평행판 도파관내의 산란 도체에 의한 산란파 해석

정봉식,김현정,김응수,조규완 대한전자공학회 1995 전자공학회논문지-A Vol.32 No.12

In this paper, new algorithm which calculates transmission coefficient of electromagnetic wave by numerical analysis of scattered field by conductors with arbitrary cross-sections in parallel-plate waveguide is proposed. Proposed algorithm assumes magnetic current distribution on the boundary of scattering conductors, and applies Image theorem to perfect conductor surfaces of parallel-plate waveguide. Integral equations for fictitious magnetic currents on conducting boundary are set up. Magnetic current distributions on conducting boundary are expanded as exponential basis function, and using Galerkin method matrix equations are set wp. To compute matrix elements this method utilizes Fourier transform which is faster than numerical integration. Finally, frequency and incidence-angle characteristic of transmission coefficient are calculated and compared with experimental results.

트맆토판펩타이드와 인돌유도체의 광분해에 관한 자외선 Action 스펙트라에 미치는 용매효과

정봉식 全北大學校 學徒護國團 1983 全國大學生學術硏究發表論文集 Vol.8 No.-

N-AcetylPhenyl alanyl-L-Tryptophan(NAPT)과 3-Methyl Indole(Seatale)의 광분해에 관한 Action 스펙트라를 수용액 및 유기용매 조건에서 측정하고 분석하였으며 이들 자료로 부터 광분해 양자수율(Photolysis Quantum yield)를 계산하였다. 수용액에 녹은 0.1mM의 NAPT 광분해 Action 스펙트라를 측정 하기위해 얻은 조사(Irrodiation)파장별로 측정된 광조도 효과곡선들(Fluence Effect Curves)이 서로 유사한 점으로 미루어 NAPT의 광분해 메타니즘이 전파장에 대하여 일정하다는 사실이 예상 되었는데 260∼310 nm영역 에서는 일정한 광분해 양자수율을 나타내다가 250nm 보다 짧은 파장영역 에서는 양자수율이 급격히 증가한다. 이러한 현상은 이미 밝혀진 광이온화효율에 미치는 조사파장의 효과와 일치하므로 예상되는 광분해 메카니즘은 이온화과정으로 추정된다. 한편 광이온화에 의하여 생성된 N-Formyl Kynurenine(NFK), 유형의 화합물에 의해 제 2 광화학반응(광증감작용)에 대한 증거는 관측되지 않았다. 반면에 에탄올에 녹은 NAPT와 에타올 또는 시클로핵산에 녹은 Scatole의 광분해 Action 스펙트람들은 NFK 유도체의 흡수스텍트람과 유사한점과 기대이상의 높은 광분해 양자수율로 부터 NFK 유도체에 의한 광증감작용과 같은 제 2의 광화학 반응이 광분해 지배적인 역할을 한다고 추정된다.

유한요소법과 흡수경계조건을 이용한 산란파 해석

정봉식 동아대학교 공과대학부설 생산기술연구소 1998 生産技術硏究所硏究論文集 Vol.3 No.1

The finite element method with absorbing boundary condition for open boundary problems like as 2-dimensional infinitely long inhomogeneous circular or rectangular dielectric scatterer is presented. High order boundary condition (absorbing boundary condition), which is able to put on an approximate extenal boundary near the scatterer, are used to reduce number of unknown and computation time. Homogeneous circular scatterer of the radius of 0.3λ and homogenous rectangular scatterer of 1.0λ×1.0λ in the free space are considered. The relative permittivity of homogenous scatterer is 2.0. The relative permittitivities of an inhomogenous rectangular scatterer are 2.0 in the cross-section of 1.0λ×1.0λ and 4.0 in 0.5λ×0.5λ. The accuracy of scattered fields is investigated as the element size and the radius of approximate extenal boundary are decreased. Numerical results calculated by a quadratic(2nd order) basis function compared with by a linear (1st order) one are well agreed with an analytic solution.

대칭꼴의 pole tip을 boundary integral method를 이용하여 임의의 위치에서의 자장을 구하는 방법 ( Field computation of the magnetic pole tip using boundary element method )

