• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.65-69
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• 2007

For self-developed alkali-alkaline earth-silicate and commercial glass melts for plasma display panel substrate, the corrosion behavior of fused casting refractory consisting of $Al_2O_3-ZrO_2-SiO_2$ was examined at the temperature corresponding to $10^2\;dPa{\cdot}s$ of melt viscosity by static finger methode. The corroded refractory specimens showed a typical concave shape due to interfacial convection of melts at their flux line. However, the corrosion thickness by commercial glass melts was $6\sim10$ times comparing to that by the self?developed melts. From the view point of the glass composition and the role of alkaline earth in glass network, it was discussed the effect of alkali/alkaline earth diffusion and temperature on the refractory corrosion.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.175-176
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• 2000

Electric fields and the wall voltages in a surface-type AC PDP cell were measured using a Laser Induced Fluorescence Spectroscopy. For the condition of He 100Torr, 200V sustain voltage and 50kHz sustain frequency, the wall voltage dropped from about 50V to about -75V within $1{\mu}sec$ after the main discharge. And the wall voltage decreased with the rate of $10.8V/{\mu}sec$ due to the accumulation of the space charges after $1{\mu}sec$. But when the operating pressure was 40Torr, it increased with the rate of $4.5V/{\mu}sec$ because the diffusion effect of the wall charge on MgO surface was more dominant than the accumulation effect of the space charges. During the pulse-off period, the wall voltage decreased slightly due to the diffusion of the wall charge. When the sustain voltage was 250V, the self-erasing discharge occurred, and the absolute value of the wall voltage decreased rapidly just after the pulses were off, which was caused by the accumulation of the charges generated by the self-erasing discharge.

• Journal of the Korean Chemical Society
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• v.19 no.3
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• pp.149-155
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• 1975

Pivalic acid, which has a globular shape and is a plastic crystal, has been examined by means of temperature-dependent with-line proton magnetic resonance spectroscopy. Results of temperature-dependent line width, second moment, and spin-lattice relaxation time studies of pivalic acid were interpreted in terms of dynamic behavior and hydrogen bonding. The dynamic behavior consists of superimposed reorientation of the methyl groups about their three-fold axes$(C_3) and of the molecule about the central C-C bond(C_3'),$ general molecular reorientation about the center of gravity, and molecular self-diffusion. Activation energies for the motional processes have been obtained from line width measurements using the modified Bloembergen, Purcell, and Pound theory and from spin-lattice relaxation time measurements. The results were compared with the Pople-Karasz theory of fusion and the agreement was found to be poor. The discrepancy was interpreted in terms of hydrogen bonding in this molecule.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.696-700
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• 2002

The Ti-aluminide intermetallic compound was formed from high purity elemental Ti and Al foils by self-propagating, high-temperature synthesis(SHS) in hot press. formation of $TiAl_3$ at the interface between Ti and Al foils was controlled by temperature, pressure, heating rate, and so on. According to the thermal analysis, it is known in this study that the heating rate is the most important factor to form the intermetallic compound by this SHS reaction. The V layer addition between Al and Ti foils increased SHS reaction temperatures. The fully dense, well-boned inter-metallic composite($TiA1/Ti_3$Al) sheets of 700 m thickness were formed by heat treatment at $1000^{\circ}C$ for 10 hours after the SHS reaction of alternatively layered 10 Ti and 9 Al foils with the V coating layer. The phases and microstructures of intermetallic composite sheets were confirmed by EPMA and XRD.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.249-254
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• 2014

Due to their unique properties, tungsten borides are good candidates for the industrial applications where certain features such as high hardness, chemical inertness, resistance to high temperatures, thermal shock and corrosion. In this study, conditions were investigated for producing tungsten boride powder from tungsten oxide($WO_3$) by self-propagating high-temperature synthesis (SHS) followed by HCl leaching techniques. In the first stage of the study, the exothermicity of the $WO_3$-Mg reaction was investigated by computer simulation. Based on the simulation experimental study was conducted and the SHS products consisting of borides and other compounds were obtained starting with different initial molar ratios of $WO_3$, Mg and $B_2O_3$. It was found that $WO_3$, Mg and $B_2O_3$ reaction system produced high combustion temperature and radical reaction so that diffusion between W and B was not properly occurred. Addition of NaCl and replacement of $B_2O_3$ with B successfully solved the diffusion problem. From the optimum condition tungsten boride($W_2B$ and WB) powders which has 0.1~0.9 um particle size were synthesized.

