• 대한간호학회지
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• 제26권1호
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• pp.53-72
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• 1996

The Purpose of this study was to identify characteristics of fatigue and the relationship between fatigue and related factors in patients on hemodialysis. This study was a survey study using a cross-sectional design. The subjects for this study were 101 patients on hemodialysis who were registered in the six hemodialysis clinics among a total of eleven clinics in Seoul. The period of data collection was from February 28, 1995 to May 2, 1995. Data were collected through an interview with a structured packet and the physiological data. The tools used in this study were the Visual Analogue Scale-Fatigue developed by Lee et al(1990) and translated by Lee(1991), the fatigue interview schedule developed by this researcher, Zung's self rating depression scale(Zung, 1965), the self-efficacy scale developed by Sherer et al(1982) and the Norbeck Social Support Questionnaire(NSSQ) translated by Oh(1984). The collected data were analyzed using descriptive statistics(mean, standard deviation, frequency, range), Pearson correlation coefficients and Stepwise multiple regression. The results were as follows ; 1. Characteristics of Fatigue of hemodialysis patients : 1) 79 of 101 hemodialysis patients complained fatigue. 2) The mean fatigue score as measured by the VAS-F was 36.2mm. 3) The mean duration of fatigue was 2.9 hours 2. Characteristics of fatigue related factors : 1) The physiologic factor which included Hgb, Hct, BUN, creatinine, potassium and interdialytic weight gain deviated from normal range. 2) The psychological factor which included depression and self-efficacy was about the same level as for patients with other chronic diseases. 3) The environmental factor which included social support had wide variation. 3. The relationship between fatigue and related factors : 1) Interdialytic weight gain in the physiologica factor was the only valuable with fatigue （p＜.05） 2) The relationship between fatigue and the psychological factor of depression showed a positive and strong correlation（p＜.05）. According to the findings of this study, fatigue was highly correlated with the depression. This indicates that nurses should try to assess and control psychological factors when patients complain of fatigue rather than just considering physiological factors. Nursing has to develop effective nursing interventions to reduce fatigue in patients with chronic diseases using the relationship between fatigue and physiological, psychological and environmental factors.

• Structural Engineering and Mechanics
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• 제11권3호
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• pp.301-314
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• 2001

The purpose of this experimental study is to investigate the damage mechanism due to shear-fatigue behavior of high-strength reinforced concrete beams under repeated loading. The relationship between the number of cycles and the deflection or strain, the crack growths and modes of failure with the increase of number of cycles, fatigue strength, and S-N curve were observed through a fatigue test. Based on the fatigue test results, high-strength reinforced concrete beams failed at 57-66 percent of static ultimate strength for 2 million cycles. The fatigue strength at 2 million cycles from S-N curves was shown as about 60 percent of static ultimate strength. Compared to normal-strength reinforced concrete beams, fatigue capacity of high-strength reinforced concrete beams was similar to or lower than fatigue capacity of normal-strength reinforced concrete beams. Fatigue capacity of normal-strength reinforced concrete beams improved by over 60 percent.

• Nuclear Engineering and Technology
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• 제45권7호
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• pp.929-940
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• 2013

Environmental fatigue of the metallic components in light water reactors has been the subject of extensive research and regulatory interest in Korea and abroad. Especially, it was one of the key domestic issues for the license renewal of operating reactors and licensing of advanced reactors during the early 2000s. To deal with the environmental fatigue issue domestically, a systematic test program has been initiated and is still underway. The materials tested were SA508 Gr.1a low alloy steels, 316LN stainless steels, cast stainless steels, and an Alloy 690 and 52M weld. Through tests and subsequent analysis, the mechanisms of reduced low cycle fatigue life have been investigated for those alloys. In addition, the effects of temperature, dissolved oxygen level, and dissolved hydrogen level on low cycle fatigue behaviors have been investigated. In this paper, the test results and key analysis results are briefly summarized. Finally, an on-going test program for hot-bending of 347 stainless steel is introduced.

• Structural Engineering and Mechanics
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• 제38권4호
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• pp.443-457
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• 2011

The loss of strength in a structure as a result of cyclic loads over a period of life time is an important phenomenon for the life-cycle analysis. Service loads are accentuated at the areas of stress concentration, mainly at the connection of components. Structural components unavoidably are affected by defects such as surface scratches, surface roughness and weld defects of random sizes, which usually occur during the manufacturing and handling process. These defects are shown to have an important effect on the fatigue life of the structural components by promoting crack initiation sites. The value of equivalent initial flaw size (EIFS) is calculated by using the back extrapolation technique and the Paris law of fatigue crack growth from results of fatigue tests. We try to analyze the effect of EIFS distribution in a multiple site damage (MSD) specimen by using the extended finite element method (XFEM). For the analysis, fatigue tests were conducted on the centrally-cracked specimens and MSD specimens.

