• 한국세라믹학회지
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• 제44권8호
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• pp.424-429
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• 2007

Novel conductive $CO_2$ membranes composed of dual phases, molten carbonates and electronic conducting ceramics, were investigated. As the microstructure control of electronic conducting ceramic supports is extremely important to keep the molten carbonates stable in the membranes by a capillary force applied by the pore structure of the supports, we have scrutinized the microstructure of the electronic conducting supports utilizing microscopic images and gas permeability measurement. From the evaluation of the electrical conductivities of the molten carbonates and the electronic conducting ceramic supports, we found that the ionic conductivity of the molten carbonates could determine $CO_2$ flux through the dual phase membranes if the surface exchange rate were relatively high enough.

• 전기화학회지
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• 제6권3호
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• pp.174-177
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• 2003

Electric double-layer capacitors based on charge storage at the interface between a high surface area activated carbon electrode and an electrolyte solution are characterized by their long cycle-life and high power density in comparison with batteries. However, energy density of electric double-layer capacitors obtained at present is about 6 Wh/kg at a power density of 500W/kg which is smaller as compared with that of batteries and limits the wide spread use of the capacitors. Therefore, a new capacitor that shows larger energy density than that of electric double-layer capacitors is proposed. The new capacitor is the hybrid capacitor consisting of activated carbon cathode, carbonaceous anode and an organic electrolyte. Maximum voltage applicable to the cell is over 4.2V that is larger than that of the electric double-layer capacitor. As a result, discharged energy density on the basis of stacked volume of electrode, current collector and separator is more than 18Wh/l at a power density of 500W/l.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권4호
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• pp.147-155
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• 2006

The drag reduction (DR) and heat transfer efficiency reduction (ER) of non-ionic surfactant were investigated as a function of fluid velocity, temperature, and surfactant concentration. An experimental apparatus consisting of two temperature controlled water storage tanks, pumps, test specimen pipe and the piping network, two flow meters, two pressure gauges, a heat exchanger, and data logging system was built. From the experimental results, it was concluded that existing alkyl ammonium surfactant (CTAC Cethyl Trimethyl Ammonium Chloride) had DR of $0.6{\sim}0.8$ at $1,000{\sim}2,000ppm$ concentration with fluid temperature ranging between $50{\sim}60^{\circ}C$. However, the DR was very low when the fluid temperature was $70{\sim}80^{\circ}C$. The new amine oxide and betaine surfactant(SAOB Stearyl Amine Oxide + Betaine) had lower DR at fluid temperatures ranging between $50{\sim}60^{\circ}C$ compared with CTAC. However, with fluid temperature ranging between $70{\sim}80^{\circ}C$ the DR was $0.6{\sim}0.8$ when the concentration level was $1,000{\sim}2,000ppm$.

• 펄프종이기술
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• 제44권4호
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• pp.25-31
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• 2012

Ionic trash in furnish decreases retention and drainage performance of the microparticle retention system using recycled fibers in closed papermaking system. Two retention systems, such as the microparticle system and the PEO/cofactor system, were compared and analyzed to improve retention. The PEO/cofactor system achieved similar retention performance at low addition level as the microparticle system. Optimum ratio of PEO/cofactor dual polymer system was 1:10. Ash retention was increased when using the fixing agent. As the TMP ratio increased, the PEO/cofactor system was more efficient in retention and drainage than the other system. The high molecular weight and non-ionic polymer retention system had less effect on flocculation hindrance than the traditional electrostatic retention system.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.312-317
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• 1985

