• Journal of Broadcast Engineering
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• v.15 no.5
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• pp.607-616
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• 2010

The methods developed to measure visual fatigue so far are quite few and lack of validity, and more importantly, they do not figure out the complex properties of the visual fatigue. The purpose of the research was to analyze the factors comprising the visual fatigue and to develop the method to measure it validly. The results are summarized as follows. First, we found that the 3D visual fatigue was comprised of four independent factors (visual stress, eye pain, body pain and image blurring factors). Second, we developed 29 items that measure four factors of 3D visual fatigue. Finally, the watching duration and binocular disparities affected the visual fatigue as had been expected. These results imply that the developed method does measure the three dimensional fatigue validly.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.589-594
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• 2022

In an acceleration of 'untact' society during the COVID-19 pandemic, video conferencing platforms have been provided to connect the isolated and to overcome the limit of having interpersonal relationships. While these services brought a great deal of benefits, they also increased the number of people who suffer from additional fatigue from video conferencing. This study, thus, aimed to identify the factors of using video conferencing services and further to examine the relationship between the factors and the users' overall fatigue. Through focus-group interviews and survey, four main factors of fatigue (restriction from untact communication, difficulty of use, background set-ups, discomfort from excessive attention) were identified. This study also found the positive relationships of restriction from untact communication and background set-ups on the users' overall fatigue. The results does not only provide implication on defining new fatigue factors from young generations but also help practitioners and service providers to improve the deficits of services that the real users currently experience.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.80-85
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• 2012

Fatigue cracks in structural components are the most common cause of structural failure when exposed to fatigue loading. In this respect, fatigue crack detection and structural health assessment are very important. Currently, various smart materials are used for detecting fatigue crack and measurement of SIFs(Stress Intensity Factors). So, this paper presented a measurement of SIFs using MFC(Micro Fiber Composite) sensor which is the one of the smart material. MFC sensor is more flexible, durable and reliable than other smart materials. The SIFs of Mode I(K I) as well as Mode II(K II) based on the piezoelectric constitutive law and fracture mechanics are calculated. In this study, the SIF values measured by MFC sensors are compared with the theoretical results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.201-207
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• 2010

Recently, about 600 cases of marine accidents occur annually in Korea. According to many studies and analyses on occurrence of marine accidents, 70~80% of marine accidents were caused by human factors. Among the human factors, navigation officers' fatigue is very important factor. Although navigation officers' fatigue serves as an important role in marine accidents, there is no method to exactly examine the degree of officers' fatigue. Accordingly, this study analyzed human factors according to types of marine accidents and extracted important five factors affecting navigation officers' fatigue through the questionnaire survey by means of literatures and 5-point scale. In addition, evaluation factors of marine accident risks caused by fatigue factors were divided and structured by using ISM. Lastly, it found out the importance of each fatigue factor drawn by AHP and decided marine accidents that were most highly caused by navigation officers' fatigue in order. At the result, weights were high as sleep time 0.385, stress 0.302, health condition 0.139, rest time 0.099, alcohol and drug 0.074 in fatigue factors, and death and injury 0.328, collision 0.308, grounding 0.195, sinking 0.094, fire accident 0.075 in evaluation factors of marine accident risks. Therefore, the control plan to lower marine accident risks should be prepared on the basis of high weight factors.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.8 no.1
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• pp.5-14
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• 2002

Objectives : In order to investigate industrial fatigue due to visual display terminal (VDT) work of post office. Methods : The questionnaire survey for subjective symptoms of fatigue was carried out on 39 post office clerks who had been engaged in VDT work for various length of work hours. The questionnaire comprised three groups of 10 items each, representing dullness and sleepiness, difficulty in concentration and bodily projection of fatigue. Results : The scores of dullness and sleepiness was 16.62, scores of concentration difficulty was 16.35, those of bodily fatigue was 16.23, and total scores was 49.21. Fatigue scores was significantly associated with age and work duration, VDT of work hours, ventilation, illumination, nosie. Conclusions : Data from this study support a statistically significant association between age and scores of dullness, scores of concentration difficulty, between work duration and scores of dullness, scores of bodily fatigue, between VDT of work hours and scores of bodily fatigue.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.10
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• pp.113-119
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• 1998

