• 한국응용과학기술학회지
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• 제24권4호
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• pp.354-361
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• 2007

The distribution of light in a randomly scattering medium can represent problems found in many area. Particularly, in the clinical application of lasers for Photodynamic therapy(PDT) or in the fluorescence spectroscopy for biological tissue, turbidity plays a very important role. The influences of fluorophor, scatterer, and absorber in turbid material by light scattering were interpreted for the scattered fluorescence intensity and wavelength. The molecular properties have been studied by laser induced fluorescence spectroscopy in scattering medium as tissue. It has been found that the effects of optical properties in scattering media could be investigated by the optical $parameters({\mu}_s$, ${\mu}_a$ ,${\mu}t)$. Experimental and Monte Carlo simulation method for modelling light transport in tissue was applied. The experimental results using a randomly distributed scattering medium were discussed and compared with those obtained through Monte Carlo simulation. It'll be also important in designing the best model for oil chemistry, medicine and application of medical engineering.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.388-394
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• 2005

A typical honeycomb sandwich panel consists of two thin, high-strength facings bonded to a thick, light-weight core. Each component by itself is relatively weak and flexible, but when it combind in a sandwich panel they produce a structure that is stiff, strong, and lightweight. In addition to use in honeycomb sandwich panels, honeycomb is used for energy absorption, radio frequency shielding, light diffusion, and to direct air flow.Accordingly, the usage of honeycomb sandwich structure is very widely applied to the aircraft, the automobile, and marine industry, etc., because of these advantages. Generally, this honeycomb sandwich structure is manufactured by autoclave process.In this study, the honeycomb sandwich structure was produced by prepreg. To prove the suitability the honeycomb sandwich structure with prepreg, The optimum design of the skin materials and honeycomb sandwich structure were evaluated with the theory of stress analysis.

• Rapid Communication in Photoscience
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• 제4권1호
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• pp.1-8
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• 2015

For understanding molecular mechanisms of photochemical reactions, in particular reactions of proteins with biological functions, it is important to elucidate both the initial reactions from the photoexcited states and the series of subsequent chemical reactions, e.g., conformation, intermolecular interactions (hydrogen bonding, hydrophobic interactions), and inter-protein interactions (oligomer formation, dissociation reactions). Although time-resolved detection of such dynamics is essential, these dynamics have been very difficult to track by traditional spectroscopic techniques. Here, relatively new approaches for probing the dynamics of protein photochemical reactions using time-resolved transient grating (TG) are reviewed. By using this method, a variety of spectrally silent dynamics can be detected and such data provide a valuable description about the reaction scheme. Herein, a blue light sensor protein TePixD is the exemplar. The initial photochemistry for TePixD occurs around the chromophore and is detected readily by light absorption, but subsequent reactions are spectrally silent. The TG experiments revealed conformational changes and changes in inter-protein interactions, which are essential for TePixD function. The TG experiments also showed the importance of fluctuations of the intermediates as the driving force of the reaction. This technique is complementary to optical absorption detection methods. The TG signal contains a variety of unique information, which is difficult to obtain by other methods. The advantages and methods for signal analyses are described in detail in this review.

• 한국인쇄학회지
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• 제26권2호
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• pp.55-64
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• 2008

We designed a UV-LED exposure system which has 365nm dominant wavelength due to the environment-friendly and economical maskless screen plate making. And the photoresist applied on the screen stretched was exposed without mask by beam projector with UV-LED light source. Then it was developed by air spray with $1.7\;kgf/cm^2$ of injection pressure. The pencil hardness and solvent resistance of curing photoresist film were excellent as those of conventional photoresist film and the maximum resolution of line image formed by maskless screen plate making. was $100{\mu}m$, so we could establish the possibility of environment-friendly maskless screen plate making technology. But the sharpness of the patterns were ${\pm}40{\mu}m$ since the exposure system for maskless plate making has weak light intensity and the diffusion of light.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1291-1292
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• 2007

Recently, there were many researches for efficiency improvement of DSC. Among of these works, research of surface treatment is still a prerequisite for electron diffusion, light-harvesting and surface state of DSC.[1] Using of the surface treatment, it can be raise up porosity of $TiO_2$ nano-crystalline structure on photo-electrode. There are chemical, physical, electrical and optical methods which raise up its porosity. In this paper, we have designed and manufactured MOPA-type ultrasonic circuit (100W, frequency and duty variable). Manufactured ultrasonic circuit to use to force cavity density and power into $TiO_2$ paste. Then, we have optimized forcing time, frequency and duty of ultrasonic irradiation for surface treatment of photo-electrode of DSC. In I-V characteristic test of DSC, ultrasonic and thermal treated DSC shows 19% improved its efficiency against monolithic DSC. And it shows stability of light-harvesting from drastically change of light irradiation test.

• Current Optics and Photonics
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• 제4권4호
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• pp.380-390
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• 2020

In this study, the traditional electron-blocking layer (EBL) in (In,Ga)N/GaN light-emitting diodes is replaced by a circular EBL that is the same size as the n-pad. The three-dimensional (3D) nonlinear Poisson, drift-diffusion, and continuity equations are adopted to simulate current transport in the LED and its characteristics. The results indicate that the local carrier-density distribution obtained for the circular EBL design is more uniform than that for the traditional EBL design. This improves the uniformity of local radiative recombination and local internal quantum efficiency (IQE) at high injection levels, which leads to a higher lumped IQE and lower efficiency droop. With the circular EBL, the lumped IQE is higher in the outer active region and lower in the active region under the n-pad. Since most emissions from the active region under the n-pad are absorbed by the n-pad, obviously, an LED with a circular EBL will have a higher external quantum efficiency (EQE). The results also show that this LED works at lower applied voltages.

