• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.340-344
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• 2007

Catalytic upgrading of pyrolytic bio-oil produced from Japanes Larch was carried out over MCM-41 catalyst. Oil with enhanced stability was produced by the MCM-41 catalyst due to transform oxygen known as a main cause for the instability of bio-oil into $H_2O$, CO and $CO_2$. In addition, the MCM-41 catalyst produced the larger amount of phenolic compounds in the pyrolytic bio-oil product compared with that in the bio-oil produced without catalyst. Especially, the catalytic activity of Al-MCM-41 for the bio-oil upgrading was higher than that of Si-MCM-41 because Al-MCM-41 has the larger amount of acid sites. Also, the better reforming result was obtained when pyrolytic bio-oil vapor passed through catalytic layer rather than Japanese Larch was mixed with catalyst directly.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.55-62
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• 2010

In addition to the previous study for development of a 1,200 N-class bipropellant rocket engine with concentrated hydrogen peroxide, the effect of characteristic length and thrust measurement were experimentally evaluated. Tests with characteristic lengths of 0.95, 1.07, and 1.20 m were performed and $C^*$ and Isp efficiencies were increased as increasing characteristic length. The maximum $C^*$ and Isp efficiencies were 98.4% and 93.1% respectively. Based on the evaluation of the designed engine, the optimized characteristic length was proposed in using the engine adapted decomposed hydrogen peroxide and the engine performance at vacuum-level was evaluated using thrust and Isp efficiency at the designed equivalence ratio. As a result, 218.4 s at sea-level, 253.3 s at vacuum-level, and vacuum thrust of 1035.3 N can be estimated.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.11-18
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• 2014

The combustion flowfield at the near-injector region of a 50 N scale $N_2O/C_2H_5OH$ thruster was visualized using shadowgraph technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.1-8
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• 2011

In addition to the previous study for development of a 1,200 N-class bipropellant rocket engine with concentrated hydrogen peroxide, the effect of characteristic length and thrust measurement were experimentally evaluated. Tests with characteristic lengths of 0.95, 1.07, and 1.20 m were performed and $C^*$ and Isp efficiencies were increased as increasing characteristic length. The maximum $C^*$ and Isp efficiencies were 98.4% and 93.1% respectively. Based on the evaluation of the designed engine, the optimized characteristic length was proposed in using the engine adapted decomposed hydrogen peroxide and the engine performance at vacuum-level was evaluated using thrust and Isp efficiency at the designed equivalence ratio. As a result, 218.4 s at sea-level, 253.3 s at vacuum-level, and vacuum thrust of 1035.3 N can be estimated.

• IMMUNE NETWORK
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• v.22 no.6
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• pp.49.1-49.15
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• 2022

Exosomes derived from mesenchymal stem cells (MSCs) could protect against myocardial infarction (MI). TLR4 is reported to play an important role in MI, while microRNA-182-5p (miR-182-5p) negatively regulates TLR4 expression. Therefore, we hypothesize that MSCs-derived exosomes overexpressing miR-182-5p may have beneficial effects on MI. We generated bone marrow mesenchymal stem cells (BM-MSCs) and overexpressed miR-182-5p in these cells for exosome isolation. H₂O₂-stimulated neonatal mouse ventricle myocytes (NMVMs) and MI mouse model were employed, which were subjected to exosome treatment. The expression of inflammatory factors, heart function, and TLR4 signaling pathway activation were monitored. It was found that miR-182-5p decreased TLR4 expression in BM-MSCs and NMVMs. Administration of exosomes overexpressing miR-182-5p to H₂O₂-stimulated NMVMs enhanced cell viability and suppressed the expression of inflammatory cytokines. In addition, they promoted heart function, suppressed inflammatory responses, and de-activated TLR4/NF-κB signaling pathway in MI mice. In conclusion, miR-182-5p transferred by the exosomes derived from BM-MSCs protected against MI-induced impairments by targeting TLR4.

• Tribology and Lubricants
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• v.1 no.1
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• pp.80-87
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• 1985

Lithium dual complex grease was prepared through the second continuous saponification reaction of a complex gellant system whose essential components comprised of a selected hydroxy fatty acid, lithium hydroxide monohydrate and boric acid to have a fiber structure of chemical, thermal and mechanical stability at high temperatures. An optimum amount of complex gellant was found to be 14% (NLGI #2), and an addition of castor wax of 1.5% provided an excellent performance properties, especially. The oil separation, oxidation stability, water wash-out property, shear stability, extreme pressure and wear property of thus prepared were tested by the ASTM and KS methods, and a characteristic result was obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.313-317
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• 2003

The study is the results of accelerated tests and the specimens, mortars, are submerged in a 5% sulfuric acid solution. The deterioration of specimens is followed up by investigating the change in weight and compressive strength of the specimens and techniques such as XRD and XRF are used to examine the chemical changes. Sulfuric acid is a very aggressive acid that reacts with the free lime [$Ca(OH)_2$] in the concrete forming gypsum($CaSO_{4}.2H_{2}O$). This reaction is associated with an increase in volume of the concrete, and the corroded surface becomes soft and white. The results showed that the OPC mortar caused an decrease in weight above 18% and strength loss about 57%. On the other hand, AASC(alkali-activated slag composites) did not cause any decrease in weight and in the case of strength caused an decrease below 10%. In addition, this mechanical results was verified to XRD and XRF.

• Ecology and Resilient Infrastructure
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• v.7 no.2
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• pp.134-144
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• 2020

In-situ stabilization is a remediation method using amendments to reduce contaminant availability in contaminated soil. We tested the effects of two amendments (furnace slag and red mud) on the availability of toxic trace elements (TTEs) and soil enzyme activities (dehydrogenase, phosphatase, and urease). The application of amendments significantly decreased the availability of TTEs in soil (p < 0.05). The decreased availability of TTE content in soils was accompanied by increased soil enzyme activities. We found significant negative relationships between the TTE content assessed using Ca(NO₃)_2^-, TCLP, and PBET extraction methods and soil enzyme activities (p < 0.01). Soil enzyme activities responded sensitively to changes in the soil environment (pH, EC, and availability of TTEs). It could be concluded that soil enzyme activities could be used as bioindicators or ecological indicators for soil quality and health in environmental soil monitoring owing to their high sensitivity to changes in soil.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.55-58
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• 1999

Nafion supported catalytic membranes were found to be active, stable and selective in th partial oxidation of propane to oxygenates with H2O2 under mild condition. Addition of Fe2+ in liquid phase enhances the reaction rate. Reaction proceeds according to a radical mechanism based on th electrophilic activation of propane on superacid sites and subsequent reaction of the activated paraffin with OH radicals. The use of a catalytic membrane, which allow separation of the intermediate products from the liquid phase containing the oxidant, was found to be effective to perform selective partial oxidation of propane with high yields to oxygenated products.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.354-357
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• 2007

The nitriding and post-sintering behavior of silicon powder compact containing sintering additives of 2.3 wt% and 7 wt% were investigated in this study. Regardless of the liquid phase content, elongated large grains of a typical morphology evolved in the post-sintered specimens. Phase analysis revealed a complete phase transformation into ${\beta}-Si_3N_4$ in both porous systems. Oxynitride second phases (mellilite) precipitated in the latter, while those were free in the former containing less amount of liquid phase. The post-sintering condition that yielded a favorable microstructure for a filter application was achieved when the specimens were soaked at $1800^{\circ}C$ for 2 h. It was found that the thermal conductivity of porous $Si_3N_4$ ceramics is dominated by the porosity more than this factor is influenced by the addition of $Al_2O_3$.