• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.470-475
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• 2013

Zr-benzendicarboxylate structure, UiO-66 was prepared in 1-L batch scale by using a unique sonochemical-solvothermal combined synthesis method. The produced UiO-66 showed uniform particles of ca. $0.2{\mu}m$ in size with the BET surface area of $1,375m^2/g$ in high product yield (>95%). The UiO-66 showed 198 and 84 mg/g $CO_2$ adsorption capacity at 273 K and 298 K, respectively, with excellent $CO_2$ selectivity ($CO_2:N_2=32:1$) at ambient conditions. The isosteric heat of $CO_2$ adsorption varied from 33 to 25 kJ/mol as the adsorption progressed. The UiO-66 tested for xylene isomer separation in a liquid-phase batch mode confirmed preferential adsorption of the adsorbent for o-xylene over m-, and p-xylene.

• KSBB Journal
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• v.17 no.1
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• pp.63-67
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• 2002

Silver-alginate and copper-alginate were prepared with Na-alginate extracted from marine brown algae(Sargassum fluitans). The antibacterial effect of Ag-alginate or Cu-alginate against Staphylococcus aureus and Escherichia coli was carried out by measuring optical density of liquid culture at 600 nm. The cell growth of Staphylococcus aureus and Escherichia coli was very active at pH 7, and was inhibited by adding Ag-alginate with more than 0.006 wt.% of silver content. The antibacterial effect of Ag-alginate against S. aureus and E. coli was better than that of Cu-alginate at the same metal concentration. The cell growth of S. aureus was less inhibitory than E. coli at the same concentration of Ag-alginate. The cell growth of S. aureus and E. coli was also influenced by the characteristics of counter ion of silver.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.647-659
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• 2008

Colloids are a heterogeneous system in which particles of a few nanometers to hundreds micrometers in size are finely dispersed in liquid medium, but show homogeneous properties in macroscopic scale. They have attracted much attention not only as model systems of natural atomic and molecular self-assembled structures but also as novel structural materials of practical applications in a wide range of areas. In particular, recent advances in colloidal science have focused on nano-bio materials and devices which are essential for drug discovery and delivery, diagnostics and biomedical applications. In this review, first we introduce nano-bio colloidal systems and surface modification of colloidal particles which creates various functional groups. Then, various methods of fabrication of colloidal particles using holographic lithography, microfluidics and virus templates are discussed in detail. Finally, various applications of colloids in metal inks, three-dimensional photonic crystals and two-dimensional nanopatterns are also reviewed as representative potential applications.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.428-432
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• 2010

A study on the forming characteristics of outer shell structure for thrust chamber nozzle extension has been performed. In order to identify anisotropy of cold rolled sheet metal, three types of tensile specimens according to the direction to the sheet rolling axis were prepared and tested, and Landford's values were obtained using the results and applied to structural analysis. Forming characteristics of the outer shell structure of the nozzle extension are investigated through manufacturing and forming of the full scale outer shell structures, and strain values obtained by the forming processes are compared to the numerical analysis results. The results obtained by this study will be utilized to design forming tools and processes for manufacturing other outer shell structures which have a bigger expansion area ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.864-870
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• 2017

The propellants are burned in the pre-burner of the staged combustion cycle engine, and the resulting hot gas drives the turbine, and the turbine operates the turbo pump. The burned gas passing through the turbo pump is supplied to the combustor at high temperature and high pressure, where the gas is supplied in an excess of fuel or an excess of oxidant depending on the amount of fuel or oxidant. When the cycle works at oxidizer-rich staged combustion, its metal pipe can ignite or explode by the impact of even small particles. In this study, we develop the powder combinations for anti-oxidation coating through the analysis of other coating materials and establish the coating process.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.672-681
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• 2009

The aim of this study was to evaluate the antioxidant activities of enzymatic digests from citrus by-products (CBPs) prepared by high speed drying (HSD). HSD needs a short time (60 min) for drying and can be used in a commercial scale. Enzymatic digests were prepared from the CBPs using 6 enzymes such as aminoglucosidase (AMG), celluclast, pectinex, termamyl, ultraflo, and viscozyme. Antioxidant activities of AMG digest from CBPs were evaluated by different in vitro models such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, alkyl, $H_2O_2$ scavenging, metal chelating, lipid peroxidation, and comet assays, and exhibited strong activities. The antioxidant compounds were detected by an high performance liquid chromatography (HPLC) coupled on-line to an 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid ($ABTS^+$) scavenging detection system, and found that hesperidin was the key compound. Therefore, the results obtained in this study suggest that HSD is an effective method to transform wet CBPs into dried form, and CBPs are potential source of natural antioxidant.

