• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1085-1090
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• 2011

To assure the safety of rolling stock, it is important to perform the fatigue analysis of reduction gear unit in rolling stock considering a variation of velocity and traction motor capability. This paper presents fatigue analysis of the damage of reduction gear unit of railway vehicle under variable amplitude loading(VAL) based on quasi-static fatigue analysis using finite element model and linear Miner's rule. The VAL for the simulation was constructed from the tractive effort curve and train run curves of railway vehicle under commercial operation condition using MSC.ADAMS dynamic analysis. The finite element model for evaluating the carburizing effect on the gear surface was used for predicting the fatigue life of the middle gear based on strain-life based approach. The results showed that the frequent high starting torque due to a quick start as well as increasing numbers of stops at station would decrease the fatigue life of reduction gear unit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.131-136
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• 2011

This paper aims to examine the possibility of using an environmentally friendly $N_2$ as an alternative gas to $SF_6$. For this purpose, we have investigated breakdown characteristics of $N_2$ under impulse voltages in a quasi-uniform electric field gap. The 1.2/50[${\mu}s$] lightning impulse voltage, switching impulse voltages and oscillatory impulse voltages were applied at the test gap. The electric field utilization factor ranges from 0.5 to 0.8. The experimental data of $SF_6$ and $N_2$ acquired in the same experimental condition are presented in parallel for comparison. As a result, the breakdown voltages in $SF_6$ and $N_2$ are linearly increased with the gas pressure, also the breakdown voltages in $N_2$ are increased with increasing the gap distance and electric field utilization factor. The positive breakdown voltages are higher than the negative breakdown voltages. The nagative basic lightning impulse withstand level of 150[kV] in $N_2$ of about 0.5[MPa] is nearly equal to that in $SF_6$ of 0.15[MPa]. It is seen from the results obtained in this work that $N_2$ can be used as an eco-friendly alternative gas to $SF_6$ in distribution power equipment.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.9-18
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• 1994

In this study, we conducted experimental tests to evaluate fracture behaviors of fresh-butt welded metal by Acoustic Emission technique. We selected similar welding and dissimilar welding process, the one welded for SM45C, SS41 and SUS304 of each material, the other for SM45C and SS41, SM45C and SUS304 and SS41 and SUS304. The fracturing processes of weld metal were estimatied through the fracture toughness test with compact tension specimens and fractography analysis. In ASTM test method E-399, type I curves for materials of this study were obtained by load-cod diagram of fracture toughness test. and 5% offset load( $P_{5}$) was estimated as the estimated crack initial load( $P_{Q}$), The estimated crack initial load( $P_{Q}$) of similar welding materials generally lower than base matal, and then SM45C appeared greatly in decreasing rate of PB, SS41 and SUS304 appeared in order. $P_{Q}$ of dissimilar welding materials were lower than the similar welding materials. $P_{Q}$ of welding of SM45C and SS41 appeared in small, SUS304 and SS41 appeared greatly in dissimilar welding materials. In fracture toughness test, AE counts increased before the inflection point of the slope, decreased after that. It was found that increasing of AE counts were due to the microcrack formation at the crack tip near the $P_{5}$ point through AE data. For welding materials in this study, both low and high AE amplitude appeared simulataneously. It was confirmed that the low AE amplotude was due to formation of micro void, micro crack or micro dimple, the high AE amplitude was caused by microvoid coalescence and quasi-cleavage fracture through analyses of fractograpy.apy.apy.apy.

• Journal of KIISE
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• v.44 no.1
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• pp.21-26
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• 2017

In recent years, new technologies such as Internet of Things, Cloud Computing and Big Data are being widely used. And the type and amount of data is dramatically increasing. This makes security an important issue. In terms of leakage of sensitive personal information. In order to protect confidential information, a method called anonymization is used to remove personal identification elements or to substitute the data to some symbols before distributing and sharing the data. However, the existing method performs anonymization by generalizing the level of quasi-identifier hierarchical. It requires a higher level of generalization in case where k-anonymity is not satisfied since records in data table are either added or removed. Loss of information is inevitable from the process, which is one of the factors hindering the utility of data. In this paper, we propose a novel anonymization technique using decision tree based machine learning to improve the utility of data by minimizing the loss of information.

• Earthquakes and Structures
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• v.15 no.5
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Women's Health Nursing
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• v.8 no.3
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• pp.335-344
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• 2002

Providing visual information about the fetus to the mother by the ultrasound examination was found to be an effective nursing intervention to promote Maternal-Fetal Attachment. In keeping with the purpose of the study, to evaluate the effect of providing visual information by ultrasound on level of Maternal-Fetal Attachment, a non-equivalent experimental group quasi-experimental design was used. The data were collected using Cranley's Maternal-Fetal Attachment Scale(1981) with a research questionnaire that consisted of 16 items on general characteristics and 23 items on Maternal-Fetal Attachment from November 2, 2000 to August 11, 2001. Subjects were 126 pregnant women who were received visual information by ultrasound and 123 pregnant women who did not receive visual information by ultrasound after finishing examination. The data were analyzed by using the SPSS/PC+ window 10.0 version program. The results of this study were as follows: There was no statistical difference in general characteristics between both groups. The scores on Maternal-Fetal Attachment at second trimester show no statistical difference (t=1.123, p=0.263). The scores on Maternal-Fetal Attachment in both groups increased between the second trimester and third trimester. However, the increase was greater in the group receiving visual information by ultrasound as compared to the group which did not receive the visual information(t=-2.152, p=0.032). This result shows that providing visual information about the fetus by the ultrasound examination is effective in increasing Maternal-Fetal Attachment.

