• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.953-962
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• 1987

Domestic dissimilar structural steels, SM 45 C and SUS304 were friction welded under optimal welding condition and the micro-artificial holes were drilled at SM 45 C base metal, SM 45 C HAZ, welded zone, SUS 304 HAZ, and SUS 304 base metal for fatigue behavior tests. In this study, the fatigue limit and the behavior of micro-crack propagation, crack propagation rate, and its dependency on stress intensity factor under the low stress level and high stress level of bending stress have been investigated. The results obtained are as follows. (1) The fatgiue strength of the portion of SM45C B.M., SM45C HAZ, welded zune, SUS304 HAZ and SUS304 B.M. on notched friction welded specimens are 20 kgf/mm$^{2}$, 32 kgf/mm$^{2}$, 27kgf/mm$^{2}$, 29kgf/mm$^{2}$, and 29kgf/mm$^{2}$, respectively. (2) The fatigue strength of welded zone of unnotched and notched specimens are 32.5kgf/mm$^{2}$, and 27kgf/mm$^{2}$, respectively. (3) Micro-crack initiation in the welded zone, HAZ, and each base metals occurrs simultaneously in front and rear of micro-hole tips in the view of the rotational directions. (4) Fatigue crack propagates more slowly in the welded zone than in another protions of specimen, regardless of the magnitude of the stress level. (5) Fatigue crack propagation rates were plotted as a function of stress intensity range. The value of m in the equation da/dN=C(.DELTA.K)$^{m}$ was found to range from 2.09-2.55 in this study.

• Journal of the Korean Dietetic Association
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• v.19 no.4
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• pp.373-388
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• 2013

The purpose of this study was to investigate the effects of a nutrition education and exercise on nutritional status in hemodialysis patients, with regard to quality of life (QoL), and fatigue. The subjects were divided into two groups : an educated (E) group (11 men and 9 women) and a non-educated (NE) group (7 men and 22 women). The educated group received a nutrition education and a regular exercise program for 3 months. Data on anthropometric indices and biochemical parameters were obtained from medical records. Dietary habits and nutrient intake were assessed through questionnaires and three-day food records. QoL (through the SF-36 questionnaire) and fatigue (measured by a visual analogue scale questionnaire) were assessed before and after the interventions. Dietary habit scores regarding food variety and fluid intake control significantly increased (P<0.05) after the nutrition education. Furthermore, the intake of total energy, carbohydrates, Fe, and vitamin A significantly increased (P<0.05). Vitamin C intake also significantly increased (P<0.01). Hb levels decreased whereas TG levels increased in the NE group. BUN levels decreased in the E group. After the nutrition education, QoL aspects, such as feelings of pain and general health, and the total score significantly increased (P<0.05) and the level of fatigue score decreased (P<0.01). The results of this study indicate that nutrition education and exercise for hemodialysis patients provides changes in dietary habit, daily nutrient intake, biochemical parameters, QoL, and the level of fatigue. Therefore, nutrition education and exercise help improve nutritional status and QoL.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3_1spc
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• pp.504-508
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• 2013

This paper describes in detail the life prediction models and simulations of thermal fatigue under different mold compounds and chip sizes for wafer-level embedded SiP. Three-dimensional finite element models are built to simulate the viscoplastic behaviors for various mold compounds and chip sizes. In particular, the bonding parts between a mold and silicon nitride (Si3N4) are carefully modeled, and the strain distributions are studied. Three different chip sizes are used, and the effects of the mold compounds are observed. Through the numerical studies, it is found that type-C, which has a relatively lower Young's modulus and higher CTE, has a better fatigue life than the other mold compounds. In addition, the $4{\times}4$ chip has a shorter life than the $6{\times}6$ and $8{\times}8$ chips.

• Journal of East-West Nursing Research
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• v.18 no.2
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• pp.66-73
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• 2012

Purpose: This study examines the effect of aroma inhalation therapy with lavender and rosewood essential oils for alleviating fatigue and enhancing quality of sleep in nurse shift workers. Methods: The data were collected from November 9th to 27th in 2009 at four hospitals located in Seoul. Total 60 nurses who started their night-shift works were chosen for the study and allocated to either experimental group or control group. The experimental group had had aroma inhalation therapy with lavender and rosewood for 2 weeks and was compared the level of fatigue and quality of sleep with those of the control group. Results: Significant differences were shown between the experimental group and the control group. After 2 weeks, the nurses in experimental group reported significantly lower level of fatigue and higher quality of sleep compared to the nurses in control group. Conclusion: Therefore, aroma inhalation therapy by using lavender and rosewood essential oils can be an effective intervention for relieving the level of fatigue and enhancing quality of sleepf for nurse shift workers.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.354-359
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• 2014

The objective of this study is to examine the fatigue behavior in compression of normal-weight and lightweight concrete mixtures with high volume supplementary cementitious material(SCM). The selected binder composition was 30% ordinary portland cement, 20% fly-ash, and 50% ground granulated blast-furnace slag. The targeted compressive strength of concrete was 40 MPa. For the cyclic loading, the constant maximum stress level varied to be 75%, 80%, and 90% of the static uniaxial compressive strength, whereas the constant minimum stress level was fixed at 10% of the static strength. The test results showed that fatigue life of high volume SCM lightweight concrete was lower than the companion normalweight concrete. The value of the fatigue strain at the maximum stress level intersected the descending branch of the monotonic stress-strain curve after approximately 90% of the fatigue life.

