• Journal of Powder Materials
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• v.18 no.4
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• pp.347-358
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• 2011

Two different schemes were adopted to fabricate ordered macroporous structures with face centered cubic lattice of air spheres. Monodisperse polymeric latex suspension, which was synthesized by emulsifier-free emulsion polymerization, was mixed with metal oxide ceramic nanoparticles, followed by evaporation-induced self-assembly of the mixed hetero-colloidal particles. After calcination, inverse opal was generated during burning out the organic nanospheres. Inverse opals made of silica or iron oxide were fabricated according to this procedure. Other approach, which utilizes ceramic precursors instead of nanoparticles was adopted successfully to prepare ordered macroporous structure of titania with skeleton structures as well as lithium niobate inverted structures. Similarly, two different schemes were utilized to obtain disordered macroporous structures with random arrays of macropores. Disordered macroporous structure made of indium tin oxide (ITO) was obtained by fabricating colloidal glass of polystyrene microspheres with low monodispersity and subsequent infiltration of the ITO nanoparticles followed by heat treatment at high temperature for burning out the organic microspheres. Similar random structure of titania was also fabricated by mixing polystyrene building block particles with titania nanoparticles having large particle size followed by the calcinations of the samples.

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.304-310
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• 1999

We have developed a new process for the production of new structure oligosaccharides using the mixed-culture fementation of Lipomyces starkeyi KSM22 and leuconostoc mesenteroides B-512FMCM.L.starkeyi KSM22 produces a novel DXAMase(an enzyme containing both dextranase and amylase activities). It hydrolyzes the soluble starch and dextran. The hydrolyzates were used as acceptors for dextransucrase of L.mesenteroides to synthesize the new oligosaccharides(NOS). In fermentation, as the concentration of sucrose was increased from 9%(w/v) to 15%(w/v), the yields of dextran(sum of dextran I, MW=66kD, and dextran II, MW=21kD) was increased from 12.7% to 42.5%, and NOS was increased from 3.9% to 5.2% of the theoretical, respectively. The NOS of dp(degree of polymerization) 5 and over was increased from 33.1% to 58.3% of the total NOS. The NOS showed heat resistant up to 12$0^{\circ}C$ and was stable at pHs ranged from 2 to 6. The NOS decreased the pH changes in the culture of S. mutans, and also showed inhibitory effects on the growth of S. aureus or S. typhimurium.

• Polymer(Korea)
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• v.25 no.3
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• pp.327-333
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• 2001

Acetylene substituted fluorenes such as 2-ethynylfluorene and 2,7-diethynyl-fluorene were synthesized and thin films were prepared by the vacuum deposition. Curing of these fluorene derivatives could be achieved by heat treatment and UV irradiation. The curing temperature of 2-ethynylfluorene and 2,7-diethynylfluorene were found to be 231 and $198^{\circ}C$, respectively. The cured poly(2-ethynylfluorene) and poly(2,7-diethynylfluorene) started to decompose at 280 and $ 385^{\circ}C$, respectively. Fluorescent characteristics of the cured films were similar to those of monomers, but fluorescent efficiency of the film was decreased about 3 to 10 fold.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1392-1397
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• 2009

This study was aimed at developing a low cost cold storage system for agricultural products. Three kinds of slurries: $K_1$, $K_2$, and $K_3$ slurries were developed using phase change materials (PCMs) such as tetradecane, octadecane, and sodium polyacrylate to maintain the desired temperature ranges. The slurries were manufactured by in-situ polymerization. Tetradecane and octadecane were capsulated in a core with melamine at the surface. The thermodynamic characteristics of the slurries were measured and analyzed. The latent heats of the $K_1$, $K_2$, and $K_3$ slurries at the melting points were 206.41, 186.88, and 147.91 kJ/kg, respectively. A transportable cold storage container was built to investigate the performance of the slurries as thermal storage media. The temperatures at the insides of the container could be maintained in the ranges of 0-5, 5-10, and $10-15^{\circ}C$ for more than 23, 27, and 60 hr with the $K_1$, $K_2$, and $K_3$ slurries, respectively.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.559-567
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• 1989

Bioglasses have been known to be as one of the promising biomateials, which can be used for replacing defective hard and soft tissue. There have been many reports on biological results for this type of glass, but no systematic work has carried out on the structures and properties of the bioglass itself. In the present study, the effect of P2O5 in bioglasses on their structures and properties was examined. Infrared and Raman spectroscopy for the glass structural analysis, differential thermal and X-ray diffraction analysis for the crystallization of the bioglass were performed, and several physical properties were measured. When the glasses were heat-treated, Na2O.2CaO.3SiO2 was the major crystalline phase and $\beta$-NaCaPO4 crystal was found for the glass with high P2O5 content. The added P2O5 in the glasses enhanced the polymerization of silicate glass structure and it changed the chain-like glass structure to a sheet-like structure, and some P2O5 may stay as phosphate monomer. With addition of P2O5 in the glass the density of the glasses decreased, but not much changes in their thermal expansion coefficient, softening point and microhardness were observed.

