• Title/Summary/Keyword: 모멘트방정식

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4-Element Circular Array Dipole Antennas with Beam Steering (지향성 절환 4소자 원형 배열 타이폴 안테나)

  • 이종녕;양규식;김기채
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.4
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    • pp.386-392
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    • 2002
  • This paper presents a basic characteristics of 4-element circular array dipole antennas for 4-sector beam steering. The coupled integral equations for the unknown current distributions on dipole elements are derived and solved by applying Galerkin's method of moments. The parasitic elements have been used to increase the directional gain and the beam is steered electronically either by sswitching between the parasitic elements or switching the position of the active element. The parasitic elements are switched short-circuited or open-circuited as required to steer a directional beam. In order to verify the theoretical analysis, the radiation pattern was compared with experiments.

Design and Near-Field Analysis of X-Band Linear/Circular Polarizer (X-밴드 선형/원형 편파 변환기의 설계 및 근거리장 해석)

  • 서창용;정명수;박동철
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.8
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    • pp.801-808
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    • 2004
  • In this paper, we proposed the grating parallel plate waveguide structure for converting a linearly polarized wave to a circularly polarized wave. For the design of the polarizer, the moment method and Floquet's theorem are applied under two assumptions that the incident wave is a plane wave and the structure is infinitely periodic. In order for the more precise design, we performed the near-field analysis for the finite polarizer structure using MATLAB. By comparing with the measured results obtained by the near-field arrangement, we verified the correctness of our near-field analysis. By taking the ideal assumptions considered in the initial design procedure into account, newly designed modified dimensions for the polarizer was suggested which give improved performance.

Maximum Coupling Phenomena through a Slit Fed by a Flanged Parallel-Plate Waveguide with a Conducting Strip (플랜지된 평행 평판 도파관으로 급전된 슬릿을 통한 도체 스트립과의 최대 결합 현상)

  • Lee Jong-Ig;Cho Young-Ki
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.6 s.109
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    • pp.501-510
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    • 2006
  • In this paper, the electromagnetic coupling through a slit in a flanged parallel-plate waveguide with a conducting strip is studied. The coupled integro-differential equations for the electric field over the slit and the induced current over the strip are derived and solved by use of the method of moments. The characteristics of some types of maximum coupling phenomena are investigated from the examinations of the variations of the equivalent slit admittance and the coupled power against various parameters such as the location of conducting strip, operating frequency, and strip length.

MoM Forward Solver for Medical Microwave Imaging (의용 전자파 영상을 위한 모멘트법 순방향 해석 알고리즘)

  • Kim, Bo-Ra;Lee, Taek-Kyung;Son, Seong-Ho;Jeon, Soon-Ik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.8
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    • pp.797-805
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    • 2009
  • In this paper, we developed MoM(Moment of Method) forward solver to implement the inverse scattering by using BIM(Born Iterative Method) for the detection of cancer in human body Especially, we adopted two-dimensional breast structure to analyze electromagnetic scattered phenomena. For the two-dimensional scattering structure, the integral equations is solved with MoM employing two-dimensional Green's function. Also, calculated results are compared with the measured results obtained from breast cancer detecting equipment.

Real-Time CoM/ZMP Trajectory Transformation Method for Humanoid Robots Considering Structure Characteristics (구조 특성을 반영한 인간형 로봇을 위한 실시간 CoM/ZMP 궤적 변환 방법)

  • Hong, Seok-Min
    • Journal of Advanced Navigation Technology
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    • v.21 no.1
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    • pp.132-137
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    • 2017
  • This paper proposes a transformation method of the zero moment point (ZMP) and the center of mass (CoM) from one walking pattern to other patterns by considering the structure of a robot or walking situations in real time. In general, a humanoid robot has own structure characteristics like height and mass. The structure characteristics make the given CoM/ZMP walking pattern of one human or one humanoid robot to be difficult to apply to other robot directly. For this purpose, we analyze the characteristics of walking patterns according to the step length, duration of walking support phase and the CoM height by using the cart-table model as the simple humanoid robot model. A transformation equation is derived from the analyzation and it is verified with simulation.

