• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.208-214
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• 2000

Reduction of structure-borne noise of the compartment in a car is an important task in automotive engineering. Transfer path analysis using vibroacoustic reciprocity technique or multiple path decomposition method has generally been used for structure-borne noise path analysis. These methods are useful in solving particular problem but do not quantify the effectiveness of vibration isolation of each isolator of a vehicle. To quantify the effectiveness of vibration isolation, the vibrational power flow has been used for a simple isolation system or a laboratory based isolation system. It is often difficult to apply the vibrational power flow technique to the complex isolation system like a car. In this paper, a simple equation is derived for calculation of the vibrational power flow of an isolation system with multiple isolators such as a car. It is successfully applied to not only quantifying the relative contributions of eighteen isolators but also reducing structure-borne noise of a passenger car. According to the results, the main contributor of eighteen isolators is the rear roll mount of an engine. The reduced structure-borne noise level is about 5dBA.

• Smart Structures and Systems
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• 제32권6호
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• pp.383-391
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• 2023

Energy harvesting in trams may become a prevalent source of passive energy generation due to the high density of vibrational energy, and this may help power structural health monitoring systems for the trams. This paper presents a broadband vibrational energy harvesting device design that utilizes a varied frequency from a tram vehicle using a 2 DOF vibrational system combined with electromagnetic energy conversion. This paper will demonstrate stepwise optimization processes to determine mechanical parameters for frequency tuning to adjust to the trams' operational conditions, and electromagnetic parameters for the whole system design to maximize power output. The initial optimization will determine 5 important design parameters in a 2 DOF vibrational system, namely the masses (m₁, m₂ (and spring constants (k₁, k₂, k₃). The second step will use these parameters as initial guesses for the second optimization which will maintain the ratios of these parameters and present electrical parameters to maximize the power output from this system. The obtained values indicated a successful demonstration of design optimization as the average power generated increased from 1.475 mW to 17.44 mW (around 12 times).

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.533-536
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• 2016

본 논문에서는 진동 에너지를 이용한 MPPT 제어기능을 갖는 에너지 하베스팅 회로를 설계하였다. Body-bias technique과 bulk-driven technique을 이용하여 저전압에서도 높은 효율특성을 갖는 고성능 AC-DC 변환기를 제안하고 진동에너지 하베스팅 회로 설계에 적용하였다. MPPT (Maximum Power Point Tracking) 제어는 진동소자의 개방회로전압과 MPP 전압간의 관계를 이용하였으며, 진동소자의 개방회로전압을 주기적으로 샘플링 함으로써 이를 이용해 MPPT 기준전압을 생성하고, 이를 기준으로 부하로의 에너지 공급을 제어한다. $0.35{\mu}m$ CMOS 공정으로 설계된 회로의 칩 면적은 $1.21mm{\times}0.98mm$이다.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.150-158
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• 2009

A centrifugal turbo blower is one of the part to generate electric power of fuel cell electric vehicle(FCEV). In order to generate the electric power of FCEV, the centrifugal turbo blower operates at very high speed above 30,000rpm in order to increase the pressure of the air, which supplied to a stack of FCEV, using rotation of its impeller blades. Vibration which originated from the blower is generated by unbalance of mechanical components, rotation of bearings and rotating asymmetry that rotate at high speed. The vibration is transmitted to receiving structure through vibration isolators and it can causes serious problems in the noise, vibration and harshness(NVH) performance. Thus, the study about reducing this kind of vibration is an important task. Quantifying the effectiveness of vibration isolation can be effectively accomplished by using vibrational power flow because relative contributions of each isolator to the total vibration transmission can be easily represented. In this paper, vibrational power flow is applied to the centrifugal turbo blower mounted on FCEV in order to analyze the most dominant vibration transmitting path. As a result, the main contributor among four isolators is a mount #3 of the blower. Also, a 30 percent lowering of the mount #3 stiffness shows 34 percent decrement of vibrational power flow by the simulation.

• 한국정밀공학회지
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• 제19권6호
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• pp.109-118
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• 2002

The vibrational intensity and the dynamic response of a compound vibratory system had been controlled actively by means of a feedforward control method. A compound vibratory system consists of a flexible beam and two discrete systems - a vibrating source and a dynamic absorber. By considering the interactive motions between discrete systems and a flexible beam, the equations of motion for a compound vibratory system were derived using a method of variation of parameters. To define the optimal conditions of a controller the cost function, which denotes a time averaged power flow, was evaluated numerically. The possibility of reductions of both of vibrational intensity and dynamic response at a control point located at a distance from a source were fecund to depend on the positions of a source, a control point and a controller. Especially the presence of a dynamic absorber gives the more reduction on the dynamic response but the less on the vibrational intensity than those without a dynamic absorber.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.78-84
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• 2001

In this paper, Power Flow Boundary Element Method(PFBEM) has been developed for one and two dimensional noise and vibration problems in the medium to high frequency ranges. Green functions used for PFBEM are the fundamental solutions of energy governing equations. Both direct and indirect methods of PFBEM have been formulated and numerically applied to predict the vibrational energy density and intensity distributions of simple beams, rectangular plates and L-type plates.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1177-1184
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• 2002

In this paper, power flow analysis method on the various types of thin shell has been developed to solve vibrational Problems in the medium to high frequency ranges. Energy governing equations have been derived both for out-of plane and in-plane waves in thin shell. These results have been numerically applied to predict the vibrational energy density and intensity distributions of cylindrical, spherical and doubly-curved shells.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1986년도 춘계학술발표회 논문집
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• pp.202-205
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• 1986

In this paper, real-time vibration measurement using system is described. Modes getting from different vibrational frequencies of come vibrational plates are rectified and filtered by digitizer and recorded 488 dots(abscissa) printer. PZT and mechanical chopper is placed in front of cw laser for better resolving power. Rayleigh`s mode theory and mode pattern are compared with experimental results.

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.8-16
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• 1998

In this work a method to detect the vibrational peak and to decide the vibrational mode of detected peak for core internal vibration monitoring system which is particularly concerned on the core support barrel (CSB) and fuel assemblies is developed. Flow induced vibration and aging process in the reactor internals cause unsoundness of the internal structure. In order to monitor the vibrational status of core internal, signals from the ex-core neutron detectors are transformed into frequency domain. By analyzing transformed frequency domain signal, an analyst can acquire the information on the vibrational characteristics of the structures, i.e., vibration frequencies of each component, vibrational level, modes of vibration, and the causes of the abnormal vibration, if any. This study is focused on the development of the automated monitoring system. Several methods are surveyed to define the peaks in power spectrum and fuzzy theory is used to automatic detection of the vibrational peaks. Fuzzy algorithm is adopted to define the modes of vibration using the peak values from fuzzy peak recognition, phase spectrum, and coherence spectrum.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.423-439
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• 2006

This paper proposes a hybrid analytic method for the prediction of vibrational and acoustic responses of reverberant system in the medium-to-high frequency ranges by using the PFA(Power Flow Analysis) algorithm and SEA(Statistical Energy Analysis) coupling concepts. The main part of this method is the application of the coupling loss factor(CLF) of SEA to the boundary condition of PFA in reverberant system. The hybrid method developed shows much more promising results than the conventional SEA and equivalent results to the classical PFA for various damping loss factors in a wide range of frequencies. Additionally, this paper presents applied results of hybrid power flow finite element method(hybrid PFFEM) by formulating the new joint element matrix with CLF to analyze the vibrational responses of built-up structures. Finally, the analytic results of coupled plate structures and an automobile-shaped structure using hybrid PFFEM were predicted successively.