• 대한전자공학회논문지
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• 제25권3호
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• pp.343-351
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• 1988

Planar optical waveguides are fabricated on a Y-cut LiNbO3 single crystal substrate by Ti indiffusion method. From data measured by the bright M-line spectroscopy, refractive index profiles are reconstructed by WKB approximation method. Then, single strip, X-crossing strip, and Y-brinch strip optical waveguides are fabricated on X-cut LiNbO3 single crystal substrate, with waveguide patterns made by the laser beam direct writing method. And their near-field intensity profiles are observed after coupling the light to the waveguide edges.

• 한국통신학회논문지
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• 제22권7호
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• pp.1459-1467
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• 1997

The current on the thin planar structure as an element of the transversely fed electromagnetically coupled(EMC) microstrip dipole array antenna is obtained by using the integral forms of the finite difference time domain(FDTD) method. This method was applied to calculating the optimum current distribution (Doplh-Tchebyscheff distribution) of each dipole element on the feed line as a function of their offset positions for the narrow main beam width and the side beam level below -20 dB. The current on each dipole substitutes for the electric and magnetic current densities on the virtual surface of the FDTD calculation to express the far field intensity, the calculation time and the computer memeory can be reduced to about 80% and 1.3 Mbyte, respectively. The calculated radiation patterns are compared to the measured values and these are in good agreement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1880-1884
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• 2004

To analyze the fluid flow and thermal characteristics in a nanoscale system, the planar Poiseuille flow of a Lennar-Jones liquid through parallel plates formed by fixed atoms is studied using nonequilibrium molecular dynamics simulations. The role of important simulation parameters such as the channel width, the magnitude of external field, the temperatures of the top and bottom plates, and the interaction potential parameter between fluid and wall atoms, which affect flow patterns and heat transfer rate inside the channel, are investigated. Under the various simulation conditions, interesting phenomena deviated from the continuum predictions have found.

• 센서학회지
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• 제21권2호
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• pp.96-102
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• 2012

This paper addresses photometric distortion problems of a compact 3D scanning sensor which is composed of a micro-size and inexpensive camera-projector system. Recently, many micro-size cameras and projectors are available. However, erroneous 3D scanning results may arise due to the poor and nonlinear photometric properties of the sensors. This paper solves two inherent photometric distortions of the sensors. First, the response functions of both the camera and projector are derived from the least squares solutions of passive and active calibration, respectively. Second, vignetting correction of the vision camera is done by using a conventional method, however the projector vignetting is corrected by using the planar homography between the image planes of the projector and camera, respectively. Experimental results show that the proposed technique enhances the linear properties of the phase patterns that are generated by the sensor.

• Applied Science and Convergence Technology
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• 제26권4호
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• pp.74-78
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• 2017

The discharge characteristics of the radio frequency (RF) surface dielectric barrier discharge have been simulated for the investigation of the ratio of the ion transit time to the RF period. From one-dimensional particle-in-cell (PIC) simulation for a planar dielectric barrier discharge (DBD), it was observed that the high-frequency driving voltage confines the ions in the plasma because of a shorter RF period than the ion transit time. For two-dimensional surface dielectric barrier discharges, a fluid simulation is performed to investigate the characteristics of RF discharges from 1 MHz to 40 MHz. The ratio of the peak density to the average density decreases with the increasing frequency, and the spatiotemporal discharge patterns change abruptly with the change in the ratio of ion transit time to the RF period.

• 한국공간구조학회논문집
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• 제19권1호
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• pp.93-100
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• 2019

There has been considerable recent interest in deep learning techniques for structural analysis and design. However, despite newer algorithms and more precise methods have been developed in the field of computer science, the recent effective deep learning techniques have not been applied to the damage detection topics. In this study, we have explored the structural damage detection method of truss structures using the state-of-the-art deep learning techniques. The deep neural networks are used to train knowledge of the patterns in the response of the undamaged and the damaged structures. A 31-bar planar truss are considered to show the capabilities of the deep learning techniques for identifying the single or multiple-structural damage. The frequency responses and the elasticity moduli of individual elements are used as input and output datasets, respectively. In all considered cases, the neural network can assess damage conditions with very good accuracy.

