• 한국음향학회지
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• 제22권5호
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• pp.337-344
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• 2003

자기부상열차의 가장 중요한 소음원인 VVVF 인버터와 DC/DC 컨버터는 탄성체인 코어가 MS (Magnetostriction)에 의해 가진되어 소음을 발생한다. DC/DC 컨버터는 변압기가 주원인이며 소음/진동 스펙트럼에 가진주파수의 하모닉성분이 뚜렷하게 나타난다. 반면, LIM/VVVF 인버터소음은 가진주파수의 하모닉성분은 미약한 대신 변환주파수의 하모닉성분이 매우 강하게 나타난다. VVVF 인버터소음에서 변환주파수를 올리면 하모닉성분이 고주파수대역으로 이동하는데 700 ㎐를 2㎑로 올리면 소음이 5-6 ㏈ 감소되는 것으로 나타났다. 현 기술수준으로 MS에 의한 탄성체의 소음/진동을 정량적으로 예측하기는 어려운 실정이므로 본 논문에서는 정성적으로 MS에 의한 가속도 스펙트럼을 예측하였고 VVVF 인버터에 대해 변환주파수 증가의 효과를 확인할 수 있었다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권3호
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• pp.59-63
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• 2001

This paper presents a new modeling of the two dimensional magnetic property in soft magnetic materials for the magnetic field computations. In this modeling an approximate treatment is introduced to expand the applicable exciting frequency range. The result shows that the new modeling presented here is very useful in simplicity of magnetic field analysis.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.91-100
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• 1997

In this paper the linearzed stiffness and damping coefficients of tilting pad thrust bearing are calculated by the perturbation method. The coefficients are obtained for a wide range of pivot positions. The effects of exciting frequency and pad mass on stiffness and damping coefficients are investigated. Critical frequencies due to the tilting motions of the pad are presented and are shown to be strongly influenced by the pivot position and pad mass.

• Tribology and Lubricants
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• 제13권3호
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• pp.33-41
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• 1997

In this paper the linearized stiffness and damping coefficients of tilting pad thrust bearing are calculated by the perturbation method. The coefficients are obtained for a wide range of pivot positions. The effects of exciting frequency and pad mass on stiffness and damping coefficients are investigated. Critical frequencies due to the tilting motions of the pad are presented and are shown to be strongly influenced by the pivot position and the pad mass.

• 한국화재소방학회논문지
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• 제18권2호
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• pp.34-40
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• 2004

층류 비예혼합 분류 화염에서 다양한 주파수와 강도로 외부에서 유동장에 자극을 주었을 때 화염의 배출특성과 거동에 대해서 실험적으로 조사하였다. 먼저 일정한 관 공명 주파수에서 가진 강도를 가변시켜 난류화염 된 부상화염에서 질소산화물 배출 지수($EINO_x$)를 측정하였다. 또한, 가진 강도가 일정한 상태에서 주파수를 0 Hz에서 높은 주파수인 2 KHz까지 다양한 주파수 조건으로 가진된 한 경우에도 질소산화물의 배출지수를 측정하였다. 큰 가진 강도의 관공명 주파수로 가진된 경우 부상된 난류화염에서 $NO_x$ 배출 특성은 다음과 같이 크게 세 가지 형태의 특성을 보였다. Group I의 화염에서는 공간적인 섭동이 크며 비교적 화염길이가 길고 높은 $NO_x$ 배출 특성을 보였으며 Group II에서는 상대적으로 짧은 길이와 좁은 폭의 화염거동에 낮은 $NO_x$배출 특성을 보였다. Group III에서는 약간 긴 화염길이에 매우 큰 화염체적으로 상당한 높이까지 시ㆍ공간적으로 섭동이 큰 운동양태로 부상되는 거동과 가장 높은 $NO_x$ 배출 특성을 보였다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2000년도 춘계 학술대회 및 국제 감성공학 심포지움 논문집 Proceeding of the 2000 Spring Conference of KOSES and International Sensibility Ergonomics Symposium
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• pp.15-25
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• 2000

