• Polymer(Korea)
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• v.32 no.3
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• pp.199-205
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• 2008

In this study, we fabricated poly (lactide-co-glycolide) (PLGA) scaffold modified with small intestinal submucosa (SIS) as a drug delivery matrix of bioactive molecules. SIS derived from the submucosa layer of porcine intestine has been widely used as biomaterial because of low immune response. PLGA scaffold was prepared by the method of solvent casting/salt leaching. Novel composite scaffolds of SIS/PLGA were manufactured by simple immersion method of PLGA scaffold in SIS solution under vacuum. SEM observation shows that PLGA and SIS/PLGA scaffolds have interconnective and open pores. Especially, SIS/PLGA scaffold showed that micro-sponge of SIS with interconnected pore structures were formed in the pores of PLGA scaffold. In order to assay release profile of proteins, we manufactured FITC conjugated BSA loaded PLGA and SIS/PLGA scaffold. And the release amount was identified by fluorescence intensity using the fluorescence spectrophotometer. The initial burst of BSA containing SIS/PLGA scaffolds was lower than that of PLGA scaffolds resulting in constant release. And release of BSA in SIS/PLGA scaffold was fast and incremental because of the increased content of BSA. In conclusion, we confirmed that penetrated SIS solution prevented the initial burst of BSA and PLGA modified with SIS scaffold is useful as protein carriers with controlled release pattern.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.331-337
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• 2019

Titania has become the most applicable material for photocatalytic application. Nevertheless, titania has the weak point in its wide band gap energy that is mainly activated by UV irradiation. There have been vast research challenges in order to make the wide band gap energy of titania narrow that could be activated in the presence of visible light. Various modifications of titania surface were popular because titania needs to change its surface to respond in visible light. Among the methodological approaches, N-doping to titania can be the alternative candidate because it is facile process and eco-friendly. The activated electron from valence band in N-doped $TiO_2$ migrates to conduction band in the presence of visible light irradiation, which shows photocatalytic activity as well. In this study, focused on the evaluation of nitrogen state after N-doping through brief review. Arguments are still existed in nitrogen states and their different effects on photocatalytic activity. In particular, two nitrogen states are generally reported; substitutional and interstitial states. The research articles regarding N-doped $TiO_2$ are continuously appearing because the potential application of water split in visible light is still fascinate. The future of N-doped $TiO_2$ is also presented by referrals based on various literature.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.733-737
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• 2012

This study reports the microfluidic preparation of monodisperse multiple emulsions using hydrodynamic control. To generate multiple emulsions, we fabricate a microfluidic capillary device based on co-flowing stream without any surface modification of microchannels. Based on the system, we can successfully generate multiple emulsions (W/O/W) using water containing 0.5 wt% Tween 20, n-hexadecane with 5 wt% Span 80, and 10 wt% poly (vinyl alcohol) (PVA) aqueous solution, respectively. Furthermore, we control the number of inner droplets by modulation of flow rate of inner fluid at fixed flow rate of middle and outer fluid. The multiple emulsions having precisely controlled inner droplets' size and number can be applicable for multiple chemical reactions as an isolated microreactor.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.216-223
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• 2006

To increase the stability of liposomes in blood circulation, surface modification of liposomes by incorporating a lipid-polymer derivative in the lipid bilayer or conjugating a hydrophilic polymer to the liposomal surface has been developed. In this study, the comblike copolymer, poly(HEMA-co-HPOEM), having multiple polyethyleneoxide side chains was prepared by free radical polymerization of hydroxyethylmethacrylate (HEMA) and hydroxypolyoxyethylenemethacrylate (HPOEM) as vinyl monomers. Poly(HEMA-co-HPOEM) was conjugated to the liposomal surface and the characteristics of the modified liposomes in serum were investigated. Conjugation of poly(HEMA-co-HPOEM) to liposomes increased the particle size of the liposomes by 30 nm and decreased the absolute value of zeta potential of the liposomes by shielding the negative charge of liposomal surface. Loading efficiency of model drug, doxorubicin, in liposomes was about 90% and the efficiency was not affected by conjugation of poly(HEMA-co-HPOEM) to liposomes. The particle size of poly(HEMA-co-HPOEM)-conjugated liposomes in serum did not changed and the protein adsorption was lower than that of control liposomes or liposomes containing polyethyleneoxide-lipid derivative (PEG-liposomes). These results suggest that poly(HEMA-co-HPOEM) is efficient for the stabilization of liposomes in blood circulation.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.1-5
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• 2011

