• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.643-644
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• 2010

• 한국콘텐츠학회논문지
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• 제19권12호
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• pp.517-526
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• 2019

본 연구는 자동노출제어장치 사용 시 파라미터 조합에 따른 영상 화질과 방사선 출력을 분석하여 임상에 적용할 수 있는 최적의 방법을 모색하고자 하였다. 실험방법은 관전압 70, 81 kVp와 자동노출제어장치(Automatic Exposure Control, AEC)의 감도 S200, S400, S800, S1000을 조합해서 복부와 골반부의 입사표면선량, 관전류량, 신호 대 잡음비(Signal to Noise Ratio, SNR), 대조도 대 잡음비(Contrast to Noise Ratio, CNR), 시간-방사선량 곡선을 구하였다. 그 후 영상 화질과 출력의 안정성을 평가하였다. 그 결과 입사표면선량, 관전류량, 신호 대 잡음비, 대조도 대 잡음비는 관전압과 감도가 높게 설정될수록 감소하였다. 또한 관전압과 감도가 높게 설정될수록 시간-방사선량 곡선은 출력의 안정성이 줄어드는 양상을 보였다. 결론적으로 복부와 골반부 검사 시 관전압과 감도를 높게 조합할수록 검출기는 영상 화질과 방사선 출력을 정상적으로 재현해내지 못하였다. 따라서 비교적 낮은 관전압과 감도를 조합하여 검출기가 파라미터의 조합을 인식할 때 발생하는 오차 범위를 최소화해야 영상 화질과 방사선 출력의 안정성을 최적화할 수 있다는 것을 알 수 있었다.

• 한국산업보건학회지
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• 제28권4호
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• pp.382-392
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• 2018

Objective: Allergic diseases such as asthma due to fungal exposure in houses have increased, and proper management is urgent. Mold can grow in the air, floor, walls, and other areas according to environmental conditions, and there are many limitations to the conventional methodology for examining fungal exposure. For this reason, the degree of fungal contamination is being evaluated by ERMI (Environmental Relative Moldiness Index), a quantitative analysis method proposed by the EPA. In this study, we compared ERMI values between water-damaged dwellings and non-damaged ones to evaluate the effectiveness of Korean ERMI values. We also explored the association of ERMI values with the level of airborne mold and characteristics of dwellings. Methods: Floor dust was collected after installing a Dustream collector on the suction port of a vacuum cleaner. The collected samples were filtered to remove only 5 mg of dust, and DNA was extracted using the FastDNA SPIN KIT protocol. Results: The ERMI values were found to be 19.6 (-6.9-58.8) for flooded houses, 7.5 (-29.2-48.3) for leaks/condensation, and 0.8 (-29.2-37.9) for non-damaged dwellings. The airborne concentration of mold for flooded, leakage or condensed, and non-damaged houses were $684CFU/m^3$, $566CFU/m^3$, and $378CFU/m^3$, respectively. The correlation between ERMI values and the levels of airborne mold was low (R = 0.038), but a weakly significant association of the ERMI values with the concentration of particulate matter ($PM_{10}$) was observed as well(R=0.231,P<0.05). Conclusions: Our findings show that the reference value using ERMI can be used to distinguish water-damaged and non-damaged dwellings. It is believed that ERMI values could be a promising tool for assessing long-term fungal exposure in dwellings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.366-371
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• 2004

For the reduction and efficient management of railway noise, first of all prediction of railway noise is necessarily requisted. At home and abroad many studies for prediction of raiiway nearby noise have been accomplished. But it is impossible to predict easily and exactly for the Korean Railway, because the acoustic powers for each rolling stock operated in Korea have not been built yet. So in this study, prediction model equation for environmental noise for Korean rolling stock Mugungwha was suggested using SEL of engine and rolling noise component separately. In this prediction model, the number of car, distance from the rail can be considered. Finally for the validation of prediction nlodel equation, the predicted Leq was compared to the measured Leq.

• 한국소음진동공학회논문집
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• 제16권2호
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• pp.156-162
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• 2006

For the reduction and efficient management of railway noise, first of all prediction of railway noise is necessarily requisited. Many studies for prediction of railway nearby noise have been accomplished. But it is impossible to predict easily and exactly for the Korean Railway, because the acoustic powers for each rolling stock operated in Korea have not been built yet. So in this study, Prediction model equation for environmental noise for Korean rolling stock Saemaeul was suggested using SEL of engine and rolling noise component separately. Finally for the validation of prediction equation, the predicted result was compared to the measured.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.371-376
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• 2005

For the reduction and efficient management of railway noise, first of all prediction of railway noise is necessarily requisited. Many studies for prediction of railway nearby noise have been accomplished. But it is impossible to predict easily and exactly for the Korean Railway, because the acoustic powers for each rolling stock operated in Korea have not been built yet. So in this study, prediction model equation for environmental noise for Korean rolling stock Saemaeul was suggested using SEL of engine and roiling noise component separately. Finally for the validation of prediction equation, the predicted result was compared to the measured.

