• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.569-579
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• 2005

An investigation for long-term strength characteristics of crushed sand concrete using crushed sands produced in Yang-san, Kim-hae and Jin-hae that can be assumed to respectively represent eastern, middle and western suburbs of Busan has been carried out. Concrete is composed of 70~80% of aggregates in whole volume so the effect of aggregates quality to the characteristics of concrete is very important. Since 1980s, aggregates used in concrete have already been substituted crushed stone because of the exhaustion of natural gravel and sand. Crushed sand tends to increase in using quantity because of the prohibition of sea sand picking and deterioration of river sand. Crushed sand is blended with river sand in order to investigate the quality changes and characteristics of concrete as variation of blend ratio of crushed sand (n, 50, 70, 80, 90, 100%). Slump and air content were measured to investigate the properties of fresh concrete. Unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, n, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased with a passage of time and they are expected to keep on increasing in long-term age as well. The experimental results of the qualifies of crushed aggregates in each producing area, were all satisfied with Korea Standard. The results of the measurement of slump exposed that slump preferably decreased as mixing rate increased till 70~80% but it increased to mixing rate 70~80%. The air content was exposed that it decreased by micro filler phenomenon according to that crushed sand b)ended ratio increased. According to the result of measuring unit weight in age of 7, 28, 60, 90, 180days, it increased in accordance with that blended ratio of crushed aggregates increases. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 50, 90, 180days, compressive strength was highest when it is 70% of blended ratio.

• Journal of the Korea Convergence Society
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• v.9 no.3
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• pp.137-144
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• 2018

The purpose of this study was to investigate the fusion effects and difference them of the deep transverse stroking, manual stretching exercise and active muscle release technique on psoas major muscle thickness and muscle tone, and pelvic angle in non-specific low back pain patients. Psoas major muscle thickness was significantly decreased after the application of the deep transverse stroking $0.19{\pm}0.16cm$ (p <0.05), manual stretching exercise $0.18{\pm}0.14cm$ (p <0.05), and active muscle release technique $0.43{\pm}0.35cm$ (p <0.05). The pelvic angle was significantly decreased after the application of the deep transverse stroking $4.48{\pm}1.63^{\circ}$ (p <0.05), manual stretching exercise $5.36{\pm}2.04^{\circ}$ (p <0.05), and active muscle release technique $7.24{\pm}2.23^{\circ}$ (p <0.05). The Psoas major muscle tone was significantly decreased after application of the deep transverse stroking $0.96{\pm}0.93Hz$ (p <0.05), but manual stretching exercise $0.87{\pm}1.20Hz$ (p> 0.05) and active muscle release technique $0.82{\pm}0.98Hz$ (p> 0.05) there was no significant difference after application. There were no significant differences between the three intervention methods in the pelvic angle and psoas major muscle thickness and tone changes. In order to change psoas major muscle thickness and pelvic angle, three intervention methods should be applied appropriately according to the condition and environment of the patient, and deep transverse stroking is more effective for changing psoas major muscle tone.

• The Korean Journal of Ecology
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• v.26 no.1
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• pp.39-47
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• 2003

The leaf aqueous extracts from five gymnosperms plant were investigated for allelopathy with five Hibiscus syriacus varieties. The leaf aqueous extract of Pinus rigida had the highest total phenolic compound of 2.21mg/L, whereas the soil under Pinus koraiensis canopy had the highest total phenolic compound of 1.38mg/L. Fourteen phenolic compounds were isolated from five gymnosperm plants by HPLC. Among them, phenolic compounds were the highest in P. rigida (320.56 g/mg) with the primary compound 5-sulfosalicylic acid (312.55 g/mg). The correlation between leaf total phenolic compound and pH was not significant, while the total phenolic compound of the leaf extract changed soil pH. The relative seed germination of H. syriacus varieties showed 25% was threshold concentration. The germination rates of varieties were similar to the control group or showed slight stimulation to treatment of P. koraiensis extract. H. syriacus Cambanha was similar to the control group or showed stimulation in all treated groups. H. syriacus Seohohyang showed stimulation in both root and shoot growth compared to the control group. In other varieties except Seohohyang, shoot growth was similar to the control group, while root growth was stimulated in all treated groups. The extracts of tested gymnosperms showed significantly more stimulation to transplanted Seohohyang seedlings, whereas others were similar to control or inhibited in the greenhouse. The dry weight of Seohohyang was greater in all treated groups than the control group, while other varieties were inhibited. All gymnosperm extracts stimulated the chlorophyll contents of Seohohyang and H. syriacus Koyoro but other varieties were not significantly affected. Accordingly, it is suggested that Seohohyang seems the most desirable when planted within these five gymnosperms.

