• 대한방사선기술학회지:방사선기술과학
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• 제18권1호
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• pp.55-62
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• 1995

This study was performed to find out dose distribution, pdd, surface dose and off center ratio. A few articles is analysis of dose data in radiotherapy field, there is no standardized measure of an assessment of exposure dose at diagnostic radiology, yet. And authors demonstrated a new assessment measure by ion chamber, TLD and film dosimetry system. We assurance that our data is useful to quantiative analysis of exposure dose and clinical fields for reduction of radiation dose.

• 한국멀티미디어학회논문지
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• 제19권8호
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• pp.1386-1394
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• 2016

Pyramid fusion usually adjusts the Laplacian weights of pixels of the input images by evaluating predefined criteria. This has advantages that it can selectively express intense color and enhance the contrast when applied to HDR exposure fusion. But it may cause noise because the weights are determined by pixel importance without considering the interdependent pixel relationship that constitutes a scene. This paper proposes a fusion method using simple weight criteria generated from the gray pixel values, which is expected to preserve the interdependent relationship and improve execution speed. In order to evaluate the performance of the proposed method we examine a homogeneity measure, H and compare the execution time for both methods. The proposed method is found to be more advantageous with respect to homogeneity and execution speed.

• Toxicological Research
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• 제6권1호
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• pp.63-73
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• 1990

Human exposure to environmental carcinogens can be detected by a number of methods including immunoassay, $^{32}P-postlabeling$ assay, and fluorescence technique. These assays have been applied to measure biological markers of carcinogen-adducts formed with macromolecules such as DNA, RNA and protein. In an attempt to investigate causal relationships between carcinogen exposure and tumor formation, specific carcinogen-adducts have been quantitated from human tissues and body fluids of cancer patients, occupational workers heavily exposed to certain carcinogens, smokers and controls. Carcinogens studied for biological human monitoring include benzo(a)pyrene, aflatoxin B1, UV light, ethylene oxide, 8-methoxypsoralen, 4-aminobiphenyl, vinyl choride, N-nitrosamine, cisplatin and other chemotherapeutic agents. Relevance of human monitoring for cancer research, progress in this field, methods to detect carcinogen-adducts are reviewed here. It is hoped that these approaches will be used for the risk assessment of carcinogen exposure, cancer etiology study and cancer prevention in humans.

• Toxicological Research
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• 제6권1호
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• pp.61-61
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• 1990

Human exposure to environmental carcinogens can be detected by a number of methods including immunoassay, $^{32}P$-postlabeling assay, and fluorescence technique. These assays have been applied to measure biological markers of carcinogen-adducts formed with macromolecules such as DNA, RNA and protein. In an attempt to investigate causal relation ships between carcinogen exposure and tumor formation, specific carcinogen-adducts have been quantitated from human tissues and body fluids of cancer patients, occupational workers heavily exposed to certain carcinogens, smokers and controls. Carcinogens studied for biological human monitoring include benzo(a)pyrene, aflatoxin B1, UV light, ethylene oxide, 8-methoxypsoralen, 4-aminobiphenyl, vinyl chloride, N-nitrosamine, cisplatin and other chemotherapeutic agents. Relevance of human monitoring for cancer research, progress in this field, methods to detect carcinogen-adducts are reviewed here. It is hoped that these approaches will be used for the risk assessment of carcinogen exposure, cancer etiology study and cancer prevention in humans.

• 한국환경보건학회지
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• 제40권1호
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• pp.17-26
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• 2014

Background: Despite children's unique characteristics that distinguish them from adults, relatively few attempts have been made to measure exposure factors for characterization of children's exposure to hazardous chemicals in child-specific products (CSP). This study was conducted to establish the child-specific exposure factors for exposure and risk assessment of hazardous substances in CSP. Methods: We investigated the exposure factors (e.g., time use of child-products, time and frequency of object-to-body contact, time and frequency of object-to-mouth contact) influencing children's exposure to CSP (e.g., toys, playmats, oil pastels, etc.) in 650 children through a parent-completed questionnaire using a web-based survey. Participants were recruited in five age groups, <1, 1-2, 2-3, 3-6, and 6-12 years of age. Results: The child-specific exposure factors were presented as the mean, median, $95^{th}$ percentile, minimum, and maximum values. Time activity for play mats was the longest among CSP and infants spent more time on them than did elder age groups (189.3-224.7 min/day for <1-2 years vs. 91.2 min/day for 6-12 years). It is apparent that time and frequency of toy block- and plastic toy-to-mouth contact significantly decreased as a function of age. When the variation of CSP use patterns was compared by gender, the only variable that was statistically different between genders was time activity in child-products exposure space. Conclusion: We believe the five child-specific exposure factors suggested in the present study will be valuable for reducing uncertainty in the estimation of chemical exposure during risk assessment of CSP and furthermore, in the appropriate regulations to protect children's health.

• 대한방사선기술학회지:방사선기술과학
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• 제41권2호
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• pp.115-122
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• 2018

We aims to perform comparative analysis on the dose area and image qualities varying on the slice thickness when using Automatic Exposure Controller (AEC) and manual exposure; thus, it wants to suggest a measure to reduce exposure dose by setting the optimal examination condition for each slice thickness. The method was to set the thickness as Thin, Normal, and Heavy adult and evaluate the dose area, spatial resolution, low contrast resolution, Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) according to each slice thickness by using the AEC and the manual exposure controller. The dose area according to each slice thickness all increased both when using the AEC and the manual exposure. However, the manual exposure showed lower dose area product than the AEC. Spatial resolutions and low contrast resolutions were all observed to be higher than the evaluation standard. Also, the SNR and CNR of each thickness all increased when using the AEC. When using the manual exposure, SNR and CNR increased in all cases other than the Heavy Adult. Consequently, the Thin and Normal Adult showed dose reduction about 2 times when using the manual exposure controller, while ensuring the image quality. Heavy adult was able to maintain good image quality by using AEC.

