• 한국세라믹학회지
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• 제46권1호
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• pp.24-29
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• 2009

The suspension of $Al_2O_3$ which has long-term stability was made by mechanical milling. Thin films were evaluated and made to use as coating materials. A particle size of the suspension manufactured was 98 nm when 2 mt% nitric acid was added. It indicated that viscosity of the suspension is 12 cps and that it had the long-term stability. Thickness which was from 200 nm to 600 nm of the thin films was able to be made by adjusting draw rate and organic additive. Cracks of thin films at room temperature were prevented by adding Ethyl cellulose from 0.5 wt% to 2 wt%. The thin film heated at $500^{\circ}C$ indicated a hydrophilic property against water and an excellent permeability against a visible ray.

• KSBB Journal
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• 제27권6호
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• pp.352-360
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• 2012

Bacillus clausii I-52 which produced SDS- and $H_2O_2$-tolerant extracellular alkaline protease (BCAP) was isolated from heavily polluted tidal mud flat of West Sea in Incheon, Korea and stable strain (transformant C5) of B. clausii I-52 harboring another copy of BCAP gene in the chromosome was developed using the chromosome integration vector, pHPS9-fuBCAP. When investigated the production of BCAP using B. clausii transformant C5 through pilot-scale submerged fermentation (500 L) at $37^{\circ}C$ for 30 h with an aeration rate of 1 vvm and agitation rate of 250 rpm, protease yield of approximately 105,700 U/mL was achieved using an optimized medium (soybean meal 2%, wheat flour 1%, sodium citrate 0.5%, $K_2HPO_4$ 0.4%, $Na_2HPO_4$ 0.1%, NaCl 0.4%, $MgSO_4{\cdot}7H_2O$ 0.01%, $FeSO_4{\cdot}7H_2O$ 0.05%, liquid maltose 2.5%, $Na_2CO_3$ 0.6%). The enzyme stability of BCAP was increased by addition of polyols (10%, v/v) and also, the stabilities of BCAP towards not only the thermal-induced inactivation at $50^{\circ}C$ but also the SDS and $H_2O_2$-induced inactivation at $50^{\circ}C$ were enhanced. Among the polyols examined, the best result was obtained with propylene glycol (10%, v/v). The BCAP supplemented with propylene glycol exhibited extreme stability against not only the detergent components such as ${\alpha}$-orephin sulfonate (AOS) and zeolite but also the commercial detergent preparations. The granulized enzyme of BCAP was prepared with approximately 1,310,000 U/g of granule. Wash performance analysis using EMPA test fabrics revealed that BCAP granule exhibited high efficiency for removal of protein stains in the presence of anionic surfactants as well as bleaching agents. When compared to Savinase 6T$^{(R)}$ and Everlase 6T$^{(R)}$ manufactured by Novozymes, BCAP under this study probably showed similar or higher efficiency for the removal of protein stains. These results suggest that the alkaline protease produced from B. clausii transformant C5 showing high stability against detergents and high wash performance has significant potential and a promising candidate for use as a detergent additive.

• Asian Pacific Journal of Cancer Prevention
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• 제17권8호
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• pp.4063-4070
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• 2016

Background: Cytochrome P450 2E1 (CYP2E1) and catechol-O-methyltransferase (COMT) genes may contribute to susceptibility to lung cancer because of their critical involvement in mechanisms of carcinogenesis. Materials and Methods: We evaluated the role of CYP2E1 rs2031920 and COMT rs4680 in a case-control study involving 462 lung cancer cases and 379 controls in Japanese. Logistic regression was used to assess adjusted odds ratios (OR) and 95% confidence intervals (CI). Multiplicative and additive interactions with cigarette smoking or alcohol use were also examined. Results: Neither CYP2E1 rs2031920 nor COMT rs4680 was associated with lung cancer risk overall. However, smokers with the CC genotype of CYP2E1 rs2031920 (OR = 3.57, 95% CI = 2.26 - 5.63) presented a higher risk of lung cancer than those with at least one T allele (OR = 2.91, 95% CI = 1.70 - 4.98) as compared to never-smokers with at least one T allele (reference). Subjects with excessive drinking and the CC genotype of CYP2E1 rs2031920 had a significantly higher risk (OR = 2.22, 95% CI =1.39 - 3.56) than appropriate drinkers with at least one T allele. A similar tendency was observed between COMT rs4680 and either smoking or drinking habits. There were no multiplicative or additive interactions between the polymorphisms and either smoking or alcohol use. Conclusions: Our findings indicate that CYP2E1 rs2031920 and COMT rs4680 are not major contributors to lung cancer risk in our Japanese population. Future studies on the genetics of lung cancer in Japanese and their environment interactions are required.

