• 공업화학
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• 제19권4호
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• pp.370-375
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• 2008

비수계 분산(NAD : non-aqueous dispersion) 중합을 이용하여 친환경적인 아크릴 수지를 합성시 최적의 중합조건에 대해 연구하였다. 중합된 고분자 입자들 간의 응집을 방지하기 위한 안정제의 적정량은 20 wt%로 나타났고 안정된 NAD 상태를 유지하기 위한 혼합 용매의 적정 혼합비는 지방족과 방향족 용매의 비율이 80 : 20인 것으로 나타났다. NAD 수지의 점도는 반응시간뿐만 아니라 개시제의 양 및 교반 속도 등에 의해 영향을 받는 것으로 나타났다. 또한 NAD 수지의 입자 크기 및 분포도, 안정제의 양, 개시제의 농도 등에 의해 영향을 받는 것을 확인하였다. 단량체의 투입시기는 단량체를 초기에 모두 투입하면 용매의 극성이 증가하여 입자의 크기가 커져서 입자의 안정성이 저하되므로 단계별로 지속적으로 투입할 필요가 있는 것으로 관찰되었다.

• 청정기술
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• 제13권3호
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• pp.208-214
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• 2007

본 연구에서는 비수계 분산중합(NAD)을 이용하여 $0.1\;{\mu}m$에서 $1\;{\mu}m$ 크기의 입자를 가지는 환경친화적인 아크릴 수지를 제조하였다. 1 단계에서 안정제를 제조한 후 2 단계에서 안정제에 아크릴 단량체를 투입하여 NAD수지를 제조하였다. 적정 점도의 NAD수지를 합성하려면 안정제도 1000 cP 이상의 점도를 가진 것을 사용하여야 하는 것으로 나타났고 이를 위해서는 안정제 중합 시 단량체와 개시제를 단계적으로 투입하는 것이 필요한 것으로 관찰되었다. 또한 NAD수지 중합시 안정제의 양은 적정량을 투입하는 것이 필요하고 적정량 이상에서는 더 이상 NAD수지의 점도가 증가하지 않는 것으로 나타났다. 중합 단량체의 조성 선택 시에도 용해도 상수 차이 등의 요인으로 입도분포가 두 가지로 나올 수 있으므로 이를 고려하여 단량체를 투입하여야 하는 것으로 관찰되었다.

• 한국재료학회지
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• 제13권11호
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• pp.725-731
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• 2003

The effect of organic processing parameters on the dispersion stability of the BaTiO$_3$-based dielectric particles and borosilicate glass particulate suspensions was investigated in a system where organic solvents, dispersant, binder and modifier were used as processing additives in a low temperature cofired ceramic fabrication processes. Two- and three-component organic solvents were used to disperse ceramic particles and it was found the better stability in the particulate suspension prepared in a bi-solvent, which was consists of toluene and ethanol in a non-azeotropic composition. The addition amount of organic additives had a great impact on dispersion in the present investigation. The flow curves of the suspensions prepared with binder and modifier were fitted according to the power-law equation, which indicates that the internal structure of the suspension could be disturbed under the applied shear stress. Finally, the LTCC green tapes were successfully tape-cast based upon the optimum formulation of LTCC suspension and its microstructure was compared with that of the hard-agglomerates.

• 약학회지
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• 제57권4호
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• pp.258-264
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• 2013

Herbal medicine has been traditionally used in Asian countries for a long time. Many pharmacological effects are identified in the herbs and these herbs are believed to be safe for human. However, the safety or adverse effect of some traditional herbal medicines has not been established. We have chosen Cyperi rhizoma based on the Korea Herbal Pharmacopoeia and which have been widely used for an anti-inflammatory effect in Korea. The object of the study was to evaluate safety of Cyperi rhizoma in rats. The aqueous extract of Cyperi rhizoma was prepared according to the standard hot water extraction method of the Korea Pharmacopoeia. In the sub-chronic study, the aqueous extract of Cyperi rhizoma was orally administered once daily as 0, 125, 250, 500, 1000 and 2000 mg/kg/day to male and female F344 rats for 13 weeks. There were no treatment related abnormalities in mortality, clinical signs, food consumption, ophthalmologic examination, hematology, serum chemistry, urinalysis, gross observation, organ weight and histopathologic examination. In conclusion, The NOAEL (No Observed Adverse Effect Level) for Cyperi rhizoma aqueous extract was determined as more than 2000 mg/kg/day in the present experimental condition.

