• Composites Research
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• 제12권2호
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• pp.62-69
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• 1999

복합재료가 피로하중을 받으면 재료 내부에 손상이 누적되며, 이는 재료의 물성 변화로 나타난다. 본 연구에서는 손상을 나타내는 인자로 피로계수를 사용하였다. 피로계수와 참고계수로 정의되는 손상함수로부터 복합재료의 피로수명 예측을 이론적으로 연구하였다. 제안된 모델들은 인가 응력 수준, 피로주기 및 피로수명의 함수로 유도하였다. 예측 결과는 유리섬유/에폭시 복합재료와 유리섬유/폴리에스터 복합재료를 사용한 다중응력 피로 실험 데이터를 이용하여 검증하였다.

• 대한기계학회논문집
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• 제6권2호
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• pp.107-112
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• 1982

In order to analyze and investigate in the fatigue behavior of the notched specimens under the two level stressing, the U-notched specimens of structural carbon steel which is generally used is prepared. The obtained results are summarized as follows; (1) The fatigue limit of the U-notched specimens is lower than that of the unnotched. The fatifue notch factor (.betha.) of the U-notched specimens is 1.44 for mild steel and 1.52 for harden steel. The notch sensitivity (q) is 0.68 for mild steel and o.8 for harden steel. That is, these facts show that harden steel is more sensitive to the notch than mild steel. (2) The fatigue life time of the U-notched specimens under the overstressing is shorter than under the constant stressing, and the degree of fatigue life time decrease is different to each stress level; the degree for the high stress level is more than for the low stress level. (3) The fatigue life time of the U-notched specimes under the understressing is longer than under the constant stressing, and the degree of fatigue life time increase for the low stress level is more than for the high stress level.

• 대한금속재료학회지
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• 제48권6호
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• pp.489-497
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• 2010

The remaining life estimation of the level luffing crane component, which has operated for about 20 years is examined carefully, especially on the crane structures. To analyse the crane sructures, the basic load and load combination needed to be considered. We modeled various parts of the level luffing crane to analyse fatigue. Fatigue analysis results showed that the level luffing crane is in the fatigue life so that the crane is in the safe state in fatigue cumulative damage. Analysis results show that the remaining life of a jib upper beam would be about 10 years therefore, the level luffing crane should be stable for fatigue for that period.

• Steel and Composite Structures
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• 제39권3호
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• pp.229-241
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• 2021

This work focused on aluminum foam sandwich (AFS) with different foam core densities and different face-sheet thicknesses subjected to constant amplitude three-point bending cyclic loading to study its fatigue performance. The experiments were conducted out by a high frequency fatigue test machine named GPS-100. The experimental results showed that the fatigue life of AFS decreased with the increasing loading level and the structure was sensitive to cyclic loading, especially when the loading level was under 20%. S-N curves of nine groups of AFS specimens were obtained and the fatigue life of AFS followed three-parameter lognormal distribution well. AFS under low cyclic loading showed pronounced cyclic hardening and the static strength after fatigue test increased. For the same loading level, effects of foam core density and face-sheet thickness on the fatigue life of AFS structure were trade-off and for the same loading value, the fatigue life of AFS increased with aluminum foam core density or face-sheet thickness monotonously. Core shear was the main failure mode in the present study.

• 한국직업건강간호학회지
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• 제24권4호
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• pp.372-380
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• 2015

Purpose: The purpose of this study was to seek ways to improve the quality of life of workers by separating workers into the low fatigue group and the severe fatigue group depending on the level of fatigue level, and analyzing and understanding the difference between quality of life and job stress according to the fatigue level. Methods: For the 'Development of Mibyeong management system which was a consumer-directed health care service', the data of job stress, fatigue and quality of life was collected from 115 workers who visited the oriental hospitals located in J city and C city from Jul, 2012 to Dec, 2012. Results: The severe fatigue group showed significantly higher job stress than the low fatigue group in physical environment (p=.004), job demand (p<.001), interpersonal conflict (p=.012), lack of reward (p=.062). The severe fatigue group showed lower degrees both in physical component summary (PCS) (p<.001) and mental component summary (MCS) (p<.001) measured by SF-12 and the quality of life (p<.001) measured by EQ5D than the lower fatigue group. A relatively strong negative correlation was found in the item of mental component summary (MCS) measured by SF-12. Conclusion: Considering our results that high fatigue level show negative impact on quality of life and job stress, we suggest to provide a variety of health promotion strategies to improve the quality of life through the prevention and relief of fatigue for workers.

