• 제목/요약/키워드: 모멘트방정식

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Effect of finite conductive image planes on PCB radiation (유한 도전성 영상 평면이 PCB 전자파 복사에 미치는 영향 분석)

  • Kim, Jin-Suk;Cho, Kwang-Yun;Kim, Nam
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.23 no.4
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    • pp.836-845
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    • 1998
  • In this ppaer, the confguration of multi-layers of the image planes surrounding the current trace of inite width has been considered, and the shielding performance of image planes is analyzed with the parameters of the width and conductivity of the planes, and the distance between the current trace and the planes. The induced current distributions on the image planes have bgeen calculated by solving a set of electric field integral equations by the method of moments. To cacluate the current distribution on the planes effectively, a new method for dividing integral intervals is proposed.

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A Study on the Analysis of Hydrologic Similarity of the Catchment Response(I) (유역응답의 수문학적 상사성해석에 관한 연구(I))

  • 조홍제;이상배
    • Water for future
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    • v.23 no.4
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    • pp.421-434
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    • 1990
  • The problems of hydrologic similarity among river basins was analyzed by a geomorphologic response model using Hortons*s ordering scheme. The Nash model was used for deriving the geomorphologic response function, and for the optimization of the responsefunction, imcomplete gamma function andRosso*s regression equation were used. The application of this method was tested on some observed flood data of Pyungchang river basin and Wi Stream basin and Bocheong stream, and predictions of hydrologic response were compared with that of the Moment method. The results show that the proposed model and dimensionless instantaneous unit hydrograph can be used for the runoff analysis of an ungauged basin and the analysis of hydrologic similarity.

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Scattering of Coaxial Waveguide with Periodic Axial Slots Using Characteristic Mode Theory : TE Case (특성모드 이론을 이용한 주기적인 축방향 슬롯이 있는 동축선로 도파관 구조의 산란특성 : TE의 경우)

  • 윤리호;조영기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.8 no.6
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    • pp.629-635
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    • 1997
  • The theory of characteristic modes for coaxial waveguide with periodic axial slots is used to derive the weighted eigenvalue equation for calculating the characteristic values and the characteristic currents. Once the characteristic values and the characteristic currents are obtained, the important quantities such as the equivalent magnetic current, radiation patterns, and RCS are determined. Numerical results of the equivalent magnetic currents, radiation patterns, and RCS are compared with those obtained by use of the method of moments. A fairly good correspondence is observed between them.

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Numerical Computation of the Backscattering Coefficients of Rice Fields Using the Impedance Boundary Condition, Moment Method and Monte Carlo Method (임피던스 경계 조건, 모멘트 법과 몬테 카를로 방법을 이용한 논의 산란계수 수치적 계산과 측정 데이터와의 비교)

  • Hong, Jin-Young;Oh, Yi-Sok
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.18 no.7
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    • pp.819-827
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    • 2007
  • A numerical algorithm for estimating precise backscattering coefficients of rice fields is proposed and its accuracy is verified in this paper. After a bunch of rice plants above water surface is modeled with a bunch of randomly oriented lossy dielectric bodies above an impedance surface and the equivalent volume currents of the lossy dielectrics are computed using the moment method. Then, the scattered fields of a rice field with many bunches are computed with a Monte Carlo method, and consequently the backscattering coefficient of the rice field is computed for various incidence angles and polarizations. Finally, the backscattering coefficient of a rice field is measured at 1.85 GHz using an R-band scatterometer system, and these experimental data are used to verify the numerical algorithm proposed in this paper. It is found that the numerical computation results agree well with the measurement data.

Direct Solution of Structural Rigid Frames with Sidesway (절점이동(節點移動)이 있는 구조강절(構造剛節) 뼈대의 직접해법(直接解法))

  • Yang, Chang Hyun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.3
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    • pp.91-105
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    • 1992
  • For the analysis of multistory frames with sidesway, no adequate procedures can be found in the classical methods of structural analysis. Even well-known procedures such as the slope-deflection method and the moment distribution method may not be effective tools since those methods require a multiple of computational labor and/or yield results of approximate values. In this study, a direct method is developed and proposed for the analysis of multistory frames with sidesway, which is due to the lateral loads, asymmetry of the structure itself, or asymmetry of vertical loadings. The proposed method is to obtain simple forms of equations derived by a mathematical formulation of the moment distribution procedure combined with successive correction concept. Numerical illustrations show that the results obtained by the proposed method agree well with those by rigorous ones. Undoubtedly, this newly developed method can be applied more easily for the analysis of structural frames without joint translation as well as continuous beams.

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3D Optimal Layout Design of Satellite Equipment (위성 구성품의 3차원 최적 배치 설계)

  • Yeom, Seung-Yong;Kim, Hong-Rae;Chang, Young-Keun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.10
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    • pp.875-887
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    • 2015
  • The optimal layout design is used in the development of various areas of industry. In the field of space systems, components must be placed properly in the limited space of spacecraft by considering mechanical, thermal and electrical interfaces. When applying optimal layout design, a proper, even ideal placement of components is possible in the limited space of a satellite platform. Through the optimal placement design, the minimized moment of inertia enhances efficient attitude control, rapid maneuver and mission performance of the satellite. This paper proposes 3D optimal layout design that minimizes the spacecraft's moment of inertia and effect of thermal dissipation between inner components as well as interference between inner components based on a cubic-structure satellite platform. This study proposes the new genetic algorithm for 3D optimal layout design of the satellite platform.

