• 분석과학
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• 제12권2호
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• pp.89-93
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• 1999

적은 양의 시료를 분석할 수 있는 마이크로 컬럼 이온 크로마토그래피용 전도도 셀과 억압컬럼을 개발하였다. 안지름이 작은 모세관 컬럼을 사용하는 경우 이동상의 유속은 보통 $5{\sim}20{\mu}L/min$ 정도 된다. 따라서 이 경우 일반적인 전도도 셀은 사용할 수가 없기에 내부 부피가 작은 모세관 컬럼용 전도도 셀과 억압컬럼을 제작하였다. 전도도 셀은 두 개의 백금 피하주사 바늘을 안지름이 0.010 mm인 튜브 속에 넣어 간격이 $2{\mu}m$ 되게 만들었고, 억압컬럼은 Nafion 튜브를 이용하여 막-억압컬럼 형태로 개발하였다. 이 전도도 셀과 억압컬럼을 이용하여 실제 음이온들(플루오르화물, 아질산염, 질산염, 염소산염)을 분석한 결과 재현성 있고 양호한 크로마토그램을 얻었다.

• 분석과학
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• 제13권6호
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• pp.775-780
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• 2000

고온에서 용융된 유리의 전기 전도도를 측정하였다. 유리의 전기 전도도는 유리의 물성 연구와 유리 제조 공정에서 공정 조건을 조절하기 위하여 중요하게 사용되는 용융물의 물리적 성질이다. 그러나 고온의 용융물은 수용액에서 사용하는 전도도 셀을 사용할 수 없기 때문에 고온의 전도도를 직접 측정할 수 있는 백금 도가니와 막대로 구성된 전도도 셀을 구성하고 유리 용융액의 전도도를 측정하였다. 전도도 셀의 상수를 구하기 위하여 융융 유리와 전도도가 유사하도록 KCl의 수용액을 사용하였다. 교류 1 kHz의 사인파 발생기와 연산증폭기로 구성된 회로를 사용하고 용액의 전도도에 따른 출력 전위를 측정하여 전기 전도도와 셀 상수를 구하였으며, 고온에서 사용하기에 적합한 전도도 셀 형태를 결정하였다. 측정하는 Cell의 크기와 용기의 크기, Cell이 들어가는 깊이, 전극의 형태를 달리하여 측정한 결과를 비교하였다. 시험 측정한 붕규산염 유리의 고온 용융물의 전기 전도도는 $1,450^{\circ}C$에서 $0.053{\Omega}^{-1}cm^{-1}$이었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권6호
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• pp.331-334
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• 2002

Culture conductivity and on-line NADH fluorescence were used to measure cellular growth in plant cell suspension cultures of Podophyllum hexandrum. An inverse correlation between dry cell weight and medium conductivity was observed during shake flask cultivation. A linear relationship between dry cell weight and culture NADH fluorescence was obtained during the exponential phase of batch cultivation In a bioreactor under the pH stat (pH 6) conditions. It was observed that conductivity measurement were suitable for biomass characterisation under highly dynamic uncontrolled shake flask cultivation conditions. However, if the acid/alkali feeding is done for pH control the conductivity measurement could not be applied. On the other hand the NADH fluorescence measurement allowed online-in situ biomass monitoring of rather heterogenous plant cell suspension cultures in bioreactor even under the most desirable pH stat conditions.

• 한국임상수의학회지
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• 제15권2호
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• pp.242-246
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• 1998

These studies were Performed to provide some basic informations for developing an automatic system in dairy farming in order that the farmers may easily and automatically detect the mastitis. Electrical conductivity of each milk sample was measured by micro-ohm meter and also the number of somatic cell was detected by somecounter. The major microorganisms causing mastitis were also investigated. The rate of infected cattle with mastitis was 33.0% among 2,540 dairy cattle and the rate of infected quarters with mastitis was 13.9 % among 9.660 quarters. When the number of somatic cell was under lost electrical conductivity of the milk was 0.073, whereas number of somatic cell was over $3{\times}10^{6}$, electrical conductivity was increased by 0.167. When electrical conductivity of milk was over 0.073, the cattle was diagnosised as mastitis. The major micmorganisms of mastitis were Staphylococcus spp. (55-60%) and Streptococcus spp. (15-20%).

• Journal of Electrochemical Science and Technology
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• 제11권2호
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• pp.132-139
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• 2020

Solid oxide fuel cells (SOFCs) are among one of the promising technologies for efficient and clean energy. SOFCs offer several advantages over other types of fuel cells under relatively high temperatures (600℃ to 800℃). However, the thermal behavior of SOFC stacks at high operating temperatures is a serious issue in SOFC development because it can be associated with detrimental thermal stresses on the life span of the stacks. The thermal behavior of SOFC stacks can be influenced by operating or material properties. Therefore, this work aims to investigate the effects of the thermal conductivity of each component (anode, cathode, and electrolyte) on the thermal behavior of samarium-doped ceria-based SOFCs at intermediate temperatures. Computational fluid dynamics is used to simulate SOFC operation at 600℃. The temperature distributions and gradients of a single cell at 0.7 V under different thermal conductivity values are analyzed and discussed to determine their relationship. Simulations reveal that the influence of thermal conductivity is more remarkable for the anode and electrolyte than for the cathode. Increasing the thermal conductivity of the anode by 50% results in a 23% drop in the maximum thermal gradients. The results for the electrolyte are subtle, with a ~67% reduction in thermal conductivity that only results in an 8% reduction in the maximum temperature gradient. The effect of thermal conductivity on temperature gradient is important because it can be used to predict thermal stress generation.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.35-35
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• 2017

