• 한국해안·해양공학회논문집
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• 제32권3호
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• pp.161-169
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• 2020

테트라포드로 피복된 경사식방파제 상부구조물에 파가 경사 입사할 때의 파력 변화를 관찰하기 위한 수리모형실험을 수행하였다. 입사파향은 0, 15, 30, 45° 4가지로 변화시켰으며 상부구조물 전면 및 하부면에 파압계를 부착하여 수평 및 연직파력을 계측하였다. 실험을 통해 입사각과 구조물 전면이 이루는 각도가 증가할수록 수평 및 연직 파력이 모두 감소함을 확인하였다. 실험자료 분석 결과로부터 입사파향에 대한 수평 및 연직 파력 감소율 산정식을 각각 제시하였다.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1704-1713
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• 2003

Point contact film thickness in elastohydrodynamic lubrication (EHL) is analyzed by image processing method for the images from an optical interferometer with monochromatic incident light. Interference between the reflected lights both on half mirror Cr coating of glass disk and on super finished ball makes circular fringes depending on the contact conditions such as sliding velocity, applied load, viscosity-pressure characteristics and viscosity of lubricant under ambient pressure. In this situation the film thickness is regarded as the difference of optical paths between those reflected lights, which make dark and bright fringes with monochromatic incident light. The film thickness is computed by numbering the dark and bright fringe orders and the intensity (gray scale image) in each fringe regime is mapped to the corresponding film thickness. In this work, we developed a measuring technique for EHL film thickness by dividing the image patterns into two typical types under the condition of monochromatic incident light. During the image processing, the captured image is converted into digitally formatted data over the contact area without any loss of the image information of interferogram and it is also interpreted with consistency regardless of the observer's experimental experience. It is expected that the developed image processing method will provide a valuable basis to develop the image processing technique for color fringes, which is generally used for the measurement of relatively thin films in higher resolution.

• 한국전자파학회논문지
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• 제26권5호
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• pp.499-505
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• 2015

전자기 공진 현상을 이용한 무선전력전송 시스템에 대한 조사량 평가 시 전기장의 고려 여부를 검토하였다. 인체로 인가되는 전기장과 자기장의 상대적인 크기가 조사량 평가 시에 중요한 지표가 되기 때문에, 이를 검토하기 위해 자기 다이폴 인근의 다양한 전자기장의 크기를 갖는 곳에 구형의 간이 인체 모델을 위치시키고, 구 모델 내부로 유도되는 전기장의 값을 이론과 수치해석을 통하여 구하고 비교하였다. 그 결과, 전기장을 무시할 수 없는 영역이 존재함을 확인하였으며, 이는 무선전력전송의 조사량 평가 시 외부 전기장에 대한 고려가 필요함을 알 수 있었다.

• Journal of Positioning, Navigation, and Timing
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• 제5권3호
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• pp.131-136
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• 2016

The present paper shows that beamforming algorithm such as Minimum Variance Distortionless Response (MVDR) based on array antenna signal processing can have not only anti-jamming but also anti-spoofing characteristics. A beam pattern due to the beamforming algorithm strengthens received signal power as it is formed in the incident direction of desired signal. During the process, the effect of unnecessary signals such as spoofing signals can be reduced because the beam pattern reduces received signal power in the incident directions excluding the beam pattern-directed direction. In order to analyze the anti-spoofing effect due to the beamforming algorithm, a software-based simulation environment was configured. An arbitrary error was applied between incident direction of Global Positioning System (GPS) satellite signal and steering vector direction of the beamforming algorithm to analyze the received signal power and required conditions were provided to see the anti-spoofing effect due to the beamforming algorithm. The used antenna was 7-element planar circular array and beam patterns were formed through the MVDR algorithm.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.199-203
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• 2006

This paper presents an ASER (Accelerated Soft Error Rate) integral model. The model is based on the facts that the generated EHP/s(electron hole pairs) are diminished after some residual range of the incident alpha particle, where residual range is a function of the incident angle and the capping layer thickness over the semiconductor junction. The ASER is influenced by the flux of the alpha particles, the junction area ratio, the alpha particle incident angle when the critical charge is same as the collected charge, and the sizes of the alpha source and the chip. The model was examined with 8M static RAM samples. The measured ASER data showed good agreement with the calculated values using the model. The ASER decreased exponentially with respect to the operational voltage. As the capping layer thickness increases up to $16{\mu}m$, the ASER increases, and after that thickness, the ASER decreases. The ASER increased as the depth of BNW increased from $0{\mu}m\;to\;4{\mu}m$. and then saturated. The ASER decreased as the node capacitance increased from 2fF to 5fF.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.887-903
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• 2016

