• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.9-22
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• 2005

The allowed operation space for the mass damper in an active tuned mass damper (ATMD) system is limited for most civil structures. In this study, a restrained stroke active tuned mass damper (RS-ATMD) system with a end-spring and a holder that reduces the stroke of the mass damper with maintaining the control effect durably is proposed. This new control system functions as a conventional ATMD within the predetermined stroke limitation under small excitation and as an RS-ATMD beyond that limitation under large excitation. A new control algorithm considering such an operation principle of the RS-ATMD are also provided. Parameteric study for the various design factors of the RS-ATMD is conducted and the control effectiveness are investigated in comparison with the ATMD. Exposed to sinusoidal or impact load, the RS-ATMD system shows the considerable reduction of the maximum stroke of the mass damper with the slight diminution in the control effectiveness. Excited by random load, it also shows the considerable reduction of the maximum stroke of the mass damper not allowing the diminution in the control effectiveness.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.105-111
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• 1999

Dampers have been used to dissipate energy in mechanical systems. There are several types of dampers such as passive, active, and semi-active damper. Semi-active dampers have higher performance than passive ones and require less power to operate than active ones. Their damping characteristics can be changed properly for varying conditions. In this paper, we investigated the semi-active damper using Magneto-Rheological fluid. Magneto-Rheological fluid, which is one of controllable fluids, changes its damping and rheological characteristics from Newtonian fluid to Bingham fluid as the magnetic field is applied. It has several advantages such as high yield strength, low viscosity, robustness to impurities and wide temperature range of stability. If we designe a semi-active damper by using this material, we can not only design a simply structured damper but also expect rapid response. In this study, we propose several types of semi-active dampers which are designed and manufactured using Magneto-Rheological fluid and some problems encountered during their applications.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.124-143
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• 1997

본 논문은 능동 구속층 감쇠(active constrained layer damping) 처리된 관의 동적 모델링과 정식화를 제시한다. 판의 운동방정식은 Hamilton정리를 이용하여 전개된 판, piezoelectric film 및 점탄성층의 운동방정식을 조합하므로서 유도된다. 이 운동방정식은 외부인가전압의 영향하에서 적층판의 해석적 모델을 제공할 뿐만이 아니라, 판 구조내에서 진동에너지를 감소시킬 수 있는 전단층의 효과에 대한 변위관계식을 나타낸다. 그리고 운동방정식에 대응하는 경계조건도 유도되었다. 또한 판과 능동구속층감쇠계의 동특성을 설명하기 위한 유한요소모델이 유도되었다. 이 모델의 타당성을 실온조건에서 실험적으로 입증하였다. 개발된 이론 및 실험적인 결과들은 판과 능동구속층 감쇠계가 구조진동의 감쇠를 위한 매우 유효한 수단으로 사용될 수 있음을 나타내었다.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.127-132
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• 2001

자기유변유체감쇠기를 이용한 반능동 제어 시스템은 최근에 개발되어 승용차의 승차감 향상을 위한 진동제어에 사용되고 있다. 본 연구에서는 바람, 지진, 파랑 등에 대한 대형구조물의 진동제어를 위한 MR 감쇠기의 적용성을 분석하기 위하여, 미국 토목학회에서 제안한 76층 건물의 풍하중에 대한 진동제어에 관한 Benchmark Problem에 대하여 수치모의 해석을 수행하였다. 연구결과로부터, 풍하중에 대한 고층 건물의 진동제어를 위하여 MR 감쇠기를 이용한 반능동 제어의 성능은 능동형 동조질량 감쇠기의 성능과 유사함을 확인할 수 있었다.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.16-23
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• 2001

Passive noise reduction is a classical approach to attenuate industrial noise, and an active noise cancellation has several advantages over the passive noise cancellation. The active noise reduction system offers a better low frequency performance with a smaller and lighter system. This paper presents a simple active closed loop control system which consists of an controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic out of phase signal to reduce the external noise, and external noise can be reduced after compensating the phase difference to be $180^{\circ}$ in the frequency of maximum value in the amplitude response. The noise of the phase delay covered from $50^{\circ}\;to\;310^{\circ}$ tends to be reduced in the active noise control system and it is possible to obtain a noise cancelling of up to approximately 20[dB] at the ears in the enclosurer.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.26-36
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• 2023

