• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.322-328
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• 1995

A thermophilic bacteria showing proteolytic activity against defatted soybean was isolated from soil. It was identified as Bacillus amyloliquefaciens based on its morphological and physiological characteristics. The Bacillus amyloliquefaciens NS 15-4 was cultivated at 50$\circ$C by rotary shaking in a medium containing defatted soybean. An extracellular protease from this strain was purified to homogeneity by ammonium sulfate precipitation, ion exchange, and hydrophobic interaction chromatographies. The molecular weight of the enzyme was estimated to be approximately 30,000 by SDS-PAGE and the N-terminal amino acid sequence of the enzyme was turned out to be AQSVPYGISQIKAPA. The optimum temperature and pH for the enzyme reaction were 60$\circ$C and 11, respectively, and its thermostability was increased by the addition of calcium ion. The enzyme was inactivated by phenylmethylsulfonylfluoride, suggesting it be a serine protease. Comparing with other commercial proteases, the enzyme showed relatively high proteolytic activity against defatted soybean, a water-insoluble protein substrate.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.57-71
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• 1985

The characteristics of compaction and unconfined compressive strength were investigated by mixing with lime to all soils adjusted by given percentages of two kinds of clays to sand to obtain the most effective distribution of grain size and the optimum lime content for soil stabilization. In addition, unconfined compressive strength and durability tested by adding of sodium metasilicate, sodium sulfate, sodium carbonate, sodium gydroxide and magnesium oxide to lime-soil mixture mixed with 8 percent lime to adjusted soil having the mixing percentage of 60 percent of cohesive black clay and 40 percent of sand by weight to get the effect and the optimum content of chemicals. The results obtained were as follows; 1.With the addition of more lime, the optimum moisture content was increased, and the maximum dry density was decreased, whereas the more the amount of clay and the less was the maximum drt density. 2. In the soil having more fine grain size the unconfined compressive strength was larger in the earlier stage of curing period, in accordance with the longer period, the mixing percentages of sand to clay showing the maximum unconfined compressive strength, on the basis of 28-day strength, were 60% : 40% (black clay) and 40% : 60% (brown clay) respectively. 3. The reason why the soil adjusted with black clay was remarkably bigger in the unconfined compressive strength than ones adjusted with brown clay for all specimen of lime-soil mixture was the difference in the kind of clay, the amount of chemical compositions the value of pH. Black clay was mainly composed of halloysite that reacted with lime satisfactorily, whereas the main composition of brown clay was kaolinite that was less effect in the enhance of unconfined compressive strength. Also the difference of unconfined compressive strength was because black clay was larger in the amount of composition of calcium oxide and magnesium oxide in the value of pH affecting directly on the unconfined compressive strength of lime-soil mixture than brown clay. 4. In the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40%, on the standard of 7-day strength, the effect of chemical was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium hydroxide and sodium metasilicate. 5. The optimum amount of chemical being applicable to the maximum unconfined compressive strength of lime-chemical-soil mixture was 1 percent by weight for air dry soil in the case of adding sodium carbonated and 0.75 percent on sodium hydroxide, the unconfined compressive strength was increased continuously with increase of the amount of chemical up to 2 percent of chemical content is the lime-chemical-soil mixture added sodium metasilicate, sodium sulfate and magnesium oxide. 6. It was considered that the chemical played and accelerant role of early revelation of strength because the rate of increase of unconfined compressive strength of all of lime-chemical-soil mixtures was largest on the 7-day cured specimen. 7. The effect of test on freezing and thawing after adding suitable amount of chemical on the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40% was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium metasilicate and sodium hydroxide.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.1
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• pp.39-44
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• 1989

This experiment was conducted to mature newly reclaimed upland and to increase soybean yield at this upland, Kim Jae, Jeon Buk, Koera from 1987 to 1988. Lime, lime-magnesium and calcium sulfate were applied with two, levels, amount of lime requirement, and 1.5 times of lime requirement. The results were summarized as follows: 1. The yields of soybean among treaments were in order of lime-magnesium 1.5 times, lime 1.5 times, lime-magnesium, calcium sulfate, lime and control with significancy at 1% level. 2. Correlations between yield components and inorganic element contents (T-N, $P_2O_5$, CaO and MgO) in plant at flowering stage were positive, but manganese in plant was negative at 5%, respectively. 3. Correlations, between yields and MgO and CaO contents in plant at flowering stage were positive, but Mn in plant was negative at 5% respectively. 4. Inorganic element contents of the soils at flowering stage were higher than those of before experiment. Correlation between yield and base saturation degree in soil at flowering stage was positive at 5%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.154-159
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• 2019

The glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system was fabricated by using yttrium oxide and iron oxide that it can reduce the melting temperature and affect the homogenization. Zirconium sulfate was used as a nucleation agent. Calcium phosphate was used to improve the flow the glass so as reduce the viscosity of the glass. The glass-ceramics met a thermal shock test of more than $750^{\circ}C$ and the temperature at which the coefficient of thermal expansion rapidly increased at over $800^{\circ}C$ was shifted by about the above $30^{\circ}C$. Therefore, it is concluded that the glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system with yttrium oxide and iron oxide was founded to have good melting conditions and excellent thermal expansion resistance at high temperature such as special field for kitchen utensils.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.561-568
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• 2022

In this study, the mechanical properties and self-healing performance of cement mortar containing clinker binder, calcium sulfoaluminate(CSA), and sodium sulfate(Na₂SO₄) were evaluated. The mechanical properties of cement mortar were investigated by measuring compressive strength and flexural strength, and the healing performance was evaluated through hydrostatic water permeability test and gas diffusion test. In addition, the healing products precipitated in the cracks were visually observed through an optical microscope and a scanning electron microscope(SEM). As a result, the incorporation of the clinker binder-based inorganic additives improved the initial and 28-day strength by about 20 %. Depending on the healing performance evaluation method, there was a difference in the healing rate, and the healing rate showed a tendency to be underestimated. Nevertheless, CaCO₃ was precipitated as the main healing product inside the 0.3 mm crack when the inorganic additives were mixed with cement mortar, improving the self-healing performance.

• Advances in concrete construction
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• v.6 no.4
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• pp.345-362
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• 2018

In this paper, mechanical and short-term durability properties of fly ash and slag based geopolymer concretes (FAGPC-SGPC) were investigated. The alkaline solution was prepared with a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) for geopolymer concretes. Ordinary Portland Cement (OPC) concrete was also produced for comparison. Main objective of the study was to examine the usability of geopolymer concretes instead of the ordinary Portland cement concrete for structural use. In addition to this, this study was aimed to make a contribution to standardization process of the geopolymer concretes in the construction industry. For this purpose; SGPC, FAGPC and OPC specimens were exposed to sulfuric acid ($H_2SO_4$), magnesium sulfate ($MgSO_4$) and sea water (NaCl) solutions with concentrations of 5%, 5% and 3.5%, respectively. Visual inspection and weight change of the specimens were evaluated in terms of durability aspects. For the mechanical aspects; compression, splitting tensile and flexural strength tests were conducted before and after the chemical attacks to investigate the residual mechanical strengths of geopolymer concretes under chemical attacks. Results indicated that SGPC (100% slag) is stronger and durable than the FAGPC due to more stable and strong cross-linked alumina-silicate polymer structure. In addition, FAGPC specimens (100% fly ash) showed better durability resistance than the OPC specimens. However, FAGPC specimens (100% fly ash) demonstrated lower mechanical performance as compared to OPC specimens due to low reactivity of fly ash particles, low amount of calcium and more porous structure. Among the chemical environments, sulfuric acid ($H_2SO_4$) was most dangerous environment for all concrete types.

• Analytical Science and Technology
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• v.30 no.4
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• pp.182-193
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• 2017

