• Bulletin of the Korean Chemical Society
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• v.4 no.1
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• pp.25-28
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• 1983

The effect of internal rotation of methyl group in liquid perdeuterotoluene on nuclear quadrupole relaxation of methyl deuterons is investigated. A model of a spherical diffusor undergoing rotational diffusion is extended to include the extended diffusion of internal rotation. The overall reorientational correlation time in the presence of internal rotation is explicitly given as an analytical function of the angular momentum correlation time. Also, the degree of inertial effect in the internal rotation is evaluated.

• Computers and Concrete
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• v.22 no.3
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• pp.319-326
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• 2018

RC (Reinforced Concrete) members are always subjected to loading conditions and have construction joints when constructed on a big scale. Service life for RC structure exposed to chloride attack is usually estimated through chloride diffusion test in sound concrete, however the test is performed without consideration of effect of loading and joint. In the present work, chloride diffusion coefficient is measured in concrete cured for 1 year. In order to evaluate the effect of applied load, cold joint, and mineral admixtures, OPC (Ordinary Portland Cement) and 40%-replaced GGBFS (Ground Granulated Blast Furnace Slag) concrete are prepared. The diffusion test is performed under loading conditions for concrete containing cold joint. Investigating the previous test results for 91 days-cured condition and the present work, changing diffusion coefficients with applied stress are normalized considering material type and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted, and service life in each location is evaluated considering the effects of applied stress, cold joint, and GGBFS. From the work, varying service life is simulated under various loading conditions, and the reduced results due to cold joint and tensile zone are quantitatively evaluated. The effect of various conditions on diffusion can provide more quantitative evaluation of chloride behavior and the related service life.

• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.74-81
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• 2010

In this study, soot formation characteristics on the instability of laminar diffusion flames were investigated experimentally using a concentric co-flow burner. When a small amount of air was supplied through an inner nozzle, a stable propane laminar diffusion flame became unstable and began to oscillate mainly due to the dilution effect. The increase of air flow rate transformed an oscillating non-sooting flame into a stable nonsooting flame. When the air flow rate was continuously increased an inner flame was formed and the flame was changed to an oscillating sooting flame, an oscillating non-sooting flame and finally a stable non-sooting hollow flame. When the air flow rate was decreased, a non-sooting hollow flame was eventually changed back to a stable non-sooting flame. The presence of an inner flame, however, altered the soot formation characteristics of a flame. More soot production was observed with the presence of an inner flame. The increased or decreased soot formation/oxidation rates, the radiation heat loss, and the heating effect of inner flames are most likely to be responsible for the observed instability of laminar diffusion flames.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.147-155
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• 2001

Experimental investigations were conducted for two hydrogen-nitrogen coaxial jet diffusion flames. A flame was a conventional coaxial jet diffusion flame and the other was a coaxial jet diffusion flame of which ambient air-jet turbulence was intensified. In this study, firstly two kinds of NOx measuring system were campared by using different convertors, secondly the NOx formation characteristics were investigated in order to examine the effect of turbulence intensity. In this study it is known that stainless convertor has some problem in the converting process from NO$_2$to NO in fuel rich region but molybdenum convertor can detect the amount of NOx correctly. The increase of turbulence intensity reduces the thermal NOx less than a half in our experiment and this effect is conspicuous near the nozzle. The conversion rate from NO to NO$_2$and the portion of NO$_2$among NOx are increased with turbulence intensity. These NOx measurements will help to understand the influences of turbulence intensity on NOx formation.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.332-340
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• 2003

Crosslinked poly(methyl methacrylate) particles from 2.4 to $8.1{\mu}m$ in diameter were prepared by homogenized suspension polymerization. The effect of polymerization parameters such as homogenizing speed, homogenizing time and stabilizer concentration on the particle size were examined. Optical diffusion films were prepared with the crosslinked poly(methyl methacrylate) particles. The effect of film thickness, particle size, and particle size distribution on transmittance and haze of optical diffusion film was examined. Transmittance of optical diffusion film increased with increasing particle size and decreasing film thickness. Haze increased with increasing film thickness and decreasing particle size. We also found the existence of an optimum ratio for optical performance when the mixture of small particle and large particle was used.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.479-484
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• 2009

