• 대한화학회지
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• 제36권4호
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• pp.496-503
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• 1992

반도체 수소이온센서인 pH-ISFET를 제조 하고, 이를 ISFET 요소 센서로 이용하기 위하여 pH-ISFET의 Si$_3$$N_4$ 막 위에 요소 분해효소인 urease를 감광성 고분자 물질인 PVA-SbQ를 이용하여 고정화하였다. 제조된 센서는 빠른 응답특성과 우수한 재현성을 보였으며, 약 1∼50 mg/dl의 요소농도를 정량할 수 있었다. 또한 그 임상적용을 위한 기초연구로서 혈액 중에 존재하는 여러 가지 물질들이 센서의 출력에 미치는 영향을 조사하였으며, 혈장의 요소농도를 측정하여 현재 실용되고 있는 분광광도법의 결과와 비교하였다.

• Journal of Pharmaceutical Investigation
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• 제32권1호
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• pp.35-40
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• 2002

We prepared a novel dosage form, peel-off type soft hydrogel using poly(vinyl alcohol), and evaluated the effect of skin penetration enhancer on the indomethacin release from soft hydrogel by in vitro permeation and in vivo absorption test. In this study, we used four enhancers-urea, dimethyl urea, 1,1,3,3-tetramethyl urea, and pirotiodecane (1-[2(decylthio)ethyl]azacyclopentane-2-one, $HPE-101^{circledR}$). In addition, we evaluated the primary skin irritation test of soft hydrogel using rabbit. From these results, we could find the pirotiodecane was a prominent enhancer, and soft hydrogel seemed to be safe and have no irritancy.

• Journal of the Korean Wood Science and Technology
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• 제51권1호
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• pp.14-22
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• 2023

Economical use of larix (larch) boards (grade 3) in industries is lower than that of imported hardwood; thus, studies have been conducted toward performance improvement of larix boards. Herein, flexural modulus of larix board samples laminated with wood adhesives polyurethane resins, poly (vinyl acetate) resins, phenol-resorcinol-formaldehyde resins, melamine-formaldehyde resins, and urea-formaldehyde resins was compared with that of the samples bonded with adhesives reinforced with mesh-type basalt fibers. Moreover, the flexural moduli of the laminated samples bonded by mesh-type basalt fibers were compared with those of reinforced samples. The results showed that boards laminated with polyurethane and urea-formaldehyde resin adhesives had higher flexural modulus than those without the lamination. In particular, the increase in the flexural modulus was relatively significant for the 2- and 3-ply board structures laminated with polyurethane adhesives compared to those with reinforcement. The 3-ply board structure without reinforcement had the highest flexural modulus when the urea-formaldehyde resin adhesive was used.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.43-45
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• 2011

As technologies evolve, building large concrete structures ever built, but due to lack of maintenance after completion of concrete corrosion, leaks, and preparedness from the problem that is an urgent need. In particular, water-resistant variety of concrete structures. How the concept applies to the most important public drinking water purification and drinking water that is draining the production and storage, and distribution as the structure cause damage to the structure when the contaminated water is supplied to each home that can harm the health of citizens is the cause. Therefore, the correct choice of materials, and thorough a lot of investment in construction and maintenance should have. In this study, unlike conventional water-proof materials, methods, and in other reactions easily than conventional poly-urea resins have good physical performance and chemical resistance, high performance polyurea resin performance review of the physical infrastructure of the country for the longevity of would like to make long-term durability.

• Elastomers and Composites
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• 제53권2호
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• pp.86-94
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• 2018

The effect of the NCO index and catalyst type on the thermal stability of poly(urethane-isocyanurate) (PUIR) foams was investigated to identify a method for enhancing the flame resistance of PUIR. PUIR foams were prepared using 4,4-diphenylmethane diisocyanate (MDI) and [(diethylene glycol)adipate]diol, which were synthesized by esterification of adipic acid and diethylene glycol. Dabco K-15, Dabco TMR-30, and Toyocat RX-5 were used as the catalysts for trimerization and gelation. The amount of urea and isocyanurate groups in PUIR was semi-quantitatively determined by normalizing their absorbance with the phenyl absorbance measured by FT-IR. The normalization data showed that Dabco TMR-30 effectively generated isocyanurate groups in PUIR. As a result, Dabco TMR-30 effectively raised the decomposition temperature and increased the 800 K and 900 K residues of the PUIR foam synthesized with an NCO index of 200.

