• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1705-1707
• /
• 2005

This paper proposes a novel active frequency drift(AFD) method for the islanding prevention of grid-connected photovoltaic inverter. To detect the islanding phenomenon of grid-connected photovoltaic(PV) inverters concerning about the safety hazards and the damage to other electric equipments, many kinds of anti-islanding methods have been presented. Among them, AFD method using chopping fraction(cf) enables the islanding detection to drift up(or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD methods, which have a certain value of cf only, is inefficient and difficult to design the appropriate cf value analytically to meet the limit of harmonics. In this paper, the periodic chopping fraction based on an AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with the power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also good performance of islanding detection compare with the conventional AFD method.

• Journal of the Korean Applied Science and Technology
• /
• v.32 no.4
• /
• pp.781-788
• /
• 2015

In this study, the antioxidative effects of 50% ethanol extract, ethylacetate fraction and aglycone fraction obtained from dried whole plant of Solanum nigrum L. were investigated. The free radical scavenging activities ($FSC_{50}$) were $215.46{\mu}g/mL$, $42.43{\mu}g/mL$ and $52.28{\mu}g/mL$, respectively. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) in $Fe^{3+}-EDTA/H_2O_2$ system were $25.25{\mu}g/mL$, $7.05{\mu}g/mL$ and $6.25{\mu}g/mL$, respectively. 50% ethanol extract and aglycone fraction showed the cellular protective effect against $^1O_2$ induced cellular damage of rabbit erythrocytes at $5{\sim}25{\mu}g/mL$, but not at high concentrations. These results indicated that S. nigrum extract/fractions could be used as an antioxidative agent. However, it could induce cellular damage at high concentrations. In conclusion, a special caution is required to use S. nigrum extracts as a cosmetic ingredient.

• Food Science and Preservation
• /
• v.24 no.7
• /
• pp.965-974
• /
• 2017

This study was carried out to investigate the effect of particle size of naked oat flour (NOF) on physicochemical property and antioxidant activity. The NOF was passed through $250{\mu}m$ and $160{\mu}m$ size sieves to obtain three fractions (fraction A: $250{\mu}m$ or more, fraction B: $160-250{\mu}m$, and fraction C: $160{\mu}m$ or less). Moisture, crude protein, crude fat, and crude ash contents of NOF were 8.4, 15.7, 10.0, and 1.8%, respectively, and these contents were increased as the particle size of NOF decreased. The mineral and free amino acid contents of NOF also had a similar tendency. The contents of total starch, amylose, starch damage, total dietary fiber, ${\beta}$-glucan, total phenolics, and flavonoids in NOF were 56.4%, 21.4%, 11.7%, 11.0%, 4.7%, $237.8{\mu}g/g$ and $90.9{\mu}g/g$, respectively. As the particle size of NOF decreased, total starch, amylose, and starch damage contents increased, whereas total dietary fiber, ${\beta}$-glucan, total phenolic and flavonoid contents decreased. Also, three antioxidant activities of NOF were closely correlated with their total phenolics and flavonoids contents, showing high correlation coefficient values ($R^2=0.87$ and 0.81, respectively).

• Fire Science and Engineering
• /
• v.18 no.4
• /
• pp.64-71
• /
• 2004

This paper describes the result of the pump room fire analysis of the nuclear power plant using CFAST fire modeling code developed by NIST. The sensitivity studies are performed over the input parameters of CFAST: the constrained or unconstrained fire, Lower Oxygen Limit (LOL), Radiative Fraction (RF), and the opening ratio of the fire doors. According to the results, a pump room fire is the ventilation-controlled fire, so it is adequate that the value of LOL is 10% which is also the default value. It is anlayzed that the Radiative Fraction does not affect the temperature of the upper gas layer. It is appeared that the integrity of the cable located at the upper layer is maintained except for the safety pump at the fire area and the Conditional Core Damage Probability (CCDP) is 9.25E-07. It seems that CCDP result is more realistic and less uncertain than that of Fire Hazard Analysis (FHA).

