• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.502-503
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• 2014

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.123-127
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• 1993

소음방사의 이해 및 효과적인 소음제어를 위해서는 소음원의 특성, 음장의 공간상 방사 특성 등을 아는 것이 중요하며, 이를 위해 많은 연구가 진행되 어 왔다. 특히 다수의 마이크로폰 어레이를 이용한 음향 홀로그래피 방법에 의한 실험적 음장 예측 방법이 소개되었고 연구가 진행됨에 따라 많은 실용 가능성을 보여 주었다. 음향 홀로그래피 방법에는 측정상 제한이 필연적으로 존재할 수밖에 없는데, 이에 따른 오차가 존재하며 결국 예측음장의 신뢰도 를 떨어뜨리는 요인이 된다. 본 연구의 목적은 측정조건에 따른 오차의 요인 을 고찰하고 이를 정량적으로 표현함으로써 음향 홀로그래피 방법의 적용에 도움을 주고자 한다. 평면 음향 홀로그래피에 나타나는 오차는 둘러 싸기 오 차(wraparound error), 앨리애싱(aliasing), 창문영향(window effect)으로 나 눌 수 있는데, 오차는 측정구경의 크기와 마이크로폰 사이의 간격등의 측정 조건 뿐만 아니라 음원의 특성, 홀로그램 평면의 위치 등에 직접적인 영향을 받게 된다. 본 연구에서는 오차해석을 위한 기본 연구로써 점음원(monopole) 과 쌍극자(dipole)음장의 파수 스펙트럼을 해석적으로 구하고 이를 기본으로 평면 음향 홀로그래피 적용시 존재하는 앨리애싱에 대해 고찰하고 전산기 모의 실험 (computer simulation)을 통해 오차를 최소화하는 측정조건을 제 시하고자 한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.667-673
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• 2005

This paper shows a method for design of the nano-positioning planar scanner used in the scanning probe microscope. The planar scanner is composed of flexure guides, piezoelectric actuators and feedback sensors. In the design of flexure guides, the Castigliano's theorem was used to find the stiffness of the guide. The motion amplifying mechanism was used in the piezoelectric actuator to achieve a large travel range. We found theoretically the travel range of the total system and verified using the commercial FEM(finite element method) program. The maximum travel range of the planar scanner is above than 140 $\mu$m. The 3 axis positioning capability was verified by the mode analysis using the FEM program.

• Journal of KSNVE
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• v.9 no.3
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• pp.621-628
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• 1999

The fundamental dynamic properties of the planar electric charged particle are investigated experimentally. The experiment is conducted using electric charged spheres(4 table tennis balls with conductive surfaces) suspended by insulating strings to cancel the gravitational force. The measurements of the equilibrium angles and the natural frequencies of oscillation agree well with the analytical predictions with some error, respectively.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.199-207
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• 1999

The differential quadrature method (DQM) is applied to computation of eigenvalues of the equations of motion governing the free in-plane and out-of-plane vibrations for circular curved beams. Fundamental frequencies are calculated for the members with various end conditions and opening angles. The results are compared with existing exact solutions and numerical solutions by other methods (Rayleigh-Ritz, Galerkin or FEM) for cases in which they are available. The differential quadrature method gives good accuracy even when only a limited number of grid points is used.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.9
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• pp.171-182
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• 2019

Isogeometric concept is introduced to carry out free vibration analysis of plane structures. The geometry of structures is represented by using non-uniform rational B-spline surface (NURBS) and its basis function is consistently used in the formulation of plane stress element. In addition, multi-patch strategy is introduced to deal with the openings in building. The performance of the present isogeometric plane stress element is investigated by using five numerical examples. From numerical results, it is found to be that the isogeometric concept can successfully identify reliable natural frequencies and associated mode shapes of plane structures with/without openings in efficient way.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.31-40
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• 1991

This paper described on the availability fo the underwater telemetering by the ulterasonic multi-beam system made as a trial to expand detectable range of the fish school. The ultrasonic multi-beam system consisted of four transducers which reconstructed with the existing net recorder. The experiment for the telemetering carried out in the set net fishing ground. The results obtained are summerized as follows: 1. The detectable distance of a target by the linear arrangement of four transducers increased according to the sea depth and the interval between transducers. 2. When the fish school in the entrance of set net was measured by linear arrangement of transducers it was entered in depth of 2.5~3.5m at near position of leader, and in depth of 3.5~4.5m at near position of door net. 3. The deviations of error between the actual position and the position by transducer in case of the target depth 1m, 1.5m, 2m were 5.9~27.1cm, 3.2~28.9cm, 3.5~25.8cm respectively, and 68.3% probability radius of them were 14.6cm, 17.7cm, 17.0cm respectively. 4. When the fish school in the fish court of set net was measured by plane arrangement of transducer it was entered toward the opposite direction of tide current. 5. The available distance of telemetering by the multi-beam transducer was 1.8km and the telemetering was possible to control everywhere in case of sea depth more than three meters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.280-281
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• 2009

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1399-1404
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• 2000

• Journal of KSNVE
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• v.6 no.1
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• pp.35-44
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• 1996

This paper presents a new type of fuzzy-sliding mode controller for robust tip position control of a single-link flexible manipulator subjected to parameter variations. A sliding mode controller is formulated with an assumption that imposed parameter variations are bounded so that certain deterministic performance can be guaranted. In the design of the sliding mode controller, so called moving sliding surface is adopted to minimize the reaching phase and thus mitigate system sensitivity to the variations. The sliding mode controller is then incorporated with a fuzzy technique to reduce inherently ever-existing chattering which is impediment in position control of flexible manipulators. A set of fuzzy parameters and control rules are obtained from a relation between predetermined sliding surface and representative points in the state space. Computer simulations are undertaken in order to demonstrate superior control performance of the proposed methodology.