• 한국산업보건학회지
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• 제25권4호
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• pp.573-583
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• 2015

Objectives: This study was carried out to evaluate the effect of noise exposure and aging on changes in hearing threshold level and the relationship between age and noise. Materials: The author selected 274 male shipyard and assembly line workers as the noise exposed group and 582 males not exposed to noise as the general population group. Data were collected from five years of consecutive annual audiometric tests performed from 2008 to 2012. Results: In the general population and noise exposed groups, there was a reverse phenomenon that hearing threshold level for 2009 was lower than that of 2008, which seemed to be due to the learning effect, but from 2010 hearing threshold level increased. In the noise exposed group, the mean hearing threshold level in the left ear was significantly higher than that for right ear. In the general population group, the older was the age, the higher was the hearing threshold level, especially at 4000 Hz. In the general population and noise exposed groups, frequency, age group and noise exposure independently affected hearing threshold level, and there was no relationship between age and noise exposure. Over all frequencies, the change of hearing threshold level was larger in the noise exposed group than in the general population group. In the noise exposed group below thirty years old, the change at 4000 Hz was remarkable. Conclusions: Age and noise exposure seem to affect hearing threshold level independently and contribute to an additive effect on hearing threshold level.

• 한국산업보건학회지
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• 제5권2호
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• pp.193-199
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• 1995

This study was designed to investigate the difference of time weighted average(TWA) of noise levels and noise doses by the different operating parameter settings such as exchange rate, threshold level and criterion level for noise dosimeter in the field measurements of noise at industrial working environments. The time weighted averages of noise level and noise doses for noise working environments were determined by noise dosimeter on 80 workers employed at 20 industrial establishments of 8 industries. The results obtained were as follows: 1. The mean time weighted average(TWA) of the noise working environments by the operating parameter settings showed 93.4 dB(A) in 3 dB of exchange rate, 80 dB of threshold level and 90dB of criterion level 92.0 dB(A) in 3 dB-exchange rate, 90 dB-threshold level and 90 dB-criterion level, in 90.8 dB(A) in 5 dB of exchange rate, 80 dB of threshold level and 90 dB of criterion level, and 86.7 dB(A) in 5 dB of exchange rate, 90 dB of threshold level and 90dB of criterion level. 2. ln group of noise level less than 90 dB(A), mean TWAs of 80 dB of threshold level were significantly higher than that of 90 dB of threshold level in 3 dB and 5 dB of exchange rate. 3. The case exceeded threshold limit value of noise was 49(61.3 %) in 3dB, 80dB and 90 dB setting, 44(55.0 %) in 3 dB, 90 dB, 90 dB setting, 33(41.3 %) in 5 dB, 80dB, 90 dB setting and 26(32.5%) in 5 dB, 90 dB, 90 dB setting. Above considerations in mind, it is suggested that exchange rate and threshold level be specified in related laws and regulations in the evaluation of working environments noise.

• 한국도로학회논문집
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• 제17권1호
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• pp.129-142
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• 2015

PURPOSES : The purpose of this study is to suggest a basis for setting appropriate safety goals specifically related to the threshold zone luminance in a vehicular traffic tunnel. METHODS : In the test, drivers were divided into two groups. One group consisted of all drivers (average drivers) group with an age ratio of drivers holding domestic driver's license and driver group by age to produce threshold zone luminance in the tunnel. The threshold zone luminance produced as a result was used to analyze how it affects the safety level of each driver group and provide a basis for setting an appropriate safety criterion that can be used to determine threshold zone luminance. We used test equipment, test conditions, and ananalysis of threshold zone luminance identical to that reported by ChoandJung(2014) but the values of adaptation luminance in our analys is were expanded to range from100 to $10,000cd/m^2$. RESULTS : Adaptation luminance and threshold zone luminance are found to be related by a quadratic function. The threshold zone luminance needed by older drivers to ensure a certain safety level is significantly higher than that for drivers of other age brackets when adaptation luminance increases. 56% of older drivers are at an increased risk of an accident at the same luminance for which the safety level of average drivers is 75%. The safety level that can be achieved for older drivers increases to above 60% when threshold zone luminance level is set with the goal of attaining a safety level of more than 85% for average drivers. The safety level that can be attained for average drivers is above 90% when the threshold zone luminance is high enough to ensure over 75% in the safety level of older drivers. Results of this study are applicable to highways and others whose designed speed is 100 km/h. CONCLUSIONS : Threshold zone luminance determined on the basis of drivers having average visual ability is of limited value as a performance standard for ensuring the safety of older drivers. Hence, safety level for older drivers should be considered separately from safety levels for drivers with an average ability to avoid risk. Upward adjustment of older drivers' safety level in the process of determining appropriate threshold zone luminance in a vehicular traffic tunnel may bring both tangible and intangible benefit as a result of reducing accidents. However, there is an associated dollar cost arising from installing and operating lights. As a result, the economic impact of these trade-offs should also be considered.

