• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.45-50
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• 2010

Thermal analyses have been performed to study the effect of location of fuel ring and thermal barrier coatings in regenerative cooling channels in a full-scale combustor. For the effective cooling, the fuel ring has better be installed near axial location of the low expansion ratio and low heat flux, and branching of cooling channels is preferable. Also, the radiative cooled nozzle extension is thought to be reasonable for the cooling of combustor walls. Among the possible coatings, $Y_2O_3$ stabilized $ZrO_2$ coating and Ni/Cr coating have been adopted. Compared with Ni/Cr coating which has high oxidation resistance, $Y_2O_3$ stabilized $ZrO_2$ coating, one of ceramic coatings is found to be much effective to sustain the thermal survivability of combustion walls.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.145-149
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• 2010

Thermal analyses have been performed to study the effect of location of fuel ring and thermal barrier coatings in regenerative cooling channels in a full-scale combustor. For the effective cooling, the fuel ring has better be installed near axial location of the low expansion ratio and low heat flux, and branching of cooling channels is preferable. Also, the radiative cooled nozzle extension is thought to be reasonable for the cooling of combustion walls. Among the possible coatings, $Y_2O_3$ stabilized $ZrO_2$ coating and Ni/Cr coating have been adopted. Compared with Ni/Cr coating which has high oxidation resistance, $Y_2O_3$ stabilized $ZrO_2$ coating, one of ceramic coatings is found to be much effective to sustain the thermal survivability of combustion walls.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.9-19
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• 2002

By using the thermionic emission model, the L-I-V(power-current-voltage) characteristics of a SCH(seperate confinement heterostructure) QW(quantum well) laser diode is analytically derived. We derived the relationships between the bulk carrier density of SCH regions and the confined carrier density of QW. The L-I-V characteristics is derived analytically by using current continuity equations. Solving the ambipolar diffusion equation under the condition of high level injection and charge neutrality, the current distribution in the SCH regions is considered. Results showed that the major factor affecting the laser I-V characteristics was the change of potential barrier at the cladding-SCH interface. Also the series resistance of a laser diode was decreased and the carrier injection was increased by increasing the forward flux of injection current from cladding to SCH region.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.3
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• pp.91-102
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• 2016

The spatio-temporal variations of the dissolved methane concentration were investigated and the methane budget was estimated in the Nakdong Estuary in January, September, and November of 2014. Dissolved methane showed seasonal variation (21~874 nM) with high concentration in summer due to enhanced temperature and fresh water discharge. Decreasing trends of dissolved methane from the river to the estuary were consistent in all seasons showing the main source of the estuarine methane is river discharge. However, the decreasing trends were modified seasonally due to the local sources such as organic-rich sediments in intertidal zone or near the estuarine barrage. Dissolved methane concentration in the Nakdong Estuary was high, compared to other estuaries probably due to the well developed wetland in Nakdong-river system and stagnation effect from barrages and dams. Dominant sink for the Nakdong estuarine methane was outflux into the atmosphere. Relatively long residence time (produced by barrier island and estuarine dam) in the estuary might provide the enough time for the outgassing.

• Journal of Pharmaceutical Investigation
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• v.36 no.6
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• pp.393-399
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• 2006

This study was aimed to design, formulate and characterize the moisture-activated patches containing acyclovir for antiviral action. Gel intermediates for film-type patches were prepared with mucoadhesive polymer, viscosity builders, enhancers and acyclovir. Patches containing acyclovir were characterized by in vitro measurement of drug release rates through a cellulose barrier membrane, and of drug flux through the hairless mouse skin. Film-type patches obtained were uniform in the thickness and showed a mucoadhesive property when contacted with moisture. The formulation was optimized, which consisted of $Cantrez^{\circledR}$ AN-169(2%), $Kollidon^{\circledR}$ VA 64(1%), $Natrosol^{\circledR}$(1%), hydroxypropyl-$\beta$-cyclodextrin(1%) and dimethylsulfoxide(0.5%). Release rates of acyclovir patches increased dose-dependently. The addition of terpenes such as d-limonene or cineole increased release rates of acyclovir, but decreased permeation rates. The permeation rates were enhanced by 2 and 2.5 times by the addition of glycyrrhizic acid ammonium salt and sodium glycocholate, respectively, compared with that of no enhancer. These results suggest that it may be feasible to deliver acyclovir through the skin or gingival mucosa from the moisture-activated patches.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.828-837
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• 2006

