• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.528-532
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• 2013

In this study, an analytical model of micro-beam structure including thermoelastic damping with irregularly distributed masses is investigated. The significance of thermoelastic damping for micro-scale mechanical resonators is evaluated to design -with high quality factor(Q-factor). The beam model of this work is based on Euler-Bernoulli beam theory. In order to determine the natural frequency of the model, energy method is applied. Also, the thermoelatic damping effects are considered by using heat conduction equations, and the Q-factor can be determined. To derive the equation of motion, non-dimensionalization is employed for systematic analysis. Results of the model are verified, and present mode shapes and Q-factors for the micro-beam with thermoelastic damping including random point masses.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.1
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• pp.117-124
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• 2015

This study explored the determinant variables of physical health of the high school students in Korea. Specifically, it explored how the sociodemographic characteristics factor, school factor, delinquent behaviors factor of the students affect their physical health using the 2012 Korean Youth Health Risk Behavior On-line Survey. Using the case of 36,889, this study conducted frequency analysis, t-test, F-test, and multiple regression analysis. As the result of total multiple regression analysis, gender, father's educational level, sibling(s), economic status, grade, academic record, problem drinking, drug use were statistically significant determinant variables of physical health of the high school students in Korea. Also, it delivered some implications for enhancing their physical health.

• Journal of Nutrition and Health
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• v.34 no.1
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• pp.89-97
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• 2001

The relationship among food behavior, psychological factor(life strees) and perceive tiredness was investigated in 514 adolescents. Tiredness was measured in four cases: in lessons, before school, in the early evening and at weekends. Adolescents felt most tired in lessons and before school, and leat at weekends. Irregularity of meal times and skipping breakfast were positively correlated with tiredness in lessons and befor school. Consumption of some foods was related to perceived tiredness. High sugar or fat containing ice-cream, hamburger of fizzy drinks in boys, and crisps and cookies in girls were positively associated with tiredness. Whereas beans and mushrooms were negatively associated with tiredness in girls. Life stress(by scholastic problem and personal problem) of adolescents was positively related to tiredness. The contribution of stress to tiredness was much greater than of food behavior according to multiple linear regression .There was no relationship between nutrients intake and tiredness in lessons and before school which were more strongly influenced by stress, whereas the relationship was found at weekend without influences of stress. The more tired, the lower NARs(nutrient adequacy ratio) of energy, phosphorus, vitamin A, vitamin B$_2$, and niacin were. In conclusion, some eating behavior and psychological factor can cause tiredness in adolescents, but tiredness in school and before school had more of a psychological cause than at weekend. (Korean J Nutrition 34(1):89-97, 2001)

• Journal of Korean Public Health Nursing
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• v.17 no.1
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• pp.113-121
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• 2003

Purpose : This study was performed to develop a scale of outdoor school safety behavior in Korean elementary students. Methods : A list of 40 items were selected by priori experiences of school health teachers and a literature review. For evaluation of the appropriateness of the 32 items, questionnaires were reviewed by an expert group which was consisted of 10 professionals. Validity of the 31 items was screened in this process with 4 point Likert scale. Using the preliminary tool. data were collected from 684 subjects for item analysis and factor analysis. A total of 26 items were remained, and items with the lower than 0.2 item-total correlation coefficient were removed. Factor analysis was done with these 26 items, and 26 items with factor loadings higher or equal to 0.4 were remained. Relsult : 1. Cronbach's alpha for the 26 items was 0.70 2. Five factors were identified with eigen value 1.0 These contributed $51.617\%$ of the variance in the total score. 3. Each factor was labled 'vonobserbance of safety rule', 'good habit for safety', 'careless action', 'lack of safety knowledge', 'injurious action to friend' It is suggested that this scale could be used to measure outdoor school safety behaviors among elementary students in Korea.

• Computers and Concrete
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• v.30 no.5
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• pp.323-337
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• 2022

This paper proposes a numerical model to simulate the rotational behavior of steel fiber in fresh cement-based materials in the presence of a magnetic field. The results indicate that as the aspect ratio of fiber increases, the required minimum magnetic field intensity to make fiber rotate in viscous fluid increases. The optimal magnetic field intensity is 0.03 T for aligning steel fiber in fresh cement-based materials to ensure that the applying time of the magnetic field can be conducted concurrently with the vibrating process to increase the aligning efficiency. The orientation factor of steel fiber in cement mortar can exceed 0.85 after aligning by 0.03 T of the uniform magnetic field. When the initial angle of the fiber to the magnetic field direction is less than 10°, the magnetic field less than 0.03 T cannot make the fiber overcome the yield stress of fluid to rotate. The coarse aggregate in steel fiber-reinforced concrete is detrimental to the rotation and alignment of the steel fiber. But the orientation factor of ASFRC under the 0.03T of the magnetic field can also exceed 0.8, while the orientation factor of SFRC without magnetic field application is around 0.6.

