• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2696-2701
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• 2007

For the analysis of a two-phase flow, the interaction between two phases such as the interfacial momentum or heat transfer is proportional to the interfacial area. So the interfacial area concentration (IAC) is one of the most important parameters governing the behavior of each phase. This study focuses on the development of a computational fluid dynamics (CFD) code for investigating a boiling flow with a one-group IAC transport equation. It was based on the two-fluid model and governing equations were calculated by SMAC algorithm. For checking the robustness of the developed code, the experiment of a subcooled boiling in a vertical annulus channel was analyzed to validate the capability of the IAC transport equation. As the results, the developed code was confirmed to have the capability in predicting multi-dimensional phenomena of vapor generation and propagation in a subcooled boiling.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1679-1684
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• 2011

Interfacial reactions kinetics often differ from kinetics of bulk reactions. Here, we describe how the density change of an immobilized reactant influences the kinetics of interfacial reactions. Self-assembled monolayers (SAMs) of alkanethiolates on gold were used as a model interface and the Diels-Alder reaction between immobilized quinones and soluble cyclopentadiene was used as a model reaction. The kinetic behavior was studied using varying concentrations of quinones. An unusual threshold density of quinones (${\Gamma}_c$ = 5.2-7.2%), at which the pseudo-first order rate constant started to vary as the reaction progressed, was observed. This unexpected kinetic behavior was attributed to the phase-separation phenomena of multi-component SAMs. Additional experiments using more phase-separated two-component SAMs supported this explanation by revealing a significant decrease in ${\Gamma}_c$ values. When the background hydroxyl group was replaced with carboxylic or phosphoric acid groups, ${\Gamma}_c$ was observed at below 1%. Also, more phase-separated thermodynamically controlled SAMs produced a lower critical density (3% < ${\Gamma}_c$ < 4.9%) than that of the less phaseseparated kinetically controlled SAMs (6.5% < ${\Gamma}_c$ < 8.9%).

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.26-33
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• 2001

This article involves the application of the fractal geometry to interfacial electrochemistry. Especially, we gave our attention to impedance behaviour of the fractal electrode. First, this article briefly explained the constant phase element (CPE) in electrochemical impedance and the do Levie's transmission line model. Second, we introduced the Nyikos and Pajkossy's theoretical works to approach the CPE phenomena using the fractal geometry. Finally this article presented other various fractal models for analysing the ac response of the rough electrodes.

• Polymer Science and Technology
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• v.6 no.5
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• pp.481-487
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• 1995

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.52-56
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• 2011

Active regeneration in CDPF requires $O_2$ which regenerates soot at high temperature. However, small amount of NO can interrupt $O_2$ regeneration in CDPF. To verify this phenomena, soot oxidation experiments using a flow reactor with a $Pr/CeO_2$ catalyst are carried out to simulate Catalyzed Diesel Particulate Filter (CDPF) phenomena. Catalytic soot oxidation with and without small amount of NO is conducted under tight contact condition. As the heating rate rises, the temperature gap of maximum reaction rate is increased between with and without 50ppm NO. To accelerate the $NO_2$ de-coupling effect, CTO process is performed to eliminate interfacial contact for that time. As CTO process is extended, temperature which indicates peak reaction rate increases. From this result, it is found that small amount of NO can affect tight contact soot oxidation by removal of interfacial contact between soot and catalyst.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.115-115
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• 1999

To demonstrate the applicability of RELAP5 to the prediction of the onset offlooding in the hot leg at the reflux condensation phase during mid-loop operation, numerical analysis is performed for the counter-current flow in a horizontal pipe with the inclined riser using the RELAP5/MOD3.2.2b code. It is found that the RELAP5, simulating the CCFL phenomena using interfacial friction along with the flow regime map in the horizontal pipe, produces unsatisfactory results. Under the CCFL condition, it is observed that large oscillation exists in the flow rate, void fraction, and etc. and the liquid flow rate is much lower than that predicted by the CCFL model measured in the experiment. The CCFL model of RELAP5 for the vertical volume is extended to the model for the horizontal and inclined volumes. The horizontal volume flow regime map and interfacial friction model coupled to the CCFL model are modified. And a new correlation developed from Kang's experiment is implemented to the CCFL model of RELAP5. With this modified RELAP5, the analysis of CCFL phenomena in the horizontal pipe and hot leg geometry is performed, and produces reasonable results in comparison with experimental data.

• Vacuum Magazine
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• v.2 no.2
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• pp.4-11
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• 2015

During last two decades, remarkable progresses have been made in organic electronic devices, such as organic light-emitting device, organic photovoltaic and many other applied devices. Many of these progress are attributed to the multilayered/heterojunction device architectures, which could be achieved from the control of "interfacial energetics". In that sense, the interfacial electronic structures in organic electronic devices have a decisive role in device performance. However, the prediction of the interfacial electronic structures from each separate material is not trivial. Many complex phenomena occur at the interface and these can be only understood from thorough measurements on interfacial electronic structures in situ. Photoemission and inverse photoemission spectroscopy have been known as the most proper measurement tools to analyze these interfacial electronic structures. In this review, the basic principles of (inverse) photoemission spectroscopy and typical measurement results on organic/inorganic interfaces are introduced.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.116-120
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• 2001

Fiber fracture is one of the dominant failure phenomena to determine total mechanical properties in composites. Fiber fracture locations were measured by optical microscopic method and acoustic emission (AE) as functions of matrix toughness and surface treatment by the electrodeposition (ED), and then two methods were compared. Two AE sensors were attached on the epoxy specimen and fiber fracture signals were detected with elapsed time. The interfacial shear stress (IFSS) was measured using tensile fragmentation test and AE system. In ED-treated case, the number of the fiber fracture measured by an optical method and AE was more than that of the untreated case. The signal number measured by AE were rather smaller than the number of fragments measured by optical method, since some fiber fracture signals were lost while AE detection. However, one-to-one correspondence between the x-position location by AE and real break positions by optical method was generally established well. The fiber break source location using AE can be a valuable method to measure IFSS for semi- or nontransparent matrix composites nondestructively (NDT).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.677-682
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• 2015

We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.127-132
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• 2003

A study of high-pressure n-heptane droplet vaporization is conducted with emphasis placed on equilibrium at vapor-liquid interface. General frame of previous rigorous model[1] is retained but tailored for flash equilibrium calculation of vapor-liquid interfacial thermodynamics. The model is based on complete time-dependent conservation equations with a full account of variable properties and vapor-liquid interfacial thermodynamics. The influences of high-pressure phenomena, including ambient gas solubility, thermodynamic non-ideality, and property variation on the droplet evaporation are investigated. The governing equations and associated moving interfacial boundary conditions are solved numerically using a implicit scheme with the preconditioning method and the dual time integration technique. And a parametric study of entire droplet vaporization history as a function of ambient pressure, temperature has been conducted. Some computational results are compared with Sato's experimental data for the validation of calculations. For low ambient temperatures, the droplet lifetime first increases with pressures, then decreases for high pressures. For higher ambient temperatures, the droplet lifetime increase with less amplitude than that of low ambient temperatures, which then decreases with more amplitude than that of low temperatures. The solubility of nitrogen can not be neglected in the high pressure and it becomes higher as the pressure goes up.