• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.37-44
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• 2009

An experimental study was conducted to reduce NOx emission in RT(radiant tube)burner by using oscillating combustion processes in RIST. A solenoid valve gives the various oscillating conditions, such as oscillation frequency, duty ratio of fuel flow. In this study, we used commercial software, CFD-ACE+ to predict combustion and NOx emission characteristics for various experimental oscillation conditions. The effect of oscillation frequency and duty ratio on NOx emission will be discussed in terms of flow field, temperature and equivalence ratio distributions in detail.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.46-55
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• 2008

This study assesses the formaldehyde and TVOC emissions from bio-composites with attached fancy veneer manufactured using wood flour and polypropylene (PP) measured using the Field and Laboratory Emission Cell (FLEC) method and 20 L small chamber method. To determine and compare the effects of the adhesive, samples were prepared with different manufacturing methods. In the FLEC result, the formaldehyde emission level of the bio-composites with attached veneer by hot-press was the lowest than pure bio-composite and bio-composite attached veneer using adhesive. The TVOC emission levels are similar to the formaldehyde emission. The TVOC emission level is very low in all of the samples except fancy veneer that is attached with bio-composites using adhesive. The TVOC emission varies depending on how attaching fancy veneer. The results of the 20 L small chamber method were very similar to those obtained with the FLEC, but the correlation was not perfect. However, the FLEC method requires a shorter time than the 20 L small chamber method to measure the formaldehyde and TVOC emissions. The internal bonding strength exceeded the minimum value of $0.4N/mm^2$ specified by the KS standard. All of the bio-composites with attached veneer satisfied the KS standard.

• Journal of Multimedia Information System
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• v.2 no.4
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• pp.317-326
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• 2015

The paper deals with the analysis of the effectiveness of acoustic emission monitoring and diagnostics of engineering products. We discuss the results of the processing results of the field experiment to study the acoustic emission in the alloy and its welded joints in the presence of technological defects. We study the characteristics of the output of acoustic emission signals at different stages of elastic-plastic deformation of alloys. Analyzed acoustic chart and the output waveform of the acoustic emission for the different types of welds. Studies have shown the effectiveness of the Acoustic emission techniques and help improve the accuracy of non-destructive testing systems in problems of automation and control.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.36-52
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• 2021

As the application of nano-satellites constellation increases worldwide in the wake of New Space era, there is growing demand for the development of thrusters for precise attitude and orbit control of small satellites. Field Emission Electric Propulsion(FEEP) thruster uses a liquid metal as a propellant and accelerates the ionized liquid metal through a strong electric field at the tip of the metal surface. FEEP thruster technology is suitable for nano-satellites which require various missions for attitude and orbit control, because it provides thrust ranging from 1 µN to 1 mN with high specific impulse up to about 10,000 s and can be miniaturized due to its simple structure. In this paper, the basics of FEEP thrusters are introduced, then the current status of research and development of FEEP thrusters are presented.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.798-802
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• 2010

From time-resolved optical emission spectra, we have investigated the effects of a transverse magnetic field on the expansion of a plasma plume produced by laser ablation of a ZnO:$P_2O_5$ ceramic target in oxygen active atmosphere. The emission spectra of $Zn^{+*}$, $P^{+*}$, and $Zn^*$ neutrals in the presence of magnetic field turn out to be considerably different from those without magnetic field. The characteristics of the deposited films grown on amorphous fused silica substrates by pulsed laser deposition (PLD) are examined by analyzing their photoluminescence (PL), X-ray diffraction (XRD), and UV-visible spectra.

• Journal of Information Display
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• v.1 no.1
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• pp.63-69
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• 2000

In order to improve both the level and the stability of electron emission, Mo and Co silicides were formed from Mo mono-layer and Ti/Co bi-layers on single crystal silicon field emitter arrays (FEAs), respectively. Using the slope of Fowler-Nordheim curve and tip radius measured from scanning electron microscopy (SEM), the effective work function of Mo and Co silicide FEAs were calculated to be 3.13 eV and 2.56 eV, respectively. Compared with silicon field emitters, Mo and Co silicide exhibited 10 and 34 times higher maximum emission current, 10 V and 46 V higher device failure voltage, and 6.1 and 4.8 times lower current fluctuation, respectively. Moreover, the emission currents of the silicide FEAs depending on vacuum level were almost the same in the range of $10^{-9}{\sim}10^{-6}$ torr. This result shows that silicide is robust in terms of anode current degradation due to the absorption of air molecules.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1021-1023
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• 2003

We studied field-emission characteristics of CNTs under various pre-treatment with $NH_{3}$ plasma on the substrate. The turn-on electric field is the lowest value and field enhancement factor (${\beta}$) is he highest value in CNTs pre-treated by $NH_3$ plasma (80 W and 5 min). The field-emission property of CNTs grown on the Ta substrate is slightly better than on the W substrate.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1244_1245
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• 2009

Coating of amorphous nitride thin layers, such as boron nitride (BN) and carbon nitride (CN), has been performed on carbon nanotubes (CNTs) for the purpose of enhancing their electron-emission performances because those nitride films have relatively low work functions and commonly exhibit negative electron affinity behavior. The CNTs were directly grown on metal-tip (tungsten, approximately 500 nm in diameter at the summit part) substrates by inductively coupled plasma-chemical vapor deposition (ICP-CVD). Sharpening of the tungsten tips were carried out by electrochemical etching. Morphologies and microstructures of BN and CN films were analyzed by field-emission scanning electron microscopy (FE-SEM), energy dispersive x-ray (EDX) spectroscopy, and Raman spectroscopy. The electron-emission properties (such as maximum emission currents and turn-on fields) of the BN-coated and CN-coated CNT-emitters were characterized in terms of the thickness of BN and CN layers.

• Journal of the Korean Society of Combustion
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• v.14 no.1
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• pp.31-38
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• 2009

The effects of acoustic excitation of coaxial air on mixing enhancement and reduction of nitrogen oxides (NOx) emission were investigated. A compression driver was attached to the coaxial air supply tube to impose excitation. Measurements of NOx emission with frequency sweeping were performed to observe the trend of NOx emission according to the fuel and air flow conditions and to inquire about the effective excitation frequency for reducing NOx. Then, Schlieren photographs were taken to visualize the flow field and to study the effect of excitation. In addition, phase-locked particle image velocimetry (PIV) was performed to acquire velocity field for each case and to investigate the effect of vortices more clearly. Direct photographs and OH chemiluminescence photographs were taken to study the variation of flame length and reaction zone. It was found that acoustic forcing frequencies close to the resonance frequencies of coaxial air supply tube could reduce NOx emission. This NOx reduction was influenced by mixing enhancement due to large-scale vortices formed by fluctuation of coaxial air jet velocity.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.863-866
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• 2003

Multi-walled carbon nanotubes (CNTs) were synthesized on glass substrates in the different ramp-up heating ambient of vacuum, He, Ar, and $N_{2}$ by thermal chemical vapor deposition. CNTs with higher crystallinity were developed in the buffer gases with faster growth rates than in vacuum. Field emission characteristics were strongly related to the relative position of CNT emitters to the cathode electrodes. The areal-spread emission and instability were overcome by locating the emitters far away from the edges of cathode electrodes. The electrical conditioning of emitters improved their emission uniformity over a large area although it decreased the emission current. This study also discussed the long-term stability of CNT emitters.