• Safety and Health at Work
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• 제3권2호
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• pp.130-139
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• 2012

Objectives: The purpose of this study is to evaluate the tire manufacturing work environments extensively and to identify workers' exposure to hazardous substances in various work processes. Methods: Personal air sampling was conducted to measure polycyclic aromatic hydrocarbons, carbon disulfide, 1,3-butadiene, styrene, methyl isobutyl ketone, methylcyclohexane, formaldehyde, sulfur dioxide, and rubber fume in tire manufacturing plants using the National Institute for Occupational Safety Health Manual of Analytical Methods. Noise, carbon monoxide, and heat stress exposure were evaluated using direct reading instruments. Past concentrations of rubber fume were assessed using regression analysis of total particulate data from 2003 to 2007, after identifying the correlation between the concentration of total particulate and rubber fume. Results: Workers were exposed to rubber fume that exceeded 0.6 mg/$m^3$, the maximum exposure limit of the UK, in curing and production management processes. Forty-seven percent of workers were exposed to noise levels exceeding 85 dBA. Workers in the production management process were exposed to $28.1^{\circ}C$ (wet bulb globe temperature value, WBGT value) even when the outdoor atmosphere was $2.7^{\circ}C$ (WBGT value). Exposures to other substances were below the limit of detection or under a tenth of the threshold limit values given by the American Conference of Governmental Industrial Hygienists. Conclusion: To better classify exposure groups and to improve work environments, examining closely at rubber fume components and temperature as risk indicators in tire manufacturing is recommended.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.283-288
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• 2022

Purpose: This study was conducted to measure the radiation exposure and image quality of various cone-beam computed tomography (CBCT) machines under common clinical conditions and to analyze the correlation between them. Materials and Methods: Seven CBCT machines used frequently in clinical practice were selected. Because each machine has various sizes of fields of view (FOVs), 1 large FOV and 1 small FOV were selected for each machine. Radiation exposure was measured using a dose-area product (DAP) meter. The quality of the CBCT images was analyzed using 8 image quality parameters obtained using a dental volume tomography phantom. For statistical analysis, regression analysis using a generalized linear model was used. Results: Polymethyl-methacrylate (PMMA) noise and modulation transfer function (MTF) 10% showed statistically significant correlations with DAP values, presenting positive and negative correlations, respectively (P<0.05). Image quality parameters other than PMMA noise and MTF 10% did not demonstrate statistically significant correlations with DAP values. Conclusion: As radiation exposure and image quality are not proportionally related in clinically used equipment, it is necessary to evaluate and monitor radiation exposure and image quality separately.

• Journal of Oral Medicine and Pain
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• 제35권1호
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• pp.49-59
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• 2010

본 연구는 단기간의 인공소음과 음악 청취에 대한 저작근의 반응을 조사하였다. 연구의 가설은 높은 소음은 작은 소음이나 음악에 비하여 저작근의 경도는 높이고 탄성도는 감소시킨다는 것이다. 15명의 지원자에게 60 dB 과 100 dB 의 소음과 음악을 각각 6분씩 들려주고 청취 전과, 청취 2분후, 4분후, 6분후에 tactile sensor system을 이용하여 교근과 측두근의 경도 및 탄성도를 조사하였다. 첫째날은 100 dB의 소음, 둘째날은 100 dB 의 음악, 셋째날은 60 dB 의 소음, 넷째날은 60 dB 의 음악을 청취한 후 조사하였다. 실험 결과, 60 dB, 100 dB 모두에서 소음과 음악 청취군 간에는 유의성 있는 차이가 대부분 없었으며, 60 dB, 100 dB군간의 비교에서 측두근에서는 유의한 차이가 없었으나 교근의 경우, 음악군에서는 탄성도에서, 소음군에서는 경도에서 유의한 차이를 보여주었다. 이는 소음의 종류에 관계없이 비록 음악이고 단기간의 청취일지라도 큰 소음인 경우에는 저작근의 수축을 야기할 수 있음을 의미한다.

• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.21-32
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• 2015

We have carried out photometric follow-up observations of bright transiting extrasolar planets using the CbNUOJ 0.6 m telescope. We have tested the possibility of obtaining high photometric precision by applying the telescope defocus technique, allowing the use of several hundred seconds in exposure time for a single measurement. We demonstrate that this technique is capable of obtaining a root-mean-square scatter of sub-millimagnitude order over several hours for a V~10 host star, typical for transiting planets detected from ground-based survey facilities. We compared our results with transit observations from a telescope operated in in-focus mode. High photometric precision was obtained due to the collection of a larger amount of photons, resulting in a higher signal compared to other random and systematic noise sources. Accurate telescope tracking is likely to further contribute to lowering systematic noise by exposing the same pixels on the CCD. Furthermore, a longer exposure time helps reduce the effect of scintillation noise which otherwise has a significant effect for small-aperture telescopes operated in in-focus mode. Finally we present the results of modelling four light-curves in which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes was achieved.