• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.270-272
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• 2003

We have investigated the coupling characteristics of localized modes of line defect i.e., guided modes, in photonic crystals. The parity of the coupled guided modes is not conserved when the distance between the line defects changes. By comparing the coupling characteristics of localized modes without the oscillatory nature such as cavity modes of metallic Fabry-Parot cavities with those of localized modes in photonic crystals, we confirmed that this parity nonconservation is attributed to the oscillatory nature of the evanescent waves of localized modes in photonic crystals.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1302-1307
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• 2001

This study identifies the major coupling path by examining the variation of the coupled acoustic modal frequencies and modes. A 1/2-size acryl compartment model is designed and manufactured for the measurement and analysis of coupled acoustic modes. Due to acoustic coupling, a new acoustic mode appears in a low frequency range. This coupling affects only longitudinal acoustic modes of compartment. Experimental result shows that the package tray holes contribute to the coupling much more than the back seat and hole size is an important design factor to control low frequency acoustic modes in the coupled system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2245-2250
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• 1994

The normal coordinates of a nonclassically damped systems are coupled by nonzero off-diagonal elements of modal damping matrix. The relationship between modal coupling and the frequency separation of the natural modes is presented in this paper. Contrary to widely accepted beliefs, increasing the frequency separation of the natural modes does not neccessarily diminish the effect of modal coupling. Consequently, in the pratical engineering applications, wide frequency separation of the natural modes would not be sufficient for neglecting modal coupling.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.76-80
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• 2011

This paper proposes a method to calculate magnetostrictive forces, displacement, and vibration modes of a large-scale Brushless DC(BLDC) motor by using a magneto-mechanically strong coupling formulation. The force is calculated using the energy method with magnetostrictive stress tensor. The mechanical vibration modes are also analyzed by using the principle of Hamilton and the calculated magneto-elastic forces acting on the surfaces of the stator. To verify the algorithm, 3 MW BLDC motor is simulated, and the forces, displacements, and vibration modes are calculated. The result shows that the mechanically stressed core has more deformation or displacements than those of the normal condition.

• Wind and Structures
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• v.14 no.3
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• pp.239-252
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• 2011

The wind-induced mean, background and resonant responses of Beijing National Stadium are investigated in this paper. Based on the concepts of potential and kinetic energies, the mode participation factors for the background and the resonant components are presented and the dominant modes are identified. The coupling effect between different modes of the resonant response and the coupling effect between the background and resonant responses are analyzed. The coupling effects between the background and resonant components and between different modes are found all negligible. The mean response is approximately analogous to the peak responses induced by the fluctuating wind. The background responses are significant in the fluctuating responses and it is much larger than the resonant responses at the measurement locations.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.607-611
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• 2000

Acoustic modal property of the vehicle passenger compartment is a very important factor which dominates vehicle interior noise in the low frequency range. In most real cars, trunk noise often transfers into the passenger compartment since the two cavities are acoustically coupled. This study identifies the major coupling path by examining the variation of the coupled acoustic modal frequencies and modes. An 1/2 size acryl compartment model is designed and manufactured for the measurement and analysis of coupled acoustic modes. Experimental result shows that package tray contributes to the coupling much more than the back seat and hole size of the package tray is an important design factor to control low frequency acoustic modes in the coupled system.

• Proceedings of the IEEK Conference
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• 2002.07a
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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.

• Structural Engineering and Mechanics
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• v.51 no.2
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• pp.315-331
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• 2014

The present study investigated the effect of the correlation of the measured road roughness profiles corresponding to the left and right wheels of a vehicle on the vibration of a vehicle-bridge coupling system. Four sets of road roughness profiles were measured by a laser road-testing vehicle. A correlation analysis was carried out on the four roughness samples, and two samples with the strongest correlation and weakest correlation were selected for the power spectral density, autocorrelation and cross-correlation analyses. The scenario of a three-axle truck moving across a rigid-frame arch bridge was used as an example. The two selected road roughness profiles were used as inputs to the vehicle-bridge coupling system. Three different input modes were adopted in the numerical analysis: (1) using the measured road roughness profile of the left wheel for the input of both wheels in the numerical simulation; (2) using the measured road roughness profile of the right wheel for both wheels; and (3) using the measured road roughness profiles corresponding to left and right wheels for the input corresponding to the vehicle's left and right wheels, respectively. The influence of the three input modes on the vibration of the vehicle-bridge system was analyzed and compared in detail. The results show that the correlation of the road roughness profiles corresponding to left and right wheels and the selected roughness input mode both have a significant influence on the vibration of the vehicle-bridge coupling system.

• Journal of Power Electronics
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• v.18 no.3
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• pp.879-891
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• 2018

A bidirectional dc-dc converter is used in battery energy storage systems owing to the growing requirements of a charging and discharging mode of battery. The magnetic coupling of output or input inductors in parallel-connected multi modules of a bidirectional dc-dc converter is often utilized to reduce the peak-to-peak ripple size of the inductor current. This study proposes a novel design guideline to achieve minimal ripple size of the inductor current under bidirectional power flow. The newly proposed design guideline of optimized coupling factor is applicable to the buck and boost operation modes of a bidirectional dc-dc converter. Therefore, the coupling factor value of the coupled inductor does not have to be optimized separately for buck and boost operation modes. This new observation is explained using the theoretical model of coupled inductor and confirmed through simulation and experimental test.

• Bulletin of the Korean Chemical Society
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• v.15 no.3
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• pp.228-236
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• 1994

The effect of the vibration mode coupling induced by the vibration-rotation interaction on total energy was investigated for the states with zero total angular momentum(J=0) in a quasilinear symmetric triatomic molecule of $AB_2$ type using a model potential function with a slight potential barrier to linearity. It is found that the coupling energy becomes larger for the levels of bend and asymmetric stretch modes and smaller for symmetric stretch mode as the excitation of the vibrational modes occurs. The results for the real molecule of $CH_2^+$, which is quasilinear, generally agree with the results for the model potential function in that common mode selective dependence of coupling energy is exhibited in both cases. The differences between the results for the model and real potential function in H-C-H system are analyzed and explained in terms of heavy mixing of the symmetric stretch and bend mode in excited vibrational states of the real molecule of $CH_2^+$. It is shown that the vibrational mode coupling in the potential energy function is primarily responsible for the broken nodal structure and chaotic behavior in highly excited levels of $CH_2^+$ for J= 0.