• 폴리머
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• 제32권5호
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• pp.465-469
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• 2008

블록 공중합체의 자기조립현상과 졸-겔 공정을 결합하여 나노크기 수준에서 다양한 형태를 발현하는 블록공중합체-이산화티타늄 하이브리드 박막의 모폴로지를 제조하였다. 모폴로지 변화를 일으키는 요소로서 블록 공중합체의 조성, 용매의 선택성과 첨가제에 의한 영향을 고려하였으며, 모폴로지 변화에 따른 이산화티타늄의 발광 효율 변화 또한 확인하였다. 폴리스티렌-폴리4비닐피리딘 이중블록공중합체는 용매와 두 블록간의 상대적인 친화성에 따라 미셀과 나노선 형태로 자기조립이 가능하며, 이산화티타늄의 전구체인 티타늄 테트라아이소프로폭시드는 폴리4비닐피리딘블록의 질소 원소와 결합한다. 블록 공중합체/졸-겔 전구체 혼합 용액에 제3의 성분인 3-펜타데실페놀을 첨가하면 블록의 상대적인 부피 비율의 변화를 야기하여 모폴로지 변화를 일으킨다. 다양하게 변화하는 모폴로지에서 이산화 티타늄의 형광 효율이 변화함을 확인하였다.

• 전기화학회지
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• 제6권4호
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• pp.242-249
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• 2003

아연 전극은 고농도의 KOH전해질 용액의 알카리 전지용 양극재료로 폭넓게 이용되고 있다. 그러나 급속한 전기화학적 반응과 높은 용해도에 의한 수지상의 생성에 의해 사이클 수명이 현저하게 짧아지는 것으로 알려져 있다. 본 연구에서는 용액온도 $25^{\circ}C$의 $40wt.\%$ KOH 전해질에 $Ca(OH)_2$, Citrate, Tartrate 및 Gluconate 등의 첨가제를 첨가하고 그리고 $Pb_3O_4\;5wt\%$를 아연 전극에 혼합하였을 때 아연 전극의 전기화학적 거동에 미치는 Pb,04와 첨가제의 효과를 동전위 분극 곡선, 순환전위전해분석법, 가속수명시험 및 SEM사진 분석을 통하여 고찰하였다. $Pb_3O_4$의 첨가는 아연 전극의 부식 속도를 확실히 감소시키는 효과가 있었으며 그리고 $Pb_3O_4$의 첨가에 의한 아연 전극의 부식 전위는 순수아연 전극에 비하여 다소 높았으나 개로 전압에는 거의 영향이 없었다. 그리고 4가지 종류의 첨가제는 내식성과 가속 수명시험시의 사이클 수명을 향상시키는 데 중요한 역할을 하고 있는 것으로 확인되었다. 더욱이 Tartrate 첨가는 4가지 종류의 첨가제 중에서 상대적으로 충방전 특성을 개선할 뿐 아니라 양호한 내식성 효과가 확인되었다.

• 한국재료학회지
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• 제9권6호
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• pp.630-634
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• 1999

$Al(OH)_3$와 비정질 $SiO_2$를 출발원료로 사용하여 반응소결을 통한 다공성 뮬라이트를 제조하였다. $Al(OH)_3$와 $SiO_2$의 몰비를 뮬라이트의 화학양론적 조성과 실리카와 얄루미나가 많은 조성으로 변화시키고, 각 조성에 $AlF_3$를 0, 1, 5, 10wt% 첨가하여 뮬라이트의 생성에 미치는 조성과 첨가제의 영향을 살펴보았다. 첨가한 $AlF_3$의 양이 많아질수록 낮은 온도에서 뮬라이트가 생성됨을 보였고, 첨가된 $AlF_3$의 양이 5wt%인 경우, 화학량론적 뮬라이트 조성에서 율라이트가 $1250^{\circ}C$에서부터 생성되기 시작하였으 며 $1300^{\circ}C$ 이상 열처리한 경우 충분히 발달한 침상형의 다공성 뮬라이트가 합성되었다. $AlF_3$의 양이 5wt% 이상 첨가한 경우 열 처리 온도의 영향은 크게 나타나지 않았으며, 소성체의 수축도 거의 일어냐지 않았다.

