• Polymer(Korea)
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• v.25 no.1
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• pp.63-70
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• 2001

The objective of this study was to investigate the effect of cure type on the processing and physical properties under conditions of similar stress-strain properties. On the carbon black filled natural rubber(NR) based compound, the induction time decreased, but the cure rate became fast with increasing loading of sulfur donor agent. Tensile strength was little affected on the curing type. However, elongation generally decreased with increasing accelerator. Effect of cure type on the blow-out properties was followings: CV

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.607-611
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• 2007

To improve transfection efficiency, we prepared histidine-low molecular weight water-soluble chitosan (LMWSC) having the potential to form complex with DNA as a cationic polymer. Histidine-LMWSC was synthesized by the esterification reaction and removing phthaloyl group. The histidine-LMWSC was characterized using FT-IR, $^1H$ NMR spectra. Histidine-LMWSC was complexed with plasmid DNA (pDNA) in various polymer/DNA (N/P) weight ratios, and the complex was identified using gel retardation assay. The particle sizes of the hisitidine-LMWSC/DNA complexes were measured on a DLS instrument by fixing the histidine-LMWSC/DNA weight ratio of 10/1. Owing to the utilization of a large excess amount of cationic LMWSC against anionic DNA, the particle size of histidine-LMWSC/DNA complexes was in the range of 100~200 nm. Therefore, histidine-LMWSC will be useful in the development of gene carriers.

• Journal of Sericultural and Entomological Science
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• v.50 no.2
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• pp.71-75
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• 2012

Silk is a natural polymer that has the advantages of the biocompatibility, excellent mechanical strength, low immune rejection, and molding facility. But silk does not dissolve easily in water or general solvent. To investigate the characteristics of silk biological membranes according to dissolving condition of silk fibroin, we made the silk biological membranes using silk fibroin solutions with different amount and dissolving time of silk. The characterizations of the silk biological membranes such as morphology, structure, and mechanical strength were observed. Although each biological membrane has the same fibroin content, there was a significant difference in the thickness and transparency. But there was no significant change in the molecular weight of the silk fibroin solutions and morphology of silk biological membranes. We were established the manufacturing condition for silk fibroin biological membrane. So we expect that the conditions will help in the development of medical supplies in the future.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.35-43
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• 2010

We have developed a sodium fluoride containing gelatin and methyl cellulose gel. Cariostatic abilities of those gel were investigated and compared with APF gel and fluoride varnish($Cavityshield^{TM}$). We prepared the bovine tooth samples and divided into two surface, control side and experimental side in same specimen for exclusion of difference between specimens. The experiment was consisted of 4 groups : (I) APF gel : (II) $Cavityshield^{TM}$ : (III) Gelatin F gel : (IV) Methyl cellulose F gel Decalcification were produced by placing each specimen into artificial acidic solution(pH 4.0) for 72 hours. Surface microhardness were measured and depth of demineralization lesion were measured by polarizing light microscope. The results were as follows: 1. The difference of VHN between control and experimental side is smallest in group I (p<0.05). 2. The largest difference was shown in group II (p<0.05). 3. There were no significant difference between group III and IV in microhardness test (p>0.05). 4. The difference of lesion depth is smallest in group I (p<0.05). 5. There were no significant difference between group II, III and IV in lesion depth (p>0.05). The result of the present study indicate that the fluoride containing gelatin and methyl cellulose gel is more effective than APF gel and is similar to fluoride varnish application for prevention of demineralization.

• Food Science and Industry
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• v.53 no.1
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• pp.2-32
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• 2020

In recent years, significant importance has been given to chitooligosaccharides (COS) due to its potent notable biological applications. COS can be derived from chitosan which is commonly produced by partially hydrolyzed products from crustacean shells. In order to produce COS, there are several approaches including chemical and enzymatic methods which are the two most common choices. In this regard, several new methods were intended to be promoted which use the enzymatic hydrolysis with a lower cost and desired properties. Hence, the dual reactor system has gained more attention than other newly developed technologies. Enzymatic hydrolysis derived COS possesses important biological activities such as anticancer, antioxidant, anti-hypersentive, anti-dementia (Altzheimer's disease), anti-diabeties, anti-allergy, anti-inflammatory, etc. Results strongly suggest that properties of COS can be potential materials for nutraceutical, pharmaceutical, and cosmeceutical product development.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.10
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• pp.1466-1470
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• 2009

