• Nuclear Engineering and Technology
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• 제36권4호
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• pp.327-337
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• 2004

It is commonly required that tubes with defects exceeding $40\%$ of wall thickness in depth should be plugged; however, this criterion is too conservative for some locations and for some types of defects. Many studies have been done with the aim of developing an alternative plugging criteria, and these studies have shown that steam generator tubes with a certain range of axial through-wall cracks could remain in service without any safety or reliability problems. However, these studies have been limited, thus far, to consideration of single cracked tubes, necessitating a study on multiple cracks, which are commonly found. A crack coalescence model applicable to steam generator tubes with two collinear axial through-wall cracks was proposed in the previous study. In this paper, the investigation is extended to the parallel axial cracks spaced in a circumferential direction, because parallel axial cracks are more frequently detected during in-service inspections than collinear axial cracks. Interaction effects between two parallel cracks are evaluated by performing elastic and elastic-plastic finite element analyses.

• 한국산업융합학회 논문집
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• 제27권4_2호
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• pp.897-908
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• 2024

Evaluating the adequacy of facility safety inspection and diagnosis services performed by private enterprises is a time-consuming and administratively complex process. This study aims to analyze the determinants that could influence the rating of these safety inspection and diagnosis services using data analytics approach. Through a comparative analysis of several machine learning algorithms suitable for multi-class classification, we selected the model with the best performance (Random Forest) and identified the main determinants using the permutation importance technique. Among the variables examined, "contract value," "days of service performed" and "adherence to fair market value" were found to be strongly correlated with the rating assessments. Furthermore, we discovered that the skills and expertise of service performing personnel significantly impacted the rating. The results of this study can contribute to the enhancement of the current post-evaluation administrative processes and offer valuable insights into rating assessments by incorporating previously unexplored variables pertaining to both service providers and the services itself.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.87-95
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• 2020

Generally, occupational safety and particularly construction safety is an intricate phenomenon. Industry professionals have devoted vital attention to enforcing Occupational Safety and Health (OHS) from the last three decades to enhance safety management in construction. Despite the efforts of the safety professionals and government agencies, current safety management still relies on manual inspections which are infrequent, time-consuming and prone to error. Extensive research has been carried out to deal with high fatality rates confronting by the construction industry. Sensor systems, visualization-based technologies, and tracking techniques have been deployed by researchers in the last decade. Recently in the construction industry, computer vision has attracted significant attention worldwide. However, the literature revealed the narrow scope of the computer vision technology for safety management, hence, broad scope research for safety monitoring is desired to attain a complete automatic job site monitoring. With this regard, the development of a broader scope computer vision-based risk recognition system for correlation detection between the construction entities is inevitable. For this purpose, a detailed analysis has been conducted and related rules which depict the correlations (positive and negative) between the construction entities were extracted. Deep learning supported Mask R-CNN algorithm is applied to train the model. As proof of concept, a prototype is developed based on real scenarios. The proposed approach is expected to enhance the effectiveness of safety inspection and reduce the encountered burden on safety managers. It is anticipated that this approach may enable a reduction in injuries and fatalities by implementing the exact relevant safety rules and will contribute to enhance the overall safety management and monitoring performance.

• 한국구조물진단유지관리공학회 논문집
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• 제14권6호
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• pp.246-253
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• 2010

시설물의 안전관리에 관한 특별법이 1995년 제정된 이후 정밀점검 및 정밀안전진단을 실시하여 국가의 주요시설물의 안전 확보에 기여해 왔다. 그러나 관리주체의 안전등급 판정 개입, 안전진단전문기관의 저가수주, 진단기술력 부족 등으로 점검 진단의 실효성에 관한 의문이 꾸준히 제기되어 왔다. 이에 평가제도가 도입되어 부실 점검 진단 방지로서 역할과 기능을 하고 있지만, 앞으로 부실 점검 진단비율을 더 이상 낮아지기 힘들다는 의견이 대두되고 있다. 따라서 현행 평가제도와 부실 점검 진단비율에 대한 현황 분석을 실시하고, 부실 점검 진단으로 인한 국가적 손실비용을 추정함으로서 현행 평가제도 개선의 필요성과 당위성을 제시하고자 하였다.

