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VTE 처리된 강유전 LiNbO₃ 단결정 내의 Nd³+와 Er³+ 초미세 구조의 비등방성
박일우(I.-W. Park),조성호(S. H. Choh),김영미(Y. M. Kim),전웅(U. Chon),김상수(S. S. Kim),김원정(W. J. Kim),김봉구(B. G. Kim),손재민(J. M. Sohn) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.2
We have obtained sharp and clearly resolved ESR spectra of Nd³+ and Er³+ in vapor transport equilibrium (VTE) treated LiNbO₃ crystals, consequently have determined more accurate spin Hamiltonian parameters, than those in congruent samples. The anisotropic hyperfine structures of ¹⁴³Nd³+ and (145)^Nd³+ in the VTE-treated crystals at liquid helium temperature have been analyzed. It is proposed that both rare earth ions favor the lithium site in LiNbO₃ from the consideration of the determined anisotropic g-values.
FE Simulation 을 이용한 BIS 백 프레임 모듈의 경량화 방안
김봉구(B. G. Kim),신동석(D. S. Shin),오희택(H. T. Oh),전의식(E. S. Jeon) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
자동차 산업에서의 고강도-경량화 기술 연구에서 안전 규정의 강화, 환경 규제의 강화, 편의 기술의 발전에 필수적으로 필요하다. 자동차 시트는 고강도-경량화 조건을 만족시켜야 하는 대표적인 내장 부품이며 미래형 자율주행차, 전기차, 수소차 등의 다양한 조건을 만족시키기 위하여 고강도-경량 소재만을 활용하거나, BIS (Belt in Seat) 프레임과 같이 구조를 변경하는 연구 사례가 수행되어 왔다. 하지만 고강도-경량 소재는 가공이 어려운 문제가 있고, BIS와 같은 구조에 적용 시 각 부품의 두께 및 이중 소재를 선택해야 하는 경우가 발생하므로, FE Simulation 을 활용하여 시행착오를 최소화하는 방안들이 시도되고 있다. 본 논문에서는 BIS 프레임 구조에 대한 초고강도 및 경량화 조건을 만족시키기 위하여, BIS 프레임 모델에 대한 FE Simulation 을 활용하고 그 결과를 제시했다. BIS 프레임에 대한 유한요소 모델링을 수행했고, 물성 시험 데이터와 두께 정보를 박판 부품들에 적용했다. 안전성을 확인하기 위해 FMVSS 207 및 FMVSS 210 규정에 대한 시험을 모사하고, 그 결과를 분석했다. 고강도-경량화 조건을 만족시키기 위하여 인자 이산화를 수행했고, 인자 배치에 따른 유한요소해석을 수행하여 BIS 백 프레임 모듈의 소재와 두께 선정 과정을 제시했다. 이러한 연구 과정은 BIS 프레임의 개념설계 단계에서 활용될 것으로 기대한다.
화학당량에 따른 우라니아의 핵분열 기체 확산 계수 측정
김희문(H. Kim),박광헌(K. Park),김봉구(B. G. Kim),주용선(Y. S. Choo),김건식(K. S. Kim),송근우(K.W. Song),홍권표(K. P. Hong),강영환(Y. H. Kang) 한국표면공학회 2002 한국표면공학회지 Vol.36 No.1
The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimens were made from a UO₂ single crystal powder with natural enrichment. Weight and grain size were 300mg and 23(㎛, respectively. Oxygen potentials were obtained from an oxygen sensor. Released fractions were obtained from both results of gamma scans and quantitative analysis with MCNP code, The annealing test was performed at three temperatures at once. Diffusion coefficients of Xe-133 were calculated using slope of Booth theory in each O/M ratios. Activation energy and the pre-exponential factor of the diffusion coefficient were obtained. The activation energy of near stoichiomeric UO₂ is 310 kJ/mol. The measured values of near stoichiometric UO₂ are very close to other data available. Diffusion coefficients increase with hyper-stoichiometry, due to higher concentration of cation vacancies.
벨로우즈를 이용한 반복 하중부과장치의 개발 및 성능시험
최명환(M.H. Choi),조만순(M.S. Cho),김봉구(B.G. Kim),김학노(H.R. Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
A fatigue capsule is one of the special capsules to investigate the fatigue characteristics of the nuclear materials in a research reactor, HANARO. In this study, the performance test and the preliminary fatigue test results by using a cyclic load device newly developed for a fatigue capsule are described. In order to obtain the characteristics such as a realization and a controllability of the periodic wave shape and the relation between the pressure and the load, a spring and rigid bar specimens are used. The fatigue test for the STS 316L specimen with 1.8㎜ in diameter and 12.5㎜ in gage length is also performed under the same conditions as the temperature(550℃) of the specimen during irradiation tests. As a result of the test, the fracture of the specimen occurs at a total of 127,865 cycles (22 days), and the displacement is 2.63㎜. It is expected that these results will be used for a determination of test conditions and a comparison of the in-pile fatigue test results.
최명환(Choi, M.H.),주기남(Choo, K.N.),조만순(Cho, M.S.),김봉구(Kim, B.G.) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.12
The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change of the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural integrity of the material capsule called 04M-17U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19.6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's in-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.