• Wind and Structures
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• v.19 no.2
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• pp.113-144
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• 2014

Separation bubble and conical vortices on a large-span flat roof were observed in this study through the use of flow visualization. The results indicated that separation bubble occurred when the flow was normal to the leading edge of the flat roof. Conical vortices that occur under the cornering flow were observed near the leading edge, and their appearance was influenced by the wind angle. When the wind changed from along the diagonal to deviating from the diagonal of the roof, the conical vortex close to the approaching flow changed from circular to be more oblong shaped. Based on the measured velocities in the conical vortices by flow visualization, a proposed two-dimensional vortex model was improved and validated by simplifying the velocity profile between the vortex and the potential flow region. Through measured velocities and parameters of vortices, the intensities of conical vortices and separation bubble on a large-span flat roof under different wind directions were provided. The quasi-steady theory was corrected by including the effect of vortices. With this improved two-dimensional vortex model and the corrected quasi-steady theory, the mean and peak suction beneath the cores of the conical vortices and separation bubble can be predicted, and these were verified by measured pressures on a larger-scale model of the flat roof.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.91-102
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• 2013

This paper proposes the improved LCCT(Inductor-Capacitor-Capacitor-Trans) Z-source DC-DC converter (Improved LCCT ZSDC) which can generate the bipolar output voltages according to duty ratio D. The proposed converter has the characteristic and structure of Quasi Z-source DC-DC converter(Quasi ZSDC) and conventional LCCT Z-source DC-DC converter(LCCT ZSDC). To confirm the validity of the proposed method, PSIM simulation and a DSP based experiment were performed for each converter. In case which the input DC voltage is 70V, the bipolar output DC voltage of positive 90V and negative 50V could generate. Also, as comparison result of the capacitor voltage ripple in Z-network and the input current under the same condition for each converter, the voltage stress and the capacitor voltage in Z-network of the proposed method were lower compared with the conventional methods. Finally, the efficiency for each method was investigated according to load variation and duty ratio D.

• Earthquakes and Structures
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• v.22 no.2
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.

• Composites Research
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• v.22 no.4
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• pp.1-12
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• 2009

In this paper, quasi-static crushing tests of composite circular tubes under axial compression load are conducted to investigate the energy absorption characteristics. Circular tubes used for this experiment are glass/epoxy (GFRP) composite tubes which are fabricated by the filament winding method. One edge of the composite tube is chamfered to reduce the initial peak load and to prevent catastrophic failure during crushing process. Energy absorption characteristics vary significantly according to the constituent materials, fabrication conditions, tube geometry and test condition. In tube geometry, according as inner diameter increase, unstable crush mode is caused by local buckling of delamination, but control of the fiber orientation should help composite tubes get stable crush mode.

• Journal of muscle and joint health
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• v.19 no.2
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• pp.152-160
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• 2012

Purpose: The purpose of this study was to test the effects of the Tai Chi exercise on metabolic syndrome and health-related quality of life in middle-aged women. Methods: A quasi-experimental design was used. Subjects were sixty middle-aged women with metabolic syndrome. All of the subjects were met the criteria of the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III). The subjects were divided into the experiment group (n=33) trained the Tai Chi for 12 weeks and the control group (n=27). Metabolic syndrome risk factors including blood pressure, waist circumference, glucose, triglyceride (TG), and high density lipoprotein cholesterol (HDL-C) were measured before and after the 12-week period. Euro Quality of Life Questionnaire 5-Dimensional Classification (EQ-5D) was used to evaluate the health-related quality of life. Results: The experiment group showed significant decreases in diastolic blood pressure, waist circumference, glucose, and TG; and increase in HDL-C compared to the control group. For the health-related quality of life evaluation, the experiment group showed significant improvement more than the control group. Conclusion: The Tai Chi exercise may be effective intervention in preventing cardiovascular disease caused by metabolic syndrome in middle-aged women.

