• Food Science and Biotechnology
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• v.17 no.2
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• pp.379-383
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• 2008

Extraction characteristics of garlic and functional properties of corresponding extract were monitored by response surface methodology (RSM). Maximum extraction yield of 26.41% was obtained at microwave power of 146.29 W, ethanol concentration of 63.31 %, and extraction time of 5.88 min. At microwave power, ethanol concentration, and extraction time of 114.84 W, 58.83%, and 1.42 min, respectively, maximum electron-donating ability (EDA) was 72.86%. Maximum nitrite-scavenging ability was 94.62% at microwave power, ethanol concentration, and extraction time of 81.83 W, 2.65%, and 3.83 min, respectively. Superoxide dismutase (SOD) showed maximum pseudo-activity of 49.12% at microwave power of 34.23 W, ethanol concentration of 33.11 %, and extraction time of 4.40 min. Based on superimposition of 4-dimensional RSM with respect to extraction yield, electron-donating ability, nitrite-scavenging ability, and pseudo-activity of SOD, optimum ranges of extraction conditions were microwave power of 0-100 W, ethanol concentration of 40-70%, and extraction time of 2-8 min.

• Food Science and Biotechnology
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• v.16 no.2
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• pp.299-305
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• 2007

Response surface methodology was employed to optimize extraction conditions for finding the maximal functional properties of Pleurotus eryngii. Based on central composite design, the study plan was established with variations of microwave power (30-150 W), ethanol concentration (0-99.9%), and extraction time (1-9 min). Regression analysis was applied to obtain a mathematical model. A maximal yield of 47.86% was obtained when the microwave power, ethanol concentration, and extraction time were set at 122.7 W, 42.14%, and 8.3 min, respectively. A maximized electron donating ability of 93.32% was found under the following conditions: a microwave power of 144.19 W, an ethanol concentration of 49.52%, and an extraction time of 6.7 min. When the microwave power, ethanol concentration, and extraction time were set at 125.43 W, 40.54%, and 8.1 min, respectively, the maximum nitrite-scavenging ability was 80.47%. The optimum ranges of the extraction conditions, superimposed by the response surface methodology, could predicate a microwave power of 110-150 W, ethanol concentration of 0-45%, and extraction time of 7-9 min.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.6
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• pp.236-241
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• 2006

This paper presents a transfer capability enhancement process using VSC HVDC system which can control active power as well as reactive power. The transfer capability is constrained by stability like voltage stability as well as thermal rating of power system components. Transfer capability of the power system limited by these constraints may be enhanced by reactive power control ability and active power flow control ability of the VSC HVDC system. To enhance the transfer capability of the system using VSC HVDC, selection of the HVDC installation site is performed. In this work, power zones which consist of major power plants and their sinks are identified using power tracing and distribution factor. Alternative route of major AC transmission line in the power zone is identified as VSC HVDC system.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.93-96
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• 2022

The boiler tubes of thermal power plants are exposed to harsh environment of high temperature and high pressure, and the deterioration state of materials rapidly increases. In particular, parent material and welds of the materials used are subjected to a temperature change and various constraints, resulting in deformation and its growth, resulting in frequent leakage accidents caused by tube failure. The power plant checks the integrity of boiler tubes through non-destructive testing as it may act as huge costs loss and limitation of power supply during power station shutdown period due to boiler tube leakage. However, the current non-destructive testing is extremely limited in the field to detect micro cracks. In this study, the ability of metal magnetic memory technique to detect flaws of size that are difficult to inspect by the visual or general non-destructive methods was verified in the early stage of their occurrence.

• Food Science and Preservation
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• v.18 no.1
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• pp.59-64
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• 2011

This study was performed to investigate antioxidant activity of various solvent extracts (methanol, ethanol, acetone and water) from canola meal. As the concentration of all extracts increased, antioxidant activities increased gradually. Among solvent extracts from canola meal, methanol extract showed the highest antioxidant activities with $EC_{50}$ values of 0.9, 3.5, 1.3, and 8.5 mg/mL for DPPH radical scavenging ability, ABTS radical scavenging ability, reducing power, and chelating ability, respectively, and it had the highest total phenolics and total flavonoids contents. Furthermore, methanol extract was fractionated into three fractions (MF 1, MF 2, and MF 3) using Sephadex LH-20 column. The highest antioxidant activity was found on MF 2 for DPPH radical scavenging ability, on MF 3 for ABTS radical scavenging ability and reducing power, and on MF 1 for chelating ability at the same concentration of 1.5 mg/mL. The results indicated that each fraction containing various antioxidant materials seemed to have different influence at each antioxidant activity.

