• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.52-59
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• 2014

This study examines the compressive strength, elastic modulus and splitting tensile strength of geopolymer concrete in order to evaluate its mechanical characteristics according to the admixing of fly ash and blast furnace slag. Moreover, identical tests are also conducted considering the amount of powder, the mixing ratio of alkali activator and the mixing ratio of silica fume for further comparative analysis considering various variables. The comparison with the formulae specified in Korean and overseas codes reveal that a mixing ratio of 18% is adequate for the alkali activator and that a replacement ratio of 5% by silica fume is recommended for silica fume. The elastic modulus of the geopolymer concrete appears to increase slightly with the increase of the compressive strength per variable and age and to be smaller than the values predicted by the formulae specified in Korean and overseas codes. In addition, the examination of the stress-strain curves shows that the geopolymer concrete exhibits ductile behavior compared to the conventional OPC. In view of the splitting tensile strength, high strength is observed for a powder content of $400kg/m^3$ and a replacement ratio of 18% by silica fume. The resulting ratio of the compressive strength to the splitting tensile strength is seen to range between 8.7 and 10.2%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.10
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• pp.1572-1578
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• 2005

Response surface methodology was used for monitoring changes in physicochemical properties with heating condition of ginseng which was sliced and freeze-dried. As heating temperature and time increased, soluble solid content decreased and browning color increased. Also, acidic polysaccharide and total phenolics increased with the increase in heating temperature and time. Heating condition for maximum soluble solid content was 146.05$^{\circ}C$ in heating temperature and 18.16 min in heating time. Maximum value of crude saponin content was 64.40 mg/g in 160.00$^{\circ}C$ and 20.00 min. Crude saponin content was influenced by heating time but the other properties were influenced by heating temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.7
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• pp.953-959
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• 2003

This study examined physicochemical properties of two waxy rice starches, shinsun and black rice starches. Proximate compositions of both samples were similar. The major minerals in the shinsun rice starches were Ca, Mg, P and Na, whereas those in black rice starches were Ca, P, Fe and Mg. The major particle size of shinsun rice starch was 6.97 micron and that of black rice starch was 6.27 micron. In iodine reaction, maximum absorbance wavelength (λmax) and absorbance at 625nm of black rice starch were higher than those of shinsun rice starch. Intrinsic viscosity of black rice starch (183mL/g) was higher than that of shinsun rice starch (178 mL/g). Water binding capacity was similar in both samples. Swelling power and solubility of black rice starch were lower than those of shinsun rice starch. X-ray diffraction patterns of all samples showed traditional A type of cereals as shown peaks at 15.2 (15.0), 17.2 (17.15), 18.05 (17.95), 23.25 (23.15)$^{\circ}$. The common shape of SEM was observed in both waxy rice starches.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.5
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• pp.616-621
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• 2007

In order to improve the storage stability of steamed bread, fermented pine needle extract syrup potentially with several functional properties was added in manufacturing the products at levels of 8.3, 11 and 18% based on Brix degree of the dough. The manufactured bread was stored at ambient conditions and measured for quality attributes. Dough added with the fermented pine needle extract syrup maintained its pH and water activity at levels of $5.45{\sim}5.90\;and\;0.94{\sim}0.96$, which are normally suitable for yeast fermentation and for appropriate dough hardness. Addition of the extract syrup increased the bread volume by more than 20%. The bread with higher content of the pine needle extract syrup showed slower increase of bread hardness during storage, suggesting retardation of bread retrogradation. The addition of the pine needle extract syrup in bread dough also inhibited growth of the aerobic bacteria and molds on the bread surface (by $0.8{\sim}24$ in log (CFU/g) at 4 day storage). Use of higher than 11% concentration presented initially a strong fine needle flavor to the bread, which disappeared soon after 2 days. Generally addition of the pine needle extract syrup did not give negative effects on the bread quality including sensory quality. Therefore, the addition of the needle extract syrup could contribute to improving the storage stability and extending the shelf life of the bread.

• Environmental and Resource Economics Review
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• v.24 no.3
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• pp.523-549
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• 2015

This paper investigates an oil refiner's asymmetric behavior in the adjustments of gasoline and diesel prices to changes in his own price and his rivals' prices as well as input costs. An asymmetric error correction model which allows a firm's pricing behavior to the deviation of other firms' prices from their long-run equilibrium level is employed for estimation using weekly data for the period April 2009 to January 2015. Evidence is found that there is a significant degree of asymmetry in the adjustment of wholesale prices to changes in crude oil price. A similar result in regard to the exchange rate is also found by the data. The estimation results for firm's response to changes in other firms' prices indicates that implicit collusion could be more easily exploited in the wholesale petroleum market as results of firms' interaction with each other and anticipation of rivals' pricing behavior. A few refiners show competitive price adjustment in response to the upward deviation of the others' prices from their equilibrium level.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.97-106
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• 1996

Macroalgal community was analysed from December 1993 to October 1994 in Yonggwang vicinity, western coast of Korea. A total 51 species (12 green, 11 brown and 29 red algae) of marine algae were identified. Among four localities, the number of species observed was the highest as 34 species at Shimwon and the least as 31 species at Sunchanggum and Gamakdo. Seasonally, the number of species observed was the highest as 42 species in winter and the least as 18 species in summer. The species showing relatively high important value were Enteromorpha compressa, Sargassum thunbergii, Corallina pilulifera and Carpopeltis affinis, which were all common to four investigated localities. Seasonal and regional fluctuations of mean biomass was $66.0\~820.0\;g-wet\;wt/m^2$ at Hyanghado, $248.3\~886.3\;g-wet\;wt/m^2$ at Sunchanggum, $154.5\~510.2\;g-wet\;wt/m^2$ at Gamakdo and $85.0\~451.9\;g-wet\;wt/m^2$ at Shimwon, respectively. The flora investigated could be classified into six functional groups such as coarsely branched form $(41.2\%)$, sheet form $(25.5\%)$, filamentous form $(19.6\%)$, thick leathery $(7.8\%)$, crustous form $(3.9\%)$ and jointed calcarious form algae $(2.0\%)$. At the effluent area of the nuclear power plants, the algal composition of functional groups may affect species composition due to thermal pollution.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.335-340
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• 1996

