• Proceedings of the KSR Conference
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• 2004.06a
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• pp.309-314
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• 2004

This study focused on the introduction of damage repair for polymeric composite carbody. called selfing tech-healinique. using microcapsules loaded with the healing agent The manufacturing process for microcapsules with the healing agent was introduced and tile characteristics of microcapsules manufactured by varying with various manufacturing process variables were evaluated. The DCPD was used for the healing agent and microcapsules were made of urea-formaldehyde resin. The magnitude and the size distribution of microcapsules were measured by a particle size analyzer using laser diffraction technique. Thermal stability was investigated by using a TGA under continuous and isothermal heating conditions for the healing agent. microcapsules without the healing agent. microcapsules with the healing agent.

• Journal of the Korean Ceramic Society
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• v.33 no.8
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• pp.935-941
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• 1996

Two-dimensional carbon/carbon preforms made of PAN-based carbon yarn and phenolic resin were densified with pyrolysis of propane by pulse chemical vapor infiltration where repeated the cycle of gas introduction residence and evacuation. Maximim density increment was 14% when infiltration temperature and time were 100$0^{\circ}C$ and 21.25 hrs respectively. The distribution of deposits of pyrocarbon by this process has been occurred uniformly in the bottom middle and top of carbon/carbon composite preform Pulse CVI with residence is most effective in increasing density and shortening infiltration time among isothermal CVI and pulse CVI with and without residence.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.793-796
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• 2003

This study dealt with the manufacturing process of self-healing microcapsules for damage repair in polymeric composites. The microcapsule was consisted with a DCPD (dicyclopentadiene) as the healing agent and a urea-formaldehyde resin as the wall section. The size distribution of microcapsules were measured by a particle size analyzer using a laser diffraction technique. Thermal stability of microcapsules was investigated by using a TGA under continuous and isothermal heating conditions. According to the results, these microcapsules were verified to be to thermally stable and have a great potential to be applicable for damage repair in polymeric composites.

• Journal of the Korean Society of Tobacco Science
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• v.5 no.2
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• pp.55-62
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• 1983

Four of non- isothermal methods evaluating kinetics have been studied by using differential scanning calorimetry (DSC) and thermogravimetry (TG) and applied for kinetics of the thermal decomposition of cellulose. It is concluded that the heating evolution methods with DSC and approximative methods with TC can lead to satisfactory kinetic analysis. Results calculating the reacting order and the activation energy of cellulose decomposition were 1/2 order and 42kcaB/mol, respectively.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1657-1659
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• 1996

The objective of this study is to provide a life prediction of isothermal fatigue using strain partitioning of high temp. steel for power plants. The experimental system was composed of Instron 8501, induction heating system, extensometer and pyrometer with hydraulic power system

• Journal of Welding and Joining
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• v.11 no.1
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• pp.2-8
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• 1993

A literature review was conducted to gather informations available on the welding metallurgy of aluminum alloys, emphasized on characteristics in the heat affected zone(HAZ). Nominal metallurgical reactions that occur in aluminum alloys provide a basis for understanding aluminum welding metallurgy. However, welding reactions differ to some extent because of the relatively short times involved, and the non-isothermal heating excursed. For non-heat treatable alloys, welding primarily affects these alloys by annealing (recrystallization and growth) and to a less extent, changes in low temperature precipitates. In the case of heat treatable alloys, the resulting HAZ properties depend upon alloy composition, starting temper, heat input and post weld heat treatments.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1331-1336
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• 1995

The glass-ceramics for ferro-electric were made from compositions of 70PbO.16TiO2.8SiO2.4B2O3.2AlPO4 (wt%) and 67.5PbO.20TiO2.8.5SiO2.2B2O3.2AlPO4 (wt%). The crystallization kinetics for PbTiO3 crystalline phase formation from glass was studied using non-isothermal DSC techniques. The values of activation energy, ΔE using variables of heating rate and temperature were calculated at various reaction fractions obtained from peak area over DSC. The results indicated that activation energy was lowest at 60% reaction fractions and the activation energy of glass containing 20.0 wt% TiO2 is higher than that of glass containing 16.0 wt% TiO2. The crystallization mechanism was three dimensional growth (n=4).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.640-648
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• 1998

A numerical study has been conducted to investigate the effect of inflow supply air temperature and velocity on ventilation effectiveness in an underfloor air conditioning space. A low Reynolds number k-$\varepsilon$ model is implemented to calculate steady state turbulent velocity distributions. A step-down injection method is used to calculate local and room mean ages from transient concentrations based on the concept of the age of air. Results show that there is a significant effect of Archimedes number on ventilation effectiveness especially for cooling conditions. Reynolds number shows relatively minor effect on velocity distribution and ventilation effectiveness especially for isothermal and heating conditions. It can be concluded that underfloor air conditioning system provides good ventilation characteristics for cooling conditions because of temperature stratification in the space.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.47.1-47.1
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• 2013

Supersonic turbulence is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to investigate the role of global magnetic fields and structures. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in warm neutral medium. Early evolution is consistent with previous studies characterized rapid decay of turbulence with the decaying time shorter than a flow crossing time and power-law temporal decay of turbulent kinetic energy with slope of -1. If initial magnetic fields are strong and perpendicular to the sheet, however long term evolutions of kinetic energy shows that a significant amount of turbulent energy still remains even after ten flow crossing times, and decaying rate is reduced as field strengths increase. We analyse power spectra of remaining turbulence to show that incompressible, in-plane motions dominate.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.2-39.2
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• 2016

The central regions of barred-spiral galaxies contain interesting gaseous structures such as dust lanes located at the leading side of the bar and nuclear rings that are sites of intense star formation. Our previous studies showed how gas structures form under the influence of a non-axisymmetric bar potential and temporal/spatial behavior of the star formation in nuclear rings. However, previous works were limited to 2-dimensional infinitesimally-thin, unmagnetized and isothermal disks. To study effects of cooling/heating, vertical motions of gas structures and magnetic field, we use Mesh-Free magneto-hydrodynamic simulation code GIZMO. We find that temporal variations of the star formation rates in the nuclear ring in the three-dimensional model are overall similar those in the previous two-dimensional results, although the former shows more violent small-scale fluctuations near the early primary peak. We will present our recent results about evolution of gaseous structures and star formation rate compare with results of previous studies.