Geotextiles consist of three major types of geosynthetic material (woven, non-woven and composite) and the functions of geotextiles are separation, reinforcement, filtration, drainage and as a moisture barrier. Although the many research scholar and engineer developed and established the design criteria and construction methodology, sustainable research still needed for optimum design methodology to the complicate field conditions. In this study, in-situ rainfall test performed to develop suitable filter system for sea dyke upper slope filter layer. In-situ rainfall test conducted for seven different filter system and measured the infiltration flux and pore pressure at various filter layer. Based on the test results, the double layered geotextile filter and sand transition system is most suitable for sea dyke upper filter layer because which system is effective for drainage of infiltration flow and minimize the deformation of sea dyke cover stone.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1874-1881
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• 2002

Heat dissipation technology using the flow resonant phenomenon is a kind of a new concept in the heat transfer area. A vibration exciter is needed to enhance air flow mixing which has the natural shedding frequency of thermal system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator with a displacement estimator using strain gage. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is checked by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, the vibration exciter using strain displacement estimator is developed. During the experimental verification phase, it turns out the high modal resonant characteristics of a vibrating plate are a major barrier against obtaining a high bandwidth vibration exciter.

• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.30-34
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• 2014

Membrane distillation (MD) is a thermal driven separation process in which separation a hydrophobic membrane is a barrier for the liquid phase, letting the vapor phase pass through the membrane pores. Therefore, a porous and hydrophobic membrane should be used in membrane distillation. MD cannot work if water penetrates into the pores of the membrane (membrane wetting). Accordingly, it is necessary to prevent wetting of MD membranes and to remove water inside the pores of the wetted membranes if possible. In this context, our study aimed to develop methods to recover wetted membranes in MD processes. Poly-vinylidene fluoride (PVDF) membranes were used in this study. A laboratory-scale direct contact MD (DCMD) system was used to examine the effect of operating parameters on wetting. For dewetting the wetted membranes, specific techniques including the use of high temperature air were applied. The performances of the membranes before and after dewetting were compared in terms of flux, salt rejection and liquid entry pressure(LEP). The surface morphology of dewetted membrane was confirmed by scanning electron microscope (SEM).

• Ocean and Polar Research
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• v.32 no.3
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• pp.331-336
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• 2010

The CREAMS (Circulation Research of the East Asian Marginal Sea) survey in 1999 revealed a sharp mid-depth discontinuity of the phosphate:silicate ratio in all basins of the East/Japan Sea. Incidentally, this discontinuity layer corresponds to the oxygen minimum layer. Directly below the discontinuity layer, oxygen concentration is increased. This increase in oxygen concentration is interpreted as a proof of intermediate water formation. Oxygen minimum indicates that the water parcel is old and stable against mixing. So it seems be an efficient barrier to vertical exchange of materials. This means that, once materials enter the lower domain, they rarely return to the upper domain. Therefore, the biogeochemistry of the East/Japan Sea depends heavily on material input through the Korea Strait, and flux is expected to be sensitive to the climate change. As a result, the East/Japan Sea ecosystem seems vulnerable to tipping (regime shift), which occurred on a decadal time scale.

• Journal of Magnetics
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• v.10 no.4
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• pp.157-162
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• 2005

We report the magnetic-field dependence of the irreversible magnetization of binary superconductor $MgB_2$. For the temperature region of $T\;<\;0.9T_c$, the contribution of the bulk pinning to the magnetization overwhelms that of the surface pinning. This was evident from the fact that the magnetization curves, M(H), were well described by the critical-state model without considering the reversible magnetization and the surface pinning effect. It was also found that the M(H) curves at various temperatures scaled when the field and the magnetization were normalized by the characteristic caling factors H$\ast$(T) and M$\ast$(T), respectively. This feature suggests that the pinning mechanism determining the hysteresis in M(H) is unique below $T\;=\;T_c$.