• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1181-1185
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• 1990

A failure evaluation diagram to evaluate fatigue fracture was developed. The relation between the fatigue limit and the threshold stress intensity factor for the short-cracked specimens of various materials including a piping carbon steel can be rationally predicted by the proposed method. It is shown that the coupled failure evaluation diagram for fatigue and ductile fracture is expecially useful for evaluation of the flaw tolerance as well as the margin of the safety of the pressure vessel and piping. Further, accumulation of fatigue data will be needed to construct an accurate fatigue failure evaluation diagram.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.733-738
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• 2002

In this study, contact fatigue in wheel-rail contact is simulated. It is necessary to calculate contact stress and subsurface stresses accurately to predict fatigue behavior. Contact stresses are obtained by contact analysis of semi-infinite solid based on influence function and subsurface stress field obtained by using rectangular patch solutions. Based on these stress values, several multiaxial high-cycle fatigue criteria are used and the critical loads corresponding to fatigue limits are calculated. The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when friction coefficient exceeds a specific value for all of three fatigue criteria.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.832-842
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• 1996

Fatigue life prediction and fatigue behavior of circular notched carbon fiber reinforced plastic laminates are presented. Point and average stress criteria by Whitney and Nuismer are generalized to fatigue fracture criteria for notched laminates. Residual strength degradation model and the assumptions on the stress redistribution are introduced during the derivation of prediction equations. S-N curve, Basquin's relation, and H and H's FLPE1 are chosen for evaluation of residual strength of unnotched laminates and six prediction equations are derived. Experiments are performed using Graphite/Epoxy laminates whose fiber orientation is $[0$^\circ$/+45$^\circ$/-45$^\circ$/90$^\circ$]s. Presented prediction equations are reasonably close to experimental data and proposed appoach is found to be suitable to predict fatigue life of notched composite laminates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.241-249
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• 2003

The service life of steel bridges can be assured only when their strength, serviceability and fatigue safety are fulfilled. However, at the present time, the continuous research for fatigue of steel bridges is desperately required since not much research work has been done so far. In this study, a guideline on the fatigue design is suggested for the practical purpose in order to establish the long-term safety of steel bridges against fatigue. The continuous steel truss bridge was analyzed for the cumulative reversals of the actual traffic, stress ranges and fatigue strength. From the results, the domestic fatigue design procedure was found to be fairly overestimated in comparison to the design code of other foreign countries. Therefore, it is necessary to review the current fatigue design specifications and have the new and rationalized design criteria in the future domestic fatigue design guidance.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.146-154
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• 2010

In this study the experimental results of fatigue specimen for the Strand Stay Cable Assembly of Extadosed bridges is investigated. The fatigue test and tensile experiment is conducted to 6 kinds of specimens. Test specimen OVM250-31 Strand Cable System manufactured by china OVM B-Machinery Co., Ltd, and OVM250-42 Parallel Strand Stay Cable Assembly manufactured by china OVM B-Machinery Co., Ltd, are passed for fatigue test and rupture tensile test. But Test specimen OVM250-42 Parallel Strand Stay Cable Assembly manufactured by korean A-Machinery Co., Ltd, is not passed for fatigue test conducted according to the "Recommendation for Stay Cable Design. The test result are compared to the fatigue criteria of PHI 2001 for cyclic load, and it is concluded that the current korean design code will be needed for representing the fatigue load in Hot Dip Galvanized Strand Stay Cable. It is verified that the new korean specification and quality criteria of Strand Stay Cable and exact experimental applied process will be needed.

