• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.3
• /
• pp.265-274
• /
• 2007

A study has been conducted to clarify NO emission behavior through preferential diffusion effects of $H_2$ and H in methane-hydrogen diffusion flames. A comparison is made by employing three species diffusion models. Special concerns are focused on what is the deterministic role of the preferential diffusion effects in flame structure and NO emission. The behavior of maximum flame temperatures with three species diffusion models is not explained by scalar dissipation rate but the nature of chemical kinetics. The preferential diffusion of H into reaction zone suppresses the populations of the chain carrier radicals and then flame temperature while that of $H_2$ produces the increase of flame temperature. These preferential diffusion effects of $H_2$ and H are also discussed about NO emissions through the three species diffusion models.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.713-715
• /
• 2009

Preferred orientation of MgO protection layer is controlled via adjusting diffusion of adatom between (111) plane with highest neighbor atoms and (200) plane with lowest neighbor atoms. The diffusion of adatom could be modulated by the factors such as substrate temperature, deposition rate, and extra energy applied on adatom like ion beam energy.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.5
• /
• pp.476-480
• /
• 1984

This paper deals with nitrogen diffusion velocity and activation energy in diffusion layer and compound layer in ion-nitriding, and presents observations on the effect of deformation according to nitriding methods. During the experiment the activation energy and diffusion velocity of nitrogen have been examined in S45C steel samples. It is found that the results of an investigation correspond with the theoretical data and the ion-nitriding method offers less deformation than conventional salt-bath method of nitriding.

• Journal of Korean Institute of Industrial Engineers
• /
• v.40 no.3
• /
• pp.333-341
• /
• 2014

The purpose of this study is to forecast the penetration rate of renewable energy and a reasonable scale for the R&D investment plan in Korea based on the relationship between the diffusion and R&D investments drawn by analogy from empirical cases of advanced countries. Among numerous candidate developed countries, the German market was chosen based on the similarity of the diffusion patterns to those of the Korean plan. We then figured out how the investment triggers the growth of technology from the selected benchmark, and applied the technology S-curve relation formula to derive the desirable investment plan for Korea. The present paper is a pioneering attempt to forecast the diffusion process of renewable energy technology in Korea using the comparative analogy from cases of advanced countries.

• Journal of the Korean Society of Industry Convergence
• /
• v.22 no.6
• /
• pp.767-773
• /
• 2019

The thermal diffusion performance of the electronic device is a factor for evaluating the stability of the electronic device. Therefore, many of research have been conducted to improve the thermal characteristics of thermal interface materials, which are materials for thermal diffusion of electronic products. In this study, nano thermal grease was prepared by blending graphene, silver and copper nano powders into a thermal grease, a type of thermal interface materials, and the heat transfer rate was measured and compared for the purpose of investigating the improved thermal properties. As a result, the thermal properties were good in the order of graphene, silver and copper, which is thought to be due to the different thermal properties of the nano powder itself.

• Journal of Environmental Health Sciences
• /
• v.30 no.5 s.81
• /
• pp.395-401
• /
• 2004

In this study, lots of methods have been studing to utilize energy and decrease contaminated effluents. There has been great progress on IGCC (Integrated gasification combined cycle) to reduce thermal energy losses. The following results have been conducted from desulfurization experiments using waste shell to remove $H_{2}S$. Unreacted core model ior desulfuriration rate prediction of sorbent was indicated. These were linear relationship between time and conversion. So co-current diffusion resistance was conducted reaction rate controlling step. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. Maximum desulfurization capacity was observed at 0.631 mm for lime, oyster and hard-shelled mussel. The kinetics of the sorption of $H_{2}S$ by CaO is sensitive to the reaction temperature and particle size at $800^{\circ}C$, and the reaction rate of oyster was faster than the calcined limestone at $700^{\circ}C$.

• Korean Journal of Metals and Materials
• /
• v.48 no.8
• /
• pp.691-698
• /
• 2010

A study has been carried out to evaluate the interaction behavior between a lanthanide element and clad material in order to analyze the effect of the lanthanide element on the fuel cladding chemical interaction (FCCI). A diffusion couple test between Misch metal (70Ce-30La) and ferritic-martensitic steel (Gr.92) was performed at $660^{\circ}C$, followed by a microstructural analysis of the coupled sample. The results showed that Ce in the Misch metal, rather than La, reacted with the ferritic-martensitic steel (FMS) to form an interaction layer that penetrated the clad thickness. Fe diffused outside the clad interface to form an $Fe_2Ce$ compound, leaving a depletion of Fe caused by excess diffusion as well as by the formation of Cr-rich precipitation inside the interaction layer. The rate of growth followed the cubic rate law, which indicated that Fe depletion was caused by the diffusion of Fe and that the associated Cr-rich phase formation controlled the whole diffusion process.

• Journal of the Korean Chemical Society
• /
• v.7 no.3
• /
• pp.203-206
• /
• 1963

The eddy diffusion in the pulsed wetted wall column, where the spherical balls are consecutively arrayed along the axis of the column and turbulence is caused around the balls by pulsation, has been studied both theoretically and experimentally. A diffusion equation is solved for a longitudinal column where a concentration impulse is given at the top of the column, and the experimental results, which are the impulse response measurements at the half of the total height of the column, have shown a good agreement with the developed theory. A method of measuring the eddy diffusivity, which is based on the slope of concentration vs. time in the particular interval of concentration, is proposed and the measured diffusivity is used as a criterion of comparing the theory and the experiment. The eddy diffusion is remarkably increased as the amplitude and the frequency of the pulsation increase but the increasing rate is decreased as the pulsation increases.

• Korean Chemical Engineering Research
• /
• v.52 no.1
• /
• pp.133-140
• /
• 2014

The experiment was designed to compare the char combustion kinetics of pulverized Indonesia coals commonly utilized in Korea power plants. The reaction rate of coal char has been formulated using the external and internal effectiveness factors to describe the diffusion effect quantitatively. The Random Pore Model (RPM) was used for applying internal specific surface area as a function of carbon conversion ratio. Reaction rate was obtained from reaction time using the Wire Heating Reactor (WHR) which can heat and measure the char particle temperature at the same time. BET and TGA were used to obtain physical properties such as internal specific surface area and structural parameter. Three kinds of Indonesia Sub-bituminous coals "BARAMULTI, ENERGYMAN, AGM" were used in order to derive the activation energy and pre-exponential factor. The results of this study showed that the effect of internal diffusion than that of external diffusion is the dominant as comparison of kinetics was reflected in external and internal effectiveness factors. For three kinds of coal char, finally, activation energy of intrinsic kinetics indicates 110~118 kJ/mol.

• Food Science and Biotechnology
• /
• v.18 no.1
• /
• pp.202-206
• /
• 2009

Drying characteristics of fresh Korean-type rehmannia (jiwhang) noodle was investigated to determine drying kinetic parameters under the experimental conditions of 5 temperatures (30, 40, 60, 80, and $90^{\circ}C$). Drying curve of the noodle showed a biphasic pattern of decrease in drying rate with initial rapid drying followed by slow dehydration as the progress in drying. In all drying conditions, only falling drying rate period was observed and the drying rate of the noodle was greatly influenced by the drying temperature. The effective diffusion coefficients ($D_{eff}$) were determined by the diffusion model and their temperature dependency was determined using an Arrhenius equation. The activation energy ($E_a$) values for the drying of the noodle were 19.94 and 21.09 kJ/mol at the initial and the latter stage of dehydration, which were comparable to those of pasta or Japanese udong dehydration.