정봉식,안창회,이수영,나정웅 대한전자공학회 1989 대한전자공학회 학술대회 Vol.1989 No.7

동축선로내 대역억제필터의 최적화

정봉식 한국정보통신학회 2000 한국정보통신학회논문지 Vol.4 No.1

본 논문에서는 고주파 발생기로부터 발생되는 원하지 않는 고조파 성분을 차단하기 위해 동축선로형 출력단의 내부에 대역억제필터를 삽입하고, 이필터를 등가회로 개념으로 해석하고 최적화하고자 한다. 동축선로 내부에 삽입되는 대역억제필터는 $\fraction ane-quarters\lambda$초크구조로서, 초크의 길이는 고조파 성분에 해당하는 파장의 $\fraction ane-quarters$로 초기화한다. 이때 초크구조의 불연속 경계에서 나타나는 가장자리효과는 초크의 길이를 등가적으로 증가시켜 차단주파수를 감소시키므로 고조파 성분의 정확한 차단을 어렵게 한다. 여기서는 가장자리 효과를 보상하기 위해 최적화 알고리즘(LMA)을 이용하여 대역억제필터를 최적화하고자 한다. In this paper band-stop filters that reject the undesired 3th and/or 5th harmonics generated from high frequency generator are analyzed using equivalent circuit concept, and optimized using iterative optimization algorithm. The length of the band-stop filter is setup initially a quarter of a wavelength of the harmonic, but initial filter structure is exactly unable to cutoff the harmonics because of the fringing effect at the discontinuous boundary. To reduce the mismatch between the cutoff frequency and the harmonics, iterative LMA(Levenberg-Marquardt Algorithm) is introduced and band-stop filters in coaxial line are optimized.

요한요소법과 LMA-GA 혼합법을 이용한 거대 강산란체의 역산란

정봉식 동아대학교 공과대학부설 생산기술연구소 1998 生産技術硏究所硏究論文集 Vol.3 No.2

An iterative inverse scattering method(IISM) for reconstructing the permittivity of two dimensional high contrast and large object is presented. This method uses the finite element method(FEM) for calculating the scattering fields and the hybrid method for minimizing the cost function. The FEM calculates the scattered fields faster than the method of moment(MM). The hybrid method(HLMGA) is composed of a Levenberg-Marquardt algorithm(LMA) and a genetic algorithm(GA). Numerical results show that the IISM based on the HLMGA and GA can always reconstruct all the permittivity profiles of a high contrast and large object, in contrast the IISM based on the LMA often converges to the local minima of the cost function. The HLMGA gives better permittivity profiles and faster convergence than the GA. When the noise is presented in the scattering fields, the characteristics of the cost function show that multiple incident waves are needed for the stable inversion. Also both LMA and a prior knowledge of background medium for a fast convergence are used. The permittivity profile converged to local minima by LMA is modified by substituting the background profile into a known background medium, then this modified profile as an initial one in order to get out of a local minima of cost function is used.

企業合倂에 있어서 問題點

정봉식 成均館大學校 經商大學 1971 經商論集 Vol.22 No.1

유한요소법에 의한 도파관 급전 캐비티의 전자계해석

정봉식,안창회 嶺南大學校 工業技術硏究所 1994 工業技術硏究所論文集 Vol.22 No.2

Electromagnetic fields of the rectangular waveguide-loaded cavity are calculated using finite element method. Magnetic field vectors are used as vector variables with edge basis functions. The cavity analyzed in this paper is loaded by the rectangular waveguide only ?? mode excited. Also complex reflection coefficients are obtained.

5G 단말기용 이중대역 평면 다이폴-스트립 배열 안테나 설계

정봉식(Bongsik Jeong) 한국정보기술학회 2022 한국정보기술학회논문지 Vol.20 No.2

In this paper, a dual-band 4x1 dipole-strip array antenna operated at 28㎓ and 39㎓ is designed to be applied to antenna-in-package(AiP). The dipole antenna is fed by a microstrip line and the strip is fed by a coupling with the dipole. Two poles of the dipole antenna are arranged separately on both sides of the substrate to utilize the line feed; one pole is on the ground plane, and the other pole is located on the other side of the substrate. As the phase difference between the neighboring ports of the array antenna changes, the gain and beam steering angle of the array antenna change. When the phase difference is changed to 0~135˚, the gain at 28㎓ and 39㎓ changes to 8.9~8.2㏈ and 10.2~9.4㏈, respectively, and the beam steering angle changes to 0~39˚ and 0~30˚, respectively. The designed array antenna has a thin thickness of 24.5㎜×3.34㎜×0.324㎜ in size and –10㏈ bandwidth of 26.6~29.7㎓ and 37.6~40.3㎓ in both bands, which has a bandwidth of about 3㎓.

동축선로형 λ/4초크 대역억제필터의 최적화

정봉식,이규한,김진길 東亞大學校 附設 情報通信硏究所 1999 情報通信硏究所論文誌 Vol.7 No.1

In this paper the band-stop filter that rejects the undesired 3th and 5th harmonics generated from high frequench generator is analyzed and optimized. The length of the band-stop filter is setup initially a quarter of a wavelength fo the harmonic, but initial filter structure is unable to cutoff the harmonics because of the fringing effect at the input of the choke. To reduce the mismatch between the cutoff frequency and the harmonics, the length of the choke is optimized by using iterative Levenberg-Marquardt Algorithm.