• 한국안전학회지
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• 제37권5호
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• pp.89-99
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• 2022

This study was conducted to provide basic data for establishing safety management measures, which facilitate accident prevention, in the institutions that were subject to the regulations that pertain to the maintenance of a safe laboratory environment. The data was collected between 2018 and 2020, and it was analyzed to establish the effectiveness of the laboratory safety management measures that focus on universities, research institutes, and business-affiliated research institutes. Consequently, the level of compliance with the regulations and the size of the institution influenced the accident rate. More specifically, the accident rate increased when an institution was subject to risk factors, or when the institution failed to conduct routine and regular inspections. Furthermore, it was observed that institutions where accidents occurred exhibited a lower level of completion in regard to safety education for laboratory directors and research workers than those in which no accidents occurred. Finally, it was observed that the number of researchers, laboratories, in-depth safety inspection laboratories, and the level of safety management expenses were higher in the institutions where accidents occurred than in the institutions in which no accidents occurred.

• 한국항행학회논문지
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• 제26권6호
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• pp.528-535
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• 2022

항공기 제작 및 운송 기술 발달로 국내 항공산업은 비약적인 발전을 이루었으나, 항공안전 사고는 지속해서 발생하고 있다. 관리 감독기관에서는 위험기반 항공안전데이터를 기반으로 위해 요인과 위험도를 분류하고, 운송사업자별 안전 경향성 파악과 취약분야를 도출하여 사전점검을 수행함으로써 사건·사고를 사전 예방중에 있다. 그러나 자연어 형식으로 기술된 항공안전데이터의 휴먼 분류는 지식과 경험, 성향에 따라 서로 다른 분류 결과를 초래하고, 이벤트 내용의 의미 파악 및 분류를 위한 작업에 상당한 시간을 소요케 한다. 이에, 본 논문에서는 KoBERT 모델을 fine-tunning하고 5천 건 이상의 항공안전데이터를 기계학습 시켜 신규 데이터의 분류 값을 예측한 결과 79.2%의 정확성을 보였다. 그리고 유사 이벤트에 대해 동일한 결과 예측과 fail 된 데이터 중 일부는 휴먼 에러에 의한 오류임을 확인할 수 있었다.

• 한국화재소방학회논문지
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• 제28권4호
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• pp.21-28
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• 2014

단상 2선식 MCCB의 관련 기준을 분석하고, 내열 특성을 평가하여 다음과 같은 결과를 얻었다. KS C 8321은 IEC 60947-2의 규격을 부합화되어 관련 규정 대부분이 유사하다. NFPA는 사용자 중심의 안전 규정을 제시한 것으로 시험 또는 검사 등의 세부 사항은 없으나 안전에 직접 관련이 있는 규정이 구체적으로 명시되어 있다. KS C 8321은 시험과 검사에 대한 항목이 세부적으로 분류되어 있는 것을 알 수 있다. 그러나 IEC 60947-2와 IEEE C37.51의 경우 시험 및 검사 항목을 간소화하거나 일부 생략되어 있다. 내열 실험 장치를 이용하여 MCCB를 $180^{\circ}C$에서 6 hr 동안 열적 스트레스를 인가하였을 때 작동 손잡이의 변형이 확인되었고, 트립 상태로 이동한 것이 확인되었다. 또한 고정걸이의 대부분은 녹아서 기능이 상실되었다. $90^{\circ}C$에서 MCCB가 열적 스트레스를 받았을 때 특이 사항이 없었고, $105^{\circ}C$ 및 $120^{\circ}C$의 온도에서는 고정걸이가 일부 변형되었다. $150^{\circ}C$에서는 고정걸이의 변형 및 명판의 변색 등을 확인할 수 있었다. MCCB의 내부 분석에서 트립바가 녹아서 없어진 것을 알 수 있었고, 상하 가동편은 상부로 이동한 것이 확인되었다. 내전압 6 kV를 60 s 동안 5회 인가한 실험에서 모든 항목이 안전하였다. 또한 절연저항계로 직류 500 V를 인가한 절연 성능 평가 역시 양호하였다.

