• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.419-423
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• 2000

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.649-655
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• 1997

본 논문은 항공기의 외부소음 중 엔진에 의한 소음의 전방으로의 방사에 대한 연구이다. 우선 엔진소음의 소음원을 살펴보고 주된 소음원인 압축기/팬 소음을 Tyler & Sofrin의 논문에 의해서 모델한 후 FEM을 이용하여 내부 음원에 의한 외부의 방사음압을 해석하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.432-433
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• 2013

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.623-624
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• 2013

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.421-432
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• 2019

In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structure-borne noise of the viaduct box girder is mainly caused by $16^{th}$ and $62^{th}$ vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.

• 대한의용생체공학회:의공학회지
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• 제28권6호
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• pp.756-767
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• 2007

For the combination of phosphor screens having various thicknesses and a photodiode array manufactured by complementary metal-oxide-semiconductor (CMOS) process, we report the observation of image-quality degradation under the irradiation of 45-kVp spectrum x rays. The image quality was assessed in terms of dark pixel signal, dynamic range, modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). For the accumulation of the absorbed dose, the radiation-induced increase both in dark signal and noise resulted in the gradual reduction in dynamic range. While the MTF was only slightly affected by the total ionizing dose, the noise power in the case of $Min-R^{TM}$ screen, which is the thinnest one among the considered screens in this study, became larger as the total dose was increased. This is caused by incomplete correction of the dark current fixed-pattern noise. In addition, the increase tendency in NPS was independent of the spatial frequency. For the cascaded model analysis, the additional noise source is from direct absorption of x-ray photons. The change in NPS with respect to the total dose degrades the DQE. However, with carefully updated and applied correction, we can overcome the detrimental effects of increased dark current on NPS and DQE. This study gives an initial motivation that the periodic monitoring of the image-quality degradation is an important issue for the long-term and healthy use of digital x-ray imaging detectors.

• 항공우주시스템공학회지
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• 제16권3호
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• pp.73-83
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• 2022

본 논문에서는 항공기 운영 중에 RF 방사 신호로 인하여 발생한 특정 주파수 대역 대의 수신 잡음에 대한 개선 방안을 연구하였다. 항공기의 통신장비는 내/외부통신의 기능을 담당하기에 비행 임무 수행과 안전에 있어서 매우 중요하다. 잡음이 없고 깨끗한 통신 품질과 송/수신 기능이 구현되어야 한다. 따라서 특정 주파수 대역 대의 수신 잡음 현상을 고장탐구를 통해 원인분석을 하였다. 항공기 내부의 특정 보조시스템 장비에서 발산되는 RF 방사 신호로 인해 발생한 수신 잡음을 무전해 니켈 도금이 적용된 CAP으로 차폐하여 개선하였다. 또한, 개선 방안에 대한 측정 및 검증 결과도 함께 기술하였다.

• 한국해양공학회지
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• 제26권4호
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• pp.30-36
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• 2012

Recently, the underwater radiated noises generated from large commercial ships have become a globally important issue. Countries with large ports and environmental protection organizations demand strict safety guidelines in relation to underwater radiated noise. In this paper, the coupled PFFE/PFBE method is used to investigate the vibration and underwater radiated noise of a commercial ship. PFFEM is employed to analyze the vibrational responses of the commercial ship, and PFBEM is applied to analyze the underwater radiation noise. The vibrational energy of the structure is treated as an acoustic intensity boundary condition of PFBEM to calculate the underwater radiation noise. Numerical simulations are presented for the commercial ship under various frequencies, and reliable results are obtained.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1503-1510
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• 2020

Ultra-low noise charge sensitive amplifiers (CSAs) based on various types of circuit board substrates, such as FR4, Teflon, and ceramics (Al₂O₃) with two different designs, PA1 and PA2, have been developed. They were tested to see the noise effect from the dielectric loss of the substrate capacitance before and after irradiation. If the electronic noise from the CSAs is to be minimized and the energy resolution enhanced, the shaping time has to be optimized for the detector, and a small feedback capacitance of the CSA is favorable for a better SNR. Teflon- and ceramic-based PA1 design CSAs showed better noise performance than the FR4-based one, but the Teflon-based PA1 design showed better sensitivity than ceramic based one at a low detector capacitance (<10 pF). In the PA2 design, the equivalent noise and the sensitivity were 0.52 keV FWHM for a silicon detector and 7.2 mV/fC, respectively, with 2 ㎲ peaking time and 0.1 pF detector capacitance. After 10, 100, 10³, 10⁴, and 10⁵ Gy irradiation the ENC and sensitivity characteristics of the developed CSAs based on three different substrate materials are also discussed.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.90-98
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• 2011

Noises from diesel engine are the major issues for noise pollution as well as affect customers' purchasing needs to vehicles powered by diesel engine. This study investigates to screen-out main factors that contribute to noises from diesel engine using VGT 2000cc engine developed recently. Changes of fuel temperature, intake temperature and the presence of three way catalyst don't affect the 'Engine Radiation Noise' and the solely three way catalyst influence on the 'Tail Pipe Noise'. Especially, there are no effects of the presence of three way catalyst on torque, which is main subject that should be considered in secondary study.