• 응용통계연구
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• 제37권2호
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• pp.225-237
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• 2024

경쟁위험자료에서 일부 공변량들이 연구대상들의 일부분에 대해 관측되지 않을 수 있다. 그런 경우 결측된 공변량 값을 가진 연구대상들을 분석에서 제외하는 것은 편향된 추정치와 효율성 손실이 발생할 수 있다. 본 논문에서는 누락된 공변량을 가진 원인별 비례위험모형의 회귀모수 추정을 위해 다중대체 방법과 증대된 역 확률 가중 방법을 연구하였다. 모의실험을 통해 다중대체 방법과 증대된 역 확률 가중 방법에 의해 구해진 추정량의 성능을 평가한 결과, 이 방법들이 잘 수행됨을 확인하였다. 미국 국립암연구소의 전립선, 폐, 대장, 난소 암 선별 시험 연구에서 제공하는 종양 크기의 값이 누락된 유방암 자료에 대해 암 사망 위험률과 다른 원인 사망 위험률에 유의한 영향을 미치는 요인을 파악하기 위해 다중대체 방법과 증대된 역 확률 가중 방법을 적용하였다. 다중대체 방법과 증대된 역 확률 가중 방법에 의해 원인별 비례위험모형을 적합한 결과, 인종, 기혼여부, 병기, 분화도, 종양의 크기는 유방암 사망 위험률에 유의한 영향을 미치는 요인들이였으며, 병기가 유방암 사망 위험률을 높이는데 가장 큰 영향을 미치는 요인임을 확인하였다. 진단시 연령과 종양의 크기는 다른 원인 사망 위험률을 높이는데 유의한 영향을 미치는 요인이였다.

• Smart Structures and Systems
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• 제24권6호
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• pp.693-707
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• 2019

This paper proposes an integrated safety assessment method that can take multiple sources data into consideration based on a data fusion approach. Data cleaning using the Kalman filter method (KF) was conducted first for monitoring data from each sensor. The inclination data from the four tilt sensors of the same monitoring section have been associated to synchronize in time. Secondly, the finite element method (FEM) model was established to physically correlate the external forces with various structural responses of the shield tunnel, including the measured inclination. Response surface method (RSM) was adopted to express the relationship between external forces and the structural responses. Then, the external forces were updated based on the in situ monitoring data from tilt sensors using the extended Kalman filter method (EKF). Finally, mechanics parameters of the tunnel lining were estimated based on the updated data to make an integrated safety assessment. An application example of the proposed method was presented for an urban tunnel during a nearby deep excavation with multiple source monitoring plans. The change of tunnel convergence, bolt stress and segment internal forces can also be calculated based on the real time deformation monitoring of the shield tunnel. The proposed method was verified by predicting the data using the other three sensors in the same section. The correlation among different monitoring data has been discussed before the conclusion was drawn.

• 한국직업건강간호학회지
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• 제29권1호
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• pp.58-68
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• 2020

Purpose: Workers with chronic health problems find it difficult to maintain their work because of socioeconomic difficulties. The purpose of this study was to evaluate the relationships between physical, ergonomic, and mental health hazards in the workplace and chronic health problems of Korean workers. Methods: A total of 28,807 wage workers participated in the study and were selected using the Fifth Korean Working Conditions Survey (2017). Multiple logistic regression analysis was used to determine the associations between physical, ergonomic, and mental health hazards and chronic health problems. Results: Of the participants, 1,220 (4.23%) had chronic health problems. Even after adjusting the general characteristics, vibration, noise, high temperature, low temperature, dust, chemical and cigarette smoke, fatigue and painful posture, dragging or pushing or moving of heavy objects, repetitive hand or arm movements, working with a computer or smartphone, use of internet or e-mail, and anxiety situations increased the risk of chronic health problems. Conclusion: The study reaffirms that exposure of physical, ergonomic, and mental health hazards in the workplace significantly increases the risk of chronic health problems.

