• 한국기계가공학회지
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• 제8권4호
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• pp.69-75
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• 2009

Recently developed automotive components are getting lighter providing a higher fuel efficiency and performance. Following the current trend, this study proposes a structural optimization method for the lower control arm installed at the front side of a Vehicle. Lightweight design of lower control arm can be achieved through design and material technology. In this research, the shape of lower control arm was determined by applying the optimization technology and aluminum was selected as a steel-substitute material. Strength performance is the most important design requirement in the structural design of a control arm. This study considers the static strength in the optimization process. For the optimum design, the durability analysis is performed to predict its fatigue life. In this study, the kriging interpolation method is adopted to obtain the minimum weight satisfying the strength constraint. Optimum designs are obtained by the in-house program, EXCEL-Kriging. Also, based on the optimum model obtained for the static strength, the optimization of Index of Fatigue Durability is carried out to get th optimum fatigue performance.

• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.240-246
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• 2022

This study was conducted to develop a domestic product for a flow control valve for a hydrogen refueling station, and a domestic prototype was manufactured and the durability performance evaluation was conducted through comparison with an imported products. The stress generated by the internal pressure was checked and safety was confirmed using a commercial structural analysis program, ABAQUS, in accordance with the withstand pressure test standards. In addition, after identifying the weak areas the fatigue life was predicted through a commercial software, fe-safe. This fatigue analysis showed that the hydrogen gas repeated test criteria were satisfied.

• 한국기계가공학회지
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• 제9권6호
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• pp.16-20
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• 2010

This study proposes a structural design method for the upper control arm installed at the rear side of a SUV. The weight of control arm can be reduced by applying the design. In this research, the former includes optimization technology, and the latter the technologies for selecting aluminum as a steel-substitute material. Strength assessment is the most important design criterion in the structural design of a control arm. At the proto design stage of a new control arm, FE (finite element) analysis is often utilized to predict its strength. In this study, the kriging interpolation method is adopted to obtain the minimum weight satisfying the strength constraint and durability criteria. The optimum results determined from the in-house program are compared with those of ANSYS WORKBENCH. The durability assessment is obtained by a index of fatigue durability and trial & error method, MSC. Fatigue program.

• Annals of Occupational and Environmental Medicine
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• 제34권
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• pp.6.1-6.12
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• 2022

Background: To date, little is known about the effects of factors linked to work-related fatigue on vibration-exposed workers. Thus, the purpose of this study was (1) to assess the effects of vibration exposure time per week and work-related fatigue on workers and (2) to identify factors associated with work-related fatigue caused by long-term exposure to occupational vibration. Methods: This study used data collected from the 5th Korean Working Conditions Survey. A total of 34,820 non-vibration-exposed and 10,776 vibration-exposed employees were selected from the data. The χ² and multiple logistic regression were used to determine the effect of vibration exposure time per week and the effects of factors of work-related fatigue on workers. Results: The prevalence of work-related fatigue in vibration-exposed workers (30.5%) was higher than that of non-exposed workers (15.9%). The prevalence of work-related fatigue was higher for female and workers with depression, anxiety, and shift work, and those with authority to control their work pace had statistically significantly higher odds than those who did not. The employees who had the authority to control their order of work (odds ratio [OR]: 0.88; 95% confidence interval [CI]: 0.81-0.95) and method of work (OR: 0.90; 95% CI: 0.82-0.98) had statistically significantly lower odds than those who did not. The OR of workrelated fatigue symptoms was highest among employees whose vibration exposure time per week were 30.0%-40.0% (OR: 2.36; 95% CI: 1.96-2.83). Lower OR was observed as vibration exposure time per week decreased. Conclusions: The results of the present study suggest an association between occupational vibration and work-related fatigue and longer vibration exposure time per week, causing an increased prevalence of work-related fatigue symptoms. Measures to protect workers exposed to occupational vibration from work-related fatigue must be taken.

• 한국항공운항학회지
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• 제20권1호
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• pp.76-85
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• 2012

Air traffic controllers often experience fatigue and stress on the job due to work-related factors. Performance impairment resulting from fatigue and stress is an important concern for aviation safety. The goal of this research was to investigate fatigue and stress factors for air traffic controllers. The research involved an extensive literature review of fatigue and stress in the air traffic control environment and surveyed fatigue and job stress level of Korean air traffic controllers compared to other occupation groups. Results of survey showed that fatigue and stress levels of air traffic controllers were significantly higher than other occupation groups. Specially air traffic controllers reported that night work created high level of fatigue and perceived that physical environment and job demand induced high level of stress. In addition, implications for fatigue and stress management were discussed.

• 대한간호학회지
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• 제39권5호
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• pp.662-672
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• 2009

Purpose: This study was to examine the effects of self-foot reflexology on stress, fatigue and blood circulation in premenopausal middle-aged women. Methods: A quasi-experimental nonequivalent control group, pretest-posttest design was used. Participants were 59 premenopausal, middle-aged women in their 40s and 60s living in G city: 30 in the experiment group and 29 in the control group. Data were collected from May to August 2008. Self-foot reflexology was performed three times a week for 6 weeks for 40 min at each session. Results: The results showed that self-foot reflexology was effective in reducing perceived stress and fatigue and helped blood circulation in premenopausal middle-aged women. Conclusion: Self-foot reflexology may be an effective nursing intervention in reducing perceived stress and fatigue and in improving blood circulation.