A green house experiment was conducted to investigate the growth of Chinese cabbage, radish and soybean and change in the chemical properties of the soil after the 10mm application of the simulated acid rain(SAR) of pH 2.7 in the form of sprinkle and mist. It was applied 30 times for Chinese cabbage and radish and 62 times for soybean at the two-day intervals. The results obtained are summarized as follows: 1. Visual damages caused by SAR were dark-brown or red brown leaf spots in Chinese cabbage, and dark-brown and wrinkled leaf margins in radish and soybean. 2. The degree of visual damages became severer as the number of SAR applications increased and it was severer with mist than with sprinkle of SAR. 3. Chlorophyll content was reduced by SAR, but it was not affected by the form of SAR application(sprinkle or mist) in all crops, although it was slightly lower with mist than with sprinkle of SAR. 4. Fresh weight of Chinese cabbage heads and radish roots and grain yield of soybean were reduced by SAR, and were not affected by the form of SAR application. 5. Contents of K, Ca, and Mg in leaves were reduced, while S content increased by SAR in all crops. The forms of SAR application did not affect contents of mineral nutrients in all crops. 6. SAR decreased soil pH and the contents Ca, Mg, and K of soil, while increased $SO_4$ content. However, the contents of soil organic matter, N, and P were not affected by SAR. Forms of SAR application did not affect soil chemical properties either.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.341-347
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• 1996

A green-house experiment was conducted to investigate the growth of Chinese cabbage, radish, and soybean and changes in soil chemical properties after application of 5 and 10mm of pH 2.7 simulated acid rain(SAR) followed by 0, 5, and 10mm of pH 6.0 normal water at the three-day intervals 20 times for Chinese cabbage and radish and 42 times for soybean. The results obtained are summarized as follows: 1. Visual damages by SAR were white-yellow leaf spots, dark brown or light green leaf color, and wrinkled leaf margins in all crops. The degree of visual damages was severer at 10mm than at 5mm SAR and it was reduced as the amounts of normal water increased after SAR application. 2. Chlorophyll content was higher at 10mm than at 5mm SAR application and increased as the amounts of normal water increased after SAR application in all crops. 3. Fresh weights of Chinese cabbage heads and radish roots and grain yield of soybean were higher at 10mm than at 5mm SAR, while they increased as the amounts of normal water increased at the same SAR level. 4. Changes in the mineral contents of plants were not consistent, while S content in radish and soybean increased as the amounts of SAR increased. 5. SAR lowered soil pH, while it increased soil N and S contents. Contents of soil organic matter, P, and exchangeable Ca, Mg, and K were not affected by the amounts of SAR.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.3 no.2
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• pp.25-31
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• 1996

Various treaments such heating, acid tenting, acid healing, alkaline treating, acid+alkaline renting were attempted to investigate their effects on molar ratio, chemical composition, DTA and specific surface area(SSA) of natural zeolite poder. Molar ratio, Si to AI. of natural zeolite was 4.78, which represented high silica type. Composition of natural zeolite showed that $SiO_2$ was 66.34% $Al_2O_3$ was 13.89%, $Fe_2O_2$ was 1.55% X-ray diffraction showed that main component of natural zeolite was mordenite and clinoptliolite. Differential Thermal Analysis and Thermogravimetry curve of natural zeolite was showed to peak of endothermic peak at $80^{\circ}C$ and it means to the peak of dehydrate reaction, but recristalization was not formed below at $1,000^{\circ}C$. Weight loss during calcination was 16% at $1,000^{\circ}C$. Thermal treatments on SSA of natural zolite powder decreased from $75.2m^2/g\;to\;2.1m^2/g$. In contrast chemical treatments on SSA showed to increase to $300.2m^2/g$(1 N HCl treating), $54.9m^2/g$(1 N NaOH) and $90.9m^2/g$(HCl+NaOH)tudy, it could be proposed to employ acid tret method as packaging materisls for MA packaging.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.15 no.2
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• pp.43-47
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• 2009

Respiration and quality of persimmon fruits were monitored through the storage at 0, 5, 15 and $25^{\circ}C$. Respiration rate data at different temperatures were used for determining the $O_2$ and $CO_2$ permeabilities required to maintain the optimal package atmosphere (1~3% $O_2$, 4~7% $CO_2$). The estimated gas permeabilities were then compared to those of available plastic films for examining their potential application at various temperature conditions. $O_2$ consumption and $CO_2$ production were at similar order and leveled at stable value after initial time span with higher rates measured at higher temperatures. Major quality indexes during storage were observed to be ascorbic acid content change and firmness destruction with the most significant changes at $25^{\circ}C$ Higher $O_2$ and $CO_2$ permeabilites were required at higher temperatures, and common plastic films were shown to be unable to satisfy those requirements. Films or devices of high permeation property such as silicone rubber or microporous film may be combined to increase the permeation properties satisfying the required high gas permeabilities.