Modeling and Simulation of a Ship with Anti-Rolling Devices in Waves (자세제어장비를 장착한 선박의 파랑중 운동 모델링 및 시뮬레이션)

  • 윤현규;이경중;이창민
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.04a
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    • pp.285-290
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    • 2004
  • Wave exciting force and moment generate the motions of a ship in waves. Since ship motion exerts the negative influences on a crew's operability, the safety of cargos, passenger's comfort, etc, the anti-rolling devices may be required to reduce such motion. In this paper, the dynamics of the anti-rolling devices such as passive and active moving weight stabilizer and anti-rolling tank, and fin stabilizer are mathematically modeled. While the effect of the motion of the anti-rolling device on a ship was taken into consideration in roll mode only in the past, the 6 DOF coupled equations of motion between a ship and the anti-rolling devices are constituted. Finally the motion of a ship with anti-rolling devices in waves is simulated through the developed simulation program.

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Longitudinal Stability of a Wing-In-Ground Effect Craft (해면효과익선의 종방향 안정성에 대한 연구)

  • Ho-Hwan Chun;Chong-Hee Chang;Kwang-Jun Paik
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.60-70
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    • 1999
  • The longitudinal stability characteristics of a Wing-In-Ground Effect Craft are quite different from that of the conventional airplane due to the existence of force and moment derivatives with regard to height. This stability characteristics plays a great role in designing a safe and efficient WIG due to its potential danger in sea surface proximity. The static and dynamic stability criteria are derived from the motion equations of WIG in the framework of small disturbance theory and discussed in the paper. The static and dynamic stability analyses of a 20-passenger WIG are conducted based on the wind tunnel test data and the dynamic motion behaviors are investigated for the change of the design parameters. Finally, the flying quality of the 20-passenger WIG is analysed at the cruising condition according to the military regulations.

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A analysis of Thin-Straight Monopole antenna on a conducting box Using the Wire-Grid Method (Wire-Grid 방법을 이용한 도체 상자에 부착된 선형 모노폴 안테나 해석)

  • 이승엽;김경재;이영훈;허선종;박한규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.11
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    • pp.1669-1676
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    • 1993
  • In this paper, a thin-straight monopole antenna attached to a conducting box is analyzed using a moment method with the pocklington integral expression for the exact Green's function. A modeling of a conducting box is based on a Wire-Grid method for an efficient calculation procedure. A system of linear equation is obtained using the piecewise sinusoidal basis function. And a Junction basis function is enforcing to represent the physical current on the edge of the conducting box. Especially, the junction basis functions are overlapped for the current continuity preserving on the vertexes. Numerical results are obtained for the current distribution on the unified antenna/conducting box system, input impedance and radiation pattern. The results are compared with the known data.

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Reduction Characteristics of Electromagnetic Fields in Cavity by Lossy Dielectric Materials (손실 유전체를 이용한 공동 내부의 전자계 저감 특성)

  • 정광현;김기채
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.9
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    • pp.950-954
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    • 2003
  • This paper presents the delivered power and reflection coefficient in metallic shielding enclosure excited by the interior source, which are evaluated with the method of moments, and describes a method for reducing the radiation of electromagnetic fields in the cavity by putting lossy dielectric material in one inside wall. In this paper we introduce carbon polystyrene-foam as lossy dielectric material and observe it's effects of reduction when the thickness and permittivity of lossy dielectric material are changed. The results show that the reduction of the electromagnetic radiation can be achieved by controlling the amount of carbon in lossy dielectric material. The theoretical analysis is verified by the measured delivered power.

Theoretical Curve of Normalized Site Attenuation for Forced Resonant Type EMI Dipole Antennas (강제 공진형 EMI 다이폴 안테나에 대한 정규화 시험장 감쇠량 이론곡선)

  • 김기채
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.5
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    • pp.467-472
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    • 2004
  • This paper presents the normalized site attenuation characteristics for frequencies below 80 ㎒ using forced resonant type EMI dipole antennas. The coupled integral equations for unknown current distribution are solved by the Galerkin's method of moments with piecewise sinusoidal functions. The results show that the forced resonant type EMI dipole antenna for frequencies below 80 ㎒ can be used effectively for the measuring normalized site attenuation. The calculated normalized site attenuation curves for the forced resonant type EMI dipole antenna are useful in determining the suitability of open area test sites.