• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.655-670
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• 2004

This paper aims to evaluate the effect of typhoons on fatigue damage accumulation in steel decks of long-span suspension bridges. The strain-time histories at critical locations of deck sections of long-span bridges during different typhoons passing the bridge area are investigated by using on-line strain data acquired from the structural health monitoring system installed on the bridge. The fatigue damage models based on Miner's Law and Continuum Damage Mechanics (CDM) are applied to calculate the increment of fatigue damage due to the action of a typhoon. Accumulated fatigue damage during the typhoon is also calculated and compared between Miner's Law and the CDM method. It is found that for the Tsing Ma Bridge case, the stress spectrum generated by a typhoon is significantly different than that generated by normal traffic and its histogram shapes can be described approximately as a Rayleigh distribution. The influence of typhoon loading on accumulative fatigue damage is more significant than that due to normal traffic loading. The increment of fatigue damage generated by hourly stress spectrum for the maximum typhoon loading may be much greater than those for normal traffic loading. It is, therefore, concluded that it is necessary to evaluate typhoon induced fatigue damage for the purpose of accurately evaluating accumulative fatigue damage for long-span bridges located within typhoon prone regions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2353-2360
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• 2000

Statistical fatigue properties of metallic materials are increasingly required for reliability design purpose. In this study, static and fatigue tests were conducted and the normal, log-normal, two -parameter Weibull distributions at the 5% significance level are compared using the Kolmogorov-Smirnov goodness-of-fit test. Parameter estimation were compared with experimental results using the maximum likelihood method and least square method. It is found that two-parameter Weibull distribution and maximum likelihood method provide a good fit for static and fatigue life data. Therefore, it is applicable to the static and fatigue life analysis of the spheroidal graphite cast iron. The P-S-N curves were evaluated using log-normal distribution, which showed fatigue life behavior very well.

• PNF and Movement
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• v.17 no.3
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• pp.481-486
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• 2019

Purpose: This study examined the effect of calf muscle fatigue on postural sway according to foot posture (a pes cavus, a normal foot, and a pes planus). Methods: The subjects of this study were 12, 11, and 9 students of U University with a pes cavus, a normal foot, and a pes planus, respectively, according to a Navicular Drop Test. Postural sway was measured with a balance instrument (BioRescue, RM Ingenierie, France) while the subjects stood static on two legs as well as during one-leg standing using the dominant leg in two conditions (with the eyes open and with the eyes closed for 30 seconds). Muscle fatigue was then induced in the calf muscle of the dominant leg, and both muscle fatigue and postural sway were measured using an EMG. To compare the degree of postural sway between the three groups after muscle fatigue was induced, the change values were calculated. The results were analyzed using a Kruskal-Wallis test, and a post-hoc test was conducted using the Bonferroni correction. Results: Significant inter-group differences were detected for postural sway during two-leg standing with the eyes closed and during one-leg standing with the eyes open and with the eyes closed (p<0.05). The post-hoc test showed significant differences between the pes cavus and normal foot groups and between the pes planus and normal foot groups for all three variables (p<0.05). However, no significant difference was detected between the pes cavus and pes planus groups (p>0.05). Conclusion: The results of this study show that the pes cavus and pes planus cause more fatigue and postural sway than a normal foot. Therefore, attention should be paid to changes in balance caused by muscle fatigue.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.3
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• pp.163-169
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• 2006

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases into 50-70% of the plain fatigue strength. The connecting rod for automobile has been used in special environments and various loading conditions. Failure of connecting rod in automotive engine may cause catastrophic situation. In this study, we investigated the fatigue characteristic of connecting rod material for an automobile. Fatigue life is defined as the number of cyclic stress to failure by regular cyclic stress. Fatigue life of C70S6 specimen was obtained from 134,000 to 147,000 cycles. Fatigue limit showed 432MPa by normal fatigue test. The other hands, it was 96MPa in the case of fretting fatigue test. It was extremely lower than that of a normal fatigue test. From observation of fracture surface, it was confirmed that the fatigue crack was initiated at the boundary of a specimen and bridge pad.