• Steel and Composite Structures
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• v.36 no.2
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• pp.119-141
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• 2020

In this paper, wavy square absorbers were experimentally and numerically investigated. Numerical simulations were performed with LS-Dyna software on 36 wavy absorbers and their crushing properties were extracted and compared with the simple one. The effect of different parameters, including wave height, wave depth, and wave type; either internal or external on the crushing characteristics were also investigated. To experimentally create corrugation to validate the numerical results, a set of steel mandrel and matrix along with press machines were used. Since the initial specimens were brittle, they were subjected to heat treatment and annealing to gain the required ductility for forming with mandrel and matrix. The annealing of aluminum shells resulted in a 76%increase in ultimate strain and a 60% and 56% decrease in yield and ultimate stresses, respectively. The results showed that with increasing half-wave height in wavy square absorbers, the maximum force was first reduced and then increased. It was also found that in the specimen with constant diameter and half-wave depth, an increment in the half-wave height led to an initial increase in efficiency, followed by a decline. According to the conducted investigations, the lowe maximum force can be observed in the specimen with zero half-wave depth as compared to those having a depth of 1 cm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.3
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• pp.24-32
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• 2011

[ $SF_6$ ]gas, which has an excellent dielectric strength and interruption performance, is used in various applications such as gas insulated switchgear (GIS) in substations. However, since $SF_6$ has a high global warming potential (GWP), it is necessary to find an eco-friendly alternative insulation gas. In order to examine the possibility of using alternative insulation gases for $SF_6$ in power distribution system equipment, the dielectric strength and physical phenomena of dry air in a quasi-uniform electric field are investigated experimentally in this paper. As a result, the breakdown voltages for positive polarity are higher than those for negative polarity under impulse voltage applications. The negative 50[%] flashover voltage, $V_{50}$ of dry air under conditions above 0.4[MPa] gas pressure, is higher than 150[kV], that is the basic impulse insulation level of distribution equipment. The $V_{50}$ increases linearly with increasing the gas pressure, regardless of the waveform and polarity of the applied impulse voltages. The voltage-time curves are dependent on the rise time of the impulse voltage and gas pressure. Furthermore, streamer discharge was observed through light emission images by an ICCD camera under impulse voltage applications.

• Journal of Korean Academy of Nursing
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• v.36 no.5
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• pp.721-731
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• 2006

Purpose: This study was done to describe the research trend of Complementary and Alternative Medicine(CAM) in Korea and internationally. Method: A Systematic review of CAM related literature published from 2000 to 2005 was done. A comprehensive search by using 34 CAM modalities as search terms to identify all articles dealing with CAM was undertaken from 4 databases: PubMed, RICHIS, KoreaMed, and Riss4U. A Total of 588 abstracts and 223 original articles were reviewed by two independent reviewers using systematic analysis guidelines. Data regarding the types of study design, characteristics of subjects and researchers, and classification of CAM modalities was recorded. The outcome measures of CAM were identified. Results: CAM research has been rapidly increasing worldwide in the last decade. In Korea, nursing(53.5%) followed by medicine(42.7%) occupied the majority of CAM research in comparison to medicine(42.9%) and disciplines in CAM(25.0%), like homeopathy, internationally. Prevailing research designs in Korea were experimental and quasi-experimental, however, randomized clinical trials were found. Internationally, survey research was dominant, with the exception of randomized clinical trials that were mostly an experimental design. Conclusion: The findings suggest that a robust research design in CAM research is needed to accumulate strong scientific evidence and to adopt nursing interventions from CAM modalities.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.24 no.2
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• pp.118-127
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• 2017

Purpose: The purpose of this study was to identify effects of self-evaluation using smartphone recording on competency in nursing skills, satisfaction and learning motivations in nursing students'. The setting was the open laboratory hours. Methods: A quasi-experimental pre/post-test design was conducted in September 2015. The participants were 82 sophomore nursing students from one University. The experimental group did self-evaluation by watching recorded video clips of their performance. The control group did not have any self-evaluation. The primary outcomes were scores from the foley catheterization checklist, scores from a student satisfaction tool, and scores from a learning motivation tool. Data were analyzed using ${\chi}^2$ test, Fisher's exact test, independent t-test, and paired t-test. Results: There was a significant higher mean score in levels of satisfaction by students in the experimental group compared to the control group (t=2.26, p=.027). In addition, improvement in communication skills by the experimental group was significantly higher than improvement in the control group (t=3.96, p<.001). Conclusion: Findings show that self-evaluation using smartphone recordings has positive effects on increasing both communication skills and satisfaction with practice during open laboratory hours. These results indicate that, self-evaluation using smartphone recording is useful as a supplement to traditional open laboratory education.