• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.784-793
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• 2016

We present a single shot low coherence white light Hilbert phase microscopy (WL-HPM) for quantitative phase imaging of Si optoelectronic devices, i.e., Si integrated circuits (Si-ICs) and Si solar cells. White light interferograms were recorded by a color CCD camera and the interferogram is decomposed into the three colors red, green and blue. Spatial carrier frequency of the WL interferogram was increased sufficiently by means of introducing a tilt in the interferometer. Hilbert transform fringe analysis was used to reconstruct the phase map for red, green and blue colors from the single interferogram. 3D step height map of Si-ICs and Si solar cells was reconstructed at multiple wavelengths from a single interferogram. Experimental results were compared with Atomic Force Microscopy and they were found to be close to each other. The present technique is non-contact, full-field and fast for the determination of surface roughness variation and morphological features of the objects at multiple wavelengths.

• 한국버섯학회지
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• 제11권1호
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• pp.24-31
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• 2013

선행연구로서 꽃송이버섯 배지내 LED 조명색에 의한 푸른곰팡이 생육억제 효과는 모든 처리구에서 생육이 억제되었으나 blue 처리구에서 푸른곰팡이균의 포자발생량이 매우 높아 꽃송이버섯 배양에 부적합하다는 것으로 확인되었다. 배양 28일 후 LED 파장에 따른 꽃송이버섯의 균사생장 특성과 LED 파장 색상별 배양시간의 경과에 따른 균사생장 특성을 조사한 결과 모두 red 파장 처리구에서 균사생장이 높은 경향을 나타내었다. 이에 따라 red 파장 범위에서 광량을 달리하여 균사생장 조건을 확인한 결과, 광량 세기가 낮은 1.41 ${\mu}mol/m^2S$ 처리구에서 우수한 균사생장을 나타내었다. 계대배양 실시 여부에 따른 균사생장 특성에서는 실험 전 1회 계대배양을 실시한 처리구에서 유의적인 차이를 나타내었다. 배지조성을 달리한 톱밥배지 내 LED 광량별 균사생장은 미송 처리구에서 높은 경향을 나타내었다. 이를 미송 톱밥배지에서 LED red 2.11 ${\mu}mol/m^2S$의 광량을 처리하였을 경우 84일 배양한 처리구에서 유의적인 차이를 보였다. 상기의 결과를 종합하여 보았을 경우 red 파장 2.11 ${\mu}mol/m^2S$ 광량에서 84일 이상 미송 톱밥배지에서 배양하는 것이 꽃송이버섯 배양에 좋을 것으로 판단되었다.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.10-18
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• 2011

In order to develop highly-integrated RGBY(Red, Green, Blue, Yellow) LED light, a high thermal radiation ceramic package was manufactured, and the encapsulation process was applied with a vacuum printing encapsulation system(VPES). After the completion of vacuum printing, the shape of the encapsulation layer could be controlled by heat treatment during the curing process, and the optical power became highly increased as the encapsulation layer approached a dome shape. The optical characteristics involved in a Correlated Color Temperature(CCT), a Color Rendering Index (CRI), and the efficiency of RGBY LED light were able to be identified by the experimental designing method. Regarding the characteristics of the white light of RGBY LED light, which were measured on the basis of the aforementioned optical characteristics, CRI posted 88, CCT recorded 5,720[$^{\circ}K$], and efficiency exhibited 52[lm/W]. The chip temperature of RGBY LEDs was below 55[$^{\circ}C$] when the consumption power of LED chips was 0.1[W] for the red, 0.3[W] for the green, 0.08[W] for the blue, and 0.24[W] for the yellow. Also, the thermal resistance of the highly-integrated RGBY LED light measured by T3Ster was 2.3[K/W].

• 한국표면공학회지
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• 제48권5호
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• pp.211-217
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• 2015

To fabricate white LED having a high color rendering index value, red color phosphor mixed with the green color phosphor together in the blue chip, namely the blue chips with RG phosphors packaging is most favorable for high power white LEDs. In our previous papers, we reported on successful syntheses of $Sr_{2-}$ $Si_5N_8:Eu^{2+}$ and $CaAlSiN_3$ phosphors for red phosphor. In this work, for high power green phosphor, greenemitting ternary nitride $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphor was synthesized in a high frequency induction furnace under $N_2$ gas atmosphere at temperatures up to $1400^{\circ}C$ using $EuF_3$ as a raw material for $Eu^{2+}$ dopant. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 250 - 500 nm, namely from UV to blue region with distinct enhanced emission spectrum peaking at ${\approx}530nm$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1540-1545
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• 2004

