• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.19-27
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• 2003

This paper presented an experimental modal analysis of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the Rayleigh-Ritz method and compared with the experimental results. Good agreement was obtained between the analytical solution and experimental result. The experimental results in water showed that the mode shapes are not sensitive to the depth of submergence. The natural frequencies were shown to decrease drastically once the perforated plates come in contact with water. However, the natural frequencies decrease with the depth of submergence until a certain depth is reached, and become the asymptotic values beyond this depth of submergence. The depth of submergence did not affect the damping ratio greatly.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.97-104
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• 2003

The main objectives of this study are to examine the random responses of a vibration absorber system with autoparametric coupling in the neighborhood of internal resonance subjected to narrow band random excitation by Gaussian closure scheme and to compare the results with those obtained by Monte Carlo simulation. The Monte Carlo simulation is found to support the main features of the nonlinear modal interaction in the neighborhood of internal resonance conditions. The jump phenomenon of the cantilever mode and saturation phenomenon of the main system are shown to occur if the excitation bandwidth is sufficiently small.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.345.1-345
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• 2002

This paper dealt with an experimental study on the hydroelastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energies and compared with the experimental results. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.276-276
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• 2003

This paper dealt with an experimental study on the free vibration of circular-tube-beam submerged in water. A circular-tube-beam is commonly founded on the nuclear fuel assembly system in nuclear reactor. The nuclear fuel assembly susceptible to flow-induced vibration in nuclear reactor. So, the nuclear fuel assembly be designed to avoid any resonance due to the vibration during the reactor operation. In the experiment, applied boundary condition is clamped-free and the effect of water height to natural frequency and damping is studied. The experiment in air and in water has been performed. Used experimental method is impact exciting method. The natural frequencies and damping ratio according to water height is presented.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1848-1862
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• 2006

As a basic study on the fluid-structure interaction of the shell structure, a theoretical formulation has been suggested on the free vibration of a thin-walled conical frustum shell filled with an ideal fluid, where the shell is assumed to be fixed at both ends. The motion of fluid coupled with the shell is determined by means of the velocity potential flow theory. In order to calculate the normalized natural frequencies that represent the fluid effect on a fluid-coupled system, finite element analyses for a fluid-filled conical frustum shell are carried out. Also, the effect of apex angle on the frequencies is investigated.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.864-867
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• 1998

This is Part I of a two part paper dealing with control design in power systems using the method of normal forms. In stressed power systems, due to the presence of increased nonlinearity and the existence of nonlinear modal interactions. there exist some limitation to the use of conventional linear control design techniques. The objective of this work is to understand the effect of the nonlinear modal interaction on control performance and to develop a procedure to design controls incorporating the nonlinear information. Part II presents the numerical results dealing with the design procedure.

• Journal of Korea Multimedia Society
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• v.21 no.12
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• pp.1459-1466
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• 2018

Robots which detect human and recognize action are important factors for human interaction, and many researches have been conducted. Recently, deep learning technology has developed and learning based robot's technology is a major research area. These studies require a database to learn and evaluate for intelligent human perception. In this paper, we propose a multi-modal sensor-based image database condition considering the security task by analyzing the image database to detect the person in the outdoor environment and to recognize the behavior during the running of the robot.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.241-248
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• 1987

The theoretical backgrounds of the several methods were surveyed and reviewed to fin out the adequate one to determine equivalent modal damping values in solving the dynamic problem of soil-structure interaction by mode superposition method. Furthermore the rigorous damping matrix of equation of motion was obtained through component mode synthesis technique and used in direct integration of the equation. The analytical results by direct integration method were compared with those of mode superposition approach using the various sets of equivalent modal damping values calculated by the methods to be reviewed. Two types of superstructures and four kinds of subsurface conditions were considered and combined to make soil-structure coupled models. It was realized that dissipating energy method gives the equivalent modal damping values which lead the most similar results to direct integration ones. In case of fixed base, the responses of all methods except stiffness weighted approach are almost equal to those of direct integration method.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.359-366
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• 2010

For the application of Lamb wave to structural health monitoring(SHM), understanding its physical characteristic and interaction between Lamb wave and defect of the host structure is an important issue. In this study, reflected, transmitted and mode converted Lamb waves at discontinuity of a plate structure were simulated and the amplitude ratios are calculated theoretically using Modal decomposition method. The predicted results were verified comparing with finite element method(FEM) and experimental results simulating attached PZTs. The result shows that the theoretical prediction is close to the FEM and the experimental verification. Moreover, quantitative estimation method was suggested using amplitude ratio of Lamb wave at discontinuity.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2006.06a
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• pp.57-62
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• 2006

휴대용 단말기의 소형화 및 지능화와 더불어 차세대 PC 기반의 유비쿼터스 컴퓨팅에 대한 관심이 높아짐에 따라 최근에는 펜이나 음성 입력 멀티미디어 등 여러 가지 대화 모드를 구비한 멀티 모달 상호작용 (Multi-Modal Interaction MMI)에 대한 연구가 활발히 진행되고 있다. 따라서, 본 논문에서는 잡음 환경에서의 명확한 의사 전달 및 휴대용 단말기에서의 음성-제스처 통합 인식을 위한 인터페이스의 연구를 목적으로 Voice-XML과 Wearable Personal Station(WPS) 기반의 음성 및 내장형 수화 인식기를 통합한 멀티 모달 명령어 인식 시스템 (Multi-Modal Instruction Recognition System : MMIRS)을 제안하고 구현한다. 제안되어진 MMIRS는 한국 표준 수화 (The Korean Standard Sign Language : KSSL)에 상응하는 문장 및 단어 단위의 명령어 인식 모델에 대하여 음성뿐만 아니라 화자의 수화제스처 명령어를 함께 인식하고 사용함에 따라 잡음 환경에서도 규정된 명령어 모델에 대한 인식 성능의 향상을 기대할 수 있다. MMIRS의 인식 성능을 평가하기 위하여, 15인의 피험자가 62개의 문장형 인식 모델과 104개의 단어인식 모델에 대하여 음성과 수화 제스처를 연속적으로 표현하고, 이를 인식함에 있어 개별 명령어 인식기 및 MMIRS의 평균 인식율을 비교하고 분석하였으며 MMIRS는 문장형 명령어 인식모델에 대하여 잡음환경에서는 93.45%, 비잡음환경에서는 95.26%의 평균 인식율을 나타내었다.