• 한국환경보건학회지
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• 제36권5호
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• pp.373-382
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• 2010

A number of recent studies have shown that occupational stress is closely associated with increased fatigue and decreased job satisfaction. This study was designed to assess stress in workers in the field of EIA (environment impact assessment) from July 2009 through september 2009, and questionnaires were uesd to analyze the stress scores and identify the primary factors influencing stress in this occupation. The number of respondents was 272 working in the Capital (Seoul and Kyunggido), Chungcheongdo, Jejudo area. A structured questionnaire was used to evaluate the participants' socio-demographics, job-related factors, health-related behaviors, occupational stress, reaction factor (self-perceived fatigue, job satisfaction) and buffer factor (social support). Occupational stress and self-perceived fatigue were assessed using the Korean Occupational Stress Scale-Short Form (KOSS-SF) and the Multidimensional Fatigue Scale (MFS), respectively. The analysis revealed a strong correlation between occupational stress, job satisfaction, and social support, with occupational stress being associated with an increased risk of fatigue and decreased job satisfaction. In the multiple regression analysis(stepwise), the main factors influencing occupational stress were found to be job satisfaction, supervisor, fatigue, working time, no. of personnel, career. The results of this study suggest that occupational stress is a determinant predictor of self perceived fatigue and job satisfaction. Thus, a strong recommendation is made for a stress management program for reduction of occupational stress, and for the development of relevant experts on the health and quality of life of environment impact assessment workers.

• 한국해양공학회지
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• 제1권2호
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• pp.93-100
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• 1987

Corrosion fatigue cracking of the austenitic stainless steel(bese metal & heat affected zone by TIG weld) was studied experimentally under the environments of various specific resistance and air. The characteristics of corrosion fatigue crack growth rate and the environmental constants of paris' rule were investigated for SUS 304 weldments in the various specific resistance. The influences of stress intensity factor range and corrosion on the crack growth rate were compared. The characteristics of corrosion fatigue cracking for the weldments were inspected from mechanical, electrochemical and microstructural point of view. Main results obtained are as follows: 1) As the specific resistance decreases, the environmental constant C of paris'rule increases(hence the corrosion fatigue crack growth rate is rapid), but the environmental constant m decreases, so the effect of corrosion to the crack growth rate is more susceptible than thet of stress intensity factor range. 2) As the stress intensity factor range decreases, the corrosion fatigue crack growth rate of heat affected zone is more susceptible than that of the base metal. 3) The corrosion fatigue crack growth rate of the heat affected zone is more rapid than that of the base metal, because of the phenomenon of softening and the less noble potential coused by wedlding heat cycle. 4) The corrosion fatigue cracking of SUS 304 weldment appears transgranular fracture.

• 대한토목학회논문집
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• 제28권6D호
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• pp.819-829
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• 2008

콘크리트 포장에 반복적으로 재하되는 차량의 하중에 의하여 슬래브의 동적강도는 꾸준히 감소하며 장기적으로 피로균열이 발생한다. 온도와 수분의 분포에 의하여 슬래브 내에는 항상 응력이 도입되어 있으므로 이를 고려한 후 차량하중의 영향을 추가해야만 보다 정확하게 콘크리트 포장의 피로수명을 예측할 수 있다. 따라서, 본 연구에서는 기존에 개발된 대표적 피로모형들의 각종 인자들을 평가하고 모형으로부터 데이터를 추출하여 환경하중을 고려하는 새로운 피로모형을 개발하였다. 국내 각 지역의 기상 및 교통조건을 사용하여 국내에서 일반적으로 시공되는 콘크리트 포장에 대한 피로해석을 수행하여 개발된 피로모형의 적용성을 평가하였다. 슬래브 하부에서 발생한 상향의 균열보다는 슬래브 상부의 인장응력에 의한 하향의 균열이 피로파손의 주요한 원인으로 판단되었다. 본 연구결과를 바탕으로 한 후속 연구를 통하여 차량의 속도가 고려된 피로해석도 수행될 수 있을 것으로 기대된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.17-22
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• 2007

Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa, $315^{\circ}C$ of a operating pressurized water reactor. The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside the small autoclave. So the magnet type LVDT's were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. FEM calculated the displacement and the strain of the gauge length from the data measured at the shoulders. Tensile test properties in elastic and plastic behavior of CF8M material were used in the FEM analysis. A series of low cycle fatigue tests simulating the cyclic strain hardening effect verified that the FEM calculation was well agreed with the simulated tests. The process and method developed in this study would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2600-2609
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• 2021

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (F_en) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.450-457
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• 2022

The construction industry is demanding, dynamic, and complex making it difficult for workers to recognize hazards. The nature of construction tasks exposes workers to several critical risk factors, such as a high rate of exertion and fatigue. Recent studies suggest that fatigue may impact hazard recognition in the construction industry. However, most studies rely on subjective measures when assessing the relationship between physical fatigue and hazard recognition, limiting such studies' efficacy. Thus, this study examined the relationship between physical fatigue and hazard recognition using a controlled experiment. Worker fatigue levels were captured using physiological data and a subjective exertion scale. The findings confirmed that physical exertion plays a significant role in hazard recognition skills (p < 0.05). This research contributes to theory and practice by providing a process for objectively assessing the influence of physical fatigue on worker safety and providing construction professionals with some critical insight needed to improve workplace safety.