Measurement of concentration fields in a micro-channel is the crucial technology in the area of Lab-on-a-chip to be used for various bio-chemical applications. It is wel-known that the only possible way to measure the concentration field in the micro-channel is using micro-LIF(Laser Induced Fluorescence) method. However, an accurate concentration field at a given cross plane in a micro-channel has not been made so far due to the limit of light illumination. The present study demonstrates a novel method to provide an ultra thin laser sheet beam having 5 microns thickness by a micro focus laser line generator. Nile Blue A was used as fluorescent dye for LIF measurement. The laser sheet beam illuminates an exact plane of concentration measurement in the micro-channel to increase the signal to noise ratio and reduce the depth uncertainty considerably.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1686-1687
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• 2011

A microfabricated chip with in-channel electrochemical cell using interdigitated gold electrode was fabricated for sensitive electrochemical analysis. The gold electrodes were fabricated on glass wafer using thermal evaporator and were covered using PDMS mold containing microchannel for analyte and electrolyte. The active area of each electrode was $250\;{\mu}m{\times}200\;{\mu}m$ with a gap of 200 ${\mu}m$ between the electrodes. Microelectrodes results in maximum amplification of signal, since the signal enhancement effect due to cycling of the reduced and oxidized species strongly depends on the inter electrode distance. Analytes such as methylene blue and guanosine were characterized using the fabricated electrodes and their electrochemical characteristics were compared with conventional bulk electrodes. The device so developed shall find use as disposable electrochemical cell for rapid and sensitive analysis of electroactive species.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.23-23
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• 2003

GaN-related semiconductors are of great technological importance for the fabrication of optoelectronic devices, such as blue and ultra violet light emitting diodes (LEDs), laser diodes, and photo-detectors. One of the most important applications of GaN-based LEDs is solid-state lighting, which could replace incandescent bulbs and ultimately fluorescent lamps. For solid-state lighting applications, the achievement of high extraction efficiency in LED structures is essential. For flip-chip LEDs (FCLEDS), the formation of low resistance and high reflective p-GaN contact is crucial. So far, a wide variety of different methods have been employed to improve the ohmic properties of p-type contacts to GaN. For example, surface treatments using different chemical solutions have been successfully used to produce high-quality ohmic contacts, Metallization schemes, such as Ta/Ti contacts to p-GaN, were also investigated. For these contacts, the removal of hydrogen atoms from the Mg atoms doped n the GaN was argued to be responsible for low contact resistances.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2011년도 춘계학술논문집 2부
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• pp.792-795
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• 2011

After the year of 2000, compositions of stock holders in domestic firms are rapidly changing. In domestic stock market, the proportion of market value held by foreign investors reaches over 40%. There are several blue chip companies among those where foreign investors hold more than 50% of the stocks. There are still hot debates going on about whether the increase in the number of foreign investors contributes to domestic companies. This research attempted to determine foreign ownership increases enhance firm value empirically. It has been shown that foreign ownership variable has significant positive impact on Tobin's Q of firm value variable. The result suggests that foreign ownership increases in domestic corporations positively contribute to firm value, as they monitor and keep the management transparent as an institutional investor, and they work to soothe agency problems by the managements or the large stock holders.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.238-240
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• 2006

In this study, we designed a digital inclinometer to measure the angle and acceleration signals. Digital inclinometer consists of a tilt sensor, accelerometer, one-chip micro controller and BlueTooth module. Using the developed system, we made an experiment with Roll. The subject is laid on the Roll and rises each foot $90^{\circ}$ and $45^{\circ}$ up, and measures angle and acceleration signals with 100Hz sampling frequency. Through several tests, we could find the possibilities and usefulness which can evaluate normality / abnormality of body posture objectively.

• 한국안광학회지
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• 제8권1호
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• pp.23-28
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• 2003

랩온어칩을 위한 변환 가능한 RGB 색상 필터를 연구하였다. 잉크 색상 필터는 PDMS 패턴과정에 의한 공정으로 제작하였고, 칼라 필터의 자외선-가시광선 영역의 광투과율을 조사하였다. 잉크 칼라 필터는 스펙트럼의 모양과 기울기에 의해 특성 지워진다. 적색/황색 필터의 투과는 600 nm와 500 nm에서 차단스펙트럼 모양을 가지는 곡선으로 구성되었다. 잉크 필터의 청색 출력은 80% 피크 투과율과 약한 적색 누수를 보였다. 한편 녹색 잉크 필터는 48% 피크 투과율과 적색 누수 투과를 보였다.