• Management & Information Systems Review
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• v.33 no.2
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• pp.119-133
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• 2014

This Research focuses on the effect of the price limits change in KOSDAQ market change on the volatility. The sample period ranges from 22 May 2000 to 24 March 2010 for daily data. We construct two subsample periods for comparing with the effect of the change of the price limit. These limits were relaxed from 12% to 15% on March 25, 2005. The first subsample period is from 25 March 2000 to 24 March 2005. The second subsample period is from 25 March 2005. to 24 March 2010. We employee four different volatility, which are the range-based volatility of Parkinson(1980; PK), Garman and Klass(1980; GK) Rogers and Satchell(1991; RS), Yang and Zhang(2008; YZ). The empirical result as follows. The major findings are summarized as follows; First, the volatility of individual stocks in KOSDAQ market reduces significantly after the price limit change. Second, There is so high volatile especially when the volatility of stock prices is high. Third, There is no meaningful relationship between volatility and market capitalization. Fourth, the more volume stocks reduce the volatility. Our results show the volatility decreased the more large volume, the more trading amount and the high price stock.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.12
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• pp.1675-1679
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• 2011

To improve the quality and palatability of Kochujang, the physicochemical properties, antioxidant capacity, and sensory evaluation of Kochujang were assessed when red ginseng and wild herbal extract were added during fermentation. This study investigated the antioxidant capacities of general Kochujang (GK) and Kochujang prepared with red ginseng and fermented wild herbal extract (RGK) by employing various in vitro antioxidant assays such as DPPH and FRAP assays. Inhibition of lioxygenase (LOX) activity was also investigated. RGK exhibited significant antioxidant effects compared to control in DPPH, FRAP, and LOX assays. The LOX inhibitory activity of RGK ($68.68{\pm}3.37%$) at 100 ${\mu}g$/mL was markedly higher than those of GK ($31.21{\pm}2.64%$) and NDGA (positive control, $30.54{\pm}1.36%$). All concentrations of RGK showed significantly higher FRAP activities than that of GK. The addition of red ginseng and fermented wild herbal extract exhibited better sensory characteristics in terms of color, flavor, taste and overall preference. We concluded that RGK improves not only functional properties but also sensory properties as well.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.287-294
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• 2008

Three amino acid residues (His119, Glu164, and Glu338) in the active site of Thermus caldophilus GK24 ${\beta}$-glycosidase (Tca ${\beta}$-glycosidase), a family 1 glycosyl hydrolase, were mutated by site-directed mutagenesis. To verify the key catalytic residues, Glu164 and Glu338 were changed to Gly and Gln, respectively. The E164G mutation resulted in drastic reductions of both ${\beta}$-galactosidase and ${\beta}$-glucosidase activities, and the E338Q mutation caused complete loss of activity, confirming that the two residues are essential for the reaction process of glycosidic linkage hydrolysis. To investigate the role of His119 in substrate binding and enzyme activity, the residue was substituted with Gly. The H119G mutant showed 53-fold reduced activity on 5mM p-nitrophenyl ${\beta}$-D-galactopyranoside, when compared with the wild type; however, both the wild-type and mutant enzymes showed similar activity on 5mM p-nitrophenyl ${\beta}$-D-glucopyranoside at $75^{\circ}C$. Kinetic analysis with p-nitrophenyl ${\beta}$-D-galactopyranoside revealed that the $k_{cat}$ value of the H119G mutant was 76.3-fold lower than that of the wild type, but the $K_m$ of the mutant was 15.3-fold higher than that of the wild type owing to the much lower affinity of the mutant. Thus, the catalytic efficiency $(k_{cat}/K_m)$ of the mutant decreased to 0.08% to that of the wild type. The $k_{cat}$ value of the H119G mutant for p-nitrophenyl ${\beta}$-D-glucopyranoside was 5.l-fold higher than that of the wild type, but the catalytic efficiency of the mutant was 2.5% of that of the wild type. The H119G mutation gave rise to changes in optima pH (from 5.5-6.5 to 5.5) and temperature (from $90^{\circ}C\;to\;80-85^{\circ}C$). This difference of temperature optima originated in the decrease of H119G's thermostability. These results indicate that His119 is a crucial residue in ${\beta}$-galactosidase and ${\beta}$-glucosidase activities and also influences the enzyme's substrate binding affinity and thermostability.

• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.488-496
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• 2015

This study was done to investigate the antidiabetic and antioxidant effects of Cibotium barometz in Streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by intravenous injection of STZ at a dose 45mg/kg.b.w. dissolved in citrate buffer(pH4.5). The ethanol extract of Cibotium barometz was orally administrated once a day for 7 days. The contents of serum glucose, triglyceride(TG) and total cholesterol were significantly decreased(p<0.05) in Cibotium barometz treated group compared to the those of STZ-control group, The content of glutathione(GSH) and activity of gluthathione-s-transferase(GST) were significantly increased (P<0.05) in Cibotium barometz treated group compared to the those of STZ-control group. and activityes of catalase(CAT) and glutathione peroxidae(GSH-Px) were signiicantly decreased (P<0.05) in Cibotium barometz treated group compared to the those of STZ-control group. Also the content of hepatic glycogen and activities of glucose-phosphate dehydrogenase(G-6-PDH)and glucokinase(GK) were significamtly increased(p<0.05), but activity of glucose-6-phosphatase (G-6-Pase) was significamtly decreased (p<0.05) in Cibotium barometz treated group compared to the those of STZ-control group. These results indicated that ethanol extract of Cibotium barometz would have antidiabetic and antioxidant effects in STZ-induced diabetic rats.

• Korean Journal of Environmental Agriculture
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• v.19 no.1
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• pp.38-43
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• 2000

This study was conducted to examine the effects of cow manure originated from the clay mineral (porphyrite, zeolite and bentonite) feeding on the growth of Zea mays GK729. CEC of the manure after bentonite, zeolite, and porphyrite feeding were 147.5, 137.0, and 114.0 cmol/Kg, respectively. These values were higher than that of non-mineral treated manure, 107.5 cmol/Kg. After 3 month growing, there was significant difference among treatment in the biomass prodcution and the content of minerals in plant tissue of Z. mays, but the physico-chemical properties of soils were not showed significant difference. For these results suggested that the clay mineral enhanced the grwoth of Z. mays according to the unknown mechanism, the further studies on the physiological changes will be needed.

• Journal of Korean Neurosurgical Society
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• v.61 no.6
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• pp.753-760
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• 2018

Objective : We investigated the effect of optimization in dose-limiting shell method on the dosimetric quality of CyberKnife (CK) plans in treating brain metastases (BMs). Methods : We selected 19 BMs previously treated using CK between 2014 and 2015. The original CK plans ($CK_{original}$) had been produced using 1 to 3 dose-limiting shells : one at the prescription isodose level (PIDL) for dose conformity and the others at low-isodose levels (10-30% of prescription dose) for dose spillage. In each case, a modified CK plan ($CK_{modified}$) was generated using 5 dose-limiting shells : one at the PIDL, another at intermediate isodose level (50% of prescription dose) for steeper dose fall-off, and the others at low-isodose levels, with an optimized shell-dilation size based on our experience. A Gamma Knife (GK) plan was also produced using the original contour set. Thus, three data sets of dosimetric parameters were generated and compared. Results : There were no differences in the conformity indices among the $CK_{original}$, $CK_{modified}$, and GK plans (mean 1.22, 1.18, and 1.24, respectively; p=0.079) and tumor coverage (mean 99.5%, 99.5%, and 99.4%, respectively; p=0.177), whereas the $CK_{modified}$ plans produced significantly smaller normal tissue volumes receiving 50% of prescription dose than those produced by the $CK_{original}$ plans (p<0.001), with no statistical differences in those volumes compared with GK plans (p=0.345). Conclusion : These results indicate that significantly steeper dose fall-off is able to be achieved in the CK system by optimizing the shell function while maintaining high conformity of dose to tumor.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1235-1243
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• 2021

