• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.69-76
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• 1997

The rotating bending fatigue tests were performed using the specimens taken from Cr-Mo-V steel, widely sued in thermal power plant turbines, at various temperatures such as room temperature, 300 .deg. C, 425 .deg. C and 550 .deg. C. The characteristics of fatigue crack propagation were examined and analyzed by using fracture mechanics parameter. The plastic replica method was also applied in order to measure the crack length on the basis of serial observation of fatigue crack propagation behavior on the defected specimen surface. The fatigue crack propagation behavior of Cr-Mo-V steel was investigated within the frame work of elastic-plastic fracture mechanics. The propagation law of fatigue crack is obtained uniquely by using the term .sigma. $^{n}$ sub a/where .sigma. $_{a}$ is the service stress, a is the crack length and n is a constant. The values of constant n are nearly equal to 2.48, 2.60 and 8.61 at room temperature, 300 .deg. C and 425 .deg. C.

• The Korean Journal of Emergency Medical Services
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• v.22 no.3
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• pp.149-162
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• 2018

Purpose: The purpose of the study was to investigate the differences in quality of sleep, job stress, fatigue, job satisfaction, and posttraumatic stress disorder (PTSD) according to the type of work in fire-fighting officers. Methods: This study used an online questionnaire. The participants were 322 fire-fighting officers. The data were collected from May 2 to 20, 2018. Data were analyzed using SPSS 22.0. Results: According to the work styles of fire fighting officers, job stress, job satisfaction, and PTSD showed significant differences. However, There were no differences in sleep quality and fatigue. There were significant differences in job stress, job satisfaction, and PTSD in those in roles of fire suppression and rescue emergency medical technicians and this result suggests a way to improve the quality of sleep, job stress, job satisfaction and fatigue for fire-fighting officers who suffer from PTSD. Conclusion: Based on the results of this study, mental health of fire-fighting officers will be improved through basic data for psychotherapy which can overcome the quality of sleep, job stress, fatigue, job satisfaction and PTSD according to the work style of fire-fighting officers.

• Korean Journal of Occupational Health Nursing
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• v.7 no.2
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• pp.177-185
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• 1998

The purposes of this study were to investigate the effects of farming in greenhouses with respect to subjective fatigue symptoms among farmers and the degree of symptoms. The study compared 176 green-house farmers with 216 open field farmers using a subjective fatigue symptoms rating scale developed by the Industrial Research Institute of Fatigue, Japanese Association for industrial Hygiene. 1. With respect to complaint rates of the subjective fatigue symptoms, the results indicated that greenhouse farmers have, in order of severity, high degrees of low back pain, difficulty in collecting thoughts, and apt to forget. 2. With respect to cumulative scores of fatigue symptoms, the results indicated that both groups of farmers exhibited a lack of attentiveness and a high degree of dullness and sleepiness(category I), body projection of fatigue(category II), and difficulty in concentration(category III). 3. With respect to general characteristics, it was found that the degrees of subjective fatigue symptoms were found to be higher among females, people with lower educational levels, and the elderly, regardless of the group. 4. With respect to work related factors, farmers with more years of experiences were found to have higher degrees of subjective fatigue symptoms, except for open field farmers with less than nine years experience. Both groups of farmers were found to have high degrees of subjective fatigue symptoms when working less than eight hours a day and less than six months a year. 5. With respect to health habits, for people who get less than eight hours of sleep per day exhibited higher fatigue scores than people who get more than eight hours. People who do not smoke and drink also exhibited higher fatigue scores than people who smoke and drink. 6. The results of multiple regression showed that the risk factors related to the subjective fatigue symptoms of farmers in the greenhouse group were ages, levels of education, sex and for the comparison group, were sex. years of farming, and hours of sleep. The R-square were 12.5% in the greenhouse group and 12.1% in the comparison son group. The differences between the greenhouse and open field farmers in the degrees of fatigue symptoms were found not to be statistically significant even if the working conditions of the greenhouse farmers were poor. This may be attributed to non-work related factors, i.e., social, economical, and psychological factors among greenhouse farmers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4315-4328
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• 2019

The present study investigated the effects of work satisfaction on quality of life for 119 paramedics, the Korean equivalent of 911 paramedics. Data collection began in July 2017 and lasted for six months. Data was collected from 410 119 paramedics of the J province and the G metropolitan area who consented to study participation. The results showed that the higher the job satisfaction of the participants, the higher the quality of life (r = 0.508, p = 0.008). The factors affecting the quality of life were leisure activity, subjective health, and job satisfaction. For 119 paramedics to improve their quality of life, they need to relieve work stress and fatigue through leisure activities, and recover and maintain their health through sufficient rest. Moreover, returning to work in a healthy state likely leads to increased job satisfaction, and the quality of life will increase accordingly. Therefore, 119 paramedics should be permitted to have plenty of leisure time outside their work hours and should be able to maintain health through periodic health checks.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.678-683
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• 2016

The study aim was to investigate a comparison of muscle activity fatigue between maximal and submaximal strength gains during the bench press in men. It was hypothesized that maximal voluntary contraction (%MVC) would similar gains between maximal and submaximal strength gains during the bench press, but median frequency (MDF) would increase in maximal compared with submaximal exercise. Employing a randomized, counterbalanced crossover design, 12 men were asked to perform maximal repetitions and submaximal repetitions (concentric: 1-s, eccentric: 1-s, 2-s/repetition) to failure with a load of 85% of 1RM for the bench press, with a 3-minute recovery between the sets. Each subject was tested for the number of repetitions and sets, total work in bench press. Surface electromyography (EMG) was recorded from the pectoralis major, deltoid anterior, and triceps brachii for %MVC and MDF. Total work was significantly higher in the submaximal repetition exercise than that the maximal repetition exercise (p<.05). Muscle fatigue of pectoralis major, deltoid anterior and triceps brachii were significantly smaller in the submaximnal repetition exercise than that the maximal repetition exercise (p<.05, respectively). However, muscle activity of pectoralis major, deltoid anterior, and triceps brachii were not significantly different between exercises. Our study showed that a smaller muscle fatigue in submaximal repetitions, despite higher in total work and a similar in muscle activity were observed. These results suggest that submaximal repetitions during the bench press would be enhanced intensity and/or volume compared with maximal repetitions exercise.

