• Polymer(Korea)
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• v.32 no.3
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• pp.199-205
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• 2008

In this study, we fabricated poly (lactide-co-glycolide) (PLGA) scaffold modified with small intestinal submucosa (SIS) as a drug delivery matrix of bioactive molecules. SIS derived from the submucosa layer of porcine intestine has been widely used as biomaterial because of low immune response. PLGA scaffold was prepared by the method of solvent casting/salt leaching. Novel composite scaffolds of SIS/PLGA were manufactured by simple immersion method of PLGA scaffold in SIS solution under vacuum. SEM observation shows that PLGA and SIS/PLGA scaffolds have interconnective and open pores. Especially, SIS/PLGA scaffold showed that micro-sponge of SIS with interconnected pore structures were formed in the pores of PLGA scaffold. In order to assay release profile of proteins, we manufactured FITC conjugated BSA loaded PLGA and SIS/PLGA scaffold. And the release amount was identified by fluorescence intensity using the fluorescence spectrophotometer. The initial burst of BSA containing SIS/PLGA scaffolds was lower than that of PLGA scaffolds resulting in constant release. And release of BSA in SIS/PLGA scaffold was fast and incremental because of the increased content of BSA. In conclusion, we confirmed that penetrated SIS solution prevented the initial burst of BSA and PLGA modified with SIS scaffold is useful as protein carriers with controlled release pattern.

• Membrane Journal
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• v.15 no.4
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• pp.272-280
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• 2005

In this study, asymmetric polysulfone membranes were prepared by the phase inversion method and the casting solutions were containing N-methyl-2-pyrrolidone (NMP) as a solvent. Deionized water and various alcohols(methanol, ethanol, and propanol) were used as a coagulation medium in preparing asymmetric polysulfone membranes. This study investigates the effect of alcohol coagulants having different solubility parameters as a pore-former on the construction of porous structures and their pure water permeation properties. Asymmetric polysulfone membranes immersed in the pure alcohol coagulation bath solution showed the typical sponge-like structures and the reduced water permeability as compared with those of polysulfone membranes precipitated in the pure water coagulation bath solution. In the water/alcohol mixtures, asymmetric polysulfone membranes showed the finger-like structures with the sponge-like structures. Therefore, the sponge-like structure of polysulfone membrane was formed under the delayed demixing systems while the porosity of membrane was decreased significantly. The water permeability of polysulfone membrane precipitated in the pure water coagulant showed 164 [$L/m^2hr$] at 14.7 psi. In case of polysulfone membranes prepared in the pure methanol and ethanol coagulant, they showed the water permeability of 56 and 30 [$L/m^2hr$], respectively.

• Membrane Journal
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• v.16 no.1
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• pp.39-50
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• 2006

Porous chitosan and chitin membranes were prepared by using silica particles as porogen. Membrane preparation was achieved via the following three steps: (1) chitosan film formation by casting an chitosan solution containing silica particles, (2) preparation of porous chitosan membrane by dissolving the silica particles by immersing the film into an alkaline solution and (3) preparation of porous chitin membrane by acetylation of chitosan membrane with acetic anhydride. The optimum preparation conditions which could provide a chitosan and chitin membranes with good mechanical strength and adequate pure water flux were determined. To allow protein affinity, a reactive dye (Cibacron Blue 3GA) was immobilized on porous chitosan membrane. Binding capacities of affinity chitosan and chitin membranes for protein and enzyme were determined by the batch adsorption experiments of BSA protein and lysozyme enzyme. The maximum binding capacity of affinity chitosan membrane for BSA protein is about 22 mg/mL, and that of affinity chitin membrane for lysozyme enzyme is about 26 mg/mL. Those binding capacities are about $several{\sim}several$ tens times larger than those of chitosan and chitin-based hydrogel beads. Those results suggest that the porous chitosan and chitin membranes are suitable in affinity filtration chromatography for large scale separation of proteins.

• Membrane Journal
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• v.21 no.4
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• pp.389-397
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• 2011

In this study, polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) were prepared using a solution casting method with different amount of vermiculite (VMT) content. The dispersion of VMT particles in the SPAES matrix was confirmed by means of a scanning electron microscopy observation. The composite membrane containing less than 1 wt% of VMT has a smooth skin on the top and bottom, which means there is a good dispersion of VMT in the matrix. The water uptake of the composite membranes gradually increases as the temperature increases, and the results confirm that all the adsorbed water is bound water because VMT has a strong water affinity on account of its high cation exchange value. A composite membrane with a VMT content of less than 1 wt% increases the proton conductivity and reduces the methanol permeability. Of all the composite membranes, the membrane SPAES/VMT 1.0 has the best fuel cell performance in terms of membrane selectivity. The performance value of SPAES/VMT 1.0 is double that of Nafion 112, which suggests that SPAES/VMT1.0 could be an excellent candidate for direct methanol fuel cells.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.519-526
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• 2001

The effects of methyl isobutyl ketone(MIBK)/ethanol(EtOH) solvent mixtures on the dispension, particle size distribution and rheology of $Al_2$O$_3$/ZrO$_2$ nonaqueous suspensions were investigated by measuring sedimentation density and viscosity. The sedimentation density of $Al_2$O$_3$ and ZrO$_2$ particles increased in MIBK-rich($\geq$60 vol%) solvents with 'Hypermer' KD-1 as a dispersant. The ball-milled suspensions in 80MIBK/20EtOH(vol%) solvent exhibited the narrow and unimodal particle size distribution. Although all Suspensions exhibited the Pseduo-Plastic flow(Shear thinning) the shear thinning behavior was somewhat different depending on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ and MIBK/EtOH. Under a given shear rate( <300 s$^{-1}$ for $Al_2$O$_3$; <3000 s$^{-1}$ for ZrO$_2$) the strongest shear thinning appeared in the $Al_2$O$_3$ and ZrO$_2$ suspensions with pure MIBK solvent. The shear thinning was nearly independable on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ in case of using the identical solvent(80MIBK/20EtOH, vol%).

