• Clean Technology
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• v.18 no.2
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• pp.123-143
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• 2012

Supercritical fluid technology (SFT) is recently one of the most new techniques, which has been interested various fields of related chemical industries. SFT is the most effective and practical technology with eco-friendly, energy-savings, and high efficiency as the technique using the advantages of supercritical fluid such as high solvation power, solubility, mass transfer rate, and diffusion rate. Especially, it is necessary to analyze, evaluate, and develop the potential of application techniques using SFT with these characterizations. Therefore in this review, the phase behavior in supercritical fluid at high temperature and pressure of monomers/polymers for the optimization of polymerization process are briefly described, and the preparation of molecularly imprinted polymers (MIPs) in supercritical fluid using supercritical polymerization and the performance evaluation of MIPs are introduced.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.521-528
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• 1993

Ni-graphi~e composite powders were prepared by reduct ion of $Ni^{++}$ from arnmoniacal nickel sulfate solution on graphite core by hydrogen gas at elevated temperature and pressure. Effect of coating catalyst. Anthraquinone $(C_6H_4COC_6H_4 CO)$, on the reduction rate and the properties of nickel layer were investigated by SEM, X-ray, size and chemical analysis. 1nduct.ion period, a time lag between the ~njection of hydrogen gas and the start of the reduction, was 22 to 70 mins and was affected by the size and amount of Anthraquinone. Kickel layer deposited on the surface of graphite core material was composed of nickel nodules whose sizes were different with vari~ ous reduction conditions. Minimum diameter of nickel nodules was about 2-3$\mu \textrm m$.

• Elastomers and Composites
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• v.34 no.4
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• pp.321-331
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• 1999

The curing process is the final step in tire manufacturing whereby a green tire built from layers of rubber compounds is formed to the desired shape and the compounds are converted to a strong, elastic materials to meet tire performance needs under elevated pressure and temperature in a press. A numerical optimization procedure was developed to improve product quality in a tire curing process. First, a dynamic constrained optimization problem was formulated to determine the optimal condition of the supplied cure media during a curing process. The objective function is subject to an equality constraint representing the process model that describes the heat transfer and cures kinetic phenomena in a cure press and is subject to inequality constraints representing temperature limits imposed on cure media. Then, the optimization problem was solved to determine optimal condition of the supplied cure media for a tire using the complex algorithm along with a finite element model solver.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.7-14
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• 1999

TiZrB2 solid solution was synthesized using fine powders of Ti, Zr and B by SHS microwave process. The characterization of the synthesized powder and sintered bodies ws investigated. The combustion temperature and rate were increased with increasing the mole ratio of Zr in temperature profile, and showed the maximum combustion temperature and velocity values of 285$0^{\circ}C$ and 14.6mm/sec in Ti0.2Zr0.8B2 composition. Phase separation has been occured into a composite with TiB2 and ZrB2 phases from TiZrB2 solid solution, which was hot pressed sintering at 30 MPa for an hour at 190$0^{\circ}C$. At the composition of Ti0.8Zr0.2B2 the best properties has been obtained in relative density, bending strength, fracture toughness and hardness, with 99%, 680 MPa, 7.3MPa.m1/2 and 2750 Kg/$\textrm{mm}^2$ respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.3
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• pp.313-318
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• 1984

Some chemical, biochemical and physical treatments on the baker's yeasts (Saccharomyces cerevisiae) before 12-hour digestion at $50^{\circ}C$ were made to accelerate their autolysis. Dilute alkali treatment with 0.01N-NaOH solution showed a considerable increase in soluble nitrogen extraction only in the 6-hour initial autolysis. The addition of fresh yeast autolysate, 10% to the yeast slurry, could increase the autolysis rate from 65% to 83%. Microwave treatment of yeast slurry for 40 seconds also raised the autolysis rate by about 15%, while longer exposures to the microwave accompanying high temperatures repressed the autolysis process. Extrusion of the yeast cells with high pressures of 16,000 to 20,000 psi brought about significantly higher autolysis rate until the digestion time of 9 hours, but thereafter it showed a gradual drop in soluble nitrogen extraction.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.441-444
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• 2008

