• 한국해양공학회지
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• 제17권2호
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• pp.54-59
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• 2003

The characteristics of the parameters for the probability distribution of fatigue crack growth life, using the non-Gaussian random process simulation method is investigated. In this paper, the material resistance to fatigue crack growth is treated as a spatial random process, which varies randomly on the crack surface. Using the previous experimental data, the crack length equals the number of cycle curves that are simulated. The results are obtained for constant stress intensity factor range conditions with stress ratios of R=0.2, three specimen thickness of 6, 12 and 18mm, and the four stress intensity level. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Wiubull,, showing a slight dependence on specimen thickness and stress intensity level. The shape parameter, $\alpha$, does not show the dependency of thickness and stress intensity level, but the scale parameter, $\beta$, and location parameter, ${\gamma}$, are decreased by increasing the specimen thickness and stress intensity level. The slope for the stress intensity level is larger than the specimen thickness.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.301-306
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• 2002

The characteristics of parameters for the probability distribution of fatigue crack growth lives by the non-Gaussian random process simulation method is investigated. In this paper, the material resistance to fatigue crack growth is treated as a spatial random process, which varies randomly on the crack surface. Using the previous experimental data, the crack length - the number of cycles curves are simulated. The results are obtained for constant stress intensity factor range conditions with stress ratio of R=0.2, three specimen thickness of 6, 12 and 18mm, and the four stress intensity level. The probability distribution function of fatigue crack growth lives seems to follow the 3-parameter Wiubull and shows a slight dependence on specimen thickness and stress intensity level. The shape parameter, ${\alpha}$, does not show the dependency of thickness and stress intensity level, but the scale parameter, ${\beta}$, and location parameter, ${\upsilon}$, are decreased by increasing the specimen thickness and stress intensity level. The slope for the stress intensity level is larger than the specimen thickness.

• 여성건강간호학회지
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• 제11권2호
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• pp.163-168
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• 2005

Purpose: This study was to identify the relationship between fatigue and sleep disturbance in adult women so as to provide basic data for developing a women's health promotion program and nursing intervention. Method: A convenience sample of 184 women who visited a Well-baby clinic at P city Maternal child center during October in 2004 was obtained. Data was collected by self-administered questionnaires. Results: The Subjects' mean age was 36.87 years and 70% were employed and had more education than high school. The mean level of fatigue was 56.65, mean sleeping hours were 6.54, and time until falling asleep was 17.58 minutes. Scores of fatigue differed by subject's age, level of education, and menstruation status. In addition, sleeping hours differed by age, occupation status, and income level. There were significant low levels of correlation between fatigue and sleeping hours (r=-.16) and getting up too early (r=-.15). Conclusion: This study concludes that fatigue and sleeping patterns have a significant relationship.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.137-145
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• 2003

본 연구에서는 국산 PS 강봉의 직경, 반복최소응력 및 반복최대응력 등을 실험변수로 하여 직접 인장 피로실험을 수행하였다. 정적 인장실험 결과, 국산 PS 강봉의 응력 - 변형률 곡선과 극한강도 등을 얻었다. 또한, 피로실험에서의 특징적인 실험결과는 PS 강봉의 직경은 피로 수명에 중요한 인자가 아니며, 반복 최소응력의 크기는 국산 PS 강봉의 피로수명에 매우 큰 영향을 미치는 것으로 나타났다. 이러한 피로실험결과를 통계 분석하여 PS 강봉의 응력 범위 및 반복 최소응력 등을 변수로 하는 피로강도 예측식을 제안하였다. 피로실험 중, 시편중앙에 설치한 Extensometer를 이용하여, 변형률의 변화를 측정하였으며, 측정된 변형률 변화현상에서 탄성계수의 변화현상을 구하였다. 변형률 증가현상은 3단계의 형태 즉, 초기에 급격한 증가 후 서서히 증가하며 파괴 직전에 급격하게 증가하는 형태로 나타났다. 탄성계수의 변화현상은 변형률 변화현상과 유사하게 감소하는 것으로 나타났으며 응력수준은 탄성계수 변화에 큰 영향을 주지 않는 것으로 나타났다.

• 대한간호학회지
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• 제36권7호
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• pp.1224-1231
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• 2006

Purpose: This study was conducted to identify comprehensive predictors of fatigue in cancer patients. Methods: One hundred ten cancer patients visiting in-patient or out-patient clinics of a university hospital located in Incheon participated in this study. Results: The hematologic indicators (WBC and Hemoglobin) were significant fo. explaining fatigue. The psychological factors of fatigue were statistically significant. Both anxiety and depression, included as psychological factors, were significant in explaining fatigue in cancer patients. The influence of physical factors on fatigue was also statistically significant. Among the variables included as physical factors, pain, nausea/vomiting/anorexia, and sleep disturbance were significant whereas, dyspnea was not significant. The influence of the daily activity factor on fatigue was statistically significant. Among the variables included as daily activity factors, regular exercise or not and the usual activity level were significant in explaining fatigue of cancer patients, while the level of rest was not statistically significant. Conclusions: From the study results fatigue of cancer patients appeared to be influenced by multidimensional factors, such as physiological, physical, psychological, and activity related factors.