${\beta}$-Glucuronidase (EC 3.2.1.31) which hydrolizes D-glucuronate from ${\beta}$-D-glucuronide was purified from rat liver, using ammonium sulfate fractionation, DEAE-cellulose chromatography, Concanavalin-A Sepharose 4B chromatography and gel filtration on Sephadex G-200. This enzyme has the molecular weight of 280,000 daltons by gel filtration and 75,000 daltons by SDS-polyacrylamide gel electrophoresis. As its funtion is reverse of detoxification in the liver, the inhibition of the enzyme was tested with extracts of several food products and medicinal herbs, some are known as anti-cancer agents. Among them, Panax ginseng and Cortnellus shiiake inhibited the enzyme competitively and the $K_1$ values were $9.22 {\times}\;10^{-2}$ and 0.102 mg/ml, respectively. These inhibitors strongly bound to DEAE-cellulose. The negatively charged amino acids, L-aspartate and L-glutamate, inhibited the enzyme, and $K_1$ value of L-aspartate was 0.80 mM. The interaction between ${\beta}$-glucuronidase and p-nitrophenyl-${\beta}$-D-glucuronide was found to involve ionic forces by the effect of ionic strength on the kinetic constant, Vmax/Km. It was inferred from these findings that cationic group at the active center of the enzyme is probably involved in attacking the substrate.

• 한국과학교육학회지
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• 제27권8호
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• pp.677-692
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• 2007

In this study, university students were provided with repeated opportunities to represent their ideas graphically, and to examined via their drawings the extent to which they could visualize macroscopic phenomena microscopically. These drawings provided insight into the students' basic understanding of solution chemistry, revealing three conceptual models: the Undifferentiated Symbolic Model, the Particulate Model, and the Symbolic Ionic Model. Generally speaking, students who had poor conceptual understanding tended to exhibit the Undifferentiated Symbolic Model, whereas students with deeper understanding tended to employ the Symbolic Ionic Model. Students' conceptual comprehension was predictable from their graphical representations, which better elucidated what they actually comprehended about the phenomena, as opposed to their ambiguous verbal descriptions alone. The results of this study demonstrated a lack of development in university students' conceptions of solutions. Their weakness in understanding at the molecular-level became more obvious when they were asked to represent their ideas in drawings. Few students exhibited expert knowledge, and several common misconceptions were found, which indicated typical difficulties students have perceiving common phenomena at the molecular level. The findings of this study illustrate how eliciting graphical representations can be used to assess students' conceptual understandings.

• 한국식품과학회지
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• 제29권2호
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• pp.320-325
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• 1997

이소말토올리고당의 생산에 사용되는 Aspergillus niger 유래의 TG의 고정화를 위해 여러가지 방법을 비교하여 고정화방법을 선정하였다. 이온결합과 흡착, entrapment, 공유결합과 금속이온을 이용한 결합 등을 이용하여 TG의 고정화를 시도하였다. TG의 고정화를 위해서는 수율면에서 우수하고(61.3%) 간편성도 있는 CNBr-activated sepharose 4B를 이용한 고정화 방법을 선정하였다. DEAE-sephadex를 이용한 이온결합에 의해서는 33.1%, Diaion HP-20를 이용한 흡착법에 의해서는 22.5%의 수율을 보였으나 CNBr-activated sepharose 4B를 이용한 고정화 방법에 비해 수율과 안정성이 낮아 제외하였다. Entrapment에 의한 고정화는 bead내의 확산저항으로 인해 최종산물의 생성에 불리한 것으로 판단되었고 magnesium silicate, silica gel, glass bead 등의 담체를 이용한 고정화방법은 낮은 수율로 인해, 금속이온을 이용한 경우 역시 낮은 수율과 장시간의 준비로 인해 고정화방법으로 부적당하다고 판단되었다.

