• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.95-105
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• 2009

The flow fields around the HARTII rotor were numerically investigated using a viscous flow solver on adaptive unstructured meshes. An overset mesh and a deforming mesh technique were used to handle the blade motion including blade deflection, which was obtain from the HARTII experimental data. A solution-adaptive mesh refinement technique was also used to capture the rotor wake effectively. Comparison of the sectional normal force and pitching moment at 87% radial station between the two cases, with and without the blade deflection, showed that the blade loading is significantly affected by blade torsion. It was found that as the mesh was refined, the strength of tip vortex is better preserved, and the magnitude of high frequency blade loading, caused by blade-vortex interaction (BVI), is further magnified. It was also found that a proper time step size, which corresponds to the cell size, should be used to predict unsteady solutions accurately. In general, the numerical results in terms of the unsteady blade loading and the rotor wake show good agreement with the experimental data.

• 대한전자공학회논문지TC
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• 제39권10호
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• pp.27-37
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• 2002

본 논문에서는 주파수 영역에서 3차원 임의형태의 유전체 산란 해석을 위하여 다양한 결합 적분방정식(combined field integral equation, CFIE)의 구성을 제안한다. 서로 다른 시험 함수의 조합으로 8 가지의 CFIE를 제안하였다. 본 논문의 목적 중의 하나는 제안된 모든 CFIE가 구조물의 내부공진 주파수에서 공진문제를 극복하지 못함을 보이는 것이다. 또한 이 8가지의 CFIE는 네 개의 항으로 구성되는데, 이 중에서 하나를 무시하는 방법으로 16가지의 새로운 CFIE를 제안하였다. 수치 예로서 유전체로부터의 원거리장과 레이다 단면적(radar cross section, RCS) 계산 결과들을 보이며, 제안되는 각 CFIE의 동작 특성을 비교하여 고찰하였다.

• 천문학회보
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• 제39권2호
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• pp.83.2-83.2
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• 2014

Flare and rotational variabilities induced by stellar activity are important for studying the effect of magnetic fields on the evolution of red dwarf stars. The level and frequency of magnetic activity in these stars have a different aspect at every moment of the observations due to the effect of age-rotation relation. The use of both tracers is thus essential to have a relatively homogeneous set of stellar activity data for statistical studies. The archival light curves and imaging data of the open cluster M37 taken by MMT 6.5m telescope were used for this work. In order to achieve much more accurate photometric precisions and also to make the most efficient use of the data, the entire imaging database were re-analyzed with our new time-series photometry technique and carefully calibration procedures. Based on the new light curves, we study, for the first time, a variety of aspects of those two variabilities in red dwarfs and their relation to magnetic activity. In this talk, we present all observational evidences that support the idea that the strength of magnetic activity is closely connected with the rotation rate of a star and its evolutionary status (age-activity-rotation paradigm). In conclusion, we suggest future directions to improve our understanding of stellar activity in cool stars with photometric time-series data.

• 한국통신학회논문지
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• 제26권11B호
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• pp.1600-1606
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• 2001

공기갭과 유전체 덮개층을 갖는 이방성 매질 위의 마이크로스트립 안테나의 공진 주파수에 대해 해석하였다. 이방성 매질의 구성관계식으로부터 파수영역에서의 다이애덕 그린 함수를 유도하였고 이 결과를 퓨리에 변환을 사용하여 공간에서의 전계 적분 방정식을 수식화차였다. 갈러킨 모멘트법을 사용하여 적분 방정식을 이산화하였으며 실제 전류 밀도와 가장 유사한 정현적 함수를 기저함수로 선택하였다. 수치해석 결과의 타당성을 검증하기 위해 기존의 결과와 비교, 일치된 결과를 얻었으며 공기 갭의 두게, 패치 길이, 이방성 비의 변화에 따른 공진 주파수가 제시되고 분석되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.231-236
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• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• 한국전자파학회논문지
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• 제14권10호
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• pp.1096-1103
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• 2003

