• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.371-374
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• 2005

In this study, calcium chloride($CaCl_2$), sodium chloride (NaCl), organic acids-containing deicer(NS 40, NS 100), mixed deicier($NaCl\;70\%\;+\;CaCl_{2}\;30\%,\;NS\;40\;70\%\;+\;CaCl_{2}\;30\%,\;NaCl\;70\%\;+\;NS\;40\;30\%,\;NS\;40\;70\%\;+\;NaCl\;30\%$) is investigated based on the laboratory test for deicing performance. Test items for deicing performance were ice melting and ice penetration, freezing point depressions and eutectic points, pH, thermal properties for selected deicing chemicals. As a test results, in case of the use chloride-containing deicier in area that concrete structures has subjected to freez-thaw reaction in winter season, it showed desirable method that use deicing chemicals mixed with optimum ratio rather than use one deicing chemicals when is consider to deicing performance and effects, corrosion of steel materials, freez-thaw resistance of concrete. When use various deicing chemicals mixed, NS40($70\%$)+Calcium chloride($30\%$) showed the best effective method.

• Magazine of the Korea Concrete Institute
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• v.5 no.1
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• pp.129-138
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• 1993

프리텐션 방식 원심력 고강도 콘크리트 말뚝[KS F 4306]제조에 관한 실험적 연구로써 고황산염시멘트를 이용한 800kg/$ extrm{cm}^2$이상의 고강도콘크리트 제조시 수화 특성검토와 콘크르트 조직내의 기공율과 압축강도간의 상관식을 도출하여 고강도 발현기구를 규명하였으며 콘크리트 압축 및 휨강도간의 상관식 유도와 내구성 측면에서의 내동해성, 건조수축, 화학저항성등을 보통 포틀랜드 시멘트와 비교 고찰한 결과, 고황상염시멘트의 내구성이 우수함을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.491-499
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• 1997

High flexible lightweight composites containing tobermorite as a main mineral is produced using various amorphous silicates, lime, cement and fibers. Here, Mechanical properties of the composites were studied by observing microstructures of hydrates and fibers. Amorphous silicates having better hydraulicity retarded the crystallization of tobermorite due to better formation of C-S-H gel in water bath curing, but, difficult conversion from C-S-H gel to tobermorite in hydrothermal reaction. In the low molar ratio of CaO/SiO2 (0.67), faster crystalization was observed dued to more impurities such as Al2O3 alkali, resulting in improving mechanical properties due to small crystal size and many contact points. It was identified that a lot of calcium silicate hydates formed at surface of pulps increase bonding strength and the crack-resistance of matrix in the composites, but decrease hardness and compressive strength. The choice of amorpous silicates having better hydraulicity, low CaO/SiO2 adding each fibers bellow about 5% in the raw mixs and lower molding pressure should be needed at improve mechanical properties of composites.

• The Korean Journal of Food And Nutrition
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• v.2 no.2
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• pp.14-20
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• 1989

A strain of Saccharomyces cerevisiae BY-366 was isolated to produce a strong sucrose-hydrolyzing enzyme. After entrapment of yeast cell invertase with alginate, enzymatic properties of immobilized cells were investigated. The results are as follows. 1. The optimum pH of invertase in immobilized cells and non- immobilized cells was 6.0 and 5.0, and pH stability of invertase in immobilized cells and non- immobilized cells was 6.0 and 5.0, respectively. 2 Activation energy of immobilized cells was 4.7 kcal/mol. 3 The immobilized preparation exhibited high resistance to heat and urea Induced denaturation. 4, The bead size less than 2 mm in diameter was desirable. 5. In spite of repeated use, the enzyme activity of immobilized cells was inhibited slightly in batch reaction, and a small column of the immobilized preparation could hydrolyze relatively high concentration of sucrose almost quantitatively to more than 6 days.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.151-152
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• 2020

When concrete is exposed to fire, the thermal decomposition of hydrates of Portland cement paste results in critical damage to the concrete structure of a building. Recently, nanosilica arose as the effective nano-additive which can enhance the thermal resistance of the cementitious materials. However, the mechanism of the enhancement was not elucidated specifically. In this study, we investigated the properties of calcium silicate hydrates(C-S-H)of the nanosilica incorporated cement paste after heating to different heating temperatures (200℃, 500℃, and 800℃) by 29Si nuclear magnetic resonance. The results showed that the polymerization of C-S-H of nanosilica incorporated samples was larger than ordinary cement paste after heating to 200℃, and C-S-H formed during heating process to 500℃ due to the pozzolanic reaction during heating process.