High concentration of carbon dioxide at subway cabin is one of the serious environmental concerns because carbon dioxide causes drowsiness, headache, and nervelessness of passengers. Ministry of Environment set a guideline for indoor carbon dioxide levels in train or subway in 2007. In this study, a carbon dioxide removal system for subway cabin was developed and tested using a test subway cabin. Various types of modified zeolites were used as the adsorbent of carbon dioxide. The tested zeolites were applied to the subway cabin, and showed high potential to lower the indoor $CO_2$ level.

• Corrosion Science and Technology
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• v.15 no.1
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• pp.28-37
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• 2016

Due to the increased construction of offshore concrete structures and the use of de-icing salts for the purpose of snow removal, the needs for the development of anti-corrosive concrete are increasing. To solve these problems, an evaluation of the mechanical and durability properties for concrete were conducted by mixing modified-sulfur as 0 %, 5 %, 10 %, 15 % cement weight ratio. Both strengths and the properties affecting durability such as water absorption coefficient, chloride ion permeability, accelerated carbonation resistance, rapid freezing and thawing, and chemical resistance were evaluated. All evaluations performed were according to the test specifications associated KS. The results indicate that mixing of modified-sulfur lowed chloride ion permeability and improved chemical resistance.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.130.2-130.2
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• 2010

한전 전력연구원에서는 2009년 12월부터 125 kW급 용융탄산염 연료전지 발전시스템의 성능평가를 위한 운전이 진행되고 있다. 현재 진행 중인 "250 kW급 열병합 용융탄산염 연료전지 Proto Type개발" 과제의 최종시작품인 250 kW급 발전시스템은 125 kW급 MCFC 스택 2기로 설계되어, 125 kW급 시스템의 시험운전은 매우 중요한 기술적 성과가 될 것이다. 현재 125 kW급 MCFC 스택은 10,000 $cm^2$의 유효전극면적을 갖는 단위전지들로 구성되었으며, 적층 스택의 온도 및 농도분포의 최적화를 위해 내부 매니폴드 및 Co-flow Type 열교환기 기반의 분리판을 개발 적용하였다. 연료극의 전극 구성은 Ni-Al alloy로, 공기극의 전극 구성은 Lithiated-NiO로 이루어졌다. 그리고 매트릭스는 ${\alpha}-LiAlO_2$로 제작되었고, 전해질은 Li과 K Carbonate가 68 : 32 비율로 섞인 용융염을 사용하였다. 본 125 kW급 용융탄산염 연료전지 시스템의 운전평가는 고적층 스택의 온도 및 농도 분포를 확인하고, 최적화된 스택 운전 조건을 도출하는 것을 그 목적으로 하고 있다. 125kW급 스택 1기의 규모의 주변기기 시스템은 외부개질기, 촉매연소기, 이젝터, 고온순환 블로어 및 공기블로어 등으로 이루어져 있다. 고온형 연료전지 시스템에서 연료극과 공기극의 균일한 온도 및 압력 확보는 매우 중요하며, 이를 위하여 외부개질기 및 촉매연소기 연동을 통한 온도편차를 최소화하고, 기존 고온용 순환 블로어 대신 이젝터를 개발 도입하여 압력균형을 조절하였다. 125kW급 MCFC 시스템은 2009년 12월부터 전처리 운전을 시작하여 2010년 1월 말부터 PCS로 전기를 생산하고 있다. 평균전압 0.83V에서 100kW의 출력을 기록하였으며, 피크부하 120 kW, 누적출력량 30 MWh를 초과달성하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.206.2-206.2
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• 2010