• The Journal of Korean Physical Therapy
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• v.4 no.1
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• pp.13-18
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• 1992

Most of the electromagnetic agents used in physical therapy rely for their effects on tissue heating and photoreaction of the body. Infrared and untraviolet light on the other hand, owns its place in medicine because it produces direct photochemial reaction when it interacts with the body. This study was carried out to investigate and review for photoreaction of the akin. The results were an follows. 1. The effects of the infrared are heat production, increasing metabolism, increasing circulation, vasodilatation and pigmentation. 2. Directed photoreactions are divided into acute reaction and chronic reaction, and the acute reaction makes pigmentation from $290\~320nm$ of ultraviolet ray. 3. Ultraviolet ray formated pigmentations, which are melanoblasts excited from ultraviolet ray and received chemical stimulation, that make melanin granule. 4. If exposured with long duration, at ultraviolet ray, it makes skin thickening and epithelioma. 5. Indirected photoreaction is made by existenced hypersensitivity of photoreaction or lack of photodefence structure. 6. The phototoxic reactions are synthesized by chemical reaction of excitement from ultraviolet ray also this time analysis, synthesis and polymerization from energy of a circumferenced substance. 7. Sunscreen substances are P-amino benzoic acid and oxidate titan.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.552-557
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• 2015

The nanostereolithography process using a femtosecond laser has been shown to have strong merits for the direct fabrication of 2D/3D micro structures. In addition, a femtosecond laser provides efficient tools for precise micromachining owing to the advantages of a small and feeble heat effect zone. In this paper, we report an effective fabrication process of 3D micro optical and fluidic devices using nanostereolithography process composed of a dual stage system. Process conditions for additive and subtractive fabrication are examined. The Piezo stage scanning system is used for 3D micro-fabrication in unit area of sub-mm scale, and the motor stage is employed in fabrication on the scale of several mm. The misalignment between the pizeo- and motor- stages is revised through rotational transformation of CAD data in the unit domain. Here, the effectiveness of the proposed process is demonstrated through examples using 3D optical and microfluidic structures.

• Carbon letters
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• v.15 no.4
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• pp.262-267
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• 2014

Pyrolized fuel oil (PFO) was reformed by novel electron beam (E-beam) radiation, and the elemental composition, chemical bonds, average molecular weight, solubility, softening point, yields, and density of the modified patches were characterized. These properties of modified pitch were dependent on the reforming method (heat or E-beam radiation treatment) and absorbed dose. Aromaticity ($F_a$), average molecular weight, solubility, softening point, and density increased in proportion to the absorbed dose of E-beam radiation, with the exception of the highest absorbed dose, due to modification by free radical polymerization and the powerful energy intensity of E-beam treatment. The H/C ratio and yield exhibited the opposite trend for the same reason. These results indicate that novel E-beam radiation reforming is suitable for the preparation of aromatic pitch with a high ${\beta}$-resin content.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.537-542
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• 2016

In this study, we have prepared mesophase pitch from pyrolysis fuel oil (PFO) by heterogeneous reforming process. This process was conducted by direct fluorination at various temperature and followed by the heat treatment at $390^{\circ}C$. The reformed pitch was then investigated by softening point analysis, elemental analysis, fourier-transform infrared spectroscopy, high resolution X-ray diffraction and polarization microscope analysis. Carbon contents of reformed pitch increased according to increasing the reaction temperature of fluorination, while oxygen, nitrogen and sulfur contents were completely eliminated. As the fluorination temperature increased, the creation, growth, coalescence and alignment process of mesophase spheres were observed. Also the interlayer spacing of carbon hexagonal planar structure decreased, while its crystalline size increased. In addition, aromatic ring compound contents increased by the condensation polymerization of aliphatic compound. These results can be attributed to the radical reactivity of the fluorine increased as the reaction temperature increased. It was considered that the fluorination reaction could help PFO to generate aromatic compounds, via promoting polymerization by radical reaction.

• Journal of Adhesion and Interface
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• v.19 no.1
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• pp.13-18
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• 2018

At ruthenium (Ru) catalyst was exposed from the atmosphere, the degree of catalyst activation decreased. The change of catalyst activity with the number of days of exposure to air for the Ru catalyst was confirmed using the surface tension method quantitatively. Mechanical properties and surfactant change after polymerization by DCPD using Ru catalyst for each air exposure day was evaluated. The Ru catalyst mixed with a dilution agent was exposed in the air and color was monitored for each day. Surface tension was measured using Wilhelmy and PTFE and associated with different catalyst activities. Heat was measured in real time during polymerizing DCPD with Ru catalyst. After polymerization, tensile strength was measured for p-DCPD and the change of material property was measured. Interfacial properties were also evaluated via microdroplet pull-out tests between glass fiber and p-DCPD. The surface tension was stable until the 4 days (33 dyne/cm) whereas the surface energy increased at the 10 days (34 dyne/cm), which could be correlated with oxidation of the catalyst. Tensile property and interfacial shear strength (IFSS) was also stable until the 4 days (tensile strength: 38 MPa and IFSS: 26 MPa) whereas the mechanical property decrease at 10 days (tensile strength: 15 MPa and IFSS: 3 MPa) dramatically.