• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.2
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• pp.116-124
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• 1994

There has been studied a lot of two dimensional hydrofoil sections for the boundary layers. This paper suggests that the plaiable roughness effects on boundary layer transition region of suction side for NACA 4412 hydrofoil sections provided by auxieiary shape factor and lag-entrainment effects. These results show that the laminar sepration. Transition and end of transition of the boundary layer due to pitting roughness effects, to the foil Reynold's number as well as to the angle of attack were delayed a little. And comparisons with valuable the other calculations and measurements show qualitative agreements.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.256-262
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• 2018

This study introduces a novel Soft Switching (SS) Pulse Width Modulated (PWM) AC-DC boost converter. In the proposed converter, the main switch is turned on with Zero Voltage Transition (ZVT) and turned off with Zero Current Transition (ZCT). The main diode is turned on with Zero Voltage Switching (ZVS) and turned off with Zero Current Switching (ZCS). The auxiliary switch is turned on and off with ZCS. All auxiliary semiconductor devices are turned on and off with SS. There is no extra current or voltage stress on the main semiconductor devices. The majority of switching energies are transferred to the output by auxiliary transformer. Thus, the current stress of auxiliary switch is significantly reduced. Besides, the proposed converter has simple structure and ease of control due to common ground. The theoretical analysis of the proposed converter is verified by a prototype with 100 kHz switching frequency and 500 W output power. Furthermore, the efficiency of the proposed converter is 98.9% at nominal output power.

• The Journal of Korean Academic Society of Nursing Education
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• v.25 no.1
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• pp.17-26
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• 2019

Purpose: This study was conducted to verify the validity and reliability of the modified Transition Shock Scale for use among nursing students. Methods: From March 8-April 3, 2018, 207 nursing students participated in this study and were asked to complete self-reported questionnaires, including transition shock, clinical stress, and adapting to clinical practicums. The IBM SPSS Win 18.0 and AMOS 18.0 programs were used for data analysis. Results: A confirmatory factor analysis supported good convergent and discriminant validities ($x^2/df=1.58$, TLI=.92, CFI=.95, RMSEA=.053, AVE=.51-.68, CR=.75-.68). Correlations among transition shock, clinical stress (r=.34, p<.001), and adapting to clinical practicums (r=-.54, p<.001) were significant. Cronbach's alpha for the overall scale was .85, and for the six subfactors it ranged from .65 to .75. Conclusion: The findings suggest that the 17-item transition shock questionnaire is an appropriate instrument for measuring nursing students' transition shock with good validity and reliability.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.413-416
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• 2002

The dielectric responses of 10 and 40 wt% siloxane-epoxy copolymers were investigated in temperature range near the glass transition of polydimethylsiloxane at which the dielectric transitions were also observed. On the other hand, the pure epoxy did not show any dielectric transition in measurement temperature range -90 to 150 $^{\circ}C.$ The experimental data showed that for the copolymer investigated, the temperature-frequency super-position principle could be applied to the dielectric response. From the Cole-Cole equation, the dielectric relaxation of the 10 wt% siloxane near the glass transition temperature resulted in a broad distribution with ${\beta}=$ 0.19 and the relaxation time at -70 $^{\circ}C$ was 5.3 ${\times}$ $10^{-2}$s. The glass transition temperature, 188 K, was estimated by using WLF relation, which was consistent with the data presented in experiment.

• KDI Journal of Economic Policy
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• v.43 no.2
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• pp.53-79
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• 2021

The recession caused by the COVID-19 crisis has features that could disproportionately harm female employment. Risk of infection and social distancing measures may have disrupted jobs in face-to-face industries, which have traditionally hired more women than men. School closures and a consequent increase in childcare and homeschooling demands may have discouraged labor market participation by working mothers. Using the Economically Active Population Survey, I examine how female employment was affected by each factor. I find that the gender gap in the Employment to Non-participation (E to N) transition rates is twice as large as the gap in the Employment to Unemployment (E to U) transition rates. Women's overrepresentation in the face-to-face industries accounts for most of the gap in the E to U transition but only a third of the gap in the E to N transition. The rise in non-participation is especially pronounced among married women aged 39-44, the group most likely to have elementary-school-age children.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.4
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• pp.192-199
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• 2004

