• 한국기계연구소 소보
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• s.13
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• pp.3-13
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• 1984

Fatigue failure of axle housing could cause many injuries and much financial loss. This challenges the engineer to improve design decisions involving fatigue. Endurance evaluation of axle housing is great interest to auto-mobile manufacturers for the sake of safety and reliability. Axle housing is subjected to gross vehicle weight(G.V.W)as mean load and alternating load. Theoretical design diagram involving mean and alternating stresses is used for the evaluation of axle housing fatigue endurance with the equivalent stress of fatigue critical area on the axle housing. Four point bending fatigue tests on axle housing with constant amplitude loading at approximately R=0 were performed with 50 ton servohydraulic strucural fatigue testing machine developed at KIMM. Specimens were made with the same material STKM 13B as the axle housing and tested to obtain S_N data. Five specimens of STKM 13B were tested at 253.61 MPa and weibull distribution was obtained at the same stress level. Material data and structural data were compares and fatigue stress property factor and fatigue life property factor were obtained.

• Korean Journal of Adult Nursing
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• v.20 no.4
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• pp.513-525
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• 2008

Purpose: The present study was intended to measure fatigue symptoms according to the quality of sleep among nurses working for an university hospital and to reveal its related factors. Methods: The self-administered questionnaires were given to 397 nurses employed in an university hospital located in Daejeon City during the period from June 1st to July 31st, 2007. Results: The group with higher quality of sleep accounted for 78.1% of all the subjects and the one with lower quality, 21.9%. According to qualities of sleep, the fatigue symptom was determined to be significantly higher in the group with lower quality of sleep than its counterpart. On adjustment for quality of sleep, the level of fatigue symptom was significantly higher in the groups, than in each respective counterparts, who don't take regular exercises, who have few leisure time, who have lower level of subjective health status, who range ${\geq}$ 1 and < 10 years in job careers, who work in shifts, who reported that it is hard to get physical burden of work, who are satisfied with the job, who find themselves unfit to the job, who are considering quitting the job, who have higher job demand, who have lower job control, who have higher level of supervisor support, who have type A behavior pattern. Conclusion: The study results may explain that the fatigue symptom of nurses is highly associated with the quality of sleep independently of other variables and also with job-related characteristics independently of the sleep quality. In conclusion, to reduce the fatigue symptom of nurses, strategic efforts should be directed for programs to improve the quality of sleep and a proper job analysis.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.247-259
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• 2017

This paper presents a fatigue assessment model that was developed for corroded reinforced concrete (RC) beams strengthened using prestressed carbon fiber-reinforced polymer (CFRP) sheets. The proposed model considers the fatigue properties of the constituent materials as well as the section equilibrium. The model provides a rational approach that can be used to explicitly assess the failure mode, fatigue life, fatigue strength, stiffness, and post-fatigue ultimate capacity of corroded beams strengthened with prestressed CFRP. A parametric analysis demonstrated that the controlling factor for the fatigue behavior of the beams is the fatigue behavior of the corroded steel bars. Strengthening with one layer of non-prestressed CFRP sheets restored the fatigue behavior of beams with rebar at a low corrosion degree to the level of the uncorroded beams, while strengthening with 20- and 30%-prestressed CFRP sheets restored the fatigue behavior of the beams with medium and high corrosion degrees, respectively, to the values of the uncorroded beams. Under cyclic fatigue loading, the factors for the strengthening design of corroded RC beams fall in the order of stiffness, fatigue life, fatigue strength, and ultimate capacity.

• Physical Therapy Korea
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• v.26 no.2
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• pp.16-23
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• 2019

Background: High-heeled shoes can change spinal alignment and feet movement, which leads to muscle fatigue and discomfort in lumbopelvic region, legs, and feet while walking. Objects: This study aimed to identify the effects of different shoe heel heights on the walking velocity and electromyographic (EMG) activities of the lower leg muscles during short- and long-distance walking in young females. Methods: Fifteen young females were recruited in this study. The experiments were performed with the following two different shoe heel heights: 0 cm and 7 cm. All participants underwent an electromyographic procedure to measure the activities and fatigue levels of the tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and hamstring muscles with each heel height during both short- and long-distance walking. The walking velocities were measured using the short-distance (10-m walk) and long-distance (6-min walk) walking tests. Results: Significant interaction effects were found between heel height and walking distance conditions for the EMG activities and fatigue levels of TA and MG muscles, and walking velocity (p<.05). The walking velocity and activities of the TA, MG, and RF muscles appeared to be significantly different between the 0 cm and 7 cm heel heights during both short- and long-distance walking (p<.05). Significant difference in the fatigue level of the MG muscle were found between the 0 cm and 7 cm heel heights during long-distance walking. In addition, walking velocity and the fatigue level of the MG muscle at the 7 cm heel height revealed significant differences in the comparison of short- and long-distance walking (p<.05). Conclusion: These findings indicate that higher shoe heel height leads to a decrease in the walking velocity and an increase in the activity and fatigue level of the lower leg muscles, particularly during long-distance walking.