Ultra high performance concrete (UHPC) in this study is composed of sand, cement, silica fume, siliceous powder, superplasticizer and steel fiber. UHPC is composed of fine mineral particles below 0.5mm in diameter. In general, siliceous powder improves the mechanical properties of concrete by physical and chemical effect. Physical effect is related with filling interior voids which weaken the mechanical properties and chemical effect with reaction of $SiO_2$ with cement hydrates in a condition of high temperature and pressure. We evaluated the effect of siliceous powder's particle size on the mechanical properties of ultra high performance concrete in air pressure and $90^{\circ}C$ steam curing condition. siliceous powder's particle size in this study is in the range of $2{\mu}m$ to $26{\mu}m$. Fluidity in a fresh concrete, compressive strength, ultimate strain, elastic modulus and flexural strength in a hardened concrete was evaluated. We could find out that the smaller siliceous powder's particle size is, the better the fluidity and strength properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.347-354
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• 2016

Because typical gas turbine systems have frequent startup and shutdown operations, it is likely to cause cracks at the gas turbine casing and gas leakages at casing flanges due to thermal fatigue and embrittlement. Therefore, the evaluation of structural integrity and gas leakage at the gas turbine casings must be performed. In this paper, we have evaluated the structural integrity of the turbine casing and bolts under a normal operation in accordance with ASME B&PVC and evaluated the leakage at casing flanges by examination of contact pressure calculated using the finite element analysis. Finally, we propose a design flow including finite element modeling, the interpretation and evaluation methods for gas turbine casings. This may be utilized in the design and development of gas turbine casings.

• Food Science and Preservation
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• v.20 no.4
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• pp.592-596
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• 2013

To stabilize the basal extraction conditions of Leonuri herbal products, three kinds of Leonurus sibiricus water extracts were prepared with different extraction conditions (boiling extraction (I), high thermal process & boiling extraction (II), and wet grinding & boiling extraction (III)), and their physiological properties were investigated. The extraction yields of the L. sibiricus water extracts were from 13.02 to 15.90%, with no significant difference among them. The polyphenol contents were significantly high in extracts (II) and (III) than in extract (I). The $IC_{50}$ for the electron-donating ability was the smallest in extracts (II), (III) and (I) in ascending order. The ABTS radical scavenging ability was significantly higher in extracts (II) and (III) than in extract (I). Also, the ACE in hibition ability for 5 mg/mL of each extract was high in extracts (II) and (III), but there was no significant difference among the three extracts in terms of their nitrite scavenging abilities. Extraction processes (II) and (III) were shown to be useful for preparing Leonurus sibiricus water extracts with healthful properties.

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.15-19
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• 1997

Single crystals of Co-doped quartz (blue quartz) were grown hydrothermally from the $Na_2CO_3$ solution. The size of as-grown crystal was $100{\times}50{\times}35mm^3$ and the growth rate was 0.55 mm/day under the growth condition of $5wt.\%\;Na_2CO_3$ mineralizer, growth temperature of $343^{\circ}C$ and temperature gradient of $22^{\circ}C$. Visible spectrum showed a typical absorption feature of the synthetic blue quartz near 545, 570 and 643 nm. The concentration of color of the as-grown blue quartz related not to the concentration of cobalt in raw material but to the growth temperature.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.30-35
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• 1996

Calcite(CaCO3) single crystals were grown hydrothermally and transmittance of as grown crystals was measured. Instead of platinium, teflon was lined onto the wall of autoclave to prevent the corrosion of autoclave wall by acidic NH4Cl solution. Spontaneous nucleation and growth of calcite crystal on teflon was reduced considerably by addition of NaCl and /or CH3COOH and applying low temperature gradient. When the temperature gradient exceeded to a few degrees from the critical temperature gradient(6-7℃), spontaneous nucleation and growth was rapidly increased in any hydrothermal solutions. Precise temperature control is thought to be the most important factor for the growth of calcite single crystal by hydrothermal technique. As grown calcite single crytal showed high transmittance compared to natural one by UV-visible analysis.