This study analyses the seismic response of a three-dimensional (3-D) rigid massless square foundation resting or embedded in a viscoelastic soil limited by rigid bedrock. The foundation is subjected to harmonic oblique seismic waves P, SV, SH and R. The key step is the characterization of the soil-foundation interaction by computing the impedance matrix and the input motion matrix. A 3-D frequency boundary element method (BEM) in conjunction with the thin layer method (TLM) is adapted for the seismic analysis of the foundation. The dynamic response of the rigid foundation is solved from the wave equations by taking into account the soil-foundation interaction. The solution is formulated using the frequency BEM with the Green's function obtained from the TLM. This approach has been applied to analyze the effect of soilstructure interaction on the seismic response of the foundation as a function of the kind of incident waves, the angles of incident waves, the wave's frequencies and the embedding of foundation. The parametric results show that the non-vertical incident waves, the embedment of foundation, and the wave's frequencies have important impact on the dynamic response of rigid foundations.

• 전자공학회논문지D
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• 제35D권3호
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• pp.91-97
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• 1998

In a LiNbO$_{3}$ crystal, optical noise is caused by the inhomogeneity of crystal inside if the excess energy is incident on the crystal. In this paper, we experiemnt the influence of optical noise when it is applied for beam diffraction and optical information storage. And it is proposed the energy threshold level which is not affected by optical noise in Fe-LiNbO$_{3}$ crystal(0.02Wt.% doped, 10mm*10mm*10mm). The optical noise of crystal weremeasured as a function of the incident beam intensity(10mw, 5mw, 1mw, 0.5mw), direction in incident(orthogonal, left rotation, right rotation) and wavelength(514.5nm, 632.8nm).

• 한국산업정보학회논문지
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• 제4권1호
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• pp.102-109
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• 1999

본 논문에서는 접지평면위에 2개의 유전체 층을 가지는 완전도체 격자구조에서의 전자파 산란문제를 간단한 방수치해석 방법으로 잘 알려진 PMM방법을 적용하여 입사각에 따라 수치해석하였다. 산란전자계는 Floquet 모드 함수의 급수로 전개하였다. 경계조건은 미지의 계수를 구하기 위하여 적용하였고, 도체의 경계조건은 접선성분의 전계와 스트립 위의 전류와의 관계를 위해 적용하였다. 입사각이 수직일 때 비유전율이 증가함에 따라 기하광학적 반사전력의 변하는 최소점은 스트립 폭이 높은 값으로 이동한다는 것은 주목되며, 이때 수직입사시 대부분의 전력은 다른 각도의 방향으로 산란된다.

• 한국ITS학회 논문지
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• 제22권6호
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• pp.114-123
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• 2023

컴퓨터 비전(Computer Vision: CV) 기술 발전으로 폐쇄회로 TV(Closed-Circuit television: CCTV)와 같은 영상 센서로 돌발상황을 검지하고 있다. 그러나 현재 이러한 기술은 대부분 고정식 영상 센서를 기반으로 한다. 따라서 고정식 장비의 영상 범위가 닿지 않는 음영지역의 돌발상황 검지에는 한계가 존재해왔다. 최근 엣지 컴퓨팅(Edge-computing) 기술의 발전으로 이동식 영상정보의 실시간 분석이 가능해졌다. 본 연구는 차량 내 설치된 이동식 영상 센서(dashboard camera 혹은 dash cam)에 컴퓨터 비전 기술을 도입하여 고속도로에서 실시간으로 돌발상황 검지 가능성에 대해 평가하는 것이 목적이다. 이를 위해 한국도로공사 순찰차량에 장착된 dash cam에서 수집된 4,388건의 스틸 프레임 데이터 기반으로 학습데이터를 구축하였으며, YOLO(You Only Look Once) 알고리즘을 활용하여 분석하였다. 분석 결과 객체 모두 예측 정밀도가 70% 이상으로 나타났고, 교통사고는 약 85%의 정밀도를 보였다. 또한 mAP(mean Average Precision)의 경우 0.769로 나타났고, 객체별 AP(Average Precision)를 보면 교통사고가 0.904로 가장 높게 나타났고, 낙하물이 0.629로 가장 낮게 나타났다.

• 한국소음진동공학회논문집
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• 제16권7호
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• pp.729-738
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• 2006

Knowledge of acoustic transmission loss of acoustic window material has a great importance for the sonar performance in ship. The purpose of this study was to investigate the measurement and analysis method for the acoustic transmission loss of the acoustic window materials for sonar dome. The measurement and analysis were carried out in water with GRP material. Transmission losses were calculated based on integrated direct and transmitted signals. The experimental setup enabled to vary the angle of incidence. Thus the transmission loss data could be expressed as the function of frequency and angle of rotation. In this paper, diffraction effect of incident angle, size of specimen with test material, transmission analysis method and multiple waves as incident acoustic signal were discussed.