The effect of anode gas channel height on gas diffusion and cell performance in a 100 $cm^2$ class molten carbonate single cell is investigated. Single cell separators with three different channel height are used. The effect of the gas channel height on the distribution of the reactive gas concentration is evaluated by the two-dimensional concentration diffusion equation. The overpotential caused by concentration drop with different channel height is estimated by the voltage decay related to diffusion of reactants, well known as concentration polarization, using limiting current density. The estimation could have the possibility to identify the reactant mass transfer polarization in the complicate factors of the overall electrodes.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.225-228
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• 2017

In this study, zinc tin oxide (ZTO) films were prepared on indium tin oxide (ITO) glasses and annealed at different temperatures under vacuum to investigate the correlation between the Ohmic/Schottky contacts, electrical properties, and bonding structures with respect to the annealing temperatures. The ZTO film annealed at $150^{\circ}C$ exhibited an amorphous structure because of the electron-hole recombination effect, and the current of the ZTO film annealed at $150^{\circ}C$ was less than that of the other films because of the potential barrier effect at the Schottky contact. The drift current as charge carriers was similar to the leakage current in a transparent thin-film device, but the diffusion current related to the Schottky barrier leads to the decrease in the leakage current. The direction of the diffusion current was opposite to that of the drift current resulting in a two-fold enhancement of the cut-off effect of leakage drift current due to the diffusion current, and improved performance of the device with the Schottky barrier. Hence, the thin film with an amorphous structure easily becomes a Schottky contact.

• Journal of Welding and Joining
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• v.22 no.1
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• pp.77-82
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• 2004

The effect of bonding condition on tensile properties of joints diffusion bonded spheroidal graphite cast iron, FCD60 to Cr-Mo steel, SCM 440 was investigated. Diffusion bonding was performed with various temperatures, holding times, pressures and atmospheres. All tensile specimens were fractured at the bonding interface. The tensile strength and elongation was increased with increasing bonding temperature. Especially, tensile strength of joints bonded at 1123K was higher than that of a raw material, FCD60, and tensile strength of joints bonded at 1173K was equal to that of a raw material, SCM440, but elongation of all joints was lower than those of raw materials. There was little the effect of holding time on the tensile properties. In comparison with bonding atmosphere, the difference of tensile strength was not observed, but elongation of joint bonded at vacuum(6.7mPa and 67mPa) was higher than that of Ar gas. Higher the degee of vacuum, elongation increased. Tensile properties of diffusion bonds depended on microstructures of cast iron at the interface and void ratio. Microstructures of cast iron at interface changed with temperature, because decarburizing and interdiffusion at the interface occurs and transformation of austenite-1 ferrite + graphite occurs on the cooling process. The void ratio decreased with increasing temperature, especially, effected on the elongation.

• Korean Management Science Review
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• v.32 no.3
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• pp.29-36
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• 2015

In this research, we analyze the sensitivity of the network density to the estimates for the Bass model parameters with both theoretical model and a simulation. Bass model describes the process that the non-adopters in the market potential adopt a new product or an innovation by the innovation effect and imitation effect. The imitation effect shows the word of mouth effect from the previous adopters to non-adopters. But it does not divide the underlying network structure from the strength of the influence over the network. With a network based Bass model, we found that the estimate for the imitation coefficient is highly sensitive to the network density and it is decreasing while the network density is decreasing. This finding implies that the interpersonal influence can be under-looked when the network density is low. It also implies that both of the network density and the interpersonal influence are important to facilitate the diffusion of an innovation.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.677-682
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• 2001

In this study, a method to evaluate diffusion coefficient of chloride ion in cracked concrete is proposed. For cracked concrete having either anisotropic or isotropic crack network, each crack of saturated concrete is considered as a V shape crack, and an effective diffusion coefficient is expressed with diffusion coefficients of cracked part and noncracked part and a so-called crack spacing factor. A comparison with experimental results shows that the diffusion coefficient for cracked concrete is accurately predicted by the effective diffusion coefficient. Prediction results also show that the cracks in concrete markedly change the diffusion properties and accelerate penetration of drifting species. The method in this paper can be effectively used to consider the effect of cracks on concrete diffusion coefficient of cracked concrete.