• Journal of Nutrition and Health
• /
• v.33 no.7
• /
• pp.717-724
• /
• 2000

A number of epidemiological studies has indicated lifestyles including dietary habits are closely related to the development of certain forms of cancer. These findings have led several investigators to identify the ways in which these factors mdulate the risk of cancer. Seaweeds are rich sources of non-digestible polysaccharides which possibly posses physiological functions. In vitro studies showed several components in seaweeds inhibit tumor cell growth and mutagenicity of known food mutagens. On the other hand non-digestible polysaccharides of different food sources negatively affect mineral nutrition by decreasing mineral absorption. The objectives of this study was to investigate the effect of major seaweed intake on azoxymethane(AOM) - induced DNA damage a known cancer initiation step and on apparent absorption of calcium and iron. To accomplish these objectives twenty five ICR mice were divided into five groups and fed one of the following diets for 10 days : control diet d, diet containing 10% water-soluble fraction of seamustard or seatangle diet containing 10% water-insoluble fraction of seamustard or seatangle. AOM was injected 6 hours before sacrifice and N7-methylated guanines from the colonic DNA were quantified using a gas chromatography -mass spectroscopy. Fecal samples were collected on days 4 and 8. Caclium and iron contents of the diets and feces were analyzed using an atomic absorption spectrophotometry to determine the apparent absorption of these minerals. Results are as follows. AOM-induced guanine methylation of colon was decreased in animals fed diets containing water-soluble fractions of seamustard or seatangle compared to those in animals fed control diet although only the seatnagle fed group showed statistically significant effect. Apparent calcium absorption was significantly reduced in animals fed diets containing water-insoluble fractions of seaweeds. Iron absorption was significantly decreased and negatively balanced in animals fed diets containing water-insoluble fractions of both seaweeds, and water-soluble fraction of seatangle. In conclusion, seamustard and seatangle intakes may effectively prevent colon tumorigenesis by reducing a carcinogen-induced DNA damages, and more mechanistic studies on possible role of seaweeds on carcinogenesis are required. Also, adverse effects of seaweed diets cintaming a large amount of polysaccharides on mineral nutrition should be carefully monitored.

• Korean Journal of Food Science and Technology
• /
• v.27 no.6
• /
• pp.1008-1012
• /
• 1995

Glutinous rice was microparticulated and air-classified at different air classifying wheel speeds (ACWS) of 20,000 rpm and 15,000 rpm in a Turboplex classifier. The starch was concentrated to a coarse fraction and the protein was shifted to a fine fraction. The degree of starch damage of the coarse fraction was comparable to that of traditionally soaked glutinous rice. Yoogwa(Korean cracker) made from the fractions of $ACWS\;15,000{\sim}20,000\;rpm$ and below ACWS 15,000 rpm was very comparable to that made by the traditional method in degree of puffing, hardness and internal structure. It was also confirmed by the sensory evaluation, indicating that the microparticulation/air classification technology could be applied to produce raw material of Yoogwa. The developed noble process could exclude the long soaking step in the traditional Yoogwa process and reduce the pretest time remarkably.

• Archives of Pharmacal Research
• /
• v.27 no.1
• /
• pp.106-110
• /
• 2004

The antioxidant activities of Acanthopanax senticosus stems were evaluated in $CCl_4$-intoxicated rats. The n-butanol fraction from the water extract of the stems, when pretreated orally at 200 mg/kg/day for 7 consecutive days in rats, was demonstrated to exhibit significant increases in antioxidant enzyme activities such as hepatic cytosolic superoxide dismutase, catalase and glutathione peroxidase by 30.31, 19.82 and 155%, respectively. The n-butanol fraction whereas showed a significant inhibition of serum GPT activity (65.79% inhibition) elevated with hepatic damage induced by $CCl_4$-intoxication. Eleutheroside B, a lignan component, isolated from the n-butanol fraction was found to cause a moderate free radical scavenging effection DPPH, its scavenging potency as indicated in $IC_{50}$ value, being 58.5$\mu$ M. These results suggested that the stems of A. senticosus possess not only antioxidant but also hepatoprotective activities.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.52 no.1
• /
• pp.35-42
• /
• 2019

