• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.611-614
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• 2003

p-KG03의 고유점도는 65.22 및 50.75 $d{\ell}/g$ 이며, 사슬강도성은 0.170이였고, 특성화 농도는 0.114 g/l이었다. p-KG03은 non-Newtonic fluid로 Power-Low Model에 의한 pseudoplastic한 물성을 갖으며, 유체성으로 p-KG03 1%의 constancy index (K)는 2,172 cp, flow behavior index (n)는 0.52이었다. 특히 pH, 염 및 열에 안정하며 기존 다당류와의 혼합이용 가능성이 있을 것으로 생각된다.

• 대한기계학회논문집B
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• 제22권4호
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• pp.489-498
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• 1998

Among the heat/mass exchange units composing an absorption system, the absorber, where the refrigerant vapor is absorbed into the liquid solution is the one least understood. In the present study, the effects of non-absorbable gas on the absorption process of aqueous lithium bromide solution falling film inside a vertical tube were experimentally investigated. In the range of film Reynolds number of 30 ~ 195, heat and mass transfer characteristics were investigated as a function of non-absorbable gas volumetric concentration, 0.2 ~ 20%. An increase of non-absorbable gas volumetric concentration degraded the mass transfer rate dramatically in the absorption process. The reduction of mass transfer rate was significant for the addition of small amount of non-absorbable gas to the pure vapor. At film Reynolds number of 130, an increase of non-absorbable gas concentration from 0.2 to 6.0% resulted in the decrease of mass transfer rate by 36% and 20% of non-absorbable gas by 59%. However the decrease of film Nusselt number with the increase of volumetric concentration of non absorbable gas was relatively smaller than the decrease of Sherwood number. Critical film Reynolds number was identified to exist for the maximum heat and mass transfer regardless of the volumetric concentration of non-absorbable gases.

• 한국결정성장학회지
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• 제18권3호
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• pp.131-135
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• 2008

본 연구에서는 합성운모에 대한 코팅기술을 확립한 뒤, 비수성을 나타내는 합성운모를 제조하였다. 합성운모의 표면코팅은 고속교반기를 사용하여 행하였으며, 스테아린산으로 코팅된 합성운모의 특성은 침적실험, XRD 및 SEM을 이용하여 분석하였다. 본 연구 결과, 교반기의 내부온도는 $70^{\circ}C$를 유지하고, 10분 동안 1600 rpm/min을 행함으로써 운모 표면에 스테아린산의 코팅이 가능하였다. 또한 SEM 관찰결과로부터, 스테아린산과 운모의 혼합비율, 교반기 내부온도, 회전속도에 의해 특성이 변화하는 반면 코팅처리시간과는 무관함을 알 수 있었다.

• 청정기술
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• 제17권2호
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• pp.150-155
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• 2011

본 연구에서는 수용액상의 금속이온을 기능화된 구형의 실리카 담체를 이용하여 제거하는 공정에 대하여 유한 차분법을 이용하여 모사하였다. 평형 모델과 비평형 모델을 수립하여 무차원 변수와 각종 변수에 대한 영향을 살펴보았으며 평형 모델과 비평형 모델의 결과를 비교하였다. 평형모델의 경우 Freundlich 등온식을 사용하였으며 비평형 모델의 경우 1차 반응속도를 가정하였다. 평형모델과 비평형 모델의 경우 변수값에 따라 비슷한 경향을 나타내었으며 금속이온 제거공정의 효율을 예측할 수 있었다. 문헌에 제시된 실험값을 활용하여 평형 모델의 예측 결과를 비교한 결과 부합되는 결과를 나타내었다.

• 청정기술
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• 제12권4호
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• pp.250-258
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• 2006

CFC-113과 1,1,1-trichloroethane 등과 같은 CFC 화합물은 화학적 안정성 및 열역학적 특성 등이 우수하고, 불연성이며, 부식성이 없는 화합물로 오랜 시간 동안 전 산업에 걸쳐 널리 사용 되어 왔다. 하지만, 1989년 지구 환경의 보호를 위해 이들의 생산과 사용을 규제하는 국제협약인 '오존층 파괴물질에 관한 몬트리올 의정서'가 체결되어 대체 세정제가 요구되고 있다. 본 연구에서는 세정 시스템을 변화시키지 않고 세정력이 우수하면서 환경 친화적이며 인체 유해도가 낮으며 부식성 물질을 발생 시키지 않는 비수계 세정제를 개발하고자 하였다. 이를 위하여 글리콜 에테르계의 용매와 파라핀계 탄화수소 물질을 일정 비율로 혼합, 배합하면서 실록산을 첨가하여 비수계 세정제를 배합 제조하였다. 그리고 이들 세정제의 물성과 세정성을 평가하여 대체 세정제로서의 가능성을 평가하였다. 배합세정제의 물성측정 결과 밀도와 표면장력이 낮아 오염물에 대한 침투력이 우수할 것으로 예상되었고 인화점과 증기압 측정값으로 세정제의 안전성을 평가할 수 있었다. 플럭스, 솔더 및 그리스에 대한 세정성능 측정결과 높은 세정성능을 보여주었고 피세정물의 표면에 잔류물이 생성되지 않았다. 결과적으로, 규제물질과 동등한 세정능력을 지니며 침투력이 우수하고 인체 유해도가 낮은 세정제를 개발할 수 있었다.

