• Membrane Journal
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• v.34 no.1
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• pp.30-37
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• 2024

As a promising method to address global water scarcity, sorbent-assisted water harvesting from air has shown great potential to deliver drinking water for inlands lacking traditional water sources. In this article, the recent studies of using metal-organic frameworks (MOFs) as sorbents to harvest atmospheric water will be introduced. Compared to the other sorbent materials such as zeolites or silica-based materials, MOFs have shown prospective properties such as the water isotherm inflection points as low as ~10%, which are suitable for harvesting water at dry regions. Due to this property, recently, MOFs have been extensively adopted to develop practical water harvesting devices that can harvest water. Since atmospheric water is accessible anywhere and anytime in the world, this technology is expected to open a new avenue in terms of securing safe water for the future.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.595-604
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• 1992

Carbonate-type polyurethane resins containing anionic moieties were systhesized from NCO-terminated prepolymer method. Membranes were manufactured from the polymer solution and the separation of aqueous ethanol solution was investigated. To enhance the property of urethane resin, carbonate-type polyol(PTMCG) was used. ${\alpha}^{\prime},{\alpha}^{{\prime}{\prime}}$-dimethylolpropionic acid was used as a chain extender to increase the hydrophilicily of the urethane membrane. The ionization of the pendent carboxylic groups in urethane resin was carried out using trimthylamine. To confirm the formation of anionic groups in urethane resin, IR spectra of model compounds were compared with those of urethane resins. It was confirmed that the concentration of hard segment and hydrogen bond contributed to the property of the concentration of hard segment and hydrogen bond contributed to the property of urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to 5:1. The carbonate-type polyurethane containing pendent carboxylic grop(PU) had Tg of around-$25^{\circ}C$ and Tm, $45^{\circ}C$ measured by DSC. Transition temperatures of one containing pendent anionic group(APU) prepared from the ionization of PU shifted to $8{\sim}10^{\circ}C$ lower temperature region than those of PU. Pervaporation membrane was prepared through the casting method. N, N-dimethylformamide (DMF) were used as a solvent and hexamethylene diisocyanate(HMDl) as a crosslinking agent. Swelling degree increased with ethanol concentration in mixure and the control of the swelling degree of the membrane could be achieved by crossliking. The results of pervaporation were as follows : separation factor, 2.3~9.8 ; flux, $27{\sim}79.5g/m^2hr$. Pervaporation separation capacity could be enhanced by reducing the molecular weight of polyol from 2,000 to 1,000.

• Journal of Periodontal and Implant Science
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• v.37 no.3
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• pp.465-478
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• 2007

Various periodontal barrier membranes used in many clinical and experimental fields, and many recent studies of membranes have reported good results. To improve clinical results, selection of barrier membranes is an important factor. So, we need not only to evaluate various barrier mem-branes, but also to understand the property of barrier membranes appropriate to defect characteristics. For this purpose, this study reviewed available literature, evaluated comparable experimental models, and compared various barrier membranes. From above mentioned methods, the following conclusions are deduced. 1. In i-wall periodontal defect models, new bone formation showed a consistent result, almost 30% of the defect size. New cementum formations measured mostly 40% of the defect size, but showed more variations than new bone formations. This seems to be resulted form difference in experimental methods, so standardization in experimental methods is needed for future studies. 2. Application PLGA barrier membrane to periodontal defect demonstrated improved healing in new bone and new cementum. 3. There was a minimal periodontal regeneration with calcium sulfate barrier membrane only. But, there was better healing pattern in combination of calcium sulfate membrane with bone graft material, such as DFDBA, 4. There was no significant difference between the experimental group that used chitosan mem-brane only and the control group. But, in combination with bone graft material for space maintanence, periodontal regeneration was improved. Overall, Space maintenance is a critical factor for Guided tissue regeneration using barrier membranes. Also, a barrier membrane itself that has difficulty in maintaining space, achieved better result when used with graft material.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.6
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• pp.510-522
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• 2005

