• 전기학회논문지P
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• 제63권4호
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• pp.317-321
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• 2014

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. Using quantitative simulations of weakly ionized plasma, we can analyze gas characteristic. In this paper, the electron Ionization and diffusion Coefficients in $CH_4$ has been analysed over the E/N range 0.1~300[Td], at the 300[$^{\circ}K$] by the two term approximation Boltzmann equation method and Monte Carlo Simulation. Boltzmann equation method has also been used to predict swarm parameter using the same cross sections as input. The behavior of electron has been calculated to give swarm parameter for the electron energy distribution function has been analysed in $CH_4$ at E/N=10, 100 for a case of the equilibrium region in the mean energy. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

• 한국인터넷방송통신학회논문지
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• 제20권1호
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• pp.77-82
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• 2020

본 논문에서는 2중 유전체층 사이의 완전도체띠 격자구조에 의한 E-분극 전자파 산란 문제는 전자파 수치해석 방법으로 알려진 FGMM(Fourier-Galerkin moment method)를 이용하여 해석하였다. 경계조건들은 미지의 계수를 구하기 위하여 이용하였고, 도체띠의 해석을 위해 완전도체 경계조건을 적용하였다. 도체띠의 폭과 주기, 2중 유전층 사이의 비유전율과 두께 및 입사각에 대해 정규화된 반사전력과 투과전력을 계산하였다. 전반적으로 2중 유전체 층의 비유전율이 증가할수록 반사전력은 증가하였으며, 상대적으로 투과전력은 감소하였다. 2중 유전체 층의 비유전율이 증가할수록 도체띠에 유도되는 전류밀도는 스트립 중앙에서 증가하였다. 본 논문의 제안된 구조에 대한 수치결과들은 기존 논문의 수치해석 결과들과 비교하여 매우 잘 일치하였다.

• 대한기계학회논문집
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• 제16권12호
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• pp.2328-2339
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• 1992

본 연구에서는 일방향(unidirectional)으로 섬유가 강화된 복합재료를 다루게 되는데, 섬유는 직경이 모두 같고, 길이가 무한이며, 서로 평행하게 정렬되엉 불규칙 하게 분포된 원형실린더로 가정한다. 먼저, 임의의 한 기준 산란체에 의한 압축파 및 SV파의 산란을 수식화하고, 기준 산란체에 대한 나머지 산란체들이 존재할 확률을 이용하여 산란계수의 통계적 기대값을 구함으로써 그 매질내에 존재하는 파동의 전파 특성을 지배하는 분산 관계식의 해를 수치적으로 구함으로써 매질의 평균전파속도, 유 효 동탄성계수 및 감쇠계수를 주파수와 체적비의 함수로 구한다. 또 구하여진 동탄 성계수의 저주파 극한값과 정적하중상태에서 구한 Hashin-Rosen의 값들과 비교하여 봄 으로써 본 연구의 타당성을 입증한다.

• 대기
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• 제22권3호
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• pp.367-379
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• 2012

Measurements of $PM_{10}$ mass concentration, aerosol light scattering and absorption coefficients as well as aerosol size distribution were made to characterize the aerosol physical and optical properties at the two Korean WMO/GAW regional stations, Anmyeondo and Gosan. Episodic cases of the severe Asian dust events occurred in spring of 2009-2010 were studied. Results in this study show that the aerosol size distributions and optical properties at both stations are closely associated with the dust source regions and the transport routes. According to the comparison of the $PM_{10}$ mass concentration at both stations, the aerosol concentrations at Anmyeondo are not always higher than those at Gosan although the distance from the dust source region to Anmyeondo is closer than that of Gosan. The result shows that the aerosol concentrations depend on the transport routes of the dust-containing airmass. The range of mass scattering efficiencies at Anmyeon and Gosan was 0.50~1.45 and $0.62{\sim}1.51m^2g^{-1}$, respectively. The mass scattering efficiencies are comparable to those of the previous studies by Clarke et al. (2004) and Lee (2009). It is noted that anthropogenic fine particles scatter more effectively the sunlight than coarse dust particles. Finally, we found that the aerosol size distribution and optical properties at Anmyeondo and Gosan show somewhat different properties although the samples for the same dust_episodic events are compared.

• ETRI Journal
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• 제21권3호
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• pp.41-48
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• 1999

We have calculated differential reflection coefficient for isolated well structure of micro-scale, etched on dielectric surface. The differential reflection coefficient is computed using Green's second integral theorem. The purpose of our computation is to find a class of well profiles which give maximal diffusive scattering. To have such a maximal effect, we have concluded that the waist radius of Gaussian beam and its wavelength should be comparable to the well width and that well depth has to be larger than a wavelength. Exact calculation of differential reflection coefficients of dielectric surface with isolated structure on it may be used for the examination of dielectric surfaces and also in making simple but efficient diffuser.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.363-366
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• 1998

High frequency scattered fields by a double impedence wedge are computed. In the procedure of the computation, arbitrary impedence faces and wedge angles are considered. The diffraction coefficients for the single, double and triple diffraction mechanism are founded. The second-order and third-order diffracted fields are approximated via the extended spectral ray method and the modified Pauli-Clemmow method of the steepest descent. The maliuzhinets function which is very difficult to obtain accurate value is approximated by the Volakis's asymtotic expression. Numerical computations are performed for the various wedge angles and surface impedence values.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.147-150
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• 1994

To predict light propagation in biological tissues irradiated by laser, the optical properties such as absorption and scattering coefficients are required. There have been various techniques for measuring these coefficients. One method requires tissue samples, often a slab of thin tissue, is invasive. On the other hand, non-invasive method usually measures back-scattered light from a subject with no physical intervent ions. Advantages and disvantages of using different methods are investigated. A careful attention should be made in order to select the best method for a given experimental condition since, even either for invasive or non-invasive method, accuracy is subject to governing models and sample preparations.

• 전자공학회논문지A
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• 제32A권3호
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• pp.38-44
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• 1995

The scattered electric field from a multilayered circular dielectric cylinder is caculated. Approximate boundary condition used in on-surface radiation boundary condition(OSRC) method has been applied to all the boundary surface of N-layered dielectric cylinder. It was assumed that scattered electric field at inner boundary surface in one region transmitted to the adjacent region at outer boundary surface. In the whole region, the unknown coefficients of electric field are acquired by the given incident electric field with ease. Electric field distribution at each boundary surface and the scattered electric field in free space are taken with the calculated unknown coefficients. the results obtainted were compared with those results that were used by regular surface boundary condition.

• 전기학회논문지P
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• 제63권1호
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• pp.19-23
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• 2014

This paper describes the electron transport characteristics in $SF_6$-He gas calculated E/N values 0.1~700[Td] by the Monte Carlo simulation and Boltzmann equation method using a set of electron collision cross sections determined by the authors and the values of electron swarm parameters obtained by TOF method. This study gained the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients for $SF_6$-He gas at a range of E/N. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1017-1031
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• 2009

The problem of interaction of surface water waves by small undulation at the bottom of a laterally unbounded sea is treated on the basis of linear water wave theory for both normal and oblique incidences. Perturbation analysis is employed to obtain the first order corrections to the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Fourier transform method and residue theorem are applied to obtain these coefficients. As an example, a patch of sinusoidal ripples is considered in both the cases as the shape function. The principal conclusion is that the reflection coefficient is oscillatory in the ratio of twice the surface wave number to the wave number of the ripples. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with high reflection of incident wave energy. The theoretical observations are validated computationally.