• 한국산업보건학회지
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• 제11권2호
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• pp.102-110
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• 2001

To establish an accurate asbestos analysis method for workplace samples, chrysotile, amosite, crocidolite, tremolite, actinolite, and anthophyllite asbestos fibers were analyzed for their morphology, atomic content and electron diffraction patterns. The morphology of asbestos fiber was evaluated in $10,000{\times}$ magnification. The atomic contents was analyzed by X-ray analyzer (TEM-EDX). Asbestos fibers were further assessed using electron diffraction (ED) patterns to provide an additional criterion for classifying the asbestos fibers. Twenty asbestos fibers were initially randomly selected for morphological evaluation; based on an aspect ratio (length : diameter = 3:1). Then the fibers were determined for their EDX spectrums and ED patterns. Our results showed that only chrysotile fiber has a hollow tube structure to be distinguished from other asbestos fibers. Although asbestos fibers had similar morphology, they had different EDX spectrums and ED patterns. Our results on the atomic content of asbestos fibers were very similar to those of other researchers, but amosite and crocidolite had a little difference in atomic content compared with the results from other researchers. The difference may be due to the difference in equipment or asbestos sample selection. A study on asbestos samples from biological specimens to establish a criterion for determining occupational asbestos exposed diseases should be done in the near future.

• 해양환경안전학회지
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• 제24권3호
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• pp.332-338
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• 2018

To perform the Maritime Safety Audi Scheme, $10^{-4}$ was constantly applied without adjustment when evaluating the proximity of the fairway. The necessity of applying the different aberrancy probabilities from the different proximity of the fairway depending on the shape of the route and the size of the ship was validated using marine simulations. Marine simulation was performed to evaluate the validity of statistical analysis-based aberrancy probability according to the different shapes of routes and ship size presented in the previous study. As results, the validity of the criterion of the statistical analysis-based aberrancy probability was confirmed by comparing with the results of simulation-based aberrancy probabilities. The results support that the aberrancy probabilities by the types of a vessel could be different based on the type and size of vessels. The results motivate that further investigation is required to find the reasonable criteria of the aberrancy probabilities for the maritime traffic safety audit according to the fairway shape and the size of the vessel.

• 산업공학
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• 제25권4호
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• pp.422-430
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• 2012

In this article, we introduced the estimation method by 'Safety Integrity Level'(SIL) for the criterion of safety assurance and performed a case study on a flame scanner. SIL requires probabilistic evaluation of each set of equipment used to reduce risk in a safety related system. FMEDA(Failure Modes, Effects and Diagnostic Analysis) method is widely used to evaluate the safety levels and provides information on the failure rates and failure mode distributions necessary to calculate a diagnostic coverage factor for a part or a component. Basically, two parameters resulting from FMEDA are used for SIL classification of the device : SFF(Safe Failure Fraction) and PFD(Probability of Failure on Demand). In this case study, it is concluded that the flame scanner is designed to fulfill the condition of SIL 3 in the aspect of SFF and PFD.

• Structural Engineering and Mechanics
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• 제41권4호
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• pp.495-508
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• 2012

The strength theory of concrete is significant to structure design and nonlinear finite element analysis of concrete structures because concrete utilized in engineering is usually subject to the action of multi-axial stress. Experimental results have revealed that lightweight aggregate (LWA) concrete exhibits plastic flow plateau under high compressive stress and most of the lightweight aggregates are crushed at this stage. For the purpose of safety, therefore, in the practical application the strength of LWA concrete at the plastic flow plateau stage should be regarded as the ultimate strength under multi-axial compressive stress state. With consideration of the strength criterion, the ultimate strength surface of LWA concrete under multi-axial stress intersects with the hydrostatic stress axis at two different points, which is completely different from that of the normal weight concrete as that the ultimate strength surface is open-ended. As a result, the strength criteria aimed at normal weight concrete do not fit LWA concrete. In the present paper, a multi-axial strength criterion for LWA concrete is proposed based on the Unified Twin-Shear Strength (UTSS) theory developed by Prof Yu (Yu et al. 1992), which takes into account the above strength characteristics of LWA under high compressive stress level. In this strength criterion model, the tensile and compressive meridians as well as the ultimate strength envelopes in deviatoric plane under different hydrostatic stress are established just in terms of a few characteristic stress states, i.e., the uniaxial tensile strength $f_t$, the uniaxial compressive strength $f_c$, and the equibiaxial compressive $f_{bc}$. The developed model was confirmed to agree well with experimental data under different stress ratios of LWA concrete.