• 한국전자파학회논문지
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• 제25권4호
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• pp.387-392
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• 2014

본 논문에서는 USB Dongle에 적용 가능하고 Wibro(2.3~2.4 GHz), Wi-Fi(2.4~2.5 GHz), LTE7(2.5~2.7 GHz) 대역을 지원하는 광대역 안테나 설계 기법을 제안한다. 제안된 안테나는 PIFA(Planar Inverted-F Antenna) 구조를 기본으로 설계되었고, 리액티브 소자를 이용하여 임피던스 조절이 가능하고, 급전 구조와 방사체 간의 커플링을 조절하여 광대역을 실현하였다. 그 결과, 유전율이 4.4인 FR-4 PCB에서 $15{\times}5$ mm의 협소한 공간에서 안테나의 대역폭은 반사계수 -10 dB 기준으로 약 1 GHz 대역폭을 실현했다. 측정된 반사 손실, 대역폭과 방사 패턴은 시뮬레이션 값과 잘 일치하였다.

• Spatial Information Research
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• 제6권1호
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• pp.77-90
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• 1998

자연적이거나 인위적인 여러 요인의 복합적인 상호작용에 의해 지표는 계속 변화해간다. 자연재해는 생태계의 다양한 군집이 서로 상호작용을 하는데 결정적 영향을 미치는 요소로 이런 변화의 직접적인 원인이 되는 특정 사건의 발생과정이나 공간적 분포에 대한 연구는 환경과 자원관리 측면에서 중요하다. 본 논문에서는 지표변화에 영향을 미치는 자연화재의 경우를 중심으로 공간적 분포를 모형화하는 방법론을 설명하였다. 자연화재는 주로 번개에 의해 발생되어 몇 주에 결쳐 수만 킬로미터의 지역을 태우면서 새롭고 다양한 서식지를 만들어 가는 주된 자연재해중의 하나로 생태계관리차원에서 연구되고 있다. 오스트리아 빅토리아사막을 예로 이곳에서의 자연화재 발생지역을 20년동안의 원격탐사자료(MSS data)로부터 추출하여 이를 바탕으로 자연화재발생에 대한 공간적 모형을 개발하였고 모형에 입각한 시뮬레이션 방법을 논의하였다. 화재발생과정은 불규칙적으로 분포된 공간상의 point pattern에 의해 특징지어질 수 있는데 이의 모형화를 위해서 Nonhomogeneous Planar Poissin Process가 이용되었다.

• 대기
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• 제26권3호
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• pp.473-482
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• 2016

An accurate determination of turbulent fluxes over an urban area is a challenging task due to its morphological diversity and associated flow complexity. In this study, an eddy covariance (EC) method is applied over a highly heterogeneous urban area in a small city (Gongju), South Korea to investigate the quantitative influence of 'coordinate tilt' in determining the turbulent fluxes of sensible heat, latent heat, momentum, and carbon dioxide mass. Two widely-used coordinate transform methods are adopted and applied to eight directional sections centered on the site to analyze a 1-year period EC measurement obtained from the urban site: double rotation (DR) and planar fit (PF) transform. The results show that mean streamline planes determined by the PF method are distinguished from the sections, representing morphological heterogeneity of the site. The sectional pitch angles determined by the DR method also compare well with those in the PF method. Both the PF and DR methods show large variabilities in the determined streamline planes at each directional section, implying that flow patterns may form in a complicate way due to the surface heterogeneity. Resulting relative differences of the turbulent fluxes, defined by $(F_{DR}-F_{PF})/F_{DR}$, are found on average +13% in sensible heat flux, +21% in latent heat flux, +37% in momentum flux, and +26% in carbon dioxide mass flux, which are larger values than those reported previously for fairly homogeneous natural sites. The fractional differences depend significantly on wind direction, showing larger differences in northerly winds at the measurement site. It is also found that the relative fractional differences are negatively correlated with the mean wind speed at both stable/unstable atmospheric conditions. These results imply that EC turbulent fluxes determined over heterogeneous urban areas should be carefully interpreted with considering the uncertainty due to 'coordinate tilt' effect in their applications.

• 마이크로전자및패키징학회지
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• 제20권3호
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• pp.19-22
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• 2013

고속, 대용량 정보 전송 수요가 급격하게 증가함에 따라 대량생산 및 고효율의 PLC형 집적 광소자의 연구가 증가하고 있다. 본 논문에서는 광소자와 광섬유가 수동 정렬이 가능하도록 일체형 정렬 구조를 제안하였다. 일체형 구조의 광소자는 기본적으로 1채널의 입력부의 광신호를 2채널의 출력부를 통해 분리하는 광분배기 구조이다. 본 연구에서 제안된 일체형 구조의 제작은 롤투롤 공정 기술을 이용하여 제작하고 그 특성을 평가하였다. 롤투롤 공정 기술은 광소자의 제작에 들어가는 시간을 절감하고 연속생산이 가능한 방법이다. 제작된 광소자의 광특성은 1550 nm의 광원을 이용하여 약3.9 dB의 삽입손실과 0.2 dB의 채널 균일도를 나타내었다.