• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.1
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• pp.51-60
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• 2018

Objectives: Currently, there is only limited knowledge regarding the hazard of low-level exposure to CMR materials in workplaces. To overcome this limitation, a reference concentration for workers($RfC_w$) from among the risk assessment tools proposed by the US EPA is widely used to set a provisional workplace exposure level(PWEL) for CMR materials for which there are no established Korea Occupational Exposure Limits(KOELs) or subjective chemicals for work environment measurements as regulated by Korea Ministry of Employment and Labor(KMOEL). A simple European calculator of derived no effect level(SECO-DNEL) as proposed by REACH can also be used in place of $RfC_w$ to set the PWEL for chemicals. This study was performed to test the acceptability of using SECO-DNEL as an alternative to $RfC_w$ when setting a PWEL for low-level exposures. Methods: The $RfC_w$ and DNEL for the five CMR materials of dinitrogen oxide, catechol, 2-phenoxy ethanol, carbitol, and carbon black were calculated using the dose-response assessments of the US EPA for $RfC_w$ and REACH guidance for SECO-DNEL, respectively. They were compared using paired t-tests to determine the statistical differences between them. Results: For the five chemicals, the $RfC_w$ were 2.53 ppm, 0.10 ppm, 1.73 ppm, 1.66 ppm, and $0.05mg/m^3$, respectively, while the SECO-DNEL were 2.01 ppm, 0.11 ppm, 1.83 ppm, 1.77 ppm, $0.14mg/m^3$, respectively. There was no statistically significant difference between $RfC_w$ and SECO-DNEL. Conclusions: This study suggests that the SECO-DNEL could be applied in place of $RfC_w$ to set a PWEL for low-level exposure to chemicals, especially CMR materials. To further ensure the reliability of SECO-DNEL as an alternative tool, more chemicals should be applied for calculation and comparison with $RfC_w$.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.1
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• pp.80-90
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• 2018

Objectives: This study was performed to propose a domestic occupational exposure limit(OEL) following a health hazard assessment, calculation of a non-carcinogenicity reference concentration worker($RfC_{worker}$) value, and examination of international agencies' exposure limits. It also recommends legal management within the Occupational Safety and Health Act for HCFC-123, which caused an acute hepatotoxicity incident. Methods: An acute hepatotoxicity incident due to the fire extinguishing agent HCFC-123 was investigated. Toxicological hazard and health hazard classifications were examined and a non-carcinogenicity $RfC_{worker}$ value was calculated for HCFC-123. An OEL and the necessity of legal management were recommended as well. Results and Conclusions: An OEL for HCFC-123 of 10 ppm($62.5mg/m^3$), which considered the $RfC_{worker}$ value, 5.56 ppm, produced in dose-response assessment and the exposure level of 19.1-20.9 ppm measured as an eight-hour TWA(time-weighted average) in the incident place, is recommended. HCFC-123 is urged to be included as a chemical requiring legal management in the Occupational Safety and Health Regulations. In addition, it is recommended that a peak exposure of ACGIH be adopted in the Notice of the Ministry of Employment and Labor.

• Journal of Sensor Science and Technology
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• v.3 no.1
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• pp.40-45
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• 1994

$112^{\circ}$ rot. x-cut $LiTaO_{3}$ wafer was used as the substrate of SAW gas sensor. Dual delay line SAW device with IDTs which consist of the reference delay line and the sensing delay line was fabricated using photolithigraphy. Each IDTs had 10 finger pairs and finger spacing is 10 microns. One delay line channel is the reference, while the second is the sensing channel with Pb-phthalocyanine film in the propagation path. Pb-phthalocyanine film which is p-type organic semiconductor was evaporated in $10^{-5}$ torr vacuum using shadow mask selectively. Dual delay line oscillator was constructed by using the rf amplifier and AGC. Frequency of the IDTs had the range of $87{\sim}$89 MHz oscillation frequency. Oscillation frequency shifts were investigated as a function of the temperature and the concentration of $NO_{2}$ gas.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.1
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• pp.13-20
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• 2019

