• The Science & Technology
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• v.35 no.12 s.403
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• pp.6-9
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• 2002

명왕성 밖에서 거대한 얼음-돌 천체 발견/남공 상공 오존층 작아져/가장 아름다운 물리학 실험 10가지/곤충으로 박테리아 퇴치/인공의 뇌운으로 산불 끈다/전기자동차용 리튬이온전지 개발/박테리아 위성 발사로 생명체 기원 실험/대용량 원자 메모리 기술 개발/세계에서 가장 높은 발전 타워/원자파 레이저로 화산폭발 예측/새 치아를 생물학적으로 자라게 한다/강하고 견고한 에어로겔 제조/유리 속의 분자도 구조를 가졌다

• Defense and Technology
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• no.4 s.290
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• pp.18-29
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• 2003

냉전의 또 하나의 부산물은 우주경쟁인데, 인공위성 등 발사체의 추진기관은 거의 예외 없이 액체연료를 사용하는 액체추진로켓이고, 이것의 연료가 되는 액체산소, 액체수소 등은 발사체에 저장된 상태로 보관 할 수 없다는 단점 때문에 거의 군사용으로 적용되고 있지 않다. 지금은 SATURN-V와 같은 거대한 액체 추진 로켓을 대신해서 부분적으로 재활용이 가능한 우주왕복선이 사용되고 있는데, 여기에는 처음 이륙단계 대부분의 추력을 고체추진제에 의존하고 있기 때문에 이들의 성능 향상을 위한 좀 더 강역하고, 안전성을 높일 수 있는 에너지 물질에 대한 요구가 증대되고 있는 실정이다.

• Journal of the KSME
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• v.55 no.7
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• pp.32-36
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• 2015

최근 화석 연료의 과다 사용에 따른 에너지 자원 고갈 및 환경오염에 대한 우려가 증가함에 따라 비화석연료 기반의 재생가능하고 지속가능하며, 환경친화성이 높은 에너지에 대한 관심이 급증하고 있다. 농산폐기물, 폐목재, 에너지작물, 도시고형폐기물, 미세조류, 거대조류 등 육상 및 해상에서 발생하는 바이오매스는 재생가능한 에너지원으로서 화석원료와는 달리 사용 후 발생하는 이산화탄소를 다시 흡수하는 탄소중립(carbon-nutral)의 특성을 갖고 있어 전세계적으로 많은 주목을 받고 있다. 바이오연료 중 당질계원료를 이용하는 바이오에탄올 및 식물성유지를 이용하는 바이오디젤은 현재 상업적인 생산이 이루어지고 있으나, 이들 1세대 바이오연료는 식량자원과의 경쟁이라는 원천적인 한계를 가지고 있고, 분자구조식에 산소를 포함하고 있기 때문에 기존 화석원료에서 출발하는 가솔린, 항공유 및 디젤과 비교하였을 때 에너지 함량이 낮은 단점이 있다. 따라서 기존 1세대 바이오연료에서 탈피하여, 식량자원과 경쟁이 없으며, 또한 분자구조식에 산소를 적게 포함하거나 아예 포함하지 않는 바이오연료("drop-in" 바이오연료) 생산에 많은 관심이 집중되고 있다. 이 글에서는 최근 그린공정으로 대표되는 초임계 유체를 이용한 "drop-in" 바이오연료를 제조하기 위한 바이오매스 액화의 기술동향을 소개하고자 한다.

• Korean Journal of Microbiology
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• v.36 no.3
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• pp.203-208
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• 2000

A Baczllus circdans KCTC3004 $\alpha$-amylase gene contained in a recombinant plasmid pAL850 was transferred into a new shuttle vector plasmid pALSIlI by ligating linearlzed DNAs of pUC19 and pUB110. B. subtilis RM125 and B. megatenurn ATCC14945 transfonned with pALS111 produced the $\alpha$-amylase substantially Most of the enzyme was produced during the exponential growth period. The maxiinurn activities of the $\alpha$-amylase produced by the Bucillus transformants were compared with that of the B. circulans gene donor strain. The B. subtilis RM125(pALS111) enzyme showed the actlvicy 95 times higher than that of the gene donor cells, followed by the B, nzegaterium ATCC14945(pALSlll) enzyme with activity 34 limes higher than that of the gene donor cells. While E coli secreted about 10% of the produced enzyme, B. subtilis excreted the enzyme inlo the medium wholly and B. megaterirun about 98% ofthe total product. The plasmid pALSI11 was quite stable inB. nzegaterium (92%), inoderately stable in B. subtilis (76%), but was unstable in E. coli (38%). The SDS-PAGE and zymogram of this enzyme produced in E. coli(pALS111), B. subtilis( pALS111) or B. megateril~m (pALS111) indicated a molecular weight of 55,000. The enzymes overproduced in three different host cells hydrolyzed starch to produce mainly maltoaiose and mallooligosaccharides.