• 한국대기환경학회지
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• 제31권1호
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• pp.15-27
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• 2015

The collection of fine particulate matter samples was made at Gosan site of Jeju Island, one of the background sites of Korea, during a year of 2013, and their water-soluble ionic species were analyzed in order to examine the chemical compositions and pollution characteristics. The concentrations of $nss-SO_4{^{2-}}$, $NH_4{^{+}}$, $NO_3{^{-}}$, and $K^+$ had occupied 66.0% of water-soluble ionic species in $PM_{10}$, especially 94.3% in $PM_{2.5}$ fine mode, however the $nss-Ca^{2+}$ and $Na^+$ showed high concentrations in $PM_{10-2.5}$ coarse mode. $NO_3{^-}/nss-SO_4{^{2-}}$ concentration ratios in $PM_{10}$ and $PM_{10-2.5}$ were 0.30 and 0.13, showing less significant effect from automobile and local pollution sources. The sulfate and nitrate compounds were presumed to be long-range transported to Gosan area by the relatively high SOR and NOR values. The trajectory cluster analysis showed the higher concentrations of the major secondary pollutants ($nss-SO_4{^{2-}}$, $NO_3{^{-}}$, $NH_4{^{+}}$) and $nss-Ca^{2+}$ when the air masses had moved from China continent and Korean peninsula into Gosan area.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.79-84
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• 2003

The main objective of this study was to investigate the chemical characteristics of post-harvest biomass burning aerosols from field burning of barley straw in late spring and rice straw in late fall in rural area in Korea. 12-hr integrated intensive sampling of $PM_{10}$ and $PM_{2.5}$ biomass burning aerosols had been conducted continuously at Gwangju, Korea 4-15 June 2001 and 8 October-14 November 2002. The fine and coarse particles of biomass burning aerosols were collected for mass, ionic, elemental, and carbonaceous species analysis. Average fine and coarse mass concentrations of biomass burning aerosols were measured to be 129.6, 24.2 ${{\mu}gm}^{-3}$ in June 2001 and 47.1, 33.2 ${{\mu}gm}^{-3}$ in October to November 2002, respectively. Exceptionally high level of $PM_{2.5}$ concentration up to 157.8 ${{\mu}gm}^{-3}$ well above 24-hour standard was observed during the biomass burning event days under stagnant atmosphere condition. During biomass burning periods dominant ionic species were $Cl^{-}$, ${NO_3}^{-}$, ${SO_4}^{2-}$, and ${NH_4}^{+}$ in fine and coarse mode. In the fine mode $Cl^{-}$ and ${KCl}^{+}$ were unusually rich due to the high content of the semiarid vegetation. High OC values and OC/EC ratios were also measured during the biomass burning periods. Increased amount of fine aerosols with high enrichment, which were originated from biomass burning of post-harvest agricultural waste, resulted in extremely severe particulate air pollution and visibility degradation in the region. Particulate matters from open field burning of agricultural wastes cause great adverse impact on local air quality and regional climate.

• 상하수도학회지
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• 제29권1호
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• pp.77-88
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• 2015

Soil column experiments were evaluated effects of silver nanoparticles (i.e., 0, 2.5, 5, and 10 mg/L) on the microbial viability which is strongly associated with the degradation of organic matter, pharmaceutically active compounds(PhACs) and biological oxidation of nitrogenous compounds during river bank filtration. The addition of silver nanoparticles resulted in almost no change in the aqueous matrix. However, the intact cell concentration decreased with addition of silver nanoparticles from 2.5 to 10 mg/L, which accounted for 76% to 82% reduction compared to that of control (silver nanoparticles free surface water). The decrease in adenosine triphosphate was more pronounced; thus, the number and active cells in aqueous phase were concurrently decreased with added silver nanoparticles. Based on the florescence excitation-emission matrix and liquid chromatograph - organic carbon detection analyses, it shows that the removal of protein-like substances was relatively higher than that of humic-like substances, and polysaccharide was substantially reduced. But the extent of those substances removed during soil passage was decreased with the increasing concentration of silver nanoparticles. The attenuation of ionic PhACs ranged from 55% to 80%, depending on the concentration of silver nanoparticles. The attenuation of neutral PhACs ranged between 72% and 77%, which was relatively lower than that observed for the ionic PhACs. The microbial viability was affected by silver nanoparticles, which also resulted in inhibition of nitrifiers.