We investigated the protective effects of antioxidant fractions from a 70% ethanolic extract of Hizikia fusiformis in human dermal fibroblasts (HDFs). Powdered H. fusiformis was extracted with 70% ethanol and then partitioned into three fractions according to polarity using n-hexane (HFH), chloroform (HFC), and ethyl acetate (HFEA). Antioxidant activity was observed in HFEA at 0.66 mg/mL based on the half maximal inhibitory concentration ($IC_{50}$) of 1,1-diphenyl-2-picrylhydrazyl (DPPH), and at 0.24 mg/mL based on alkyl radical scavenging. The protective effects of the HFEA antioxidant fraction against 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH)-damaged HDFs and the expression of Type I procollagen in HDFs were examined. HFEA caused the proliferation of HDFs with and without AAPH treatment and protected against AAPH damage to HDFs in a dose-dependent manner ($50-200{\mu}g/mL$). This implies that the antioxidant properties of the fractions depended on their proliferative and protective effects. The HFEA antioxidant fraction had significant effects and caused the dose-dependent expression of Type I procollagen, an important anti-wrinkle protein, in HDFs. In conclusion, antioxidant substances in H. fusiformis were found in the ethyl acetate fraction, and the resulting HFEA may have cosmetic applications.

• Korean Journal of Agricultural Science
• /
• v.48 no.1
• /
• pp.119-131
• /
• 2021

Over-produced reactive oxygen species (ROS) exert oxidative damage on lipids, proteins, and DNA in the human body, which leads to the onset of neurodegenerative diseases such as Alzheimer's disease (AD). In this study, we explored the cellular antioxidant effect of Cirsium japonicum var. maackii (CJM) against hydrogen peroxide (H₂O₂)-induced oxidative stress in neuronal cells. The antioxidant activity was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, 2',7'-dichlorofluorescin diacetate and nitric oxide (NO) assays, and the molecular mechanisms were examined by Western blot analysis. H₂O₂ treatment of SH-SY5Y cells decreased cell viability and increased ROS and NO production compared to H₂O₂-untreated cells. However, CJM increased cell viability and decreased ROS and NO accumulation in the H₂O₂-treated SH-SY5Y cells compared to H₂O₂-treated control cells. Especially, the EtOAc fraction from CJM showed the strongest antioxidant effect compared with the other extracts and fractions. Therefore, we further examined the CJM mechanism against oxidative stress using the EtOAc fraction from CJM. The EtOAc fraction up-regulated the expressions of heme oxygenase-1, NAD(P)H quinone oxidoreductase 1, and thioredoxin reductase 1. These results indicate that CJM promotes the activation of antioxidative enzymes, which eliminate ROS and NO, and further leads to an increase in the cell viability. Taken together, our results show that CJM exhibited an antioxidant activity in H₂O₂-treated SH-SY5Y cells, and it could be a novel antioxidant agent for the prevention or treatment of neurodegenerative disease such as AD.

• Applied Chemistry for Engineering
• /
• v.30 no.1
• /
• pp.114-121
• /
• 2019

In this study, antioxidative, antibacterial and cytoprotective effects of the ethanol extract and ethylacetate fraction of Lycopus lucidus (L. lucidus) were compared and analyzed. Free radical scavenging activities ($FSC_{50}$) of the L. lucidus extract and fraction were found to be 65.1 and $64.9{\mu}g/mL$ respectively. In the $Fe^{3+}-EDTA/H_2O_2$ system, the reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) for the extract and fraction were 6.6 and $6.3{\mu}g/mL$, respectively which showed excellent total antioxidant abilities. The extract showed antibacterial activity against S. aureus, while the fraction showed in all the bacteria except for A. niger. The cytoprotective effect of L. lucidus extract was compared to that of the fraction and the effect against $^1O_2$-induced cellular damage of human erythrocytes (${\tau}_{50}$) was 51.3 and 73.7 min at $50{\mu}g/mL$, respectively. For the cytoprotective effect of keratinocytes damaged by $H_2O_2$ and UVB, the extracts did not show any efficacy but showed efficacy at $1-2{\mu}g/mL$, respectively. The fraction increased the cell viability up to 85.8 and 81.9%, respectively. As a result of intracellular ROS scavenging activity, the scavenging activity was observed at $1-2{\mu}g/mL$ of the fraction. From the results comparing the physiological activities of L. lucidus extract and the fraction, the ethylacetate fraction of L. lucidus has antioxidative effect similar to that of the extract whereas superior antimicrobial and cytoprotective effects than that of the extract. Overall, the ethylacetate fraction of L. lucidus protects cells from an external stress which can be used as a potential cosmetic material.