• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1083-1086
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• 2005

Light scattering measurement system that can evaluate light scattering characteristic from defects on silicon wafer surface has been developed. The system uses $Ar^+$ laser as an illumination source, and a highly sensitive photomultiplier tube (PMT) for detecting scattered light from defects. Unlike with conventional measurement system, our system has ability to measure scattered light pattern from wide range of scattering angles with changeable incidence condition. It is shown that our developed system is effective to discriminate the types and sizes of defects from basic experimental results using a microscatch and a PSL sphere.

• 전자공학회논문지A
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• 제32A권7호
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• pp.23-29
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• 1995

A characteristic mode theory for longitudinal slot of arbitrary width in the outer conductor of coaxial waveguide is applied for calculating the characteristic magnetic currents, the characteristic fields, radiation patterns, and the fields evershere(inside and outside the guide, and in the aperture region). Numerical results of the equivalent magnetic currents and the radiation patterns are compared with those obtained by use of the method of moments.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2003년도 춘계학술대회논문집
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• pp.15-18
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• 2003

전자파 산란해석 방법으로서 유한요소법, 경계요소법 및 모멘트법 등은 임의 구조를 한 산란체의 산란현상을 다룰 수 있다. 그러나 이러한 해석방법들은 정상 파동문제를 다루는데 편중되어 있어 시간영역에서의 비정상 파동문제를 해석하기 위해서는 여러 가지 제약이 따른다. 본 논문에서는 본질적으로 시간영역 해석방법인 TLM(Transmission Line Matrix)법을 이용하여 프레넬 렌즈의 산란특성을 해석하고 키르호프의 근사식과 PO(Physical Optics)법과 비교 검토하여 그 유효성을 검증한다.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.41-47
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• 2007

Scattering fields of two dimensional acoustic waves by a circular cylinder are investigated. The present numerical approach for the acoustic scattering problem has difficulties of numerical robustness, long-time stability and suitability of far-field boundary treatments. The time-dependent periodic acoustic source is used to analyze Interference patterns between incident waves and waves reflected by the cylinder. Characteristic boundary algorithms coupled with 4th order Modified-Flux-Approach ENO(essentially non-oscillatory) schemes are employed in generalized coordinates to examine the effect of the wane frequency on the interference patterns. Non-reflecting boundary conditions, which is crustal for accurate computations of aeroacoustic problems, are used not to contaminate scattering fields by reflected waves at the outer boundary. Computed scattering fields show the circumferential acoustic modes generated by interacting between acoustic sources and scattered waves. At a lower frequency, the wave passes almost straight through the cylinder without Interacting with circular cylinder. Simulation results are presented and compared with the analytic solution. Computed RMS-pressure distribution on the cylinder wall is good agreement with exact solution.

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.65-69
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• 2010

High energy electron beams were to concentrically dose inside a tumor and more energy is a shape decreased of dose. Therefore, it is useful to radiation therapy of a tumor. Also high energy electron beams ionized into collision with a atom in structure material of tissue and it has big changes to dose distribution by multiple scattering. The study had to establish characteristic of electron beams from interaction of electron beams and materials. Experiment method was to measure dependence of electron beam central axis for depth dose curve, field flatness and symmetry and field size dependence. The results were able to evaluate data for a datum pint of electron beam. Also radiotherapy has to be considered for not only energy pencil of lines but characteristic, electron guide and isodose curves distribution.

• 한국전자파학회논문지
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• 제8권6호
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• pp.629-635
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• 1997

주기적인 축방향 슬롯이 있는 동축선로 도파관 구조에 TE 편파가 입사될 때 특성모드 이론(characteristic mode theory)을 사용하여 가중 고유방정식(weighted eigenvalue equation)을 유도하고, 일반적인 수치방볍 으로 특성값(characteristic values)과 특성전류(characteristic currents)를 구하여 미지의 등가 자기전류, 산 란패턴과 RCS(radar cross section)를 구하였다. 그리고 이 수치 결과들을 모멘트법을 이용하여 구한 결과들과 각각 비교하여 특성모드에 의한 해석방볍의 타당성을 보였다.

