• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.165-165
• /
• 2001

Purpose： To obtain quantitative diffusion-tensor anisotropy information of human cerebral structu using turbo STEAM diffusion-tensor imaging. Method： Quantitative diffusion anisotropy MR images were obtained in 7 healthy adults using turbo STEAM sequence and a combination of tetrahedral and orthogonal diffusi gradients. Both relative anisotropy(RA) and fractional anisotropy(FA) values were measured various brain regions. The anisotropy index was then compared with the reported valu resulting from EPI-based diffusion tensor imaging.

• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.138-138
• /
• 2001

Purpose： To obtain quantitative diffusion-tensor anisotropy information of human cerebral structu using turbo STEAM diffusion-tensor imaging. Method： Quantitative diffusion anisotropy MR images were obtained in 7 healthy adults using turbo STEAM sequence and a combination of tetrahedral and orthogonal diffusi gradients. Both relative anisotropy(RA) and fractional anisotropy(FA) values were measured various brain regions. The anisotropy index was then compared with the reported valu resulting from EPI-based diffusion tensor imaging.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.7 no.2
• /
• pp.26-33
• /
• 2011

To evaluate steam oxidation behaviours of Alloy 617 and Haynes 230, oxidation test were performed at $900^{\circ}C$ in steam and $steam+20\;vol.-%\;H_2$ environments. Oxidation rate in steam condition was similar to that in air for Alloy 617, while it was slightly lower for Haynes 230. When hydrogen was added to steam, oxidation rate was enhanced. Isolated $MnTiO_3$ particle were formed on $Cr_2O_3$ oxide layer and sub layer $Cr_2O_3$ were formed in steam and $steam+20\;vol.-%\;H_2$ for Alloy 617. On the other hands, $MnCr_2O_3$ layer were formed on top of $Cr_2O_3$ oxide layer for Haynes 230. The extensive sub layer $Cr_2O_3$ formation was resulted from the oxygen inward diffusion in such environments. When hydrogen was added, the oxide morphology was changed from polygonal to platelet because of the accelerated diffusion of cations under the oxide layer. In addition, decarburized zone was extended as hydrogen participated into the reactions causing carbide dissolution.

• Transactions of the Korean hydrogen and new energy society
• /
• v.13 no.3
• /
• pp.214-223
• /
• 2002

Kinetic and effectiveness factors for methanol steam reforming using commercial copper-containing catalysts in a plug flow reactor were investigated over the temperature ranges of $180-250^{\circ}C$ at atmospheric pressure. The selectivity of $CO_2$/$H_2$ was almost 100%, and CO products were not observed under reaction conditions employed in this work. It was indicated that $CO_2$ was directly produced and CO was formed via the reverse water gas shift reaction after methanol steam reforming. The intrinsic kinetics for such reactions were well described by the Langmuir-Hinshelwood model based on the dual-site mechanism. The six parameters in this model, including the activation energy of 103kJ/mol, were estimated from diffusion-free data. The significant effect of internal diffusion was observed for temperature higher than $230^{\circ}C$ or particle sizes larger than 0.36mm. In the diflusion-limited case, this model combined with internal effectiveness factors was also found to be good agreement with experimental data.

• Proceedings of the KSMRM Conference
• /
• 2001.11a
• /
• pp.167-167
• /
• 2001

Purpose： To obtain normative human skeletal muscle data and evaluate quantitative diffusion-ten anisotropy information using diffusion-tensor imaging technique. Method： Quantitative extremity muscle diffusion tensor MR images were obtained in 5 healt adults by using turbo STEAM sequence and a combination of tetrahedral and orthogon diffusion gradients. Relative anisotropy(RA) and fractional anisotropy(FA) values we measured in soleus and gastrocnemius muscle in addition to mean ADC value.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.63-66
• /
• 2007

Reformers which produce hydrogen from natural gas are essential for the operation of residential PEM fuel cells. For this purpose, steam-methane reforming reactions with Ni catalysts is primarily utilized. Commercial Ni catalysts are generally made to have porous pellet shapes in which Ni catalyst particles are uniformly dispersed over Alumina support structures. This study numerically investigates the reduction of catalyst effectiveness due to the mass transport resistances posed by porous structures of spherical catalyst pellets. The multi-component diffusion through porous media and the accurate kinetics of reforming reaction is fully considered in the numerical model. The preliminary results on the variation of the effectiveness factor according to different operation conditions are presented, which is planned to be used to develop correlations in future studies.