• 한국안전학회지
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• 제18권1호
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• pp.38-43
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• 2003

In this paper, the low cycle fatigue(LCF) life tests were carried out under waveforms of asymmetric triangle($4{\times}10^{-3}$ and $4{\times}10^{-10}$ strain rate) and hold-time(1min and 10min) in strain control. In triangular waveform, the fatigue lives of fast-slow waveforms were decreased to about 63-73% and them of slow-fast waveforms were down to about 23-24% compared to them of fast-fast waveforms. The shapes of fracture surfaces were transgranular in fast-fast and fast-slow waveforms and intergranular in slow-fast ones. The fatigue lives of slow-fast waveforms were remarkedly shorter than them of hold-time waveforms even though cycle times of hold time waveforms were longer than them of slow-fast ones. The damage mechanisms of frature surfaces were mixed frature with both transgranular and intergranular, but intergranular fratures were r-type cavity in hold-time waveforms and w-type cavity in slow-fast ones.

• 성인간호학회지
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• 제23권6호
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• pp.615-623
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• 2011

Purpose: The purpose of this study was to identify the effects of aromatherapy on sleep disorders, satisfaction of sleep and fatigue in hemodialysis patients. Methods: The study design was a quasi-experimental study with nonequivalent control group pretest-posttest design. The subjects were assigned an experimental group (N=17) and a control group (N=17). The experimental group had inhaled lavender and sweet orange for 2 minutes three times a day for 7 days. Sleep disorders were measured using Sleep Measuring Instrument and satisfaction of sleep was gauged using Visual Analogue Scale. Fatigue was checked using Fatigue Measuring instrument. Collected data were analyzed by ${\chi}^2$-test, t-test, Fisher's exact test, and paired t-test using SPSS/WIN 17.0 program. Results: There are significant differences in the sleep disorders, satisfactions of sleep and fatigue between experimental group and control group. Conclusion: Aromatherapy reduced the sleep disorders and the fatigue and increased satisfactions of sleep in hemodialysis patients. Based on the results of this study, aromatherapy can be used at the any setting as a safe and effective independent nursing intervention to sleep disorders and fatigue in hemodialysis patients.

• The Journal of Korean Physical Therapy
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• 제26권5호
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• pp.280-289
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• 2014

Purpose: This study was conducted in order to determine the stimulation variables which should be considered when neuromuscular electrical stimulation (NMES) is applied for a muscle under the normal innervation to minimize muscle fatigue and increase force-generating ability. Methods: A total of 23 healthy men participated in the study and all subjects were randomly assigned to the 1:1 group, 1:3 group, 1:5 group, and control group with on-off ratio of NMES. The subjects performed a fatigue task, consisting of 10 times of isometric contraction sustained by NMES. NMES using Russian current stimulation was applied to muscle fatigue and divided into three sessions by pulse frequency (10 bps, 30 bps, 90 bps). The EMG was recorded using an MP 100 system from the quadriceps femoris muscle in four groups. Results: The differences of delta MdF and delta MF of between on-off ratio groups of 10 bps, 30 bps, and 90 bps pulse frequencies were very significant (p<0.05). According to the results of post hoc of 10, 90 bps, it was greater in the 1:1 group and the 1:3 group compared with the 1:5 group, and no fatigue was observed in the control group. In 30 bps, it was greater in the 1:1 group compared with 1:3, 1:5, and control group (p<.05). Conclusion: Among NMES variables to minimize muscle fatigue, the larger on-off ratio by pulse frequency showed the lower muscle fatigue. Therefore, on-off ratio needs to be great enough, and will be more efficient with the frequency 30 bps rather than of 10 bps and 90 bps.

• 임상간호연구
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• 제14권3호
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• pp.27-36
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• 2008

Purpose: This study was to investigate the effects of foot massage on fatigue and depression among patients undergoing chemotherapy with hematological malignancies. Method: The subjects were 60 patients hospitalized for undergoing chemotherapy from September 2007 to March 2008, and 30 of them were the experimental group and the other 30 were the control group. To the subjects in the experimental group, foot massage was provided for 30 minutes everyday before the chemotherapy at the same time for 4 days, and the effect was measured on Day 4 and 5 after chemotherapy. Fatigue was measured using the Brief Fatigue Inventory (BFI) developed by Mendoza et al. (1999), and depression was measured by psychiatric rating scale SCL-90-R developed by Derogatis (1977) and translated by Kim Gwang il et al. The data were analyzed through $x^2$-test, Fisher's exact test, unpaired t-test and repeated measures ANOVA using SPSS 12.0. Results: Fatigue and depression were significantly lower in the experimental group than in the control group. Even on Day 5, fatigue and depression were significantly lower in the experimental group than in the control after finish foot massage. Conclusion: The findings of the study demonstrated that foot massage would be an effective nursing intervention to reduce fatigue and depression in patients with hematological malignancies.