• Polymer(Korea)
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• v.32 no.6
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• pp.566-572
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• 2008

Polyethylene has been prepared via metallocene catalysts [(TMDS)$Cp_2$]$ZrCl_2$, 1, and [$(n-Bu)_2Cp_2$]$ZrCl_2$, 2, in the presence of hydrogen as a chain transfer reagent. Increase of hydrogen flow to the polymerization reactor resulted in the drop of catalytic activity, reduction of molecular weight of polyethylene, getting narrow of molecular weight distribution of polyethylene, and melting point of the polyethylene wax. It should be noticed that it was possible to control molecular weight down to 1500 and melting temperature to 60 $^\circ$C of polyethylene wax using the catalyst 1 that has been developed by authors as well as the catalyst 2 from Exxon.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.958-964
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• 2008

In this work, micro-sized dextran particles, which have recently been focused as one of the candidate materials for the Drug Delivery System(DDS), were prepared by means of the Supercritical Antisolvent (SAS) process with $CO_2$. With dimethyl sulfoxide(DMSO) as the solvent, effects of the operating variables such as temperature (308.15~323.15 K), pressure(90~130 bar), solute concentration(10~20 mg/ml), and the molecular weight of the solute(Mw=37,500, 450,000) on the size and morphology of the resulting particles were thoroughly observed. The higher solute concentration led to the larger particles, however, the injection velocity of the solution and pressure did not show significant effects on the resulting particle size. With dextran of the lower molecular weight, the smallest particles were obtained at 313.15 K. On the other hand, the size of the particles from the high molecular weight dextran ranged between $0.1{\sim}0.5{\mu}m$ with an incremental effect of the temperature and pressure. For the solute concentration of 5 mg/ml, the lower molecular weight dextran did not form discrete particles while aggregation of the particles appeared when the solute concentration exceeded 15 mg/ml for the higher molecular weight dextran. It is believed that if the solute concentration is too low, the degree of the supersaturation in the recrystallization chamber would not be sufficient for initiation of the nucleation and growth mechanism. Instead, the spinodal decomposition mechanism leads to formation of the island-like phase separation which appears similar to aggregation of the discrete particles. This effect would be more pronounced for the smaller molecular weight polymer system due to the narrower phase-splitting region.

• Korean journal of food and cookery science
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• v.32 no.6
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• pp.677-685
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• 2016

Purpose: Molecular press dehydration is one of the dehydration methods. The purpose of this study was to investigate the quality characteristics of tarts made with dehydrated purple sweet potatoes during the storage period. Methods: Quality characteristics of purple sweet potato tarts were evaluated by analyzing moisture content, water activity, total phenolics, anthocyanins, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, color, and sensory evaluation for 45 days of storage. Results: Moisture content of tart crust made with molecular press dehydration treated purple sweet potatoes with concentrations of 20%, 40%, 60%, and 80% maltodextrin as a dehydrating agent for 45 days was 8.47%, 7.95%, 6.96%, and 6.24% respectively; however, the moisture content of non-treated tart crust was 11.99% (p<0.05). Total phenolics, anthocyanins, and DPPH free radical scavenging activity of dehydrated purple sweet potato tarts were lowered than those of non-treated tart (p<0.05). Conclusion: These results indicated that tarts made with molecular press dehydrated purple sweet potatoes had effectively controlled moisture content and water activity during storage although total phenolics, anthocyanins, DPPH free radical scavenging activity, color, and sensory evaluation were decreased.

• KSBB Journal
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• v.16 no.4
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• pp.321-326
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• 2001

The change of molecular weight inside and outside a capsule produced using coencapsulating technology was investigated. Chitosan and chitosanase were enveloped in this membrane and product released was a loaded the medium by the principle of size exclusion. The leakage of substrate corresponding to the agitation speed was controlled by adjusting the alginate and CaCO$_3$ concentrations. The optimal condition of alginate concentration and agitation speed were 0.5% and 40rpm, respectively. Membrane thickness and capsules diameter were 10 $\mu$m and approx. 3.0 - 1.5 mm, respectively. Molecular weight difference by concentration and alginate viscosity were of little significance. In accordance with the molecular weight distribution versus enzyme concentration relationship, low concentration of enzyme produced high molecular weight oligosaccharides. At a 1.5 mm capsule size the product diffusion rate to outer surface highest. The molecular weight distribution of the released oligosaccharides was ranged from 1000 to 6000 Da. More than 80% of the initial activity of encapsulated enzyme retained after 8hrs of reaction.