• 한국재료학회지
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• 제32권1호
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• pp.30-35
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• 2022

The development of advanced materials to improve the efficiency of photoelectrochemical (PEC) water splitting paves the way for widespread renewable energy technologies. Efficient photoanodes with strong absorbance in visible light increases the effectiveness of solar energy conversion systems. MoS₂ in a two-dimensional semiconductor that has excellent absorption performance in visible light and high catalytic activity, showing considerable potential as an agent of PEC water splitting. In this study, we successfully modulated the MoS₂ morphology on indium tin oxide substrate by using the metalorganic chemical vapor deposition method, and applied the PEC application. The PEC photocurrent of the vertically grown MoS₂ nanosheet structure significantly increased relative to that of MoS₂ nanoparticles because of the efficient transfer of charge carriers and high-density active sites. The enhanced photocurrent was attributed to the efficient charge separation and improved light absorption of the MoS₂ nanosheet structure. Meanwhile, the photocurrent property of thick nanosheets decreased because of the limit imposed by the diffusion lengths of carriers. This study proposes a valuable photoelectrode design with suitable nanosheet morphology for efficient PEC water splitting.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.590-590
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• 2012

A transparent conducting oxide (TCO) layer was applied in crystalline Si (c-Si) solar cells without use of the conventional SiNx-coating. A high quality indium-tin-oxide (ITO) layer was directly deposited on an emitter layer of a Si wafer. Three different types of emitters were formed by controlling the phosphorous diffusion condition. A light-doped emitter forming a thinner emitter junction showed an improved photoconversion efficiency of 14.1% comparing to 13.2% of a heavy-doped emitter. This was induced by lower recombination within a narrower depletion region of the light-doped emitter. In the aspect of light management, the intermediate refractive index of ITO is effective to reduce the light reflection leading the enhanced carrier generation in a Si absorber. For the electrical aspect, the ITO layer serves as an efficient electrical conductor and thus relieves the burden of high contact resistance of the light-doped emitter. Additionally, the ITO works as a buffer layer of Ag and Si and certainly prevents the shunting problem of Ag penetration into Si emitter region. It discusses an efficient design scheme of TCO-embedded emitter Si solar cells.

• 한국재료학회지
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• 제28권11호
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• pp.680-684
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• 2018

We investigate the effect of light intensity and wavelength of a solar cell device using photoconductive atomic force microscopy(PC-AFM). A $POCl_3$ diffusion doping process is used to produce a p-n junction solar cell device based on a polySi wafer, and the electrical properties of prepared solar cells are measured using a solar cell simulator system. The measured open circuit voltage($V_{oc}$) is 0.59 V and the short circuit current($I_{sc}$) is 48.5 mA. Moreover, the values of the fill factors and efficiencies of the devices are 0.7 and approximately 13.6 %, respectively. In addition, PC-AFM, a recent notable method for nano-scale characterization of photovoltaic elements, is used for direct measurements of photoelectric characteristics in limited areas instead of large areas. The effects of changes in the intensity and wavelength of light shining on the element on the photoelectric characteristics are observed. Results obtained through PC-AFM are compared with the electric/optical characteristics data obtained through a solar simulator. The voltage($V_{PC-AFM}$) at which the current is 0 A in the I-V characteristic curves increases sharply up to $18W/m^2$, peaking and slowly falling as light intensity increases. Here, $V_{PC-AFM}$ at $18W/m^2$ is 0.29 V, which corresponds to 59 % of the average $V_{oc}$ value, as measured with the solar simulator. Furthermore, while the light wavelength increases from 300 nm to 1,100 nm, the external quantum efficiency(EQE) and results from PC-AFM show similar trends at the macro scale but reveal different results in several sections, indicating the need for detailed analysis and improvement in the future.

• 한국정보전자통신기술학회논문지
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• 제11권5호
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• pp.608-614
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• 2018

ICT기술 확산과 더불어 효율적인 정보 운용을 위해 다양한 프로토콜의 근거리 무선통신기술이 적용되고 있다. 하지만 근거리 무선통신의 제한사항으로 인하여 주파수 혼선 및 창고형 공장 등 주파수 환경이 좋지 않은 곳에서 통신이 원활하지 못하다. 이에 대한 대안이 필요한 시점에 LED 기술의 발달과 빠른 보급을 통한 인프라 확충으로 LED 기반 가시광 통신이 대안으로 주목되고 넒은 분야에 확산되고 있다. 또한 신재생에너지 활성화에 맞춰 태양광 패널 또한 빠른 보급으로 인프라가 확충되어 있다. 이러한 상황에서 PD를 활용한 가시광 통신은 PD의 수신각도 및 주변 환경의 빛으로 인해 LoS가 확보되고 주변의 빛에 영향이 적은 초근거리 환경에서 제한적으로 적용되어 왔다. 이를 해결하고자 현재 인프라가 확충되어 있는 LED 조명과 수신 면적이 넓은 태양광 패널을 이용하여 가시광 통신을 구현하였으며, 주변 환경 빛에서도 정확한 데이터를 복원을 위한 회로를 제안하였다. 본 연구결과를 통해 태양광 패널을 수신부로 하는 가시광 통신 연구의 기반 자료로 활용 되어 가시광 통신이 더욱 넓게 응용될 것으로 기대한다.