• The Korean Journal of Financial Management
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• v.21 no.2
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• pp.125-151
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• 2004

This study tests the price discovery from US Treasury bond markets to Korean bond markets using the daily returns of Korean bond data (CD, 3-year T-note, 5-year T-note, 5-year corporate note) and US treasury bond markets (3-month T-bill, 5-year T-note 10-year T-bond) from July 1, 1998 to December 31, 2003. For further research, we divide full data into two sub-samples on the basis of the start-up of bond valuation system in Korean bond market July 1, 2000, employing uni-variate AR(1)-GARCH(1,1)-M model. The main results are as follows. First the volatility spillover effects from US Treasury bond markets (3-month T-bill, 5-year T-note, 10-year T-bond) to Korean Treasury and Corporate bond markets (CD, 3-year T-note, 5-year T-note, 5-year corporate note) are significantly found at 1% confidence level. Second, the price discovery function from US bond markets to Korean bond markets in the sub-data of the pre-bond valuation system exists much stronger and more persistent than those of the post-bond valuation system. In particular, the role of 10-year T-bond compared with 3-month T-bill and 5-year T-note is outstanding. We imply these findings result from the international capital market integration which is accelerated by the broad opening of Korean capital market after 1997 Korean currency crisis and the development of telecommunication skill. In addition, these results are meaningful for bond investors who are in charge of capital asset pricing valuation, risk management, and international portfolio management.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.1
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• pp.42-47
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• 2006

L-Ascorbic acid (AsA) is an essential nutrient for prevention of scurvy in humans, primates and guinea pigs that lack $L-gulono-\gamma-lactone$ oxidase which is required for the final step of AsA biosynthesis. AsA participates in various hydroxylation reactions involved in the biosynthesis of collagen. The purpose of this study is to clarify the role of AsA on collagen synthesis in 3T6 fibroblasts and primary cultured cells of chondrocytes. Cells were cultured in medium supplemented with catalase and AsA at various concentration. Supplement of AsA induced collagen synthesis in 3T6 fibroblasts and primary cultured cells of chondrocytes. The most remarkable induction of collagen synthesis by AsA was found in primary cultured chondrocytes. The content of collagen representing the amounts of extracellular matrix significantly increased in the cells of which growth was stimulated by AsA, while it decreased with increasing passage numbers of subculture in cells. It showed that the content of collagen decreased in the medium which contained AsA at the concentration higher than 5.0 mM. However, the contents of collagen to DNA were not different among various AsA concentrations. Supplementing with AsA resulted in enhancement of collagen formation and extracellular matrix. Therefore, there might be a Positive correlation between the activity of catalase and the AsA concentration. Moreover, it can be assumed that AsA stimulates the collagen synthesis by optimizing the cell-culture environment.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.1
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• pp.21-27
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• 2006

Effects of root, stem and leaf extracts of Zanthoxylum piperitum on the inhibition of lipid peroxidation in the hepatic microsome of rat, DPPH radical scavenging activity, soybean lipoxygenase activity and activated partial thromboplastin times (APTT) were examined in vitro. The highest inhibition of hepatic microsomal lipid peroxidation was observed by ethyl acetate fraction of the root and stem extracts. The high inhibition of lipid peroxidation was observed in the leaf, the root and the stem in order. The DPPH radical scavenging activity of ethyl acetate fraction was higher than that of n-butanol fraction and it was similar to the root and the steam extract. It was similar to the inhibition of hepatic microsomal lipid peroxidation. The DPPH radical scavenging activity was the highest in 0.50 mg/mL of ethyl acetate fraction, and it was 4.4-fold higher than that of a-tocopherol, as an antioxidant standard. The DPPH radical scavenging activity was dependent on the extract concentration in the range of $0.12\~5.00$ mg/mL. The soybean lipoxygenase activity of ethyl acetate fraction was higher than that of n-butanol fraction and it was similar to the root and the stem extracts. The soybean lipoxygenase activity was the highest in 0.50 mg/mL of ethyl acetate fraction. The soybean lipoxygenase activity was dependent on the extract concentration in the range of $0.12\~5.00$ mg/mL. The leaf extract showed the highest antithrombogenic effect followed by the stem and then the root extract. The activated partial thromboplastin times were dependent on the extract concentration in the range of $0.10\~2.00$ mg/mL.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.55-61
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• 2009

