• Corrosion Science and Technology
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• 제9권2호
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• pp.57-66
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• 2010

Since nuclear power plants are being operated under high temperature and high pressure, on-line monitoring technique to detect corrosion could be more effective than off-line method in shut-off period. In this operating condition, electrochemical noise method may be suitable to monitor the corrosion. This paper aims the analysis on the relation between the cracking and electrochemical noise signal of Alloy 600 under U-bending. When electrochemical noise monitoring technique was used during SCC test, it was judge to be obvious that if cracks generate, its generation can be detected by electrochemical current noise. Cracking-related noise was defined as the noise showing 5~10 times greater than the average value of background noise bands. On the base of crack noise, crack initiation time was determined. From SCC test and electrochemical noise monitoring in $25^{\circ}C$, 0.1 M $Na_2S_4O_6$ solution (Reverse U-Bended Alloy 600 SE+), average crack initiation time was obtained as 9,046 seconds and from its initiation time, it could be defined that net crack propagation rate is the crack length divided by ${\Delta}T$(= total test period - crack initiation time). Therefore, average net crack propagation rate was obtained to be $1.18{\times}10^{-9}\;m/s$.

• 한국방사선학회논문지
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• 제16권4호
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• pp.395-403
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• 2022

본 연구에서는 디지털방사선영상 시스템에 사용되는 평판형 검출기(flat-panel detector, FPD)를 이용하여 조직 등가 물질인 폴리메틸메타아크릴레이트(Polymethyl Methacrylate, PMMA)의 두께 변화에 따라 발생되는 산란선이 영상품질의 영향으로서 해상력 평가의 변조전달함수(modulation-transfer function, MTF)와 잡음력 스펙트럼(noise-power spectrum, NPS)으로 정량적인 영상 평가를 위한 연구를 수행하였다. 해상력-차트 팬텀 영상으로 PMMA 두께가 증가할수록 산란선의 영향이 커져 변조특성이 저하 되는 것을 알 수 있고 영상이 밝다. 결과는 영상의 잡음이 많아진다는 것을 알 수 있는데 공간주파수 별로 확인하기 위해 푸리에 변환으로 잡음력 스펙트럼 영상을 얻었다. 그러므로 영상에서 피사체로서 PMMA 두께 증가에 따라 산란선의 변화를 MTF로 평가하여 해상도 특성변화와 2차원 잡음력 스펙트럼을 1차원 값으로 나타낸 결과를 통해 PMMA 두께와 잡음은 비례하는 것을 확인할 수 있다.

• 대한전자공학회논문지TC
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• 제37권4호
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• pp.17-24
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• 2000

통신을 위한 채널로써 전력선을 활용하기 위해서, 전력선상에서 존재하는 잡음을 측정하여 잡음 데이터를 획득하고, 망구조에 따른 단위길이(100m당)에 따른 신호 감쇄량을 측정했다. 본 논문에서 구분한 3종류의 전력선 구조에 따른 신호 감쇄와 잡음의 최대, 최소값을 이용해서 채널 용량식에 대입한 후 통신 채널로써 전력선이 가지는 채널용량을 계산하였다. 건물내 전력선이 가지는 채널용량은 전력선에 있어서 송,수신기 사이의 거리와 전력선 망구조에 영향을 크게 받는 것으로 나타났다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.223-226
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• 2007

This paper first outlines the technology used in Power Line Communications(PLC) systems, and the political support being offered to the technology, from the point of view of its effect on electromagnetic compatibility (EMC). The radio spectrum needs protection from other interferers, and there is a regime in place to provide this interference avoidance/mitigation. Nevertheless, PLC has several features that mean that it is capable of creating such interference. These features are discussed, and some published field trial results are reviewed. Difficulties in achieving compatibility between the requirements for radio protection and the requirements for operation of the PLC system mean that there is no consensus as yet as to how PLC system components can be made compliant with EMC requirements. It is concluded that there is little prospect of an accommodation between the competing demands, so that if PLC is to become widespread it will be at the expense of the radio environment.

• 소음진동
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• 제6권3호
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• pp.349-355
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• 1996

For a rail traffic noise, a typical source has a length of 200m - 400m so that the noise pollution areas have been located in the transition regions where the sound level drops between 3dB/dd and 6dB/dd. Therefore, in this region, parameters such as a horizontal distance from the track, the geometry of the ground surface, the environmental effect, and the boundary impedance condition play import roles, especially in our nation's situation. In this study, modelling techniques for the finite length of noise source have been investigated in order to evaluate the rail traffic noise level. Then. noise correction value .${\Delta}$SPL for various location in the track region is represented by the non-dimensionalized horizontal and parallel distance from the track. As an application, a high speed train is examined. Beas on the noise data measured for a Eurostar in France, the sound power value per unit length $H_1$is calcuated. It turns out that$H_1$is 109 dB. Overall sound power from the highspeed train to be serviced in our country is expected to 135 dBA.

