• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1459-1466
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• 1994

A novel technique for determining the oxygen tracer diffusion coefficients in oxides was developed. After the 16O-18O solid-gas exchange reactions between 16O in the oxides and 18O in the ambient gas, Raman spectra of the cross sections of oxide samples were measured in a spatial resolution of 5 ${\mu}{\textrm}{m}$. From thus obtained Raman spectra, depth profiles of 18O concentration in the oxide samples were calculated. The oxygen tracer diffusion coefficients and the surface exchange coefficients were determined under the assumptions that samples are semi-infinite slab and that the surface exchange reactionsare not negligible. The oxygen tracer diffusion coefficient of 2.8 mol% Y2O3-containing tetragonal ZrO2 polycrystals, 8 mol% Y2O3-containing ZrO2 polycrystals, and 10 mol% Y2O3-containing cubic ZrO2 single crystals (along the a axis) are as follows.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.2
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• pp.59-66
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• 2007

The oxygen distribution at steady state is analyzed mathematically in a hexagonal cylinder. The domain is penetrated by parallel cylindrical capillaries of different oxygen squirt. Asymptotic solution is used to determine the effect of axial diffusion. Oxygen concentration profiles are displayed at some positions of capillary-beds. At the venous end some tissue areas suffer from a shortage of oxygen.

• Journal of the Korean Ceramic Society
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• v.28 no.12
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• pp.989-995
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• 1991

By means of the secondary ion mass spectrometer, the tracer diffusion of oxygen in rutile single crystal was measured as function of temperature and oxygen partial pressure. The tracer diffusivity was determined from the depth profile of 18O. The Po2 dependence of D suggests that the dominant defects in TiO2-y are oxygen vacancies (V{{{{ { ‥} atop { o} }}) and interstitial titanium ions (Ti{{{{ {‥‥} atop {i} }}). The doubly ionized oxygen vacancies are prominent at low temperature and Po2. However, the tetravalent interstitial titanium ions predominate at teperature above 120$0^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.37-42
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• 2012

Mass transport near grain boundary in a magnetite bi-crystal has been estimated at 823 K by finite element method. Mass transport near grain boundary strongly depends on the diffusivities along grain boundary. If grain boundary diffusion has the same oxygen activity dependence as lattice diffusion, there is no mass transport between grains and grain boundary. On the other hand, mass transport between grains and grain boundary is observed in the case that grain boundary diffusion has different oxygen activity dependence.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.99-107
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• 2003

The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimens were made from a UO$_2$ single crystal powder with natural enrichment. Weight and grain size were 300mg and ($23\mu\textrm{m}$, respectively. Oxygen potentials were obtained from an oxygen sensor. Released fractions were obtained from both results of gamma scans and quantitative analysis with MCNP code, The annealing test was performed at three temperatures at once. Diffusion coefficients of Xe-133 were calculated using slope of Booth theory in each O/M ratios. Activation energy and the pre-exponential factor of the diffusion coefficient were obtained. The activation energy of near stoichiomeric $UO_2$ is 310 kJ/mol. The measured values of near stoichiometric $UO_2$ are very close to other data available. Diffusion coefficients increase with hyper-stoichiometry, due to higher concentration of cation vacancies.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.72-82
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• 2007

This paper relates to reducing the temperature of a cryogenic liquid by contacting it with gas bubbles, which can be characterized by diffusion-driven evaporative cooling, The characteristic of diffusion-driven evaporative cooling is thoroughly examined by theoretical. analytical and experimental methods specifically for the case of helium injection into liquid oxygen. The results reveal that if the gaseous oxygen partial pressure in helium bubbles is lower than the liquid oxygen vapor pressure, cooling occurs autonomously due to diffusion mass transfer. The method of lowering the injected helium temperature turns out to be very effective for cooling purpose.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.35-43
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• 2008

Purpose: This review article was written to investigate how the various factors, such as lacrimal thickness, CL's thickness and Dk, affects the influx of $O_2$ diffusion into the cornea. Methods: A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. Results: The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. Conclusions: It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency at/inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.2
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• pp.85-93
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• 2005

Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF) . These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of Li$_{2}$O. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.

• Journal of the Korean Society of Combustion
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• v.21 no.4
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• pp.6-15
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• 2016

The oxygen fuel MILD (Moderate or Intense Low-oxygen Dilution) combustion has been considered as one of the promising combustion technology for flame stability, high thermal efficiency, low emissions and improved productivity. In this paper, the effect of oxygen and fuel injection condition on formation of MILD combustion was analyzed using lab scale oxygen fuel MILD combustion furnace. The results show that the flame mode was changed from a diffusion flame mode to a split flame mode via a MILD combustion flame mode with increasing the oxygen flow rate. A high degree of temperature uniformity was achieved using optimized combination of fuel and oxygen injection configuration without the need for external oxygen preheating. In particular, the MILD combustion flame was found to be very stable and constant flame temperature region at 7 KW heating rate and oxygen flow rate 75-80 l/min.

• Journal of the Korean Ceramic Society
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• v.20 no.2
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• pp.129-134
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• 1983

MgO.$Al_2O_3$ polycrstalline spinel powder was subjected to vaporization over the temperature range of 1150-130$0^{\circ}C$ under H2 atmosphere. Diffusion coefficient of oxygen ion through the spinel were calculated using the measure vaporization rates as follows : D=28.4 exp(-901500/RT) Reference data of the vaporization rates of MgO.$8Al_2O_3$ single crystal spinel were applied to the vaporiza-tion model proposed in this study and were calculated to give the oxygen ion diffusion coefficients over the tempera-ture 1700-195$0^{\circ}C$. The obtained diffusion coefficients are as follows: $D=3.20{\times}106$ exp(-155600/RT)