• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.495-495
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• 2003

• 한국가스학회:학술대회논문집
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• 2003.05a
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• pp.224-231
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• 2003

• 한국가스학회:학술대회논문집
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• 2005.05a
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• pp.221-221
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• 2005

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.346-347
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• 2006

New manufacturing processes, such as thermochemical, mechanochemical and chemical vapor condensation processes have been developed to obtain nanostructured WC/Co materials. Nanoscale size WC/Co composite powders of near 100-150nm can be synthesizes by thermochemical and mechanochemical processes using water soluble precursors. Non-agglomerated and nano sized WC powder can be synthesized by the chemical vapor condensation process using metallorganic precursors as starting materials. In this paper, the scientific and technical issues on synthesis and consolidation of nanostructured WC/Co alloys produced by new chemical processes are introduced.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.152-161
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• 2023

Vanadium redox flow batteries (VRFBs) have been considered one of promising power sources for large scale energy storage systems (ESS) because of their excellent cycle performance and good safety. However, VRFBs still have a few challenging issues, such as poor Coulombic efficiency due to vanadium crossover between catholyte and anolyte, although recent efforts have shown promise in electrochemical performance. Herein, the vanadium complexes with various glyme ligands have been examined as active materials to suppress vanadium crossover between catholyte and anolyte, thus improving the Coulombic efficiency of VRFBs. The conventional Nafion membrane has a channel size of ca. 10 Å, whereas vanadium cation species are small compared to the Nafion membrane channel. For this reason, vanadium cations can permeate through the Nafion membrane, resulting in significant vanadium crossover during cycling, although the Nafion membrane is a kind of ion-selective membrane. In this regard, various glyme additives, such as 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), and tetraethylene glycol dimethyl ether (tetraglyme) have been examined as complexing agents for vanadium cations to increase the size of vanadium-ligand complexes in electrolytes. Since the size of vanadium-glyme complexes is proportional to the chain length of glymes, the vanadium permeability of the Nafion membrane decreases with increasing the chain length of glymes. As a result, the vanadium complexes with tetraglyme shows the excellent electrochemical performance of VRFBs, such as stable capacity retention (90.4% after 100 cycles) and high Coulombic efficiency (98.2% over 100 cycles).

• Journal of Ginseng Research
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• v.41 no.4
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• pp.572-577
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• 2017

Background: Panax ginseng Meyer is cultivated because of its medicinal effects on the immune system, blood pressure, and cancer. Major ginsenosides in fresh ginseng are converted to minor ginsenosides by structural changes such as hydrolysis and dehydration. The transformed ginsenosides are generally more bioavailable and bioactive than the primary ginsenosides. Therefore, in this study, hydrothermal processing was applied to ginseng preparation to increase the yields of the transformed ginsenosides, such as 20(S)-Rg3, Rk1, and Rg5, and enhance antioxidant activities in an effective way. Methods: Ginseng extract was hydrothermally processed using batch reactors at $100-160^{\circ}C$ with differing reaction times. Quantitative analysis of the ginsenoside yields was performed using HPLC, and the antioxidant activity was qualitatively analyzed by evaluating 2,2'-azino-bis radical cation scavenging, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, and phenolic antioxidants. Red ginseng and sun ginseng were prepared by conventional steaming as the control group. Results: Unlike steaming, the hydrothermal process was performed under homogeneous conditions. Chemical reaction, heat transfer, and mass transfer are generally more efficient in homogeneous reactions. Therefore, maximum yields for the hydrothermal process were 2.5-25 times higher than those for steaming, and the antioxidant activities showed 1.6-4-fold increases for the hydrothermal process. Moreover, the reaction time was decreased from 3 h to 15-35 min using hydrothermal processing. Conclusion: Therefore, hydrothermal processing offers significant improvements over the conventional steaming process. In particular, at temperatures over $140^{\circ}C$, high yields of the transformed ginsenosides and increased antioxidant activities were obtained in tens of minutes.

• Clean Technology
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• v.18 no.4
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• pp.341-346
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• 2012

Many researchers have studied that many processes to effectively remove heavy metals in water/wastewater. Especially, among many processes, physical and chemical processes are relatively simple and obtain high treatment efficiency for removal heavy metals compared with biological treatment. Recently, interests in physical and chemical methods are sharply increasing again because of dangerousness for radioactive element. In this study, various physical and chemical processes such as chemical precipitation, ion-exchange, electrodialysis, and membrane separation are introduced.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.75-81
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• 2001

MCVD(modified chemical vapor deposition) used in making optical-fiber currently utilizes the hydrogen-oxygen burner as a energy supply source. To improve the productivity and to reduce the manufacturing cost of optical-fiber, a natural gas-oxygen burner has been developed. The manufacturing processes of optical-fiber consist of vapor deposition, collapse and drawing processes. Among these processes, the vapor deposition and the collapse processes are important in terms of improving the productivity and saving the production cost. The vapor deposition and collapse processes are performed by combustion heat and flame force supplied by a burner. So the flame force of the burner used in these processes is required to have an optimal and consistent value in order to allow uniform heating and collapse of quartz tube. In this regard, the momentum ratio of natural gas and oxygen has been optimally determined by modification of a burner and the inlet flow pass also has been modified.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1603-1607
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• 2012

The effects of plating process on the surface coverage of the accelerator were investigated in terms of Cu superfilling for device metallization. When a substrate having 500 nm-wide trench patterns on it was immersed in an electrolyte containing poly (ethylene glycol) (PEG)-chloride ion ($Cl^-$)-bis(3-sulfopropyl) disulfide (SPS) additives without applying deposition potential for such a time of about 100s, voids were generated inside of the electrodeposit. In time-evolved electrochemical analyses, it was observed that the process (immersion without applying potential) in the electrolyte led to the build-up of high initial coverage of SPS-Cl on the surface, resulting in the fast saturation of the coverage. Repeated experiments suggested that the fast saturation of SPS-Cl failed in superfilling while a gradual increase in the SPS-Cl coverage through competition with initially adsorbed PEG-Cl enabled it. Consequently, superfilling was achievable only in the case of applying the plating potential as soon as the substrate is dipped in an electrolyte to prevent rapid accumulation of SPS-Cl on the surface.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3542-3546
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• 2014

Relationship between molecular freedom of amyloidogenic protein and its self-assembly into amyloid fibrils has been evaluated with ${\alpha}$-synuclein, an intrinsically unfolded protein related to Parkinson's disease, by restricting its structural plasticity through an end-to-end disulfide bond formation between two newly introduced cysteine residues on the N- and C-termini. Although the resulting circular form of ${\alpha}$-synuclein exhibited an impaired fibrillation propensity, the restriction did not completely block the protein's interactive core since co-incubation with wild-type ${\alpha}$-synuclein dramatically facilitated the fibrillation by producing distinctive forms of amyloid fibrils. The suppressed fibrillation propensity was instantly restored as the structural restriction was unleashed with ${\beta}$-mercaptoethanol. Conformational flexibility of the accreting amyloidogenic protein to pre-existing seeds has been demonstrated to be critical for fibrillar extension process by exerting structural adjustment to a complementary structure for the assembly.