• The Korean Journal of Mycology
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• v.27 no.2 s.89
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• pp.100-106
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• 1999

The polysaccharides, intracellular and extracellular, extracted from the liquid culture of the Agrocybe cylindracea were purified and characterized. The mycellial cellular productivity of Agrocybe cylindracea was proved to be almost 2 folds in the shaking culture compared to the standing culture. These polysaccharides were purified by the DEAE-cellulose ion exchange chromatography and the Sepharose 2B size exclusive gel filteration. The two purified fractions of extracellular polysaccharides, ACEPDG and ACEPAG, contained 75.8% and 65.4% total sugar respectively. The total sugar content of ACIPDG and ACIPAG, the two purified fractions of intracellular polysaccharides, were 89.2% and 54.2% respectively. The molecular weights range of all the substances were estimated to be above 100,000, from 300KDa of ACEPDG to 600 KDa of ACIPAG. The results of sugar analysis by HPLC showed that the sugar part of ACEPDG was consisted of glucose and inositol. The ACIPDG, ACEPAG and ACIPAG contained three kinds of monosaccharides, glucose, fructose and inositol.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.755-764
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• 2000

Fate and transport of hydrophobic organic contaminants can be influenced by naturally-existing humic substances and surfactants applied to wash polluted soils in the subsurface environment. The objective of this paper is to study the solubility enhancement of four PAHs (polycyclic aromatic hydrocarbon) and p,p'-DDT in humic acid and surfactant solutions. As the number of aromatic ring is increased, the extent of solubility enhancement of PAHs by humic acid increased. Although the hydrophobicity of p,p'-DDT was the largest among five organic compounds used, the extent of solubility enhancement of p,p'-DDT by humic acid was lower than that of pyrene. In case of anionic surfactants, the extent of the increased solubility of five organic compounds by SDS and SDDBS was increased linearly, but the extent of the increased solubility of p,p'-DDT by MADS-12 was lower than that of perylene.

• Polymer(Korea)
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• v.26 no.3
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• pp.353-359
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• 2002

High intensity ultrasound has been applied to a series of poly(ethylene oxide) (PEO)/water systems having different molecular weights of PEO. Major interest was focused on the effect of ultrasonic wane on the melt viscosity chemical structure and thermal properties of PEO. The expected role of ultrasound used in this study was to generate macroradicals of PEO chains by the formation and subsequent collapse of bubbles. It was found that the melt viscosity and chemical structure of PEO change significantly depending on the sonication time. For the prolonged sonication, PEO chains were significantly degraded and new end groups were formed by the interplay of various radical species. When the molecular weight of PEO was relatively higher, the crystallization rate was decreased and the intensity of the melting peak was reduced.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.158-162
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• 1986

Various cell wall polysaccharides such as ionically associated pectin (IAP), covalently bounded pectin (CBP),4N potassium hydroxide soluble hemicellulosic fraction (HF,) and 0-3N soluble hemicellulosic fraction (HF,) were fractionated from crude cell wall of the fresh and soft persimmon by chemical method. The changesin cell wall polysaccharides were studied by gel filteration chromatography . The content of crude cell wall remarkably decreased in the soft persimmon. The decreasing rates of IAP, CBP and $HF_2$ were 59, 60 and 74%, respectively, while $HF_1$ and cellulose changed only a little during softening. Sugar compositions of IAP and CBP were 72-84% uronic acid, 5-1% hexose and 11-16% pentose, and also the hemicellulose was composed of uronic acid besides hexose and pentose that was hemicellulosic components. The loss rate of pentose in IAP, of hexose in CBP, of hexose and uronic acid in $HF_2$, of pentose in $HF_1$ increased during softening. Though apparent average molecular freight of all polysaccharides shifted from high molecular freight to low molecular weight polymer, the shifting degree of CBP and $HF_2$ was especially remarkable during softening. It is suggested that the severe softening phenomenon of persimmon involved the degradation and dissolution of wall bound-CBP and $HF_2$ which were associated with each other.

• Korean Journal of Microbiology
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• v.40 no.2
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• pp.167-171
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• 2004

Reduction in the leakage of the amplified PCR product out of cell is required for effective in situ PCR. For this purpose, primers with complementary tail sequences at their 5' sides were utilized to synthesize high molecular weight PCR products, but it is time-consuming and causes deterioration of cellular appearance with many PCR cycles. Therefore, it is required to optimize the PCR condition with minimal PCR cycles. To achieve the pur-pose, primer polymers were made without the target DNA in tube from nonspecific amplification with tailed primers and treated onto the fixed Molt/LAV cells on the glass slide for the 20 cycle-in situ PCR, in which the appropriate target signals were observed for the possible use of primer polymers in in situ PCR.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.761-763
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• 2001

Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Dendrimer can be made with high regularity and controlled molecular weight. Peculiar features of the dendritic geometry are the large number of end groups as well as the shape persistence in higher generations, approaching spherical geometry. One of the most peculiar characteristics of dendritic macromolecules is their controlled molecular structure and orientation, which means that they have a practical application in achieving a highly organized molecular arrangement. We attempted to fabricate a G4-48PyA dendrimer LB films containing 48 pyridinealdoxime functional end group that could form a complex structure with metal ions. Also, we investigated the surface activity of dendrimer films at air-water interface. And we have studied the electrical properties of the ultra-thin dendrimer LB films. The electrical properties of the ultra-thin dendrimer LB films were investigated by studying the current-voltage(I-V) characteristics of metal/dendrimer LB films/metal (MIM) structure. And rectifying behavior of the devices was occurred in applied field.