• Food Science and Preservation
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• v.18 no.4
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• pp.546-551
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• 2011

Response surface methodology (RSM) was used for the microwave-assisted extraction (MAE) of the effective components of grape seed, such as its antioxidative and nitrite-scavenging abilities. Microwave power (2,450 MHz, 0-160W), ethanol concentration (0-100%), and MAE time (1-5 min) were used as independent variables (Xi) for the central composite design to yield 16 different MAE conditions. The optimum MAE conditions were predicted for the dependent variables of the extracts, such as the total phenolic content ($Y_1$) antioxidative ability ($Y_2$), and nitrite-scavenging ability ($Y_3$), depending on different microwave powers, ethanol concentrations, and MAE times. The determination coefficients ($R^2$) of the regression equations for the dependent variables ranged from 0.8024 to 0.9498. The maximal values of each dependent variable were predicted at different MAE conditions, as follows: 3.19% total phenolic content at 142.32W, 44.30% ethanol, and 4.36 min, and 1.22 antioxidative ability at 84.44W, 56.60% ethanol, and 3.28 min. More than 99.5% nitrite-scavenging ability was predicted at pH 1.2-3.0, 30.80-106.58W, 49.32-55.18% ethanol, and 3.72-4.58min, respectively. The results indicated that the total phenolic content and anti oxidative ability showed a higher correlation with each other in that they were more influenced by microwave power than by the other variables, while the nitrite-scavenging ability was largely influenced by the ethanol concentration.

• Research in Community and Public Health Nursing
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• v.28 no.3
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• pp.313-323
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• 2017

Purpose: The purpose of this study is to investigate factors affecting social problem-solving ability of alcohol-dependent patients with a focus on gender differences. Methods: Participants were 250 alcohol-dependent people(men 140, women 110) who were living in B, G and Y cities. Data were collected from January 10 to March 31, 2017 using self-report questionnaires. Abstinence self-efficacy, alcohol insight, unconditional self-acceptance, and social problem-solving ability were investigated. For data analysis, t-test, one-way ANOVA, Pearson correlation coefficients and multiple regression were employed. Results: Factors influencing social problem-solving ability for men were unconditional self-acceptance and age. The explanatory power was 28%. Factors influencing social problem-solving ability for women were unconditional self-acceptance, stress, religiousness, age, occupation and abstinence self-efficacy and the explanatory power was 72%. Unconditional self-acceptance and age were significant variables of social problem-solving ability in both men and women. Stress, occupation, religiousness and abstinence self-efficacy were significantly associated with social problem-solving ability in women but not in men. Conclusion: The results suggest that it is necessary to consider gender characteristics in order to develop effective management programs for social problem-solving ability in alcohol-dependent people.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.7
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• pp.20-28
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• 2009

This paper presents the design of zero current switching ZCS pulse frequency modulation type DC-DC converter for magnetron power supply. A magnetron serving as the microwave source in a microwave oven is driven by a switch mode power supply (SMPS). SMPSs have the advantages of improved efficiency, reduced size and weight, regulation and the ability to operate directly from the converter DC bus. The demands of the load system and the design of the power supply required to produce constant power at 4[kV]. A magnetron power supply requires the ability to limit the load current under short circuit conditions. The current source series resonant converter is a circuit configuration which can achieve this. The main features of the proposed converter are an inherent protection against a short circuit at the output, a high voltage gain and zero current switching over a large range of output power. These characteristics make it a viable choice for the implementation of a high voltage magnetron power supply.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.149-151
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• 2011

This paper describe that restoration ability raising method of power system operator when Power System fault happen. This paper introduce score management method about simulation training when supposed fault happened and essencial fault have to be trained for power system operator.

• Korean Journal of Food Science and Technology
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• v.34 no.6
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• pp.1013-1017
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• 2002

Functional activities of Flammulina velutipes extract including electron donating ability, nitrite-scavenging effect, and tyrosinase inhibition activity was examined. Extraction were carried out by microwave-assisted extraction (MAE) under different conditions including solvent and microwave power. Tyrosinase inhibition activity and nitrite-scavenging effect increased as microwave power increased during extraction. Total phenol content and electron-donating ability reached maximum at the microwave power of 90 W. Total polyphenol content and electron-donating ability increased as extraction time extended up to 15 min, with the highest tyrosinase inhibition obtained after 5 min extraction. Significantly higher tyrosinase inhibition activity was found in 99% ethanol extract, whereas greater nitrite-scavenging effect was observed in the water extract. The maximum nitrite-scavenging effect was found at pH 1.2 and decreased as pH increased.