• Journal of Nutrition and Health
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• v.38 no.2
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• pp.117-124
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• 2005

We investigated the effects of prolonged exposure in hot environmental condition and ingestion of fluid on various physiological variables including plasma glucose, lactate, the rating of perceived exertion (RPE), and heart rate as well as golf putting performance. Six male professional golfers were voluntarily participated in three different putting trials which were separated by seven days of time interval period. Three different putting trials were conducted at either 20℃ or 32℃, or 32℃ + Fluid ingestion. Performing 32℃ + Fluid ingestion trial, all subject ingested sport drink as much as their body mass was decreased. For each experiment, all subjects were undertaken total 48 putting, which separated by four x 12 putting in four different time points (i.e., Rest, 1 hr, 2 hr, and 3 hr). Plasma glucose concentration was significantly decreased with hot ambient condition but it was almost fully recovered by fluid ingestion. Plasma lactate concentration was significantly higher when subjects were exposed in hot environmental condition, and it did not change with fluid ingestion. There was a no different in putting performance and psychological fatigue level (performed by GRID test) at any environmental conditions. The RPE, commonly used for evaluating of physical fatigue level, was significantly dropped by fluid ingestion which indicates lower physical fatigue level. In addition to this, heart rate (HR) was also significantly decreased after fluid ingestion. Based on these results, it was concluded that the ingestion of fluid during prolonged exposure in hot ambient condition decrease the degree of physical fatigue levels and heart rate, which will possibly improve the golf performance when exposed in extreme weather condition in summer. (Korean J Nutrition 38(2): 117～124, 2005)

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.245-252
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• 2016

The development of Top-Mounted In-Core Instrumentation(TM-ICI) is an ongoing project to reduce the risk due to severe accidents by inserting the instrumentation into a reactor closure head instead of a reactor bottom head. As part of this project, environmental fatigue analyses for TM-ICI nozzle have been performed using two methods of NUREG/CR-6909 and Code Case N-761. TM-ICI nozzle is subjected to transient loads for level A, level B and test conditions that should be evaluated for a fatigue analysis. It is found that a cumulative usage factor considering reactor coolant environment for TM-ICI nozzle is evaluated as less than 1, which is ASME Code allowable criteria of a fatigue analysis.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.90-98
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• 2017

This paper is concerned with air traffic controllers' fatigue and stress that they experience during their daily job particularly as being shift workers. Previous researches reveal that the controllers' fatigue and stress increase by several factors including time spent at work, traffic intensity, visibility, etc. The researches also indicate that air traffic controllers' fatigue and stress can be reasonably surrogated by their heart rate. We set three hypotheses relating the influencing factors and the fatigue and stress represented by the heart rates. Using wrist bands, air traffic controllers' heart rates at various situations are collected at Choongju airport. The hypothetical tests explicitly confirm that the heart rate is highly correlated with the traffic level and the time spent at work. In particular, it be shown that even when handling the same traffic level, air traffic controllers' stress level increases as the time they spent at work increases.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.85-93
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• 1992

The only hardness of 2nd phase of martensite in dual phase steel which was composed of the martensite and ferrite was changed. Fatigue test was conducted by cantilever type of self-made rotated bending fatigue testing machine. The corrosion fatigue fracture behaviors of dual phase steel were investigated in 3% NaCl solution at $N_f$ = $1.5\times$$10^5$ $N_f$=1.0 $\times$ $10^6$ cycles. The fatigue strength was increased with increasing the hardness of 2nd phase. The size and number of corrsion pits were influenced by the 2nd phase hardness and pits remain constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of $\Delta$K and da/dn has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the higher the corrosion fatigue life becomes. Corrosion fatigue fracture behavior was effected by mechanics in case of $N_f$=1.5$\times$10$^5$$N_f$=1.5$\times$10$^6$ cycles.

• Research in Community and Public Health Nursing
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• v.14 no.4
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• pp.699-706
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• 2003

The objective of this study is to find out the difference in perceptional fatigue and health promoting behavior between hospital nurses and public health nurses. The subjects of this study were 141 hospital nurses and 73 public health nurses in Daejeon. Data were collected using a self-reporting questionnaire during the period from the 5th to 16th of March 2003. Collected data were analyzed using SPSS program. Real number, percentage, mean and standard deviation were calculated, and $x^2$-test and t-test, ANOVA, Pearson's correlation coefficient, stepwise multiple regression procedures were carried out. The findings of this study as follows: 1. The mean score of health promoting behavior was 2.71. 2. There were statistically significant differences in health promoting behavior according to age, marital status, family status, residency, educational level, income, the length of work experience and the field of work. (p<0.05) 3. There were statistically significant differences in fatigue according to age, marital status, family status, educational level, income, the length of work experience, perceived health status and the field of work. (p<0.05) 4. The fatigue was found to be in significant negative correlations with health promoting (r=-0.358, p<0.000) and self efficacy (r=-0.314, p<0.000). On the contrary, a significant positive correlation was found between fatigue and perceived barriers (r=0.210, p<00.01). 5. There were five predictors affecting health promoting behavior, which were self-efficacy, income, perceived benefit, fatigue and family support. The most influential factor was self-efficacy that made 31% of prediction, followed by income (6%), perceived benefit (5.2%), fatigue (2.2%) and family support (1.7%) in their order. As a whole, these factors made 46.1% of prediction of health promotion behavior.