• Journal of Power Electronics
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• 제16권2호
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• pp.631-642
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• 2016

Usually, the output characteristics of a photovoltaic (PV) array are significantly affected by non-uniform irradiance which is caused by ambient obstacles, clouds, orientations, tilts, etc. Some local maximum power points (LMPP) in the current-voltage (I-V) curves of a PV array can result in power losses of the array. However, the output power at the global maximum power point (GMPP) is different in different interconnection schemes in a PV array. Therefore, based on the theoretical analysis and mathematical derivation of different topological structures of a PV array, this paper investigated the output characteristics of dual series PV arrays with different interconnections. The proposed mathematical models were also validated by experimental results. Finally, this paper also concluded that in terms of performance, the total cross tied (TCT) interconnection was not always the optimal structure, especially in a dual series PV array. When one of the PV modules was severely mismatched, the TCT worked worse than the series parallel (SP) structure. This research can provide guidance for switching the interconnection to gain the greatest energy yield in a changeable- structure PV system.

• 한국전산유체공학회지
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• 제22권1호
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• pp.88-94
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• 2017

The IR signal entering into a sensor is composed of the following components: the self-emitted component directly from the object surface, the reflected components of the solar and sky irradiance at the object surface, and the scattered component by the atmosphere without reference to any object surfaces. The self-emitted and reflected components from the object can be lowered by the atmospheric layer between the object and the IR sensor. The principle factors influencing the atmospheric transmittance are the air temperature, the relative humidity and the observation distance. Previous studies on IR signal transmission through the atmosphere are focused on uniform atmospheric conditions and the non-uniform nature of the atmosphere was not properly treated in modeling. In this study, we use the local atmospheric transmittance to simulate the non-uniform atmosphere in analyzing the IR signal from the object surface. The results show that the nonuniform analysis of the atmosphere becomes more important as the wavelength of IR signal increases.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.303-308
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• 2009

In 2008, the global photovoltaic(PV) market reached 5.6GW and the cumulative PV power installed totalled almost 15GW compared to 9GW in 2007. Due to a favourable feed-in-tariff, Korea emerged in 2008 as the 4th largest PV market worldwide. PV power installation rose 495.5 percent to 268MW in 2008 compare to 45MW in 2007. However many PV systems are not installed in suitable part which is concerned about geometrical factor. It is generally recognized that the actual output of PV system in field is a function of orientation, tilt angle, irradiance, temperature, soiling and various system-related losses. Thus this paper shows that a experimental result of PV modules(A group) with uniform azimuth angle and PV modules(B group) with non-uniform azimuth angle. As a result, the electrical output of B group is decreased 48.8% as compared with electrical output of A group.

• 반도체디스플레이기술학회지
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• 제21권1호
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• pp.114-118
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• 2022

The photovoltaic system is affected by various conditions such as temperature and irradiance. Because non-uniform irradiation and partial shading conditions affect the entire string of cells connected in series, a bypass diode is used to bypass the current flow normally. In order to find the maximum power point in partial shade conditions, it is necessary to estimate various methods of maximum power point tracking. In this paper, the hybrid method of MPPT using Lambert W function and perturbation & observation algorithm is proposed under partial shading conditions. The simulation results are obtained using MATLAB/Simulink and shows the improvement of the accuracy of MPPT.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.156-158
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• 2007

The radiance observed from the ocean depends on the illumination and viewing geometry along with the water properties, and this variation is called the bidirectional effect which is important to be considered in ocean color remote sensing. In the present study, as a preliminary step, the spectral-angular radiances in coastal water were investigated with experiments for a range of viewing geometric conditions $(0-70^{\circ})$. Over a phytoplankton-dominated water surface the upward radiance for visible and near-infrared wavelengths (example, SeaWiFS and GOCI) increased at nadir and decreased toward the near-horizon, becoming dependent of viewing angles (with higher radiance at nadir view angle and lower radiance at near-horizon viewing angle). This variations were better expressed by the Q-factor, which relates upwelling radiance to the upwelling irradiance (i.e., $Q=E_u/L_u$, also dependent on Sun's position). The Q-factor for this case was more non-uniform with the considered wavelengths and was dependent on viewing geometric conditions. These experimental results confirm the previous similar findings in other coastal waters.

• 전자공학회논문지B
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• 제29B권7호
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• pp.52-61
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• 1992

본 논문은 단시안에 투영된 3차원 물체의 Image에서 측정된 명암강도의 차이를 이용하여 3차원 물체의 절대거리 z 및 형상을 유출하는 수치적인 방법을 연구, 단시안에 의해서도 Camera와 물체사이의 3차원 절대거리가 구해질 수 있음을 보여주고 있다. 기발표된 이론과는 다르게 본 논문에서는 점광원을 이용하여 투영된 명암강도와 3차원 물체의 절대거리 및 형상과의 관계를 물체가 Uniform Lambertian이라는 가정하에서 새로운 관계식으로 정립하였다. 정립된 Non-Linear 관계식은 Smoothness 조건아래 $'Calculus of Variation$'방법을 사용하여 수학적 Algorithm으로 정리되어 Programming 되었고 간단한 실험방법을 이용하여 실제 Data에 적용시켜 그 타당성을 조사하였다.당성을 조사하였다.

• Korean Chemical Engineering Research
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• 제60권4호
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• pp.535-543
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• 2022

실리콘 카바이드 입자(평균 입도 123 ㎛)의 유동층 태양열 흡열기의 성능 및 효율에 영향을 미치는 입자 거동 해석을 위해 MP-PIC 모델을 이용하여 전산모사를 수행하였고, 기존 실험결과와의 비교를 통해 검증하였다. 특히, 본 연구에서는 실험적으로 접근하기 어려운 유동층 표면 부근에서의 거동을 모사함으로써 흡열 성능과 입자 거동과의 상호 영향을 분석하였다. CPFD 모사결과는 입자층 및 프리보드에서의 평균 고체체류량과 압력요동 등 수력학적 특성 실험결과를 잘 예측하였다. 입자 흡열기에서 1차적으로 태양열 에너지를 흡수하여 층 내부로 전달하는 층 표면 부근에서의 국부 고체체류량은 입자층 내 기포거동에 따라 중심부에서 상대적으로 낮은 값을 나타내는 불균일 분포를 나타내었다. 프리보드 영역에서 국부 고체체류량은 기체속도가 증가할수록 축방향과 각 높이에서의 횡방향에서 불균일성이 증가하였고, 이는 입자 흡열기의 프리보드 영역 내 비산된 입자에 의해 반사된 태양광 에너지 손실과 연관된 압력강하 상대표준편차 증가의 원인임을 나타내었다. 입자 흡열기 내 기체속도 증가에 따른 국부적인 기체 및 입자 속도의 변화에 대한 고찰을 통해, 유동층 내 국부적인 입자거동 특성은 Geldart B 입자 물성과 관련된 입자층 내 기포 거동과 밀접하게 연관됨을 확인하였다. 유동층 입자 흡열기의 성능 척도인 일사량 당 유동기체의 출입구 온도차(∆T/I_DNI)는 입자 층 표면 및 표면 상부 프리보드 영역 내 압력요동 RSD와 상관관계가 매우 높음을 확인하였고, 이 결과는 흡열기 성능 개선에 활용할 수 있을 것으로 판단되었다.