• 한국보건간호학회지
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• 제26권1호
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• pp.126-136
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• 2012

Purpose: The purpose of this study was to investigate the relationship among use of earphones, stress level, and hearing threshold in university students. Methods: Study subjects included 210 university students (76 men, 134 women). Data were collected by questionnaire and audiometer from December 17 to 20, 2011. The SPSS win 19.0 program was used for data analysis by descriptive statistics, t-test, one-way ANOVA, and Pearson's correlation coefficient. Results: 1) 4KHz, 6KHz hearing threshold of subjects who used earphones was higher than average hearing threshold of same age group. 2) Not significant differences in hearing threshold were observed according to frequency of use, and stress level. 3) Significant differences in 4KHz hearing threshold were observed according to earphone volume. 4) A significant positive correlation was observed between frequency of use and stress level (r=0.15, p<.05), earphone volume, and 4KHz hearing threshold (left) (r=0.15, p<.05); however, a negative correlation was observed between stress level and 4KHz hearing threshold (right) (r=-0.14, p<.05). Conclusion: A significant positive correlation was observed between frequency of use and stress level and earphone volume and 4KHz hearing threshold (left). Development of a program for hearing conservation is needed.

• 한국정보전자통신기술학회논문지
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• 제8권2호
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• pp.140-146
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• 2015

본 논문에서는 레이더 시스템에서 원하는 목표물 추정을 위한 효율적인 임계치 방법을 연구였다. 관심있는 목표물 탐지 검출 방법은 오 경보 확률을 변화 시켜 가면서 원하는 목표물을 추정한다. 이때 오 경보의 확률은 임계치와 밀접한 관계가 있다. 임계치를 낮게 하면 원하는 목표물의 정확도를 향상시킬 수 있지만 잡음 까지 추정하여 효율적인 신호처리 방법이 되지 못한다. 효율 적인 임계치 방법을 제안하여 원하는 목표물을 추정하는 연구 방법을 제안하다. 모의실험을 통해서 기존의 방법과 본 연구에서 제안한 방법을 비교 분석하였다.

• 한국수자원학회논문집
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• 제47권5호
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• pp.491-500
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• 2014

하천수 가뭄을 평가하기 위하여 임계수준 방법을 이용한 하천수 가뭄지수 (streamflow drought index)를 소개하고 섬진강댐의 유입량을 대상으로 적용하였다. 사용한 임계수준은 고정, 월별 및 일별로써 연도별 가뭄의 1~3순위 분석결과, 1984년, 1988년과 1995년이 수문학적 가뭄의 크기도 컸고 오랫동안 지속되었다. 총 물 부족량과 지속기간의 극한값을 연도별로 비교해 본 바, 1984년, 1988년, 1995년과 2001년에 발생하였던 사상이 심각한 수준이었다. 또한 고정 임계수준은 계절 변동성을 반영하지못하는 단점이 있어서 최소한계절 이하의 임계수준 사용이 요구되었지만 월별과 일별로 정해진 임계수준은 적정한 것으로 판단되었다. 본 연구에서 제안한 방법론은 갈수예보 및 저수지 용량결정에 활용될 수 있겠다.

• 한국도로학회논문집
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• 제16권3호
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• pp.85-99
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• 2014