• 자원리싸이클링
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• 제27권4호
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• pp.29-35
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• 2018

본 연구에서는 네오디뮴의 상온제련의 가능성을 알아보기 위하여 비수계 전해액에서 네오디뮴의 전기화학적 레독스 거동을 조사하였다. 비수계 전해질로는 이온성액체인 $[C_4mim]PF_6$, $[C_4mim]Cl$, $[P_{66614}]PF_6$와 함께 네오디뮴 염에 대한 용해도가 높은 에탄올과 전기화학적 안정성이 높은 탄산염계 유기용액을 기반으로 한 혼합전해질을 대상으로 하였다. 다른 전해액에 비하여 ethylene carbonate(EC)/di-ethylene carbonate (DEC)의 경우가 네오디뮴의 전기화학적 레독스 특성이 우수한 것으로 판단되었으며, 물성향상을 위하여 에탄올을 첨가하는 실험을 수행하였다. 순수한 1 : 1 EC/DEC와 에탄올의 혼합 비율, 그리고 $NdCl_3$의 농도에 따른 이온전도도를 측정한 결과, 에탄올 함량 50 vol%, $NdCl_3$ 농도 0.5 M에서 전해질 특성이 가장 우수한 것으로 판단된다. 순환전위법과 선형전위법을 이용해 -3.8 V (vs. Pt-QRE)에서 네오디뮴의 환원반응으로 추정되는 전류피크가 관찰된다. 상온에서 -6 V (vs. Pt-QRE)에서 18시간 동안 정전압법으로 전해한 결과, 금속 네오디뮴이 전착되었음을 확인하였다.

• 청정기술
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• 제25권3호
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• pp.206-222
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• 2019

최근에는 다양한 다상오염물 거동 흐름 모델들이 개발되었고 일부는 상용화되기도 하였으나, 대부분이 압력기저접근방식을 갖고 개발된 프로그램들이므로 다양한 수치적 어려움을 내재하고 있다. 이러한 수치적 어려움을 극복하기 위해서는 분율흐름접근방식을 따르는 기존 다상흐름거동 수치모델로 개발된 MultiPhaSe flow (MPS) 모델에 계면활성제에 의한 용해 현상을 모사할 수 있는 오염물 거동 모듈을 결합해서 MultiPhaSe flow and TranSport (MPSTS) 프로그램을 본 연구에서 개발하였다. 개발된 모델은 Clement의 해석 해를 사용하여 검증하였다. 여기서 MPSTS프로그램은 입자추적법과 결합한 라그랑지안-율러리안 기법을 이용해서 상간물질전달 효과와 다상내 오염물 거동 기능을 결합한 계면활성제 활용 복원과정을 모사할 수 있는 프로그램이다. 본 연구에서는 개발된 모델을 이용해서 소수성 액체(non aqueous phase liquid, NAPL)로 오염된 지역의 계면활성제에 의한 오염 정화 시 층상구조를 가지는 수리지질학적 불 균질성이 복원효율에 미치는 영향을 수치 모의 하였다. 수치모의 결과, 하부 층의 수리전도도가 상부 층의 수리전도도보다 10배, 20배, 50배로 큰 경우에 대해서 하부에서 물속에 용해된 디젤의 농도가 높게 나타난다. 왜냐하면 계면활성제가 하부 층을 따라서 좀 더 빨리 움직여서 하부 층에서 잔류 소수성 액체를 좀 더 많이 용해시켰기 때문이다.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1640-1644
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• 2011

