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수소화 처리된 InAs/GaAs 양자점 적외선 수광소자의 전기적 특성
남형도,송진동,최원준,조운조,이정일,최정우,양해석,Nam H.D.,Song J.D.,Choi W.J.,Cho W.J.,Lee J.I.,Choe J.W.,Yang H.S. 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.2
InGaAs/GaAs 양자 우물 내에 삽입된 InAs 양자점으로 구성된 5층의 흡수층과 $Al_{0.3}Ga_{0.7}As/GaAs$ SL (superlattice) 암전류 장벽층을 갖는 QDIP (quantum dot infrared photodetector) 구조에 대한 수소 RF 플라즈마에 의한 수소화 처리가 QDIP의 전기적. 광학적 특성에 미치는 영향에 대해 연구하였다. RF 플라즈마 수소화 처리는 양자점의 밴드구조에 영향을 미치지 않았으며 $Al_{0.3}Ga_{0.7}As/GaAs$ SL 암전류 장벽층 내의 결함 제거 및 QDIP 구조 내 결함 생성을 동시에 유도함으로써 QDIP의 전기적 특성 향상은 수소 플라즈마 처리시간의 함수임을 알았다. 20 W의 수소 RF 플라즈마를 사용했을 때, 10분간의 플라즈마 조사가 가장 좋은 전기적 특성을 제공하여 높은 암전류 때문에 원시료에서는 측정 할 수 없었던 광전류 신호를 측정 할 수 있었다. In this paper, we investigated the effect of hydrogen-plasma (H-plasma) treatment on the electrical and optical properties of a quantum dot infrared photodetector (QDIP) with a 5-stacked InAs dots in an InGaAs/GaAs well structure and $Al_{0.3}Ga_{0.7}As/GaAs$ SL (superlattice) current blocking layer. It has been observed that H-plasma treatment didn't affect the band structure of QDIP. It has been also observed that the H-plasma treatment on the QDIP not only enhance the electrical property of QDIP by curing the defect channels in $Al_{0.3}Ga_{0.7}As/GaAs$ SL but also introduce defects in QDIP structure. The H-plasma treatment for 10 min with 20 W of RF power provided the lowest dark current, which made it possible to measure the photo-current (PC) of QDIP whose PC was not detectable without the H-plasma treatment due to the high dark current.
남정우(J.-W. Nam),정세민(S.-M. Jeong),박종천(J.-C. Park),秋元 博路(Hiromichi Akimoto) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
MPS(Moving Particle Simulation) and SPH(Smoothed Particle Hydrodynamics) methods have some serious drawbacks for pressure solution. The pressure field shows spurious high fluctuation both temporally and spatially. One of the reason why the pressure fluctuation is occurred is that free-surface particles are not recognized accurately. The other is the approximation of the partial differential operators. MPS and SPH methods employ a pre-defined kernel function in approximation of the gradient and Laplacian operators. Since the kernel function is constructed artificially, an accurate solution cannot be guaranteed, especially when the distribution of particles is irregular. In this study, we propose a particle simulation method based on the moving least-square technique for solving the partial differential operators by Taylor-series expansion. The developed method was applied to the hydro-static pressure and dam breaking problems for its validation.
무격자법을 이용한 2차원 다중 물체주위의 점성 유동 해석
정세민(S.-M. Jeong),남정우(J.-W. Nam),박종천(J.-C. Park) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
The gridless (or meshfree) methods, such as MPS, SPH, FPM an so forth, are feasible and robust for the problems with moving boundary and/or complicated boundary shapes, because these methods do not need to generate a grid system. In this study, a gridless solver, which is based on the combination of moving least square interpolations on a cloud of points with point collocation for evaluating the derivatives of governing equations, is presented for two-dimensional unsteady incompressible Navier-Stokes problem in the low Reynolds number. A MAC-type algorithm was adopted and the Poission equation for the pressure was solved by successively in the moving least square sense. Flow fields around two-dimensional multi bodies were solved by the presented solver for the validation and the results obtained were compared with experimental and other numerical results by conventional CFD methods, such as FVM.