Elastic-factor of elastic epoxy were investigated by TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis), TGA (Thermogravimetric Analysis) and FESEM (Field Emission Scanning Electron Microscope) for structure-images analysis as toughness-investigation to improve brittleness of existing epoxy resin. A range of measurement temperature of the TMA and DMTA was changed from -20($^{\circ}C$) to $200^{\circ}(C)$, and TGA was changed from $0^{\circ}(C)$ to $600^{\circ}(C)$. Glass transition temperature (Tg) of elastic epoxy was measured through thermal analysis devices with the content of 0(phr), 20(phr) and 35(phr). Also, thermal expansion coefficient (a), high temperature, modulus and loss factor were investigated through TMA, TGA, and DMTA. In addition, the structure of specimens was analyzed through FESEM, and then elastic-factor of elastic epoxy was visually showed by FESEM. As thermal analysis results, 20(phr) was more excellent than 30(phr) thermally and mechanically. Specially, thermal expansion coefficient, high temperature, modulus, and damping properties were excellent. By structure-images analysis through FESEM, we found elastic-factor of elastic epoxy that is not existing epoxy, and proved high impact.

• Journal of Yeungnam Medical Science
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• v.23 no.1
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• pp.10-18
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• 2006

Epithelial to mesenchymal transition (EMT) is an important etiologic factor for the development of peritoneal fibrosis in CAPD patients. Mesothelial cells are main source of trans-differentiated fibroblasts under stress from the bioincompatible peritoneal dialysate. In our study there was no difference in dialysate TGF-${\beta}$ and VEGF between the low and high GDP groups during an initial 12 months. However, after adjusting with D-CA125, the low GDPs group showed a significantly lower D-TGF-${\beta}$/D-CA125 and D-VEGF/CA125 during the initial 12 months. Among the adjusted peritoneal growth factors for CA125, VEGF/CA125 and TGF-b/CA125 were factors significantly associated with greater EMT in this study. Adjustment of the peritoneal growth factor for effluent CA125 (surrogate for mass of HPMCs) revealed significant association with EMT suggesting that the fibroblastoid transition from HPMCs could be affected by the amount of intraperitoneal growth factors (TGF-b, VEGF) per unit mass of HPMCs. There was significant improvement in both cell score and D-CA125 at the sixth and 12th months after switching from a high GDPs solution to a low GDPs solution. Use of icodextrin solution in patients who had average peritoneal transport showed not only better systemic effects such as decreased glucose absorption via dialysate but also preservation of the peritoneum, including less EMT and high mesothelial bulk mass. In conclusion, Therapy with low GDP solution including icodextrin may positively impact preservation of the peritoneal membrane integrity and prevention of peritoneal fibrosis with time on PD.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.230-240
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• 1990

An exprimental research has been carried out to find the intermittent flow pattern in the transition region of a turbulent round jet in order to elucidate detailed turbulence structure and to accumulate basic data necessary for computational turbulence modelling. Turbulent signals were processed digitally to obtain conventional or conditional velocity components. The high-order conditional correlations obtained in this study showed similar trends as those of other free shear flows. It was found that the non-turbulent fluid contributes negligibly to the turbulent kinetic energy production and its diffusive transport and that the diffusion by bulk convection has the same order of magnitude as the gradient diffusion in the free boundary region. The statistical analyses such as flatness factor, skewness factor and probability density functions of turbulent and non-turbulent zone durations have also been performed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.4 s.107
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• pp.324-329
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• 2006

In this paper, a resonator with the substrate integrated waveguide(SIW) structure at the satellite communication band is presented. The SIW structure is realized by via-holes on the dielectric substrate and has an advantage of integration with other circuits. For the measurement, a designed back-to-back transition has the insertion loss of 0.4 dB at 18 GHz. Also, the quality factor of the resonator with the SIW structure including back-to-back transition is obtained to be 222. The high-Q resonator with the SIW structure can be used in filter, oscillator, and voltage controlled oscillator.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.323-337
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• 2009

This paper researched the adiabatic characteristic, safety and sound insulation characteristic of rolling stock window pane type and transition process of korean train vehicle window glass, and also including investigating a hereafter course of development. The window pane have provided the romantic feeling and the external scenery of train travel to the passenger in period of korea 110 year railway history. From the adiabatic viewpoint, this paper reviewed heat conductivity(U-value) and solar factor according to window pane type, including the safety and sound transmission loss of window pane.