• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.30-35
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• 2013

In order to increase cell efficiency in crystalline silicon solar cell, reduction of light reflection is one of the essential problem. Until now silicon wafer was textured by wet etching process which has random patterns along crystal orientation. In this study, high aspect ratio patterns are manufactured by nano imprint process and reflectance could be minimized under 1%. After that, screen printed solar cell was fabricated on the textured wafer and I-V characteristics was measured by solar simulator. Consequently cell efficiency of solar cell fabricated using the wafer textured by nano imprint process increased 1.15% than reference solar cell textured by wet etching. Internal quantum efficiency was increased in the range of IR wave length but decreased in the UV wavelength. In spite of improved result, optimization between nano imprinted pattern and solar cell process should be followed.

• The Journal of Information Systems
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• v.8 no.2
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• pp.91-110
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• 1999

Recently, searching agent systems to help purchase of products between business and customer have been actively studied in Electronic Commerce(EC). However, the most of comparative searching agent systems are only provided customers with searching results by the keyword-based search, and is not support the efficient decision models to be selected products considering the customer's requirements. This paper proposes the decision agent system applied decision model as well as searching functions based on the keyword-input to be selected useful products in EC. The proposed decision agent system is consist of the user interface, provider interface, decision model. Especially, as the example of the decision model, this paper is designed and implemented the prototype of decision agent system which is normalized the searching data and value of customer's preference weight as to each attribute, and orderly provided customers with computed results. This agent system is also carried out sensitive analysis according to the reflection ratio of the each attribute.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.10
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• pp.572-581
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• 2000

When the manipulator consisting of high ratio gear reducers at its joints is used as the slave manipulator in teleoperated systems, its dynamic characteristics is much slower than that of the master manipulator and it is likely to encounter the saturation in the input magnitude. The control input saturation generates an windup phenomenon that the system stability and position tracking performance of the slave manipulator are to be deteriorated. This paper proposes an force reflecting control scheme and its design method which compensates the control input saturation with absolute stability. The proposed scheme is shown to give a stable force reflection while compensating for control input saturation effectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.263-263
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• 2012

본 연구는 실리콘 표면에 형성된 pyramid 구조의 크기와 각도, aspect ratio에 따른 반사도, 흡수율 최적화에 관한 연구이다. Atlas device simulation을 이용하여 표면에 형성된 pyramid의 각도는 $54.74^{\circ}$에서 $71.56^{\circ}$ 가변하였으며 pyramid height은 5에서 $20{\mu}m$ 크기로 가변하여 반사도와 흡수율 변화와 상관관계를 분석하였다. 특히 표면 반사도 감소와 실리콘 기판의 흡수율 증가에 가장 큰 영향을 미치는 표면구조의 인자는 pyramid 각도로 나타났으며, 또한 표면의 pyramid 각도 증가에 따라 표면적도 증가하는 결과를 얻을 수 있었다. 본 연구의 표면 구조의 형상에 따른 반사도와 흡수율 최적화 및 표면적 증가에 대한 결과를 태양전지에 적용할 시 단락전류 향상을 통한 효율 향상을 기대할 수 있을 것이다.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.93-94
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• 2000

In this work, we proposed a reflective antiferroelectric liquid crystal display (AFLCD) using a half-wave cell whose tilt angle is $22.5^{\circ}$. To check the validity of our design, we fabricated a reflective half-wave AFLC cell of which tilt angle is $24.9^{\circ}$, and measured viewing angle dependent reflectance and VIS reflection spectra. In the results, the half-wave AFLC cell in the reflective configuration exhibits high brightness, high contrast ratio of 20:1.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.11a
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• pp.90-93
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• 2001

In the present work, ultrasonic testing method has been developed to evaluate adhesive layers in rocket motor case assembly for the reliability of the rocket. The main objective of the present work was to find debonding between steel and rubber layers. The relationship between adhesion ratio and reflected ultrasonic amplitude was calculated by considering reflection coefficient at the interface between steel and rubber layers. It was found that the higher amplitude of ultrasound is reflected for the debonding area, and shown good agreements with experimental results. The ultrasonic C-scan images offers good implements for the determination of debonding area. The nondestructive testing results were compared with the micrography of destruective testing. As results, ultrasonic testing could be utilized for the evaluation of adhesive layer in the rocket motor case assembly.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.116-119
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• 1993

In this paper, we implemented a pulse wave type oximeter system that continuously measure the of oxyhemoglobin saturation of the arterial blood(SaO2) and pulse rate with non-invasively. We use the transmission type and reflection type transducer for comparison the percentage of hemoglobin oxgen saturation. The light Iron the two kind of LEDs is transmitted through the tissue, then received by a single photodiode with alternatively. By the phase sensitive detection circuit, the output of the photodiode is separated in to red and near infrared signal. We calculated a ratio of light transmittance between two kind of LEDs, and then, it is applied to the oxgen saturation coefficent calculation formular.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.200-201
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• 2008

태양전지 제작 시 반사방지막(Anti-reflection Coating)이 태양전지 효율에 미치는 영향을 알아보기 위한 실험으로 최적의 가스비를 알아보기 위하여 Plasma Enhanced Chemical Vapor Deposition(PECVD)를 이용한 Silicon nitride 증착 실험이다. SiH4 가스를 45 sccm으로 고정시킨 상태에서 NH3를 25,45,60,90,135 sccm으로 가변하여 Carrier Lifetime과 Refractive index를 측정하였다. PECVD의 조건은 기판온도 $450^{\circ}C$, Chamber 압력 1 Torr, 증착두께 $1000\AA$으로 고정하였다. 증착 후 500, 600, 700, $800^{\circ}C$로 열처리를 하고나서 Carrier Lifetime을 측정하여 열처리에 대한 효과도 알아보았다.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.787-790
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• 2009

High contrast red, green and blue organic light-emitting diodes were fabricated using inorganic metal multi layer composed of thin Al, KCl and thick Al and then were compared to optical and electrical characteristics with the attached polarizer and conventional OLEDs. Ambient light reflection of OLED using inorganic metal layer, polarizer and conventional metal layer were 29.2, 31.1 and 82.5% respectively. Optical characteristics of OLEDs using inorganic metal layer were max luminescence of 13040 cd/m2 and luminous efficiency of 2.12 cd/A at 8V whereas OLEDs using polarizer has 8456 cd/m2 and 1.43 cd/A at 8V each. OLEDs including inorganic metal multi layers show significant technical advantages in achieving high performance of OLED display with improved contrast ratio of 251:1, specifically in Red OLED.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.198-203
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• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.