• Title/Summary/Keyword: Coupled-mode theory

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Free vibration analysis of moderately thick rectangular laminated composite plates with arbitrary boundary conditions

  • Naserian-Nik, A.M.;Tahani, M.
    • Structural Engineering and Mechanics
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    • v.35 no.2
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    • pp.217-240
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    • 2010
  • A semi-analytical method is presented for accurately prediction of the free vibration behavior of generally laminated composite plates with arbitrary boundary conditions. The method employs the technique of separation of spatial variables within Hamilton's principle to obtain the equations of motion, including two systems of coupled ordinary homogeneous differential equations. Subsequently, by applying the laminate constitutive relations into the resulting equations two sets of coupled ordinary differential equations with constant coefficients, in terms of displacements, are achieved. The obtained differential equations are solved for the natural frequencies and corresponding mode shapes, with the use of the exact state-space approach. The formulation is exploited in the framework of the first-order shear deformation theory to incorporate the effects of transverse shear deformation and rotary inertia. The efficiency and accuracy of the present method are demonstrated by obtaining solutions to a wide range of problems and comparing them with finite element analysis and previously published results.

Design of a Novel Lumped Element Backward Directional Coupler Based on Parallel Coupled-Line Theory (평행 결합선로 이론에 근거한 새로운 집중 소자형 방향성 결합기 해석 및 설계)

  • 송택영;이상현;김영태;천창율;박준석
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2002.11a
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    • pp.157-160
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    • 2002
  • In this paper, a novel lumped equivalent circuit for a conventional parallel directional coupler is proposed. The equivalent circuit and design formula for the presented lumped element coupler is derived based on the even-and odd-mode properties of a parallel-coupled line. By using the derived design formula, we have designed the 3㏈ and 10㏈ lumped element directional couplers at the center frequency of 100Mhz. Furthermore, a chip type directional coupler has been designed to fabricate with multilayer configurations by employing the Low Temperature CofiredCeramic (LTCC) process. Designed chip-type directional coupler has a 10㏈-coupling value at the center frequency of 2㎓. Excellent agreements between simulations and measurements on the designed directional couplers show the validity of this paper

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Bending-Torsional Vibration Characteristics of Large Structure Influenced by Coupling Effects (연성효과에 의한 대형 구조물의 굽힘-비틀림 진동특성)

  • 송창용;손충열;송재영
    • Journal of KSNVE
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    • v.6 no.4
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    • pp.431-438
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    • 1996
  • The channel type structure which has large openings is frail with respect to torsional strength, and the horizontal-torsional motion is highly coupled, because of the large difference between the centroil and the shear center. Also, a discontinuous boundary phase is came from tansition section between the opened section and the closed section. To analyze the Bending- Torsional coupled mode parameters for the channel type structure, the Transfer Matrix Method was used. Comparing the result of F.D.M.T.M.M yields good results in relatively low frequency region.

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A Study on the Adjusting Fine Method of Tap-off for CATV Transmitting Circuits Using Coupled-Line Theory (결합선로이론을 이용한 CATV 전송회로용 Tap off의 미조정방법에 관한 연구)

  • 김동일;민경식;정세모
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.6
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    • pp.26-33
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    • 1994
  • Much time and labor has been conventionally paid for fine adjustment of circuit elements by experience to improve the characteristics of Tap-off for CATV systems. To solve the problem, in this paper, the relations between the even- and odd-mode impedance. Z$_{oe}$ and Z$_{oo}$ of symmetrical 4-port coupled-line directional coupler and power dividing characteristics of Tap-off for CATV system have been derived. After the coupling, the reflectivity and the isolation are represented by Z$_{oe}$ and Z$_{oo}$ only, the fine adjustment of all S-parameters can be performed by controling the elements of Z$_{oe}$ and Z$_{oo}$ only. Furthermore, the validity of the new fine adjustment method proposed here has been confirmed by experiments.

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Approximate Analysis of Shear Wall-Frame Structure For Seismic Design (전단벽-골조 시스템의 내진설계를 위한 근사해석법)

  • Yoo, Suk-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.99-106
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    • 2019
  • A wall-frame structure resists horizontal load by the interaction between the flexural mode of the shear wall and the shear mode of the frame, which implies that the frame deflects only by reverse bending of the columns and girders, and that the columns are axially rigid. However, as the height of frame increases the shear mode of frame changes to flexural mode, which is due to the extension and shortening of the columns. An approximate hand method for estimating horizontal deflection and member forces in high-rise shear wall-frame structures subjected to horizontal loading is presented. The method is developed from the continuous medium theory for coupled walls and expressed in non-dimensional structural parameters. It accounts for bending deformations in all individual members as well as axial deformations in the columns. The deformations calculated from the presented approximate method and matrix analysis by computer program are compared. The presented approximate method is more accurate for the taller structures.

