• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.508-511
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• 2002

By defining a power distribution ratio (PDR) and coupling efficiency (CE) amenable to the rigorous analytical solutions of newly developed rigorous modal transmission-line theory (MTLT), we explicitly analyze the power coupling characteristics of TE modes propagating in GADCs. The numerical results reveal that the incident power is optimally coupled into the desired guiding channel if the powers of rigorous modes excited at the input boundary of grating-assisted coupler are equally partitioned.

• Smart Structures and Systems
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• 제28권6호
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• pp.827-838
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• 2021

The dynamic displacement is considered to be an important indicator of structural safety, and becomes an indispensable part of Structural Health Monitoring (SHM) system for high-speed railway bridges. This paper proposes an indirect strain based dynamic displacement reconstruction methodology for high-speed railway box girders. For the typical box girders under eccentric train load, the plane section assumption and elementary beam theory is no longer applicable due to the bend-torsion coupling effects. The monitored strain was decoupled into bend and torsion induced strain, pre-trained multi-output support vector regression (M-SVR) model was employed for such decoupling process considering the sensor layout cost and reconstruction accuracy. The decoupled strained based displacement could be reconstructed respectively using box girder plate element analysis and mode superposition principle. For the transformation modal matrix has a significant impact on the reconstructed displacement accuracy, the modal order would be optimized using particle swarm algorithm (PSO), aiming to minimize the ill conditioned degree of transformation modal matrix and the displacement reconstruction error. Numerical simulation and dynamic load testing results show that the reconstructed displacement was in good agreement with the simulated or measured results, which verifies the validity and accuracy of the algorithm proposed in this paper.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.568-571
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• 1997

The overall aim of this paper is to determine coupling loss factor using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one directional power flow between two sub structures. Using these conditions, it is possible to find the coupling loss factor equation. The comparison between theory of power transmission on conjunction and above equation, show a good agreement in simple beam structure. To check the effectiveness of above equation, it was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.266-271
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• 2009

A modeling method for the modal analysis of a multi-packet blade system having a crack undergoing rotational motion is presented in this paper. Each blade is assumed as a slender cantilever beam. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. Hybrid deformation variables are employed to derive the equations of motion. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters related to the angular speed, the depth and location of a crack on the modal characteristics of the system are investigated with some numerical examples.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.966-969
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• 1999

Using modal transmission-line theory (MTLT), we evaluate the power coupling of optical directional coupler composed by two parallel guiding slabs. The numerical results reveal that maximum power transfer occurs at a novel wavelength λ$_{opt}$, in which the excitation ratio of supermodes at input boundary is equal to each other, and it is generally different from minimum gap λ$_{min}$.in/.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.126-130
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• 2003

The optical power transfer of TM modes in grating-assisted directional couplers (GADCs) with three-guiding channels is rigorously evaluated by defining a novel coupling efficiency amenable to the rigorous analytical solutions of modal transmission-line theory (MTLT). The results reveal that the incident power is sensitively partitioned through three output channels in terms of such grating parameters as the period, the duty cycle, and wavelength.

• 한국인터넷방송통신학회논문지
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• 제11권3호
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• pp.47-52
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• 2011

세 채널로 구성된 나노 크기의 플라즈마 방향성 결합기가 모드 결합효과와 립형 전송구조를 사용하여 설계되었다. 종방향 모드 전송선로 해석법을 이용하여 방향성 결합기에서 전파하는 빛의 전파특성과 설계특성들을 분석하였다. 전력분배기로 동작하는 플라즈마 방향성 결합기는 약 200~250 nm의 전송 폭을 갖는 나노 크기로 설계하였다. 최적의 전력분배율을 얻기 위하여 중심 채널의 폭 변화에 따른 전송 모드들의 굴절률을 분석하였다. 결국, 하향 채널에서 입사된 광 신호를 각 채널을 통하여 출력하는 나노 크기의 플라즈마 방향성 결합기가 설계되었다.

• 전자공학회논문지A
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• 제31A권5호
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• pp.85-93
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• 1994

We have studied the effect of channel and/or spacing chirpings on the near field and near field intensity patterns, modal gains and radiation angles of 6 supermodes in the index-guided laser arrays with 6 channels, on the basis of the coupled mode theory. The spacings between channels can be indenpendent parameters for control of the radiation angle. It is found that an asymmetrically v channel-chirped array has both a smaller radiation angle and better supermode discrimination characteristics than a uniform array. Comparing two approaches for enhancing modal stability in point of supermode discrimination characteristics, approach I which increases the coupling cofficient between the outer-most waveguides at each end of an otherwise uniform array, has superior discrimination characteristics to the approach II which increases the propagation constant for the end elements with the same coupling between neighbor elements. Approach III which has a narrower spacing between the outer-most waveguides at one end and a wider channel width of the outer-most waveguide at another end, gets a narrower radiation angle than the approach I and good supermode discrimination characteristics by applying optimized gain profiles.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.6-15
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• 2008

This paper deals with the aeroelastic instability of vibrating multiple blade rows under aerodynamic coupling with each other. A model composed of three blade rows, e.g., rotor-stator-rotor, where blades of the two rotor cascades are simultaneously vibrating, is considered. The displacement of a blade vibrating under aerodynamic force is expanded in a modal series with the natural mode shape functions, and the modal amplitudes are treated as the generalized coordinates. The generalized mass matrix and the generalized stiffness matrix are formulated on the basis of the finite element concept. The generalized aerodynamic force on a vibrating blade consists of the component induced by the motion of the blade itself and those induced not only by vibrations of other blades of the same cascade but also vibrations of blades in another cascade. To evaluate the aerodynamic forces, the unsteady lifting surface theory for the model of three blade rows is applied. The so-called k method is applied to determine the critical flutter conditions. A numerical study has been conducted. The flutter boundaries are compared with those for a single blade row. It is shown that the effect of the aerodynamic blade row coupling substantially modifies the critical flutter conditions.

• 한국광학회지
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• 제18권3호
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• pp.190-195
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• 2007

광 평면 유전체 기판 위에 형성된 금속격자구조의 누설특성을 이용한 새로운 광 결합용 필터를 제안하였고, Bragg 조건들을 모드 전송선로 이론을 사용하여 정확하게 분석하였다. 수치해석 결과, 유전체격자구조로 구성된 기존의 DFB는 전송 모드들의 피드백특성에 기인한 차단대역을 형성하지만 금속격자구조는 누설파특성에 기인한 차단대역을 형성하는 것으로 나타났다. 결국, 누설파 필터특성을 적용한 광 결합용 필터는 LD나 광섬유와 같은 광통신용 소자들과 집적이 가능함을 보였다.