• Proceedings of the KSR Conference
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• 2011.05a
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• pp.277-282
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• 2011

Bogie frame is typical safety part of railway vehicle. Total serviceable life of bogie frame will be evaluated by Cumulative Damage Approach Method that is defined by dynamic strain measurement during revenue service under the actual track conditions. As a result of the standardization process developed in British Standard Institution, BS 7608 defines for fatigue design and test method of steel structure by fatigue test results over the long period. This paper evaluates the total serviceable life applying BS 7608 for the bogie frame of Electric Multiple Unit to verify structural safety of the bogie frame.

• Korean Journal of Psychosomatic Medicine
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• v.9 no.2
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• pp.164-173
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• 2001

Objectives : Fatigue is a common symptom in primary medical care and has nonspecific and highly subjective features. So it has been difficult to define and measure fatigue, especially those present without any organic diseases. This study was conducted to evaluate the validity of the Fatigue severity scale(FSS) in patients with persistent fatigue who were free of any organic diseases or psychiatric disorders of depression or anxiety. Methods : Subjects consisted of 45 controls, 44 fatigued patients and 43 psychiatric patients with depression or anxiety. They all completed the fatigue severity, modified Bepsi stress, and Hospital anxiety and depression scales. Chalder fatigue scale was administrated randomly in 30 of them. Data were analyzed for reliability and validity of the FSS. Results: Cronbach's a coeffient of FSS was 0.929, and the Pearson correlation coefficient for test-retest was 0.916(p<0.01). ANCOVA for discriminant validity revealed that there were significant differences in mean FSS values among the three groups. The fatigue group had significantly higher FSS value than the other two groups. The psychiatric group also had significantly higher FSS value than the control group. The Pearson correlation coefficient for convergent validity by comparing FSS with Chalder fatigue scale was 0.782(p<0.01). Using FSS index 3.22 as the cut-off point, sensitivity was 84.1% and specificity was 85.7% for the fatigue and control groups, respectively. Conclusion : Results suggested the clinical application of the FSS to be a useful measurement for distinguishing fatigue between patients with physiologic fatigue and psychiatric patients with depression or anxiety.

• Women's Health Nursing
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• v.6 no.3
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• pp.398-412
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• 2000

The purpose of this study was to identify a relationship between housework hours and fatigue level in middle-aged women. The subjects were 204 women living in Seoul and near the city, ranging in ages of 30-59(mean = 41.6 year) and were interviewed during the month of Oct. to Dec. 1999. The following questionnaires were utilized in this study: a self reporting housework time measurement table and a fatigue symptom scale originated from Yoshitake (1978). The analysis of the data was done by SAS program, t-test, ANOVA, and Pearson correlation. The results of this study were as follows : 1. Total mean hours of housework of the subjects were shown 9.2 hours on weekdays and 8.9 hours on weekend. Mean hours according to the area of houseworks on weekdays and on weekend were preparing and providing meal 3.9 and 4.2, doing laundry and maintaining clothes 3.1 and 1.6, keeping and maintaining house 1.6 and 1.4, caring family 1.3 and 1.2, and keeping household records 0.5 both. 2. With respect to the general characteristics of the subjects, there were significantly difference in age, job, religion, type of family, number of children, experience of present and previous illness, and perceived body size. 3. Average fatigue scores of the subjects were 16.6 of total score 60. Fatigue scores by the area were neuroperceptive fatigue 6.5, mental fatigue 5.2, and physical fatigue 4.9 in order. There were significantly differences in the score of fatigue by religion, number of family, present illness, and perception of body size. 4. There were significantly positive relationships in the scores of fatigue with the total hours of housework, preparing and providing meal, doing laundry and maintaining clothes, keeping and maintaining house, and caring family. 5. The physical fatigue scores were positively related with the areas of preparing and providing meal, doing laundry and maintaining clothes. While the mental fatigue scores were positively related the areas of preparing and providing meal, caring family, and keeping and maintaining house, and neuroperceptive fatigue scores were positively related with the areas of keeping and maintaining house and caring family. The recommendations from this study were further studies to investigate how middle-aged women manage their fatigue level, increase public awareness of middle aged women's fatigue level, and develop programs for middle-aged women to help with high fatigue.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.195-202
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• 2000

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.673-680
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• 2003

