• Korean Journal of Medicinal Crop Science
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• v.28 no.5
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• pp.331-338
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• 2020

Background: The aim of this study was to analyze the total phenol and total flavonoid contents and antioxidant activity of steam-treated leaves and rhizomes of Polygonatum sibiricum Redoute. In addition, we aimed to confirm their potential use as cosmetic materials by investigating their anti-aging and skin-whitening activity. Methods and Results: The leaves and rhizomes of P. sibiricum were treated with steam at different temperatures for different durations, and the antioxidant activity (DPPH and ABTS radical scavenging activity) and total phenol and total flavonoid contents of each sample were tested. The steam temperature and treatment duration siginificantly affected the antioxidant activity and, total phenol and total flavonoid content of the leaves and rhizome of P. sibiricum. Treating the P. sibiricum samples with steam at 120℃ for 12 h, yielded higher total phenol and total flavonoid contents. Comparatively, the samples treated with steam at 120℃ for 12 to 24 h showed significantly higher antioxidant activity. Further, the steamed samples of P. sibiricum demonstrated collagenase and tyrosinase inhibition activity, which indicated their anti-aging and skin-whitening properties. The samples steamed at 120℃ for 12 h, exhibited higher collagenase and tyrosinase inhibition activity. Conclusions: Leaves and rhizomes of P. sibiricum steamed at 120℃ for 12 h, showed highest antioxidant activity and, total phenol and total flavonoid contents than all other samples. Our results indicate the potential of using P. sibiricum as a cosmetic material by confirming its excellent anti-aging and whitening activity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.383-391
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• 2011

Numerical simulations have been conducted for the cylindrical steam reformer having various boundary temperature distributions. $CH_4$, $H_2O$, CO, $H_2$ and $CO_2$ are often generated or destroyed by the reactions, namely the Steam Reofrming(SR) reaction, the Water-Gas Shift (WGS) reaction and the Direct Steam Reforming(DSR) reaction. The SR and the DSR reactions are endothermic reactions, and the WGS reaction is an exothermic reaction. The rate of reactions can be slightly controlled by artificially given boundary temperature distributions. Therefore, the component ratio of the gases at the outlet are different for various boundary temperature distributions, namely the constant, cubic and linear distributions. Among these distributions, the linear temperature distribution is outstanding for efficient hydrogen production of the steam reformer.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.367-373
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• 1996

H$_{\infty}$ robust control theory is applied to the nuclear steam generator level control. Nuclear steam generator has the properties such as nonlinearity, non-minimum phase, and so, has some difficulties on level control. In a nuclear plant, it is more important to keep the operating variables under certain safety limits against various uncertainties than to meet the optimal performance. The designed H$_{\infty}$ controller shows robust level control against modelling error, disturbance in the nonlinear simulation. As the H$_{\infty}$ controller has both robustness and design transparency, it is adequate to the automation of level control and in licensibility

• The Journal of the Korea Contents Association
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• v.16 no.5
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• pp.746-759
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• 2016

The purpose of this study was examine the effects of STEAM(Science-Technology-Engineering-Art-mathematics) activities on young children's scientific process skill ability and problem solving ability. Subjects were 34 five-year-old young children from S and H child care centers located in G city. Subjects were divided into an experimental(n=17) and a control group(n=17). The experimental group took part in the STEAM activities during 8 weeks, while the control group took part in the traditional science activities. The procedure for this study consisted of a pre-study, a pre-test, the treatment, and a post-test schedule. The results of this study were as follows: First, the experimental group showed significantly higher score than the control group in total scientific process skill ability. Second, the experimental group showed significantly higher score than the control group in total problem solving ability. These findings suggest that the experience of STEAM activities for young children can be effective teaching-learning methods for young children's scientific process skill ability and problem solving ability.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.3
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• pp.75-83
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• 2001

