• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.772-774
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• 2004

선택적 주의선택 알고리즘 중 색상과 밝기 지도를 만드는 부분을 실시간 처리에 적용하고, 저주파수가 주로 분포하는 영역과 물체의 움직임이 감지된 영역을 입력 영상에서 찾아내어 가중치별로 합산함으로서 실시간으로 선택적 주의를 줄 수 있는 시스템을 구현했다.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.9-18
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• 1993

Numerical wave tank is a robust tool by which the nonlinear interactions between the body and the free-surface can be treated in time-domain. In this paper, a two-dimensional numerical wave tank based on the Spectral/Boundary-Element Method is developed, and applied successfully to the study of nonlinear wave diffraction around a submerged circular cylinder. Particularly, it is shown that the high-order wave components of significant wave height are developed in the lee-side of the cylinder and that these waves result in a negative drift force on the circular cylider.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.388-397
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• 2010

A two-dimensional time-domain, potential-theory-based fully nonlinear numerical wave tank (NWT) was developed by using boundary element method and the mixed Eulerian-Lagrangian (MEL) approach for free-surface node treatment. The NWT was applied to prediction of primary wave energy conversion efficiency of a bottom-mounted oscillating water column (OWC) wave power device. The nonlinear free-surface condition inside the chamber was specially devised to represent the pneumatic pressure due to airflow velocity and viscous energy loss at the chamber entrance due to wave column motion. The newly developed NWT technique was verified through comparison with given experimental results. The maximum energy extraction was estimated with various chamber-air duct volume ratios.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.335-344
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• 2011

A curvilinear non-hydrostatic free surface model is developed to investigate nonlinear wave interactions in a circular channel. The proposed model solves the unsteady Navier-Stokes equations in a three-dimensional domain with a pressure correction method, which is one of fractional step methods. A hybrid staggered-grid layout in the vertical direction is implemented, which renders relatively simple resulting pressure equation as well as free surface closure. Numerical accuracy with respect to wave nonlinearity is tested against the fifth-order Stokes solution in a two-dimensional numerical wave tank. Numerical applications center on the evolution of nonlinear waves including diffraction and reflection affected by the curvature of side wall in a circular channel comparing with linear waves. Except for a highly nonlinear bichrmatic wave, the model's results are in good agreement with superimposed analytical solution that neglects nonlinear effects. Through the numerical simulation of the highly nonlinear bichramatic wave, the model shows its capability to investigate the evolution of nonlinear wave groups in a circular channel.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.30-31
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• 2003

원자와 빛과의 상호 작용의 결과로 원자에 결맞음이 유도될 수 있는데, 결맞음이 오래 지속될 수 있는 경우, 원자의 결맞음은 빛의 전파 및 비선형 광학 현상에 영향을 미친다. 느린 빛, 빠른 빛의 발생, 빛의 저장 및 재생, 낮은 출력을 이용한 합주파수 발생 및 4광파 혼합, 닮은 꼴 펄스의 발생 등은 빛이 결맞은 원자를 지나갈 때 나타날 수 있는 현상들이다. 빛과 원자와의 상호 작용은 슈뢰딩거 방정식이나 밀도 행렬 방정식을 풀어 기술할 수 있고, 빛의 전파는 맥스웰 방정식을 풀어 기술할 수 있으므로 결맞은 매질에서 빛의 전파를 이론적으로 연구하기 위해서는 두 방정식을 결합하여 해를 구해야 한다. (중략)

• Electrical & Electronic Materials
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• v.5 no.1
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• pp.28-42
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• 1992

본 논문에서는 ZnO 바리스터의 유전특성에 대해 검토하였다. 25~75[.deg.C]의 온도에서 1[kHz]~13[MHz]의 부파수 범위에서 LCR meter와 computer로 구성된 측정장치를 사용하여 정전용량-주파수, 및 손실계수-주파수의 관계를 측정하였다. 수학적 해석 방법에 의해 복소유전율의 실험결과로 부터 3-4개의 Debye 피크를 추출할 수 있었다. 각 피크를 .alpha., .betha., .gamma. 및 .delta.라 할 때 활성화에너지는 각각 0.35-0.48, 0.62-0.99, 0.48 및 0.33-0.41[eV]이었고, 각 피크 중 .gamma.는 공핍층에 형성된 도너준위, .alpha. 및 .delta.는 결정립 계면준위, .betha.피크는 도너이온에 의한 것으로 추정된다.

