• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.263-269
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• 2003

This paper describes the vibration control using a tuned mass damper(TMD) for the existing footbridge. The footbridge connecting driveway to the Stadium is the simple steel box-girder bridge with the main span length of 44.6m. This footbridge has light weight(=25.3kN/m) and pedestrians walking on the footbridge were found to induce resonance at the fundamental mode of the structure, resulting in unacceptable accelerations in it. Taking into account economical and constructional benefits, TMD was designed to damp the vibrations of the modes next to the natural frequency caused by a pedestrian, with a limitation criteria of vertical amplitude. A set of two 500kgf vertical TMDs was manufactured by KR and installed into the railings next to the central section of this footbridge. The installation of TMDs reduced the peak acceleration in the meeting box to less than 90%. It is hoped that the study will present bridge engineers with a measure of retrofitting footbridges to make them more friendly to users.

• 대한기계학회논문집A
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• 제32권11호
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• pp.970-977
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• 2008

This paper deals with the dynamic characteristics of the shaft with impeller model which is the most important part in developing the resin mixing machine. Through reverse engineering, it is possible to make the shaft with impeller geometry model which is necessary vibration characteristic analysis by commercial impeller. The natural frequency analysis and structural analysis using finite element analysis software are performed on the imported commercial shaft with impeller model. The most important fundamental natural frequency of the shaft with impeller model is around 14.5 Hz, which well agrees with modal testing. The most effective design variables were extracted by ANOM(analysis of means) and pareto chart. This paper presents approximation 2nd order polynomial as design variables using RSM(response surface methodology). Generally, RSM take 2 or 3 design variables, but this method uses 5 design variables with table of mixed orthogonal array. Further more, the analyzed result of the commercial shaft with impeller is to be utilized for the structural design of resin chock mixing machine.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.353-354
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• 2014

An active vibration control technique of a time-varying cantilever beam is proposed in this study. A simple in-house coil sensor instead of expensive commercial sensors was used to measure the vibrational displacement of the beam. Active band pass filters and artificial neutral net works detect the frequencies, amplitudes, and phases of the main vibration mode. The time constants of the low pass filter representing the positive position feedback controller are updated in real-time, which generates the control voltage input to actuate the piezoelectric actuator and suppress the vibration. An experiment was successfully performed to verify the algorithm for a cantilever beam, which fundamental natural frequency arbitrarily varies between 9 Hz ~ 18 Hz. The present active vibration suppression technique can be applied to variety of structures which undergoes large variation of dynamic characteristics while operating.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.197-202
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• 2014

Floor Impact Noise is a structure-borne noise which is mainly caused by vibration of concrete slabs. The majority of previous studies have focused on investigating performance of absorbing sheets on the reduction of floor impact noise. But absorbing sheets do not efficiently reduce heavy-weight floor impact noise level because it cannot absorb slab vibration, which is the fundamental noise source. In this study, double-floor system was developed in order to reduce floor impact noise level in residual buildings. This floor system reduces heavy-weight impact noise level by reducing vibration response at the center of slab, which has maximum amplitude in the 1st vibration mode. In order to identify the performance of the double-floor system, experiments were planned. Primary test parameters are span of double floor, arrangement and types of absorbing sheets.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.195-203
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• 2002

In the engine room and the aft part areas of the ship, there exist so many tank structures contacting with fresh water or sea water or oil. If these structures exhibit excessive vibrations during the sea trials, it takes a lot of cost, time and effort to improve vibration situation because the reinforcement work requires emptying the fluid out of the tanks, additional welding and special painting. It is therefore very important to predict a precise vibration characteristics of the tank structures at the design stage, however it is not easy to estimate vibration characteristics of the structures because of difficulties for accurate evaluation of the added (or virtual) mass effect due to the fluid inside the tank. In this paper, numerical and experimental approaches have been performed to present same fundamental data necessary for anti-vibration design of tank structures contacting with fluid, by investigating vibration behaviors of rectangular tank structure for various water depths.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.157-163
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• 2008

The HCCI combustion mode poses its own set of narrow engine operating by knocking. In order to solve this, inhomogeneity method of mixture and temperature is suggested. The purpose of this research is to get fundamental knowledge about the effect of thermal stratification on HCCI combustion of PRF -Air mixture. The temperature stratification is made by buoyancy effect in combustion chamber of RCM. The analysis items are pressure, temperature of in-cylinder gas and combustion duration. In addition, the structure of flames using the two dimensional chemiluminescence's images by a framing camera are analyzed. Under stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous. Further, the LTR period of homogeneous conditions became shorter than that of the stratified conditions. With the case of homogeneous condition, the luminosity duration becomes shorter than the case of stratified condition. Additionally, under stratified condition, the brightest luminosity intensity is delayed longer than at homogeneous condition.

• 전력전자학회논문지
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• 제23권2호
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.

• 한국전자파학회논문지
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• 제14권11호
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• pp.1143-1148
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• 2003

CPW와 마이크로스트립선로에서 수십 피코초의 펄스 폭을 갖는 가우시안(Gaussian) 펄스 신호가 진행해 갈 때 기판 및 선로 구조에 따른 분산 및 펄스의 전파 특성을 시간 영역에서 해석하고 측정하였다. 특히, 선로에 사용된 기판의 기본 TE 모드에 대한 차단 주파수( $f_{TE}$ )의 변화에 따른 CPW와 마이크로스트립 선로간의 전송특성을 구하고 비교하였다. 이를 실험적으로 확인하기 위해 $f_{TE}$ 가 다른 기판에 두 가지 50 $\Omega$ 선로를 제작하여 수십 피코초 펄스가 진행되었을 때의 전송 특성을 시간 영역 분석기능이 내장된 VNA(Vector Network Analyzer)를 이용해서 측정하였다.

• 한국안전학회지
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• 제29권3호
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• pp.85-90
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• 2014

The purpose of this study is to analysis the 3 differential size of the interior space for impulse noise. To achieve this goal the 3 kinds (27, 35, $50m^3$) of interior space were performed comparing the impulse noise. Result of this study, the standard error of the mean peak sound pressure of value from 0.19 to 0.27dB and there was no significant difference (p<0.01). And B-duration is significant differences (P<0.01) range from 3.98 to 7.93ms. This is respectively less than 10ms. These findings are confirmed in accordance by the 3 differential space size of the indoor-impulse noise due to 0.3 dB or less, so there was no difference to the operational influence. And also below 100 Hz were found fundamental mode frequency analysis. Results were matched with calculated theoretical values.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.465-469
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• 2013

Proton transfer reaction is one of the most fundamental processes in chemistry and life science. Excited state intramolecular proton transfer (ESIPT) has been studied as a model system of the proton transfer, since it can be conveniently initiated by light. We report ESIPT reaction dynamic of 1-hydroxy-anthraquione (1-HAQ) in solution by highly time-resolved fluorescence. ESIPT time of 1-HAQ is determined to be $45{\pm}10$ fs directly from decay of the reactant fluorescence and rise of the product fluorescence. High time resolution allows observation of the coherent vibrational wave packet motion in the excited state of the reaction product tautomer. The coherently excited vibrational mode involves large displacement of the atoms, which shortens the distance between the proton donor and the acceptor. With the theoretical analysis, we propose that the ESIPT of 1-HAQ proceeds barrierlessly with assistance of the skeletal vibration, which in turn becomes excited coherently by the ESIPT reaction.