• The Journal of the Korea Contents Association
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• v.12 no.2
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• pp.69-77
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• 2012

In the case of the password-based PKI technology, because it protects by using the password which is easy that user memorizes the private key, he has the problem about the password exposure. In addition, in the system of electronic bidding, the illegal use using the authentic certificate of the others increases. Recently, in order to solve this problem, the research about the PKI technology using the biometrics is actively progressed. If the bio information which the user inputs for the bio authentication is converted to the template, the digest access authentication in which the security is strengthened than the existing authentication technology can be built. Therefore, in this paper, we had designed and developed the system of electronic bidding which it uses the most widely used fingerprint information in the biometrics, it stores the user fingerprint information and certificate in the fingerprint security token and can authenticate the user. In case of using the system of electronic bidding of the public key infrastructure using the fingerprint information proposed in this paper the agent bid problem that it uses the certificate of the others in not only user authentication intensification but also system of electronic bidding can be concluded.

• Polymer(Korea)
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• v.31 no.5
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• pp.393-398
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• 2007

We studied the mechanism of liquid crystal alignment on polyvinylfluorocinnamate (PVCN-F) films which were irradiated by UV using polarized fourier transform infrared (FT-IR) spectroscopy and ultraviolet/visible (UV/Vis) spectroscopy. UV irradiation of PVCN-F films caused decrease of vinylene -C=C- stretching peak area at $1638cm^{-1}$ and shift of conjugated C:0 stretching vibration at $1712cm^{-1}\;to\;1734cm^{-1}$ which is caused by nonconjugated C=O stretching nitration. To study the orientation direction of 5CB liquid crystal (LC) molecules in the liquid crystal cell with PUV irradiation, rubbing treatment or without any treatment on the PVCN-F alignment layer, we used polarized FT-IR dichroism technique. We successfully measured 5CB LC alignment directions, which are perpendicular to the irradiated PUV polarization direction and parallel to the rubbing direction in the liquid crystal cell without using dichroic dyes.

• Journal of Digital Contents Society
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• v.19 no.7
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• pp.1397-1403
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• 2018

Today, modern people perceive skin care as part of their physical health care, and acne is a common skin disease problem that is found on the face. In this paper, an effective acne detection algorithm using CIE $L^*a^*b^*$ color space has been proposed. It is red when the pixel value of the component image $a^*$ is a positive number, so it is suitable for detecting acne in skin image. First, the skin image based on the RGB color space is subjected to light compensation through color balancing, and converted into a CIE $L^*a^*b^*$ color space. The extracted component image $a^*$ was normalized, and then the skin and acne area were estimated with the threshold values. Experimental results show that the proposed method detects acne more effectively than the conventional method based on brightness information, and the proposed method is robust against the reflected light source.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.111-126
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• 2009

We used an optical observation system with a 0.6m wide-field telescope and 5 computers system in KASI (Korean Astronomy and Space Science Institute) for satellite optical observation. Optical data have errors that are caused by targeting, expose start time and end-point determination. Gauss method for initial orbit determination was tested using angle-only data simulated by KODAS. And suitable time span is confirmed for result which has minimum errors. Initial orbit determination results are proved that optical observation system in KASI is possible satellite tracking for a short period. And also through differential correction, initial orbit determination results are improved.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.8-17
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• 2012

In this paper we proposes a new framework to obtain 3D shape information of thin film rapidly. The conventional equipments based on reflectometry are not suitable for obtaining 3D overall shape information of thin film rapidly since they require more than 30 minutes to measure the absolute thickness for 170 points. The proposed framework is based on an image analysis method that extracts contour lines from interference fringes images using Canny edge detector. The absolute thickness for contour lines are measured and then a height map from the contour lines is obtained by interpolation using Borgefors distance transformation. The extracted height map is visualized using the DirectX 3D terrain rendering method. The proposed framework can provide 3D overall shape information of thin film in about 5 minutes since relatively small number of real measurement for contour lines is required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.473-482
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• 1998

In this paper, characteristics of the wide band microstrip antennas with parasistic element are analyzed by the Finite Difference Time Domain(FDTD) method, and antenna parameters are optimized to get maximum bandwidth, retern loss, input impedance, and radiation pattern are calculated by Founier transforming the time domain results. The characteristics of the antenna are varied and the bandwidth of the antenna is broaded as a length and a width of the driven element, a gap of the driven element and the parasitic element, a width and a length of parasitic element. So the different patchs are resonating at different frequencies and this multipule resonance increase the bandwidth. The Results of the calculation and measurement, the size of the antenna with parasitic element is about a twice larger than a microstrip antenna, but bandwidth is four times better than a microstrip antenna. And these results were in relatively good accordance with the measured values.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.454-459
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• 2013