Geostationary Ocean Color Imager 2 (GOCI-II) on Geo-KOMPSAT-2 (GK2B)satellite was developed as a mission successor of GOCI on COMS which had been operated for around 10 years since launch in 2010 to observe and monitor ocean color around Korean peninsula. GOCI-II on GK2B was successfully launched in February of 2020 to continue for detection, monitoring, quantification, and prediction of short/long term changes of coastal ocean environment for marine science research and application purpose. GOCI-II had already finished IAC and IOT including early in-orbit calibration and had been handed over to NOSC (National Ocean Satellite Center) in KHOA (Korea Hydrographic and Oceanographic Agency). Radiometric calibration was periodically conducted using on-board solar calibration system in GOCI-II. The final calibrated gain and offset were applied and validated during IOT. And three video parameter sets for one day and 12 video parameter sets for a year was selected and transferred to NOSC for normal operation. Star measurement-based INR (Image Navigation and Registration) navigation filtering and landmark measurement-based image geometric correction were applied to meet the all INR requirements. The GOCI2 INR software was validated through INR IOT. In this paper, status and results of IOT, radiometric calibration and INR of GOCI-II are analysed and described.

• Korean Journal of Remote Sensing
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• v.35 no.2
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• pp.337-342
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• 2019

This letter describes the development of WRI (Wildfire Risk Index) using GDAPS (Global Data Assimilation and Prediction System) and satellite data, and its application to the Goseong-Sokcho and Gangneung-Donghae wildfires in April 4, 2019. We made sure that the proposed WRI represented the change of wildfire risk of around March 19 and April 4 very well. Our approach can be a viable option for wildfire risk monitoring, and future works will be necessary for the utilization of GK-2A products and the coupling with the wildfire prediction model of the Korea Forest Service.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2935-2940
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• 2023

A polystyrene phantom was developed following the guidance of the International Atomic Energy Association (IAEA) for gamma knife (GK) quality assurance. Its performance was assessed by measuring the absorbed dose rate to water and dose distributions. The phantom was made of polystyrene, which has an electron density (1.0156) similar to that of water. The phantom included one outer phantom and four inner phantoms. Two inner phantoms held PTW T31010 and Exradin A16 ion chambers. One inner phantom held a film in the XY plane of the Leksell coordinate system, and another inner phantom held a film in the YZ or ZX planes. The absorbed dose rate to water and beam profiles of the machine-specific reference (msr) field, namely, the 16 mm collimator field of a GK Perfexion^TM or Icon^TM, were measured at seven GK sites. The measured results were compared to those of an IAEA-recommended solid water (SW) phantom. The radius of the polystyrene phantom was determined to be 7.88 cm by converting the electron density of the plastic, considering a water depth of 8 g/cm². The absorbed dose rates to water measured in both phantoms differed from the treatment planning program by less than 1.1%. Before msr correction, the PTW T31010 dose rates (PTW Freiberg GmbH, New York, NY, USA) in the polystyrene phantom were 0.70 (0.29)% higher on average than those in the SW phantom. The Exradin A16 (Standard Imaging, Middleton, WI, USA) dose rates were 0.76 (0.32)% higher in the polystyrene phantom. After msr correction factors were applied, there were no statistically significant differences in the A16 dose rates measured in the two phantoms; however, the T31010 dose rates were 0.72 (0.29)% higher in the polystyrene phantom. When the full widths at half maximum and penumbras of the msr field were compared, no significant differences between the two phantoms were observed, except for the penumbra in the Y-axis. However, the difference in the penumbra was smaller than variations among different sites. A polystyrene phantom developed for gamma knife dosimetry showed dosimetric performance comparable to that of a commercial SW phantom. In addition to its cost effectiveness, the polystyrene phantom removes air space around the detector. Additional simulations of the msr correction factors of the polystyrene phantom should be performed.

• Journal of the KSME
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• v.27 no.2
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• pp.132-136
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• 1987

최근 저자는 혼합모우드에 대한 Budiansky와 Rice의 $J_k$ 적분에 모순이 있음을 지적한 바 있다. 그러나, Kishimoto등은 파괴진행영역을 고려한 경로 독립적분J/^/을 제시하여 주목을 끌고 있다. Landes등은 Rice의 J적분을 정상상태 크리이프에까지 연장 적용하기 위한 $C^*$적분을 소개하였다. 그후 크리이프파괴에 대한 매개변수로서 Liu등에 의한 $C_{gk}{\;}^*$, Brust등에 의한 $T_k{\}^*$등이 소개되어 계속 연구중이다. 여기에서는 이러한 매개변수들에 대해 개괄적으로 서술하고자 한다.