This study was focused on the development of anticariogenic edible films using pullulan containing grapefruit seed extract (GFSE), polylysine or propolis. According to the result of antimicrobial activity (disc diffusion method) of GFSE, polylysine and propolis against Streptococcus mutans, antimicrobial pullulan film was produced by adding grapefruit seed extract. The optimum combination of pullulan and sorbitol (plasticizer) was 10$\sim$15% (w/v) and 40$\sim$50% of pullulan (w/w), respectively. Minimum concentration of grapefruit seed extract for growth inhibition of Str. mutans was 50 ppm in medium. Formulation of antimicrobial pullulan films containing grape seed extract was established and these results evidently showed potential for commercial application.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.1
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• pp.35-45
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• 2003

Polymer electrolyte fuel cells(PEFC) have been considered to be a suitable candidate for residential, portable and mobile applications, due to their high efficiency and power density, even at low operating temperature. KIER developed a 5kW class PEFC system for residential application and operated the system for over 1,000 hours. To develop a 5kW PEFC system, performance of a cell was improved through successive tests of single cell of small and large area. Fabrication of three 2,5 kW class stacks, design and fabrication of natural gas reformer, design of auxiliary equipments such as DC/DC converter, DC/AC inverter and humidifying units were carried out along with integration of components, operation and evaluation of total system. During the development period from 1999 to 2001, MEA(membrane electrode assembly) fabrication technologies, design and fabrication technologies for separators, stacking technologies and so on were developed, thereby providing basis for developing stacks of higher efficiency and power density in the future. Experience of development of natural gas reformer opened possibilities to use various kinds of fuels. Main results obtained from the development of a 5kW class PEFC system for residential application are summarized.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.13-18
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• 2012

A die casting mold releasing agent was prepared from aqueous mixture of powdery carbon black and water soluble natural polymeric materials such as xanthan gum(X-gum) and carboxymethyl cellulose(CMC), which were used as thickening agent as well as curing agent with aldehydes. The suitable concentration of natural polymers for stable dispersion of carbon black in water was 0.25 wt% of X-gum or 1.0 wt% of CMC. When CMC was used less than 1 wt%, the final carbon black disperion showed a rapid phase separation. The adhesion of carbon black releasing agent on glass plate was improved with the amount of crosslinking agent, glutaraldehyde and chain extender, oligosaccharide. However, the affinity of carbon black releasing agent prepared with X-gum was stronger than that with CMC on glass plate. The final carbon black mold releasing agents prepared under our mixing conditions can be applied to the production of castings of high quality with good workability and without worthening evironmental situations.

• Fire Science and Engineering
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• v.22 no.3
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• pp.300-304
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• 2008

The flame retardancy was evaluated to present as the fundamental data to decrease the fire hazard of polymers and life losses according to the addition of clay. The combustion characteristics were examined to increase flame retardancy and to decrease smoke yield of epoxy by the addition of clay such as montmorillonite in this study. For this study, the experiments of flame retardancy were conducted the measurement of the limiting oxygen index (LOI), char yield, and smoke density. As MMT concentration increased, LOI and char yield increased. This result showed that the flame retardancy of epoxy/MMT composite was improved. On the contrary, smoke density increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.203.2-203.2
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• 2016

미생물이 스스로 생성한 고분자 물질에 싸이며 군집체를 형성한 바이오필름은 고체 표면에 부착되며 우리 생활 속에 다양한 형태로 발견할 수 있다. 바이오필름은 미생물에 적합하지 않은 외부 환경으로부터 미생물 스스로 보호하는 기능을 하며, 형성된 바이오필름은 오랜 기간 동안 생존하여 살균제나 항생제로부터 저항성을 가져 살균과정에서 제거되지 않고 2차오염을 야기할 수 있어 식품 가공 기계 및 수도관, 의료기기 등에 형성되었을 경우 식품 오염, 상처 감염 등의 원인이 된다. 이 때문에 위생과 바이오필름의 상관관계를 인지하고 이를 제어하기 위한 연구가 여러 방법으로 진행되고 있다. 대표적인 방법으로는 천연 향균제 개발, 쿼럼 센싱(Quoroum sensing)과 같이 미생물의 신호전달 체계를 차단하는 물질 개발 및 플라즈마 처리 등이 있다. 본 연구에서는 격자형식의 유전장벽방전(DBD) 형식의 플라즈마 소스를 개발하여 바이오필름의 효과적인 제어 가능성을 확인하고, 제어 방식의 관계를 파악하였다. 플라즈마 처리 대상의 화학적 분석을 위하여 유기물질 등을 사용해 플라즈마 처리수 내 화학물질 분석 시스템을 구축하여 이를 기반으로 플라즈마로 생성된 HNO2, NO2-, H2O2 등의 화학종이 가지는 바이오필름 제어 관계를 살펴보았으며, 화학적 방법인 제어효과와 비교하여 플라즈마의 바이오필름 제어 특성에 대해 살펴보았다. 본 발표에서 플라즈마의 바이오필름 제어효과에 대한 분석에 대해 더 자세한 결과가 발표될 예정이다.