• The Journal of Korean Medicine
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• v.33 no.2
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• pp.25-33
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• 2012

Objectives: To obtain the features of prevalence of chronic fatigue and chronic fatigue syndrome worldwide. Methods: All research reports for prevalence of chronic fatigue and chronic fatigue syndrome were selected from PubMed, KMbase and KISS database, and the prevalence were analyzed according to the symptoms and countries. Results: A total of 39 articles from 13 other countries and 4 articles from Korea met the criteria of this study. The prevalence of chronic fatigue and chronic fatigue syndrome was about 10% and 1% respectively. The prevalence for Korean was 17.7% and 1.4% respectively, however the data have a limitation due to the lack of well-designed studies. Conclusions: This report can provide essential information to build a strategy for development of therapeutics against chronic fatigue and chronic fatigue syndrome using traditional Korean medicine.

• Nuclear Engineering and Technology
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• v.45 no.1
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• pp.99-106
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• 2013

Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

• 한국기계연구소 소보
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• v.4 no.1
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• pp.19-26
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• 1981

Fatigue, the birth and growth of cracks in metal parts subjected to repeated loading, has been a problem plaguing engineers since the Industrial Revolution and the advent of rotating or reciprocating machinery. Designing against metal fatigue was studied briefly in several aspects. Examples of fatigue failures were shown. Fatigue was classified by loading: uniaxial Fatigue, multiaxial fatigue, cumulative fatigue da¬mage. Fatigue design criteria were discussed: Infinite-Life Design, Safe-Life Design, Fail-Safe Design, and Damage Tolerant Design. Mitigation of notch effects by design, improvement of fatigue strength of metal parts by residual stress and surface finishing were discussed. Relative fatigue beha¬vior was studied under various environmantal conditions. Especially the effects of corrosion, temperature, fretting, and irradiation were covered.

• The Journal of Pediatrics of Korean Medicine
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• v.31 no.3
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• pp.1-13
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• 2017

Objectives The purpose of this study is to investigate how irritable bowel syndrome (IBS) affects fatigue scales and eating habits in children and adolescents using Rome IV criteria. Methods Questionnaires and The $PedsQL^{TM}$ Multidimensional Fatigue Scale (MFS) have been given to 211 children and adolescents aged 8 to 18 years old who were admitted to ${\bigcirc}{\bigcirc}$ university Korean medicine hospital pediatric departments, from 29th, July, 2016 to 12th, August, 2016 to evaluate their eating habits and fatigue. Additionally, PASW statistics 18.0 were used to analyze influence of irritable bowel syndrome on eating habits and fatigue in children and adolescents by using chi-square test, independent t-test and linear regression. Results In total of 211 subjects, 29 (13.7%) were diagnosed with IBS according to the Rome IV criteria. 1. There was a statistically significant difference (p<0.05) between IBS group and non-IBS group on a specific question in the eating habit questionnaire: the amount of sugar intake and the prevalence of IBS. 2. There was a statistically significant difference in general fatigue and cognitive fatigue categories when comparing the MFS subscores according to the prevalence of IBS. Conclusions Considering patients eating habits and fatigue is a necessary process for the successful treatment of irritable bowel syndrome. Korean medicine that maximizes quality of life while minimizing the potential risks to the patients of gastrointestinal disease should also include administrative interventions that may be helpful in the daily life of IBS patients.

• The Journal of Korean Medicine
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• v.30 no.6
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• pp.80-85
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• 2009

Objective: This study aimed to build an overview of randomized clinical controlled trials (RCTs) for chronic fatigue-related symptoms to extract the useful data for management of patients and development of therapeutics using Korean traditional medicine in the future. Methods: All RCT-derived papers for chronic fatigue-related symptoms were collected via PubMed Database. We surveyed elementary information of RCTs such as clinical question, study design, and its quality and results. Results: A total of fifty-three RCTs met these review criteria. Most of the RCTs were performed in Western countries, particularly the UK and USA. The major portion of RCTs focused on chronic fatigue syndrome using immune modulators, psychotherapeutic and anti-depressants. Five RCTs using complementary and alternative medicine, including herbal remedies, showed positive results. Conclusions: Fatigue-related symptoms are a main target of Oriental medicine. This study provides helpful information for planning clinical study of chronic fatigue-related symptoms using traditional Korean medicine.