This study verified the relationship between fracture mechanics parameters(ΔK, ΔK$\sub$eff/, K$\sub$max/) and X-ray parameters (${\alpha}$$\sub$r/, B) for SG365 steel at elevated temperature up to 300$^{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase low ΔK region, reach to a maximum value at a certain value of K$\sub$max/ or ΔK and then decrease. Residual stress were independent on stress ratio by arrangement of ΔK and half value breadth were independent by the arrangement of K$\sub$max/. The equation of ${\alpha}$$\sub$r/ - ΔK was established by the experimental data. Therefore, tincture mechanics parameters could be estimated by the measurement of X-ray parameters.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.54-58
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• 2002

This study investigates a relationship between fracture mechanics parameters (Stress Intensity Factor Range: ΔK, Maximum Stress Intensity Factor; Kmax) and X-ray parameters (residual stress:$\sigma$r half-value breadth: B) for SG365 steel at elevated temperature up to 30$0^{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to the direction of crack length was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase at low ΔK region, to reach a maximum value at a certain value of Kmax or ΔK and then to decrease. Residual stress was independent of stress ratio by arrangement of ΔK and half value breadth were independent of the arrangement of Kmax. The equation of $\sigma$r-ΔK was established by the experimental data. therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.344-351
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• 2006

The fatigue of back muscle in the repetitive lifting motion was studied using multiple parameters(FFT_MDF, RMS, 2C, NT) in this study. Recent developments in the time-frequency analysis procedures to compute the IMDF(instantaneous median frequency) were utilized to overcome the nonstationarity of EMG signal using Cohen-Posch distribution. But the above method has a lot of computation time because of its complexity. So, in this study, FFT_MDF(median frequency estimation based on FFT) algorithm was used for median frequency estimation of back muscle EMG signal during muscle work in uniform velocity portion of lumbar movement. The analysis period of EMG signal was determined by using the run test and lumbar movement angle in dynamic task, such as lifting. Results showed that FFT_MDF algorithm is well suited for the estimation of back muscle fatigue from the view point of computation time. The negative slope of a regression line fitted to the median frequency values of back muscle EMG signal was taken as an indication of muscle fatigue. The slope of muscle fatigueness with FFT_MDF method shows the similarity of 77.8% comparing with CP_MDF(median frequency estimation based on Cohen Posch distribution) method.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.317-323
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• 2001

This study verified the relationship between fracture mechanics parameters$({\Delta}K,\;{\Delta}K_{eff},\;K_{max})$ and X-ray parameters $(\sigma_r,\;B)$ for SG365 steel at elevated temperature up to $300^{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase low ${\Delta}K$ region, reach to a maximum value at a certain value of $K_{max}\;or\;{\Delta}K$ and then decrease. Residual stress were independent on stress ratio by arrangement of ${\Delta}K$ and half value breadth were independent by the arrangement of $K_{max}$. The equation of $\sigma_r-{\Delta}K$ was established by the experimental data. Therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.240-244
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• 2017

Experimental verification in the rig test stage for component development is a vital link between the aeromechanical design and structural integrity validation process. Based on this premise, Non-Intrusive Stress Measuring System was adopted on the axial compressor test rig to measure the static and dynamic tip deflection of all blades by using tip-timing sensors. Through analyzing vibration characteristics, we evaluated the vibratory stresses seen on the blades fatigue critical location; detected synchronous resonances which are the source of High Cycle Fatigue (HCF) in blades; presented non-synchronous vibration response by aerodynamic excitation and individual blade mis-tuning patterns.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.938-946
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• 1989

Using the CT specimen of carbon steel(SM45C), we estimated the fatigue crack propagation behavior in stable crack propagation range. Furthermore the fatigue crack propagation rate, Acoustic Emission(AE) count rate, and fractography characteristics were also compared among others. The following results were confirmed by experimental observation. Near-threshold stress intensity factor range(.DELTA. $K_{th}$) is influenced by stress ratio but not at the upper limit of stable crack propagation range. As stress intensity factor range(.DELTA.K) and(or) stress amplitude increase (s), both crack propagation rate(da/dN) and AE count rate(dn/dN) increase. Effective stress intensity factor range(.DELTA. $K_{off}$) determined from the crack closure point measurement by AE method is useful for the evaluation of fatigue crack propagation rate. Fractography in stable crack propagation range showed striation, and agreed with the crack propagation rate obtained either by experiment of by the results of microscopic measurements.s.