• The Journal of Natural Sciences
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• v.12 no.1
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• pp.49-59
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• 2002

Exponential decrease of saturation absorption signal was reported in pump beam spacially keeping off from probe beam. Optimum angle between pump beam and probe beam in the differential-velocity-selective saturation absorption spectroscopy was computed theoretically, $1.33^{\circ}$ in cesium atoms and $1.08^{\circ}$ in Rb 87 atoms, and was good agreement with the experimental results.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.143-150
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• 1990

A cooperative Korea-Japan investigation for the demersal fisheries resources of the East China Sea was carried out by using the training ship Oshoro Maru belong to Hokkaido University Japan, during 5-12 November, 1989. The research vessel sampled 24 stations with demersal trawls on the East China Sea continental shelf, and 96 nautical miles of track line were surveyed hydroacoustically. The echo sounder used during the survey was of a scientific type having echo integration capabilities and the computer system was programmed to obtain echo integration data for each depth stratum between the transducer and the bottom. The target strength of fish school(TS per 1kg) was estimated from the relationship between mean volume backscattering strength and catches caught by the demersal trawls. The results obtained can be summarized as follows: 1. Approximately 96 species were identified from survey catches. 2. The mean volume backscattering strength for the layer occupied by bottom trawls at 25 and 100 KHz were-63.9 dB and -67.3 dB, respectively. Then the average catch per unit time of each trawl haul was 58.8 kg/hour. 3. The mean volume backscattering strength for the entire layer between the transducer and the bottom at 25 and 100KHz were -61.9 dB and -67.0 dB, respectively. 4. The mean fish school target strength per unit weight(TS/kg) at 25 and 100 KHz were -23.6 dB/kg and -26.6 dB/kg, respectively.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.355-358
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• 2004

최근 웨이블릿 변환을 이용하여 저주파수 부대역 신호를 반복적으로 분해하고 삽입된 워터마크 비트에 따라 특정 부대역 신호에 두개의 다른 반향 중 하나를 삽입하는 반향 삽입 기법을 제안하였다. 이 기법은 오디오 신호의 주파수 특성을 고려했기 때문에 시간 영역에서의 기존의 반향 삽입 기법에 비해 비가청성(inaudibility), 워터마크의 강인성(robustness) 및 용적성(capacity)을 모두 증가시킬 수 있다. 기존의 부대역 신호 기반 반향 삽입 기법이 단일 반향 커널만을 이용하였으나, 본 논문에서는 부대역 신호에 다중 반향 커널을 이용한 반향 삽입 기법을 제안한다. 이 기법은 주관적 왜곡(perceptibility)과 SNR(signal to Noise Ratio)과 같은 객관적인 왜곡 면에서, 원본 오디오 신호의 왜곡을 줄일 수 있다. 실험 결과를 통하여 기존의 방법에 비해 제안된 방법이 SNR과 DR(Detection Rate) 모두 좋은 성능을 보여 제안된 방법의 유효성을 입증하였다.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.81-87
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• 1992

Polyethylenes were reinforced with short aramid fibers on an open roll. Fiber orientation and the anisotropy of physical property were studied using scanning electron microscopy and tensile tester, together with the melt properties from an RDS rheometer. It was found that fiber orientation was obtained in roll operation, and the anisotropy of property became greater with the increase of fiber loading. Melt viscosity measurements indicated that the viscosity increases with fiber loading, with the effect much more pronounced at low loading and low frequency.