• 신재생에너지
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• 제8권4호
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• pp.38-43
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• 2012

Biodiesel is non-petroleum based fuel produced from vegetable oils or animal fats through transesterification. The compositions of saturated and unsaturated fatty acids in the feedstocks are important factors for biodiesel quality in terms of low-temperature fluidity and oxidative stability. The goal of this study is to improve the cold flow property of biodiesel from vegetable and animal origin containing highly saturated methyl esters (approx. 50%). In this purpose poly-saturated methyl esters in palm and tallow biodiesel were removed via urea-based fractionation and then the recovered fractions (enriched unsaturated fatty acid methyl esters) were supplemented with cold flow improvers. The highest concentration of unsaturated fatty acid methyl esters (93.8%) was obtained using a urea/fatty acid ratio of 3:1 at the crystallization temperature of $0^{\circ}C$ for 17 hours in incubation, with recovery of 71% and the addition of cold flow improver (Flozol$^{(R)}$ 515, 3,000 ppm) to the enriched poly-unsaturated fatty acid methyl esters reduced the CFPP(cold filter plugging point) of palm biodiesel from $12^{\circ}C$ to $-42^{\circ}C$. In tallow biodiesel both the enrichment of unsaturated fatty acid methyl esters (93.71%) and the addition of cold flow improver (Infineum R408, 3,000ppm) reduced the CFPP from $10^{\circ}C$ to $-32^{\circ}C$.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.33-35
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• 2003

Over the last 30 years, water-swellable and water-insoluble hydrogels have been extensively investigated and developed, leading to a large family of materials which have found use in a wide range of biomedical applications such as carriers of soft tissues, wound healing, ophthalmological applications, membranes for artificial kidney, and materials for blood compatible and other medical devices[1-3]. (omitted)

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1766-1768
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• 2000

신장병 진단의 척도로 요소의 농도는 매우 중요하다. 요소의 농도를 측정하기 위한 센서개발이 본 연구의 목적이다. 기존의 Potentiometry법은 Nernst식이 적용된다는 가정하에 감도를 측정했다. 실험결과 전극상에서 우레아제의 요소 가수분해 반응은 Nernst식을 적용할 수 없는 비가역적인 반응으로 판단되어 센서의 감도 측정을 Linear sweep Voltammetry(LSV)법을 이용하였다. Voltammetry법은 가역적이든 비가역적이든 관계없이 Cottrell 식에 의한 전류와 농도의 직선관계로부터 감도를 측정할 수 있다는 장점이 있다. 센서 전극의 표면은 SEM으로 분석하였고, LSV 법으로 측정한 센서의 감도는 $34{\mu}A$/decade 였다.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2009년도 학술발표대회
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• pp.63-64
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• 2009

• 한국입자에어로졸학회지
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• 제12권3호
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• pp.65-72
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• 2016

Nanoporous $SiO_2$ particles containing different pore volume and size were prepared from silicic acid by a spray pyrolysis. The pore size, pore volume and particle size could be controlled with varying the precursor concentration, reaction temperature, and amount of organic templates such as Urea and poly ethylene glycol (PEG). The pore size distribution, pore volume and specific surface area of as-prepared particles were analyzed by BET and BJH methods, and the average particle sizes were measured by a laser diffraction method. The nanoporous $SiO_2$ particles ranged $0.6-0.9{\mu}m$ in diameter were successfully synthesized and the average particle size increased as the silicic acid concentration increased. The morphology of nanoporous $SiO_2$ particles was spherical and pores ranged 1 - 40 nm in diameter were measured in the particles. In case of Urea added into silicic acid, it showed no much difference in the morphology, pore size and pore volume at different Urea concentration. On the other hand, when PEG was added, it was clearly observed that pore diameter and pore volume of the particles surface increased with respect to PEG concentration.