• Journal of Powder Materials
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• v.12 no.3
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• pp.225-230
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• 2005

In order to prevent the oxide formation on the surface of nano-size iron particles and thereby to improve the oxidation resistance, iron nanoparticles synthesized by a chemical vapor condensation method were directly soaked in hexadecanethiol solution to coat them with a polymer layer. Oxygen content in the polymer-coated iron nanoparticles was significantly lower than that in air-passivated particles possessing iron-core/oxide-shell structure. Accordingly, oxidation resistance of the polymer-coated particles at an elevated temperature below $130^{\circ}C$ in air was $10\~40$ times higher than that of the air- passivated particles.

• Journal of the Korean institute of surface engineering
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• v.45 no.2
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• pp.61-69
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• 2012

Alloys of Fe-(5, 10, 15)Al and Fe-(10, 20, 30, 40)Cr were corroded at 700 and $800^{\circ}C$ for 70 hr in either atmospheric air or 1 atm of Ar+$1%SO_2$ gases. In these atmospheres, Fe-5Al and Fe-10Cr alloys displayed poor corrosion resistance. In atmospheric air, Fe-5Al alloys formed oxide nodules, while Fe-10Cr alloys formed thick scales and internal oxides. In Ar+$1%SO_2$ gases, Fe-5Al and Fe-10Cr alloys formed thick, nonadherent bi-layered scales, which grew primarily by the outward diffusion of Fe ions and inward diffusion of oxygen and sulfur ions. By contrast, in atmospheric air and Ar+$1%SO_2$ gases, Fe-(10, 15)Al and Fe-(20, 30, 40)Cr alloys displayed good corrosion resistance by forming $Al_2O_3$ and $Cr_2O_3$ layers on the surface, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.29-30
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• 2020

As the modern society enters, the building becomes sealed and the public's interest in the environment increases, so the interest in indoor air pollution increases and the environmental pollution is raised as an important issue not only outdoors but also indoors. In addition, the emergence of sick house syndrome (SHS) has increased the interest in formaldehyde and is a cause of deteriorating indoor air quality. Accordingly, this study prepared a functional paint by incorporating a photocatalyst in an aqueous paint, and conducted formaldehyde adsorption experiments and functional evaluation. As a result of the experiment, as the photocatalyst was added, the formaldehyde adsorption performance tended to increase. In addition, as a result of measuring the impact resistance and alkali resistance according to the KS standard, there is no difference in residual cracks and cracks between the water-based paint without the photocatalyst and the water-based paint with the photocatalyst added. Therefore, it is considered that the water-based paint added with a photocatalyst can improve the indoor air quality by adsorbing formaldehyde and can be used as a functional paint because the functionality is not different from that of a general water-based paint.

• Journal of Environmental Health Sciences
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• v.39 no.5
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• pp.447-455
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• 2013

Objectives: This study aims to understand the concentration, diversity, and antibiotic characteristics of staphylococci present in the indoor air of child-care facilities. Methods: Air sampling was performed from October 2012 to January 2013 in 120 child-care facilities in Seoul, Korea. Methicillin-resistant bacteria were selected from the total obtained airborne bacteria and subjected to 16S rRNA analysis for methicillin-resistant staphylococcal species determination. Identified staphylococcal strains were tested for resistance to a range of antibiotics. Results: Average total airborne bacterial concentration was $508.9{\pm}246.3CFU/m^3$. Indoor concentration of total airborne bacteria had a significant positive correlation with the $CO_2$ concentration in the child-care facilities. Methicillin-resistant staphylococci were present in 13.3% of the child-care facilities studied. A total of four species (S. epidermidis, S. cohnii, S. saprophyticus, S. sp.) and 55 strains were identified from the indoor air of the child-care facilities. Staphylococcus cohnii was the most common species (54.5%), followed by S. epidermidis (38.2%). All of the isolated staphylococcal strains exhibited high resistance to oxacillin, erythromycin, mupirocin, and ceftizoxime. Especially, S. saprophyticus strains showed more multidrug resistance to oxacillin, vancomycin, clindamycin, erythromycin, lincomycin, ceftizoxime, mupirocin, and tetracycline than did other species. Conclusion: The results of this study showed that a monitoring system for multidrug-resistant bacteria is needed in facilities for children, as the community-associated infections of these bacteria are increasing.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.74-78
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• 2002