• Carbon letters
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• 제12권3호
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• pp.180-183
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• 2011

Li metal is accepted as a good counter electrode for electrochemical impedance spectroscopy (EIS) as the active material in Li-ion and Li-ion polymer batteries. We examined the existence of signal noise from a Li-metal counter quantitatively as a preliminary study. We suggest an electrochemical cell with one switchable electrode to obtain the exact impedance signal of active materials. To verify the effectiveness of the switchable electrode, EIS measurements of the solid electrolyte interphase (SEI) before severe $Li^+$ intercalation to SFG6 graphite (at > ca. 0.25 V vs. Li/$Li^+$) were taken. As a result, the EIS spectra without the signal of Li metal were obtained and analyzed successfully for the following parameters i) $Li^+$ conduction in the electrolyte, ii) the geometric resistance and constant phase element of the electrode (insensitive to the voltage), iii) the interfacial behavior of the SEI related to the $Li^+$ transfer and residence throughout the near-surface (sensitive to voltage), and iv) the term reflecting the differential limiting capacitance of $Li^+$ in the graphite lattice.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.214.2-214.2
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• 2011

In this work, porous carbon based electrodes are prepared by carbonization using poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composites to further increase the specific capacitance for supercapacitors. Electrode materials investigate the aspects of specific capacitance, pore size distribution and surface area: influence of carbonization temperatures of PVDF/CNT composites. The electrochemical properties are investigated by cyclic voltammetry, impedance spectra, and galvanostatic charge-discharge performance with in $TEABF_4$ (tetraethylammonium tetrafluoroborate)/acetonitrile as non-aqueous electrolyte. From the results, the highest value of specific capacitance of ~101 $F{\cdot}g^{-1}$ is obtained for the samples carbonized at $600^{\circ}C$. Furthermore, pore size of samples control be low 7 nm through carbonization process. It is suggested that micropores significantly contribute to the specific capacitance, resulting from improved charge transfer.

• Bulletin of the Korean Chemical Society
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• 제9권4호
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• pp.248-251
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• 1988

Mechanism of electrochemical polymerization of pyrrole (Py) on a Pt electrode in acidic aqueous solutions was studied by means of potentiostatic measurements, cyclic voltammetry and chronopotentiometry. Pyrrole molecule appeared to be initially oxidized via two-electron transfer step to produce oxidized pyrrole ion ($Py^+$), which was coupled with a non-oxidized pyrrole to yield a dimerized species, Py-Py. The Py-Py thus formed was further oxidized again via two-electron transfer step, which was followed by coupling with non-oxidized monomer and by concomitant expulsion of a $H^+$. Then the latter chain extension process was repeated. The chain extension and polypyrrole oxidation reactions occurred competitively.

• Journal of Pharmaceutical Investigation
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• 제29권3호
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• pp.193-203
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• 1999

In order to investigate systematically the steady shear flow properties of aqueous po1y(ethylene oxide) (PEO) solutions having various molecular weights and concentrations, the steady flow viscosity has been measured with a Rheometrics Fluids Spectrometer (RFS II) over a wide range of shear rates. The effects of shear rate, concentration, and molecular weight on the steady shear flow properties were reported in detail from the experimentally measured data, and then the results were interpreted using the concept of a material characteristic time. In addition, some flow models describing the non-Newtonian behavior (shear-thinning characteristics) of polymeric liquids were employed to make a quantitative evaluation of the steady flow behavior, and the applicability of these models was examined by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) At low shear rates, aqueous PEO solutions show a Newtonian viscous behavior which is independent of shear rate. At shear rate region higher than a critical shear rate, however, they exhibit a shear-thinning behavior, demonstrating a decrease in steady flow viscosity with increasing shear rate. (2) As an increase in concentration and/or molecular weight, the zero-shear viscosity is increased while the Newtonian viscous region becomes narrower. Moreover, the critical shear rate at which the transition from the Newtonian to shear-thinning behavior occurs is decreased, and the shear-thinning nature becomes more remarkable. (3) Aqueous PEO solutions show a Newtonian viscous behavior at shear rate range lower than the inverse value of a characteristic time $1/{\lambda}_E$, while they exhibit a shear-thinning behavior at shear rate range higher than $1/{\lambda}_E$. For aqueous PEO solutions having a broad molecular weight distribution, the inverse value of a characteristic time is not quantitatively equivalent to the critical shear rate, but the power-law relationship holds between the two quantities. (4) The Cross, Carreau, and Carreau-Yasuda models are all applicable to describe the steady flow behavior of aqueous PEO solutions. Among these models, the Carreau-Yasuda model has the best validity.

• 한국막학회:학술대회논문집
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• 한국막학회 2001년도 춘계 총회 및 학술발표회(한국막학회)
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• pp.80-83
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• 2001