• The Journal of the Korean Society for Microbiology
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• v.35 no.1
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• pp.41-48
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• 2000

Bacteroides fragilis and Escherichia coli, normal colonic inhabitants, are the most frequently isolated bacteria in infected tissues, particularly in intraabdominal abscesses. This study was designed to determine whether enteric bacteria may alter the B. fragilis-induced expression of pro inflammatory cytokines in mouse peritoneal tissue (MPT). After C57BL/6 mice were inoculated with abscess-forming mixture containing B. fragilis in the presence or absence of E. coli, RNA was extracted from MPT. Expression of interleukin (IL)-$1{\alpha}$ and tumor necrosis factor $(TNF){\alpha}$ mRNA was assessed using RT-PCR and standard RNA. Each cytokine protein was also measured by ELISA. The co-inoculation of E. coli into mouse peritoneal cavity advanced the onset of abscess development by B. fragilis infection. When mouse was co-infected with E. coli and B. fragilis intraperitoneally, there was a synergistic increase in the expression of IL-$1{\alpha}$ and $TNF{\alpha}$ mRNA in MPT and this was paralleled by increased cytokine protein secretion. Mixed inoculation of heat-killed E. coli and B. fragilis did not cause a synergistic increase in those cytokine mRNA expression. These results suggest that enteric bacteria may significantly affect proinflammatory cytokine signal produced by host peritoneal cavity in response to B. fragilis infection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.98-103
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• 2018

Many coating technologies have been developed so far to improve the corrosion resistance, strength, abrasion resistance and other surface properties of materials and equipment. Among them, the formation of CCO (CaCoO, then CCO) thin films has been studied and used in the electronic material field. One of the characteristics of CCO thin films is that it is resistant to high temperature heat. Particularly, the method of forming the CCO thin film is relatively simple, and it was judged that it could be introduced into the existing equipment. Therefore, in this study, an experiment and analysis were carried out to determine whether the coating of CCO thin films can be applied to hot dip galvanizing facilities. A CCO thin film was formed on the surface of STS304 base material and oxidized in a Zn fume atmosphere in a $650^{\circ}C$ furnace with an air atmosphere. Oxidation was carried out for 30 days, after which the shape of the CCO thin film was confirmed by SEM and its corrosivity was analyzed through a potentiodynamic polarization experiment.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.74-81
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• 2013

A numerical design analysis is conducted to search for an optimal shape of outlet in a rotating-disk CVD reactor. The goal is to suppress flow recirculation that has been found in a reactor having a sudden expansion of flow passage outside of the rotating disk. In order to streamline gas flow, the sidewall at which the flow in the Ekman layer is impinged, is tilted. The axisymmetric laminar flow and heat transfer in the reactor are simulated using the incompressible ideal gas model. For the conventional vertical sidewall, the flow recirculation forming in the corner region could be expanded into the interior to distort the upstream flow. The numerical results show that this unfavorable phenomenon inducing back flow could be dramatically suppressed by tilting the sidewall at a certain range of angle. The assessment of deviation in deposition rate based on the characteristic isotherm illustrates that the sidewall tilting may expand the domain of stable plug-like flow regime toward higher pressure. A physical interpretation is attempted to explain the mechanism to suppress flow recirculation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.1-7
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• 2016

A range of techniques have been being developed to remove the volatile organic compounds from paining processes. High temperature decomposition of harmful VOCs using arc plasma has recently been proposed, and this work analyzed the extreme hot process by computer-aided fluid dynamics prior to the reactor design. Numerical simulations utilized the conservation equations of mass and momentum. The simulation showed that the fluid flowed down along the inner surface of the centrifugal reactor by forming intensive spiral trajectories. Although the high temperature gas generated by plasma influences the bottom of the reactor, no heat transfer in radial direction appeared. The decomposition efficiency of a typical VOCs, toluene, was found to be a maximum of 67% across the reactor, which was similar to the value (approximately 70%) for the lab-scale test.

• Journal of Powder Materials
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• v.22 no.4
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• pp.266-270
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• 2015

The synthesis of NiTi alloy powders by hydrogen reduction and dehydrogenation process of NiO and $TiH_2$ powder mixtures is investigated. Mixtures of NiO and $TiH_2$ powders are prepared by simple mixing for 1 h or ball milling for 24 h. Simple-mixed mixture shows that fine NiO particles are homogeneously coated on the surface of $TiH_2$ powders, whereas ball milled one exhibits the morphology with mixing of fine NiO and $TiH_2$ particles. Thermogravimetric analysis in hydrogen atmosphere reveals that the NiO and $TiH_2$ phase are changed to metallic Ni and Ti in the temperature range of 260 to $290^{\circ}C$ and 553 to $639^{\circ}C$, respectively. In the simple-mixed powders by heat-up to $700^{\circ}C$, agglomerates with solid particles and solidified liquid phase are observed, and the size of agglomerates is increased at $1000^{\circ}C$. From the XRD analysis, the presence of liquid phase is explained by the formation and melting of $NiTi_2$ inter-metallic compound due to an exothermic reaction between Ni and Ti. The simple-mixed powders, heated to $1000^{\circ}C$, lead to the formation of NiTi phase but additional Ni-, Ti-rich and Ti-oxide phases. In contrast, the microstructure of ball-milled powders is characterized by the neck-grown particles, forming $Ni_3Ti$, Ti-oxide and unreacted Ni phase.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.436-441
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• 2000

