• Korean Journal of Optics and Photonics
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• v.26 no.5
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• pp.275-282
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• 2015

The effective reflection coefficients for light obliquely incident upon a substrate coated with uniaxially anisotropic films and with isotropic films are derived. Multiple reflections inside anisotropic films, as well as those inside isotropic films, are properly treated. These expressions, together with the related ellipsometric expressions, can be used to find the nonuniform distribution of an uniaxially anisotropic film perpendicular to the film's surface, by approximating it as consisting of uniaxially anisotropic uniform layers and applying the conventional modeling technique for spectroscopic ellipsometry.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.41-47
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• 2012

In this paper, we proposed a new method which analyzes and eliminates errors occurring by multi-reflection of ultrasonic firing in mobile robot application. This new method allows ultrasonic sensors to fire at rates that are three times faster than those customary in conventional applications readings due to ultrasonic noise disturbance. It is possible them to collect and predict sensor data much faster than conventional methods. Furthermore, this method's capability allows mobile robot to navigate in a complex and unknown environment and to collaborate in the same environment with multiple mobile robot, even if their ultrasonic sensors operate. And it's usefulness to avoid moving obstacles by capability of rapid collecting data. Finally, we present experimental results that demonstrate the performances of the new proposed method by experiments in a multi-reflective environment.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.45-49
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• 2010

This paper presents the study on multi-beam large aperture antenna systems for a satellite payload. Multi-beam large antenna provides the universal communication and broadcasting services to personal portable terminals. The hybrid antenna composed of a large reflector and a feed array forms multi-beams. The feed cluster consists of a group of feed elements and each element should be optimized for the appropriate amplitude and phase. The optimization progress for amplitude and phase was performed by GO (Geometrical Optics) and PO (Physical Optics) method. The number of feed elements as well as the power level per element were also optimized to meet the required EIRP (Effective Isotropically Radiated Power). In conclusion, 30m-class reflector and twenty five elements for fifteen beams over Korean Peninsula were designed through the optimization process.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.150-155
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• 2013

Textured surface has been fabricated to reduce the light reflectance from the solar cells. The textured surface is very suitable for the multi-junction III-V solar cells because it can decrease the light reflectance over a large wavelength range. In this study, we have generated a textured structure on InAlP which is used for the window layer of the multi-junction III-V solar cells. Ultra-thin Pt layer (0.7 nm) has been used for wet etching mask. An array of nanosized pyramid shape formed on InAlP surface dramatically reduces the light reflectance up to 13.7% over a large wavelength range (i.e., $0.3{\sim}1.5{\mu}m$).

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.184-188
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• 2001

본 논문에서는 다중대역 피드를 위한 직교모드 변환기를 설계하였다. 직교모드 변환기의 전체적인 모양은 사각 테이퍼진 형태이고, 18-20 GHz 에서 우원 편파와 좌원편파를 발생시키기 위해 테이퍼 부분에 2개의 측면포트를 두고, 직선포트는 30-45 GHz의 광대역에서 -20dB 이하의 반사계수를 가지도록 설계하였다. 직선포트에서의 반사계수 특성을 향상시키기 위해서 측면포트에 얇은 격막을 삽입하였다. 전체적인 설계에 상용소프트웨어인 HFSS$^{R}$를 사용하였다.

• Proceedings of the KAIS Fall Conference
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• 2008.05a
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• pp.258-260
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• 2008

본 논문에서 다중경로 전파환경에서 전파특성을 연구하였다. 목표지점에서 전계의 세기는 직접파와 지면 반사파의 합으로 구성된다. 이 논문에서는 지면의 반사를 고려하여 목표물 근처 공간의 3차원 전계분포를 계산하는 프로그램을 개발하였다. 실제 목표물의 궤적에 따라 목표물의 수신기에서의 신호세기를 예측하는 3차원 모델을 개발 하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.495-498
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• 1998

수중폭발성음원인 SUS(signal underwater sound)는 수중에서의 폭발과 동시에 충격파와 기포파들이 연속적으로 발생한다. 이러한 신호는 광범위한 주파수대역을 가지고 전파거리가 길어지면서 굴절과 반사등의 다중경로 전파효과에 의한 신호의 변형까지 생긴다. (1,2,3). 본 연구에서는 deconvolution 방법을 이용하여 수신신호중에서 기포파효과를 최소화시켜 충격파의 수신기 도달시간을 파악하고, 각 충격파들의 전파경로를 추정하여 이 중 직접경로와 해저면 반사경로의 신호를 이용하여 해저면 반사계수를 계산하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1401-1411
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• 2010

In this paper, we suggested the tolerance limits of FAR(Fully Anechoic Room) using correlation factor between OATS(Open area Test Site) to measure EMI(Electromagnetic Interference) and FAR to measure EMS(Electromagnetic Susceptibility). FAR Project(SMT4-CT96-2133), CISPR/A/665/DTR, and CISPR A/665/DTR documents are analyzed and theoretical correlation factor based on the documents and theoretical equations is drawn. To obtain the experimental correlation factor, EUT(Equipment Under Test) is fabricated as well as measured at the 10 m distance OATS and in the 3 m distance FAR. Also, to suggest the tolerance limits of EUT with multi sources, radiation theory for electric and magnetic dipoles is programmed. We drew the correlation factor for EUT with multi sources through the programs. As the tolerance limits of FAR is newly defined, It can be used alternative test site for OATS to measure EMI, efficiently.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.5
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• pp.593-600
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• 2014

In this paper, Radar cross section (RCS) calculations of advanced naval vessels model with RCS reduction methods are simulated and RCS results are discussed. Especially, this paper are mainly focusing on the facts influencing on RCS, the ways minimizing RCS and material characteristics of RCS changing-rate. RCS analysis results are given for a DDG-1000 type advanced naval vessels, which show that as the elevation angle increased 10 degree, the mean RCS value increased 23.91 dBsm. Also, as the superstructure angle increased 6 degree, the mean RCS value reduced 1.27 dBsm. Finally, the radar absorbing material attachment at the front and back superstructure have been reduced 2.27 dBsm in terms of mean RCS value.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.15-25
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• 1996

This paper proposes the modified image method scheme to search the reflected points and the method to calculate the number of rays. These methods are applied to the ray tracing technique for received power and delay profile prediction in microcelular environment. With ray tracing model using these methods, we show the simulated results for various environmental structures. To demonstrate the validity of this approach, these simulated results are compared and analysed with measured results in apartment towns along the street. In addition we proposed the optimum number of multipath rays with the results in microcellular environment.