• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1656-1659
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• 2008

The reflective type color filter for the liquid crystal displays (LCD) was produced using cholesteric liquid crystal monomers whose phase is characterized by the unique optical features of selective reflection. Periodic micrometer scale hemi-spherical photoresist (PR) patterns were formed on glass substrates by thermal reflow method after photolithography. Cholesteric color filter films for red, green and blue light reflections were then produced and the viewing angle dependence was investigated and compared with that of reflected light on the non-patterned substrates.

• 대한전자공학회논문지SD
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• 제37권7호
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• pp.36-42
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• 2000

광 폴리머(photopolymer)에 의한 편광 회전과 제작된 격자에서 나타나는 회절효율의 불안정을 분석하였으며, 특히 반사형 광 폴리머의 내부 복굴절(birefringence)에 의해 회절효율의 변화가 발생함을 밝혔다. 광 폴리머를 지지하고 있는 Mylar 기판(base sheet)은 고분자 물질로, 가공 중에 발생한 연신에 의해 복굴절이 발생하여 밤의 편광 상태를 회전시킴으로써 격자의 회절효율을 불안정하게 만드는 원인이 된다. Mylar 기판을 통과하는 빔의 편광 상태를 감광성이 없는 He-Ne 레이저를 사용하여 유리판 위에 접촉된 상태에서 방향을 조절하여 광원의 편광 상태와 평행하게 고정시킬 수 있었으며, 이로 인해 매우 안정적인 회절효율을 갖는 회절격자를 제작할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1216-1219
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• 1994

A reflection type SEED from LP-MOCVD grown InGaAs/GaAs ESQW structures, with 5% In fraction, has been fabricated and its basic characteristics were investigated. Its intrinsic region consists of 50 pairs of alternating $100{\AA}$ $In_{0.05}Ga_{0.95}As$ barrier and $100{\AA}$ GaAs layers. And a multilayer reflector stack of $Al_{0.12}Ga_{0.88}As(641{\AA})-/AlAs(774{\AA})$ was vertically integrated below the p-i-n structures. The device processing includes the mesa etching, insulator deposition, indium metallization, and thermal alloy for Ohmic contact. Photocurrent spectrum measurement showed the exciton absorption peak at 905nm and availability as a optical switching device. This device showed a contrast ratio of 2:1 by the reflectance spectrum measurement.

• 한국항해학회지
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• 제22권4호
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• pp.51-57
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• 1998

According to the rapid development of the electric industry, the demand of the frequency allocation and the usage of electromagnetic wave are increased due to automation of modem society. Electromagnetic wave absorbers for anechoic chamber are needed to broaden the effective frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the effective frequency bandwidth by the way of forming air layer(practically in urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 400 MHz in bandwidth. In this paper, a broadband electromagnetic wave absorber are designed, which has the reflection characteristics less than -20 dB from 30 MHz to 8,000 MHz in the bandwidth. A super broadband electromagnetic wave absorber is achieved by inserting square Ferrite Cylinders Type with the thickness less than 23.5 mm and with the frequency band from 30 MHz to 8,000 MHz under the above tolerance limits. The purpose of this research is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell and also a wall material for preventing TV ghost, etc.

• 한국해안해양공학회지
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• 제4권4호
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• pp.243-249
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• 1992

혼성방파제의 무공 및 유공 케이슨의 수리특성을 비교하기 위하여 파고 및 주기가 다른 여러 규칙파를 대상으로 수리실험을 실시하였다. 반사율, 전달률, 케이슨 전면에서의 쳐올림 높이 등 수리특성 면에서 모두 유공케이슨이 무공케이슨보다 유리한 것으로 나타났으며, 본 실험 결과가 기존의 이론식 또는 경험식들과 대체로 잘 일치함을 보였다. 특히, 유공케이슨의 반사율은 유수실 내에서의 공진현상과 밀접한 관계가 있어서 유수실의 폭이 유수실 내에서의 파장의 약 1/4 정도가 될 때 반사율이 최소가 됨을 알 수 있었다.