Vibration Analysis of Smart Embedded Shear Deformable Nonhomogeneous Piezoelectric Nanoscale Beams based on Nonlocal Elasticity Theory

  • Ebrahimi, Farzad;Barati, Mohammad Reza;Zenkour, Ashraf M.
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.2
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    • pp.255-269
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    • 2017
  • Free vibration analysis is presented for a simply-supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen's nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher order shear deformation beam theory where coupled equations obtained using Hamilton's principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.

Forward and backward whirling of a spinning nanotube nano-rotor assuming gyroscopic effects

  • Ouakad, Hassen M.;Sedighi, Hamid M.;Al-Qahtani, Hussain M.
    • Advances in nano research
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    • v.8 no.3
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    • pp.245-254
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    • 2020
  • This work examines the fundamental vibrational characteristics of a spinning CNT-based nano-rotor assuming a nonlocal elasticity Euler-Bernoulli beam theory. The rotary inertia, gyroscopic, and rotor mass unbalance effects are all taken into consideration in the beam model. Assuming a nonlocal theory, two coupled 6th-order partial differential equations governing the vibration of the rotating SWCNT are first derived. In order to acquire the natural frequencies and dynamic response of the nano-rotor system, the nonlinear equations of motion are numerically solved. The nano-rotor system frequency spectrum is shown to exhibit two distinct frequencies: one positive and one negative. The positive frequency is known as to represent the forward whirling mode, whereas the negative characterizes the backward mode. First, the results obtained within the framework of this numerical study are compared with few existing data (i.e., molecular dynamics) and showed an overall acceptable agreement. Then, a thorough and detailed parametric study is carried out to study the effect of several parameters on the nano-rotor frequencies such as: the nanotube radius, the input angular velocity and the small scale parameters. It is shown that the vibration characteristics of a spinning SWCNT are significantly influenced when these parameters are changed.

Novel Polarization Condition of Optical Polarized Beamsplitter with Misaligned Input Interface and Guiding Loss (불연속 입력 경계면과 전송 손실이 있는 광 편파기 설계를 위한 새로운 편파조건)

  • Ho, Kwang-Chun
    • Journal of IKEEE
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    • v.11 no.1 s.20
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    • pp.61-68
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    • 2007
  • Using modal transmission-line theory (MTLT), itexplores rigorously the polarization characteristics of TE-TM mode optical polarized beamsplitter with misaligned input interface. To verify the validity of the approach proposed in this paper, a novel polarization condition is defined, and it compares and evaluates with the polarization condition of coupled-mode theory (CMT) used widely. The numerical results reveal that the discontinuity of misaligned input interface has nothing to do with the polarization condition of beamsplitter. Furthermore, the condition of CMT is no longer effective at the asymmetric guiding structures with strong power coupling.

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Stability Analysis of Pipe Conveying Fluid with Crack (크랙을 가진 유체유동 파이프의 안정성 해석)

  • Ahn, Tae-Su;Son, In-Soo;Yoon, Han-Ik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.865-868
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    • 2006
  • In this paper, a dynamic behavior(natural frequency) of a cracked simply supported pipe conveying fluid is presented. In addition, an analysis of the flutter and buckling instability of a cracked pipe conveying fluid due to the coupled mode (modes combined) is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The stiffness of the spring depends on the crack severity and the geometry of the cracked section. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. This study will contribute to the safety test and stability estimation of structures of a cracked pipe conveying fluid.

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Modeling and characteristics of $K^+$ ion-exchanged waveguide-type optical coupler ($K^+$ 이온교환 도파로형 광결합기의 모델링 및 특성)

  • 천석표;박태성;정홍배
    • Electrical & Electronic Materials
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    • v.9 no.3
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    • pp.259-264
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    • 1996
  • In this study, we performed a modeling for $K^{+}$ ion-exchanged diffused channel waveguide and waveguide-type optical coupler by Wentzel-Kramer-Brillouin(WKB) dispersion equation, normalized field distribution equation for mode and coupled mode theory, and examined the optical-power-dividing of the optical coupler fabricated by using the modeling condition. The optical-power-dividing was observed at the waveguide-type optical coupler with 3[.mu.m] line-width, 6[.mu.m] space between channel waveguides, and 3[mm] interaction length.h.

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