Cardiac, respiratory, electrodermal and frontal (F3, F4) EEG responses were analyzed and compared during to slides of International Affective Picture System (IAPS) in the study on 42 students. Physiological responses during 20s of exposure to slides intended to elicit happiness (nurturant and erotic), sadness, disgust, surprise, fear or anger emotions were quite similar and were expressed in heart rate (HR) deceleration, decreased HR variability (HRV), specific SCR, increased non-specific SCR frequency (N-SCR), and EEG changes exhibited in theta increase, alpha-blocking and increased beta activity, and frontal asymmetry. However, some emotions demonstrated variations of the response magnitudes, enabling to differentiate some paris of emotions by several physiological parameters. The profiles showed higher magnitudes of HRV and EEG responses in exciting (i.e., erotic) and higher cardiac and respiratory responses in surprise. The most different pairs were exciting-surprise (by HR, HRV, theta, and alpha asymmetry), exciting-sadness (by theta, alpha, and alpha asymmetry), and exciting-fear (by HRV, theta, F3 alpha, and alpha asymmetry). Nurturant happiness yielded the least differentiation. Differences were found as well within negative emotions, e.g., anger-sadness were differentiated by HRV and theta asymmetry, while disgust-fear by N-SCR and beta asymmetry. Obtained results suggest that magnitudes of profiles of physiological variables differentiate emotions evoked by affective pictures, despite that the patterns of most responses were featured by qualitative similarity in given passive viewing context.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.110-120
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• 2000

In order to improve the vibration characteristics of mid sized passenger car automatic transmission at idle experimental and theoretical studies have been carried out. Idle shake in "D" range occurs by various reasons such as characteristics of body bending resonance between subsystems and engine mounts etc. Using full vehicle finite element analyses and modal tests we introduce the way to reduce the idle shake in the early design stage. It shows that the exciting forces are the 2nd order torque and force of engine. A powertrain system modes in "D" range are entirely effected by the additional boundary conditions of drive line. As a result the frequencies of subsystems are arranged to be lined up at the idle frequency range in order to avoid the resonances with subsystems To reduce the idle shake mounts of radiator are tuned to act as a dynamic damper to 1st bending frequency of the body. In addition a hydraulic mount which is optimized by Phase Shift Method is applied to the rear engine mount.e rear engine mount.

• 한국재료학회지
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• 제11권6호
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• pp.477-482
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• 2001

쐐기형 전극 사이에 열처리전 비정질 ($Fe_{1-x}$ $Co_{x}$ )$_{89}$ $Zr_{ 11}$ (x=0~1.0) 자성막이 증착된 MSAW 소자를 구성하고 외부 인가자기장에 의한 MSAW 속도변화율을 조사하였다. 그 결과 MSAW 속도변화율은 직류 인가자기장, 구동주파수, 자성막의 두께 및 조성에 민감하게 의존하였으며, 특히 구동주파수 및 자성막의 두께가 증가할수록 증가함을 확인하였다. 열처리전 시편에서 나타난 최대 속도변화율은 x=0.8에서 얻어진 0.062%였다.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권3호
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• pp.77-80
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• 2003

An innovative ozonizer has been developed using a high frequency, surface discharge and a high purity Ti-Si-AI ceramic catalyst as a dielectric component. Using a type of thin film, a thin cylindrical compound ceramic catalyst layer was adhered to the outside surface of its inner electrode. An alternating current (AC) exciting voltage with frequencies from 0.6 KHz to 1.0 KHz and peak-to-peak voltages of 4-6 ㎸ was applied between the electrodes to produce a stable high-frequency silent discharge. A substantial reduction of the exciting voltage was also enabled by means of a thin Ti-Si-Al ceramic catalyst tube. As a result, the ozonizer can effortlessly obtain the required ozone concentration (50-60 g/$m^2$ for oxygen) and high ozone efficiency consumption power (180 g/kWh for oxygen) with-out the assistance of any particular methods. For purposes of this experiment, oxygen gas temperature was set at 2$0^{\circ}C$, with an inner reactor pressure of 1.6 atm at 600 Hz and a flow rate of 2 l/min.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.266-270
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• 2006

Noise reduction the noise of a high precision multi-stage gearbox applied at the industrial robot is investigated by experiment such as the modal test and the signal analysis. The signal analysis performed with the waterfall plot representing the power spectrum as a function of the rotating speed. An eccentric load is installed at the gearbox in order to organize similar condition used in the industrial robot. Exciting sources are found out by the waterfall plot, and then the main factor to make the noise is distinguish. For the low-noise gearbox, the gear design parameter is modified and this gearbox is experimented in the same procedure. The results of the test show the noise level of gearbox reduced.