Recently, remote phosphors have been reported for application to white LEDs to provide enhanced phosphor efficiency compared with conventional phosphor-based white LEDs. In this study, a remote phosphor was produced by coating via screen printing on a glass substrate with different numbers of phosphor coating. The paste consists of phosphor, lowest softening glass frits, and organic binders. The remote phosphor could be well controlled by varying the phosphor content rated paste. After mounting the remote phosphor on top of a blue LED chip, CCT, CRI, and luminance efficiency were measured and values of 5300 K, 62, and 117 lm/W were respectively obtained in the 80 wt% phosphor with 3 coating layers sintered at $800^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.32-32
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• 2008

X-ray detector는 의료용, 산업용 등 다양한 분야에서 사용되어지고 있으며 기존의 Analog X-ray 방식의 환경오염, 저장공간 부족, 실시간 분석의 어려움 등의 문제점들을 해결하기 위하여 Digital X-ray로의 전환과 연구가 활발하며 이에 따른 관심도 높아지고 있는 살점이다. Digital X-ray detector는 p-영역과 n-영역 사이에 아무런 불순물을 도핑하지 않은 진성반도체(intrinsic semiconductor) 층을 접합시킨 이종접합 PIN 구조의 photodiode 이다. 이 소자는 역바이어스를 가해주면 p영역과 n영역 사이에서 캐리어 (carrier)가 존재하지 않는 공핍 영역이 발생하게 된다. 이런 공핍 영역에서 광흡수가 일어나면, 전자-정공 쌍이 발생한다. 그리고, 발생한 전자-정공 쌍에 전압이 역방향으로 인가되는 경우, 전자는 양의 전극으로 이동하고, 정공은 음의 전극으로 이동한다. 이와 같이, 발생한 캐리어들을 검출하여 전기적인 신호로 변환 시킨다. 고해상도의 Digital X-ray detector를 만들기 위해서는 누설전류에 의한 noise 감소와 소자의 높은 안정성과 내구성을 위한 높은 breakdown voltage를 가져야 한다. 본 연구에서는 Digital X-ray detector의 leakage current 감소와 breakdown voltage를 높이기 위하여 guradring과 gettering technology를 사용하여 전기적 특성을 분석하였다. 기판으로는 $10k\Omega{\cdot}cm$ resistivity를 갖으며, n-type <111>인 1mm 두께의 4인치 Si wafer를 사용하였다. 그리고 pixel pitch는 $100{\mu}m$이며 active area는 $80{\mu}m{\times}80{\mu}m$인 $32\times32$ array를 형성하여 X-ray를 조사하여 소자의 특성을 평가 하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.614-619
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• 2013

Recently, remote phosphor is reported for white LED enhancing of phosphor efficiency compared with conventional phosphor-based W-LED. In this study, Remote phosphor was produced by screen printing coating on glass substrate with phosphor contents rated paste and heat treatment. The paste consists of phosphor, lowest softening glass frit and organic binders. Remote phosphor can be well controlled by varying the phosphor content rated paste. After mounting remote phosphor on top of blue LED chip, CCT, CRI, and luminance efficiency were measured. The measurement results showed that CCT, CRI, and luminance efficiency were 6,645, 68, and 1,16l m/W in phosphor 80 wt.% remote phosphor sintered at $600^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.333-339
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• 2011

In this work, electrochemical characteristics and optical transmittance of carbon nanotubes (CNTs) counter electrodes which had different amount of CNTs in CNTs slurries were analyzed. Two-step heat treatment processes were applied to achieve well-fabricated CNTs electrode. Three sets of CNTs electrodes and dye-sensitized solar cells (DSSCs) with CNTs counter electrodes were prepared. As the amount of CNTs increased, sheet resistance of CNTs electrode decreased. CNTs electrode with low sheet resistance had low electrochemical impedance and fast redox reaction. On the other hand, in case of CNTs counter electrode with low density of CNTs, performance of the dye-sensitized solar cell was improved due to its high optical transmittance. We found that the transmittance of CNTs counter electrode influence the performance of dye-sensitized solar cells.