• 대한기계학회논문집A
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• 제23권11호
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• pp.1878-1885
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• 1999

Ultrasonic technique which is one of the most common nondestructive evaluation techniques has been applied to evaluate the integrity of structures by analyzing the characteristic of scattering sign al from internal defects. Therefore, a numerical analysis of ultrasonic scattering field due to defect profiles is absolutely needed for the accurate, quantitative estimation of internal defects. In this paper, the SH-wave scattering by multi-cavity defects and inclusion using Elastodynamic Boundary Element Method is studied. The effects of shape and distance of defects on transmitted and reflected fields are considered. The interaction of multi-cavity defects in SH-wave scattering is also investigated. Numerical calculations by the BEM have been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results can be used to improve the detection sensitivity and pursue quantitative nondestructive evaluation for inverse problem.

• Nuclear Engineering and Technology
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• 제45권4호
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• pp.529-538
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• 2013

Scattered photons cause blurring and distortions in flash radiography, reducing the accuracy of image reconstruction significantly. The effect of the scattered photons is taken into account and an iterative deduction of the scattered photons is proposed to amend the scattering effect for image restoration. In order to deduct the scattering contribution, the flux of scattered photons is estimated as the sum of two components. The single scattered component is calculated accurately together with the uncollided flux along the characteristic ray, while the multiple scattered component is evaluated using correction coefficients pre-obtained from Monte Carlo simulations.The arbitrary geometry pretreatment and ray tracing are carried out based on the customization of AutoCAD. With the above model, an Iterative Procedure for image restORation code, IPOR, is developed. Numerical results demonstrate that the IPOR code is much more accurate than the direct reconstruction solution without scattering correction and it has a very high computational efficiency.

• 한국광학회지
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• 제31권2호
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• pp.59-70
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• 2020

3차원 플래시 라이다 시스템(3D flash LIDAR system)에서의 대기 산란을 해석하기 위해 몬테 카를로 복사 전달(Monte Carlo radiative transfer, MCRT) 방법을 바탕으로 수정된 수치 해석 모델인 MCRT 행렬 방법을 논의한다. MCRT 방법을 바탕으로 라이다 신호의 복사 전달 함수를 행렬 형태로 구성하며, 이는 특성 응답에 해당한다. 근축 근사에 기반하여 본 특성 응답 행렬의 중첩 및 합성곱 연산을 활용함으로써 확장된 전반적인 플래시 라이다의 전산 모사 모델을 개발한다. MCRT 행렬 방법은 기존의 몬테 카를로 기반 방법들에서 과도하게 증가할 수 있는 개별 라이다 신호의 추적을 대폭 경감시킨다. 그 결과 본 방법은 다양한 산란 조건 및 라이다 시스템 구성 환경에서도 그 신호 응답을 빠르게 획득할 수 있는 특징을 지닌다. 본 논문에서는 MCRT 행렬 방법에 기반한 전산 모델을 이용하여 상이한 대기 환경 조건에서 동작하는 3차원 플래시 라이다 시스템을 그 산란 조건, 즉, 그 가시거리에 따른 산란 계수를 달리하며 모사하고, 플래시 라이다 신호의 신호대잡음비의 악화, 신호 오류, 시공간적 확산 및 시간 지연 등 시스템상에서의 산란 효과에 의해 나타나는 다양한 현상을 수치적으로 분석한다. MCRT 행렬 방법은 자율 주행을 위한 플래시 라이다 시스템을 포함해 다양한 라이다 시스템을 분석하는데 매우 효과적으로 사용될 수 있을 것으로 기대된다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.143-148
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• 2005

The objective of this study is to estimate RF signal strength over sea and land surfaces. For this work we calculated scattering by land with DEM(Digital Elevation Model) and sea surface with RMS surface height. and we selected two area inland and sea shore as RX point. And for each area, we get VV-pol and HH-pol characteristic of scattering at 2.2GHz.