• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.38.2-38.2
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• 2017

We present the observational study toward the multiple outflows around $LkH{\alpha}$ 234 star formation region. The high-resolution, near-IR spectral mapping using the Immersion Grating Infrared Spectrograph (IGRINS) allowed us to distinguish at least four separate outflows with the molecular hydrogen ($H_2$) and forbidden iron ([Fe II]) emission lines. The outflow associated with the radio continuum source VLA 3B is detected in both H2 and [Fe II] emission, while the outflows driven by MM 1, VLA 2 sources were only detected in $H_2$, indicating the different physical conditions of outflows. We confirm the axis of VLA 3B jet, the position angle of ${\sim}240^{\circ}$. We firstly identified the redshifted, near-IR H2 outflow associated with VLA 2, which is coincident with the previous detections of $H_2O$ masers. From the $H_2$ line ratios, we interpret the gas properties of the shock excited blue- and redshifted components, and UV excited surrounding photodissociation region. We also discuss the origin of the high-velocity (|VLSR| > $150km\;s^{-1}$) $H_2$ emission.

• Journal of Powder Materials
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• v.17 no.5
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• pp.359-364
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• 2010

In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at $400^{\circ}C$ increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive $2^{nd}$ and $3^{rd}$ step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.7-12
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• 2006

The propagation rates ($U_{edge}$) of various premixed edge-flames were measured as a function of global strain rate (${ \sigma}$), mixture strength, and Lewis number (Le). Using a counterflow slot-jet burner with electrical heaters at each end, both advancing (positive $U_{edge}$) and retreating (negative $U_{edge}$) edges can be studied as they propagate along the long dimension of the burner. Preliminary results are presented for single and twin premixed hydrocarbon edge-flames in terms of the effects on $U_{edge}$. A low-${\sigma}$ extinction limit has been discovered for all mixtures tested but further analysis is necessary for full characterization since sufficiently $high-{\sigma}$ leads to an apparent stability limit. Propagation rates clearly show a strong dependence on Le. Future work will focus on completing the premixed hydrocarbon edge-flame analysis and include investigations into non-premixed edge-flames and edge-flames composed of fuels such as hydrogen ($H_2$) with significantly lower Le.

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.145-155
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• 2001

This simulation first allows us to define a transition zone from a bubble to jet mode of the argon out-flow and hereinafter to define a similar area for water-steam leak in the KALIMER SG (Korea Advanced Liquid Metal Reactor Steam Generator) using a water mock-up system, taking into account the KALIMER leak classification and tube bundle design, as a simulation of a real water-steam into sodium leak. in accordance with leak conditions in the KALIMER SG, the transition from bubbling to jetting is studied by means of turbulence regime simulation for argon out-flow through a very small orifice, which has the equivalent diameter of about 0.253 mm. finally the noise generation mechanism is explained from the existing experimental data. We also confirmed the possibility of micro-leak detection from the information of the bubbling mode through simulations and the experiment in this study.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.123-129
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• 1998

A numerical study has been conducted to investigate the effect of shock waves on the mixing and the recirculation zone of a hydrogen jet diffusion flame in a supersonic combustor. The general trends are compared with the experimental results obtained from the supersonic combustor at the University of Michigan. For the numerical simulation of supersonic diffusion flames, multi-species Navier-Stokes equations and detailed chemistry reaction equations of $H_2$-Air are considered. The $K-{\omega}/k-{\varepsilon}$ blended two equation turbulent model is used. Roe's FDS method and MUSCL method are used for convection fluxes in governing equations. Numerical results show that when slender wedges are mounted at the combustor wall the mixing and the combustion are enhanced and the size of recirculation zone is increased . The flame shape of supersonic flames is different in the flame-tip; it is not closed but open. The flame shape is shown to be greatly affected by shock waves.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.243-248
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• 2017

Antioxidants have been added to cryoprotectant or in vitro culture medium for sperm to reduce the detrimental damage, such as reactive oxygen species. However, curcumin, an antioxidant, shows dual effect on the viability and progressive motility of bovine sperm exposed to hydrogen peroxide. Low concentration of curcumin increases sperm viability and progressive motility, whereas high concentration of curcumin reduces them. This study was performed to identify whether TREK-1 channel is related to low sperm viability and motility induced by high concentration of curcumin. Curcumin reduced TREK-1 channel activity in a dose-dependent manner. TREK-1 channel was expressed in sperm obtained from Korean native bull. Treatment with TREK-1 channel blockers, such as curcumin, fluoxetine, $GdCl_3$, and spadin, significantly reduced sperm viability and motility (p < 0.05). However, TREK-1 channel activators showed different effect; linoleic acid showed an increase in sperm viability and motility, and wogonin did not affect them. These results show that TREK-1 channel is involved in the regulation of sperm viability and motility. In particular, high concentration of curcumin might reduce sperm viability and progressive motility of Korean native bull through blockage of TREK-1 channel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.453-456
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• 2011

An experimental investigation of the heat transfer characteristics of stretched premixed flames using Synthetic gas has been performed. Hydrogen and carbon mon-oxide which could be extracted from coal gasification process are the main fuel of synthetic-gas. Heat flux at the stagnation point was increased as global strainrate was increased, then the heat flux was decreased when a global strainrate reached a sudden point. Heat flux at the stagnation point is also affected by nozzle to impingement distance. Heat flux was increased as nozzle to impingement place distance was increased. This study is a foundation study of practical use of secondary gases from coals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.829-836
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• 2013

The combustion characteristics with variations in synthetic natural gas (SNG) compositions were studied in a lab-scale combustor. The objective of the current study is to investigate the flame stabilization, flame structure, and spectrometry in a non-premixed SNG flame with varying fuel compositions. For the analysis of light emission in SNG flames, we used a spectrometer. As experimental conditions, the fuel jet velocity at the nozzle exit $u_F$ was varied from 5 to 40 m/s and the coaxial air velocity $u_A$ was varies from 0 to 0.43 m/s. The experiments showed that the flame stability increased with the hydrogen component in SNG.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.391-403
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• 2013

Propeller aircraft propelled by an electric propulsion system is gaining a renewed interest because of ever-increasing environmental concern on harmful emissions emitted from conventional jet engines and national energy security. Traditional aircraft sizing methods are not readily applicable to electric propulsion aircraft that utilize a variety of alternative energy sources and power generation systems. This study showcases an electric propulsion aircraft sizing exercise based on a generalized, power based sizing method. A general aviation aircraft is propelled by an electric propulsion system that comprises of a propeller, a high temperature super conducting motor, a Proton Exchange Membrance(PEM) fuel cell system fuelled with hydrogen, and power conditioning equipment. In order to assess the impact of technology progression, aircraft sizing was conducted for two different sets of technology assumptions for electric components, and the results were compared with conventional baseline aircraft.

• Composites Research
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• v.23 no.6
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• pp.61-66
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• 2010

In this paper, the variation of mechanical properties of T800 carbon/epoxy composites according to the forming pressure, which was referred to previous studies on a filament winding process, were investigated. The specimens of all the tests were fabricated by an autoclave de-gassing molding process controlling forming pressure (absolute pressures of 0.1MPa, 0.3MPa, 0.7MPa including vacuum) and water jet cutting after fabricating composite laminates. Various tensile tests were performed for in-plane properties and interlaminar properties were also measured by using Iosipescu test jig. Fiber volume fraction was measured to correlate the property variation and the forming pressure. This properties are expected to be utilized in the design of Type III pressure vessel for hydrogen vehicles which uses the same carbon fiber (T800 carbon fiber) for the filament winding process.