The potential of oxygen delignification is a powerful tool to reduce detrimental environmental effects. This study was performed to investigate the effect of steam explosion treatment of chemically treated oak wood on oxygen-alkali pulping. Pulp yield during steam explosion treatment by ${Na_2}{O_3}$-NaOH impregnation was higher than the other impregnation chemicals. Also, NaOH extraction at room temperature after steam explosion treatment improved the kappa number from 140~116 to 90~64. Oxygen-alkali pulping of chemical steam explosion treated woods affected to pulp yields. ${Na_2}{O_3}$-NaOH impregnation was very effective to higher carbohydrate yields at same delignification level. Its carbohydrate yield seemed to be highly related to the effluent pH. Oxygen-alkali pulping after steam explosion treatment of ${Na_2}{O_3}$-NaOH impregnated wood was shown that carbohydrate yield was very high because its effluent pH was increase from natural to mild alkali. Even if oxygen bleaching limit the delignification to 50% in order to avoid unacceptable yield and viscosity losses, oxygen-alkali pulping after steam explosion by ${Na_2}{O_3}$-NaOH impregnation was possible to extend the delignification more than 80%. Considering high pulp yield with lower lignin content from steam explosion treated wood, it might be profitable to end the cook at a high kappa number instead of a low kappa number, and continuously apply the oxygen delignification, in order to better quality pulp.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.738-743
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• 2001

A computer program, capable of performing thermal design analysis of the triple pressure bottoming system of combined cycle power plants, was developed. The program is based on thermal analysis of the heat recovery steam generator and estimation of its size and steam turbine power. The program is applicable to various parametric analyses including optimized design calculation. This paper presents examples of analysis results for the effects of arrangement of heat exchanger units, steam pressures and deaerating sources on design performance indices such as steam turbine power and the size of heat recovery steam generator.

• Textile Coloration and Finishing
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• v.18 no.6 s.91
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• pp.25-30
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• 2006

Degumming is an essential process to improve the luster and smoothness of the silk filament. Silk varieties were degummed using different methods. A number of methods, from pad-steam to specific alkaline are being used for this propose. In this paper an attempt to compare the efficiencies of different degumming processes has been made. from the results, it may be observed that when silk fabrics were pad-steam, the degree of degumming, as assessed by weight loss. When the pad-steam degumming was carried out at different pHs, adjusted using alkalies, it was observed that at higher pH the weight loss is high. Pad-steam degumming as well as star degumming was found to be superior with minimum damage to the substrate. Among the alkalis used, the sodium carbonate gives the best results, since the weight loss is almost maximum with lower strength loss by over degumming. It is also efficient from the point of view of conservation of heat energy and time as against the comparable star degumming.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.35-42
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• 2009

The piping systems in the steam-driven power engines lie under the cyclic condition of thermal expansion and contraction by superheated steam. These phenomena might cause some severe damages on the pipes and the accessory devices. To avoid these damages, the calculation of the proper strength and the consideration of the reduced resultant forces on the materials are needed. In the present study, numerical investigations on the effects of the thermal deformation of the industrial piping system were performed with comparison of the design data. Commercial software, ABAQUS with the thermal-fluidic loadings based on the design conditions was used for the thermal stress analysis of the piping system. From the analysis of the initially-designed pipe supporters, the rearrangement was suggested to improve the piping design.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.303-308
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• 2001

A rotating blade of steam turbines is designed using blade design system. To minimize the design time. quasi three dimensional flow analysis code is adopted to calculate blade section. The blade section lies on a streamline determined by previous steam turbine design procedures. The blade design system makes a transform of streamline coordinates, (m, r$\theta$), to (m', $\theta$) coordinates and all design procedure except 3 dimensional stack-up is performed in the coordinates. Each designed blade section is stacked-up and whole 3 dimensional blade can be modified by correcting 2D section, repeatly. The full 3D numerial analysis for the one stage including designed rotating blade will be performed later

• Journal of KSNVE
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• v.9 no.2
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• pp.401-408
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• 1999

A method is presented for the vibration analysis of steam turbine-generator rotor system based on the component mode synthesis method. The motion of each component of the system is described by superposing constraint mode associated with boundary coordinates and constrained normal modes associated with internal coordinates. This method using real fixed-interface modes allows for significant reduction in system model size while retaining the essential dynamic characteristics of the lower modes. The capability of this method is demonstrated in the natural frequency and unbalance response analysis of the steam turbine-generator rotor system in which the dynamics of the pedestal is considered. The results by the present method are compared with finite element method and trnasfer matrix method in terms of the accuracy and computing time.