• Clinical and Experimental Pediatrics
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• 제55권2호
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• pp.35-41
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• 2012

Passive exposure to tobacco smoke significantly contributes to morbidity and mortality in children. Children, in particular, seem to be the most susceptible population to the harmful effects of environmental tobacco smoke (ETS). Paternal smoking inside the home leads to significant maternal and fetal exposure to ETS and may subsequently affect fetal health. ETS has been associated with adverse effects on pediatric health, including preterm birth, intrauterine growth retardation, perinatal mortality, respiratory illness, neurobehavioral problems, and decreased performance in school. A valid estimation of the risks associated with tobacco exposure depends on accurate measurement. Nicotine and its major metabolite, cotinine, are commonly used as smoking biomarkers, and their levels can be determined in various biological specimens such as blood, saliva, and urine. Recently, hair analysis was found to be a convenient, noninvasive technique for detecting the presence of nicotine exposure. Because nicotine/cotinine accumulates in hair during hair growth, it is a unique measure of longterm, cumulative exposure to tobacco smoke. Although smoking ban policies result in considerable reductions in ETS exposure, children are still exposed significantly to tobacco smoke not only in their homes but also in schools, restaurants, child-care settings, cars, buses, and other public places. Therefore, more effective strategies and public policies to protect preschool children from ETS should be consolidated.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.139-144
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• 2005

Because of the photorefractive recording dynamics, each newly recorded hologram partially erases all previously stored image. Thus achieving the desired diffraction efficiency profile for the entire sequence after all images have been recorded requires exposure time schedule. The often cited classical exposure-schedule model predicts a rising-exponential build-up and an exponential decay in An with an exposure time. However because we cannot directly measure the An, it's difficult to establish the relation of both. In this paper, we deduce the relation of diffraction efficiency and exposure time from experiment data and suggest an algorithm to make time schedule profile in angle/fractal multiplexing of holographic data storage. After that, we present simulated result with equal hologram diffraction efficiency for a sequence of 250 holograms recorded by angle/fractal multiplexing.

• 한국콘텐츠학회논문지
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• 제19권8호
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• pp.276-283
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• 2019

본 연구는 자동노출제어장치(Automatic Exposure Control, AEC)와 수동노출 이용 시 입사표면선량(Entrance Surface Dose, ESD)과 Entropy를 분석하여 자동노출제어장치의 유용성에 대해 알아보고자 하였다. 실험방법은 Skull, Chest, Abdomen, Pelvis 부위에 대하여 란도팬텀(Rando Phantom)에 반도체 선량계를 위치시켜 선량을 측정하였고, 동시에 획득한 DICOM(Digital Imaging and Communications in Medicine) 파일을 Matlab으로 Entropy 분석을 하였다. 그 결과 자동노출제어장치 이용 시 모든 부위의 입사표면선량이 수동노출보다 낮았고 Entropy 수치는 높았으며, paired t-test는 p<0.05로 유의한 차이가 있음을 알 수 있었다. 결론적으로 자동노출제어장치의 사용은 X선 검사 시 발생할 수 있는 불필요한 방사선량과 정보의 손실량을 줄여서 피폭선량과 영상 화질의 최적화에 기여할 수 있는 유용한 방법이 될 수 있다.

• Journal of Korea Trade
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• 제26권3호
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• pp.45-62
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• 2022

Purpose - Using unexpected changes in geopolitical tensions on the Korean peninsula as a quasi-natural experimental setting, we examine whether and how geopolitical risks travel across borders through firm-level imports and exports linkages. We also test whether the effects are driven by either imports or exports and assess whether firms can effectively hedge themselves against geopolitical risks. Design/methodology - We focus on a series of unanticipated geopolitical events taken place in Korea in 2018. Making use of the shocks to geopolitical climate, we identify five milestone events toward peace talks. We employ the event studies methodology. We examine heterogenous firm-level stock price reactions around key event dates depending on firms' exposure to geopolitical risks. As a measure of firms' exposure to geopolitical risks in Korea, we utilize a text-based measure of firm-level trade links. When a firm announces and discusses its purchase of inputs from Korea or sales of outputs to Korea in their annual disclosure filings, we define a firm to have a trade relationship with Korea and have exposure to Korean geopolitical risks. Similarly, we use a measure of a firm's hedging policies based on a firm's textual mention of the use of foreign exchange derivatives in their annual disclosure. Findings - We find that U.S. firms that have direct trade links to Korea gained significantly more value when the intensity of geopolitical risks drops compared to firms without such trade links to Korea. The effects are pronounced for firms purchasing inputs from or selling outputs to Korea. We find that the effectiveness of foreign exchange hedging against geopolitical risks is limited. Originality/value - We document the international transmission of geopolitical uncertainty through trade linkages. Export links as well as import links serve as important nexus of transmission of geopolitical risks across borders. Hedging strategies involving foreign-exchanges derivatives do not seem to insulate firms again geopolitical risks. With the recent movements of localization and reshuffling of the global value chain, our results suggest a significant impact of geopolitical risks in Korea on the construction of the global value chain.