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LiNbO₃: MgO 결정에서 광굴절 격자의 회절 특성
이재철(Jaichul Yi),장지웅(Chi-Ung Chang),김준태(Juntae Kim),신승호(Seung-Ho Shin) 한국광학회 1999 한국광학회지 Vol.10 No.5
4% 몰의 MgO가 도핑된 광굴절 LiNbO₃결정에 기록된 광굴절 격자의 회절 효율과 응답시간을 측정하였다. 이 실험에는 고출력 펄스 Nd:YAG 레이저(Q-switch mode, λ=532 ㎚)와 연속 발진 아르곤 이온 레이저(λ=514.5 ㎚)가 사용되었다. 두 종류의 레이저 광속에 대한 실험에서 광학계의 배열을 동일하게 하고 2광파 혼합 조건에서 레이저 광속의 세기를 1.6~100W/㎠까지 변화시켜가며 최대 회절 효율과 기록 및 소거시의 응답시간을 측정하였다. 두 실험에서 얻은 결과를 비교하고 분석하였다. We present the measurement of the diffraction efficiency and response time of the photorefractive grating recorded in LiNbO₃photorefractive crystal doped with 4%-mole MgO. Two laser sources were used in the experiments; frequency-doubled Q-switched Nd:YAG laser (λ=532 ㎚) and cw Ar-ion laser (λ=514.5 ㎚). The same optical geometry was also used in both experiments in order to maintain the experimental consistency. Using the two-wave mixing scheme in both experiments we measured the maximum diffraction efficiency in the range of beam intensity of 1.6~100 W/㎠, and the response times for both cases of recording and erasing. Two sets of results obtained from the experiments are compared and analyzed.
Deflection behaviors of polymer mortar sandwich panels reinforced with GFRP
Yeon, Kyu-Seok,Yi, Jaichul,Lee, Hyun-Jong Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of applied polymer science Vol.108 No.2
<P>This study prepared sandwich panel specimens composed of methyl methacrylate (MMA)-modified polymer mortar at the core and reinforced with high-tensile GFRP on both faces to propose a method to predict the deflection of polymer mortar sandwich panels under flexural load. Nine experimental specimens of different thickness at the core and face were prepared for the flexural load test to determine the moment-deflection relationship, and the experimental results were compared with existing theoretical models. The comparison study revealed that the deflection behavior of the specimens in response to the variation in the thickness of the specimens at the core and face could be well predicted. Additionally, an analytical model, which revised a bilinear method, to explain the tension stiffening effect of the prepared sandwich panel specimens under the influence of flexural load is proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008</P>
이영호,이재철,이승우,서장일,박세희 강원대학교 부설 석재복합신소재 제품연구센터 2003 석재연 논문집 Vol.8 No.-
폴리머 콘크리트를 이용하여 호안블럭을 디자인하고 제작하였다. 제품의 표준화를 위하여 '폴리머 복합체를 이용한 호안블럭 제조용 시방서'를 작성하였다. 폴리머 콘크리트의 우수한 물리적 성질을 이용하고 환경 친화적인 호안블럭을 제작하기 위하여 중앙에 원형 홀이 있는 I형, 원형, 반원형 호안블럭을 디자인하였다. 중앙의 홀은 바닥재로 채워질 수 있도록 했으며 인공적인 색상보다는 주위의 환경과 어울리도록 식물을 조경할 수 있도록 하였다. 또한, 시판중인 호안블럭과 호환이 되도록 크기를 결정하였으며 자외선 흡수제를 첨가하여 제작하였다. 시방서에서 제시하는 방법으로 휨강도 및 흡수율을 측정하였다. Polymer concrete was used to produce the stone block. In order to make the blocks standardize, 'Specifications for Producing Stone Block using Polymer Concrete' was suggested I-type, circular type and semi-circular type of stone blocks were designed and produced, in which a circular hole was made to utilize the excellent physical properties of the polymer concrete and to produce the eco-friendly stone block. Instead of using artificial color, the hole was designed to be filled with the ground soil and then grass can be planted to make the blocks harmonize with surroundings. The dimensions of blocks were determined to fit the cement concrete block on the market and the ultra violet absorber was added in producing the blocks. Flexural strengths and absorption of the polymer concrete blocks were measured by the method regulated in the specification.
Soon-Kwon Nam,Jaichul Yi 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.6
The Hamiltonian formalism of the dynamics of a single electron transversing a drift tube under the combined in uence of a linear magnetic wiggler and an axial magnetic guide eld is used to study the behaviors of the eective potential wherein the particle propagates while satisfying the combined resonance condition. A canonical transformation is used to derive the energy conservation theorem, in which the eective potential is expressed as a function of the departure of the axial momentum from the resonant value. The eective potential is analyzed for various cases of resonance states. We conclude that a limit exists on the strength of the wiggler eld (or axial eld) above which the propagation of the beam is hampered because no resonance state exists. We also conclude that the drift tube has a limit on its size above which the resonance states vanish.
The nonlinear interaction between two resonant waves in a waveguide free - electron laser
Soon-Kwon Nam,Jaichul Yi,Ki-Bum Kim 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.4
We extend numerical analysis investigating the waveguide parameter dependency of the two resonant frequencies at the small-signal gain regime in a waveguide free-electron laser to the case that there exists a nonlinear coupling. The properties of the nonlinear interaction between the two resonant waves, one with higher frequency and positive slippage and the another one with lower frequency and negative slippage, are numerically investigated in the high gain regime. The results of numerical work with a set of partial differential equations describing the space and time interaction of the two resonant waves are analyzed.
Stability of Transverse Soliton in a Free-Electron Laser
Soon-Kwon Nam,Jaichul Yi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.6
The stability of the transverse mode of a soliton in a free-electron laser is studied by surveying its time evolution. The nonlinear Schr¨odinger equation is discretized, and a numerical simulation is carried out along the time propagation axis to survey the stability of the soliton-like solution. A numerical simulation shows that the ratio between the Rayleigh length and the gain length plays a key role in determining the stability properties of the transverse soliton-like solution. Depending on magnitude of the ratio, the soliton can propagate by increasing its magnitude or cannot propagate and breaks.
백승호,김재철,박건태,Baek, Suengho,Kim, Jaichul,Park, Geontai 항공우주시스템공학회 2007 항공우주시스템공학회지 Vol.1 No.3
The objective of this study is to investigate endurance test of localization part for T-50 aircraft engine. Major localization parts of the engine (F404-STW-102) was performed using Accelerated Simulated Mission Engine Test. The purpose of this test is to evaluate of quality demonstration capability, to verify design of engine localization parts, and to improvement safety and operation rate of T-50 advanced trainer by finding out operational problems in production phase and fixing it.