• 한국산업보건학회지
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• 제4권1호
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• pp.81-95
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• 1994

This study was performed in a diatomite factory where silicosis had been found at October, 1993. The major objectives were to evaluate worker exposure to diatomaceous earth and to present engineering control methods for workplace management. Total and respirable dust of diatomaceous earth were measured. Size distribution of dust was analyzed by applying the multiple diffraction method. Also crystalline silica in respirable dust samples was analyzed qualitatively by X-ray diffraction. The suitable Local Exhaust Ventilation systems for that factory were recommended. The results were as follows. The airborne total and respirable dust concentrations by exposure groups showed approximate normal distribution. The means of total dust exposures at flour maufacturing, fire brick grinding and packaging, ceramic raws packaging processes exceeded Korean and ACGIH standards, $10mg/m^3$. The means of total and respirable dust concentrations to high exposure groups were 6.8 and 3.9 times higher than those of low expousre groups, respectively. The size distribution of diatomaceous earth dust was lognormal with a median diameter of $7.07{\mu}m$(range, $0.10-60.0{\mu}m$) and with a geometric standard deviation of 1.43. The crystalline silica in respirable dust samples was identified to quartz and cristobalite and/or tridymite. Above results suggest that engineering controls and periodic environmental and medical surveillances will be important for preventing silicosis in the diatomite factory.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.540-543
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• 2007

The modulation transfer function (MTF) in a camera system is a measurement of how well the system will faithfully reproduce the original scene. The electro-optical camera system consists of optics, an array of pixels, and an electronics which is related to the image signal chain. The system MTF can be cascaded with each element's MTF in the frequency domain. That is to say, the electronics MTF including the detector MTF can be recalculated easily by the acquired system MTF if the well-known test optics is used in the measuring process. A Time-Delay and Integration (TDI) detector can make a signal increase by taking multiple exposures of the same object and adding them. It can be considered the various methods to measure the MTF of the TDI camera system. This paper shows the actual and practical MTF measuring methods for the detector and electronics in the TDI camera. The several methods are described according to the scan direction as well as the TDI stages such as the single line mode and the multiple-lines mode. The measuring is performed in the in the static condition or dynamic condition to get the point spread function (PSF) or the line spread function (LSF). Especially, the dynamic test bench is used to simulate on track velocity to synchronize with TDI read out frequency for the dynamic movement.

• 천문학회보
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• 제36권2호
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• pp.129.1-129.1
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• 2011

We have applied an advanced multi-aperture indexing photometry and sophisticated de-trending method to existing Taiwanese-American Occultation Survey (TAOS) data sets. TAOS, a wide-field ($3^{\circ}{\times}3^{\circ}$) and rapid photometry (5Hz) survey, is designed to detect small objects in the Kuiper Belt. Since TAOS has fast and multiple exposures per zipper mode image, point spread function (PSF) varies in a given image. Selecting appropriate aperture among various size apertures allows us to reflect these variations in each light curve. The survey data turned out to contain various trends such as telescope vibration, CCD noise, and unstable local weather. We select multiple sets of stars using a hierarchical clustering algorithm in such a way that the light curves in each cluster show strong correlations between them. We then determine a primary trend (PT) per cluster using a weighted sum of the normalized light curves, and we use the constructed PTs to remove trends in individual light curves. After removing the trend, we can get each synthetic light curve of star that has much higher signal-to-noise ratio. We compare the efficiency of the synthetic light curves with the efficiency of light curves made by previous existing photometry pipelines. Our photometric method is able to restore subtle brightness variation that tends to be missed in conventional aperture photometric methods, and can be applied to other wide-field surveys suffering from PSF variations and trends. We are developing an analysis package for the next generation TAOS survey (TAOS II) based on the current experiments.

• 한국환경보건학회지
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• 제48권4호
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• pp.236-243
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• 2022

Background: In the case of multiple exposures to different types of heavy metals, such as the conditions faced by residents living near a smelter, it would be preferable to group hazardous substances with similar characteristics rather than individually related substances and evaluate the effects of each group on the human body. Objectives: The purpose of this study is to evaluate the utility of factor analysis in the assessment of health effects caused by exposure to two or more hazardous substances with similar characteristics, such as in the case of residents living near a smelter. Methods: Heavy metal concentration data for 572 people living in the vicinity of the Janghang smelter area were grouped based on several subfactors according to their characteristics using factor analysis. Using these factor scores as an independent variable, multiple regression analysis was performed on health effect markers. Results: Through factor analysis, three subfactors were extracted. Factor 1 contained copper and zinc in serum and revealed a common characteristic of the enzyme co-factor in the human body. Factor 2 involved urinary cadmium and arsenic, which are harmful metals related to kidney damage. Factor 3 encompassed blood mercury and lead, which are classified as related to cardiovascular disease. As a result of multiple linear regression analysis, it was found that using the factor index derived through factor analysis as an independent variable is more advantageous in assessing the relevance to health effects than when analyzing the two heavy metals by including them in a single regression model. Conclusions: The results of this study suggest that regression analysis linked with factor analysis is a good alternative in that it can simultaneously identify the effects of heavy metals with similar properties while overcoming multicollinearity that may occur in environmental epidemiologic studies on exposure to various types of heavy metals.