• Journal of the Ergonomics Society of Korea
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• v.32 no.1
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• pp.125-137
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• 2013

Objective: The aim of this study was to comprehend major concepts and flows that penetrate international guides or standards for developing a quantitative possibility measure of human errors that can be committed or omitted in nuclear power plants. Background: For a few past decades, lots of researchers have studied the effect of stress and/or fatigue which can result in human errors. Thus, this study was carried out on the assumption that much of them were summarized as an international guidelines or manuals, if any, for human error prevention. Method: A literal survey was conducted with materials and documentation published by international organizations related with safety and standardization, such as ISO, OSHA, NIOSH, NASA, and so on with special reference to human error prevention through management of work stress and fatigue as major Performance Shaping Factors. Results: International guides or management manuals on stress or fatigue management for human error prevention hardly were found, and most researches seemed to concentrate on one of them individually. Conclusion: There was few vestige of research that studied both concurrently. However, it was verified that not a few researches have been tried to develop quantitative measures to estimate probability or job characteristics for human error prevention and/or performance downgrading. Application: The results of this study would help to develop a causal model of human errors due to work stress and fatigue that can result in unexpected accidents in nuclear power plant.

• Korean Journal of Community Nutrition
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• v.1 no.2
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• pp.250-259
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• 1996

The school foodservice(FS) dietitians of conventional, co-management and central kitchen systems were compared for their levels of fatigue degrees in order to examine their work specification but no to diminish their educational roles. One hundred and thirtheen primary schools in Taejon and Chungcheongnam-Do participated in the survey, of which foodservice were consisted of 99 conventional types, 7 comanagement types and central kitchen types. Information was collected about the various working hours dietary behavior and fatigue symptoms of the dietitians. The results of this study were as follows : Among 3 school foodservice types, dietitians spent 8 hours and 16 minutes daily for their for their work on the average. However, the central kitchen type dietitans in cities spent 3 hours more compared to the others. The data from the dietitians' work schedule sheets showed that the 5 parts of dietitian's duties set in the school foodservice laws were not well performed. In the central kitchen type they spent more time for food production whereas in the conventional they spent more time for menu formation and hygiene control. It was found that fatigue levels of school foodservice dietitians were chronic with no difference among foodservice systems or among school locations. Our results indicated that nutrition education in primary schools was almost neglected. It is suggested that the school foodservice should meet all the objectives of school-lunch program even though they saved dietitians' work load more or less. The importance of students to improve their dietary habits could never be overlooked. (Korean J Community Nutrition 1(2) : 250-259, 1996)

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.551-556
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• 2012

Fatigue is known to detrimentally affect a person's performance. Also, fatigue may reduce effectiveness and efficiency of marine officers and crew members. The purpose of this research is to understand on the status of the marine officers' fatigue. In this study, we carried out the questionnaire survey which is related to the marine officers' fatigue factors such as work, sleep and rest hour or period, sleepiness, casual factor, fatigue symptom, etc. The questionnaire contained 25 questions and it was distributed among 1,033 marine officers(deck officers 607 and engineers 426). The results of this survey show that marine officers' fatigue is a casual factor in marine accidents such as collisions, groundings and there was a fatigue difference between deck officers and engineers.

• Steel and Composite Structures
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• v.18 no.4
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• pp.925-946
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• 2015

This paper presents a new cost-effective hybrid GFRP-Concrete deck system that the GFRP panel serves as both tensile reinforcement and stay-in-place form. In order to understand the fatigue behavior of such hybrid deck, fatigue test on a full-scale specimen under sagging moment was conducted, and a series of static tests were also carried out after certain repeated loading cycles. The fatigue test results indicated that such hybrid deck has a good fatigue performance even after 3.1 million repeated loading cycles. A three-dimensional finite element model of the hybrid deck was established based on experimental work. The results from finite element analyses are in good agreement with those from the tests. In addition, flexural fatigue analysis considering the reduction in flexural stiffness and modulus under cyclic loading was carried out. The predicted flexural strength agreed well with the analytical strength from finite element simulation, and the calculated fatigue failure cycle was consistent with the result based on related S-N curve and finite element analyses. However, the flexural fatigue analytical results tended to be conservative compared to the tested results in safety side. The presented overall investigation may provide reference for the design and construction of such hybrid deck system.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.362-367
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• 2008

In the present work, we address electric fatigue behavior in bending piezoelectric actuators using an acoustic emission technique. Electric cyclic fatigue tests have been performed up to ten million cycles on the fabricated specimens. To confirm the fatigue damage onset and its pathway, the source location and distributions of the AE behavior in terms of count rate are analyzed over the fatigue range. It is concluded that electric cyclic loading leads to fatigue damages such as transgranular damages and intergranular cracking in the surface of the PZT ceramic layer, and intergranular cracking even develops into the PZT inner layer, thereby degrading the displacement performance. The electric-induced fatigue behavior seems to show not a continuous process but a step-by-step process because of the brittleness of PZT ceramic. Nevertheless, this fatigue damage and cracking do not cause the final failure of the bending piezoelectric actuator loaded up to 107 cycles. Investigations of the AE behavior and the linear AE source location reveal that the onset time of the fatigue damage varies considerably depending on the existence of a glass-epoxy protecting layer.