• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.219-224
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• 2004

The present study was to investigate the heat transfer enhancement effect of coil wire fins in an ice storage system. For the two cases of tubes with internal brine flows, a finned tube with coil wires on its outer surface and a smooth tube, the rates of ice layer were tested and compared for both the icing processes. The coil fins were made of a stainless steel wire with a dia. of 2.0(mm), and the coil had an outer dia. of 10(mm) and a helix angle of 60($^{\circ}$). The experimental results showed that the coil fins could substantially reduce the thermal resistance of the ice layer, and enhance the heat flow rates between the water in the storage tank and the brine. The ice storing time was found to be shortened by 13(%) for the coil fins to get the same amount of ice layer that was built on the smooth tube wall for 10 hours of operation when the same thermal conditions were provided.

• Journal of the Korean Society of Visualization
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• v.20 no.1
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• pp.38-44
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• 2022

An interscale transport of the turbulent kinetic energy (TKE) and Reynolds shear stress (RSS) is examined in an adverse pressure gradient (APG) turbulent boundary layer (TBL). The direct numerical simulation data of an APG TBL at Re_τ = 834 and β = 1.45 is employed. The TKE and RSS transport equations are divided into large and small scales, leading to the introduction of interscale transport. The TKE mainly transfers from large scales to small ones in the outer region, and vice versa for the RSS. An interscale transport of TKE and inverse interscale transport of RSS are amplified by APG, and the latter results in the increase in large scales of TKE production. Some of outer large scales of enhanced TKE transfer to small scales and then dissipate by viscosity, and the remains dissipate turbulent-non-turbulent interfaces by turbulent transport.

• Journal of the Korean institute of surface engineering
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• v.54 no.1
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• pp.30-36
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• 2021

In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

• Journal of Korea Foundry Society
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• v.13 no.1
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• pp.42-49
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• 1993

Conventional manufacturing process for cast iron-babbitt metal composite is complicate and bimetallic bonding by centrifugal casting is also difficult because their melting point is largely different and nonmetallic inclusion exists on outer shell. This study is aiming to simplify multistage process by adding Cu-powder as insert metals during cast iron solidification. The variables on fabrication of composite pipe are mold rotating speed and inner surface temperature of outer metal. The optimum temperature range for fusion bonding between cast iron and Cu-layer was $1100^{\circ}C-1140^{\circ}C$ in case of mold rotating speed was 700rpm. When the inner surface of Cu-layer was at $900^{\circ}C$, the value of interfacial hardness between Cu-layer and babbitt metal were higher than Cu-matrix by forming diffusion layer, interfacial products between Cu-layer and babbitt metal are proved to be $Cu_6Sn_5({\eta})$by XRD.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2577-2583
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• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.1
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• pp.74-82
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• 2011

The bast fiber of Paper mulberry has been generally used as a fibrous raw material in traditional Hanji-making. Nowadays, its uses is expanded to different special purposes such as paper mulberry yarn, laminated paper, antimicrobial paper depending on its application. Despite the wide array of the use of mulberry fibers, it is still limited due to some difficulties in the automation process of manufacturing works. This study is focused on the analysis of chemical components and morphological properties of paper mulberry bark for the automation of bark peeling process. The bast tissue of paper mulberry was separated in three plies; black outer layer, green inner layer, and white inner layer. The total lignin content, holocelluloses, extractives and ashes, and the anatomical structure of the three layers in mulberry bark tissue were investigated. The analysis showed that the black outer layer is composed of about 50% of total lignin content, whereas the white inner layer is composed of about 90% of holocellulose content.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.153-160
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• 2011

The AISI 216L stainless steel with a composition of Fe-16Cr-6Ni-6Mn-1.7Mo (wt.%) was oxidized at $700{\sim}900^{\circ}C$ in air for 100 h. At $700^{\circ}C$, a thin $Mn_{1.5}Cr_{1.5}O_4$ oxide layer with a thickness of $0.4{\mu}m$ formed. At $800^{\circ}C$, an outer thin $Fe_2O_3$ oxide layer and a thick inner $FeCr_2O_4$ oxide layer with a total thickness of $30{\mu}m$ formed. The non-adherent scale formed at $800^{\circ}C$ was susceptible to cracking. At $900^{\circ}C$, an outer thin $Fe_2O_3$ oxide layer and a thick inner $Mn_{1.5}Cr_{1.5}O_4$ oxide layer formed, whose total thickness was $10{\sim}15{\mu}m$. The scales formed at $900^{\circ}C$ were non-adherent and susceptible to cracking. 216 L stainless steel oxidized faster than 316 L stainless steel, owing to the increment of the Mn content and the decrement of Ni content.

• Korean Journal of Ichthyology
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• v.19 no.1
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• pp.16-23
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• 2007

Oocyte surface in two Korean minnows, Rhynchocypris oxycephalus and R. kumgangensis was examined by light and electron microscope. In two species, the development of the oocyte was similar, but the follicular layer surrounding full-grown oocyte showed an evident difference. In R. oxycephalus, the follicular layer at the yolk vesicle stage became bilaminar with the retention of its outer squamous cell layer and the acquisition of an inner cuboidal or round cell layer just over the zona radiata. As the oocyte grows, the cuboidal cells of the inner follicular layer began to be replaced by columnar cells. At the yolk granule stage, the columnar cells secreted mucin to their cytoplasm (adhesive materials) and then surround the entire oocyte, as bundles of fence-shaped structures. Whereas, although the follicular layer of R. kumgangensis had an outer squamous layer and an inner cuboidal or round cell layer at the yolk vesicles as in R. oxycephalus, no inner cells were more changed with the retention of its cuboidal or round cells. Finally, in R. kumgangensis, the adhesive materials did not occur. In Korean two minnows, the structural difference in the oocyte surface seems to be related to their habitats and spawning characteristics as well as taxonomic characters.

• The Journal of the Convergence on Culture Technology
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• v.5 no.1
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• pp.341-346
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• 2019

The study aims to provide a study on the mixing ratios and manufacturing methods of biodegradable PLA sheets for mid - term introduction, A 3-layer process was introduced to produce a multifunctional multi-layer structure sheet having improved heat resistance, impact resistance and transparency while having anti-fogging functionality as a biodegradable PLA sheet used for the purpose of anti-fogging function. Inner layer, core layer and outer layer were mixed and extruded. The inner layer and core layer were studied for a biodegradable PLA multi-layer sheet structure having inner hardness and high heat resistance and outer layer for imparting antifogging function. By applying the results of this study, plastic PLA properties and heat-resistant temperature can be improved to replace and expand plastics.

• Research in Plant Disease
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• v.14 no.3
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• pp.176-181
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• 2008

This experiment was conducted to find the causes of ineffective seed disinfection methods such as rice seeds soaking in hot water and prochloraz EC solution when the rice seeds were severely infected by Bakanae disease. In case of rice seeds collected from severely diseased field by Bakanae disease, the pathogen as the forms of spores and mycelium were infected in plumule and inner and outer integument of embryo, aleurone layer, and pericarp layer. When the rice seeds were soaked in hot water, the appearances of spores and hypha on the outer pericarp layer were severely disordered, however those of inner region of outer integument and aleurone layer were shown normal. The membrane of hypha on the outer pericarp layer was destroyed within 24 hours, while some spores were healthy and germinated 7 days after soaking, when the rice seeds soaked 24 hours in 125 ppm prochloraz solution at $30^{\circ}C$. These results indicated that the seed disinfection methods were ineffective on the Bakanae disease severely infected rice seed because the hot water did not transmit the pericarp layer of rice seed and also prochloraz solution did not effectively destroy the spore of pathogen.