• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.130-136
• /
• 2003

A FQI(fatigue quality index) analysis using the concept of SF(severity factor) is performed to various shape of elliptical hole. FQI is fatigue quality index to estimate the dynamic SF from static SF by finite element analysis. Since the SF is affected by the location of cutout in plate and radius ratio, static SF is analyzed with finite element method and forms the equation of FQI for predicting a dynamic SF. To examine the validity, dynamic SF is measured by photoelastics and thermalelastics for an epoxy resin plate with various elliptical holes under dynamic load.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.2
• /
• pp.75-84
• /
• 2018

In this study, the analysis of torrefaction products was carried out for fueling of sewage sludge. The mixed samples were composed as follows : 50% of sewage sludge and 50% of rice husk and CR(Coffee Residue). In this experiment, the reaction time(30min, 60min) and temperature($200^{\circ}C$, $250^{\circ}C$, $300^{\circ}C$) were expressed as a single variable using SF(Severity Factor). As a result, it was confirmed that as the SF increased, the heating value and fuel ratio increased, but the CI(Combustibility Index) decreased. The heating value was similarly increased as CR(Coffee Residue) and SF increased. The fuel ratio range of mixed samples was equal to that of lignite(0.5~1.0) in case of SF lower than 6.19 and that of bituminous coal(1.0~1.8) in case of SF higher than 7.36 or above. The CI showed a stable range(3,000~5,500kcal/kg) in low SF as the content of mixed samples contained more rice husk than CR.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.5
• /
• pp.90-95
• /
• 2005

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints with various shapes of cutouts. It is important to study these connected structures under dynamic forces for evaluation of stress concentration. In this paper, a FQI(fatigue quality index) analysis using the concept of SF(severity factor) is performed to various shape of elliptical hole. The SF is affected by the location of cutout in plate and radius ratio, static SF is analyzed with finite element analysis and the equation of FQI for predicting a dynamic SF is formed.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.6
• /
• pp.497-506
• /
• 2013

The optimal condition for the torrefaction of eucalyptus (Eucalyptus globulus) was investigated by response surface methodology. The carbon content in the torrefied biomass increased with the severity factor (SF), while hydrogen and oxygen contents decreased. The calorific value of torrefied biomass ranged from 20.23 to 21.29 MJ/kg, depending on the torrefaction conditions. This implied that the energy contained in the torrefied biomass increased by 1.6 to 6.9%, when compared with that of the untreated biomass. The weight loss of biomass increased as the SF increased. The Code level of reaction temperature had the highest impact on the energy yield of torrefied biomass, while the effect of Code level of reaction time was considerably low. The highest energy yield was obtained at low SF.

• Korean Journal of Biological Psychiatry
• /
• v.20 no.1
• /
• pp.6-11
• /
• 2013

Objectives There are only a limited number of studies on instruments assessing fatigue in university students, although fatigue exerts negative influences on their health and academic performances and fatigue-related complaints are more frequently reported in young adults than middle-aged adults. The aim of this study was to validate the 9-item Fatigue Severity Scale (FSS) among university students including both undergraduate and graduate students in South Korea. Methods A total of 176 university students completed a battery of self-report questionnaires, including the FSS, the Brief Fatigue Inventory (BFI), the Beck Depression Inventory-II (BDI-II), the Beck Anxiety Inventory (BAI), the Medical Outcomes Study Short Form 36 version 2 (MOS-SF36v2), and the Inclusion of Community in the Self Scale (ICS). The data were collected from February of 2012 to June of 2012. The reliability, convergent validity, divergent validity, and exploratory factor analyses were conducted to assess psychometric properties of the FSS. Results The mean FSS score was 3.20 (standard deviation = 1.43). The FSS demonstrated an excellent internal consistency (Cronbach's ${\alpha}$ = 0.93) and item-total correlations ranged from 0.56 to 0.90. Correlations of the FSS with the BFI (r = 0.71, p < 0.01), BDI-II (r = 0.54, p < 0.01), BAI (r = 0.46, p < 0.01), MOS-SF36v2 physical component summary (r = -0.28, p < 0.01), MOS-SF36v2 mental component summary (r = -0.55, p < 0.01), and ICS (Spearman's rho = -0.07, p = 0.33) showed acceptable convergent and divergent validity. Exploratory factor analysis defined one underlying factor (eigenvalue = 5.67) that explained 93.50% of the total variance. Conclusions To the best of our knowledge, this is the first study to investigate reliability and validity of the FSS in university students. The FSS exhibits good psychometric properties for evaluation of fatigue among university students in South Korea. Since the FSS is easy to administer, score, and interpret, it could be a useful tool in research and practice for assessing fatigue among university students.

• Sleep Medicine and Psychophysiology
• /
• v.14 no.2
• /
• pp.99-106
• /
• 2007

Objective: Restless legs syndrome (RLS) is known to be associated with chronic renal failure (CRF) patients on hemodialysis, however the prevalence of RLS in CRF patients on hemodialysis is variable due to different diagnostic criteria or dialysis technique. A few reports have indicated the association between RLS symptom and lower life quality in CRF patients on hemodialysis. This study aims to investigate the prevalence of RLS and its association with the quality of life in CRF patients of a single dialysis unit in Korea. Methods: A total of 83 Korean CRF patients on hemodialysis in the Korea University Hospital were examined. International Restless Legs Syndrome Study Group (IRLSSG) criteria and International Restless Legs Scale (IRLS) were used to determine the diagnosis and severity of RLS. Questionnaires including Athens Insomnia Scale (AIS), Epworth sleepiness scale (ESS), and Medical Outcome Study Form-36 (SF-36) were administered to all the patients for the assessment of sleep and quality of life. Hamilton Depression Rating Scale (HDRS) and Clinical Global Impression (CGI) were also measured for depression and status of mental illness by psychiatrist. Results: Of the 83 patients, 31 (37.3%) patients were found to have RLS and 43 (51.8%) patients met at least one of the RLS diagnostic criteria. The AIS (t=2.40, p=0.019), ESS (t=2.41, p=0.018), HDRS (t=3.85, p<0.001) and CGI (t=3.52, p=0.001) were higher in the subjects with RLS compared to other subjects. The SF-36 scores were significantly lower in the patients with RLS except physical functioning and bodily pain. Total (p=0.005), physical component (p=0.019), and mental component scores (p=0.019) of SF-36 were significantly lower in patients with more severe RLS symptoms. Conclusion: There was significant relationship between RLS and poor quality of sleep and life. More severe RLS symptom was proven to be an important factor to make a quality of life worsen.