• Journal of Hydrogen and New Energy
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• v.11 no.4
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• pp.161-169
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• 2000

In the case of photocatalytic hydrogen production from water, the performance-property relationships of CdS-TiO2 film type composite catalysts were investigated. To control the physical properties of the primary particles, the mixture of CdS and TiO2 nano-sols prepared by the sol-gel method at room temperature was hydrothermally treated at 240oC for 12hr. The film electrodes were prepared by the casting method. The photocurrents measured by a photoelectrochemical method and the hydrogen production rates measured by a photochemical method were closely dependent on the physical properties such as crystalline form, primary particle size and CdS/TiO2 mole ratio, and these varied in the range of 1.2~2.6 mA/cm2 and $1.0{\sim}1.6{\times}10-3mol/hr$, respectively.

• Journal of Korea Game Society
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• v.7 no.4
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• pp.71-80
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• 2007

In this paper, we introduce an efficient GPU-based real-time rendering technique applicable to every kind of game. Our method, without an extra geometry, can represent terrain just with a height map. It makes it possible to freely go around in the air or on the surface, so we can directly apply it to any computer games as well as a virtual reality. Since our method is not based on any geometrical structure, it doesn't need special LOD policy and the precision of geometrical representation and visual quality absolutely depend on the resolution of height map and color map. Moreover, GPU-only technique allows the general CPU to be dedicated to more general work, and as a result, enhances the overall performance of the computer. To date, there have been many researches related to the terrain representation, but most of them rely on CPU or confmed its applications to flight simulation, Improving existing displacement mapping techniques and applying it to our terrain rendering, we completely ruled out the problems, such as cracking, poping etc, which cause in polygon-based techniques, The most important contributions are to efficiently deal with arbitrary LOS(Line Of Sight) and dramatically improve visual quality during walk-through by reconstructing a height field with curved patches. We suggest a simple and useful method for calculating ray-patch intersections. We implemented all these on GPU 100%, and got tens to hundreds of framerates with height maps a variety of resolutions$(256{\times}256\;to\;4096{\times}4096)$.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.871-877
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• 2002

Alumina slurriers, having various amount of alumina and ratio of organic additives, were prepared for tape casting. The relative viscosities were compared to investigate influence of composition on stability of the slurry and plotted as a function of powder fraction. They raised with increasing powder fraction of slurries, revealing a exponential function curve, which means that stability of slurry was not affected by amount and composition of organic additives. Cast green tapes were tested under tensile condition at room temperature. The increase in alumina ratio and binder ratio was found to decrease strain to failure of green tapes from 363% to 45% and from 68% to 25%, respectively. Tensile strength of green tapes increased abruptly with increasing alumina ratio, which showed its maximum at 1 MPa. On other hand, Tensile strength increased continuously from 0.5 MPa to 4 MPa with increasing binder ratio. Mechanical properties of them were affected seriously and lost their properties by elevating temperature from 20$^{\circ}C$ to 80$^{\circ}C$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.67-76
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• 2013

In this study, the inhibitive effect of electrochemical treatment subjected to fresh and hardened concrete and literature reviews in terms of the treatment were performed. In hardened concrete, chloride ions are mixed during casting to destroy the passivity of steel, and then the current was provided for 2 weeks with 250, 500 and $750mA/m^2$. After completion of electrochemical treatment, the extraction of chloride ions was quantified and repassivation of steel was observed. Simultaneously, the equated levels of current density for 2 weeks were applied to fresh concrete. Steel-concrete interface in concrete was observed by BSE image analysis and the concrete properties in terms of the diffusivity of chloride ions and the resistance of steel corrosion was measured. As the result, electrochemical treatment is very effectiveness to rehabilitate the passive film on the steel surface and 63-73% of chloride ions in concrete were extracted by the treatment. As the treatment was applied to fresh concrete, the resistance of steel corrosion was improved due to the densification of $Ca(OH)_2$ layers in the vicinity of steel. However, an increase in the current density resulted in an increase in surface chloride content of concrete.

• Journal of Conservation Science
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• v.28 no.4
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• pp.367-376
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• 2012

The ironware production technology is a measure to fathom the society's level of development in time. To understand iron-manufacure methods in the past, various investigations on the fine structures and additions of ironware remains and Iron ingot have been conducted in a way of natural science. This study metallurgically reclassifies remains excavated in iron-manufacture remains located in Beokje, Goyang, which are thought to be in time of Goryeo Dynasty, and draws an inference from the element analysis on the iron-manufacture and smelting technology. Iron ingot samples with a cast iron structure are divided into those with a white cast iron structure and those with a grey cast iron rich in P. The P content of grey cast iron appeared to be the result of adding a flux agent like lime, iron ingot and carbon steel iron ingot with a cast iron structure excavated in the area is regarded as pig iron which was made without a refining process. In this study it seems that two methods of making ironware were used in the area; one is the method of making ironware by pouring cast iron to the casting, and the other is the method of making carbon steel through the refinement of pig iron. It appears that highly even steel structure of carbon steel and a small amount of MnS inclusion are very similar with that of the modern steel to which Mn is artificially added. Nevertheless, these data alone cannot be used to determine the source of Mn in the carbon steel of the excavated from the iron-manufacture remains, which raises the need for further studies on the source and the possibility of carbon steel via the iron-manufacture process of cast iron.