• Proceedings of the KSR Conference
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• 2010.06a
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• Journal of Korean Public Health Nursing
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• v.31 no.3
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• pp.518-527
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• 2017

Purpose: This study examined the relationship among stressful life events, mindfulness and depression, and explored the mediating role of mindfulness between stressful life events and depression in nursing students. Methods: A cross-sectional survey was undertaken. A sample of 120 nursing students participated in the study. The self-reported measures of stressful life events (revised life stress scale), depression (DASS-D) and mindfulness (MAAS) were adopted in April, 2017. The data were analyzed using descriptive statistics, frequency, Pearson correlation coefficient and multiple regression. Mediation analysis was performed using the Baron & Kenny method and Sobel test. Results: The mean scores of stressful life events, mindfulness and depression were 39.50, 77.03, and 8.18, respectively. Higher levels of stressful life events were associated with lower mindfulness (r = -46, p < .001) and higher depression (r = -44, p < .001), and mindfulness was negatively associated with depression (r = -72, p < .001). Mindfulness showed full mediation in the relationship between stressful life events and depression. Conclusion: Stressful life events influenced the nursing students' depression via the full mediating effect of mindfulness. Promoting mindfulness plays an important role in reducing depression in nursing students. Therefore, it is important to develop a mindfulness program or use a mindfulness-based stress reduction program (MBSR) for nursing students.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.20 no.3
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• pp.259-268
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• 2013

Purpose: The purpose of this study was to identify factors influencing job satisfaction among nurses working in college health centers in order to enhance their role functions and to increase their work capabilities. Method: In this study a cross-sectional survey was used to collect data from 106 nurses working in college health centers. Collected data were analyzed using frequency, Pearson correlation coefficients, independent t-test, one-way ANOVA and multiple regression with the SPSS 20.0. Results: Mean scores for self-efficacy, job stress and job satisfaction for the participants were 3.86 (5-point scale), 2.51 (5-point scale) and 3.37 (5-point scale) respectively. There was a negative correlation between self-efficacy and job satisfaction (r=-.653, p<.001). Factors influencing job satisfaction were job stress (${\beta}$=-.58, p=<.001), level of perception among the nurses that they were contributing to the health promotion of students (${\beta}$=-.21, p=.005) and marital status (${\beta}$=.17, p=.029). These 3 elements accounted for 47.7% of the variance in job satisfaction. Conclusions: The results indicate that reduction in job stress and increase in the perception that nurses are contributing to the promotion of students' health are important to reinforce the role function of nurses and to increase their work capabilities.

• Smart Structures and Systems
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• v.14 no.1
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• pp.1-16
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• 2014

In this work, we address the so-called sensor reachback problem for Wireless Sensor Networks, which consists in collecting the measurements acquired by a large number of sensor nodes into a sink node which has major computational and power capabilities. Focused on applications such as Structural Health Monitoring, we propose a cooperative communication protocol that exploits the spatio-temporal correlations of the sensor measurements in order to save energy when transmitting the information to the sink node in a non-stationary environment. In addition to cooperative communications, the protocol is based on two well-studied adaptive filtering techniques, Least Mean Squares and Recursive Least Squares, which trade off computational complexity and reduction in the number of transmissions to the sink node. Finally, experiments with real acceleration measurements, obtained from the Canton Tower in China, are included to show the effectiveness of the proposed method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.70-82
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• 2001

This study was conducted to derive the regional design rainfall by the regional frequency analysis based on the regionalization of the precipitation suggested by the first report of this project. Using the L-moment ratios and Kolmogorov-Smirnov test, the underlying regional probability distribution was identified to be the Generalized extreme value distribution among applied distributions. Regional and at-site parameters of the generalized extreme value distribution were estimated by the linear combination of the probability weighted moments, L-moment. The regional and at-site analysis for the design rainfall were tested by Monte Carlo simulation. Relative root-mean-square error(RRMSE), relative bias(RBIAS) and relative reduction(RR) in RRMSE were computed and compared with those resulting from at-site Monte Carlo simulation. All show that the regional analysis procedure can substantially reduce the RRMSE, RBIAS and RR in RRMSE in the prediction of design rainfall. Consequently, optimal design rainfalls following the legions and consecutive durations were derived by the regional frequency analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.54-60
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• 2007

A new method that optimizes a control of hydrocarbon (HC) addition to diesel exhaust gas for HC type DeNOx catalyst system has been developed. These catalysts are called as the HC-DeNOx catalyst in this paper. The system using HC-DeNOx catalyst requires a resonable quantity of hydrocarbons addition in the inlet gas of the catalyst, because the HC concentration in a diesel engine is so low that the HC is not sufficient for NOx conversion. Generally ambient temperature in the exhaust manifold is $250{\sim}350^{\circ}C$, so spray behavior in this case is different from that of any other condions. This research shows spray behavior of injected hydrocarbons in the transparent exhaust manifold.

