• The Optical Journal
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• s.154
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• pp.33-45
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• 2014

■ 광통신용 렌즈는 광통신 시스템에 있어서 송신단과 수신단에 사용되는 하나의 부품으로 집광/발산의 결상 기능을 지니며, 광회로 부품과 광섬유 또는 수발광소자인 LD/PD와 광섬유를 효율 좋게 저손실로 접속하는 기능을 수행함. ■ 마이크로 렌즈는 마이크로 광학의 분야에 있어 광의 집광 및 평행 광으로의 변환에 빠질 수 없는 가장 기본적인 소자로서, 마이크로 렌즈의 종류로는 마이크로 볼 렌즈, 비구면 렌즈와 GRIN 렌즈가 대표적으로 있음. ■ 렌즈에 적용되는 사양으로서 렌즈의 유효 구경, 초점(focal point), 주점(principle point), 주점에서 초점까지의 거리인 초점 거리(focal length), 가상의 법선을 기준으로 빛이 입사되는 각도인 입사각, 빛이 다른 매질을 만나 반사되는 각도인 반사각, 서로 다른 매질을 빛이 통과할 때 굴절하는 굴절각 등이 있음. ■ 렌즈 모듈의 구조는 렌즈, 스페이서(spacer), 아리리스(Iris), 백링(back-ring), 바렐(Barrel)로 구성함. ■ LD 모듈에서 광원에 패브리 페로(FP)로 사용하는 것에는 볼 렌즈가, DFB 광원으로 사용하는 것으로는 비구면 렌즈가 사용하고 있음. 이를 위해 PON용에서는 G-PON의 OLT, ONU 측, GE-PON의 OLT측에는 비구면 렌즈가 사용되나 GE-PON의 ONU측에는 볼 렌즈가 주로 사용되고 있음. ■ 2012년 볼 렌즈 시장은 수량 기반으로 2011년 대비 9.7% 증가한 7,350만 개, 금액기반으로는 17.0% 증가한 3,125만$를 기록하였음. ■ 2012년 비구면 렌즈 시장은 수량 기반으로 2011년 대비 22.0% 증가한 2,220만 개, 금액 기반으로는 32.0% 증가한 8,900만$를 기록하였음. ■ 2012년 광통신용 렌즈 시장(볼 + 비구면)은 수량 기반으로 2011년 대비 12.3% 증가한 9,570만 개, 금액 기반으로는 27.7% 증가한 1억 2,063만$이었음.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.273-284
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• 1999

In order to develop star trackers for a satellite in our country we studies selection procedure of optical parameters. For logical selection of the optical parameters, we simulated the entire processes in which star lights imaged on a CCD sensor were read into and processed in an associated electronics. The simulation resulted in relations between star's magnitude and achievable pointing accuracy, from which we derived optimal optical parameters to satisfy a required pointing accuracy of a star tracker. The selected optical parameters were used in an optical system design of a star tracker with a pointing accuracy of 10 arcsec.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.2
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• pp.133-138
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• 2005

As Aspheric lenses have producted to development for disadvantage of spherical lenses, the purpose of use on aspheric lenses is in improvement of the imaging quality and decrement of the number of lenses used, they are used for lessen the mass and volume in optical science. The skills to produce optical data and the aspheric are seen as high technology today. The optical science which is composed of aspheric provides broadening view of things and high efficiency. In addition, it provides many advantages such as providing image and reducing the weight. Now, I study with techniques of processing and measuring aspheric to satisfy the necessity of increasing in aspheric data. Furthermore. I emphasize that the techniques of producing, measuring, and evaluating in the aspheric lenses have constantly developing today.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.182-187
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• 2015

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.254-259
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• 2015

