• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.407-412
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• 2000

Response surface method is employed in optimizing the acoustic performance of automotive engine-cooling axial fans. The effects of modifications in blade geometry on noise reduction are investigated. Taking the far-field noise level as the objective, a quadratic response surface is constructed utilizing D-Optimality condition as the candidate-points selection criteria. It is shown that the quadratic model exhibits an excellent fitting capability resulting in the blade design with low far-field noise level.

• Journal of Radiation Protection and Research
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• 제23권1호
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• pp.1-6
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• 1998

영광 원전 지역에 적용될 수 있는 액체 방사성 물질의 확산 모델을 개발하였다. 영광에서의 해양 확산 조건은 매우 복잡하기 때문에 수치적 모델을 적용하는 것은 매우 어렵다. 따라서 비교적 단순하면서도 신뢰성 있는 미규제 지침 1.113에서 제시한 통계적 모델을 적용하였다. 이를 통해, 발전소 운전 조건이나, 피폭 경로에 따른 희석 인자를 계산할 수 있는 컴퓨터 코드를 개발하였다. 액체 방사성 물질의 확산에 대해서, 혼합 범위에 따라 근거리 혼합 모델과 원거리 혼합 모델로 구분하여 모델을 개발하였다. 근거리 혼합 현상은 부력과 초기 운동량 및 난류에 의해 결정된다. 원거리 혼합에서는 대기 중의 구름 확산과 유사하게 가우시안푸륨 모델을 적용할 수 있다. 서로 다른 피폭 경로에 대해 물리적으로 타당한 적분을 수행함으로서, 경로에 따른 희석 인자를 구할 수 있었다. 개발된 모델을 사용하여 계산한 결과에 의하면, 현행 영광 ODCM에 사용되는 희석 인자는 상당히 과평가되어 있음을 알 수 있다.

• Earthquakes and Structures
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• 제14권5호
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• pp.399-409
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• 2018

The dynamic response and seismic damage of single-layer reticulated shells in the near field of a rupturing fault can be different from those in the far field due to the different characteristics in the ground motions. To investigate the effect, the dynamic response and seismic damage of this spatial structures subjected to two different ground motions were numerically studied by nonlinear dynamic response analysis. Firstly, twelve seismic waves with an apparent velocity pulse, including horizontal and vertical seismic waves, were selected to represent the near-fault ground motion characteristics. In contrast, twelve seismic records recorded at the same site from other or same events where the epicenter was far away from the site were employed as the far-fault ground motions. Secondly, the parametric modeling process of Kiewitt single-layer reticulated domes using the finite-element package ANSYS was described carefully. Thirdly, a nonlinear time-history response analysis was carried out for typical domes subjected to different earthquakes, followed by analyzing the dynamic response and seismic damage of this spatial structures under two different ground motions based on the maximum nodal displacements and Park-Ang index as well as dissipated energy. The results showed that this spatial structures in the near field of a rupturing fault exhibit a larger dynamic response and seismic damage than those obtained from far-fault ground motions. In addition, the results also showed that the frequency overlap between structures and ground motions has a significant influence on the dynamic response of the single-layer reticulated shells, the duration of the ground motions has little effects.

• 천문학논총
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• 제32권1호
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• pp.275-279
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• 2017

The AKARI Deep Field South (ADF-S) is a large extragalactic survey field that is covered by multiple instruments, from optical to far-IR and radio. I summarise recent results in this and related fields prompted by the release of the Herschel far-IR/submm images, including studies of cold dust in nearby galaxies, the identification of strongly lensed distant galaxies, and the use of colour selection to find candidate very high redshift sources. I conclude that the potential for significant new results from the ADF-S is very great. The addition of new wavelength bands in the future, eg. from Euclid, SKA, ALMA and elsewhere, will boost the importance of this field still further.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.106-113
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• 2002

In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used for a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted for soil. These two fields are coupled using FE-BE coupling technique In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, the dynamic response analyses of interface spring elements are performed. As a result, less spring stiffness makes the natural frequency decrease and the resonant amplitude increase.

• 대한전자공학회논문지
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• 제21권1호
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• pp.1-6
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• 1984

기하광학적 해석방법으로 입사조건에 따른 SCS(step-graded-step) 모드 스크램블러의 near field pattern, 모달 파우어 분포 및 far field pattern을 계산하고, 실험결과와 일치함을 보였다. 이로부터 SGS 모드 스크램블러에 의해 피측정 graded index 광섬유에서 stable mode launching이 이루어짐을 설명하였다. 또한 SGS 모드 스크램블러의 효과적 사용 방법으로는 입사 NA를 적게하는 것이 좋다는 것을 알았으며, 실험으로 확인하였다.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.261-265
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• 2012

IGBT(insulated gate bipolar transistor) is outstanding device for current conduction capabilities. IGBT design to control the large power switching device for power supply, converter, solar converter, electric home appliances, etc. like this IGBT device can be used in many places so to increase the efficiency of the various structures are coming. in this paper optimization design of planar type IGBT and planar field stop IGBT, and both devices have a comparative analysis and reflection of the electrical characteristics.

• 한국전자파학회논문지
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• 제9권4호
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• pp.526-534
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• 1998

The electric near-fields from a cellular phone's antenna are calculated using TLM method. The cellular phones is assumed to be a conductive box and the frequency is set to be 900 [MHz] and the radiated power is set to be 0.6 [W]. The near-fields and far-field patterns are obtained for wire antennas of 1/4 and 1/2 wavelengths. For the same radiation power, (0.6 [W]), it is found out the near-field for antennal length of λ/2 is much weaker than that for λ/4 antenna. The maximum SAR calculated in a simple head model becomes 1.4[W/kg].

• 한국음향학회:학술대회논문집
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• 한국음향학회 1996년도 제11회 수중음향학 학술발표회 논문집 11th Underwater Acoustics Symposium Proceedings
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• pp.59-62
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• 1996

A numerical study of a two-dimensional acoustic field is carride ort for a spinning vortex pair located neat a wall to investigate the effect of the wall from the spinning quadrupole source in unsteady vortical flows. Based on the known incompressible flow field, the perturbed compressible acoustic terms derived from the Euler equations are calculated. Non-reflecting boundary conditions on the free field and the solid boundary conditions are developed for a generalized curvilinear coordinates system to investigate the effect of a curced wall. It is concluded that the sound generated by the quadrupole sources of unsteady vortical flows in the presence of a flat wall or a circular cylinder can be calculated by using the source terms of hydrodynamic flow fluctuations in both near and far acoustic fields simultaneously.

• 한국해안해양공학회지
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• 제10권2호
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• pp.73-82
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• 1998

연안에서 표층 방류된 온수의 확산-이송을 모의하고자 배출구 인근의 근역에서는 반능동적 입자추적의 원리가 적용된 부작위행보모형과 원역에서는 Eulerian-Lagrangian 농도가 결합된 2차원 모형이 개발되었다. 근역에서 표층으로 부상되는 온수괴는 부력을 갖는 다수의 입자군으로 변환되어 초기 평면확산의 증가를 나타내고, 이러한 부력확산의 영향이 무작위행보의 기본식에 도입되었다. 개발된 모형의 초기평가는 단순한 지형의 해역과 실제해역에서 수행되었다. 단순해역에서는 부력이 고려되지 않는 중립입자모형의 결과에 비하여 초기 확산이 크게 나타나고, 기존 근역모형CORMIX3과 유사하나 외해측으로 확장된 성향을 보인다. 천수만에서 실제적용 결과도 배출구 근처에서 관측치에 유사한 퍼짐 효과가 나타나며 모형의 적용성이 인정된다.