• 한국지반공학회논문집
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• 제39권6호
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• pp.5-12
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• 2023

산사태 위험 지역을 사전에 조사하여 설정하는 것은 다수의 피해를 줄이기 위해 필요하다. 해당 연구의 목적은 machine learning 기법 중 분류 알고리즘을 활용하여 대상 지반의 안전율 분류를 수행할 수 있는 방법론을 제시하는 것이다. 산사태 위험 지역은 high risk area(HRA) 모델을 적용하였으며, 8개의 지반공학 물성치를 통해 위험 지역을 판단하였다. 분류 알고리즘은 decision tree(DT), K-Nearest Neighbor(KNN), logistic regression(LR) 그리고 random forest(RF)의 4가지가 활용 되었으며, 안전율 1.2~2.0 범위에 8가지 지반공학 물성치의 분류 정확도를 계산하였다. 정확도는 안전율이 1.2~1.7 범위에서 신뢰성 높게 나타났지만, 그 외 범위인 1.8~2.0 사이에서는 상대적으로 낮은 정확도를 보였다. 이를 극복하기 위하여 synthetic minority over-sampling technique(SMOTE) 알고리즘을 적용하여 데이터 개수를 증폭하였으며, 증폭한 데이터를 통해 분류 알고리즘을 적용하면 안전율 1.8~2.0 범위에서 정확도가 평균적으로 약 250% 증가한 것으로 나타났다. 해당 연구 결과는 SMOTE 알고리즘이 데이터 개수를 향상시켜 분류 알고리즘의 정확도가 개선된 것을 보여주며, 타 분야에도 정확도 향상에 적용 가능하다고 판단된다.

• Safety and Health at Work
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• 제7권2호
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• pp.124-129
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• 2016

Background: Work-related fatigue has a strong impact on performance and safety but so far, no agreed upon method exists to detect and quantify it. It has been suggested that work-related fatigue cannot be quantified with just one test alone, possibly because fatigue is not a uniform construct. The purpose of this study is therefore to measure work-related fatigue with multiple tests and then to determine the underlying factorial structure. Methods: Twenty-eight employees (mean: 36.11; standard deviation 13.17) participated in five common fatigue tests, namely, posturography, heart rate variability, distributed attention, simple reaction time, and subjective fatigue before and after work. To evaluate changes from morning to afternoon, t tests were conducted. For further data analysis, the differences between afternoon and morning scores for each outcome measure and participant (${\Delta}$ scores) were submitted to factor analysis with varimax rotation and each factor with the highest-loading outcome measure was selected. The ${\Delta}$ scores from tests with single and multiple outcome measures were submitted for a further factor analysis with varimax rotation. Results: The statistical analysis of the multiple tests determine a factorial structure with three factors: The first factor is best represented by center of pressure (COP) path length, COP confidence area, and simple reaction time. The second factor is associated with root mean square of successive difference and useful field of view (UFOV). The third factor is represented by the single ${\Delta}$ score of subjective fatigue. Conclusion: Work-related fatigue is a multidimensional phenomenon that should be assessed by multiple tests. Based on data structure and practicability, we recommend carrying out further studies to assess work-related fatigue with manual reaction time and UFOV Subtest 2.

• 한국안전학회지
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• 제35권6호
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• pp.1-8
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• 2020

In recent years, hydrogen has received much attention as an alternative energy source to fossil fuels. In order to ensure safety from the increasing number of hydrogen refueling stations, prevention methods have been required. In this regard, this study suggested an approach to reduce the risk of hydrogen refueling station by increasing Safety Integrity Level (SIL) for a Steam Methane Reformer (SMR) in On-Site Hydrogen Refueling Station. The worst scenario in the SMR was selected by HAZOP and the required SIL for the worst scenario was identified by LOPA. To verify the required SIL, the PFDavg.(1/RRF) of Safety Instrumented System (SIS) in SMR was calculated by using realistic failure rate data of SIS. Next, several conditions were tested by varying the sensor redundancy and proof test interval reduction and their effects on risk reduction factor were investigated. Consequently, an improved condition, which were the redundancy of two-out-of-three and the proof test interval of twelve months, achieved the tolerable risk resulting in the magnitude of risk reduction factor ten times greater than that of the baseline condition.