To assess the clinical applicability of bio-artificial mucosa which was made with autologous oral keratinocytes and human acellular dermal matrix, the formation of basement membrane and stratification of oral keratinocytes were evaluated. Six New Zealand white rabbits (around 2kg in weight) were anesthetized and its buccal mucosa was harvested (1.0 $\times$ 0.5cm size). Oral keratinicytes were extracted and cultured primarily with the feeder layer of pretreated NIH J2 3T3 fibroblast. These confluent cells were innoculated on the human acellular dermal matrix and cultured in multiple layer by air-rafting method. After 3, 5, 7, 10, 14 days of culture, each cultured bio-artificial mucosa was investigated the number of epthelial layer of by H&E stain and toluidine blue stain. The immuhohistochemical methods were used to evaluate the cell division capacity, the formation of basement membrane, and it's property of specific cells (PCNA, cytokeratin 14, laminin). Transmission electromicroscopy was used for the attachment between cells and matrix with the number of hemidesmosome. In result, the numbers of layer of stratified growth of oral keratinocyte cultured on the human acellular dermal matrix and the number of hemidesomal attachment between epithelial cells and human acellular dermal matrix were similar to the layers of normal oral mucosa after 10 days of culture. The cell division rate, basement membrane formation and proliferation rate increased as culture period increased. With these results, bio-artificial mucosa with autologous oral epithelial cells cultured on the acellular dermal matrix had clinically adaptable properties after 10 days' culture and this new bio-artificial mucosa model with relatively short culture time can be expected clinical applicability.

• Membrane Journal
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• v.12 no.1
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• pp.41-50
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• 2002

The streaming potential generated by the electrokinetic flow within electric double layer of charged microchannel is applied to determine the zeta potential of hollow-fiber membrane pore by using the general Helmholtz-Smoluchowski equation. The streaming potential is know to provide a useful real-time information on the surface property and the interaction between pore and particles in actual situations and physicochemical conditions. The influence of physicochemical parameters upon the filtration with hollow-fibers has been examined with an in-situ and simultaneously monitoring the streaming potential as well as permeate flux. In particular, the present study examined an experimental method to identify the effect of cake layer which can vary according to the axial position of a hollow-fiber and the progress of membrane fouling by measuring the position-dependent streaming potential. As the latex concentration increases, the permeate flux decreased but the streaming potential increased. The growth of cake layer has been mire developed with increasing latex concentration, however, the effect of surface charges of latexes deposited on the membrane surface leads to increase the streaming potential. With increasing ionic concentration of KCI, both the permeate flux and the streaming potential decrease. The increase of ionic concentration provides a compact cake layer due to the shrinkage of Debye length and the decreased streaming potential results from the weakened ionic flows owing to a thin diffusive double layer.

• Membrane Journal
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• v.22 no.1
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• pp.23-34
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• 2012

In this study, we investigated the permeation property of single gases ($N_2$, $O_2$, $SF_6$, $CF_4$ through hollow fiber polymeric membrane (PSF, PC, PI) as a function of pressure and temperature to decide operating condition for $SF_6$ gas separation process. The results showed the gas permeation varied differentlydepending on the properties of gases and membrane. When permeance of each gases was represented as a function of temperature and pressure in 3 dimensional space, the surface of permeance was shown approximately flat. Thus, we established permeance models with forms of first-and second-order polynomial. These two models showed high goodness of fit. This indicates that the two polynomial models have enough applicability to predict the gas separation process.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.393-402
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• 2021