• Korean Journal of Microbiology
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• v.33 no.2
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• pp.125-130
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• 1997

Microbial reduction of hexava1ent(VI) to trivalent(lII) chromium is regarded as one of the mechanisms that confers resistance to bacteria. In order to verify this hypothesis, we compared Cr(VI) resistance with Cr(VI) reduction among 20 phenotypically distinct environmental isolates from Cr-contaminated and uncontaminated soils. With glucose as an electron donor, Cr(VI) reduction by washed cell suspensions ranged from 0.014 to 0.305 mM Cr(VI) reduced $h^1$. Cr(VI) resistance of the isolates were measured by growth inhibitions on a liquid medium containing 2 mM Cr(VI) based on their decrease of $A_{630}1$ as compared to the controls without Cr(VI). The isolates had a broad range of resistance from no inhibition to 93.4% inhibition of their growth. Upon correlation analysis, there was no significant relationship between those two phenomena. At a population level, a comparison of % resistant viable counts among the Cr-contaminated and uncontaminated soils showed 19.1 % and 0.4% of their total viable counts, respectively. The difference of % resistance between two site,. strongly suggested that the Cr(VI) present in the soils influences natural selection for resistant phenotypes. However, it is unlikely that the Cr(VI) resistance is dependent solely on the reduction as judged by the correlation analysis.

• Resources Recycling
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• v.21 no.6
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• pp.32-38
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• 2012

In this study, direct reduction of $ZrO_2$ using liquid calcium was investigated. The influence of molar ratio of Ca and $ZrO_2$, reaction time and temperature on the reduction behavior of $ZrO_2$ was studied. Experiments were conducted in a closed stainless steel chamber under Ar atmosphere during 5 to 60 minutes. Most of the $ZrO_2$ was reduced to Zr in 5 minutes at 1223 K and 3 Ca/$ZrO_2$ molar ratio. The minimum oxygen content in reduced metal Zr was obtained about 0.66 wt% at 1373 K after 30 minutes and 4 Ca/$ZrO_2$ molar ratio. The morphology of zirconium powder obtained was highly affected by the reaction temperature and reaction time.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.32-39
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• 2005

Leaching behavior of nickel contained in waste Multi-Layer Ceramic Capacitor (MLCC) was investigated using a batch reactor. The effects of acid type, acid concentration, leaching temperature, particle size, and reaction time on the extraction of nickel metal from waste MLCC were examined. As a result, 97% of nickel contained in waste MLCC was leached out in 30 min at the temperature of $90^{\circ}C$ under the condition of $HNO_3$ concentration 1N, solid/liquid ratio 5 g/L and particle size $-300/+180{\mu}m$. It was also found that a Jander equation was useful to fit well the leaching rate data. The rate of nickel leaching is controlled by pore diffusion in $BaTiO_3$ layer and has an activation energy of 37.6 kJ/mol (9.0 kcal/mol).

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.124-125
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• 2007

The composites were fabricated $\beta$-SiC and $TiB_2$ powders with the liquid forming additives of 8, 12, 16[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressureless annealing at $1,650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-$TiB_2$ electroconductive ceramic composites. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[MPa], 54.60 [GPa] and 2.84[GPa] for SiC-$TiB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature. The relative density of SiC-$TiB_2$ composites was lowered due to gaseous products of the result of reaction between SiC and $Al_2O_3+Y_2O_3$. The electrical resistivity showed the lowest value of 0.012[${\Omega}{\cdot}cm$] for 16[wt%] at 25[$^{\circ}C$]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from 25[$^{\circ}C$] to 700[$^{\circ}C$].