Objective: This study was performed to propose a domestic occupational exposure limit(OEL) following a health hazard assessment, calculation of a non-carcinogenicity reference concentration worker($RfC_{worker}$) value, and examination of international agencies' exposure limits. It also recommends legal management within the Occupational Safety and Health Act for PHMG-Phosphate(CAS No. 89697-78-9), It is a humidifier disinfectant that generated many lung injuries. Methods: We have investigated the recommendation or guidelines of foreign OEL for PHMG-Phosphate and the actual state of legal management in Korea. To examine the procedures and methods for recommendation OEL. Toxicological hazard and health hazard classifications were examined and a non-carcinogenicity $RfC_{worker}$ value was calculated for PHMG-Phosphate. An OEL and the necessity of legal management were recommended as well. Results and Conclusions: The OEL for PHMG-Phosphate is recommended to be $0.01mg/m^3$. The recommended OEL is close to 10 times the RfCworker value of $0.000833mg/m^3$ calculated from the chemical dose-response hazard assessment, which is a 2017 study. The CMIT/MIT(3:1) mixture, which was a social issue as a humidifier disinfectant substance, was also exposed to the same ratio in March 2018, establish the OEL. It is recommended to establish OEL for PHMG-Phosphate to prevent worker health hazards and for chemical safety management.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1559-1563
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• 2011

We fabricated gallium doped ZnO (GZO, 5 wt% Ga) thin films on PES (polyethersulfon) substrate with RF magnetron sputtering and investigated optical and electrical properties for various substrate temperatures ($50{\sim}200^{\circ}C$). All GZO thin film has c-axis preferred orientation without reference to deposition conditions. As a result of AFM analysis, the GZO thin film deposited at $200^{\circ}C$ exhibited the lowest surface roughness of 0.196nm. The transmittance of GZO thin films were above 80% and Burstein-Moss effect was observed. In the analysis of Hall measurement, we confirmed that the GZO thin film deposited at $200^{\circ}C$ showed the lowest resistivity of $6.93{\times}10-4{\Omega}{\cdot}cm$ and the highest carrier concentration of $7.04{\times}1020/cm^3$.

• Journal of Environmental Health Sciences
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• v.46 no.3
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• pp.335-343
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• 2020

Objectives: The Korean Ministry of Environment has identified cases of people suspected of suffering lung disease potentially caused by polyhexamethylene guanidine (PHMG) used in humidifier disinfectants (HDs). Exposure assessment for the HDs was conducted using a questionnaire during face-to-face interview. The main purposes of this study were to develop a methodology to effectively classify levels of exposure to HDs based on a questionnaire. Methods: We first identified the overall participants' exposure characteristics by HD exposure levels; Second, we selected misclassified subjects and investigated characteristics of overestimated and underestimated subjects, focusing on exposure cases to PHMG-containing HDs. An inhalation reference concentration (RfC) for PHMG was produced on the basis of inhalation toxicity values. We made a cross-tabulation of the exposure classes (Exposure classes 1-to-4) by clinical classes based on the RfC. When the value of the exposure class minus the clinical class was 0 or 1, we assumed these were true values. When the value was ≥2 and ≤ -2, we assigned these cases to the overestimation group and underestimation group, respectively. Results: The overestimated group may have already recovered and responded excessively due to psychological anxiety or in order to receive compensation. On the other hand, relatively high mortality rates and surrogate responses for those under 10 years of age may have resulted in inaccurate exposure assessment for underestimated groups. For the characteristics of exposure, it was shown that for the underestimated group, the exposure was relatively weaker than the overestimated group, even though a high overall clinical rating was determined. Conclusions: This study may suggest ways to reduce bias and overcome the limitations of current HD exposure assessment.

• Journal of Environmental Impact Assessment
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• v.19 no.3
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• pp.259-270
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• 2010

We conducted human risk assessment for exposure to inhalation of chemical substances emitted from the storage tanks of petroleum refineries. To assess human risk, this study calculated chemical emissions from the external floating roofs on storage tank at petroleum refineries, as well as concentrations thereof in the ambient air using the K-SCREEN model, and then determined risk in accordance with the Reference Concentration (RfC) values and Inhalation Unit Risk criteria developed by the US Environmental Protection Agency. The results indicated that non-carcinogenic chemicals have a hazard quotient of less than 1, meaning they have an insignificant effect on human health for residential areas near the storage tanks. Among the known carcinogens, the hazard risk for benzene slightly exceeded $10^{-6}$, indicating the need for corrective reduction measures. The methodology for health impact assessment devised herein provides findings useful in decision making for policy makers and the general public with respect to construction of industrial complexes. However, the methodology proposed herein does have limitations, including discrepancy in results induced by use of U.S. data (due to the lack of usable domestic data). More systematic studies from related researchers will be needed to address these issues and produce more reliable outcomes.