In this study, a mixed matrix membrane was prepared by putting the zeolitic imidazolate framework-7 (ZIF-7) synthesized in Pebax-1657 and Pebax-2533, which are representative poly(ether-b-amide), and the permeability properties of single gas such as N₂ and CO₂ were investigated. From the gas permeation results, in the case of N₂, both the Pebax-1657/ZIF-7 and Pebax-2533/ZIF-7 mixed matrix membranes showed a similar phenomenon in which the permeability decreased with the incorporation of ZIF-7. For CO₂ permeability, the tendency was slightly different depending on the type of polymer. In the Pebax-1657/ZIF-7 mixed membrane, the CO₂ permeability decreased in the range of 0~3 wt% of ZIF-7, and increased at higher contents. The CO₂ permeability of the Pebax-2533/ZIF-7 mixed matrix membrane gradually decreased without increasing the permeability in the range of 0~5 wt% of ZIF-7. Regarding CO₂/N₂ selectivity, both mixed films showed a tendency to increase with increasing the ZIF-7 content. In particular, Pebax-2533/ZIF-7 5 wt% showed the best gas permeation performance compared to other mixed matrix membrane. This is thought to be because ZIF-7 shows better compatibility with Pebax-2533 than that of Pebax-1657 and also better CO₂ selective property.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.101-101
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• 2018

Quantitative measurement of chloride ion concentration has an important role in various fields of electrochemistry, medical science, biology, metallurgy, architecture, etc. Among them, its importance of architecture is ever-growing due to unexpected degradations of building structure. These situations are caused by corrosion of reinforced concrete (RC) structure of buildings. And chloride ions are the most powerful factors of RC structure corrosion. Therefore, precise inspection of chloride ion concentration must be required to increase the accuracy of durability monitoring. Multi-walled Carbon nanotubes (MWCNTs) have high chemical resistivity, large surface area and superior electrical property. Thus, it is suitable for the channels of electrical signals made by the sensor. Silver nanoparticles were added to giving the sensing property. CuBTC, one of the metal organic frameworks (MOFs), was employed as a material to improve the sensing property because of its hydrophilicity and high surface area to volume ratio. In this study, sensing element was synthesized by various chemical reaction procedures. At first, MWCNTs were functionalized with a mixture of sulfuric acid and nitric acid because of enhancement of solubility in solution and surface activation. And functionalized MWCNTs, silver nanoparticles, and CuBTC were synthesized on PTFE membrane, one by one. Electroless deposition process was performed to deposit the silver nanoparticles. CuBTC was produced by room temperature synthesis. Surface morphology and composition analysis were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), respectively. X-ray photoelectron spectroscopy (XPS) was also performed to confirm the existence of sensing materials. The electrical properties of sensor were measured by semiconductor analyzer. The chloride ion sensing characteristics were confirmed with the variation of the resistance at 1 V.

• Archives of Pharmacal Research
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• v.19 no.4
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• pp.264-268
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• 1996

Panax-ginseng saponin has been known to exert various pharmacological effects on cellular metabolism. This study was performed to determine the effect of ginseng saponin on gap junction channel-mediated intercellular communication, using an established in vitro system of reconstituted gap junction channels. Gap junction channels are a specialized plasma membrane fraction, which are permeable to relatively large water-soluble molecules. The sucrose permeable property of reconstituted gap junction channels was completely inhibited with 0.1 % (w/v) of ginseng saponin. We also compared the effect of ginseng saponin with that of Triton X-100, a nonionic detergent, on the same system. Triton X-100 showed significantly different effect on sucrose-permeability of gap junction channel from that was affected by ginseng saponin. The structures of liposomes containing gap junction channels was significantly destroyed by Triton X-100.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2672-2677
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• 2007

An investigation of low Reynolds number flow in nozzles and diffusers which are widely used in the valveless micropump is presented. Flow characteristics in the nozzle and diffuser are explained in view of viscous effect and flow oscillation induced by pumping membrane. These calculation results show that the rectification property of valveless micropump is due to a flow separation in the diffuser and the separation is largely originated from the flow oscillation. Under the assumptions of steady flow velocity profile and flow separation in the diffuser, simplified analytical models are provided to see the dependency of rectification on the micropump geometry. Geometric parameters of channel length, nozzle throat, chamber size, and converging/diverging angle are depicted through the analytical models in low Reynolds number flow, and the prediction and experimental results are compared. This theoretical study can be used to determine the optimum geometry of valveless micropump.