How do plants take up water from soils especially when water is scarce in soils? Plants have a strategy to respond to water deficit to manage water necessary for their survival and growth. Plants regulate water transport inside them. Water flows inside the plant via (i) apoplastic pathway including xylem vessel and cell wall and (ii) cell-to-cell pathway including water channels sitting in cell membrane (aquaporins). Water transport across the root and leaf is explained by a composite transport model including those pathways. Modification of the components in those pathways to change their hydraulic conductivity can regulate water uptake and management. Apoplastic barrier is modified by producing Casparian band and suberin lamellae. These structures contain suberin known to be hydrophobic. Barley roots with more suberin content from the apoplast showed lower root hydraulic conductivity. Root hydraulic conductivity was measured by a root pressure probe. Plant root builds apoplastic barrier to prevent water loss into dry soil. Water transport in plant is also regulated in the cell-to-cell pathway via aquaporin, which has received a great attention after its discovery in early 1990s. Aquaporins in plants are known to open or close to regulate water transport in response to biotic and/or abiotic stresses including water deficit. Aquaporins in a corn leaf were opened by illumination in the beginning, however, closed in response to the following leaf water potential decrease. The evidence was provided by cell hydraulic conductivity measurement using a cell pressure probe. Changing the hydraulic conductivity of plant organ such as root and leaf has an impact not only on the speed of water transport across the plant but also on the water potential inside the plant, which means plant water uptake pattern from soil could be differentiated. This was demonstrated by a computer simulation with 3-D root structure having root hydraulic conductivity information and soil. The model study indicated that the root hydraulic conductivity plays an important role to determine the water uptake from soil with suboptimal water, although soil hydraulic conductivity also interplayed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.306-308
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• 2007

Poly(ethylene glycol) dimethyl ether (PEGDME)/fumed silica/ 1-methyl -3-propylimidazolium iodide (MPII)/$I_2$ mixtures were used as polymer electrolytes in solid state dye-sensitized solar cells (DSSCs). The contents of MPII were changed and the concentration of $I_2$ was fixed at 0.1 mole% with respect to the MPII. The maximum ionic conductivity was obtained at [EG]:[MPII]:[$I_2$]=10:1.5:0.15. It was supposed that the maximum of ionic conductivities would match with that of cell efficiencies, if the ionic conductivity is a rate determining step in the sol id state DSSCs. However, the maximum composition did not show the maximum solar cell performance, indicating the mismatch between ionic conductivity and cell performance. This suggests that the ionic conductivity may not be the rate controlling step in determining the cell efficiency in these experimental conditions, whereas other parameters such as the electron recombination might play an important role. Thus, we tried to modify the surface of the $TiO_2$ particles by coating a thin metal oxide such as $Al_2O_3$ or $Nb_2O_5$ layer to prevent electron recombination. As a result, the maximum of the cell efficiency was shifted to that of the ionic conductivity. The peak shifts were also attempted to be explained by the diffusion coefficient and the lifetime of electrons in the $TiO_2$ layer.

• Macromolecular Research
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• 제17권1호
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• pp.44-50
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• 2009

Rigid polyurethane foams (PUF)s were synthesized with environmentally friendly blowing agents such as a cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only for four different silicone surfactants having different silicone/polyether ratios. An attempt was made to reduce the thermal conductivities of the PUF samples by varying the concentration and the silicone/polyether ratio of the various silicone surfactants. The scanning electron microscopy (SEM) results indicated an optimum concentration of the silicone surfactant of about 1.5 to 2.5 phpp for various surfactants to reduce the cell size and lower the thermal conductivity. The silicone surfactant having a higher silicone/polymer ratio showed a smaller cell size and, therefore, demonstrated the lower thermal conductivity of the PUF samples. From the relation between the thermal conductivity and the cell size of the PUF samples, the smaller cell size improved the thermal insulation property of the rigid PUF for both the PUF samples blown by the cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only. If the blowing agent is fixed, then the cell size is an important factor to decrease the thermal conductivity of the PUF samples. These results indicated that rigid PUF samples having lower thermal conductivity can be obtained by choosing a silicone surfactant containing a higher silicone/polyether ratio, as well as an optimum content of the surfactant.

• Journal of Microbiology and Biotechnology
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• 제13권5호
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• pp.641-646
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• 2003

An accurate and efficient method for measuring the mass of hairy roots using conductometry is established. A conductivity equation expressed in terms of the concentration of the ion species in the medium is suggested. By using this equation, the effect of the individual ions on the total conductivity can be quantitatively analyzed. An equation for the in situ estimation of the cell growth coefficient for determining the mass of hairy roots is established based on measurements of the nitrogen concentration and conductivity during cultivation. The proposed equation does not require preliminary experiments to determine the cell growth coefficient. Instead, the physiological characteristics of the plant species are reflected by introducing the cellular nitrogen content. Since the cell growth coefficient is determined by measuring the major ionic nutrient concentrations, it is more effective to express the dynamics of an actual culture system. This improved method for determining the mass of hairy roots was successfully utilized in a fed-batch culture system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.2137-2139
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• 2004

Cancer cell lysis at pulsed DC is realized using micromachined electrodes. In this research, quantitative analyses are performed on cell lysis results. The cell volume increasing at the pulses applied are analyzed in different medium conditions on osmotic pressure and conductivity, and the cell lysis procedures are studied in detail experimentally. Phosphate buffered saline (PBS) is used as the medium. To change the conductivity of PBS, NaCl concentration of PBS is adjusted, and inositol is used with PBS to control the effects of the osmotic pressure to cell lysis performance.