본 논문에서는 시간영역 PMCHW 적분방정식을 이용하여 3차원 유전체로부터의 전자기 과도 응답을 해석하기 위한 새로운 해법을 제안한다. 이를 위하여 공간 및 시간 시험 과정으로 분리한 갤러킨 방법을 적용한다. 3차원 임의 형태의 유전체 표면을 삼각형으로 분할한 다음, 공간에 대한 등가전류의 전개 및 시험 함수로서 삼각형 벡터 함수를 사용한다. 시간영역의 미지 계수를 라게르 함수로부터 유도된 기저함수로 근사하며, 이 함수를 시간영역의 시험함수로도 사용한다. 제안된 방법에 의하여 계산된 유전체의 등가전류 및 원거리장의 수치 결과들을 보인다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.416-419
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• 2000

A narrow slot in the broad wall of a rectangular waveguide is analysed using a Spatial Network Method[1] which takes account of the waveguide wall thickness. In essence, SNM is used to solve arbitrary shape and materials constant, derived from maxwell's equations to find the tangential electric fields on the upper and lower surfaces of the slot. In this paper, applying to the offset and length[2] which yield a zero equivalent shunt susceptance, analysing single and 4 array slot antenna. The current of the transient analysis shows each the times. Analysed result of SNM is verified by the method of moment and HFSS.

• 대한전자공학회논문지TC
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• 제38권9호
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• pp.29-39
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• 2001

공기 캡을 갖는 일축성 이방성 매질 위의 마이크로스트립 안테나에 대해 유전체 덮개층이 미치는 영향에 관하여 연구하였다. 일축성 이방성 매질의 특성을 나타내는 텐서의 구성관계식으로부터 파수영역에서의 다이에딕 그린 함수를 유도하였으며 이 결과를 푸리에 변환을 사용하여 공간에서의 전계 적분 방정식으로 수식화하였다. 갈리킨 모멘트법을 사용하여 적분 방정식을 이산화하였으며 기저함수로는 정현적 함수를 선택하였다. 수치해석 결과의 타당성을 검증하기 위해 기존의 결과와 비교, 일치된 결과를 얻었으며 공기갭의 두께, 패치 길이 그리고 덮개층의 유전율과 두께 변화에 따라 유전체 덮개층이 공진 주파수, 대역폭과 입력 임피던스에 어떤 영향을 미치는지 제시되고 분석되었다.

• 한국운동역학회지
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• 제17권4호
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• pp.157-167
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• 2007

The purpose of this study was to analyze kinematic techniques in the woman's 100m hurdle. In order to find the kinematic parameters, a 3-D video system for kinematic analysis-kwon3d 3.1(Kwon3D Motion Analysis Program Version 3.1)-was used. Eight JVC video cameras(GR-HD1KR) were used to film the performance of Lee Yeon-Kyoung at a frame rate of 60fields/s. The kinematic characteristics from the first hurdle to last hurdle were analyzed at the clearing hurdle spots such as distance, velocities, heights and angles. The real-life three-dimensional coordinates of 20 body landmarks during each phases were collected using a Direct Linear Transformation procedure. After analyzing the kinematic variables in the 100m hurdle run, the following conclusion were obtained; Lee Yeon-Kyoung had to maintain constant stride lengths between hurdles and increase takeoff distance before clearance and shorter landing distance after clearance. She also had to hit the correct takeoff point in front of the hurdle and extend the lead leg at the moment of landing in order to minimize the loss of velocity. She had to sprint between hurdles as fast as possible over 8m/s and run powerful first stride and shortened third stride preparing for the following hurdle clearances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.591-593
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• 2000

A narrow slot in the broad wall of a rectangular waveguide is analysed using a Spatial Network Method[1] which takes account of the waveguide wall thickness. In essence, SNM is used to solve arbitrary shape and materials constant, derived from maxwell's equations to find the tangential electric fields on the upper and lower surfaces of the slot. In this paper, applying to the offset and length[2] which yield a zero equivalent shunt susceptance, analysing single and 4 array slot antenna. The current of the transient analysis shows each the times. Analysed result of SNM is verified by the method of moment and HFSS.