• 한국산업보건학회지
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• 제15권3호
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• pp.202-212
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• 2005

This study was aimed at rating the existing work environment noise components and alternatives in point of worker's view. To answer the purpose, AHP(Analytic Hierarchy Process) method is adopted in this research. Based on the AHP method, this research abstracts a mathematically rigorous noise components and alternative's weights and proven process for priority and decision-making. By reconstructing complex hearing conservation programs to a series of pair-wise comparisons, and then synthesizing the results, this study not only helps establishments of noise countermeasure, but also provides a clear rationale for noise alternatives. The result of this study is summarized as follows; 1) Job satisfaction index and noise identification index are 63, 56 respectively. 2) Noise level(15.7%), frequency(14.1%) and directivity(13.6%) are main reasons in worker's ground. 3) There are some difference between the estimation of worker's identification and that of work sites. 4) Low noise machine(14.7%), enclosure(13.2%) and shielding(9.6%) are chosen for noise protection method by workers. 5) Noise environment improvement should be focused on noise source rather than personal protection. 6) By the AHP method, noise source countermeasure have a key role at work environments.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.6-11
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• 2007

Packaged power station (PPS) is a stationary diesel engine generator set and developed for the supply of electric power to small villages, islands and factories etc. Therefore, the PPS is closely installed to residence area and sometimes cause the environmental noise problems. In this paper, environmental noise analysis was performed for the power plant with 28 sets of PPS. The initial analysis results showed the some difference between the measurement and analysis because of the inaccurate noise source data. To improve the accuracy of analysis, main noise sources were inversely estimated using the in-situ measurement data in the vicinity of PPS and steam boiler. As the results of re-analysis, the good agreement was obtained and it was concluded that the noise levels exceed the specified noise limit in residence area. In order to reduce the noise, the several methods such as geometry alteration of inlet duct, application of hybrid-type silencer and noise protection barrier were suggested and verified with the confirmed analysis model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.279-281
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• 1996

This paper deals with the two stage surge protection device by using varistor and LC low pass filter. Recently varistor alone has been used with overvoltage protection devices for the AC power mains and has same problems associated with high remnant voltage and noise. In this work, in order to improve the cutoff performance of surge protection device, the lightning surge protection device having two stage hybrid circuit for an AC single phase mains was designed and fabricated. Operation characteristics and surge clamping performance of the surge protection device in an $8/20{\mu}s$ surge current are investigated. As a consequence, it is found that the proposed two stage surge protective device for AC power mains has a variety of advantages such as a smaller clamping voltage, high frequency noise reduction and large clamping capacity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.454-456
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• 1987

A more specialized area of transient evaluations is transmission line fault-detecting and protection system. During the first cycle or two following a power system fault, a high-speed protective relay is expected to make a decision as to the severity or location of the fault, usually based on 60 Hz information, i.e. the phase and magnitude of 60 Hz voltage or current signals. It is precisely at this time however that the signal is badly corrupted by noise, in the form of a de offset or frequencies above 50 Hz. One of several possible sources of transients in protection measuring signals is in the primary system for which protection is required in its response to the impact of short circuit fault on-set. Other sources are in the primary voltage and current transducers from which protection signals are derived, and, often of particular importance, in the interface circuits between the transducer secondaries and the comparator and measuring elements of the protection system. However, the noise signals that will be described in this paper are due to the main power system only and do not include errors due to current or voltage transducers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.220-223
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• 2007

Acoustic test of the payload fairing of Korea satellite launch vehicle was conducted to verify the performance of acoustic protection system installed inside the payload fairing. This paper briefly introduces the acoustic test procedures and its results. Overall 148 dB acoustic loads were exerted on the payload fairing structures which mated with the upper stage structure of the launch vehicle. In order to verify the increase of insertion loss by the acoustic protection system, two kinds of test were performed. One is conducted with acoustic protection system and the other without acoustic protection system. Internal acoustic loads as well as external ones were measured and the measured insertion losses were compared with the requirement. The results showed that the acoustic protection system increases the insertion loss by more than 6 dB above 125 Hz. They also indicated that some design modification of Helmholtz resonator array is required to increase the insertion loss at a cavity resonant frequency.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.480-483
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• 2000

We developed a home electric panel board with surge protection device to protect home electric appliances from transient overvoltages and electromagnetic(EM) noise. In this paper, electrical characteristics of the home electric panel board are described. From the performance test using a combination surge generator standardized in IEC 610004-5, it is confirmed that the proposed home panel board has an excellent surge protection performance. Also, EM noise reduction characteristics of the panel board in ranges from 150 kHz to 30 MHz is estimated by using a network analyser, and the results showed that the panel board has an over 20 45 noise reduction performance.

• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.160-169
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• 2021

Background: Dual-energy X-ray images (DEI) can distinguish or improve materials of interest in a two-dimensional radiographic image, by combining two images obtained from separate low and high energies. The concepts of DEI performance describing the performance of double-exposure DEI systems in the Fourier domain been previously introduced, however, the performance of double-exposure DEI itself in terms of various parameters, has not been reported. Materials and Methods: To investigate the DEI performance, signal-difference-to-noise ratio, modulation transfer function, noise power spectrum, and noise equivalent quanta were used. Low- and high-energy were 60 and 130 kVp with 0.01-0.09 mGy, respectively. The energy-separation filter material and its thicknesses were tin (Sn) and 0.0-1.0 mm, respectively. Noise-reduction (NR) filtering used the Gaussian-filter NR, median-filter NR, and anti-correlated NR. Results and Discussion: DEI performance was affected by Sn-filter thickness, weighting factor, and dose allocation. All NR filtering successfully reduced noise, when compared with the dual-energy (DE) images without any NR filtering. Conclusion: The results indicated the significance of investigating, and evaluating suitable DEI performance, for DE images in chest radiography applications. Additionally, all the NR filtering methods were effective at reducing noise in the resultant DE images.

• 조명전기설비학회논문지
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• 제15권5호
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• pp.75-80
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• 2001

본 논문에서는 플랜트에서 발생되는 각종 노이즈의 장해사례에 대한 원인 분석과 대책을 제시하였다. 이들 노이즈 장해 현상은 각종 설비들의 오동작과 소손 등을 일으키며, 그 원인은 주로 노이즈를 차단하기 위한 방호소자의 부적절한 적용과 접지계통의 다원화에 의한 전위차에 기인한 것으로 분석되었다. 따라서 이러한 문제해결을 위해 본 연구에서는 적정한 방호소자의 선정과 설치, 접지계의 단일화에 의한 등전위 구성 등으로 노이즈 문제를 해결하였다.

• 한국멀티미디어학회논문지
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• 제10권2호
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• pp.200-208
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• 2007

가장 흔한 직업병 중의 하나인 소음성 난청은 알려진 치료법이 없기 때문에 예방하는 것이 매우 중요하다. 청각보호를 위한 다양한 종류의 청각보호구가 시판되고 있으며 청각보호에도 효과가 있는 것으로 알려져 있지만, 착용 시 발생하는 의사소통의 어려움으로 인하여 많은 사용자들이 착용을 꺼리게 된다. 이러한 의사소통의 문제점을 해결하기 위해 음관의 형태를 변화시켜 소형 음향필터를 사용할 수 있다. 본 논문에서는 소형 음향필터들을 설계하였고 이의 특성을 유한요소해석을 통하여 분석하였다. 유한요소해석의 결과로써 길이와 직경에 따라 설계된 소형 음향필터의 특성을 확인하였다. 그리고 유한요소해석을 이용한 필터 모델의 일반적인 추세와 설계된 필터들의 음향적 실험과 일치함을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제6권3호
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• pp.189-195
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• 2006

In this paper, the derivation of the protection ratio for the digital microwave system with diversity is newly suggested for a basic guidance of initial planning for frequency coordination, and computational results are presented for an actual radio frequency band. The net filter discrimination has been also examined to see the effect of the adjacent channel protection ratio caused by adjacent channel interference. In addition, the protection ratios for the space or frequency diversity system are analyzed in terms of diversity improvement factors to find out an equivalent allowable noise-to-interference ratio (N/I) from degraded fade margin. According to results for 6.2 GHz system, with the space diversity of 25 m distance between antennas or the frequency diversity of ${\Delta}f/f=0.05$, under 64-QAM and 60 km at BER $10^{-6}$, the protection ratio can be greatly reduced in comparison to the non-diversity system. So, assuming that only the same protection ratio as the non-diversity system is kept, it is shown that the system with diversity may get more interference level of N/I allowing from 9.0 to - 5.9 dB or from 6.0 to - 4.3 dB for the space or frequency diversity. In consequence, it is concluded that the diversity system is more robust or tolerable for interferences or fades, which may play an important role in overcoming N/I to some extent.