• Bulletin of the Korean Chemical Society
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• v.5 no.3
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• pp.104-108
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• 1984

The self-diffusion experiment of THO was performed across a series of copolymer hydrogel membranes at different temperatures. Copolymer hydrogel membranes were prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA) and 2-aminoethyl methacrylate (AEMA) in the presence of the solvent and the crosslinker, ethylene glycol dimethacrylate (EGDMA). By changing the crosslinker content and the ratio of HEMA and AEMA monomer, two series of copolymer hydrogel membranes were synthesized. The tagging material was THO and efflux of THO was counted on a Liquid Sc-intillation Counter. The experimental data show that the permeability decreases as the amount of EGDMA and the mole fraction of HEMA increase, and the permeability is proportional to the temperature. The partition coefficient shows a parallel trend with permeability. Using the relationship between viscosity and diffusivity, the viscosity of water within the membrane was obtained. According to the result, the viscosity of watler within the membrane has the same value with those of supercooling water. And we obtained the activation energy of THO for transport in the membrane by using Arrhenius plotting.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.897-904
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• 1999

We have presented the thermodynamic, structural and dynamic properties of liquid pentane isomers - normal pentane, isopentane, and neopentane - using an expanded collapsed atomic model. The thermodynamic properties show that the intermolecular interactions become weaker as the molecular shape becomes more nearly spherical and the surface area decreases with branching. The structural properties are well predicted from the site-site radial, the average end-to-end distance, and the root-mean-squared radius of gyration distribution func-tions. The dynamic properties are obtained from the time correlation functions - the mean square displacement (MSD), the velocity auto-correlation (VAC), the cosine (CAC), the stress (SAC), the pressure (PAC), and the heat flux auto-correlation (HFAC) functions - of liquid pentane isomers. Two self-diffusion coefficients of liquid pentane isomers calculated from the MSD's via the Einstein equation and the VAC's via the Green-Kubo relation show the same trend but do not coincide with the branching effect on self-diffusion. The rotational re-laxation time of liquid pentane isomers obtained from the CAC's decreases monotonously as branching increases. Two kinds of viscosities of liquid pentane isomers calculated from the SAC and PAC functions via the Green-Kubo relation have the same trend compared with the experimental results. The thermal conductivity calculated from the HFAC increases as branching increases.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.309-315
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• 1991

The thermal transport coefficients-the self-diffusion coefficient, shear viscosity, and thermal conductivity-of liquid argon at 94.4 K and 1 atm are calculated by non-equilibrium molecular dynamics (NEMD) simulations of a Lennard-Jones potential and compared with those obtained from Green-Kubo relations using equilibrium molecular dynamics (EMD) simulations and with experimental data. The time-correlation functions-the velocity, pressure, and heat flux auto-correlation functions-of liquid argon obtained from the EMD simulations show well-behaved smooth curves which are not oscillating and decaying fast around 1.5 ps. The calculated self-diffusion coefficient from our NEMD simulation is found to be approximately 40% higher than the experimental result. The Lagrange extrapolated shear viscosity is in good agreement with the experimental result and the asymptotic formula of the calculated shear viscosities seems to be an exponential form rather than the square-root form predicted by other NEMD studies of shear viscosity. The agreement for thermal conductivity between the simulation results (NEMD and EMD) and the experimental result is within statistical error. In conclusion, through our NEMD and EMD simulations, the overall agreement is quite good, which means that the Green-Kubo relations and the NEMD algorithms of thermal transport coefficients for simple liquids are valid.

• Korean Journal of Environmental Agriculture
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• v.15 no.1
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• pp.116-127
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• 1996

Recent development in Japan on jumbo formulation of pesticides for paddy application by hand throw was reviewed. In addition, the diffusion of liquid formulations in water was examined to establish the research strategy for the jumbo formulation. Research on jumbo formulation in Japan has been focused on gas-generating formulations and self-emulsifiable formulations. Although continuous efforts to minimize the problem of pesticide deposit on the treated site have been made for the gas-generating formulations, much work is still needed to establish a generally acceptable formulation method and to commercialize a herbicide formulation. The self-emulsifiable jumbo formulations have recently been investigated. These formulations could simply be processed and showed relatively high biological efficacy. The emulsifiable concentrate was more diffusible than the suspension concentrate in water. The diffusion of the emulsifiable concentrate was not greatly disturbed by floating obstacles. And the diffusion rate was high when the specific grabity was lower than one.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.387-392
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• 2013

The purpose of this study investigate the main factors of the diffusion of digital contents and consumer's participation behavior, consumption culture and examine the experiential perspective to consumer's information selection behavior. In digital network, the social presence, challenge, self-presentation, arousal and emotional feeling were significant variables to flow experience. Experiential perspectives focused on the search of identity and self-determination were main basic perspective to explain the diffusion of digital contents, consumer participation. This research result applied to media and device strategy to up-coming digital convergence and adapted to product planning and development, user friendly navigation and emotional human-centered service module.