Impact Analysis of Oleo-pneumatic Nose Strut for Light Aircraft (소형항공기 올레오 타입 전방착륙장치 충격해석)

  • Park, Ill-Kyung;Choi, Sun-Woo;Jang, Jae-Won
    • Aerospace Engineering and Technology
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    • v.6 no.1
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    • pp.19-28
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    • 2007
  • In this study, a nonlinear 2 degree of freedom mathematical model has been developed for impact analysis of the nose landing gear of a light aircraft which is composed of an wheel & tire, an Oleo-pneumatic shock strut and the castering wheel fork for the differential braking steering, and then the response of impact is computed using a numerical method. The mathematical model of a nose landing gear contains nonlinear characteristics which are an impact load - deflection property of a tire and internally frictional forces between an inner surface of an upper cylinder and a bearing of a lower rod due to side forces like the declined angle of strut, the moment due to an wheel fork, the side drag due to a steering and it is computed using the 4th-order Runge-Kutta method. The comparison process between analytical results and experimental results of the other proven nose landing gear is carried out to verify the mathematical model.

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Aperture Cut-off Filter for Reduction of Electromagnetic Field Penetration through a Slot in Conducting Screens (도체평판의 슬롯 침투 전자파 저감을 위한 개구면 차단필터)

  • Kim, Ki-Chai
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.12
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    • pp.1201-1211
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    • 2014
  • The purpose of this paper is to present the aperture cut-off filter for reduction of electromagnetic field penetration through a slot in conducting screen. The reduction characteristics of electric field penetration by the aperture cut-off filter are considered. In order to establish the concept of the aperture cut-off filter, the integral equation on the slot aperture field distribution is derived and solved by method of moments, and the reduction characteristics of penetration electric fields for the incident plane wave are calculated. The numerical results showed that the aperture cut-off filter for reduction of electric field penetration through the slot can be realized. To check the validity of the concept of an aperture cut-off filter and the theoretical analysis, the calculated electric field penetration of the metallic wall with narrow slot were compared with the experimental results.

Vibration Control of the Continuous System Under White Noise Disturbance (백색잡음가진을 받는 연속체의 진동제어)

  • Paik, Jong-Han;Heo, Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1994.10a
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    • pp.116-120
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    • 1994
  • 최근 항공우주 및 생산자동화 분야의 급격한 발달에 따라 정밀도와 효율성을 향상시키기 위해 저중량, 고강도 구조물이 요구된다. 그러나 경량화 추세로 인해 수반되는 구조물의 유연성 증가로 외력에 대한 구조응답의 진폭이 커지고 구조물의 피로 수명이 단축되어 매우 위험한 상황에 이를 수 있다. 이런 바람직하지 않은 진동현상을 제어하기 위해 여러 제어이론을 응용한 진동억제시스템의 연구가 활발하며, 신소재인 압전재료의 개발로 새로운 방향이 제시되고 있다. 압전재료는 유연한 구조물에 부착되어 압전재료의 수축, 팽창 운동에 의해 발생된 에너지를 부착된 구조물에서의 제어력으로 사용되어, 진동 혹은 자세 및 형상 제어에 활용되고 있다. 압전재료에 대한 연구로는 Crawley, de Luis3가 보의 표면 혹은 내부에 압전세라믹을 부착하여 액튜에이터로 사용하는 경우 집중모멘트를 가하는 역할을 함을 밝혔고, Hanagud, obal은 압전재료를 센서와 액튜에이터로 사용해 복합재료 보에 대한 최적 진동제어 알고리즘을 개발, 그 성능에 대한 효과를 조사하였고 임의의 위치에 부착된 센서 및 액튜에이터를 고려한 복합재료 보의 운동방정식을 유한요소법을 이용 유도하였으며 변위율 피드백(rate feedback)과 모달피드백(modal feedback) 제어기를 적용하여 진동제어 효과를 고찰하였다. 그리고 Tomas, James, Hubbard는 압전필름을 액튜에이터로 사용해 복합재료 보에 Liapunov 제어기와 변위율 피드백 제어기를 사용하여 능동감쇠기를 설계하였고, Lee, Chaing, Sullivan은 압전필름을 센서와 액튜에이터로 사용해 평판에 변위율 피드백 제어기를 적용한 능동감쇠기를 설계하고 실험적으로 수행하였다. Base가 백색잡음가진을 지속적으로 받을 때 보끝의 움직임이 최소가 되도록 제어하고자 연구를 수행 중인 바 그 결과로소 본 논문에서는 적용시켰고 F-P-K 방정식을 이용해 확률영역으로 변환하여 LQR 제어기와 pole allocation 제어기를 시스템에 적용시켜 우수한 특성을 갖음을 제어 시뮬레이션의 결과를 통해 입증하였다.

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Free Vibrations of Timoshenko Beam with Elastomeric Bearings at Two Far Ends (양단이 탄성받침으로 지지된 Timoshenko 보의 자유진동)

  • Lee, Byoung Koo;Lee, Tae Eun;Park, Chang Eun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.3A
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    • pp.181-187
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    • 2011
  • This paper deals with free vibrations of the Timoshenko beam supported by two elastomeric bearings at two far ends. The ordinary differential equation governing free vibrations of such beam is derived, in which both effects of rotatory inertia and shear deformation are included as the Timoshenko beam theory. Also, boundary conditions of the free end are derived based on the Timoshenko beam theory. The ordinary differential equation is solved by the numerical methods for calculating natural frequencies and mode shapes. Both effects of the rotatory inertia and shear deformation on natural frequencies are extensively discussed. Also, relationships between natural frequencies and slenderness ratio, foundation modulus and bearing length are presented. Typical mode shapes of bending moment and shear force as well as deflection are given in figures which show the positions of maximum amplitudes and nodal points.