• Environmental Analysis Health and Toxicology
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• v.18 no.4
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• pp.295-303
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• 2003

Physiological cellular activities responses to cadmium (Cd) exposure in green algae with several reductases activities and viability of the cell were examined. The cell division of green algae, Selenastrum capricornutum treated with 5ppm was significantly decreased than that of normal algae. The mean cell number of normal algal culture was as twice much as than that of algae at 6 days after Cd treatment. The cellular viability of algae was analysed by flow-cytometry with fluorescent dye after esterase reaction on cell membrane. The 85.35% of cellular viability of normal culture was decreased to 34.35% when algae was treated with 5 ppm of Cd at 6 days after treatment. It was considered that those method of flow-cytometry is useful tool for toxicity test on micro-organisms in the respect of identifying cellular viability. Also, the activities of both glutathione peroxidase (GPX) and ascorbate peroxidase (APX), which are indirectly react against oxidative stress through reduction of glutathione by Cd were significantly increased with 25%. It is considered that both GPX and APX are involved in the metabolic pathway of Cd -detoxification with similar portion in Selenasturm capricornutum.

• Journal of ILASS-Korea
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• v.2 no.3
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• pp.17-24
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• 1997

A simplified experiment was performed to figure out the atomization characteristics of rice-bran oil which it is highly viscous liquid by applying ultrasonic energy. A spray system, an ultrasonic system, and three kinds of hole-type nozzles(hole diameter: 0.31, 0.34, 0.37mm) were manufactured. To investigate the effects of ultrasonic energy on the atomization of a highly viscous liquid, a phase doppler particle analyzer was used for measurement and calculation of spray droplets data. Nozzle opening pressures were chosen of 3 levels, i.e, 16, 20, and 24MPa. As a result, it could be concluded that the ultrasonic energy was effective to improve the spray atomization when it applied to the fuel by means of 3 different nozzles because of the effects of the liquid fuel cavitation and relaxation between molecules caused by ultrasonic energy. The improvement rate of the spray atomization by the ultrasonic method compared with the conventional spray increased about 15% in the case of hole type nozzles. By increasing of the nozzle opening pressure and decreasing of the hole diameter, the atomization of spray droplets was improved.

• Journal of Korean Public Health Nursing
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• v.22 no.1
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• pp.97-107
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• 2008

Purpose: To investigate the relationships among self-esteem, depression and academic achievement in nursing college students. Method: The study subjects consisted of 350 nursing college students. The data were collected by self-administered questionnaire from September 3rd to 28th 2007. Results: 1) The mean scores self-esteem, depression, and academic achievement were 3.03 (on a 4-point scale), 4.00 (on a 7-point scale), and 87.33 (on a 100-point scores), respectively. 2) There were significant differences and impacts on self-esteem according to the economic state, character, attitude to parents, consideration of aptitude, satisfaction of school life and satisfaction of nursing. Depression differed significantly according to the economic state, residence type and satisfaction of school life. Academic achievement differed depending on the attitude to parents, consideration of aptitude and satisfaction of nursing. There was a significant positive correlation between self-esteem and academic achievement, but a negative correlation between self-esteem and depression in nursing college students. Conclusion: There was a positive correlation between self-esteem and academic achievement. Moreover, self-esteem can provide a basis for constructing further studies in intervention programs relating to the curriculum for nursing college students. Based on the above findings, programs are needed for the improvement of self-esteem and the reduction of depression, and further research is suggested on the development of such programs.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.143-152
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• 2003

This paper suggests the improvement of the Sumjinkang for the estimation of areal averages of heavy rainfall events based on the optimal network and three existing networks. The problem consists of minimizing an objective function which includes both the accuracy of the areal mean estimation as expressed by the Kriging variance and the economic cost of the data collection. The wellknown geostatistical variance-reduction method is used in combination with SATS which is an algorithm of minimization. At the first stage, two kinds of optimal solutions are obtained by two trade-off coefficients. One of them is a optimal solution, the other is an alternative. At the second stage, a quasi optimal network and a quasi alternative are suggested so that the existing raingages near to the selected optimal raingages are included in the two solutions instead of gages of new gages.