• 한국BIM학회 논문집
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• 제6권2호
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• pp.29-38
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• 2016

Road bridges are deteriorating gradually, and it is forecasted that the number of road bridges aging over 30 years will increase by more than 3 times of the current number. To maintain road bridges in a safe condition, current safety conditions of the bridges must be estimated for repair or reinforcement. However, budget and professional manpower required to perform in-depth inspections of road bridges are limited. This study proposes an estimation model for safety rating of road bridges by analyzing the data from Facility Management System (FMS) and Yearbook of Road Bridges and Tunnel. These data include basic specifications, year of completion, traffic, safety rating, and others. The distribution of safety rating was imbalanced, indicating 91% of road bridges have safety ratings of A or B. To improve classification performance, five safety ratings were integrated into two classes of G (good, A and B) and P (poor ratings under C). This rearrangement was set because facilities with ratings under C are required to be repaired or reinforced to recover their original functionality. 70% of the original data were used as training data, while the other 30% were used for validation. Data of class P in the training data were oversampled by 3 times, and Repeated Incremental Pruning to Produce Error Reduction (RIPPER) algorithm was used to develop the estimation model. The results of estimation model showed overall accuracy of 84.8%, true positive rate of 67.3%, and 29 classification rule. Year of completion was identified as the most critical factor on affecting lower safety ratings of bridges.

• 한국가스학회지
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• 제13권2호
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• pp.49-56
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• 2009

본 연구에서는 국내외 LPG 자동차 보급 및 안전관리현황 비교 분석을 통해 국내 LPG 자동차 관련 안전성확보 방향을 제시하였다. 국내 LPG 자동차에 대한 안전관리실태 조사결과 LPG 자동차의 안전성 확보를 위한 제도와 관리실태가 미흡하였고, 실제 약 5천여대의 LPG 자동차에 대한 가스누출 점검결과 약 4% 정도가 누출되고 있음을 확인하였다. 또한 LPG 자동차 관련 안전성향상을 위해 국외에서 운영중인 안전기준을 국내에 적용할 필요성을 확인하였다. 따라서, 국내 LPG 자동차 관련 안전성확보 방향으로 최근 경형승용자동차 등에 대한 LPG 연료사용 허용으로 더욱 위험성이 증대된 지하주차공간에 대한 환기 등 시설기준의 개선, 그리고 LPG 자동차 확인 스티커 부착의무화 등 관리체계 개선방안을 제시하였다.

• 한국안전학회지
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• 제38권4호
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• pp.47-53
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• 2023

In the inspection of workplace hazards/risk factors by specialized institutions dedicated to safety management, inspection reports vary based on the inspectors, who lack the authority to enforce improvement of workplace hazards/risk factors. Thus, improvement and accident rates remain steady without decreasing. This study performed a regression analysis on the relationship between improvement and accident rates of categorized inspection items by classifying hazards/risk factors from inspection reports submitted by a specialized safety management institution in Chungbuk after inspecting 10 food and beverage manufacturers over the past three years. The hazards/risk factors were classified into five categories: mechanical, electrical, chemical, human, and environmental. The regression analysis revealed that the improvement rate of hazards/risk factors inspected by the specialized safety management institution influenced accident rates. To enhance improvement rates based on these findings, this study prioritized the correction of the five most frequently cited inspection items with the lowest improvement rates in each area. Based on these inspection items, this study suggested a checklist for use in workplace safety inspections of food manufacturers. This proposed checklist is expected to reduce accident rates in food manufacturing facilities. Currently, guidance and inspection of workplaces are mainly focused on accident rates rather than correcting hazards/risks. Thus, accident rates remain unchanged as workplace risks are inadequately improved according to the unique characteristics of each workplace. When conducting workplace guidance and inspection, policy measures and inspection methods are warranted to increase the improvement rate of hazards/risks.