On January 30, 2012 an auxiliary component of Byron Unit 2 was tripped on bus under voltage. The cause of the event was the failure of the C-phase insulator track for the Unit 2 station auxiliary transformer(SAT) revenue metering transformer. In addition to this event, other events have occurred at other plants resulting in an open-phase condition.[1] Therefore, Nuclear Regulatory Commission(NRC) has requested that not only nuclear power plant(NPP) operating company but also its Design Certification(DC) applicant have to prepare open-phase detecting system in their operating plants and design document. In this paper, various open-phase conditions are simulated in NPP using Electromagnetic Transient Program(EMTP) and Atpdraw, and open-phase condition detecting system is proposed for Main Transformer(MT), Unit Auxiliary Transformer(UAT) and SAT connected power line in NPP.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.76-82
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• 1998

As the minimum feature size of a semiconductor chip gets smaller, the inevitable distortion of patterned image by optical lithography becomes the limiting factor in the mass production of VLSI. The optical proximity correction (OPC), which corrects pattern distortion that originates from the resolution limit of optical lithography, is becoming indispensable technology. In this paper, we describe a program that corrects optical proximity effect and thus finds the optimum mask pattern with a Monte-Carlo method. The program was applied to real memory cell patterns to produce mask patterns that generate image patterns closer to object images than original mask patterns, and increase of process margin is expected, as well.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.4 s.316
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• pp.93-100
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• 2007

In this paper, a novel approach based on wavelet transform is proposed to process the scraped character which is represented on digital image. The basis idea is that the scraped character is described by its textured neighborhood, and it is decomposed into multiresolution features at different levels with its background region. The image is first decomposed into sub bands by applying Daubechies wavelets. Character features are extracted from the low frequency sub-bands by partition, FCM clustering and area-based region process. High frequency ones are activated by applying local energy density over a moving mask. Features are synthesized in order to reconstruct the original image state through inverse wavelet transform Background region is eliminated and character is extracted. The experimental results demonstrate the effectiveness of the proposed method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.8
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• pp.75-81
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• 2014

It has been widely accepted that open phase may separate one of the power lines from power supply which is mainly caused by fuse melting, malfunction for source circuit breaker, contact failure, and disconnection under normal operating conditions, and is considered a kind of failure mode during disconnection of neutral wires as well. When open phase occurs, unequal voltage between phase might happen in the unbalanced load connected each phase, and further, depending on conditions of load, malfunction by providing low voltage. Moreover, load could be burned or overheated with overvoltage, which, in turn, can be a contributor to starting fires. Accordingly, in order to clearly overcome these problems, the current study aims to introduce the theory of uninterruptible power open phase compensation device, meaning that unbalanced power automatically restores balanced power and provides continuously the power supply without blackout, and verify it through simulation and experiments.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.120-127
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• 1999

We discussed two main types-conformal and non-conformal (powered) - of holographic combiner. A theoretical model based on the Kogelnik's coupled wave theory was used to illustrate bandwidth and efficiency properties. Also we showed numerical values for the aberrations that are induced by a wavelength shift from construction to reconstruction and found optimum coordinates to reduce the chrolatic aberation of construction beams using aberration balancing techniques. The holographic combiner manufactured in conformal type with 60$^{\circ}$ incidence angle at 514.5 nm had narrow angular bandwidth (FWHM) of 4.1" and spectral bandwidth of 11.4 nm, while non-conformal one with 50$^{\circ}$, 30$^{\circ}$ incidence angle at 514.5 nm showed spectral and angular bandwidth of 10.7 nm and 5.5$^{\circ}$, respectively.vely.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.1
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• pp.57-62
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• 2019

In this paper, oneM2M based data monitoring and acquisition system is designed and implemented to measure and transmit the voltage, current, temperature, acceleration and vibration of the motor. The proposed system can detect electrical faults (overcurrent, reverse phase, phase loss, ground fault) and mechanical faults (MC counter, motor operation time, bearing and winding temperature, motor speed, insulation resistance). The system consists of sensor data collection, web server, php, database, wired/wireless communication system. The insulation resistance and the motor speed were measured, and the experimental results were similar for both the test resistance value and the reference input value.