현재 RPF 생산공정에서 생산된 RPF는 약 7,500~8,500kcal/kg 의 높은 열량을 지니고 있다. 이러한 특성으로 연소시 소각로 내부의 온도가 부분적으로 급격히 상승하여 적정온도조절이 어렵고, 로내 장치들의 내구성이 저하되는 등 문제가 발생하고 있다. 또한, RPF에 포함된 비교적 높은 농도의 염소 함량(0.8~1.8% wt)으로 인해 다량의 대기오염물질이 발생되는 단점이 나타나고 있다. 따라서, 이러한 문제점들을 개선하기 위해 RPF의 개질이 필요하며 본 연구에서는 슬러지와 RPF를 혼합하여 열량, 성형성, 염소함량등을 고려하여 최적의 혼합비율을 선정하였다. J하수처리장에서 발생하는 하수슬러지를 이용하여 5, 15, 25, 30, 35%를 RPF 성형공정에 혼합하여 실험하였다. 5% 혼합시 발열량은 약 6,300~6,800kcal/kg, 염소농도는 0.8~1.6%(wt), 15% 혼합시 발열량은 5,500~6,000kcal/kg, 염소농도는 0.7~1.4%(wt), 25% 혼합시 발열량은 5,200~5,900kcal/kg, 염소농도는 0.6~1.1%(wt), 30% 혼합시 발열량은 5,000~5,700kcal/kg, 염소농도는 0.6~1.0%(wt), 35% 혼합시 발열량은 4,800~5,200kcal/kg, 염소농도는 0.4~0.6%(wt)으로 나타났다. 각 혼합비율에서 관찰된 성형성은 5~25% 혼합까지는 성형된 RPF와 유사하게 일정한 크기 및 강도를 유지 할 수 있었으나, 25% 이상 혼합시 분말형태의 가루가 많이 발생되며 강도가 약해져 쉽게 부스러지는 문제점등이 나타났다. 연료의 개질 형태나 성형성등을 고려하였을 때 슬러지 혼합비율이 약 15~25% 정도가 최적 혼합비율인 것으로 나타났다.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.73-82
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• 2005

Linear traverse method and point count method described at ASTM have been widely used to estimate the air void system in hardened concrete. These methods, however, are rarely used at present, because they require many efforts and time consuming works. Also these results depend on each person's decision, and are not repeatable. Thus, new image analysis method using microscope and computer processes has been approached for analyzing air void system in hardened concrete. The purpose of this study was to analysis the air void systems in latex-modified concretes using a reasonable and objective image analysis method with main experimental variables such as cement types(ordinary portland cement, rapid setting cement) and latex contents(0%,15%). In the results of this study, the use of polymer latex showed that it could be attributed to its air void systems, due to the fact that the latex emulsion acts as an air-entraining agent, which thus generally guarantees an adequate air-void system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.208-213
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• 2009

Artificial lightweight aggregates were produced by using bottom ashes and dredged soils from coal power plant. The amount of glassy phases on the aggregate surfaces, specific gravities, absorption rates, and observations of cross-sectional surfaces were compared according to the compositions, sintering temperatures, and the amount of coating. It is concluded that surface modification by 10 % $CaCO_3$ coating on the aggregate surfaces enhances the properties of aggregates as follows: Specific gravities were controlled by depressing formation of large pores in the aggregates. Sticking phenomena among aggregates during the sintering process was drastically decreased by reducing glassy phases on the aggregate surfaces. Pumping problems during the application of ready-mix concretes containing lightweight aggregates having high value of absorption rates could be solved by reducing the absorption rate.