• 대한전자공학회논문지SP
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• 제49권4호
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• pp.49-57
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• 2012

본 논문은 디블러링(Deblurring) 계산 시간을 단축하면서 복원된 영상의 텍스처 및 에지의 선명도를 동시에 강화할 수 있는 다중 영상 기반의 고속 처리용 디블러링 기법을 제안하고자 한다. 먼저 상대적으로 긴 노출 시간에서 촬영된 번짐(Blurring) 결함이 발생한 두 장의 번짐 영상과 짧은 노출에서 촬영된 번짐이 없지만 잡음 성분이 많은 한 장의 잡음 영상을 취득한다. 그리고 처리 속도 개선을 위해 촬영된 다중 입력 영상을 두 배로 다운 샘플링 한 후, 전체 영상에서 추출된 영상 패치 또는 에지 패치에 기반한 점 확산 함수(PSF: Point Spread Function) 추정 기법을 도입해서 점 확산 함수 추정에 소요되는 계산 시간을 효과적으로 단축할 것이다. 입력 영상의 다운 샘플링으로 인해 열하된 미세한 텍스처 성분의 표현 능력을 보완하고 번짐현상이 제거된 복원 영상을 재현하기 위해 텍스처 향상을 위한 디블러링 기법을 개발 및 적용할 것이다. 마지막으로 입력 영상과 동일한 영상 크기로 복구하기 위해 잡음 영상의 선명한 에지 성분을 활용한 업 샘플링 기법을 적용할 것이다. 제안된 방법을 통해 기존의 디지털 카메라 적용에 걸림돌이 되었던 디블러링 처리 속도 시간을 단축할 수 있었고 동시에 텍스처 및 에지의 미세한 성분도 복원할 수 있었다.

• 대한의용생체공학회:의공학회지
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• 제33권2호
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• pp.59-64
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• 2012

With rapid increasing usage of smart phones, social concerns have arisen about the possible effects of electromagnetic fields emitted from wideband code division multiple access(WCDMA) mobile phones on human health. The number of people with self-reported electromagnetic hypersensitivity(EHS) who complain of various subjective symptoms such as headache, insomnia etc. has also recently increased. However, it is unclear whether EHS results from physiological or other origins. In this double-blinded study, we investigated physiological changes such as heart rate, respiration rate, and heart rate variability with real and sham exposures for 15 EHS and 17 non-EHS persons using a module inside a dummy phone. Experiment was conducted using a WCDMA module with average power of 24 dBm at 1950 MHz with the specific absorption rate of 1.57 W/kg using a headphone for 32 min. As a conclusion, WCDMA RF exposure did not have any effects on the physiological variables in either group.

• 한국산업보건학회지
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• 제23권3호
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• pp.229-242
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• 2013

Objectives: This study was designed to investigate the current status of the association of job-related information such as employment status, workplace environment, and hazard material exposures with health examination outcomes. Methods: The study used data from KNHANES 2007-2009 representing the three years of 2007-2009, which was conducted annually using a rolling sampling design that involved a complex, stratified, multistage, probability-cluster survey of a representative sample of the non-institutionalized civilian population in Korea. The final analytical sample consisted of 17,240 participants. Information on age, education, smoking history and alcohol intake was collected during the health interview. Job related information consisted of employment status, workplace environment, and hazardous material exposure. The selected indices of health examination were blood pressure, fasting glucose, blood cholesterol, HDL, SGOT, SGPT, and BUN. Results: In multiple logistic regression analysis using hypertension and pre-hypertension as dependent variables and job related categories as independent variables after covariate adjustments, the odds of hypertension and pre-hypertension were significantly lower in those with responsibility and power in their job activities. Interestingly, low odds for hypertension were observed among those who reported that their jobs were fast-paced. Conclusions: This study confirmed that some job-related categories in employment status, workplace environment, and hazardous material exposure had an association with health outcome status. It is worthwhile to comment that high responsibility and power in job activities were revealed as one of the important favorable factors to improve health condition of workers.