광학적 방법으로 측정된 양자우물 안의 InAs 양자점의 에너지 준위
남형도,곽호상,송진동,최원준,조운조,이정일,조용훈,최정우,양해석,Nam H.D.,Kwack H.S.,Doynnette L.,Song J.D.,Choi W.J.,Cho W.J.,Lee J.I.,Cho Y.H.,Julien F.H.,Choe J.W.,Yang H.S. 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.2
PL (photoluminescence), PLE (PL excitation) 그리고 근 적외선 투과 분광법을 활용하여 InAsGa/GaAs 우물 내 InAs 양자점 구조의 광학적 특성과 전자 버금 띠 구조에 대하여 연구하였다. 투과 스펙트럼과 PLE 스펙트럼으로부터 InAs 양자점 내 세 개의 구속 상태와 InGaAs/GaAs 우물 내에 두 개의 구속 상태가 존재함을 발견하였고, 광전류 스펙트럼에서 관측된 버금 띠 사이 전이들과 연관지어 해석하였다. We investigated the optical property and the electronic subband structure of InAs quantum dots in an InAsGa/GaAs well structure utilizing photoluminescence (PL), PL excitation (PLE) and near infrared transmission spectroscopy. From transmission and PLE spectra, we found three bound states in the InAs quantum dot and two bound states in InGaAs/GaAs quantum well, and correlated to the results of intersubband transitions observed in photocurrent spectrum.
[가솔린엔진부문] 다양한 조건에서 촉매의 온도 및 유동분포에 관한 수치적 연구
남기우(K.W. Nam),최병철(B.C.Choi),정우남(W.N.Juhug),조창주(C.J.Cho) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Numerical study was carried out to analyze the characteristics of flow and temperature distribution of automotive catalytic converter with various geometries and driving conditions in steady state. The CFD software FLUENT using FVM method was used in this study. Monolith brick was modernled using porous media and heat generation effect on monolith brick was involved with heat source term in energy equation.<br/> It was found that the geometry of the catalytic converter and engine driving conditions had little effect on flow and temperature distribution within converter, and the flow distribution within monolith brick depended strongly on temperature distribution.
파손된 탱크의 기름 유출량 산정을 위한 2차원 입자법 시뮬레이션
남정우(J.-W. Nam),황성철(S.-C. Hwang),박종천(J.-C. Park),M.H. Kim 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
In the present study, the numerical prediction of the oil amount leaked from the hole of a damaged tank is investigated using the improved MPS (Moving Particle Semi-implicit) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flow. The governing equations, which consist of the continuity and Navier-Stokes equations, are solved by Lagrangian moving particles, and all terms expressed by differential operators should be replaced by the particle interaction models based on a Kernel function. The simulation results are validated though the comparison with the analytic solution based on Torricelli’s equilibrium relation. Furthermore, a series of numerical simulations under the various conditions are performed in order to estimate more accurately the initial amount of leaked oil.
송재용 ( J. Y. Song ),사승훈 ( S. H. Sa ),남정우 ( J. W. Nam ),김동환 ( D. H. Kim ),최영우 ( Y. W. Choi ),김진표 ( J. P. Kim ),고재모 ( J. M. Goh ),박남규 ( N. K. Park ) 한국안전학회(구-한국산업안전학회) 2012 한국안전학회지 Vol.27 No.3
We investigated the breakdown patterns of silica glass under the various impacts by forensic scientific analysis. The impacts were chosen by thermal and projectiles impact stress. Thermal impacts under the fire were constructed by changing the position of the flame with gas torches. Physical impacts were constructed with the projectiles of slingshots and rifles by changing the size of the projectiles at the surfaces and the initial distance. Also we identified incident angles of the projectiles by analysis of the punching portion at the glass surface. Under the thermal impacts, the breakdown patterns were various by changing the position of the flame. Especially, the configuration of breakdown patterns had radial shape with the position of the flame at the center of the glass sheet. Under the physical impacts by the projectiles, the breakdown patterns had always radial shape