In order to examine the variation characteristics of chemical compositions in relation to the inflow pathways of Asian dust, $PM_{10}$ and $PM_{2.5}$ aerosols were collected at Gosan site of Jeju Island during the Asian dust days between 2010 and 2015, and their chemical compositions were analyzed. The mean mass concentrations of $PM_{10}$ and $PM_{2.5}$ during Asian dust days were $130.0{\pm}90.2$ and $38.2{\pm}24.7{\mu}g/m^3$, respectively. The composition ratios of major secondary pollutants ($nss-SO_4{^{2-}}$, $NH_4{^+}$, $NO_3{^-}$) were high as 53.7 % for $PM_{10-2.5}$ and 90.6 % for $PM_{2.5}$. When the Asian dusts had been transported to the Korean Peninsula via Loess Plateau of central China, the concentrations of $nss-Ca^{2+}$, $NH_4{^+}$, $nss-SO_4{^{2-}}$, and $NO_3{^-}$ increased more noticeably. Whereas in case when the inflow pathways of Asian dust had been through the Bohai bay, the concentrations of the crustal species such as Al, Fe, and Ca were relatively high in coarse particles. The atmospheric aerosols were acidified largely by sulfuric and nitric acids. They were neutralized mainly by calcium carbonate in coarse particle mode passed through Manchuria area, but by ammonia in fine particle mode passed through Loess plateau and Bohai bay. Ammonium salts are assumed to exist as ammonium sulfate and ammonium nitrate in coarse particles, but mostly as ammonium sulfate in fine particles.

• Applied Biological Chemistry
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• v.48 no.4
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• pp.311-314
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• 2005

Approximately twelve hundred strains of Actonomycetes isolated from domestic soli were tested for their ability to produce extracellular phytase. Of all these isolates a strain, YB-26, that had the highest potential for phytase activity was chosen. The nucleotide sequence of 16S rDNA of the isolate YB-26 showed the highest similarity to that of strains beloning to genus Streptomyces. The partially purified extracellular phytase was obtained from the culture filtrate of Streptomyces sp. YB-26 grown on GSM broth by ammonium sulfate precipitation (15-70%), DEAE-Sepharose column and Q-Sepharose column chromatography. The partially purified enzyme showed the maximum activity for hydrolysis of phyate at $60^{\circ}C$ and pH 7.0, and retained 90% of its maximum activity at the range of pH $6.0{\sim}8.0$. It was thermolabile and its thermostability did not increase in the presence of calcium chloride.

• Applied Biological Chemistry
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• v.1
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• pp.34-36
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• 1960

Riboflavin and protein fortified, fermented feed were prepared by cultivating koji mold of riboflavin producibility on sweet potato starch waste with addition of ammonium sulfate. Progressive riboflavin and protein yield were obtained in the feed with additive amount of ammonium sulfate up to 4%. The effect was further enchanced by mixing 1/4 amount of wheat bran and $2{\sim}3%$ calcium superphosphate with starch waste. The best fermented feed were fortified with 15% protein and 2.2 mg % of riboflavin while the starch content was decreased to 13%. The amino acid composition of mold body was studied.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.3
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• pp.191-197
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• 1992

In order to investigate the chemical components of acid precipitation at Kangwha near the Yellow Sea and Seoul in Korea, the precipitation samples were collected by wetonly precipitation sampler from February 1991 to January 1992, and pH, electric conductivity(E. C.) and major water-soluble ionic components were analyzed. Strong negative linear correlations were observed between the rainfall amount and the sum of major ionic components in $\mu eq/\ell$ at two sites. The sum of major ionic components also correlated negatively with rain intensity. The analytical results of precipitation samples at two sites were compared each other. Average values of volume-weighted pH were found to be 5.21 at Kangwha and 5.09 at Seoul. The cationic abundance($\mu eq/\ell$) in rainwater showed the general trend $NH_4^+ > Na^+ > Ca^{2+} > Mg^{2-+} > H^+ > K^+$ at Kangwah and $NH_4^+ > Ca^{2+} > Na^+ > H^+ > Mg^{2+} > K^+$ at Seoul. The anionic abundance showed the general trend $SO_4^{2-} > Cl^- > NO_3^-$ at Kangwha and $SO_4^{2-} > NO_3^- > Cl^-$ at Seoul. The concentrations of seasalt such as $Na^+ and Cl^-$ were higher at Kangwha than Seoul. The concentrations of $nss-SO_4^{2-}, nss-Cl^- and NO_3^-$ which are acid composition were higher at Seoul(96.3 $\mu eq/\ell$) than Kangwha(69.0 $\mu eq/\ell$). The contribution of seasalt to the composition of precipitation were higher at Kangwha(34.1%) than Seoul(15.7%). Ammonia and calcium species in rainwater at Kangwha and Seoul are interpreted to have 91% of neutralizing capacity of the original sulfuric and nitric acids. Provided that the precipitation acidity originates primarily from sulfate and nitrate, sulfate was found to contribute about 73-75% of the free precipitation acidity.