• BMB Reports
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• v.45 no.6
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• pp.348-353
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• 2012

L-2-Oxothiazolidine-4-carboxylic acid (OTC) is a cysteine prodrug that maintains glutathione in tissues. The present study was designed to investigate anti-fibrotic and anti-oxidative effects of OTC via modulation of nuclear factor erythroid 2-related factor 2 (Nrf2) in an in vivo thioacetamide (TAA)-induced hepatic fibrosis model. Treatment with OTC (80 or 160 mg/kg) improved serum liver function parameters and significantly ameliorated liver fibrosis. The OTC treatment groups exhibited significantly lower expression of ${\alpha}$-smooth muscle actin, transforming growth factor-${\beta}1$, and collagen ${\alpha}1$ mRNA than that in the TAA model group. Furthermore, the OTC treatment groups showed a significant decrease in hepatic malondialdehyde level compared to that in the TAA model group. Nrf2 and heme oxygenase-1 expression increased significantly in the OTC treatment groups compared with that in the TAA model group. Taken together, these results suggest that OTC restores the anti-oxidative system by upregulating Nrf2; thus, ameliorating liver injury and a fibrotic reaction.

• Asia-Pacific Journal of Business
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• v.15 no.1
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• pp.1-14
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• 2024

Purpose - We investigate whether a potential missing pricing factor plays a significant role in the idiosyncratic volatility puzzle. Design/methodology/approach - We theoretically show how a missing pricing factor can affect the idiosyncratic volatility puzzle, and also show how to get around the problem empirically. We adopt the Fama-French five factor model for the estimation of the idiosyncratic risk and use randomly constructed portfolios as test assets. Findings - We find that a missing factor does not drive the idiosyncratic volatility puzzle. Thus, we conclude that the idiosyncratic volatility does affect the risk premium of its stock. Research implications or Originality - The Fama-French five factor model does a pretty good job in explaining the risk premiums of stocks, and it can be used to reliably estimate idiosyncratic risk of stocks.

• Steel and Composite Structures
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• v.28 no.2
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• pp.209-221
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• 2018

An empirical and efficient method is presented for calculating the dynamic increase factor to amplify the applied loads on the affected bays of a steel frame structure with semi-rigid connections. The nonlinear static alternate path analysis is used to evaluate the dynamic responses. First, the polynomial models of the extended end plate and the top and seat connection are modified, and the proposed polynomial model of the flush end plate connection shows good agreement as compared with experimental results. Next, a beam model with nonlinear spring elements and plastic hinges is utilized to incorporate the combined effect of connection flexibility and material nonlinearity. A new step-by-step analysis procedure is established to obtain quickly the dynamic increase factor based on a combination of the pushdown analysis and nonlinear dynamic analysis. Finally, the modified dynamic increase factor equation, defined as a function of the maximum ratio value of energy demand to energy capacity of an affected beam, is derived by curve fitting data points generated by the different analysis cases with different column removal scenarios and five types of semi-rigid connections.

• Journal of the Korean Society of School Health
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• v.23 no.2
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• pp.286-295
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• 2010

Purpose: This study was conducted to identify the factors affecting the job stress of school nurses and reducing their the job stress by analyzing degree of the stress according to the factors related to job stress. Methods: The participants were 136 school nurses who worked in Pusan province. The Data were collected by self-reporting questionnaires from Dec. 11th in 2006 to Feb. 9th in 2007. The data were analyzed by Frequency, Mean, t-test, ANOVA, Pearson Correlation Coefficient and Stepwise multiple regression analysis (SPSSwin 12.0s). Results: There was significant difference of the degree of job stress in age. There was significantly negative relationship between the job characteristics and job stress (r=-.473), job satisfaction and job stress (r=-.561), personal values and job stress (r=-.429), achievement motivation and job stress (r=-.215) at p<.01 level. The major factor which influence the degree of job stress was job satisfaction. Conclusion: The factors affecting the job stress of school nurses was correlated with one another and influenced to the degree of the job stress directly and indirectly. The factor that affected the degree of the job stress directly was the job satisfaction and the personal values. As shown this result, it is important that the factor of the job stress lies in the mental characteristics.

• Biomolecules & Therapeutics
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• v.25 no.4
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• pp.427-433
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• 2017

Previously, we demonstrated that galangin (3,5,7-trihydroxyflavone) protects human keratinocytes against ultraviolet B (UVB)-induced oxidative damage. In this study, we investigated the effect of galangin on induction of antioxidant enzymes involved in synthesis of reduced glutathione (GSH), and investigated the associated upstream signaling cascades. By activating nuclear factor-erythroid 2-related factor (Nrf2), galangin treatment significantly increased expression of glutamate-cysteine ligase catalytic subunit (GCLC) and glutathione synthetase (GSS). This activation of Nrf2 depended on extracellular signal-regulated kinases (ERKs) and protein kinase B (AKT) signaling. Inhibition of GSH in galangin-treated cells attenuated the protective effect of galangin against the deleterious effects of UVB. Our results reveal that galangin protects human keratinocytes by activating ERK/AKT-Nrf2, leading to elevated expression of GSH-synthesizing enzymes.