• The Journal of Korean Academic Society of Nursing Education
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• v.26 no.2
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• pp.132-145
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• 2020

Purpose: The purpose of this study was to examine the effects of a care promotion program based on nursing students' self-understanding. Methods: A quasi-experimental approach using a randomized clinical trial pre- and posttest design was used. Participants were assigned to an experiment group (n=29) or control group (n=30). Data were collected from June 23 to September 8, 2017. The experiment group participated in a care promotion program based on self-understanding for 24 hours through eight sessions covering eight different topics. The data were analyzed using t-test and repeated-measures ANOVA using SPSS/WIN 21.0. Results: Compared to the control group, the experiment group reported significant positive changes for college life adjustment (F=28.74, p<.001), emotional intelligence (F=15.66, p<.001), and interpersonal caring behavior (F=9.37, p=.003). Conclusion: Findings from this study indicate that care promotion based on a self-understanding improvement program with the application of group enneagram education is a useful intervention strategy to promote the care promotion program based on nursing students' self-understanding. Care promotion based on self-understanding will be utilized as an intervention program to form positive values of care and interpersonal relationship through care awareness, self-change, understanding of others and care experience in the group.

• Journal of Oriental Neuropsychiatry
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• v.17 no.1
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• pp.121-127
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• 2006

Objective : As this is a quasi-experimental study by the post-test design for a nonequivalent control group, it was attempted to verify the effect of massage using aroma oil on whether or not the normal vaginal delivery of primiparous mothers. Methods : As for the experimental treatment, it applied the aroma oil massage to the experiment group when the cervical dilatation was $4{\sim}5cm$, and as for the data analysis, it conducted the significance test using the program of SPSS 12K for Windows, with Chi-square test $(X^2)$ and t-test. Results : The experiment group that carried out the aroma massage therapy, was high in the cases of normal vaginal delivery(P<0.05), compared to the control group that did not carry out the aroma massage therapy. Conclusion : The experiment group, which received the aroma massage therapy, had significant difference in the cases of normal vaginal delivery, compared to the control group that did not receive the aroma therapy, thus the aroma massage therapy is thought to be a nursing-intervention plan, which can be usefully applied as to the primiparous mothers aiming at normal vaginal delivery.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.7
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• pp.465-470
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• 2022

This paper studied the high-velocity impact behavior characteristics of metal materials by crosschecking the high-velocity impact analysis with the high-velocity impact experiment results of aluminul 6061. The coefficients of the Huh-Kang material model and the Johnson-Cook fracture model were calculated through quasi-static using MTS-810 and dynamic experimenting using the Hopkinson bar equipment for high-velocity impact analysis. The penetration velocity and shape were predicted through high-velocity impact analysis using the LS-DYNA. The resultes were compared with the experiment results using a high-velocit experiment equipment. It is intended to be used the containment evaluation research for aircraft gas turbine engine blade.

• Journal of Korean Home Economics Education Association
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• v.19 no.1 s.43
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• pp.65-79
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• 2007

The purpose of this study was to test the effects of practical reasoning home economics instruction on middle school students' views of home economics. Thomas(1986) categorized six alternative views of home economics as education for women, manual training, application of science, household management, family development, and an intervention. This study carried a quasi-experiment research with an independent variable of types of instruction and a dependent variable of views of home economics. The experiment was carried with the sample of 137 8th grade students in Gwangju area for ten class hours. Paired t-test was performed to examine the pretest-posttest differences of each experiment group and comparison group. The results showed that practical reasoning instruction improved level of the view of home economics as an intervention, and decreased level of the view of home economics as manual training. From the results of this study, conclusion can be made that practical reasoning home economics instruction is effective in changing to the appropriate views of home economics. Also it is expected that current Korean home economics textbook can lead to the views of home economics as household management and as family development.

• The Journal of Korean Society for School & Community Health Education
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• v.15 no.2
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• pp.63-76
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• 2014

Objectives: The purpose of this study was to explore the effects of 'affirmative language' experiment upon freshmen nursing students' negative affect, self-efficacy and stress coping style. Methods: A nonequivalent control quasi-experiment was conducted on the subjects of 55 freshmen nursing students for 26(experimental group) and 29(control group). Data were analyzed using x2-test and t-test for participants' homogeneity test and conducted content analysis of process diary record and personal impressions. Results: As for negative affect, in case of the experimental group, depression(t=-2.384, p=.022) and anxiety(t=-2.243, p=.025) were significantly low with no difference for the control group. As for self-efficacy, both experimental and control groups showed significance and as for stress coping style, the control group used sub-categorized strategies better than the experimental group. There were 4 topics and subsequent 15 topics derived from the content analysis. 'Affirmative language' experiment showed alleviation of depression and anxiety helpful for study participants in self-reporting measurement, and helpful for stress self-management competence. Conclusion: It is necessary to connect the curriculum operation with interest of competence and practice of students stress self-management through the participating experiment experience.