• Journal of Korean Academy of Nursing
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• v.29 no.2
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• pp.248-257
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• 1999

The purpose of this study was to identify basic data for the health fare of normal pregnant women. The number of subjects was 779 pregnant women who received prenatal care in two University hospitals. The data, which were collected from June to October, 1998. and used the questionnaire “Symptom Table on Fatigue Perception” designed by the Research Committee of the Industial Fatigue in Hygienic. Association of Japan Industry. The collected data were scored by use of means and standard deviations according to the subjective symptoms of fatigue and each item as an independent variable was analysed by t-test and ANOVA test. The results are as follows : 1) Degree of subjective fatigue showed as an average of 1.81. Fatigue as physical symptoms had the highest score with 2.09. followed by neuro-sensory symptoms, 1.69 and psychological symptoms had the lowest score 1.66. 2) With the respect to the general characteristics of the subjects. there were statiscally significant difference in experience of pregnancy(t＝-2.286, p＝.023). wanted pregnancy(t＝-2.935, p＝.004), parity(t＝-2.429, p＝.015), sleeping time(F＝3.478, p＝.031). and presence of other child(t＝2.347, p＝0.19).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.707-712
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• 2008

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

• Journal of Korean Medicine Rehabilitation
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• v.28 no.2
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• pp.105-111
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• 2018

Objectives The purpose of this study was to examine the effects muscle fatigue at the knee muscles on balance during standing in healthy adults. Methods Thirty healthy adults were recruited along with their written informed consent. Subjects were randomly assigned to knee extensor group (fatigue on knee extensor, KE), and knee flexor group (fatigue on knee flexor, KF). And subjects performed exercise with each muscle group until muscle fatigue was induced. They were assessed balance ability by functional reaching test (FRT), limit of stability (LOS), and postural sway (one leg standing, normal eye open (NO), normal eye close (NC), pillow with eye open (FO), and pillow with eye close (FC)) before and after fatigue. Results There were significant group differences balance performances in FRT, anterior of limit of stability, one leg standing, and the muscle fatigue of knee muscles were decreased balance performances. The balance performance was affected by visual sense and proprioception. Conclusions These results show that the muscle fatigue of knee muscles decreased balance performance. Therefore, balance exercise program should be trained without muscle fatigue.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.1
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• pp.43-48
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• 2009

The fatigue crack growth behavior of high strength X80 pipeline steel was investigated with compact tension specimens that crack growth directions were aligned either parallel or normal to the rolling direction of the pipeline. Also, the fatigue crack growth rates for welded joint of X80 pipeline steel were investigated with compact tension specimens that crack growth directions were aligned either parallel or normal to the welding line. The experimental results indicated the fatigue crack growth behavior was markedly different in three zones, weld metal, heat affected zone and base metal of welded joints. There was a trend toward increment in the fatigue life of weld metal and heat affected zone as compared with the X80 pipeline steel.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.22 no.4
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• pp.387-397
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• 2015

Purpose: This study aimed to evaluate nutritional status and fatigue, and to identify the relationship between nutritional status and fatigue in gynecological cancer patients receiving chemotherapy. Methods: Participants were 106 outpatients who had uterine, ovary, or breast cancer and a descriptive cross-sectional design was used. Nutritional indicators including biochemical and anthropometric measures, the Subjective Global Assessment (SGA) scale, and the Piper's Revised Fatigue Scale were completed. Results: About thirty-nine percent of the patients were malnourished based on the SGA. Serum hemoglobin and total lymphocyte levels were less than the normal ranges, although anthropometrics were normal. The women experienced moderate fatigue with a mean score of $5.84{\pm}2.00$. Nutritional status was significantly different by age, education, employment status, and monthly income. The women also had different nutritional status and fatigue depending on the type of cancer and chemotherapy. Fatigue was significantly related to SGA scores, serum hemoglobin, triceps skinfold thickness and mid-arm muscle circumference. Conclusion: The results of this study highlight an urgent need to provide adequate nutritional support and fatigue management with individualized strategies for gynecological cancer patients on chemotherapy.

• Korean Journal of Applied Biomechanics
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• v.23 no.4
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• pp.335-345
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• 2013

The purpose of this study was to investigate the effects of foot type and ankle joint fatigue levels on the trajectories of center of pressure and center of mass during a single-leg stance. The study subjects included 24 healthy women (normal foot group, n=10; pronated foot group, n=14). Ankle joint muscle fatigue was induced by using an isokinetic dynamometer, where the fatigue levels were measured on plantar flexion and dorsiflexion at angular velocities of $30^{\circ}/s$ at 50% and 30% of the peak torque of ankle plantar flexion. Following assessments in the anteroposterior direction according to the level of fatigue, the pronated foot group showed decreased single-leg stance ability at 50% and 30% of the fatigue level. Moreover, the normal foot group showed better single-leg stance ability than the pronated foot group at 30% of the fatigue level. Following assessments in the mediolateral direction, we noted that the single-leg stance ability did not differ significantly according to the levels of fatigue or foot type. In conclusion, ankle plantar flexion at 50% and 30% of the peak torque reduced the ability of the pronated foot group to achieve a single leg stance in the anteroposterior direction. Moreover, the normal foot group showed better single-leg stance ability than the pronated foot group.