• Structural Engineering and Mechanics
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• 제42권1호
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• pp.121-129
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• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.40-45
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• 2019

Unlike the welded pipes in the primary system of light water nuclear power plants being periodically inspected with in-Service inspection program, relatively small pipes with the outer diameter less than 2 inch have not been regularly inspected to date. However, after several failure reports on the occurrence of critical crack-like defects in small pipes, inspection for the small pipes has been more demanded because it could cause the provisional outage of nuclear power plants. Nevertheless, there's no particular method to examine the small pipes having access limitations for inspection due to various reasons; inaccessible area, excessive radiation exposure, hazardous surrounding, and etc. This study is to develop a reliable inspection technique using torsional and flexural modes of guided wave to detect defects that could occur in inaccessible area. The attribute of guided wave that can travel a long distance enables to inspect even isolated range of the pipe from accessible location. This paper presents a case study of the evaluation test on 3/4" small-bore pipes with guide wave method. The test result demonstrates the crack signal behavior and assures possibility to detect the crack signal in a flexural mode, which is clearly distinguishable from the symmetric structure signal in a torsional mode.

• 공업화학
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• 제8권4호
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• pp.631-636
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• 1997

흡착제로 널리 쓰이는 다공성탄소의 흡착성능을 증가시키는 연구를 수행하였다. 열처리에 의하여 다공성탄소의 흡착성능을 증가시킨 후, 유해중금속의 일종인 $Cr^{+6}$의 선택적 흡착을 시행하였다. 다공성탄소의 적정 열처리 온도는 $340{\sim}350^{\circ}C$가 가장 적절하였으며, 이때의 평균 비표면적은 Brunauer-Emmett-Teller(BET) 방법에 의해 $1380m^2/g$로 측정되었다. 열처리 과정에서 전체중량의 약 10%의 감소가 있었으나, 비표면적의 증가로 고품질의 흡착제가 되었다. 또한 열처리된 다공성탄소에 의하여 액상에서의 $Cr^{+6}$의 제거가 성공적으로 수행되었다.

• 한국대기환경학회지
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• 제22권5호
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• pp.574-589
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• 2006

Although concentrations of hazardous air pollutants(HAPs) are very low in the atmosphere, a growing attention has been paid on such compounds due to their high toxicity and bioaccumulation potentials into human body. In order to control and manage the amount of these materials in ambient air, it is necessary to construct monitoring system of them and to know the current concentration level of HAPs above all. In this work, a wide range of HAPs has been measured in metropolitan area to recognize the present state of HAPs in this area. The measured concentration of VOCs was higher in order of Jeonnongdong, Jeongdong, and Yangsuri. The regional difference of VOCs concentration was also highest in spring. Its total VOCs was ranged from $15.17{\sim}41.45$ ppb. Benzene $0.43{\sim}2.32$ ppb showed similar concentration level with the result of previous researches in Seoul. This value is a little higher than the average concentration 0.92 ppb for national ambient air quality standards in Japan. The concentration of aldehydes in this study was lower than those of other researches. Previous works in Seoul metropolitan area showed that the concentration of formaldehyde and acetaldehyde were higher than 5 ppb. The concentration of gaseous and particulate PAHs was high in order of winter, spring, and summer More than 90% of PAHs with low molecular weight such as 2-rings and 3-rings PAHs existed in gas phase. On the other hands, PAHs with high molecular weight more than 5-rings PAHs almost existed in particulate. In spring, the concentration of gaseous PAHs was 24.38 $ng/m^3$ in Jeongdong. Among the particulate PAHs, the concentrations of Naphthalene, Benzo(b)fluoranthene, and Benzo(g, h, i)perylene were higher than others. Especially, the concentration of Benzo(a)pyrene, a important carcinogenic pollutant, was highest in winter 0.5 $ng/m^3$ and ranged from 0.03 to 0.3 $ng/m^3$ in spring and summer, which is lower than the monitoring result in 90's. These components were mainly originated from the vehicle exhaust or heating equipment use.

• 한국산업보건학회지
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• 제21권1호
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• pp.11-24
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• 2011

Working in a research laboratory means exposure to a wide range of hazardous substances. Several studies indicated that laboratory workers, especially working with chemicals, might have an increased risk of certain cancers. However, exposure assessment data in laboratory settings are scarce. This study was performed to examine several approaches for quantitatively assessing the exposure levels to volatile organic compounds (VOCs) among workers in chemistry laboratories. The list of 10 target VOCs, including ethanol, acetone, 2-propanol, dichlormethane, tetrahydrofuran, benzene, toluene, n-hexane, ethyl acetate, chloroform, was determined through self-administered questionnaire for six chemistry research laboratories in a university, a government-funded research institute, or private labs. From September to December 2008, 84 air samples were collected (15 area samples, 27 personal time weighted samples, 42 personal task-basis short-term samples). Real time monitors with photo ionization detector were placed during the sampling periods. In this study, benzene was observed exceeding the action levels, although all the results were below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV). From the air sampling results, we concluded that (1) chemicals emitted during experiments could directly affect to neighbor office areas (2) chemical exposures in research laboratories showed a wide range of concentrations depending on research activities (3) area samples tended to underestimate the exposures relative to personal samples. Still, further investigation, is necessary for developing exposure assessment strategies specific to laboratories with unique exposure profiles.