• Safety and Health at Work
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• 제2권3호
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• pp.260-272
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• 2011

Objectives: The promotion of health and safety (H&S) awareness among hospital staff can be applied through various methods. The aim of this study was to assess the risk level of physical hazards in the hospital sector by combining workers' perception, experts' evaluation and objective measurements. Methods: A cross-sectional study was designed using multiple triangulation. Hospital staff (n = 447) filled in an H&S questionnaire in a general hospital in Athens and an oncology one in Thessaloniki. Experts observed and filled in a checklist on H&S in the various departments of the two hospitals. Lighting, noise and microclimate measurements were performed. Results: The staff's perception of risk was higher than that of the experts in many cases. The measured risk levels were low to medium. In cases of high-risk noise and lighting, staff and experts agreed. Staff's perception of risk was influenced by hospital's department, hospital's service, years of working experience and level of education. Therefore, these factors should be taken into account in future studies aimed at increasing the participation of hospital workers. Conclusion: This study confirmed the usefulness of staff participation in the risk assessment process, despite the tendency for staff to overestimate the risk level of physical hazards. The combination of combining staff perception, experts' evaluation and objective measures in the risk assessment process increases the efficiency of risk management in the hospital environment and the enforcement of relevant legislation.

• Communications for Statistical Applications and Methods
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• 제24권2호
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• pp.115-127
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• 2017

This paper proposes a Bayesian test for the equivalence of survival functions in multiple groups. Proposed Bayesian test use the model of Cox's regression with time-varying coefficients. B-spline expansions are used for the time-varying coefficients, and the proposed test use only the partial likelihood, which provides easier computations. Various simulations of the proposed test and typical tests such as log-rank and Fleming and Harrington tests were conducted. This result shows that the proposed test is consistent as data size increase. Specifically, the power of the proposed test is high despite the existence of crossing hazards. The proposed test is based on a Bayesian approach, which is more flexible when used in multiple tests. The proposed test can therefore perform various tests simultaneously. Real data analysis of Larynx Cancer Data was conducted to assess applicability.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.40-41
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• 2021

The construction industry has the highest occupational accidents/injuries among all industries. Korean government installed surveillance camera systems at construction sites to reduce occupational accident rates. Construction safety managers are monitoring potential hazards at the sites through surveillance system; however, the human capability of monitoring surveillance system with their own eyes has critical issues. Therefore, this study proposed to build a deep learning-based safety monitoring system that can obtain information on the recognition, location, identification of workers and heavy equipment in the construction sites by applying multiple-object tracking with instance segmentation. To evaluate the system's performance, we utilized the MS COCO and MOT challenge metrics. These results present that it is optimal for efficiently automating monitoring surveillance system task at construction sites.

• 한국산업보건학회지
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• 제22권2호
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• pp.156-163
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• 2012

Objectives: The aim of the present study was undertaken to investigate the association between communication for chemical hazard information and characteristics of occupational safety and health managers. Subjects and Methods: We surveyed 78 occupational safety and health managers(64 male and 14 female) in 78 chemical manufacturing plants. Data were obtained using a self-reported questionnaire about size and type of company, products, communication system for chemicals and work-related characteristics of occupational safety and health managers. All analyses in this study were performed using SPSS program 12.0. Results: 64.1% of the study participants were occupational health managers aged 39.3 years on average and were graduated from college and university around 90%. 30.0% and of them were majoring in chemistry (engineering chemistry), 18.0% occupational health, 16% nursing and 30.0% others. Occupational safety managers were aged 39.4 years on average, 42.9% of them were majoring in chemistry (engineering chemistry), 21.4% environmental engineering, 10.7% occupational safety and 25% others. 86% of occupational health managers and 71.4% of occupational safety managers were classified as office job. Over 94% of the hazards information for chemicals were delivered by occupational safety and health managers, but about 28.2% workers preferred outside experts who have a profound knowledge about occupational safety and health and understandable. Occupational safety and health managers and workers had difficulties in understanding toxicological information, hazards identification, stability/reactivity, composition/information on ingredients, physical/chemical properties and ecological information. On multiple logistic regression analysis for the 16 heading of material safety data sheet, content of material safety data sheet was significantly associated with education level (odds ratio=0.286, 95% confidence interval=0.105-0.780). The hazard identification (odds ratio=3.947, 95% confidence interval=1.092-14.271) and toxicological information (odds ratio=0.841, 95% confidence interval=0.705-0.998) were significantly associated with type of occupation. Conclusions: This finding implies that the education level, type of occupation and speciality of occupational safety and health managers may affects hazards information delivery.