• 컴퓨터교육학회논문지
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• 제22권5호
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• pp.39-50
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• 2019

본 연구에서는 중학교 SW교육에 활용할 수 있는 피지컬 컴퓨팅 교구의 선정을 위한 기준을 개발하였다. 교구를 선정하기 위한 기준을 개발하기 위하여 문헌 분석, 델파이 설문 실시와 AHP 방법을 적용하였다. 먼저 문헌을 통해 피지컬 컴퓨팅 교구가 갖추어야 할 특성을 '교육과정 적합성', '안전성', '내구성', '경제성', '범용성', '매력성', '관리의 용이성' 7개의 영역으로 설정하고 전문가 델파이 설문을 통해 영역별 세부 기준을 도출하여 7개 영역의 31개 세부 기준으로 구성된 피지컬 컴퓨팅 교구의 선정 기준을 제안하였다. 이렇게 제안된 선정 기준에 대해 추가로 AHP 방법을 적용하여 7개의 영역과 31개의 세부 기준에 대한 상대적 중요도를 분석하고 이를 바탕으로 세부 기준별 배점을 계산하여 정량화된 피지컬 컴퓨팅 교구의 선정 기준을 개발하였다.

• 한국안전학회지
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• 제38권3호
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• pp.61-68
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• 2023

This study performed a structural performance evaluation of a system scaffolding for elevator installation work developed in previous studies. The structural performance was evaluated via a structural test conducted to apply the working load specified in the design standard. The deflection of the horizontal member and the stress of each member constituting the system scaffolding were measured. Consequently, the structural safety evaluation including structural behavior and required performance was performed using the deflection and stresses measured from the structural test. The structural test and safety evaluation results based on the heavy working load corresponding to the design load indicated that the deflection, which is the performance criterion of the horizontal member, did not exceed the allowable value. Further, each member's stress, which is a safety evaluation indicator, did not exceed the allowable strength for both horizontal and vertical members with bending behavior and fordable bracing with tensile behavior, while also satisfying the required safety factor. In addition, the results confirmed the safety against deformation, partial damage, and destruction owing to excessive and maximum load. Therefore, the system scaffolding developed in this study satisfies both the structural performance and safety required by the design standards; thus, it can be applied to elevator installation work sites.

• 해양환경안전학회지
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• 제18권5호
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• pp.431-438
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• 2012

해상교통환경의 위험도를 평가하기 위한 기술로는 대표적으로 FSA, PAWSA, IWRAP 등이 있으며, 이러한 기술의 개발을 위해서는 해상교통환경에 적합한 위험요소를 선정하고 이에 대한 평가기준이 마련되어야 한다. 기존 기술에서 위험도는 사고의 출현빈도와 이로 인한 영향의 곱으로 정의되어 이에 따라 사고의 출현빈도 및 영향에 해당되는 위험요소들이 각각 구분되어 선정되고 있었다. 그러나, 본 연구는 각 위험요소에 요소별 출현빈도와 영향을 포함하여 이들의 합으로 위험도를 정의함으로써 기존 기술에서 사고의 영향에 해당되었던 위험요소들을 제외하는 한편, 위험요소 분류체계에 관한 기존 연구의 사례 검토를 통하여 위험도를 구성하는 위험요소를 20가지로 추출한 후 유사한 성격에 따라 5가지 카테고리로 분류하였다. 또한, 선정된 각 위험요소에 대하여 관련 통계자료 등을 이용 실용적으로 용이하게 평가할 수 있는 기준을 제시하여, 향후 국내 해상교통환경에 적합한 위험도 평가모델의 개발을 위한 기초를 마련하였다.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.125-132
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• 2007

In order to provide consumers with safety informations of vehicles according to the Korean New Car Assessment Program(KNCAP), the evaluation results and the star ratings of 21 vehicles for the side impact tests have been reported since 2003. Now, the KNCAP considers changing the side impact dummy from EuroSID-1 to EuroSID-2 near future. The rib deflection of EuroSID-2 is 20-30% higher than that of EuroSID-1 because of the removal of "Flat Tops" effect. In this study, the effect of changing the side impact dummy from EuroSID-1 to EuroSID-2 in the KNCAP side impact evaluation is estimated through the previous KNCAP evaluation results. The results show that the decrease of the star ratings would be one star($\bigstar$) approximately.

• Geomechanics and Engineering
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• 제13권2호
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• pp.301-318
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• 2017

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

• 한국안전학회지
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• 제24권3호
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• pp.59-64
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• 2009

This study was conducted in order to investigate prevalence of musculoskeletal disorders(MSDs) for farmers. The study was based on self-reporting questionnaire. The MSDs prevalence was ascertained by using three criteria, which are known as NIOSH criteria 1, 2 and 3. The results showed that the prevalences of MSDs in at least one body site by criteria 1, 2 and 3 were 96.4%, 66.7% and 26.2%, respectively. The MSDs prevalences for the shoulder by criterion 1 was the highest, followed by the lower back, neck, while the rates for the hip, feet and fingers were relatively low. Farmers' age, types of corps, working hours/day, length of service and length of service in current corps were not significant on the MSDs prevalences, except that types of corps and length of service in current corps were significant on the MSDs prevalences by criterion 2(p