Plasma nitrocarburising is a thermochemical heat treatment, and can be used for plain carbon steels and low alloy steels to improve wear, corrosion and fatigue resistance. The process is performed on automotive parts, machinery parts and engineering tools. However, it is still facing problems in obtaining a mono $\varepsilon$ phased compound layer. Therefore, the aim of this research is to investigate the possibility of forming a mono $\varepsilon$ phased compound layer using a gas mixture of nitrogen and methane. It was found that high nitrogen contents were essential for the production of $\varepsilon$ phase compound layer and with increasing methane content in the gas mixture, $\varepsilon$ phase compound layer was favoured. In addition, when the methane content was further increased, cementite was observed in the compound layer. $\gamma$' phase was produced after 10 minutes treatment time and cementite was formed in the compound layer resulting in decreasing the thickness of the compound layer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1675-1682
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• 2012

Weight reduction is increasingly being considered very important in light of air pollution and the exhaustion of resources. As a result, many automotive components are being replaced by Al and Mg alloys, and studies are increasingly focusing on the same. However, the use of Mg alloys is limited because they have higher material cost and lower productivity owing to the difficult forming conditions compared with Al alloys. In this study, the tube extrusion process conditions of an automotive bumper back beam were analyzed using FEA. Material tests were performed to determine the properties, and experiments and analyses for a simple shape were performed to define the data for heat generation during plastic deformation. Then, the analyses of the product were carried out by considering various temperatures and ram speeds. The conditions were then established, and a product without surface defects was extruded successfully.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.602-606
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• 2015

Porous W with spherical and directionally aligned pores was fabricated by the combination of sacrificial fugitives and a freeze-drying process. Camphene slurries with powder mixtures of $WO_3$ and spherical PMMA of 20 vol% were frozen at $-25^{\circ}C$ and dried for the sublimation of the camphene. The green bodies were heat-treated at $400^{\circ}C$ for 2 h to decompose the PMMA; then, sintering was carried out at $1200^{\circ}C$ in a hydrogen atmosphere for 2 h. TGA and XRD analysis showed that the PMMA decomposed at about $400^{\circ}C$, and $WO_3$ was reduced to metallic W at $800^{\circ}C$ without any reaction phases. The sintered bodies with $WO_3$-PMMA contents of 15 and 20 vol% showed large pores with aligned direction and small pores in the internal walls of the large pores. The pore formation was discussed in terms of the solidication behavior of liquid camphene with solid particles. Spherical pores, formed by decomposition of PMMA, were observed in the sintered specimens. Also, microstructural observation revealed that struts between the small pores consisted of very fine particles with size of about 300 nm.

• Journal of Powder Materials
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• v.24 no.5
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• pp.384-388
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• 2017

The effect of the mixing method on the characteristics of hybrid-structure W powder with nano and micro sizes is investigated. Fine $WO_3$ powders with sizes of ${\sim}0.6{\mu}m$, prepared by ball milling for 10 h, are mixed with pure W powder with sizes of $12{\mu}m$ by various mixing process. In the case of simple mixing with ball-milled $WO_3$ and micro sized W powders, $WO_3$ particles are locally present in the form of agglomerates in the surface of large W powders, but in the case of ball milling, a relatively uniform distribution of $WO_3$ particles is exhibited. The microstructural observation reveals that the ball milled $WO_3$ powder, heat-treated at $750^{\circ}C$ for 1 h in a hydrogen atmosphere, is fine W particles of ~200 nm or less. The powder mixture prepared by simple mixing and hydrogen reduction exhibits the formation of coarse W particles with agglomeration of the micro sized W powder on the surface. Conversely, in the powder mixture fabricated by ball milling and hydrogen reduction, a uniform distribution of fine W particles forming nano-micro sized hybrid structure is observed.

• Korean Journal of Food Science and Technology
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• v.43 no.3
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• pp.321-328
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• 2011

Edible films were developed from jujube (Zizyphus jujube Miller) using depolymerization processes of ultrasound and high-pressure homogenization. A 4.6% (w/w) jujube hydrocolloid was treated by ultrasound (600W, 20 min) or homogenized at high pressure (172 MPa, 6 s) and mixed with whey protein isolate, glycerol, xanthan, and sucrose esters of fatty acids to form film-forming solutions from which films were formed by drying. The film prepared by highpressure homogenization (HPH film) produced more homogeneous films without particles than those prepared without depolymerization or with the ultrasound treatment. HPH films possessed the highest tensile strength (4.7MPa), the lowest water vapor permeability ($2.9g{\cdot}mm/kPa{\cdot}h{\cdot}m^2$), and the most uniform and dense microstructures among the films. Flavor profiles of jujube powder and the films were distinguishable. Heat seal strength and oxygen permeability of the HPH films were 44.4 N/m and $0.025mL{\cdot}{\mu}m/m^2$/day/Pa, respectively. Antioxidant activities of jujube power and HPH films were not significantly different.