• 대한예방한의학회지
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• 제19권2호
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• pp.67-74
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• 2015

Objective : The aim of this study was to investigate fatigue-related factors including socio-demographic variables and life styles among workers in the automobile manufacturing industry. Method : The subjects were 22,937 individuals who had received health examination by Korean Medical doctors and responded to questionnaires for 8 months from March to November in 2011. The fatigue index was measured by heart rate variability (HRV) in an automobile manufacturing industry. A multivariate analysis with SPSS version 19.0 was used to examine the relationship between fatigue and other factors including ages, smoke consumption, drinking frequency, exercise frequency, occupational category, conjugal condition. Results : In comparison between normal and very bad level of fatigue, factors of ages, smoking, drinking, and exercise showed significant difference(p<0.05). In addition, when normal and bad fatigue were compared, ages, smoking, exercise also produced significant difference(p<0.05). Furthermore, in normal and good level of fatigue comparison, occupation and smoking yielded significant difference(p<0.05). Finally, in other comparisons between normal and very good fatigue, exercise, smoking and occupation revealed significant difference(p<0.05). Conclusion : The results of this study suggest that age increase affects fatigue negatively, whereas exercise and drinking of once or twice per a week can have positive correlations.

• 한국강구조학회 논문집
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• 제9권2호통권31호
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• pp.159-169
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• 1997

최근 중화물 차량의 적재율 증가와 교통량의 증가 등으로 인해 강도로교에서는 반복하중에 의한 피로손상이 많이 발생하고 있으며 이러한 손상은 교량의 안전성에 심각한 영향을 미치고 있다. 따라서 사용기간 동안에 발생하는 피로손상을 합리적으로 반영할 수 있는 피로설계하중을 결정하는 것은 매우 중요하다. 본 연구에서는 먼저 미국 AASHTO의 LRFD 피로설계방법을 고찰하였으며 그 결과 교폭에 관계없이 1대의 피로설계트럭을 재하하여 설계하는 것은 일정한 안전수준을 확보하지 못하는 것으로 분석되었다. 따라서, 교폭에 따라 설계하중 재하방법을 다르게 하는 것이 보다 일관성 있는 안전수준을 가지는 것으로 나타났으며 본 연구에서는 다양한 교량구조형식과 통행특성에 따라 발생하는 피로손상을 합리적으로 반영할 수 있는 피로설계하중의 재하방법과 수준 및 형식을 제시하였다.

• 대한인간공학회지
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• 제32권1호
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• pp.139-144
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• 2013

Objective: The current study investigated a non-obtrusive measure for detecting physical fatigue based on the analysis of formant frequencies of human voice. Background: Fatigue has been considered as a main cause in industrial and traffic accidents. Therefore, it is critical to detect worker's fatigue for accident prevention. Method: After running exercises on a treadmill, participants were instructed to read a sentence and their voices were recorded under four different physical fatigue levels. Korean vowels of "아", "어", "오", "우", and "이" from the voice recorded were then used to collect formant 1 frequencies. Results: Results of separate ANOVAs showed a significant main effect of physical fatigue on formant 1 frequency of "아", "어", and "이". Furthermore, post-hoc comparisons revealed that formant 1 frequency of "아" was most sensitive to physical fatigue level employed in this experiment. Conclusion: Formant 1 frequencies of some vowels significantly decrease as the physical fatigue level increases. Application: Potential application of this study includes the development of a measure of physical fatigue state that is free from sensor attachment and requires little preparation.

• 성인간호학회지
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• 제15권4호
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• pp.617-627
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• 2003

Purpose: The purpose of this study is to investigate fatigue and its related factors in cancer patients receiving radiotherapy. Method: The subjects of this study consisted of 98 patients receiving radiotherapy. Subjects were recruited from C University Hospital radiation oncology unit located in Gwangju from March to May, 2001. Questionnaire and medical records were used for data collection. The obtained data was analyzed using SAS program that included descriptive statistics, t-test, ANOVA, Post-hoc test(Fisher's LSD) and Pearson's correlation coefficients. Result: The fatigue perceived by the subjects was middle level ($5.59{\pm}1.59$) and 72.4% of them reported greater than 5 points. The subjects in no religion, low income, and spouse caregiver groups experienced the higher fatigue than another groups, respectively. The subjects in nasopharyngeal cancer, head & neck radiation site, and analgesics medication groups did, experience fatigue as well. The fatigue not only positively correlated with symptom distress, disruption of usual activity, sleep dissatisfaction, and mood state, but also negatively with less family support. Conclusion: Cancer patients receiving radiotherapy experience the middle level of fatigue and it correlates with the multi-dimensional factors. However, further research is needed to identify the changes in fatigue over the radiotherapy period through longitudinal design and to develop nursing intervention for fatigue decrease.

• 성인간호학회지
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• 제20권3호
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• pp.443-451
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• 2008

Purpose: This study is to examine how dementia day care service affects fatigue, depression and life satisfaction of caregiver. Methods: The study was conducted using a convenient sampling method from 6 Dementia Day Care Center in Incheon. Thirty nine primary caregivers answered the questionnaires. Pre-test was done before demented elders start using the dementia day care center and post-test was done five months after. Data were analyzed by using descriptive statistics and paired t-test. Results: There was a significant difference in caregivers' fatigue level after using dementia day care service(t=2.188, p=.035). Results of subcategories were as follows; There was a significant difference in caregivers' physical fatigue level(t=2.270, p=.029) and psychological fatigue level(t=2.277, p=.029) after using dementia day care service. However, there was not significant difference in caregivers' neurological fatigue level(t=1.312, p=.197). There was a significant difference in caregivers' depression level(t=3.066, p=.004) and life satisfaction(t=-2.131, p=.040) after using dementia day care service. Conclusion: The results indicated that dementia day care service is helpful for family with demented elders. Therefore it is necessary to expand dementia day care center in terms of its size and numbers in order to support increasing number of demented elders and their families.