PURPOSES : This study has been performed with the objective to determine threshold zone luminance of adaptation luminance by target safety level in a vehicular traffic tunnel with design speed set at 100km/h. METHODS : The study made a miniature capable of portraying changes in luminance distribution within $2{\times}10^{\circ}$ conical field of view of the driver approaching to the tunnel for the test. Test conditions were set based on justifications for CIE 88-1990's threshold zone luminance used as a reference by domestic tunnel light standards (KS C 3703 : 2010). Luminance contrast of object background and object is 23%, object presentation duration is 0.5 seconds, and size of the object background is $7.3{\times}11.5m^2$ RESULTS : Threshold zone luminance was set within adaptation luminance of $100{\sim}3,000cd/m^2$. Adaptation luminance and threshold zone luminance based on 50%, 75% and 90% target safety level all showed a relatively high linear relationship. According to findings in the study, it is not appropriate to specify the relationship between adaptation luminance and threshold zone luminance as luminance ratio. Rather, direct utilization of the linear relationship gained from the study findings appears to be the better solution. CONCLUSIONS : Findings of this study may be used to determine operation of threshold zone luminance based on target safety level. However, a proper verification and validity of test results are required. Furthermore, a study to determine proper threshold zone luminance level considering target safety level reviewed in this study and various decision-making factors such as economic conditions in Korea and energy-related policies should be carried out in addition. Additional tests on adaptation luminance greater than $3,000cd/m^2$ will be performed, through which application scope of the test findings will be broadened.

• 한국농공학회논문집
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• 제61권1호
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• pp.107-120
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• 2019

Reservoir water level data identify the current water storage of the reservoir, and they are utilized as primary data for management and research of agricultural water. For the reservoir storage management, Korea Rural Community Corporation (KRC) installed water level stations at around 1,600 agricultural reservoirs and has been collecting the water level data every 10 minutes. However, various kinds of outliers due to noise and erroneous problems are frequently appearing because of environmental and physical causes. Therefore, it is necessary to detect outlier and improve the quality of reservoir water level data to utilize the water level data in purpose. This study was conducted to detect and classify outlier and normal data using two different models including the threshold model and the artificial neural network (ANN) model. The results were compared to evaluate the performance of the models. The threshold model identifies the outlier by setting the upper/lower bound of water level data and variation data and by setting bandwidth of water level data as a threshold of regarding erroneous water level. The ANN model was trained with prepared training dataset as normal data (T) and outlier (F), and the ANN model operated for identifying the outlier. The models are evaluated with reference data which were collected reservoir water level data in daily by KRC. The outlier detection performance of the threshold model was better than the ANN model, but ANN model showed better detection performance for not classifying normal data as outlier.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권6호
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• pp.1-7
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• 2015

The most critical health effect of lead exposure is the neurodevelopmental effect to children caused by the increased blood lead level. Therefore, the endpoint of the risk assessment for lead-contaminated sites should be set at the blood lead level of children. In foreign countries, the risk assessment for lead-contaminated sites is conducted by estimating the increased blood lead level of children via oral intake and/or inhalation (United States Environmental Protection Agency, USEPA), or by comparing the estimated oral dose to the threshold oral dose of lead, which is derived from the permissible blood lead level of children (Dutch National Institute for Public Health and the Environment, RIVM). For the risk assessment, USEPA employs Integrated-Exposure-Uptake-Biokinetic (IEUBK) Model to check whether the estimated portion of children whose blood lead level exceeds 10 µg/dL, threshold blood lead level determined by USEPA, is higher than 5%, while Dutch RIVM compares the estimated oral dose of lead to the threshold oral dose (2.8 µg/kg-day), which is derived from the permissible blood lead level of children. In Korea, like The Netherlands, risk assessment for lead-contaminated sites is conducted by comparing the estimated oral dose to the threshold oral dose; however, because the threshold oral dose listed in Korean risk assessment guidance is an unidentified value, it is recommended to revise the existing threshold oral dose described in Korean risk assessment guidance. And, if significant lead exposure via inhalation is suspected, it is useful to employ IEUBK Model to derive the risk posed via multimedia exposure (i.e., both oral ingestion and inhalation).

• 한국산학기술학회논문지
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• 제13권5호
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• pp.2291-2297
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• 2012

X-선 스펙트럼 데이터는 물질의 성분과 관련이 없는 신호(백그라운드, 노이즈)들을 포함 하고 있다. XRF는 스펙트럼에서 가우시안 형태의 피크 위치와 크기를 이용하여 시료의 성분을 분석하며, 시료의 성분을 정확히 분석하기 위해서는 노이즈와 백그라운드를 제거 하여야 한다. 백그라운드를 제거하기 위한 방법으로는 SNIP, Threshold, Morphology 방법 등을 적용하고 있으며, Threshold 기법을 중에서 블록별로 각기 다른 임계값을 적용하는 Interval Threshold기법이 하나의 임계값을 적용하는 Level Threshold 방법보다 더 좋은 성능을 발휘한다. 본 논문에서는 Interval Threshold를 적용하기 위하여 웨이블릿을 이용하여 블록을 분리하는 알고리즘을 제안하였다.