate the boundary information from the measured scattered fields. Thus, the sensitivities of the scattered fields caused by the boundary changes can be analyzed easily. Several numerical experiments are performed. The results show the superiority of the proposed formulas in accuracy, efficiency, and stability.

• Journal of Korea Society of Industrial Information Systems
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• v.8 no.2
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• pp.1-6
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• 2003

A theoretical method for the TE polarized electromagnetic scattering on a periodic strip grating over a grounded dielectric slab is considered. The numerical results for an analysis of the plane wave scattering from the structure are presented such as normalized mode amplitude and relative reflected power against normalized dielectric slab height, relative reflected power against angle of incidence and distribution of strip current density. Detailed discussions on the Bragg blazing phenomena observed in the geometry are give.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.31-37
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• 2010

In this paper, optical deflection of laser scattering has been investigated based on Rayleigh criterion for crystalline silicon wafer in solar cell. A laser scattering mechanism is newly designed using light scattering properties in silicon wafer. Intensity distributions of laser scattering are different, depending on the incident angle of laser computed from Rayleigh criterion. In case of the incident angle satisfied with the criterion, they are asymmetric. Also, their specular reflection angle is shifted to unpredicted ones. These phenomena are in accordance with previous theories of laser scattering. The optical deflection of laser scattering is experimentally identified with the designed laser scattering mechanism. Its mathematical model is presented from the geometric relationship of laser scattering. It is shown that the optical deflection of laser scattering agree with the presented model, exclusive of grazing angles which is satisfied with Rayleigh criterion.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.594-606
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• 1999

The electromagnetic scattering characteristics by a periodic strip grating on a grounded dielectric slab for TE polarization case is examined from the viewpoints of both the reflection grating and the leaky wave antenna problems. Numerical results for two kinds of Bragg blazing (resonance type and non-resonance type) phenomena are given and some discussions on the properties such as complex propagation constants, scattering characteristics, and distributions of strip current density are presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1363-1375
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• 2000

The electromagnetic scattering characteristics by a periodic strip grating on a grounded dielectric slab for TM polarization case are examined from the viewpoints of both the reflection grating and the leaky wave antenna problems. Numerical results far two kinds of Bragg blazing (resonance type and non-resonance type) phenomena are given and some discussions on the properties(complex propagation constants, scattering characteristics, and distributions of strip current density) are presented. The comparison of the Bragg blazing phenomena between TM and TE polarization cases are also given in detail.