• Culinary science and hospitality research
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• v.19 no.5
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• pp.23-35
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• 2013

This study aimed to determine the physicochemical and sensory qualities of yogurt dressing prepared with Bokbunja juice(0, 10, 20, 30 and 40%). As the amount of added Bokbunja juice increased, contents of organic acids(citric acid, tartaric acid, malic acid, succinic acid and acetic acid) increased. The viscosity of the control group(8306.67 cP) was higher than those of the others(1633.33~6913.33 cP). The pH of the control group(3.96) was higher than those of the others(3.90~3.85). The sweetness of the control group(14.43) was lower than 10% Bokbunja juice added group(14.93). Color L decreased significantly, whereas a value and b value increased significantly with more Bokbunja juice added. DPPH radical scavenging activity of the control group was 5.84%, whereas those of yogurt dressing samples with Bokbunja juice ranged from 39.72~88.17%. The sensory property results showed that yogurt dressing with 30% Bokbunja juice added group had the highest value in terms of color, flavor, taste, mouth feel, and overall acceptability. Overall, the result of this study indicates that the yogurt dressing containing 30% of Bokbunja juice was most preferred among the groups.

• Polymer(Korea)
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• v.31 no.6
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• pp.555-561
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• 2007

To obtain low molecular weight water soluble chitosan (LMWSC) with various molecular weights, chitosan oligosaccharides (COS) with lactic acid was separated by using ultrafilteration technique and LMWSC with a free amine group was prepared by the novel salts-removal method. The characterization of LMWSC removed the lactic acid and degree of deacetylation (DDA) were identified by FT-IR and $^1H-NMR$ spectra. Polydispersity index (PDI) was $1.278{\sim}1.499$, which indicates a relatively molecular weight distribution. To identify the potential as a gene carrier, we confirmed the transfection efficiency of COS fractioned according to molecular weight successfully and the salt-removed LMWSC using 293T cell. Also, LMWSC derivatives prepared for improvement transfection efficiency were evaluated using Balb/C mice.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.73-77
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• 2004

막분리 기술인 정밀여과와 한외여과는 물질의 크기 차에 따른 체분리 (sieving)를 기본 원리로 하기 때문에 분자수준에서의 선택적 물질분리가 어렵다는 문제점이 있다. 이러한 문제점을 해결하기 위한 대안으로서 분리막에 분자수준에서의 물질 선택성을 부여한 친화성 막(affinity membrane) 제조에 대한 연구가 활발히 이루어지고 있다.(중략)

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.1-8
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• 2001

선택적 가스분리를 위한 분자체탄소(Molecular Sieve Carbon: MSC)로서의 활용을 위해 제조된 활성탄소섬유의 흡착능과 분자체 특성이 다양한 분자크기를 갖는 가스 흡착실험을 통해 조사되었다. 각 활성화 조건별 세공크기분포와 세공발달 전개과정을 유추함으로서, 세공크기분포의 조절이 가능하게 되었으며 활성탄소섬유의 분자체 탄소로서 활용을 용이하게 할 수 있었다. 800, 85$0^{\circ}C$의 온도로 수증기에 의해 활성화한 활성탄소섬유의 경우 burn-off가 각각 50, 40% 정도를 가진 활성탄소섬유가 비교적 작은 분자크기(0.3~0.4nm)의 흡착질에 대한 분자체 특성을 나타냈다. 또한, 다양한 분자크기의 흡착질을 포함하는 혼합가스의 유속과 흡착온도의 조절로서 원하는 흡착질의 선택적 분리를 위해 활성탄소섬유가 갖는 분자체 특성 향상을 보였다.

• The Optical Journal
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• s.121
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• pp.41-50
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• 2009

보다 높은 공간분해능과 광검출능을 가지면서 분자의 고속 시간 응답 또는 거동 관측을 할 수 있는 Imaging 장치는 여러 가지 Nanotechnology를 포함한 요소기술의 진보에 따라 매일 새로워지고 있다. 그 중에서 분자관측에 의해 비로서 분명해지는 생체활동의 해명, 의료적으로 중요한 새로운 지견, 신규 유기재료 개발 등이 가능하게 되었으며, 얼마나 요소기술을 미묘하게 조합해 갈 것인지가 중요한 점이다. 이것은 분자관측을 목표로 하는 연구자뿐 아니라 이들 장치를 개발하는 기술자 또는 기업의 제휴가 필요하다는 것을 말한다. 이후에는 이들 연구자나 장치 제조사를 연결하여 상세한 대응을 하는 사업도 중요해질 것이다. 본고는 <광기술컨텍트 2009년 1월호>에 게재된 Takiguchi Yoshihiro 교수(Hikari Sangyo Sosei(광산업창성(光産業創成))대학원대학)의 기고문을 발췌, 번역한 것이다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.54-55
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• 2001

반도체 산업에서 메모리의 고집적화, 회로 패턴의 미세화에 따라 클린룸 공기중에 존재하는 분자상오염 물질 (Airborne Molecular Contaminants, AMCs)이 제조공정에 미치는 영향이 매우 중요하게 대두되었다$^{1)}$ . 분자상 오염물질은 입자상 오염물질과 달리 외관상 관찰이 어려우며, 오염 종류와 형태가 원소의 종류에 따라 매우 다양하게 나타난다. 클린룸에서의 입자상 오염물질은 고효율 필터(HEPA, ULPA)를 사용하여 제거 관리하고 있으나, 분자상 오염물질은 종류 및 형태조차 파악하지 못하고 있다. (중략)