• Journal of Korean Clinical Health Science
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• v.6 no.2
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• pp.1156-1170
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• 2018

Purpose. This study was conducted to analyze fatigue and subjective oral health status in the employees in educational institutions and provide basic data for the development of a program for the promotion of oral health. Methods. As for the subjects, this study conducted a survey with 468 educational personnel in elementary, middle, and high schools in the Daegu-Gyeongbuk area from March through June 2016 and utilized 407 copies finally. As for the items on the survey, this study conducted an investigation on their general characteristics, fatigue, and subjective oral health status(halitosis, xerostomia, temporomandibular disorder) with the self-administered method. With the data collected, this study conducted frequency analysis, t-test, ANOVA, and multiple regression analysis, using SPSS 20.0 statistical program, and the statistical significance level was .05. Results. As a result of this study, it turned out that by sex, fatigue was higher in women(4.59 points); by the place of work, those in 'elementary school' had higher fatigue(4.59 points); and by health condition and oral health status, most of them responded that they were 'not healthy'(4.81 and 4.84 points, respectively) and there was a statistically significant difference (p<.05). As for the correlation between fatigue and subjective oral health status, there were positive(+) impacts on halitosis(=.248, p<.001), xerostomia(=.097, p<.05), and temporomandibular disorder(=.148, p<.01), so it turned out that there was a correlation between fatigue and subjective oral health status. Conclusion. Based on the result of an analysis of the impacts of the fatigue level on subjective oral health status, it is judged that it would be necessary to continue to build up a program that can promote the oral health status of the educational personnel. In addition, it is necessary to conduct studies continuously for the development and application of a program for the change in lifestyle and behavior that can lower their fatigue.

• Women's Health Nursing
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• v.24 no.1
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• pp.49-57
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• 2018

Purpose: Postpartum fatigue can impact maternal well-being and has been associated with levels of perceived self-care. This study aimed to examine the relationship among fatigue, depressive mood, self-care agency, and self-care action among postpartum women in Bangladesh. Methods: A descriptive cross sectional survey was done with 124 first-time mothers from two tertiary hospitals in Dhaka, Bangladesh. The Modified Fatigue Symptoms checklist, Denyes' Self Care Instrument, the Edinburgh Postnatal Depression Scale, and items on sociodemographic and delivery-related characteristics, were used in Bengali via translation and back-translation process. Results: High fatigue levels were found in 18.5% (n=23) and 73.4% had possible depression (n=91). There was a significant negative relationship between fatigue and self-care agency (r=-.31, p<.001), and self-care action (r=-.21, p<.05). Fatigue differed by level of self-care agency (t=4.06, p<.001), self-care action (t=2.36, p=.023), newborn's APGAR score (t=-2.93, p=.004), parental preparation class participation (F=15.53, p<.001), and postpartum depressive mood (t=-4.64, p<.001). Conclusion: Findings suggest that high level of self-care efficacy and behaviors can contribute to fatigue management, and highlight the need for practical interventions to better prepare mothers for postpartum self-care, which may, in turn, alleviate postpartum fatigue.

• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.198-198
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• 1991

Not only difference of fatigue crack growth and propagation behavior resulted from the grain size, the hardness ratio and volume fraction in M.E.F. dual phase steel composed of martensite in hard phase and ferrite in soft phase, but also the effects of the plastic constraint were investigated by fracture mechanics and microstructural method. The main results obtained are as follows: 1) The fatigue endurance of M.E.F. steel increases with decreasing the grain size, increasing the ratio of hardness and volume fraction. 2) The initiation of slip and crack occures faster as the stress level goes higher. These phenomena result from the plastic constraint effect of the second phase. 3) The crack propagation rate in the constant stress level is faster as the grain size gets larger, the ratio of hardness lower and volume fraction smaller.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.683-690
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• 2002

Static and fatigue tests were performed to evaluate fatigue strength in scallop at field bolted joints of longitudinal rib and deck plate in orthotropic steel decks. Numerical parametric studies using finite elemtn analysis were also conducted to show the influence of parameters such as length and radius of scallop, and thickness of deckplate on the stress concentration at the scallop. In the low stress level, fatigue tests yielded cracks at the scallop while in the high stress level, catastrophic failure of longitudinal rib occurred following the failure of handhole cover plate. Fatigue strength was compared with JSSC specification and the predicted S-N curves using Shigley and Juvinall methods, and a satisfactory result was obtatined.

• Journal of the Ergonomics Society of Korea
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• v.21 no.2
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• pp.25-33
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• 2002

The purpose of study is to investigate the relationship between the trunk muscle fatigue and recovery time during repetitive extension by using a surface electromyogram(EMG). Ten healthy subjects particioated in a simulated lifting task with five levels of recovery time and three levels of sub-maximal contraction. EMG signals of the L1(Lumbar 1st Vertebrae) and L3(Lumbar 3rd Vertebrae) level of the erector spinae muscle were recorded. and analyzed in terms of MPF(mean power frequency) parameter to quantify the level of muscle fatigue. It was found that MPF significantly (p<0.05) decreased during repetitive extension task at 50% and 75% sub-maximal contractions. Then it took minutes for the trunk muscle to recover from fatigue during 50% sub-maximal contraction. and it took five minutes during 75% sub-maximal contraction. and it took five minutes during 75% sub-maximal contraction. The recovery time estimated by the maximum force needs to be re-evaluated for the trunk muscle to fully recover from fatigue. In conclusion. the work/rest cycle needs to be studied based upon the information of muscle fatigue in order to prevent workers from musculoskeletal injuries during repetitive lifting task.

• Journal of Digital Contents Society
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• v.19 no.3
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• pp.489-496
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• 2018

This article is to examine the influence of occupational stress, socio-psychological factors and quality of sleep on fatigue symptoms from firefighters in fire service. The correlation coefficients were obtained by a tool of Pearson analysis, and covariance structure analysis was performed on the factors affecting the level of fatigue symptoms. This result suggests that the level of firefighters' fatigue symptoms in fire service. has a causal effect with occupational stress, socio-psychological factors and quality of sleep. Therefore, it is necessary to improve the work environment and to increase organizational support to deal with firefighters' fatigue in fire service.