• Journal of Sport and Applied Science
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• 제5권1호
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• pp.11-15
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• 2021

Purpose: Swimming industry is improving faster than the other types of sport industries and populations of participating swimming are promptly increasing. Lack of recognition of fire safety in swimming facilities is issues related-studies has only recently begun to pay attention. This study is to review and extract fire safety factors for managing swimming pool. Research design, data, and methodology: The study reviewed related-ordinances, governmental documents, and studies discussing safety management of sport facility. Given the literature review, the study produced an initial construct presenting items and factors including fire safety elements and experts' review were conducted to ensure conceptual validity. Finally, the study generated the final factors and subitems representing fire safety elements for swimming pool management. Results: The study confirms factors and elements as follows: the study identifies fire safety equipments as first factors presenting fire extinguisher' place, its proper run, check list and so forth, Second factor is warning system including fire warning equipment, its proper operation, sprinkler and its proper operation, switch and lamp of emergency panel and their proper run and so on. Third factor is evacuation system including a fire exit, exit sign, broadcasting equipment, and their proper operation, and so on. The other factors are an electronic equipment and its subelements, gas management including safety management of LPG, gas valve, pipe, and fire prevention facility including a fire door and its proper operating. Conclusions: Regarding safety management of swimming pool, further discussions and implications were made, and future directions for related-studies were discussed.

• Geomechanics and Engineering
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• 제37권6호
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• pp.599-614
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• 2024

To evaluate the safety status of deteriorated segments in a submarine shield tunnel during its service life, a seepage model was established based on a cross-sea shield tunnel project. This model was used to study the migration patterns of erosive ions within the shield segments. Based on these laws, the degree of deterioration of the segments was determined. Using the derived analytical solution, the internal forces within the segments were calculated. Lastly, by applying the formula for calculating safety factors, the variation trends in the safety factors of segments with different degrees of deterioration were obtained. The findings demonstrate that corrosive seawater presents the evolution characteristics of continuous seepage from the outside to the inside of the tunnel. The nearby seepage field shows locally concentrated characteristics when there is leakage at the joint, which causes the seepage field's depth and scope to significantly increase. The chlorine ion content decreases gradually with the increase of the distance from the outer surface of the tunnel. The penetration of erosion ions in the segment is facilitated by the presence of water pressure. The ion content of the entire ring segment lining structure is related in the following order: vault < haunch < springing. The difference in the segment's rate of increase in chlorine ion content decreases as service time increases. Based on the analytical solution calculation, the segment's safety factor drops more when the joint leaks than when its intact, and the change rate between the two states exhibits a general downward trend. The safety factor shows a similar change rule at different water depths and continuously decreases at the same segment position as the water depth increases. The three phases of "sudden drop-rise-stability" are represented by a "spoon-shaped" change rule on the safety factor's change curve. The issue of the poor applicability of indicators in earlier studies is resolved by the analytical solution, which only requires determining the loss degree of the segment lining's effective bearing thickness to calculate the safety factor of any cross-section of the shield tunnel. The analytical solution's computation results, however, have some safety margins and are cautious. The process of establishing the evaluation model indicates that the secondary lining made of molded concrete can also have its safety status assessed using the analytical solution. It is very important for the safe operation of the tunnel and the safety of people's property and has a wide range of applications.