• 한국전자파학회논문지
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• 제11권8호
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• pp.1363-1375
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• 2000

접지된 유전체 슬랩 위에 주기적으로 스트립이 놓여 있는 격자구조에 대한 전자파 산란 특성을 TM편파의 경우에 대하여 반사격자(reflection grating)관점과 누설파안테나(leaky wave antenna)관점에서 조사하였다. 수치해석 결과로 Bragg blazing 현상을 두가지 형태(공진형과 비공진형)로 구분하였으며 그 특성(복소전파상수, 산란특성, 전류밀도분포)에 대하여 논의하였다. 특히, 본 연구구조의 TE 및 TM편파 경우에서 확인한 Bragg blazing 현상에 관하여 상세히 기술하였다.

• 한국정보통신학회논문지
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• 제3권1호
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• pp.43-50
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• 1999

Electromagnetic wave absorbers for anechoic chamber are needed to broaden the useful frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer. Therefore, an air layer is formed absorber between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 450 MHz in frequency band, far narrower than the aimed bandwidth. The purpose of this paper is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for prevention of TV ghost, etc. Accordingly, in this paper, a broadened electromagnetic wave absorber is designed, which has the reflection characteristics less than -20 dB from 30 MHz to 5,430 or 8,000 MHz in the bandwidth. Then we will design a super broadband electromagnetic wave absorber by inserting square Ferrite Cylinders Type with the thickness less than 23.5 m in three-layed type and with the frequency band from 30 MHz to 5,430-8,000 MHz under the above tolerance limits.

• Journal of Forest and Environmental Science
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• 제39권4호
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• pp.254-260
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• 2023

A sensor system has been developed that uses an ultrasonic sensor to detect the downhill slope on the side of a forest road and prevents a vehicle-type forest machine from rolling down a mountainside. A specular reflection of ultrasonic wave might cause severe issues in measuring distances to targets. By investigating the installation angle of the sensor to minimize the negative effects of specular reflection, the installation angle of lateral monitoring ultrasonic sensor could be determined based on the width of road shoulder. Obstacles such as small rocks or piece of log in a forest road may cause the forest machine to be overturned while the machine riding over due to excessive its posture change. It was determined that the laser sensor could be a part of a sensor system capable of specifying the location and size of small obstacles. Not only this sensor system including ultrasonic and laser sensors can issue a warning of dangerous sections to drivers in forest forwarders currently in use, but also it can be used as a driving safety sensor in autonomous forest machine or remote-control forest machine in the future.

• 한국광학회지
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• 제15권5호
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• pp.415-422
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• 2004

교량과 각종 건물을 비롯한 대형 토목 구조물에서 발생하는 수 mm의 변위를 한 개의 광섬유로 간편하게 측정하기 위하여 광커넥터에서 반사가 굽힘 손실에 의하여 변하는 현상을 이용한 새로운 다중화된 광섬유 변위센서를 제안하고 실험하였다. 한 쌍의 광커넥터 양끝에서 반사광의 신호차이가 두 광커넥터 사이에서 발생한 굽힘 변위에 의해서 달라지는 것을 Optical Time Domain Reflectometer로 측정하여 선형으로 그 변화가 측정되는 변위센서를 만들고, 이 센서 4개를 직렬형으로 배열하여 여러 지점의 변위를 동사에 측정이 가능한 다중화 센서 시스템을 구성하고 실험하였다. 그 결과 이 변위센서를 이용하면 4개 지점에서 각각 최대 6 mm까지의 변위를 6%의 오차범위 내에서 0.9942의 선형성을 가지고 변위를 측정할 수 있음을 확인하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1399-1406
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• 2011

As a result of the examination analyzed loop type of Detecting the Broken Rail Monitoring System as a part of prevention of train derailment, installed in the Seoul Metro No. 2 subway line 98.51m section which is Samsung to Seolleung, we found that it is possible to detect crack location(Thermit welding: 48.18m) within the margin of error of ${\pm}1m$ accurately As analysis of the first day, third day, fifty day, and seventh day periodically, we found that Fresnel reflection happened where the crack location 48.18m. However other 3 branches show loss by bending of optical cable(spread reflection from the outside impact).