• Membrane Journal
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• v.18 no.1
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• pp.7-25
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• 2008

Sodium dodecyl sulfate, which was anionic surfactant, at a concentration higher than its critical micellar concentration was added to calcium solution for forming micelles. Then aggregates were formed by adsorption or binding of calcium ions on the surface of micelles, and gathering between them, and then rejected by two kinds of ceramic membranes to remove calcium ions. As result, rejection rates of calcium were higher than 99.98%. And in our experimental range the higher TMP trended to increase the resistance of membrane fouling ($R_f$), total permeate volume ($V_T$), dimensionless permeate flux ($J/J_o$) and permeate flux (J) because TMP was driving force. And we investigated effects of $N_2$-back-flushing time and filtration time, that was back-flushing period, during periodic $N_2$-back-flushing on ceramic membranes. As result, optimal BTs for NCMT-623l ($0.07{\mu}m$ pore size) and NCMT-7231 membrane ($0.10{\mu}m$) were 10 sec and 15 sec, respectively. Also, optimal FT was 5 min for both membranes, and the frequent $N_2$-back-flushing could decrease membrane fouling effectively. Then, the optimal conditions resulting from our experiments for synthetic calcium solution were applied to groundwater using as washing process of soymilk package. As result, rejection rates of calcium were higher than 99.98%.

• Clinical and Experimental Pediatrics
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• v.60 no.7
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• pp.216-220
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• 2017

Purpose: Vitamin D is associated with various pathological conditions such as cardiovascular diseases and cancer. We investigated the relationship between vitamin D and Kawasaki disease (KD). Methods: We performed a retrospective review of the medical records of patients with KD between February 2013 and March 2016 in Daegu Fatima Hospital. Study participants were grouped according to vitamin D serum concentration. Group 1 included patients with 25(OH)-vitamin D ${\geq}20ng/mL$. Group 2 included patients with 25(OH)-vitamin D <20 ng/mL. We analyzed the clinical characteristics and laboratory data of the 2 groups. Results: Of the 91 patients, 52 were included in group 1, and 39 in group 2. Group 1 patients had significantly higher levels of calcium, phosphate, albumin and sodium than group 2 patients did. There were no differences in clinical characteristics, but the proportion of patients with polymorphic rash was significantly higher in group 2. Resistance to intravenous immunoglobulin was more frequent in group 2 (P=0.023). No significant difference in the incidence of coronary artery complications was observed. Conclusion: Low vitamin D levels are associated with resistance to intravenous immunoglobulin therapy in KD. Vitamin D deficiency might be a risk factor for immunoglobulin resistance in KD.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.61-70
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• 2019

Geopolymer is an eco-friendly construction material that has various advantages such as reduced $CO_2$ emission, fire resistance and low thermal conductivity compared to cement. However, it has not been many studies on the thermal behavior of the surface of the geopolymer panel when flame is applied to the surface. In this study, surface characteristics of hardened geopolymer on flame exposure was investigated to observe its characteristics as heat-resistant architectural materials. External structure changes and crack due to the heat shock were not observed during the exposure on flame. According to the residue of calcite and halo pattern of aluminosilicate gel, decarboxylation and dehydration were extremely limited to the surface and, therefore, it is thought that durability of hardened geopolymer was sustained. Gehlenite and calcium silicate portion was inversely proportional to quartz and calcite and significantly directly proportional to BFS replacement ratio. Microstructure changes due to the thermal shock caused decarboxylation and dehydration of crystallization and it was developed the pore and new crystalline phase like calcium silicate and gehlenite. It is thought that those crystalline phase worked as a densification and strengthening mechanism on geopolymer panel surface.

• Archives of Plastic Surgery
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• v.33 no.3
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• pp.324-329
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• 2006

The silicone rubber implants are widely used in plastic surgery because of various advantages; however, calcification in surface of implant(as a chemical resistance) may transform or destroy the high molecular biomaterial when it stays too long within the human body. The purpose of this study is to determine the relationship between calcification and the histological disparities of the tissues surrounding the area adjoining the silicone nasal implant by examining the regional characteristics of calcium deposits in the silicone nasal implant via elemental analyses using EDX(energy-dispersive X-ray analysis) and ultrastructural analyses using SEM(scanning electron microscopy). The subjects of the study were 19 silicone nasal implants removed by revision rhinoplasty, all displaying calcification. According to the tissue characters, the implant surface was divided into 4 zones with the rhinion as the basis. For each zone, elemental and ultrastructural analyses were performed. Elemental analysis revealed that the calcium deposits consisted of Ca and P only. There were no statistically significant disparities among the ratios between Ca and P according to the zones. Ultrastructural analysis showed acellular mineral-like deposits coalesced to create amorphous deposits in all zones; however, in zones 1 and 3(more pressurized zones by periosteum or nasal bone), additional flaky cylinder-shaped calcium deposits were detected. Thus, it seems that the histological disparities in the surrounding tissues do not affect the components and their proportions in the calcification process. However, it can be inferred that the physical environment due to the histological disparities in the surrounding tissues affects the ultrastructures of calcium deposits.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.78-85
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• 2020

Shotcrete concrete is generally used in the form of ready-mixed concrete products using type I ordinary portland cement(hereinafter referred to as OPC) and about 5% of accelerator mixed separately in the field. In this study, we tested the effect of OPC fineness and SO₃ content on a penetration resistance, compressive strength of binder for shotcrete using calcium aluminate type accerlerator. And we analysed hydrates and pore structure effects on mortar performance. In the future, it is expected to be useful for manufacturing optimized OPC as a binder for shotcrete.