• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.214-221
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• 2003

In this study, based on the effect of the interaction of fracture mechanics by graphite and fatigue limit phenomena of the microscopic observation various matrix structure, spheroidal ratio, size of graphite and distribution etc. parameters containd with Ductile Cast Iron. Therefore, in this study, different ferrite-pearlite matrix structure and spheroidal ratio of graphite of 70%, 80% and 90%, GCD40, GCD45-1 and GCD45-2 series and three different ferrite-pearlite matrix structure, GCD 45-3, GCD 50, GCD 60 series, all of which contain more than 90% spheroidal ratio of graphite, were used to obtain the correlation between mean size of spheroidal graphite and fatigue strength. (1) 73% pearlite structure had the highest fatigue limitation while 36% pearlite structure had the lowest fatigue limitation among ferrite-pearlite matrix. the increase in spheroidal ratio with increasing fatigue limitation, 90% had the highest, 14.3% increasing more then 10%, distribution range of fatigue life was small in same stress level. (2) (equation omitted) of graphite can be used to predict fatigue limit of Ductile Cast Iron. The Statistical distribution of extreme values of (equation omitted) may be used as a guideline for the control of inclusion size in the steelmaking processes.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.924-932
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• 2010

War field differs from conventional military education and training environments. Warfighter may confront frequently unexpected physical and psychological stimulation. Cumulative psychological stress and physical fatigue can be causes of mood distortion, declined alertness, and decreased combat capability in warfighters. Countermeasures of combat stress and fatigue is very important for keeping combat capability and saving of life. Here in, the countermeasures of combat stress and fatigue have reviewed, and limitation and the direction of research and development of countermeasures of combat stress and fatigue are proposed.

• Journal of Korean Academy of Nursing
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• v.35 no.7
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• pp.1353-1361
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• 2005

Purpose: This study was done to provide fundamental data for developing a depression prediction model by discovering main factors that affect depression in patients who do maintenance hemodialysis. Method: The subjects were 191 patients doing maintenance hemodialysis selected from outpatient dialysis clinics at 9 major general hospitals, The Instrument tools utilized in this study were adapted from depression, fatigue, sleep disturbance, stress, adaptation, symptoms, daily activities, and role limitation and thoroughly modified to verify reliability and validity. The collected data was analyzed with a SPSS-PC 11.0 Window Statistics Program for real numbers, percentage, average, standard deviation, and multiple regression. Results: The correlation factor for depression was (M=2.54) fatigue(M=3.12), sleep disturbance (M=2.82), stress(M=3.04), adaptation(M=2.53), daily activities(M=2.24), symptoms(M=2.37), and role limitation(M=2.24). The strongest factor that affected depression was explained by symptoms of the patients who performed hemodialysis. The analysis of the factors that affected depression revealed a $58.4\%$ prediction in symptoms, stress, role limitation, and adaptation. Conclusion: It has been confirmed that the regression equation model(Depression=7.351 + .266$^{\ast}$symptoms + .260$^{\ast}$stress -.l89$^{\ast}$adaptation + .057$^{\ast}$fatigue) of this research may serve as a prediction factor for depression in Hemodialysis Patients.

• Journal of the military operations research society of Korea
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• v.24 no.1
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• pp.41-57
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• 1998

Since the aircraft has a property of moving in the three-dimensional space, it may cause personally and financially critical damage in the case of an accident. Among the causes of aircraft accident, human factor has occupied about 70% of all accidents. Specially, fatigue among human's problems has been studied earlier than any other factor. Fatigue has been the cause of 75% of accidents that are related to human factor. So many studies have been conducted. But the direction of these studies mainly attach importance to the sleep loss and circadian rhythm. Limitation for flight time of ICAO is 8 hours per day, civil airlines in domestic line also adopt the limitation. But this rule is not based on human's performance but compromise between labor and management. The long-haul flight brings about a mental block to pilot. This mental block decreases performance of pilot and loses a lot of important information. So this may cause many accidents. This paper is to offer optimal flight time according to the amount of fatigue due to increasing flight time. The optimal flight time is searched through the field experiment. The experiment has adopted two methods. One is to examine pilot's objective fatigue accumulation rate through the critical fusion frequency, and another is to investigate pilot's subjective fatigue feeling through the fatigue subjective symptoms investigation table.

• 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.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.315-320
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• 2006

This paper describes stress analysis and fatigue limit evaluation of plate with V-notch and hole-notch by lock-in infrared thermography. Temperature variation of a specimen under cyclic loading is negatively proportional to the sum of principle stress change and the surface temperature measured by infrared camera is calculated to the stress of notch specimens, based on thermoelastic equation. And also, fatigue limitation can be evaluated by the change of intrinsic energy dissipation. Fatigue limitation of two notch specimens is evaluated as 164 MPa and 185 MPa, respectively and the stress measured by Lock-in infrared Thermography show good agreement within 10% error.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3837-3851
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• 2021

To investigate how the fabrication and repair of socket welded joints could be used to enhance fatigue resistance under vibration condition, experimental test data of installation conditions that potentially influence fatigue strength were analyzed with the S-N curve. It was found that the decreasing fatigue strength of stainless steel socket welded joints was attributed to the effect of high heat input of welding process. The effect of welding method, slip-on gap and radial-gap conditions on fatigue strength was insignificant. The test data of repair technique application, 2 × 1 leg length and of socket weld overlay, clearly showed higher fatigue strength but there was a limitation for higher stress region because of the weld toe crack.

• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.21-27
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• 2005

Large welded structures, including ships and offshore structures, are normally in operation under cyclic fatigue loadings. These structures include many geometric discontinuities, as well as material discontinuities due to weld joints. The fatigue strength at these hot spots is very important for the structural performance. In the past, various Non Destructive Evaluation (NDE) techniques have been developed to detect fatigue cracks and to estimate their location and size. However, an important limitation of most of the existing NDE methods is that they are off line; the normal operation of the structure has to be interrupted, and the device often has to be disassembled. This study explores the development of a structural health monitoring system, with a special interest in applying the technique to welded structural members in ship and offshore structures. In particular, the impedance based structural health monitoring technique that employs the coupling effect of piezoceramic (PZT) materials and structures is investigated.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.94-100
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• 2004

A dynamic finite element analysis of a rig test model for truck chassis systems is conducted to establish an appropriate model designed to predict the fatigue life. A reference Belgian road input, which has been obtained from a field test, is imposed on the finite element model in the modal finite element analysis, and the resulting strain history is employed for the prediction of the fatigue life. This is compared with the prediction based upon the strain history measured in the field test. The two agree with each other within the limitation of the field data and the input data to the model. The high frequency responses over 50 Hz are confirmed to be negligible as far as their effect on the fatigue life is concerned.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.4
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• pp.44-50
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• 2011

Turbulent mixing of hot and cold coolants is one of the possible causes of high cycle thermal fatigue in piping systems of nuclear power plants. A typical situation for such mixing appears in turbulent flow through a T-junction. Since the high cycle thermal fatigue caused by thermal striping was not considered in the piping fatigue design in several nuclear power plants, it is very important to evaluate the effect of thermal striping on the integrity of mixing tees. In the present work, before conducting detailed evaluation, three thermal striping evaluation methodology suggested by EPRI, JSME and NESC are analyzed. Then, a by-pass pipe connected to the shutdown cooling system heat exchanger is investigated by using these evaluation methodology. Consequently, the resulting thermal stresses and the fatigue life of the mixing tee are reviewed and compared to each other. Futhermore, the limitation of each methodology are also presented in this paper.