• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.146-147
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• 2000

The electromagnetic wave scattering from active objects has only recently attracted attention.$^{(1).(3)}$ Theoretical studies have considered normal-incidence plane-wave interactions with active dielectric cylinders with the prediction of large enhancements in the scattered field for bound mode structures. According to the theory of the electromagnetic wave scattering from a dielectric cylinder, the eigenvector solutions are discrete and have both guided (non-radiative) and leaky (radiative) mode solutions. By using an anti-guiding (leaky) structure instead of a guided structure and scattering at oblique incident angles near critical angle, the scattering resonances predicted by theoretical studies were obtained for the first time. A fine-grained scan of the plane-wave incident angle a reveals the existence of discrete scattering resonances. The diameter and real part of the index of refraction determine the resonant conditions and the imaginary part of the refractive index has a threshold value to make mode up for its radiation loss. The cross coupling between transverse electric (TE) and transverse magnetic (TM) modes is clearly detected for both active and passive scattering as theoretically expected. (omitted)

• 한국음향학회지
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• 제33권5호
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• pp.282-290
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• 2014

매끈한 물체에 의한 음향산란에 관한 수치해석은 발전해 왔으나 경계면에 위로 부분적으로 드러나 있는 물체에 의한 음향산란에 대한 수치해석은 여전히 드물다. 해저면에 부분적으로 파묻힌 실린더의 후방산란진폭을 결정함에 있어 경계면에 의한 잔향은 표적의 산란 함수 특성을 변화시킨다. 본 연구는 평탄한 경계면에 부분적으로 파묻힌 실린더의 후방산란진폭에 대한 수치해석을 제시하기 위하여 모멘트법(Method of Moments)을 채택하였다. 제시된 수치해석은 측정 및 키르히호프 근사법으로 얻은 해석적인 해와 상당한 일치를 보여주었다. 본 연구에서 기술된 수치해석은 해저면에서의 잔향과 표적으로부터의 산란파를 결합시킴으로써 해저면에 부분적으로 파묻힌 어떠한 형상의 표적에 대한 후방산란 문제에도 적용될 수 있다.

• 소음진동
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• 제8권6호
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• pp.1172-1180
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• 1998

음향학적으로 강성인 물체와 연성인 물체로부터의 탄성파의 산란과 음향파의 산란을 수치적으로 해석하고 그 특성들을 비교하였다. 부분파들과. 또한 부분파들의 합인 전체 산란파의 위상 및 크기의 거동을 수치적으로 분석하고 토의하였다. 탄성파의 산란시 발생하는 종파와 횡파 사이의 모드변환 현상이 산란파의 크기와 위상에 주는 영향을 밝혔다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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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.

• 천문학회지
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• 제53권6호
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• pp.169-179
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• 2020

Emission features formed through Raman scattering with atomic hydrogen provide unique and crucial information to probe the distribution and kinematics of a thick neutral region illuminated by a strong far-ultraviolet radiation source. We introduce a new 3-dimensional Monte-Carlo code in order to describe the radiative transfer of line photons that are subject to Raman and Rayleigh scattering with atomic hydrogen. In our Sejong Radiative Transfer through Raman and Rayleigh Scattering (STaRS) code, the position, direction, wavelength, and polarization of each photon is traced until escape. The thick neutral scattering region is divided into multiple cells with each cell being characterized by its velocity and density, which ensures flexibility of the code in analyzing Raman-scattered features formed in a neutral region with complicated kinematics and density distribution. To test the code, we revisit the formation of Balmer wings through Raman scattering of the far-UV continuum near Lyβ and Lyγ in a static neutral region. An additional check is made to investigate Raman scattering of O vi in an expanding neutral medium. We find a good agreement of our results with previous works, demonstrating the capability of dealing with radiative transfer modeling that can be applied to spectropolarimetric imaging observations of various objects including symbiotic stars, young planetary nebulae, and active galactic nuclei.

• 대한전자공학회논문지
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• 제25권3호
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• pp.243-251
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• 1988

A new technique to reconstruct complex permittivity profiles of dielectric objects by using the moment-method solutions to the electric field integral equation iversely is presented here. Performing numerical calcualtions for several type of dielectric objects by employing the present scheme, it is demonstrated that this inverse technique provides the superresolution of the reconstructed permittivity profiles regardless of the location measured the scattered field, the size and shape of dielelctric objects and the permittivity profile.

• 한국전자파학회논문지
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• 제13권9호
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• pp.937-946
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• 2002

본 논문에서는 도체로부터의 안정된 전자기 산란 응답을 계산하는 새로운 해법을 제안한다. 이 방법은 기존의 MOT (marching-on in time) 기법을 이용하지 않고, 가중 라게르 (Laguerre) 다항식으로 유기전류의 과도 응답을 표현하여 시간 영역의 적분방정식을 푼다. 이 시간 영역의 기저함수를 사용함으로써 적분식의 미분항을 해석적으로 처리하여 과도 응답을 구할 수 있다. 또한 적용되는 이 기저함수는 시간이 진행함에 따라 영으로 수렴하는 특성 때문에, 유기전류의 과도응답도 후기 진동을 가지지 않고 영으로 수렴한다. 제안되는 방법의 타당성을 보이기 위하여 시간 영역 전장 적분방정식의 해를 MOT 및 해석해와 주파수 영역으로부터 구한 해의 이산 푸리에 역변환 (inverse discrete Fourier transform, IDFT)과도 비교한다.

• 한국군사과학기술학회지
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• 제23권4호
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• pp.328-336
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• 2020

This paper presents an asymptotic analysis method using the PO(physical optics) approximation technique to analyze the scattering contribution of an electrically large object partially coated with a radar absorbing material(RAM). By using the feature of the PO technique that can calculate the equivalent current value for each mesh independently, instead of analyzing the entire structure, scattering analysis was performed only by calculating the current on the area where the RAM coating is applied. By the numerical examples, the accuracy and the computation time of the proposed method were verified, and the computational efficiency of inverse synthetic aperture radar(ISAR) of the electrically large objects that require enormous resources is improved.

• 한국통신학회논문지
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• 제21권5호
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• pp.1317-1324
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• 1996

An angular spectral inverse technique, applying the moment method procedure with a series expansion for the induced field in each enlarged cell, is suggested to reconstruct permittivity profiles of inhomogeneous dielectric objects and to reduce the ill-posedness inherent to inverse scattering problems. The angular spectral inverse scattering using the pulse basis function in enlarging the scatterer has the ill-posedness due to the input data of higher spectra. To reduce the number of higher spectra, enlarging the cell size and averaging over the cell with a suitable weighting function are found to play improtant roles for the reduction of ill-posedness of the angular spectral inverse scattering problems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.82-85
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• 2003

In this paper, we present the analysis of electromagnetic scattering from arbitrarily shaped three-dimensional conducting objects coated with a dielectric material. The integral equation treated here is the combined field integral equation. Numerical results of radar cross section for coated conducting structure are presented and compared with other available solutions.