• Toxicological Research
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• 제34권4호
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• pp.281-290
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• 2018

Exposure to chemical agents is an inevitable consequence of modern society; some of these agents are hazardous to human health. The effects of chemical carcinogens are of great concern in many countries, and international organizations, such as the World Health Organization, have established guidelines for the regulation of these chemicals. Carcinogens are currently categorized into two classes, genotoxic and non-genotoxic carcinogens, which are subject to different regulatory policies. Genotoxic carcinogens are chemicals that exert carcinogenicity via the induction of mutations. Owing to their DNA interaction properties, there is thought to be no safe exposure threshold or dose. Genotoxic carcinogens are regulated under the assumption that they pose a cancer risk for humans, even at very low doses. In contrast, non-genotoxic carcinogens, which induce cancer through mechanisms other than mutations, such as hormonal effects, cytotoxicity, cell proliferation, or epigenetic changes, are thought to have a safe exposure threshold or dose; thus, their use in society is permitted unless the exposure or intake level would exceed the threshold. Genotoxicity assays are an important method to distinguish the two classes of carcinogens. However, some carcinogens have negative results in in vitro bacterial mutation assays, but yield positive results in the in vivo transgenic rodent gene mutation assay. Non-DNA damage, such as spindle poison or topoisomerase inhibition, often leads to positive results in cytogenetic genotoxicity assays such as the chromosome aberration assay or the micronucleus assay. Therefore, mechanistic considerations of tumor induction, based on the results of the genotoxicity assays, are necessary to distinguish genotoxic and non-genotoxic carcinogens. In this review, the concept of threshold of toxicological concern is introduced and the potential risk from multiple exposures to low doses of genotoxic carcinogens is also discussed.

• 응용통계연구
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• 제21권1호
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• pp.53-63
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• 2008

일반적으로 인간의 질병과 가축의 경제적인 특성은 하나의 유전자가 아닌 여러 유전자의 상호작용으로 일어난다고 믿고 있다. 따라서 본 연구에서는 세대를 거듭할수록 대립유전자의 유전이 안정적으로 발생되어지고 개체의 기능적인 유전적 가치를 직접적으로 추정할 수 있는 single nucleotide polymorphism(SNP)을 한우의 경제적 특성인도체중(carcass cold weight)에 대하여 모수적인 방법인 ANOVA와 비모수적인 방법인 multifactor dimensionality reduction(MDR)을 이용하여 하나의 유전자의 효과와 두 개의 유전자의 상호작용 효과를 비교하였다. ANOVA에서는 하나의 유전자 SNP1이 도체중에 유의한 효과가 있었고 상호작용 효과에서는 도체중에 유의한 효과는 없었다. MDR에서는 하나의 유전자의 효과인 SNP1과 두 개의 유전자의 상호작용인 SNP1*SNP2의 효과가 컸으며 SNP1과 SNP1*SNP2를 비교했을 시에는 SNP1*SNP2의 효과가 더 크게 나타났다. 이는 개별 SNP유전자 보다 복합 SNP유전자의 상호작용이 경제적인 특성인 도체증에 더 영향을 준다는 것을 알 수 있었다.

• 한국환경보건학회지
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• 제38권1호
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• pp.31-41
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• 2012

Objectives: Biomonitoring is used to assess human environmental exposures. Urinary biomonitoring data are typically adjusted to a constant creatinine concentration to correct for variable dilutions among spot samples. Our objective was to investigate urinary creatinine concentrations by region, gender, age and lifestyle. Methods: We studied urinary creatinine concentrations in 6,286 Koreans aged 20 years old and older who participated the fourth Korea National Health and Nutrition Survey (KNHANES IV) in 2009. Urinary creatinine concentration analysis used the Jaffe method. Results: The average urinary creatinine concentration of 6,286 Koreans was 158.99 mg/dl. The urinary creatinine concentration was significantly higher among men (184.97 mg/dl) than women (130.02 mg/dl). In both men and women, urinary creatinine concentrations were significantly different according to age group (p < 0.01). Whereas the urinary creatinine concentration of men significantly differed with smoking in adjusted comparison analysis, that of women significantly differed by education level. Ninety-two percent of urinary creatinine concentration was included within WHO guidelines effective range(30 mg/dl ${\leq}$ urinary creatinine concentration ${\leq}$ 300 mg/dl). In multiple regression analysis, creatinine was influenced by gender, age and body mass index (BMI). Conclusions: The urinary creatinine value obtained from representative samples of adult Koreans aged 20 year and older in KNHANES IV 2009 could be used as a reference value for other nationally studied surveys, such as abandoned metal mine surveys and surveys for industrial complexes.