• 한국지리정보학회지
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• 제13권4호
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• pp.67-77
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• 2010

석유화학산업의 성장으로 석유화학물의 수송량이 증가하였다. 이는 위험물 사고건수의 증가를 초래하였다. 위험물 사고의 70% 이상이 수송 중 발생하며, 경로선택과정에서 수송경로의 선택에 따라 피해규모를 줄일 수 있지만 위험물 수송경로관련 연구는 미비한 실정이다. 본 연구의 목적은 전문가의 의견을 반영한 적정 위험물 수송경로의 선정을 통해 사고 발생시 피해규모를 최소화 하는데 있다. 이에 계층분석법(AHP)을 통하여 도출된 가중치를 위험도에 적용하여 최소 위험도 경로를 도출하였다. 그 결과 가중치 적용 경로의 경우 최단경로에 비해 인구위험도는 33.4%인 0.608, 환경위험도는 21.8% 감소한 0.168, 사회위험도는 1521.7%인 0.35가 감소하였다. 가중치 미적용 노선과 가중치 적용 노선을 비교하면, 가중치 적용 노선의 인구위험도는 2.6% 감소하였다. 본 연구를 통해 전문가의 의견을 반영한 가중치의 적용으로 위험도를 감소시키면서 인구피해규모를 최소화 하는 최적경로를 도출할 수 있었다.

• 전기학회논문지
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• 제60권3호
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• pp.669-673
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• 2011

This study explores the numerical analysis method of fluid dynamics in the reaction section to improve the gas processing efficiency in the hazardous gas removal by atmospheric thermal plasma. This study also intends to contribute in technology advance to improve the processing efficiency and make the process more stable. Numerical analysis of temperature distribution in the reaction section dependent on the change in flow velocity of Ar and plasma temperature change, which are major control variables in the cracking process of HFC-23 using arc plasma, was done. The characteristic of incoming oxygen by temperature suggested that when temperature increased to 1600K, 1700K, 1800K respectively, the range of cracking temperature 1500K increased to 75.0%, 83.3%, 90.2% respectively. The temperature change of Ar by velocity change was widest in the area higher than 1500K when the velocity was 2.5m/s; however, since there was no big difference when the velocity was 2m/s, it is believed that 2 m/s would be most proper.

• 대한안전경영과학회지
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• 제12권1호
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• pp.11-18
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• 2010

In the steel industry, steel is manufactured and processed to produce a variety of steel products. The industry provides fundamental materials to the whole range of industries including car, ship, electric appliance and construction industries, so that it is very important as an infrastructure industry. The steel manufacture process involves aerial work, many danger factors caused by the treatment with hazardous gases including BFG and COG and by high pressure gases including $H_2$, $O_2$, $N_2$ and LPG. It requires the management over the large area because many workers work in a plant. The potential dangers in the steel plant were identified and the effect of the danger assessment was verified through the analysis of the danger assessment for the steel plant. The allowed degree of danger was lowered after the improvement through the danger assessment in the plant where the case studies were conducted, which indicates that the danger assessment is highly effective.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.733-738
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• 2017

본 연구에서는 여러 사업장에서 많이 사용되는 대표적 독성 물질인 염소를 누출 물질로 선정하여 화학사고 통계자료에 따라 사고 발생 빈도가 높은 여름철 기상조건을 인자로 한 대안의 시나리오와 기존의 시행방법인 연평균 기상조건을 인자로 한 대안의 시나리오 비교분석을 통해 개선방안을 제시하고자 하였다. 2014년 1월부터 2016년 12월까지 발생한 총 296건의 화학 사고를 분석한 결과 사계절 중 여름에 가장 많은 사고가 발생하는 것으로 조사되었으며 전체 사고 발생건수의 35.81%를 차지하였다. 실제 염소를 취급하는 사업장을 대상으로 위험성 평가 결과 2016년의 경우 연평균 기상조건하에서 산출된 영향범위는 발생원으로부터 반경 712.4 m, 영향범위 내 주민 수는 20,090 명이였으며, 여름철 평균 기상조건하에서 산출된 영향범위는 발생원으로부터 반경 796.2 m, 영향범위 내 주민 수는 27,143 명으로 나타났다. 이와 같은 결과는 특정 조건하에서 현 대안의 시나리오 상의 영향범위가 포괄할 수 없는 부분이 존재함을 의미한다. 따라서 화학 물질별 특성을 고려한 Case Risk Assessment가 이루어져야 한다는 위험성 평가 제도의 발전방향을 제시한다.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.324-335
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• 2024

The container package type sealed water electrolysis production system installs mechanical balance of plant and electrical balance of plant as an integrated unit to enable independent operation within the package module. The auxiliary equipment required to operate the water electrolysis system must be integrated to reduce the installation area and shorten the installation time. At this time, as leak risk factors are placed in a dense space, when a hydrogen gas leak accident occurs, it can have a mutual influence on other adjacent facilities, so it contains various risk factors. In this study, when a gas leak occurs in a container packaged water electrolysis system, possible sources of leakage in the system according to the KS C IEC 60079-10-1:2015 and KGS GC101 standards were identified, and the leak rate and leak characteristics were calculated. did. The hazardous area and its range were calculated according to ventilation and dilution characteristics. In order to optimize ventilation characteristics, design of experiment was used to analyze the influence to evaluate the adequacy of ventilation, and overseas ventilation standards were analyzed and compared. In addition, the optimal ventilation structure and characteristics of the container packaged water electrolysis system were presented according to the results of the experimental design method.