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.336-341
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• 2014

In order to determine the residual characteristics of pesticides in fruits and their effects on human health, monitoring of pesticide residues were conducted in apples, peaches, pears, grapes and citrus from the major cultivation areas in 2010. Safeties of the pesticides detected from the fruits were evaluated using the amounts of pesticide residue detected and dietary risk index (DRI). Samples were taken from 4-5 major fruit cultivation areas and then pesticide residues in the test fruits were analyzed with a liquid chromatographymass spectrometry (LC-MS/MS). Mean residue levels of the pesticides in fruits were 0.001-0.144 mg/kg. The DRIs were 0.55 for apple, 0.066 for peach, 0.008 for pear, 0.025 for grape, and 0.37 for citrus, respectively. The results indicated that the amounts of pesticide residues in domestic fruits might be safe, considering the regulatory concerning level 1.0.

• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.404-411
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• 2006

이 연구의 목적은 유치원에서 총 휘발성 유기화합물의 농도를 평가하고, 총 휘발성 유기화합물 농도와 대표적인 8개 방향족 화합물의 상관관계를 조사하는데 있다. 도시에 위치한 11개 유치원의 실내와 실외에서 각각 30개, 11개의 지역시료를, 시골에 위치한 4개 유치원에서는 각각 10개, 4개의 시료를 테낙스 튜브를 이용하여 오전에 1-2시간 채취하였다. 채취한 시료는 열탈착하여 가스크로마토그래피-질량분석기로 분석하였다. 13가지 물질을 각각의 표준물질로 개별 정량하여 이중 빈번히 발견되는 8가지 방향족 유기화합물은 상관관계 평가에 사용하였다. 총 휘발성 유기화합물은 톨루엔을 기준으로 정량하였다. 도시에 위치한 유치원 실내의 총 휘발성 유기화합물 농도가 높았고, 조사 건수의 50%가 환경부 및 교육인적자원부의 가이드라인($400{\mu}g/m^{3}$)을 초과하였다. 도시지역의 유치원 실내 및 실외의 기하평균은 각각 $387.9{\mu}g/m^{3}$과 $134.9{\mu}g/m^{3}$이었고, 시골지역 유치원에서는 각각 $189.6{\mu}g/m^{3},;74.4{\mu}g/m^{3}$이었다. 톨루엔, 크실렌, 에틸벤젠, 정량한 유기 화합물 총합, 총 휘발성 유기화합물은 기하정규분포를 하였다. 벤젠, 톨루엔, 에틸벤젠, 크실렌(BTEX)은 도시에 위치한 유치원에서 농도도 높고, 총 휘발성 유기화합물중 함량도 높았고, 시골지역에서는 농도와 상대적 함량이 낮았다. 도시지역에서는 총 휘발성 유기화합물 중 BTEX의 비중이 25.2%였고 정량한 13가지 유기화합물 중에서는 35.6%를 차지하였다. BTEX 각각 개별물질은 미국 환경보호청이 제시하는 일일 노출 기준량(Reference Concentration; RfC) 보다는 현저히 낮았다. 총 휘발성 유기화합물읜 농도는 실내가 실외 보다 높았다(I/O ratio 2.5). BTEX의 상대적 함량도 실내가 실외보다 높아 실내에도 발생원이 있음을 암시하고 있다. 자료 분석결과 유치원 실내의 벤젠은 실외로부터 유입되고 있었고, 톨루엔, 에틸벤젠, 크실렌은 실외뿐 아니라 실내에서도 발생하고 있었다. 정량한 8개 화합물 각각과 총 휘발성 유기화합물의 스피어만 상관계수는 벤젠을 제외하고는 모두 유의하였다. 이중 톨루엔과 크실렌은 총 휘발성 유기화합물과 좋은 상관성 (톨루엔 0.76, 크실렌, 0.87)을 나타내었다. 이 연구는 톨루엔과 크실렌이 총 휘발성 유기화합물의 좋은 지표를 사용될 있고, 톨루엔, 에틸벤젠, 크실렌 등 많은 휘발성 유기화합물의 발생원은 실외뿐 아니라 실내에도 있음을 나타내고 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10a
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• pp.297-300
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• 2001

