• 한국소음진동공학회논문집
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• 제21권9호
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• pp.828-833
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• 2011

A reaction wheel assembly(RWA) is the largest disturbance source that can induce high frequency micro-vibration on an optical payload of satellites. To ensure a tight pointing-stability budget of satellites, the RWA disturbance effect on spacecraft should be accurately analyzed and evaluated for whole design phases. For this purpose, the micro-vibration disturbance of RWA should be precisely measured. In the present study, two measurement methods on RWA micro-vibration disturbances are compared and investigated. One is a free run-down speed test and the other is a constant speed test. The micro-vibration data measured by the two methods are analyzed in terms of spectrum characteristics, static and dynamic imbalance values, and root sum square(RSS) values. The analysis results show that both methods can measure very similar results in time and frequency domains and that the free run-down speed method is more adequate in respects to wheel friction modeling, noise rejection of imbalance and RSS peak evaluation.

• 한국도로학회논문집
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• 제14권3호
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• pp.33-39
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• 2012

배수성 포장에 있어 기능적 평가인 투수성 실험과 더불어 소음저감 측정을 서울시에서 시공한 구간에서 실시하였다. 소음측정은 두 가지 방법을 이용하였는데 그 방법은 Pass-by 방법과 NCPX(Novel Close Proximity) 방법을 이용하였다. Passby 방법은 교통량에 따른 소음원이 전달되는 것을 측정하는 방법이고, NCPX는 타어어와 포장 표면간의 마찰음을 측정하는 방법이다. 현장투수시험을 위해서는 총 5개의 구간에서 실시하였으며 각 구간마다 주행부와 비주행부로 나뉘어 측정하였다. 3개 구간의 Pass-by 측정을 위해서는 교통소음원 발생점으로부터 인접한 곳에서 측정을 실시하였고 또한 공원내부 혹은 단지 내부에서도 소음을 측정하였다. 마지막으로 NCPX 측정은 4군데서 실시하였다. 결과적으로 배수성 포장의 기능인 투수성과 소음저감이 2, 3년 사이에서는 그 기능을 잘 유지함을 알 수 있었다.

• 한국도로학회논문집
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• 제15권2호
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• pp.11-18
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• 2013

PURPOSES : This study presents the noise level and frequency characteristics investigated in the national highways with the consideration of various measuring conditions and/or methods. METHODS : The noise levels on the asphalt concrete pavement(ACP) and the jointed plain concrete pavement(JPCP) of the national highway were measured and analysed with respect to three variables, i.e., pavement type, surface condition, and measurement distance. The PASS-By method is utilized for the noise measurement and then using CPB spectrum analysis method with 1/3 octave bandwidth, the noise levels and frequency characteristics were calculated for two-second periods before and after the peak noise. RESULTS : Depending on the pavement type, the noise level was changed as the average noise levels are 73.3dB(A) and 78.3dB(A) for ACP and JPCP, respectively. With respect to the effect of surface condition, the average noise levels for crack H(high), M(medium), and L (low) sections are 77.4dB(A), 77.4dB(A), and 78.1dB(A), respectively. Regarding the measurement distance, 1.2meter difference in measuring location reduces 1.6dB(A) of noise level; the average noise levels at 5.3m and 7.5m from the centerline of outer lane are 72.8dB(A) and 71.2dB(A), respectively. It should be noted that the noise levels are slightly different as a function of vehicle speed and type. However, the overall trends for each case was similar. It was found that the domain frequency bands for ACP and JPCP were 400Hz~2000Hz and 500Hz~2000Hz, respectively. CONCLUSIONS : Based on the analysis with the measured noise date from national highway, it was concluded that the noise level and frequency band vary depending on the various conditions. It was also found that some variables significantly affect the noise level while others do not. With further systematic investigation, the comprehensive noise characteristics on the national highway can be achieved. Using such database, it is possible to develop the fundamental noise reduction technology.

• 한국산업보건학회지
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• 제28권1호
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• pp.100-107
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• 2018

Objectives: This study examines exposure to hazardous substances in the working environment caused by exposure to toxic substances produced in the aluminum die casting process in the automobile manufacturing industry. Materials and Methods: The exposure concentration levels, detection rates and time-trend of 15 hazardous factors in the aluminum die casting process over 10 years(from 2006 to 2016) were used as a database. Results: The study found that hazardous factors in the aluminum die casting process were mostly metals. The rate for detected samples was 70.6%(405 samples), and that for not detected samples was 29.4%. The noise for an eight-hour work shift showed a 49.7% exceedance rate for TLV-TWA. Average noise exposure was 89.0 dB. The maximum exposure level was 105.1 dB. Conclusion: The high numbers of no-detection rates for hazardous substance exposure shows that there is no need to do a work environment measurement. Therefore, alternatives are necessary for improving the efficiency and reliability of the work environment measurement. Moreover, to prevent noise damage, reducing noise sources from automation, shielding, or sound absorbents are necessary.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1185-1188
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• 2002

The objective of this paper is to apply experimental methods to measure the in-plane vibration intensity of a semi-infinite beam. Two experimental methods have been implemented to measure the in-plane vibration intensity of the beam. The first method is the cross spectral intensity measurement method using two accelerometers. The second method is the frequency response method using the only one acrelerometer. It has the advantages of shortening measurement time and reducing accelerometer phase error. Experimental results showed that those experimental methods can be effectively used to measure the structural In-plane vibration intensity.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.199-201
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• 2011

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.300-301
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• 2011

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.533-538
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• 1997

본 논문에서는 이미 연구된 여러 홀로그램 측정 방법을 비교하여 그 장단점에 대해 고찰하였다. 이동 프레임 방법의 실제 응용, 실질적인 적용에서의 탁월성을 상대적으로 확인하기 위해서 기존의 이동 음원 가시화 방법들과의 비교 또한 시도하였으며 결과를 이 논문에 정리하였다.

• 정보처리학회논문지C
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• 제12C권4호
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• pp.519-524
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• 2005

동하중 측정 데이터에 추가되는 여러 가지 종류의 오차로 인하여, 신뢰할 수 있는 하중을 구하기 위해 측정 오차를 감소시키는 적절한 방법이 필요하다. 과도한 진동으로 인해 발생하는 측정 오류는 쉽게 제거하기 어렵다. 이러한 오류를 최소화하기 위하여 측정 장치 혹은 측정 대상의 수직 운동과 상호 관계가 전혀 없는 광 센서 시스템을 이용한다. 여러 가지 시료들의 흐름률을 광 센서를 이용하여 측정함으로써 로드셀을 이용한 부정확한 측정 부분을 보완한다. 동하중 측정시 발생하는 잡음 감소를 확인하기 위하여 모형 트레일러 시스템을 사용하며, 제안된 방법이 효과적임을 확인한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.358-362
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• 2002

The HDD unbalance, with higher rotational speed, is directly influenced by the mechanical assembly allowance between clamping disk and platter disk. The low frequency structural vibration induced by the unbalance force finally gives rise to the structure borne noise of the personal computer. To meet the noise and vibration requirements, the absolute unbalance mass of HDD needs to be measured and adjusted in the disk assembling stage. This study introduces the measurement methods of the absolute magnitude and position of the unbalance mass of HDD based on the mobility and acceleration orbit. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass ran be obtained by the rotation acceleration orbit.