• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.763-766
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• 2002

A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.772-777
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• 2002

A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surfaces on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.

• 한국전자파학회지:전자파기술
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• 제3권1호
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• pp.20-27
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• 1992

$\lambda$/2 다이폴 안테나 3개판 x,y,z축상에 서로 직교되도록 배열하여 각 소자의 수신 출력을 합성하므로써 등방성 패턴 안테나가 실현되었다. 각 소자는 H20MHz-895MHz익 서례 주파수 대역에서 임피먼스 정합플 양호하게 하고, 소자간의 상호 결합 효과를 최소로하기 위하여 슬리브 형태의 $\lambda$/2 다이폴 안테나를 사용하였다. 설계된 등방성 패턴 얀테나로 부터 복사된 충 전계의 세기는 원방계에서 각 촉상의 다이폴에 의해 발생 되는 Magnetic Vector Potential을 이용하여 계산하였다. 계산결과, 총 전계의 세기는 원점으포 부터의 거리에는 반비례하였고, 패턴상수 차이는 2.1dB이하이었다. 또한, x,y,z 축상에 배열된 안테나에서 수산된 합성전계의 편차는 2.8dB이하로 이론적 계산치와 O.7dB 정도의 차이가 있었다.

• 지구물리
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• 제3권2호
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• pp.113-126
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• 2000

난지도 매립장의 안정화에 따른 지질환경 변화를 조사하기 위하여 탐사가 가능한 제 2 매립장 상부와 한강변에 연한 매립지의 기저지역에서 중력, 자력, 쌍극자-쌍극자, 자연전위 탐사를 수행하였다. 제 2 매립장 상부에서 수행한 중력과 자력 탐사 결과를 4 년전의 선행연구 결과와 비교하면 매립장 중앙 부분에서 밀도구배가 작아지고 복잡한 양상을 보였던 자력이상 분포가 많이 단순해진 것으로 나타난다. 이는 매립지의 안정화과정에서 침하와 복토작업이 반복되면서 매립물의 다짐작용이 순조롭게 진행되고 있는 것으로 보인다. 제 1 매립장 차수벽 밖에서 실시한 쌍극자-쌍극자 전기탐사와 자연전위탐사 결과에는 제 1 매립장 주위의 불량한 탐사환경에 의한 영향이 많이 나타난다. 제 2 매립장의 차수벽 안과 밖에서 실시한 쌍극자-쌍극자 전기탐사 결과를 비교하면 차수벽이 침출수를 어느 정도 차단하는 효과를 볼 수 있다. 제 2 매립장의 상부와 사면에서 수행한 자연전위탐사에서는 특별한 자연전위 이상은 나타나지 않으나, 하부의 차수벽 내부에서 수행한 자연전위 탐사 결과에는 침출수를 모으는 집수정의 영향이 크게 나타난다.

• 대한기계학회논문집B
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• 제21권10호
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• pp.1284-1293
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• 1997

The electrostatic effect on particle deposition onto a heated, Horizontal free-standing wafer surface was investigated numerically. The deposition mechanisms considered were convection, Brownian and turbulent diffusion, sedimentation, thermophoresis and electrostatic force. The electric charge on particle needed to calculate the electrostatic migration velocity induced by the local electric field was assumed to be the Boltzmann equilibrium charge. The electrostatic forces acted upon the particle included the Coulombic, image, dielectrophoretic and dipole-dipole forces based on the assumption that the particle and wafer surface are conducting. The electric potential distribution needed to calculate the local electric field around the wafer was calculated from the Laplace equation. The averaged and local deposition velocities were obtained for a temperature difference of 0-10 K and an applied voltage of 0-1000 v.The numerical results were then compared with those of the present suggested approximate model and the available experimental data. The comparison showed relatively good agreement between them.

• ETRI Journal
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• 제17권3호
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• pp.45-63
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• 1995

This paper proposes an algorithm to improve the correlation between giga-hertz transverse electromagnetic (GTEM) cell and open area test site (OATS). It is based on the dipole modeling process of an unknown source object in a GTEM cell and on the evaluation of the approximate far field equations correlated with measured GTEM powers at output port of the GTEM cell. In this algorithm, the relative phase differences between dipole moments play an important part in modeling the test object as a set of dipoles and offer stable calculation of emission values. The radiated emission test using this algorithm requires fifteen orientations of equipment under test, but the increased orientations as compared with the previous method have little effect on the time needed for testing. Radiation from a notebook computer has been tested for statistical analysis of the correlation between GTEM data and OATS data. The emission test results of the notebook computer show that the mean, the standard deviation, and the correlation coefficient are -0.62, 1.99, and +0.85, respectively. These figures indicate that this algorithm provides improved accuracy in the measurement of electromagnetic emissions over the previous method.

• 한국광학회지
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• 제14권1호
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• pp.103-106
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• 2003

쌍극자들로 이루어진 이준위계의 해밀토니안이 주어질 때 이 계가 만족시키는 미시적인 양자 Langevin방정식을 유도하고, 이 방정식을 거시적인 구간 내에서 평균 함으로써 거시 양자 Langevin방정식을 유도하고 국소장 효과가 양자적으로 어떻게 표현되는 지를 살펴본다.

• 센서학회지
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• 제31권4호
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• pp.194-213
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• 2022

This study comprehensively reviewed four types of integrated-optic electric-field sensors based on titanium diffused lithium-niobate waveguides: symmetric and asymmetric Mach-Zehnder interferometers, 1×2 directional couplers, and Y-fed balanced-bridge Mach-Zehnder interferometers. First, we briefly explain the crystal properties and electro-optic effect of lithium niobate and the waveguide fabrication process. We theoretically analyzed the key parameters and operating principles of each sensor and antennas. We also describe and compare the design, simulation, implementation, and performance tests: dc and ac characteristics, frequency response, dynamic range, and sensitivity. The experimental results revealed that the sensitivity of the sensor based on the Y-fed balanced bridge Mach-Zehnder interferometer (YBB-MZI) was higher than that of the other types of sensors.

• 대한기계학회논문집B
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• 제27권6호
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• pp.701-713
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• 2003

The BEM is a highly efficient method in the sense of economical computation. However, boundary integration is not easy for the complex geometry and moving surface, e.g. a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element according to their acoustic characteristics. In this study, an axial fan is assumed to have unsteady loading noise as a dominant source. Dipole sources can be modeled to solve the FW-H equation. Acoustic field is then computed by determining Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it. The optimal shape and the location of Kirchhoff surface are discussed by comparing with experimental data acquired in an anechoic chamber.

• 한국정보전자통신기술학회논문지
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• 제2권1호
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• pp.65-72
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• 2009

기지국 배열안테나의 근역장 프로빙을 통해 원역장 성능을 평가하기 위해 반사판을 갖는 다이폴 배열 안테나와 프로브 사이 높이에 따른 상호 간의 영향을 분석하였다. 기본 개념은 기지국 배열 안테나의 입력단들과 프로브의 입력 port P 에 대한 근역장에서의 상호 높이를 변화시키며 S 파라미터 측정값을 분석하여 상호결합 효과가 가장 적으면서 프로빙 효율이 높은 위치를 결정하는 것이다. 그리고 여기서 얻어진 높이는 기지국 배열안테나의 정밀한 원역장 성능을 구하기 위한 근역장 프로빙 시스템 설계에 적용 가능할 것이다.