최근의 컴퓨팅 환경은 이질적인 클라이언트와 서버들간의 상호 운용성을 요구하는 분산 어플리케이션을 위한 프로그래밍 파라다임을 지원하기 위한 분산 객체 컴퓨팅 환경으로 발전되고 있다. 여기에는 복잡한 네트워킹과 다양한 멀티미디어 응용 서비스를 위한 객체지향 기술들이 접목되고 있다. 이러한 분산 컴퓨팅 환경에서 처리되는 어플리케이션들의 실시간 서비스 지원을 위해 요구되는 실시간 특성과 분산 객체들의 관리의 어려움을 해결하기 위하여 본 논문에서는 실시간 객체그룹 플랫폼을 구축한다. 기존의 연구들은 실시간 CORBA를 사용하거나 또는 ORB를 수정하거나 실시간 운영체제상에 특정 CORBA 제품군을 사용하여 분산 환경의 특정 영역의 성능향상만을 도모하고 있다. 그러므로, 본 논문은 ORB의 수정 없이 표준 CORBA상에서 실시간 특성을 지원한 수 있는 실시간 객체그룹 플랫폼을 설계한다. 본 논문의 실시간 객체그룹 구조는 객체들의 관리적인 측면과 실시간 어플리케이션 서비스 지원 측면에 대한 요구사항들을 분석하여 정립한 모델이며, 구성요소들의 기능을 관리와 서비스로 분리하여 각각의 기능수행시에 발생하는 객체간의 상호작용이 다른 기능에 영향을 미치지 않도록 한다. 또한, 구축된 플랫폼은 실시간 어플리케이션 개발자에게 실시간 특성 파라미터의 표현과 처리에 대한 투명성을 부여하여 어플리케이션에 유연성과 확장성을 제공하기가 용이하도록 한다. 따라서, 본 논문은 실시간 객체그룹 플랫폼의 구성요소들에 대한 역할을 정의하고 기능을 정립하며, 각 구성요소들을 설계하고 구현하였으며, 구현되어진 실시간 객체그룹 플랫폼의 기능과 수행 성능을 검증한다.가지 유기화합물 중에서는 35.6%를 차지하였다. BTEX 각각 개별물질은 미국 환경보호청이 제시하는 일일 노출 기준량(Reference Concentration; RfC) 보다는 현저히 낮았다. 총 휘발성 유기화합물읜 농도는 실내가 실외 보다 높았다(I/O ratio 2.5). BTEX의 상대적 함량도 실내가 실외보다 높아 실내에도 발생원이 있음을 암시하고 있다. 자료 분석결과 유치원 실내의 벤젠은 실외로부터 유입되고 있었고, 톨루엔, 에틸벤젠, 크실렌은 실외뿐 아니라 실내에서도 발생하고 있었다. 정량한 8개 화합물 각각과 총 휘발성 유기화합물의 스피어만 상관계수는 벤젠을 제외하고는 모두 유의하였다. 이중 톨루엔과 크실렌은 총 휘발성 유기화합물과 좋은 상관성 (톨루엔 0.76, 크실렌, 0.87)을 나타내었다. 이 연구는 톨루엔과 크실렌이 총 휘발성 유기화합물의 좋은 지표를 사용될 있고, 톨루엔, 에틸벤젠, 크실렌 등 많은 휘발성 유기화합물의 발생원은 실외뿐 아니라 실내에도 있음을 나타내고 있다.>10)의 $[^{18}F]F_2$를 얻었다. 결론: $^{18}O(p,n)^{18}F$ 핵반응을 이용하여 친전자성 방사성동위원소 $[^{18}F]F_2$를 생산하였다. 표적 챔버는 알루미늄으로 제작하였으며 본 연구에서 연구된 $[^{18}F]F_2$가스는 친핵성 치환반응으로 방사성동위원소를 도입하기 어려운 다양한 방사성의 약품개발에 유용하게 이용될 수 있을 것이다.었으나 움직임 보정 후 영상을 이용하여 비교한 경우, 결합능 변화가 선조체 영역에서 국한되어 나타