• 환경영향평가
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• 제13권1호
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• pp.9-19
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• 2004

This study is performed to examine the relationship between air pollution exposure and mortality in Daejeon for the years of 1998 - 2001. Daily counts of death were analyzed by general additive Poisson model, with adjustment for effects of seasonal trend, air temperature, humidity, and day of the week as confounders in a nonparametric approach. Daily death counts were associated with CO(4 day before), $O_3$(current day), $PM_10$(4 day before), $NO_2$(6 day before), $SO_2$(2 day before). Increase of $31.07{\mu}g/m^3$(interquartile range) in $PM_10$ was associated with 2.0 % (95% CI = 0.5 % - 3.5 %)) increase in the daily number of death. This effect was greater in children(less than 15 aged) and elderly(more than 65 aged). We concluded that Daejeon had 2 - 4 % increase in mortality in association with IQR in air pollutants. Daily variations in air pollution within the range currently occurring in Daejeon might have an adverse effect on daily mortality. These findings also support the hypothesis that air pollution at levels below the current ambient air quality standards of Korea except PM10, is harmful to sensitive subjects, such as children or elderly.

• 환경위생공학
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• 제18권3호통권49호
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• pp.89-99
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• 2003

This study is peformed to examine the relationship between air pollution exposure and mortality in Incheon for the years of 1998 - 2001. Daily counts of death were analyzed by general additive Poisson model, with adjustment for effects of seasonal trend, air temperature, humidity, and day of the week as confounders in a nonparametric approach. Daily death counts were associated with CO(1 day before), O$_3$(2 day before), PM$_{10}$(1 day before), NO$_2$(1day before), SO$_2$(1 day before). Increase of 32.21 ${\mu}$g/m$^3$(interquartile range) in PM$_{10}$ was associated with 1.9 % (95% CI = 0.8 % - 2.9 %) increase in the daily number of death. This effect was greater in children(less than 15 aged) and elderly(more than 65 aged). We concluded that Incheon had 2 - 4 % increase in mortality in association with IQR in air pollutants. Daily variations in air pollution within the range currently occurring in Incheon might have an adverse effect on daily mortality. These findings also support the hypothesis that air pollution, at levels below the current ambient air quality standards of Korea, is harmful to sensitive subjects, such as children or elderly.

• 한국세라믹학회지
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• 제54권4호
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• pp.340-348
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• 2017

$SiC_f/SiC$ composites were joined using a $60{\mu}m-thick$ $Ti_3AlC_2$ or $Ti_3SiC_2$ MAX phase tape. The filler tape was inserted between the $SiC_f/SiC$ composites containing a 12 wt.% $Al_2O_3-Y_2O_3$ sintering additive. The joining was performed to a butt-joint configuration at $1600^{\circ}C$ or $1750^{\circ}C$ in an Ar atmosphere by applying 3.5 MPa using a hot press. Microstructural and phase analyses at the joining interface confirmed the decomposition of $Ti_3AlC_2$ and $Ti_3SiC_2$, indicating the joining by solid-state diffusion. The results showed sound joining interface without the presence of cracks. Joining strengths higher than 150 MPa could be obtained for the joints using $Ti_3AlC_2$ or $Ti_3SiC_2$ at $1750^{\circ}C$, while those for joined at $1600^{\circ}C$ decreased to 100 MPa approximately without the deformation of the joining bodies. The thickness of initial filler tape was reduced significantly after joining because of the decomposition and migration of MAX phase owing to the plasticity at high temperatures.

• 한국재료학회지
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• 제27권9호
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• pp.507-511
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• 2017

An optimum route to fabricate oxide dispersion strengthened ferritic superalloy with desired microstructure was investigated. Two methods of high energy ball milling or polymeric additive solution route for developing a uniform dispersion of $Y_2O_3$ particles in Fe-Cr-Al-Ti alloy powders were compared on the basis of the resulting microstructures. Microstructural observation revealed that the crystalline size of Fe decreased with increases in milling time, to values of about 15-20 nm, and that an FeCr alloy phase was formed. SEM and TEM analyses of the alloy powders fabricated by solution route using yttrium nitrate and polyvinyl alcohol showed that the nano-sized Y-oxide particles were well distributed in the Fe based alloy powders. The prepared powders were sintered at 1000 and $1100^{\circ}C$ for 30 min in vacuum. The sintered specimen with heat treatment before spark plasma sintering at $1100^{\circ}C$ showed a more homogeneous microstructure. In the case of sintering at $1100^{\circ}C$, the alloys exhibited densified microstructure and the formation of large reaction phases due to oxidation of Al.