• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2051-2053
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• 1998

In spite of nonlinear or step-changing load and line disturbances, the inverter for the UPS must provide the pure sinusoidal output voltage with low THD(Total Harmonics Distortion). This paper proposes an inverter controller for the UPS which has a good dynamic response characteristic and robustness for applying industrial world directly. The inverter output voltage is controlled instantaneously with a double regulation loop by a TMS320C31 Digital Signal Processor so that it has very good dynamic response for nonlinear or step-changing load and line disturbances. To improve the voltage utilization and response characteristics, the Space Vector Modulation(SVM) technique is adapted for the switching method of this system. The characteristics of the proposed control system were verified by simulations and experiments.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.382-390
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• 2007

To check the feasibility of SMART(Steam Methane Advanced Reforming Technology) system, an experimental investigation was performed. A fluidized bed reactor of diameter 0.052m was operated cyclically up to 10th cycle, alternating between reforming and regeneration conditions. FCR-4 catalyst was used as the reforming catalyst and calcined limestone(domestic, from Danyang) was used as the $CO_2$ absorbent. Hydrogen concentration of 98.2% on a dry basis was reached at $650^{\circ}C$ for the first cycle. This value is much higher than $H_2$ concentration of 73.6% in the reformer of conventional SMR (steam methane reforming) condition. The hydrogen concentration decreased because the $CO_2$ capture capacity decreased as the number of cycles increased. However, the average hydrogen concentration at 10th cycle was 82.5% and this value is also higher than that of SMR. Based on these results, we could conclude that the SMART system can replace SMR system to generate pure hydrogen without HTS (high tempeature shift), LTS (low temperature shift) and $CO_2$ separation process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.641-646
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• 2005

To fabricate a single layer white organic light emitting diode (OLED), a novel non-conjugated blue emitting material PPPMA-co-DTPM copolymer was synthesized containing a perylene moiety unit with hole transporting and blue emitting ability and a triazine moiety unit with electron transporting ability. The devices were fabricated using PPPMA-co-DTPM $(PPPMA[70\;wt\%]:DTPM[30\;wt\%])$ copolymer by varying the doping concentrations of each red, green and blue fluorescent dye, by molecular-dispersing into Toluene solvent with spin coating method. In case of ITO/PPPMA-co-DTPM:TPB$(3\;mol\%):C6(0.04\;mol\%):NR(0.015\;mol\%)/Al$ structure, as they were molecular-dispersing into 30 mg/ml Toluene solvent, nearly-pure white light was obtained both (0.325, 0.339) in the CIE coordinates at 18 V and (0.335, 0.345) at 15 V. The turn-on voltage was 3 V, the light-emitting turn-on voltage was 4 V, and the maximum external quantum efficiency was $0.667\%$ at 24.5 V. Also, in case of using 40 mg/ml Toluene solvent, the CIE coordinate was (0.345, 0.342) at 20 V.

• Food Science and Biotechnology
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• v.14 no.1
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• pp.6-10
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• 2005

Optimal extraction conditions such as pressures, temperatures, and modifiers on glycyrrhizin extraction from licorice were investigated using supercritical $CO_2\;(SC-CO_2)$ at 3 mL/min flow rate. Morphology of licorice tissue, after glycyrrhizin extraction, was examined by SEM, and absolute density ($g/cm^3$) measurement and glycyrrhizin content were determined by HPLC. Pure $SC-CO_2$ had no effect on glycyrrhizin extraction, but recovery of glycyrrhizin ($32.66{\pm}0.77%$) was enhanced when water was used as modifier. The highest recovery was $97.22{\pm}2.17%$ when 70% (v/v) aqueous methanol was added to 15% (v/v) $SC-CO_2$ at 50 MPa and $60^{\circ}C$. Under optimal extraction conditions, 30 MPa pressure and $60^{\circ}C$ heating temperature, glycyrrhizin recovery reached maximum ($102.67{\pm}1.13%$) within 60 min. Licorice tissue was severely damaged by excessive swelling, and absolute density of licorice residues was highest when aqueous methanol was used as a modifier.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.432-437
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• 2005

An electric swing adsorption (ESA) process for recovering highly pure $CO_2$ from the mixed gases was tested. In this study, activated carbon fibers were used as an adsorbent. The activated carbon fibers showed fast adsorption rate and the high adsorption capacity for $CO_2$ adsorption under the condition of the ambient pressure. Activated carbon fiber with higher specific surface area was suitable to repeated adsorption-desorption cycle process, showing consistent breakthrough curve. Especially, the regeneration method by vacuum combined with ESA improved the performance of desorption process by an additional 17％ regeneration efficiency compared to a vacuum only method, and showed the high regeneration efficiency at comparatively low 7-8 Wh energy.