• Journal of Korean Institute of Industrial Engineers
• /
• v.42 no.3
• /
• pp.222-230
• /
• 2016

As the global game market has been more competitive, it has been important to analyze success factors of game products. In this paper, we applied a Bass Diffusion Model and Clustering Analysis to identify the success factors of games based on data from Steam, an international game platform. By using a diffusion model, we first categorize game products into two groups : successful and unsuccessful games. Then, each group has been analyzed by using clustering analysis based on product features such as genres, price, and minimum system requirements. As a result, success factors of a game have been identified. The result shows that customers in game industry appreciate sophisticated contents. Unlike many other industries, price is not considered as a key success factor in the game industry. Expecially, advanced independent video games (commonly referred to as indie games) with killer contents show competitiveness in the market.

• Textile Coloration and Finishing
• /
• v.19 no.6
• /
• pp.21-27
• /
• 2007

The factors which affect the absorption and diffusion of disperse dye in print paste for polyester film were investigated using film roll method. When Emvatex print paste of different disperse dye concentrations were fixed by high temperature steaming(HTS) for 2 hr at $190^{\circ}C$, the dye uptake and diffusion distance of 50g/kg dye concentration for PET film were very low, but those of 100$\sim$300g/kg were increased with increasing dye concentration. It was found that sodium alginate(5%) was more effective for the absorption and diffusion of disperse dye to PET film than CMC(3%) and Emvatex(18%), and Emvatex showed comparatively low absorption in three thickeners used. The dye uptake and diffusion distance of disperse dye in sodium alginate paste for PET film were increased with increasing paste thickness to $160\sim180{\mu}m$, but were decreased at $200\sim220{\mu}m$ in both fixations of baking and HTS for 2 hr at $190^{\circ}C$, and were far more largely increased by fixation of HTS than baking because steam was very important for fixation. Also it was confirmed that dye uptake was slightly increased as steam supply pressure was raised from 1 $kg/cm^2$ to 2 $kg/cm^2$, andthe dye uptake and diffusion distance of disperse dye were outstandingly increased with raising fixing temperature from $170^{\circ}C$ to $190^{\circ}C$ and fixing time from 0.5 hr to 3 hr in the fixation of HTS.

• Journal of the Korean institute of surface engineering
• /
• v.34 no.6
• /
• pp.568-574
• /
• 2001

Mixed powders of Fe + 0.7% C, Fe + 0.7% C + 1.6% Cu, and Fe + 0.7% C + 0.3% MnS were pressed in a mold so that the green-compact densities were 6.3, 6.5, 6.7, and 6.9 g/㎤, respectively. Then, the compacts were sintered at $1125^{\circ}C$ for 30 minutes and subsequently steam treated at $600^{\circ}C$ for 60 minutes. From the results, it was found that the overall properties of the steam-treated compacts, such as the weight gain of the sintered compacts, the diffusion of oxides into the sintered compacts, the surface hardness, and the formation of surface oxide layer, were primarily influenced by the density of the compacts and the oxides that were formed on the surface of the compacts by the steam treatment.

• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.394-401
• /
• 2019

The failure of steam generators (SGs) due to corrosion is one of the most important problems in power plants. Impurities usually accumulate in the hot sides of SG and form deposits on the SG surfaces. In this paper, the sensitivity analysis of the accumulation of water impurities in the heat exchangers of nuclear power plants is presented. The convection-diffusion equation of the liquid phase on the heated surfaces is derived and then solved by the finite volume method. Also, the effects of the thermal-hydraulic parameters in the form of dimensionless numbers, such as $Pe_q$, $Pe_u$, $k_q$(relative solubility of impurity between the steam and water) on the impurities concentration are studied.