공군 조종사들이 비행 중에 겪는 지속적이고 강도 높은 소음은 조종사의 생리적(physiological) 및 심리적(psychological) 상태에 부정적인 영향을 미칠 수 있다. 이는 조종사의 비행 능력(performance)에 부정적인 영향을 주게 되며 임무 완수 및 비행 안전을 저해시키는 치명적인 결과로 이어질 수 있다. 대한민국 공군은 조종사들의 청력 보호를 위해 수동 소음 감쇠(Passive Noise Cancellation, PNC) 및 능동 소음 감쇠(Active Noise Cancellation, ANC) 기술이 적용된 헤드셋 및 헬멧을 사용 중이다. 그러나, 소음 저감 기술이 조종사의 청력 보호, 비행 능력, 및 비행 안전에 미치는 효용성에 대한 공군 조종사의 인식은 아직 연구된 바가 없다. 따라서 본 연구는 소음과 관련된 이론적 배경을 고찰하였고, 이후 설문조사를 통해 공군 조종사들(n=154)의 조종석 내 소음 및 소음 감쇠 기술에 대한 인식을 분석하였다. 분석 결과, 능동 소음 감쇠(ANC) 기술이 적용된 헤드셋 및 헬멧의 사용은 소음이 조종사의 생리적 상태에 미치는 영향에는 유의미한 효과가 없지만(p=0.402), 심리적 상태에 미치는 영향은 유의미하게 감소시키는 것으로 나타났다(p<0.001). 따라서, 능동 소음 감쇠(ANC) 기술이 적용된 비행 헤드셋 및 헬멧 사용의 필요성을 강조하였고, 이를 통해 조종사의 비행 능력(performance) 저하 방지 및 비행 안전 증진에 기여하고자 한다.

• Journal of Korean Association for Spatial Structures
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• v.6 no.3 s.21
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• pp.59-67
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• 2006

A conventional passive TMD is only effective when it is tuned properly. In many practical applications, inevitable off-tuning of a TMD occurs because the mass in a building floor could change by moving furnishings, people gathering, etc. when TMDs are offtuned, TMDs their effectiveness is sharply reduced. Moreover, the off-tuned nTMDs can excessively amplify the vibration levels of the primary structures. This paper discusses the application of a new class of MR damper, for the reduction of floor vibrations due to machine and human movements. The STMD introduced uses a MR damper called to semi-active damper to achieve reduction in the floor vibration. Here, the STMD and the groundhook algorithm are applied to a single degree of freedom system representative of building floors. The performance or the STMD is compared to that or the equivalent passive TMD. In addition, the effects of off-tuning due to variations in the mass of the floor system. Comparison of the results demonstrates the efficiency and robustness or STMD with respect to equivalent TMD.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.13-20
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• 2001

The active noise cancellation system offers a better low frequency performance with a smaller and lighter system compared to a passive one. This paper presents an active noise control system capable of reducing the noise in a helmet after attenuating the external noise using the helmet as the passive noise reduction system, which consists of a controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic anti-phase signal to reduce the external noise. In this paper, external noise can be reduced by noise controller by compensating the phase difference to be 180°in the frequency of maximun value in the amplitude response. The noise of the phase delay covered from 50°to 310°was reduced in this system and it is possible to obtain a noise reduction of up to approximately 20 dB at the ears in the enclosure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.959-967
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• 1988

In this paper, 2-DOF vehicle suspension system with a semiactive on-off damper was studied for improving the ride comfort. It is known that a nonlinear hydraulic damper, which generates force proportional to the square of the relative velocity, can describe the actual fluid resisting type damper more properly than the traditional viscous damping model. On the other hand, hydraulic damper adoption in analysis makes the system nonlinear and causes difficulties to get the system response. In this work, time domain direct integration method was used to calculate system displacement and acceleration. first of all, the response of the suspension system experiencing a given road profile was optimized by Lagrangian multiplier method within the range of given damping coefficients. The appropriate on-loaf damping values were obtained by averaging the already calculated optimum damping coefficients from Lagrangian techniques. The criterion to control the on-off mechanism was determined by examining the suspension efficiency. It was found that the best out of practically applicable criteria is following the sign (positive and negative) of the multiplication of relative displacement and velocity. Judging from the theoretical calculations, it was proved that the semiactive on-off damper can increase suspension efficiency as much as 8-11% in object function.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.233-238
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• 2006

In this paper, mixed mode magneto-rheological(MR) damper, which is applicable for vibration control of a small scale multi-story structure, is devised. First, the schematic configurations of the shear, flow, and mixed mode MR dampers are described with design constraints and then the analytical models to predict the field-dependent damping forces are derived for each type. Second, an appropriate size of the mixed mode MR damper is manufactured and its field-dependent damping characteristics are evaluated in time domain. Finally, the performance of the manufactured MR damper which is semi-actively applied to a small scale building excited by earthquake load, is numerically evaluated.