Recently, the number of high-rise buildings being built in Korea by major construction companies for residential and commercial use has been increasing. When constructing a high-rise building, it is necessary to apply massive amounts of concrete to form a mat foundation that can withstand the huge load of the upper structure. However, it is of increasing concern that due to limitations in terms of the amount of placing equipment, available job-sites and systems for mass concrete placement in the construction field, it is not always possible to place a great quantity of concrete simultaneously in a large-scale mat foundation, and for this reason consistency between placement lift cannot be secured. In addition, a mat foundation Is likely to crack due to the stress caused by differences inhydration heat generation time. To derive a solution for these problems, this study provides test results of a hydration heat crack reduction method by applying placement lift change and setting time control with a super retarding agent for mass concrete in a large-scale mat foundation. Mock-up specimens with different mixtures and placement liftswere prepared at the job-site of a newly-constructed high-rise building. The test results show that slump flow of concrete before and after adding the super retarding agent somewhat Increases as the target retarding time gets longer, while the air content shows no great difference. The setting time was observed to be retarded as the target retarding time gets longer. As the target retarding time gets longer, compressive strength appears to be decreased at an early stage, but as time goes by, compressive strength gets higher, and the compressive strength at 28 days becomes equal or higher to that of plain concrete without a super retarding agent. For the effect of placement lift change and super retarding agent on the reduction of hydration heat, the application of 2 and 4 placement lifts and a super retarding agent makes it possible to secure consistency and reduce temperature difference between placement lifts, while also extending the time to reach peak temperature. This implies that the possibility of thermal crack induced by hydration heat is reduced. The best results are shown in the case of applying 4 placement lifts.

• KSBB Journal
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• v.23 no.6
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• pp.463-469
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• 2008

During the last decade, monacolin-K biosynthesized by fermentation of red yeast rice (Monascus strains) was proved to have an efficient cholesterol lowering capability, leading to rapid increase in the market demand for the functional red yeast rice. In this study, the production medium composition and components were optimized on a shake flask scale for monacolin-K production by Monascus pilosus (KCCM 60160). The effect of three different soybean flours on the monacolin-K production were studied in order to replace the nitrogen sources of basic production medium (yeast extract, malt extract and beef extract). Among the several experiments, the production medium with dietary soybean flour to replace a half of yeast extract was very good for monacolin-K production. Plackett-Burman experimental design was used to determine the key factors which are critical to produce the biological products in the fermentation. According to the result of Plackett-Burman experimental design, a second order response surface design was applied using yeast extract, beef extract and $(NH_4)_2SO_4$ as factors. Applying this model, the optimum concentration of the three variables was obtained. The maximum monacolin-K production (369.6 mg/L) predicted by model agrees well with the experimental value (418 mg/L) obtained from the experimental verification at the optimal medium. The yield of monacolin-K was increased by 67% as compared to that obtained with basic production medium in shake flasks.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.213-222
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• 2016

Solubility data of hydrogen sulfide ($H_2S$) and methane ($CH_4$) in two kinds of ionic liquids with the same anion: 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][TfO]) and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyr][TfO]) are presented at pressures up to about 30 MPa and at temperatures between 303 K and 343 K. The gas solubilities in ionic liquids were determined by measuring the bubble point pressures of the gas + ionic liquid mixtures with various compositions at different temperatures using a high-pressure equilibrium apparatus equipped with a variable-volume view cell. The $H_2S$ solubilities in ionic liquid increased with the increase of pressure and decreased with the increase of temperature. On the other hand, the $CH_4$ solubilities in ionic liquid increased significantly with the increase of pressure, but there was little effect of temperature on the $CH_4$ solubility. For the ionic liquds [emim][TfO] and [bmpyr][TfO] with the same anion, the solubility of $H_2S$ as a molality basis was substantially similar, regardless of the temperature and pressure conditions as a molar concentration basis. Comparing the solubilities of $H_2S$ and $CH_4$ in the ionic liquid [emim][TfO], the solubilities of $H_2S$ were much greater than those of $CH_4$. For the same type of ionic liquid, the solubility data of $H_2S$ and $CH_4$ obtained in this study were compared to the solubility data of $CO_2$ from the literature. When compared at the same pressure and temperature conditions, the $CO_2$ solubility was in between the solubility of $H_2S$ and $CH_4$.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.275-282
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• 2010

A characteristic study of aqueous chlorine dioxide generation from sodium chlorite($NaClO_2$) by an undivided electrochemical cell with different anode materials were performed. $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA were used as anode materials and Pt-coated Ti electrode was used as cathode. Various electrochemical cell operating parameters such as cell residence time($t_R$), initial feed solution pH, sodium chlorite and sodium chloride(NaCl) concentration and applied current for the generation of chlorine dioxide in an un-divided cell were investigated and optimized. Estimated optimal cell residence times in $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode material systems were around 2.27, 1.52 and 1.52 sec, respectively. Observed optimum initial feed solution pH was around 2.3 in all anode material systems. Optimum sodium chlorite concentrations in $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode systems were around 0.43, 0.43 and 0.32 g/L, respectively. Optimum electrolyte concentration and applied current were around 5.85 g/L and 0.6 A in all anode systems. Current efficiencies of $IrO_2$-coated Ti, $RuO_2$-coated Ti and DSA anode systems under optimum conditions were 79.80, 114.70 and 70.99%, respectively. Obtained energy consumptions for the optimum generation of chlorine dioxide were 1.38, 1.03 and $1.61W{\cdot}hr/g-ClO_2$, respectively.