• 대한기계학회논문집
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• 제12권4호
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• pp.790-805
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• 1988

본 연구에서는 유리섬유 강화 에폭시 복합재료의 파괴 강도와 피로 수명을 정 규분포, 로그 정규 분포와 2모수 및 3모수 Weibull 분포 함수의 기대값으로 살펴 보았 다. 2연속 응력 피로 실험 [작은 응력에서 큰 응력으로의 실험(low-high test), 큰 응력에서 작은 응력으로의 실험(high-low test)]의 결과도 분포 함수들을 사용하여 분 석하였다. 비통계학적 누적 손상 법칙들(non-statistical cumulative damage rules) 을 2연속 응력 피로 수명 분산 예측에 이용하기 위해서 동등 순위 가정(equal rank assumption)을 확장하여 수정하였다. 수정한 누적 손상 모형은 Miner의 법칙, Brou- tman과 Sahu의 손상모형 및 Hashin과 Rotem의 모형 등이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1298-1301
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• 2003

The purpose of this research is to evaluate the effect of pre-load and fatigue life of the distracted one-level pedicle screw system. A spring, which acted as a substitute of the ligament, was installed in the one-level pedicle screw system before testing. The static and fatigue properties are now being tested, which includes 6mm rod to 6mm screw, 6mm rod to 6.5mm screw and 6.35mm rod to 6.5mm screw, under pre-load. Until now as test data were analyzed, 6mm rod to 6.5mm screw was found to have the best performances of stillness and fatigue lift, while 6mm rod to 6mm screw showed the shortest fatigue life. If the stiffness of screw was bigger than that of rod. the fatigue life was prolonged. The fatigue life of the distracted pedicle screw was proved to be shorter than that of the one-level pedicle screw system. So the fatigue life was shortened because of the effect of the spring on the flexibility and stiffness of the rod. In order to obtain the stability of the pedicle screw, more tests are under doing on this topic.

• 대한간호학회지
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• 제33권5호
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• pp.618-624
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• 2003

Purpose: The purpose of the study was to investigate fatigue, depression and sleep in young adult and middle-aged. Method: The convenient sample consisted of 415 subjects from 20 to 59 years old. Data were collected using a self-report questionnaire from July to October, 2001. The V AS-F and CES-D were utilized to measure the level of fatigue and depression. Sleep duration and sleep satisfaction were measured based on the subject's self-report. Result: The result of the study revealed that the level of fatigue and depression was higher among young adult than middle-aged. Considering age and gender, the level of fatigue and depression was higher among young adult women and middle-aged men. Depression and sleep satisfaction influenced on the fatigue. Conclusion: Health care providers need to concern about fatigue and depression in young adult women and middle-aged men. Especially, more concern and intervention programs are needed for young adult women and middle-aged men.

• Journal of Korean Biological Nursing Science
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• 제14권4호
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• pp.258-267
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• 2012

Purpose: The purpose of this study was to identify the relationship between energy intake and fatigue in cancer patients receiving chemotherapy. Methods: A total of 106 subjects had participated in this study. Data were collected at a university hospital in D city from September 1st to November 10th, 2010. Energy intake including carbohydrates, protein and fat was measured by scale and analyzed using Can Pro 3.0 program. Fatigue level was measured by the Revised Piper Fatigue Scale. Data were analyzed using descriptive analysis, t-test, ANOVA and Pearson correlation coefficient with SPSS/WIN 15.0. Results: The mean calorie intake during chemotherapy was $906.53{\pm}201.28Kcal/day$ which was 45.3% of the recommended daily calorie intake. The mean of protein intake level was $43.62{\pm}11.13g/day$, and it was low compared to the recommended daily protein intake. Calories, carbohydrates, and protein levels on 3rd day after chemotherapy were significantly lower than those of 2nd day after chemotherapy (p<.001). The fatigue level during chemotherapy was $5.77{\pm}0.77$ which was moderate level of fatigue. There was a significant negative interrelation between energy intake and fatigue. Conclusion: Theses results suggested that nursing approaches to encourage dietary intake may be helpful to reduce fatigue for cancer patients receiving chemotherapy.

• 대한통합의학회지
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• 제8권2호
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• pp.139-147
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• 2020

Purpose : Proprioceptive position sense plays a key role in providing joint stability, and multiple factors are related to proprioceptive position sense. Thus, this study aimed to determine the effects of body composition, particularly skeletal muscle mass on proprioceptive position sense following muscle fatigue. Methods : Healthy female subjects agreed to have their body composition analyzed. Only subjects who had 18.5-22.9 kg/㎡ of BMI (body mass index) were included in this study, and the participants were divided into two groups by skeletal muscle mass level. The experimental group had a level of skeletal muscle lower than the standard level (n=9), while the control group showed a standard or high level of skeletal muscle mass (n=11). To determine the change in proprioceptive position sense of the knee joint, the absolute angle error (AAE) was evaluated following muscle fatigue on low extremity. The muscle fatigue was induced by isokinetic resistance exercise program of Biodex system. AAE was measured by the Biodex system and compared the result before and after muscle fatigue. Results : The experimental group showed a significant AAE difference between before (3.16±2.48 °) and after (5.40±2.61 °) muscle fatigue. In addition, there was a AAE difference between the experimental (5.40±2.61 °) and control groups (3.53±1.67 °) after fatigue; however, there was no significance. Those results indicated that low level of skeletal muscle mass might influence the proprioceptive position sense of the knee joint after muscle fatigue. Conclusion : Thus, maintaining the proper level of skeletal muscle mass is pivotal to reduce the risk of injury following muscle fatigue in ADL or sport activities.