• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.2
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• pp.97-102
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• 2012

CPV system in the desert areas or areas near the equator, as is suitable for high-temperature region. As compared to silicon solar cells, CPV system have a high proportion of a BOS (balance of system). Solar cells because of its low proportion when designing a module technology is applied in a variety of ways. Applied to the CPV system is classified into two kinds of optical technology. One of those using fresnel lens uses refraction of light energy. The other is a mirror reflection of the structure using sprays. Both of these two ways to condense the sun to collect solar cell is a form of light. And goals by using a small solar cell materials is to produce more energy. In this paper, suitable for a domestic environment, with the aim CPV Manufacturing Technology, built on a variety of modular process technology to the development of a prototype performance analysis was carried out. In particular, silicone coated on the glass by the method of implementation of the Fresnel lens SOG(Silicon on glass) by applying the lens to absorb the solar spectrum was broad. In addition to, for the analyze to characteristics of the CPV module, developed CPV module performance and generating characteristics studied. These related technology through research and development of high-performance multi-junction solar cells, modules, development of concentrating solar power systems to facilitate the growth of the market is considered to be.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.975-982
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• 2010

In this study, the laser sintering of inkjet-printed silver lines was evaluated. Silver-nanoparticle ink and a drop-ondemand (DOD) inkjet printer were used for printing on glass and polyethylene terephthalate (PET) substrates with various thicknesses. To sinter the printed silver nanoparticles, the silver layer printed on the transparent substrates was irradiated by focused CW laser beams that were incident normal to the substrates; the irradiation was carried out for various beam intensities and for various irradiation times. The electrical conductivity of the laser-sintered silver patterns was measured and compared with the conductivity of silver patterns sintered by using an oven. The increase in the temperature caused by laser irradiation was also calculated on the basis of the laser beam intensity, irradiation time, surface reflectivity, and thermophysical property of the substrate in order to estimate the increase in the electrical conductivity caused by laser sintering.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.168-172
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• 2014

Under concentrated illuminations, the solar cells show higher efficiencies mainly due to an increase of the open circuit voltage. In this study, InGaP/InGaAs/Ge triple-junction solar cells have been grown by a low pressure metalorganic chemical vapor deposition. Photovoltaic characteristics of the fabricated solar cells are investigated with a class A solar simulator under concentrated illuminations from 1 to 100 suns. Ideally, the open circuit voltage should increase with the current level when maintained at the same temperature. However, the fabricated solar cells show degraded open circuit voltages under high concentrations around 100 suns. This means that the heat sink design is not optimized to keep the cell temperature at $25^{\circ}C$. To demonstrate the thermal degradation, changes of the device performance are investigated with different bonding conditions and heat sink materials.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.15-20
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• 2009

In a detection system based on laser light scattering, focusing an excitation laser beam into a focal point of a channel in a microfluidic chip is important for obtaining the highest excitation intensity, and consequently for obtaining a laser light scattering signal using a photodetector with a high efficiency. In this paper, we present a polydimethylsiloxane (PDMS) microfluidic chip consisting of an integrated PDMS microlens for cell detection based on laser light scattering. We fabricated PDMS microlens for optical detection system by simply putting down on PDMS chips. The PDMS microlens was fabricated by photoresist reflow and replica molding. This fabrication technique is simple and has an excellent property in terms of the microlens and a high-dimensional accuracy. The PDMS microlens integrated on the PDMS microfluidic chip has been verified to improve the laser intensity, and accordingly, the signal-to-noise ratio and sensitivity of laser light scattering detection for red blood cells(RBCs)

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.519-526
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• 2004

We developed a 2-D imaging system to detect ultra weak biophoton by using a high sensitive fast CCD camera. We installed an illumination apparatus to generate delayed luminescence from plant leaves. Shutters at the illumination system and detector were synchronized to each other. The lens system of the CCD camera was newly designed to accommodate the specific requirements to enhance the collection efficiency for biophoton. Based on the lens simulation, commercial lenses were chose for the lens system. All the equipment was installed in a multi-purpose dark box and the delayed luminescence of Euonymus japonica was successfully acquired.

• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.53-58
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• 2017

This paper presents the design and fabrication of a planar nano-diffraction grating for an integrated miniature spectrometer module. The proposed planar nano-diffraction grating consists of nonuniform periods, to focus the reflected beams from the grating's surface, and an asymmetrical V-shaped groove profile, to provide uniform diffraction efficiency in the wavelength range from 400 to 650 nm. Also, to fabricate the nano-diffraction grating using low-cost UV-NIL technology, we analyzed the FT-IR spectrum of a uvcurable resin and optimized the conditions for the UV curing process. Then, we precisely fabricated the polymeric nano-diffraction grating within 5 nm in dimensional accuracy. The integrated spectrometer module using the fabricated polymeric planar nano-diffraction grating provides spectral resolution of 5 nm and spectral bandwidth of 250 nm. Our integrated spectrometer module using a polymeric planar nano-diffraction grating serves as a quick and easy solution for many spectrometric applications.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.39.4-40
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• 2018

KMTNet 광시야 망원경의 성능 개선을 위해 2017년에 이루어진 주요 작업으로 주경 배플(baffle) 설치, 주경 코팅, 돔 플랫(dome flat) 장치 설치에 대해 발표한다. 망원경 주경의 가장자리(turn down edge)는 경면 가공이나 코팅 상태가 균질하지 않을 수 있으며, 이로 인한 난반사는 밝은 별 주위에 넓은 wing profile과 여러 갈래의 방사상 빛줄기를 만든다. 이런 난반사를 제거하기 위해 주경면 바로 앞에 배플을 설치하였다. 주경의 광학 성능과 집광력이 최적이 되도록 배플 내부 직경 값을 1,580 mm로 조정하여 설치한 결과, 관측 영상에서 별의 영상이 크게 개선되었다. 호주 관측소는 상대적으로 습기가 높아서 망원경 주경의 반사율이 빨리 낮아졌으며, 이를 개선하기 위해 기존의 코팅(protected silver)을 제거하고 알루미늄으로 새로 코팅하였다. KMTNet 3개 관측소는 주경의 반사율과 코팅 면의 확대 영상을 정기적으로 모니터링하여 광학 성능의 변화를 추적하고 있다. 밤하늘 플랫(twilight sky flat) 영상을 보완하기 위해, 돔 인클로져에 플랫 스크린과 광원을 설치하여 돔 플랫 영상을 획득하였다. 마지막으로 KMNet 관측시스템을 운영하며 발생한 돔 회전 및 돔 셔터 구동부 문제 등에 대해 소개하고, 문제 발생 원인과 주기, 문제 해결 방안을 발표한다.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.63-67
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• 2015

White light-emitting diode (WLED) is growing interest in using both illumination and communications. This paper reports visible light communication (VLC) composed of a super bright white light-emitting diode, low cost commercial photo-diode and a Fresnel lens. LED driver is consisted of the power MOSFET and MOSFET driver that switches the LED on and off. The modulation bandwidth of the LED used was determined to be 8 MHz. However, it was possible to communicate up to 1 Mbps under illumination of 500 lx because of the weak signal power and a low spectral sensitivity of the SHF213 as a PIN photodiode. In order to enhance the system bandwidth, the LED light was focused on the PIN photodiode by use of the Fresnel lens. As a result of that, visible light link was operated up to modulation bandwidth of the LED. The signal to noise ratio can be improved by 40 dB using an optical concentration at the receiver.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1383-1389
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• 2011

The current study focuses on the consistent analysis of heat transfer in multichannel volumetric solar receivers used for concentrating solar power. Changes in the properties of the absorbing material and channel dimensions are considered in an optical model based on the Monte Carlo ray-tracing method and in a one-dimensional heat transfer model that includes conduction, convection, and radiation. The optical model results show that most of the solar radiation energy is absorbed within a very small channel length of around 15 mm because of the large length-to-radius ratio. Classification of radiation losses reveals that at low absorptivity, increased reflection losses cause reduction of the receiver efficiency, notwithstanding the decrease in the emission loss. As the average temperature increases because of the large channel radius or small mass flow rate, both emission and reflection losses increase but the effect of emission losses prevails.

• Polymer(Korea)
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• v.29 no.4
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• pp.418-421
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• 2005

Three-dimensional (3D) microfabrication process using two-photon polymerization (TPP) is developed to fabricate the curved microstructures in a layer, which can be applied potentially to optical MEMS, nano/micro-devices, etc. A 3D curved structure can be expressed using the same height-contours that are defined by symbolic colors which consist of 14 colors. Then, the designed bitmap figure is transformed into a multi-exposure voxel matrix (MVM). In this work a multi-exposure voxel matrix scanning method is used to generate various heights of voxels according to each laser exposure time that is assigned to the symbolic colors. An objective lens with a numerical aperture of 1.25 is employed to enlarge the variation of a voxel height in the range of 1.2 to 6.4 um which can be controlled easily using the various exposure time. Though this work some 3D curved micro-shapes are fabricated directly to demonstrate the usefulness of the process without a laminating process that is generally required in a micro-stereolithography process.