Ship structures and aircraft structures are consisted of thin sheet alloy, so it is very important to understand the characteristics of fatigue crack propagation of that material and to establish the data base. The data for fatigue crack propagation behavior scatter very much even under identical experimental conditions with constant loading. The behavior of fatigue crack propagation under regular and irregular cyclic loadings is known to be highly affected by complicated factors such as plastic zone developed at the vicinity of crack tip and reduction of cross sectional area. In this paper, the controlled stress amplitude and overload fatigue crack propagation tests have been conducted to investigate the effect of varying factors such as plastic zone size near the crack tip and area reduction factor (AF) on the fatigue crack propagation behavior A better simulation of fatigue crack propagation behavior is found to be obtainable by using Wheeler and Willenborg models with AF effect.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.20-28
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• 1997

The fatigue crack propagation properties and fatigue life of two kinds of Al body panel for automobile were examined experimentally by using the plate specimen and the single spot welding specimen. The fatigue limit of spot welding specimens was lower than that of a plate specimen. The fatigue limit was similar in two kinds of spot welding specimen. The shape and size of crack propagation were observed and measured on beach mark of fracture surface. The crack propagation of surface crack specimen showed almost same tendency to that of a thick plate as almost semi-elliptical. In spot welding specimen, the fatigue crack occurred in inside surface of nugget area was almost semi-elliptical. The crack growth rate can be explained using equation of stress intensity factors.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.16 no.2
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• pp.190-199
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• 2009

Purpose: This study was conducted to identify the factors contributing to sleep disorders in patients on hemodialysis. Methods: A descriptive correlational study design was used. The participants were 135 patients on hemodialysis in hemodialysis clinics. Data were collected from March to May 2007 using structured questionnaires and hematologic sample. Stepwise multiple regression was used to identify factors influencing sleep disorders among the demographic-clinical factors, depression and fatigue. Results: About 69% of the patients had a sleep disorders. There were significant differences in sleep disorders according to marital status, caregiver, religion, economic level, insurance, erythropoietin, somnifacient, and antihypertensive agents. But there were no differences according to age, gender, dialysis period, or antidepressants. Their sleep disorders had significant correlations with depression, and fatigue, and a significant negative correlation with Protein, Albumin, Phosphate and BUN. But there were no correlations with hematocrit, hemoglobin, creatinine, sodium, potassium, or calcium. Depression and fatigue were factors influencing sleep disorders. They accounted for 43.8% of the variance in sleep disorders in these patients. Conclusion: Findings provide an understanding of sleep disorders and the factors that are an influence in patients on hemodialysis. To promote sleep in these patients, nursing interventions to manage depression and fatigue are needed.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.141-146
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• 2012

Aluminum alloys have been used with various thicknesses suitable for light weight of structure. It is known that the thickness effect of material is an important factor affecting fatigue crack propagation under constant fatigue stress condition. In this work, we presented the behavior of fatigue crack propagation in thin plate compared to thick plate Al 2024-T3 alloy with referred thickness effect in a correlative equation determined by the shape factor and the loading factor. We chose two factors that are used in the correlative equation with considering that the experiments were carried out under a constant fatigue stress condition. The thickness ratio of thin plate compared to thick plate and the equivalent effective stress intensity factor ratio depending on thickness were chosen as shape and loading factors. A correlative equation is utilized to determine the equivalent effective stress intensity factor range of thin plate and identify the degree of increasing phenomenon of fatigue life in thin plate compared to thick plate.

• Journal of muscle and joint health
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• v.27 no.2
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• pp.169-176
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• 2020

Purpose: This study aims to investigate the factors affecting fatigue of care helpers in long-term care facilities. Methods: The subjects consisted of 131 care helpers at six long-term care facilities in Chungcheongnam-do. A survey was conducted between July and September 2019 to collect data, which were analyzed using t-test, ANOVA, Pearson's correlation coefficients, and multiple regression analysis.Results: An increase in fatigue of care helpers owing to taking care of over 10 patients a day, increase in emotional labor and sleep disturbance, and a decrease in economic status was observed. Their fatigue decreased when there was an increase in their subjective health status and job satisfaction. Work-related stress (β=.37, p<.001), emotional labor (β=.21, p=.014), and sleep disturbance (β=.18, p=.026) significantly predicted fatigue. These factors explained 37% of the total variance in fatigue (F=10.48, p<.001).Conclusion: In addition to improving the work environment, interventions that alleviate emotional labor and improve sleep quality, are needed to lower the fatigue of care helpers.