Water-soluble mutant of intrinsically insoluble protein, crambin, was produced by mutagenesis based on the sequence analysis with homologous proteins. Thr1, Phe13, and Lys33 of crambin were substituted for Lys, Tyr, and Lys, respectively. The resultant mutant was soluble in aqueous buffer as well as in dodecylphosphocholine (DPC) micelle solution. The $^1H-^{15}N$ spectrum of the mutant crambin showed spectral similarity to that of the wild-type protein except for local regions proximal to the sites of mutation. Solution structure of water-soluble mutant crambin was determined in aqueous buffer by NMR spectroscopy. The structure was almost identical to the wild-type structure determined in non-aqueous solvent. Subtle difference in structure was very local and related to the change of the intra- and inter-protein hydrophobic interaction of crambin. The structural details for the enhanced solubility of crambin in aqueous solvent by the mutation were provided and discussed.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권3호
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• pp.110-117
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• 2006

Ice adhesion or cohesion leads to the decrease of the performance of ice making system, especially to dynamic type ice thermal storage system (DISS) which mainly forms ice from the flow of an aqueous solution. The ice adhesion is influenced by various parameters associated with operating or geometric condition. In this study, the influence on an adhesion of ice to the characteristic of cooling surface and to composition of an aqueous solution was fundamentally observed by using batch type cooling device,. a beaker. Three patterns of solution in each beaker were cooled with brine. Moreover, the characteristic of cooling surface on each beaker was distinguished to coating materials. Stirring power as a degree of the ice adhesion was measured. The stirring power to cooling heat transfer rate in each beaker was compared. As a result, the lowest stirring power of 8.9 W with non-adhesion of ice, was shown in the case of the aqueous solution of EG(4) + PG(1.5) + 1,6HD(1.5). in PE coating beaker.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1129-1133
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• 2004

The effects of Pluronic F-68, a non-ionic surfactant, on the growth and physical characteristics of Digitalis lanata suspension cultures were investigated in aqueous two-phase systems (ATPSs) composed of $4.5\%$ polyethylene glycol (PEG) 20,000 and $2.8\%$ crude dextran. In the range of 0.1-10.0 g $1^{-1}$, Pluronic F-68 enhanced the maximum cell density in a medium with ATPSs, even though Pluronic F-68 did not affect cell growth in a normal growth medium. In terms of physical properties of ATPSs with cell suspension cultures, 0.2 g $1^{-1}$ of Pluronic F-68 reduced viscosity by up to $40\%$, while 0.1 g $1^{-1}$ of Pluronic F-68 significantly enhanced the oxygen transfer rate. In addition, we successfully performed aqueous two-phase cultivation in a 5-1 stirred tank bioreactor with 0.5 g $1^{-1}$ of Pluronic F-68, and discovered that cell growth in ATPSs was similar to that in normal growth medium.

• Membrane and Water Treatment
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• 제13권3호
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• pp.129-137
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• 2022

In this study, the removal of Ciprofloxacin (CPX) from aqueous solutions was investigated by a new activated carbon adsorbent prepared from orange peel (ACOP) with chemical activation using ZnCl₂. The physicochemical properties of orange peel activated carbon were characterized by proximate and ultimate analysis, scanning electron microscopy, BET surface area determination and Fourier transformation infrared spectroscopic studies. According to Brunauer-Emmett-Teller isotherm and non-local-density functional theory, the cumulative surface area, pore volume and pore size of ACOP were determined as 1193 m² g^-1, 0.83 cc g^-1 and 12.7 Å, respectively. The effects of contact time, pH, temperature and ACOP dose on the batch adsorption of CPX were studied. Adsorption equilibrium data of CPX with ACOP were found to be compatible with both the Langmuir and Freundlich isotherms. CPX adsorption capacity of ACOP was calculated as 181.8 mg g^-1 using Langmuir isotherm. The CPX adsorption kinetics were found to be harmonious with the pseudo-second-order kinetic model. Conclusively, ACOP can be assessable as an effective adsorbent for the removal of ciprofloxacin (CPX) from aqueous solutions.