• Advances in materials Research
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• v.5 no.2
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• pp.121-130
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• 2016

In an attempt to reach a balance of performances in homo-polypropylene based system, the effects of single and hybrid reinforcements inclusions comprising calcium carbonate nanoparticles (2, 4 and 6 phc) and glass fibers (10 wt.%) on the mechanical and thermal properties were investigated. Different samples were prepared by employing twin-screw extruder and injection molding machine. In morphological studies, the uniform distribution of glass fibers in PP matrix, relative adhesion between glass fibers and polymer, and existence of nanoparticles in polymer matrix were observed. $PP/CaCO_3$ (6 phc) as compared to pure PP and PP/GF had superior tensile and flexural strengths, impact resistance and deformation temperature under load (DTUL). $PP/GF/CaCO_3$ (6 phc) composite displayed comparable tensile and flexural strengths and impact resistance to neat PP, while its tensile and flexural moduli and deformation temperature under load (DTUL) were 436%, 99% and $26^{\circ}C$greater respectively. The maximum impact resistance was observed in $PP/CaCO_3$(6 phc). The highest DTUL was perceived in PP hybrid nanocomposite containing 10 wt.% glass fiber and 4 phc $CaCO_3$ nanoparticle.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.285-291
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• 2011

NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), poly (tetramethylene glycol)(PTMG) and dimethylol propionic acid(DMPA). Subsequently, waterborne polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of silane coupling agents, such as methyltrimethoxysilane(MTMS), glycidoxypropyl trimethoxysilane(GPTMS), methacryloxypropyl trimethoxysilane (MPTMS) and aminopropyl triethoxysilane(APS). The average particle size of the waterborne polyurethane solutions was increased by adding silane coupling agents. Also, the coating films prepared from GPTMS, MPTMS and APS, exhibited better pencil hardness than those from pure waterborne polyurethane. On the other hand, the coating films from MTMS did not show an improved pencil hardness than those from pure waterborne polyurethane.

• Journal of Periodontal and Implant Science
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• v.33 no.4
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• pp.717-728
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• 2003

This study was performed to evaluate the difference of the bone-to-implant contact according to the surface roughness of the implants. Two beagles were used in the experiment. Extraction of the all premolars was performed in the mandible. In 3 months of healing, screw-shaped pure titanium machined surface implants (Implantium(R), Dentium Co. Korea), implants blasted with 45${\mu}m$ $TiO_2$ particles, (Implantium(R), Dentium Co. Korea) and implants blasted with 100${\mu}m$ $TiO_2$ particles (Implantium(R), Dentium Co. Korea) in diameter 3.4mm and length 6mm were installed in the edentulous mandible. Each dog was sacrificed at 4, 12 weeks after placement and then nondecalcified specimens were prepared for histologic analysis. The results of this study were as follows. 1. At 4 , 12 weeks after the surgery, bone-to-implant contact in the surface blasted with $TiO_2$ particles was higher than that in the pure titanium machined surface respectively. 2. Osseointegration in the surface blasted with 45${\mu}m$ $TiO_2$ particles was more increased than that in the surface blasted with 100${\mu}m$ $TiO_2$ particles. 3. Bone-to-implant contact was increased with time independent of surface roughness. 4. Bone formation was in the outfolded area more than inside the threads independent of surface roughness. From the above results, we were able t o find the most bone-to-implant contact in 45${\mu}m$ $TiO_2$ blasted implant.

• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.893-902
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• 2015

Various Lactobacillus reuteri strains were screened for the ability to convert glycerol to 1,3-propanediol (1,3-PDO) in a glycerol-glucose co-fermentation. Only L. reuteri DSM 20016, a well-known probiotic, was able to efficiently carry out this bioconversion. Several process strategies were employed to improve this process. Co²⁺ addition to the fermentation medium, led to a high product titer (46 g/l) of 1,3-PDO and to improved biomass synthesis. L. reuteri DSM 20016 produced also ca. 3 µg/g of cell dry weight of vitamin B₁₂, conferring an economic value to the biomass produced in the process. Incidentally, we found that L. reuteri displays the highest resistance to Co²⁺ ions ever reported for a microorganism. Two waste materials (crude glycerol from biodiesel industry and spruce hydrolysate from paper industry) alone or in combination were used as feedstocks for the production of 1,3-PDO by L. reuteri DSM 20016. Crude glycerol was efficiently converted into 1,3-PDO although with a lower titer than pure glycerol (33.3 vs. 40.7 g/l). Compared with the fermentation carried out with pure substrates, the 1,3-PDO produced was significantly lower (40.7 vs. 24.2 g/l) using cellulosic hydrolysate and crude glycerol, but strong increases of the maximal biomass produced (2.9 vs 4.3 g/l CDW) and of the glucose consumption rate were found. The results of this study lay the foundation for further investigations to exploit the biotechnological potential of L. reuteri DSM 20016 to produce 1,3-PDO and vitamin B₁₂ using industry byproducts.

• Korean Journal of Materials Research
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• v.24 no.8
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• pp.423-428
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• 2014

We synthesized Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell nanowires(NWs) by means of a co-electrospinning method and demonstrated their magnetic properties. To investigate the structural, morphological, chemical, and magnetic properties of the samples, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used, as was a vibrating sample magnetometer. The morphology of the nanostructures obtained after calcination at $500^{\circ}C$ exhibited core/shell NWs consisting of $TiO_2$ in the core region and ${\alpha}-Fe_2O_3$ in the shell region. In addition, the XPS results confirmed the formation of Fe-doped $TiO_2$ by the doping effect of $Fe^{3+}$ ions into the $TiO_2$ lattice, which can affect the ferromagnetic properties in the core region. For comparison, pure ${\alpha}-Fe_2O_3$ NWs were also fabricated using an electrospinning method. With regard to the magnetic properties, the Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell NWs exhibited improved saturation magnetization(Ms) of approximately ~2.96 emu/g, which is approximately 6.1 times larger than that of pure ${\alpha}-Fe_2O_3$ NWs. The performance enhancement can be explained by three main mechanisms: the doping effect of Fe ions into the $TiO_2$ lattice, the size effect of the $Fe_2O3_$ nanoparticles, and the structural effect of the core-shell nanostructures.