• 한국안전학회지
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• 제34권1호
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• pp.34-39
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• 2019

Flash point is the important indicator to determine fire and explosion hazards of liquid solutions. In this study, flash points of n-propanol+n-hexanol and n-butanol+n-hexanol systems were obtained by Seta flash tester. The methods based on UNIFAC equation and multiple regression analysis were used to calculate flash point. The calculated flash point was compared with the experimental flash point. Absolute average errors of flash points calculated by UNIFAC equation are $2.9^{\circ}C$ and $0.6^{\circ}C$ for n-propanol+n-hexanol and n-butanol+n-hexanol, respectively. Absolute average errors of flash points calculated by multiple regression analysis are $0.5^{\circ}C$ and $0.2^{\circ}C$ for n-propanol+ n-hexanol and n-butanol+n-hexanol, respectively. As can be seen from AAE, the values calculated by multiple regression analysis are noticed to be better than the values by the method based on UNIFAC eauation.

• 한국안전학회지
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• 제27권3호
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• pp.131-140
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• 2012

Though there might exist not a few differences between cyclic works and atypical works, many researchers have applied the same assessment techniques that used for repetitive works, which may result introduce bias in their conclusions. This research aimed to verify whether there exist non-negligible work characteristics and/or dissimilarity among works with different work nature and whether one of the most prevalent assessment techniques for assessing ergonomic hazards of musculoskeletal disorders, REBA, can be applied to atypical works. For a general hospital, an automobile repair shop, and two auto-part assembly plants which manufactures quite different parts, a questionnaire survey and field investigation and ergonomic assessment were carried out and analyzed statistically with reference to the 3rd Quantification technique. The results showed that there exist remarkable difference between physical factors in cyclic works and atypical non-cyclic works. As for repetitive work, body posture was significant factors affecting on musculoskeletal disorders while atypical works seemed to have none which implied that the necessity of taking psychosocial factors into account for assessment of hazards. Complain rate in repetitive works was highest shoulder, back, and neck or wrist in sequence. However, there existed no consistent trend in complain rate in atypical works. And, though weight of manufacturing objects was a common factor that can partly explain musculoskeletal complain, time duration was significant in atypical work whereas repeatability and body posture were significant in repetitive works. As being the results, to summarize, it could be said that application of conventional ergonomic assessment techniques regardless of repetitiveness would be fruitless, and that the necessity of a unique methodology focused on atypical non-cyclic works should not be neglected.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1959-1962
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• 2009

In this paper, we derive the hazard which is a criterion of safety assurance by PHA for the ATP equipped in Korea Tilting Train. The ATP onboard equipment in Korea Tilting Train was introduced as ETCS Level l(which is ETCS specification). Also, the ATP trackside equipment was introduced as a ETCS SRS(System Requirement Specification) 2.2.2 and it has a target for commercial operation in 2009 late. In IEC 62278(EN50126), it recommend of PHA to derive a hazard of target system in concept establishment step and estimate if it can control as a tolerable level and then derive safety case to control the hazard by lifecycle. Therefore, we indicate the hazard using criterion of safety assurance by PHA using FRS (Functional Requirement Specification) 5.0. which is a upper criterion than SRS. The hazard of ATP onboard equipment derived in Korea Tilting Train will be able to use as ATP functional hazards of unified onboard equipment in G7 which is a multiple unit and preliminary hazards of ATP onboard equipment in NEL drived by Korail.