• ETRI Journal
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• 제38권1호
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• pp.1-8
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• 2016

A large incoherent crosstalk (IC) caused by amplified spontaneous emission (ASE) noise power from Tx-disabled optical network units and a differential path loss has been shown to degrade upstream transmission performance in time-division multiplexing passive optical networks. This paper considers the IC-induced power penalty of an upstream signal both in an XG-PON and in a TWDM-PON. We investigate the degradation of the extinction ratio and relative intensity noise through a simulation and experiments. For the XG-PON case, we observe a 9.6 dB difference in the level of ASE noise power from Tx-disabled ONUs (hereafter known simply as ASE noise) between our result and the ITU-T XG-PON PMD recommendation. We propose an optical filtering method to mitigate an IC-induced power penalty. In the TWDM-PON case, the IC-induced power penalty is naturally negligible because the ASE noise is filtered by a wavelength multiplexer at the optical line terminal. The results provide design guidelines for the level of ASE noise in both XG-PONs and TWDM-PONs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.527-532
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• 2014

Generator is the main equipment of a power plant that generates electric power. The line frequency is 60Hz, since that is operated at 3600rpm in fossil power plant. Therefore, the specific frequency 120Hz by the electromagnetic excitation force is generated inherently. If the looseness of stator at generator happens, abnormal sound that has 120Hz and the harmonic frequency is emitted from generator frame. In that case, binding of end-winding or re-wedging is needed for the reduction of sound level. In case of severe level of sound, belly band can be additionally installed at core. In this paper, the characteristics of generator sound is described and modal data is analyzed after installation of belly band.

• 한국환경보건학회지
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• 제34권2호
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• pp.153-160
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• 2008

Personal noise exposure was assessed in railroad operators working in 40 operation units including the Gyeongbu line, Honam line, and Janghang line between 2004 and 2006. 8-hour TWA were assessed based on the MOL (Ministry of Labor) guideline on noise evaluation, and 17% of these measurements exceeded 85 dBA while 70% were over 80 dBA. When the ACGIH TLV is adopted, 40% of measurements were over TLV (85 dBA). The noise exposure risk of railroad operators was higher for diesel locomotive operation and longer operational distances; in addition, the risk was higher for passenger car operation compared to freight car driving. Given that in Korea, over the past 30 years diesel locomotives have provided most of the railway's motive power and that hearing protective equipment is not likely to be used by workers during operation, railroad operators are at a high risk of noise-induced hearing loss. The result of audiometric test among 568 railroad operators showed that 32.6% of those tested had a hearing threshold shift of more than 40 dB. In conclusion, this study calls for more fundamental measures including noise control countermeasures within the operation areas, development of equipment that generates less noise and adopting limitation on the operation distance for a work shift.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1142-1147
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• 2002

For the evaluation of the DC motor noise and vibration, usually it is rely on human feeling because some kinds of noise are not definitely represented by measurement Instrument such as sound meter. But when we consider time signal of the noise and vibration. It is possible to represent them. And in this paper. it is suggested to study output current shape of the motor because it Is the source to make speed and torque variation of the motor. If the current shape is not stable. it makes operating state of the motor unstable and produces noise and vibration. By analyzing signal at time and frequency of noise and vibration and current shape. it is possible to automation of the noise and vibration measurement in the Production line.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2147-2150
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• 2003

Recently, many technologies of the P.L.C (Power Line Carrier) are introduced for an efficient communication. P.L.C communication sends information in the carrier signals by conduction over the power wire. An arc detector is proposed in this paper for the effective transmission. The Power Line Carrier has an advantage in low cost because it uses existent power line. It can be easily applied anywhere that a power line socket is available. But the P.L.C. is very noisy, because many electronic devices in generate electronic noise in modulated signals. This problem should be considered carefully in the design of the arc detector system using P.L.C in railway. The proposed system can be applied for monitoring the arc detector system and the arc locator system in railway. Hence the system will be able to exchange the arc information to be T.C.M.S. (Train Control Management System), bogies and even between a station and trains in railway and use to suspicion fire in train.