• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.870-877
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• 2008

Numerical analysis is applied to model Pt-catalyzed reaction in a micro-scale combustor fueled by butane. The reaction constants of catalytic oxidation are determined from plug flow model with the experimental data. Orders of magnitude between the chemical reaction rate and the mass transfer rate are carefully compared to reveal which mechanism plays a dominant role in the total fuel conversion rate. For various conditions of fuel flow rate and surface temperature, the profiles of Sherwood number are investigated to study the characteristics of the mass transport phenomena in the micro-tube combustor.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.630-635
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• 2001

The characteristics of spatter generation in the short circuit transfer region of $CO_2$ welding was investigated. Spatteriing phenomena could be classified into three types : Type I generated due to the abrupt increase of arc voltage in arcing duration. Type II by the gas ejection from molten metal and Type III generated by the arc instability at the moment of arc re-ignition just after short circuiting. Main observed types were dependent on the chemical composition of welding wires. The case of YCW12 wires was mainly composed of spatters generated by Type l and Type II, while most, spatters in YCW11 wires were generated by Type II and Type III.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.48-55
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• 2012

Degradation of performance and life time of a functional material or device thereof is induced, to a great extent, by mass transfer in the material that is driven by various thermodynamic forces imposed intentionally or accidentally during its operation or service. The forces are any gradient of intensive thermodynamic variables, component chemical potentials, electrical potential, temperature, stresses, and the like. This paper reviews electric-field induced degradation phenomena in ionic solid compounds including insulation resistance degradation, crystal shift, microstructural alterations, compositional unmixing, and compound decomposition. Their inner workings are also discussed qualitatively.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.502-503
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• 2008

The modelling of PEMFC(Proton Exchange Membrane Fuel Cell) has been studied in many kinds of methods. But there are some limitations in application of the developed models to analysis transient phenomena of power systems. The PSCAD/EMTDC is very popular simulation tool in power system areas. To analysis power systems interconnected to PEMFCs, the PSCAD/EMTDC model of the PEMFCs is needed. In this paper, we developed a PSCAD/EMTDC model of PEMFC based on electro-chemical characteristic equations of PEMFC. Also, we performed simulations using the developed model in the PSCAD/EMTDC program and tested appropriateness of the proposed the models. The simulations showed good results.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2005.05a
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• pp.50-57
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• 2005

Although the bulk composition of materials is one of the major considerations in extractive metallurgy and environmental science, surface composition and topography (edges and dislocations are preferred sites for physicochemical reactions) control surface reactivity, and consequently play a major role in determining metallurgical phenomena and pollution by heavy metals and organics. An understanding of interaction mechanisms of different chemical species with the mineral surface in an aqueous media is very important in natural environment and metallurgical processing. X-ray photoelectron spectroscopy (XPS) has been used as an ex-situ analytical technique, but the material to be analyzed can be any size from $100{\mu}m$ up to about 1 cm. It can also measure mixed solids powders, but it is impossible to ascertain the original source of resulting x-ray signals where they were emitted from, since it radiates and scans the macro sample surface area.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.1024-1027
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• 2002

In this study, we have investigated the substitutional effects of In ions with divalent ones in the $Srln_2O_4:Pr^{3+}$ phosphors and the relative change of the red and blue emissions. The substitutional Zn ions greatly intensified the blue emission band at 492 nm, but the red emission band at 608 nm was relatively less changed. On the other hand, Cd ions have no effect on the relative intensities. We explained the phenomena in connection with the distance of Pr-D, i.e., covalency experienced by a $Pr^{3+}$ion.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.176-186
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• 1996

The phenomena of drag reduction using small quantities of a liner macromolecules has attracted the attention of many experimental investigations. On the other hand drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. But the research on dragreduction in two phase flow is not sufficient. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity and turbulent intensity whether polymer additives a horizontal single and two phase system or not. Flow pattern of air-water two phase flow was classified by electrical conductivity probe signal. Velocities and turbulent intensities of signal were measured simultaneously with a Hot-film anemometer.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.2
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• pp.163-170
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• 1995

The STEM II(Sulfur Transport Eulerian Model II) was adapted to investigate air pollutant transport phenomena between Eastern China and Korea. The movement of the high concentration region was clearly identified for the sulfate but was mot visible for SO$_{2}$. The 10.sim. 16 times more amount of SO$_{2}$ is transported to Korea compared to that of the local emission while the amount of the sulfate transported to Korea is 1 .sim. 1.3 times more than that of the sulfate produced by photo-chemical reaction in Korea. APTIs(Air Pollutant Transport Indices) for SO$_{2}$ and sulfate are approximately 0.85, which implies that the most of the SO$_{2}$ and sulfate existed in Korea are transported from Eastern China.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.49-54
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• 2006

The present study conducted a numerical modeling on the diesel SCR (selective catalytic reduction) system using ammonia as a reductant over vanadium-based catalysts $(V_2O_5-WO_3/TiO_2)$. Transient modeling for ammonia adsorption/desorption on the catalyst surface was firstly carried out, and then the SCR reaction was modeled considering for it. In the current catalytic reaction model, we extended the pure chemical kinetic model based on laboratory-scale powdered-phase catalyst experiments to the chemico-physical one applicable to realistic commercial SCR reactors. To simulate multi-dimensional heat and mass transfer phenomena, the SCR reactor was modeled in two dimensional, axisymmetric domain using porous medium approach. Also, since diesel engines operate in transient mode, the present study employed an unsteady model. In addition, throughout simulations using the developed code, effects of space velocity on the DeNOx performance were investigated.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.29-36
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• 2004

A numerical study is carried out on the detonation wave propagation through a T-shaped flame tube, which represents a crucial part of the combustion wave ignition (CWI) system aimed for simultaneous ignition of multiple combustion chambers by delivering detonation waves. The formulation includes the Euler equations and an induction-parameter model. The reaction rate is treated based on a chemical kinetics database obtained from a detailed chemistry mechanism. A second-order implicit time integration and a third-order TVD algorithm are Implemented to solve the theoretical model numerically. A total of more than two-million grid points are used to provide direct insight into the dynamics of the detonation wave. Several important phenomena including detonation wave propagation, degeneration, and re-initiation are carefully examined. Information obtained can be effectively used to facilitate the design and optimization of the flame tubes of CWI systems.