• 한국소음진동공학회논문집
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• 제17권6호
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• pp.491-497
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• 2007

Reasonably accurate estimation of the exposed population to the distinct levels of noise is essential to the efficient management of urban environmental noise. This study proposes a method of calculating the number of exposed people to industrial noise by using GIS tool and noise mapping. The exposed population of noise based on estimation of the number of people that lived in each building in urban area is compared with the one based on density of population. This study suggests the five step method that consists of gathering the fundamental data, extracting the property from the digital map, noise mapping based on the three dimensional topography, estimating population that lives in each building, merging the various results with GIS tool, and estimating exposed population to industrial noise through analyzing the noise map with GIS tools.

• 한국소음진동공학회논문집
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• 제12권5호
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• pp.317-322
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• 2002

A solution procedure of vibration and radiated noise of the plate covered with damping material has been studied. To predict the vibration level and the radiated noise level of the plate covered with damping material, FEM and BEM have been utilized, respectively. A property of damping material has been measured by using a composite beam. Two different kinds of measuring procedure for the composite beam have been introduced by comparing its characteristics. The numerical prediction of vibration level of the Plate covered with damping material has been proved with experimental data.

• 전자공학회논문지
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• 제54권3호
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• pp.63-69
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• 2017

NNPS(normalized noise power spectrum)는 획득한 x선 영상에서 평판형 방사선 디텍터의 잡음 특성을 spectrum을 관찰하기 위해 측정한다. 그러나 NNPS 측정은 획득한 영상에 따라 일관적이지 못한 성질을 가지고 있어서 안정된 측정이 필요하다. 디텍터의 NNPS 측정은 표본 periodogram을 구하여 평균을 내는 방법을 사용하는데, 일반적으로 표본의 개수를 충분히 늘리면 정확하면서 안정된 값을 구할 수 있다. 본 논문에서는 periodogram과 같은 표본 spectrum의 평균으로 유한한 개수의 영상이 주어졌을 때 일관적이고 효율적인 NNPS 값을 제공 할 수 있는 두 가지 방법을 제안하고 그 성능을 비교하고 분석했다. 실제 두 종류의 방사선 디텍터로부터 획득한 x선 영상을 사용하여 제안한 방법을 실험하였으며, 주어진 영상을 사용하여 표본 spectrum의 최대 가지 수를 갖는 조합으로 NNPS를 구하고 평균을 내는 방법이 기존 방법에 비하여 안정된 NNPS 측정이 가능함을 보였다.

• 환경영향평가
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• 제26권1호
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• pp.11-26
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• 2017

철도 소음의 환경영향평가 업무에 있어서 소음도에 대한 정확한 예측이 중요하지만, 국내에서는 overall 소음도의 거리별 측정을 통한 경험식이 근사적으로 이용되고 있다. 본 논문에서는 소음원과 소음전파의 주파수 특성을 고려하여 철도 소음의 예측 정확도를 향상할 수 있는 예측 모델을 제안하였다. 먼저 철도 소음원을 궤도(레일 및 침목), 차륜, 동력, 공력 성분으로 구분하여 각각의 옥타브 밴드 주파수별 음향파워와 속도계수를 정의하고 음향 조도와 궤도/교량 특성을 반영할 수 있는 보정항을 도입하였다. 소음원에서 수음점까지의 전파 특성은 ISO 9613-2를 적용하여 기하학적 확산, 대기 흡음, 지면 효과, 장애물의 회절에 따른 감쇠 및 지향특성을 반영하여 계산하였다. 소음원 음향파워와 지향인자를 추정하기 위하여 전동 소음원 해석 모델 및 수치해석 결과와 통과 소음도 측정값을 이용하였다. 본 철도 소음 예측 모델을 이용하여 여러 철도 차량과 궤도 유형에 따라서 예측한 소음도를 측정값과 비교하여 정확도를 검증하였으며 기존 예측 모델보다 비교적 정확한 예측이 가능하였다. 따라서 본 결과는 철도 환경 소음의 정확한 영향 예측과 효율적인 소음 저감 대책 수립에 활용될 수 있을 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.227-230
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• 2005

The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

• 한국소음진동공학회논문집
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• 제13권8호
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• pp.626-636
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• 2003

The beat distribution property of the King Seong-deok Divine Bell is investigated by experiment and analysis. The beat map method is proposed to explain the beat distribution property on the circumference of the bell. For the analytical investigation, an analytical model of the vibration beat is derived on a slightly asymmetric shell of revolution by using the modal expansion method. In the analytical method, the beat map can be drawn only if the modal parameters of the bell are obtained. The analytical beat model is applied to draw the beat map of the King Seong-deok Divine Bell. The validity of the analytical method is verified by comparing the analytical beat maps with the experimental results. This paper proposes a visualization method of the beat and theoretically identifies the reason why the clear and unclear beats repeat periodically along the circumference of the bell and how the striking position influences the beat distribution property.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1185-1191
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• 2008

This paper presents an approach to define an optimal piezoactuator length to actively control structural vibration. The optimal ratio of the piezoactuator length against the beam length when a pair of piezoceramic actuator and accelerometer is used to suppress unwanted vibration with direct velocity feedback(DVFB) control strategy is not clearly defined so far. It is well known that DVFB control can be very useful when a pair of sensor and actuator is collocated on structures with a high gain and excellent stability. It is considered that three different collocated Pairs of piezoelectric actuators (20, 50 and 100 mm long) and accelerometers installed on three identical clamped-clamped beams($30{\times}20{\times}1mm$). The response of each sensor-actuator pair requires strictly positive real(SPR) property to apply a high feedback gain. However the length of the piezoactuator affects the SPR property of the sensor-actuator response. Intensive simulation and experiment show the effect of the actuator length variation is strongly related with the frequency range of the SPR property. Thus an optimal length ratio was suggested to obtain relevant performance with a good stability under the DVFB strategy.

• 한국소음진동공학회논문집
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• 제15권11호
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• pp.1262-1267
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• 2005

The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet Is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness Properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

• 산업기술연구
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• 제22권A호
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• pp.43-48
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• 2002

Acoustic modes of a vehicle compartment dominate the noise characteristics of the vehicle system in the low frequency range. Vehicle compartments have head liner and air gap of proper thickness to mount a interior lamp, as well as to have a good sound insulation and absorption performance. This study estimates the acoustic modal property of the medium size passenger car by experiment and by finite element analysis and also, investigates the effect of the head liner on the acoustic mode of the passenger compartment to obtain useful information for low noise compartment design.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.350-355
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• 2005

This paper presents a new approach for hysteresis modeling of a magnetorheological (MR) fluid. The field-dependent hysteresis of MR fluid is investigated using the Preisach model. The commercial MR Product (MRF-132LD, Lord Corporation) is employed. Its field-dependent shear stress is then obtained using a rheometer (MCR 300, Physica). In order to show the applicability of the Preisach model to the MR fluid, two significant Properties; the minor loop property and the wiping-out property are experimentally examined. Subsequently, the Preisach model for the MR fluid is identified using experimental first order descending (FOD) curves in discrete manner. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one. In addition, the hysteresis model proposed in this work is compared to Bingham model.