• Geomechanics and Engineering
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• 제6권2호
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• pp.99-115
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• 2014

Uncertainties in design variables and design equations have a significant impact on the safety of geotechnical structures like retaining walls and slopes. This paper presents a possible framework for obtaining the partial safety factors based on reliability approach for different random variables affecting the stability of a reinforced concrete cantilever retaining wall and a slope under static loading conditions. Reliability analysis is carried out by Mean First Order Second Moment Method, Point Estimate Method, Monte Carlo Simulation and Response Surface Methodology. A target reliability index ${\beta}$ = 3 is set and partial safety factors for each random variable are calculated based on different coefficient of variations of the random variables. The study shows that although deterministic analysis reveals a safety factor greater than 1.5 which is considered to be safe in conventional approach, reliability analysis indicates quite high failure probability due to variation of soil properties. The results also reveal that a higher factor of safety is required for internal friction angle ${\varphi}$, while almost negligible values of safety factors are required for soil unit weight ${\gamma}$ in case of cantilever retaining wall and soil unit weight ${\gamma}$ and cohesion c in case of slope. Importance of partial safety factors is shown by analyzing two simple geotechnical structures. However, it can be applied for any complex system to achieve economization.

• 융복합기술연구소 논문집
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• 제9권1호
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• pp.25-30
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• 2019

Normal cranes cannot be used to move the fan inside the high-rise factories. Due to the size of the fan and safety accidents, there is a need for a structure capable of lifting and transporting. In this study, the safety of the structure was evaluated by considering the center of gravity of the fan and the effect of the fan being tilted up. An analysis of the buckling was performed by hand calculation. Nonlinear analysis was performed using ABAQUS to evaluate the safety of the structure. The safety factor for buckling is above 4.0 and the safety factor for stress is calculated to be 1.31 under the worst load distribution conditions.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1989년도 가을 학술발표회 논문집
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• pp.40-45
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• 1989

In order to take account of the statistical properties of random variables used in the structural analysis, the conventional approach usually adopts the safety factor based on past experiences for the qualitative assessment of structural safety problem. Recently, new approach based on the probabilistic concept has been applied to the assessment of structural safety in order to circumvent the difficulties of the conventional approach in choosing the appropriate safety factor. Thus, computer program called "Probabilistic finite element method" is developed by incorporation the probabilistic concept into the conventional matrix method in order to investigate the effects of the random variables on the final output of the structural analysis. From the comparison of some examples, it can be concluded that the PFEM developed in this study deals with consistently with the uncertainty of random variables and provides the rational tool for the assessment of structural safety of plane frame.

• Nuclear Engineering and Technology
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• 제36권4호
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• pp.364-373
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• 2004

This study investigates the fluidelastic instability characteristics of helical steam generator type tubes used in operating nuclear power plants. To obtain a natural frequency, corresponding mode shape, and participation factor, modal analyses using various conditions are performed for helical type tubes. Investigated are the effects of the number of turns, the number of supports, and the status of the inner fluid on the modal and fluidelastic instability characteristics of the tubes, which are expressed in terms of the natural frequency, the corresponding mode shape, and the stability ratio.

• Safety and Health at Work
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• 제5권2호
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• pp.60-65
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• 2014

Background: To elucidate the relationship between safety culture maturity and safety performance of a particular company. Methods: To identify the factors that contribute to a safety culture, a survey questionnaire was created based mainly on the studies of $Fern{\acute{a}}ndez-Mu{\tilde{n}}iz$ et al. The survey was randomly distributed to 1000 employees of two oil companies and realized a rate of valid answer of 51%. Minitab 16 software was used and diverse tests, including the descriptive statistical analysis, factor analysis, reliability analysis, mean analysis, and correlation, were used for the analysis of data. Ten factors were extracted using the analysis of factor to represent safety culture and safety performance. Results: The results of this study showed that the managers' commitment, training, incentives, communication, and employee involvement are the priority domains on which it is necessary to stress the effort of improvement, where they had all the descriptive average values lower than 3.0 at the level of Company B. Furthermore, the results also showed that the safety culture influences the safety performance of the company. Therefore, Company A with a good safety culture (the descriptive average values more than 4.0), is more successful than Company B in terms of accident rates. Conclusion: The comparison between the two petrochemical plants of the group Sonatrach confirms these results in which Company A, the managers of which are English and Norwegian, distinguishes itself by the maturity of their safety culture has significantly higher evaluations than the company B, who is constituted of Algerian staff, in terms of safety management practices and safety performance.