Zinc Air battery obtain their energy density advantage over the other batteries by utilizing ambient oxygen as the cathode materials, and reusing cathode as recycled form. And specific capacity of zinc powder is as high as 820 mAh/g. However, if the pore size in cathode is small then the flow rate of air decreased, and as a result of that discharge voltage of batteries becomes low. We focused on resistance and porosity of cathode. So we studied the effects of conducting agents to zinc air batteries performance, capacity, power density, average discharge voltage, resistance. And we also measured porosity of cathode by the ASTM. So we have got optimum contents of conducting agent.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.4
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• pp.223-229
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• 2004

The effects of the cooling and annealing conditions on the microstructures and corrosion properties were investigated for the Cu-contained Zr-Nb alloy (Zr-1.1Nb-0.07Cu). After annealing at $1050^{\circ}C$ for 15 min, the specimens were cooled by three methods of water quenching, air cooling, and furnace cooling. Widmanstatten structures were developed in both air- and furnace-cooled specimens, and the Widmanstatten plate width of the furnace-cooled specimens was wider than that of the air-cooled ones. The weight gain in the furnace-cooling case was higher than that in the air-cooling case. This could be the reason why the diffusion time was more enough during the furnace cooling than the air cooling. The oxide of the furnace-cooled specimen was nonunformly formed just beneath the Widmanstatten plate boundaries, where ${\beta}_{Zr}$ phases were exised concentrately. Compared with the $640^{\circ}C$ annealing after the water quenching, the $570^{\circ}C$ annealing could make the ${\beta}_{Nb}$ phases and a concomitant reduction of the Nb in the matrix, and then it could improve the corrosion resistance with the increase of the annealing time. It would be concluded that the corrosion resistance of the Zr-1.1Nb-0.07Cu was good when the Nb concentration in the matrix was reached at an equilibrium level and then the ${\beta}_{Nb}$ phase was formed.

• Journal of the Korean Ceramic Society
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• v.47 no.3
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• pp.232-236
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• 2010

In recent years abrasive water jet (AWJ) has received significant attention as a technology used in the manufacturing industry for cutting materials. In this paper we report the development of a new preparation method of abrasives for water jet by using an air bubbling sedimentation rate control technique. The SiC abrasives prepared by an air bubbling sedimentation rate control technique using latex resin are found to be superior to the conventional abrasives not only in surface roughness uniformity but also in lifetime. The AWJ test results also show that the former has also better impact-resistance and wear-resistance than the latter.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.36-42
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• 2020

In this study, flow analyses of a vehicle at driving were carried out after each installation of a tuning part, specifically the bonnet air ducts, the rear spoiler, and the rear diffuser. The study models were designed to comprise a total of eight cases in which each of the three parts were mounted individually or all together in vehicles. Assuming that the vehicle were driven with an average high speed of 100 km/h, the speed and pressure around the vehicle were obtained using CFD when driving. The rear diffuser that becomes the most effective among the three mounting parts has a major role in reducing air resistance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.16-26
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• 2005

Air-cooled heat sinks are employed in many electronic cooling applications since they provide significant heat transfer enhancement and operational flexibility. Strip-shaped fin heat sink is of interest and needs to be investigated as general cooling products for more applicability. The purposes of this study are to evaluate heat sink performance without bypass flow condition and to determine optimal heat sink geometries. The results show that the decreasing rate of thermal resistance of a heat sink decreases with increasing inlet air velocity, and the increasing rate of pressure drop increases with increasing inlet air velocity, but is not affected by input power. The increasing rate of optimal longitudinal fin spacing is larger than that of transverse fin spacing. The strip fin heat sink tested in this study showed better cooling performance compared to that of other plate fin type.matism. 2004; 50(11): 3504-3515.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.117-120
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• 2004

Up to now, many researches have been performed md verified that many properties of concrete can be improved by using mineral admixtures such as blast furnace slag, silica fume, and expansive admixture. But it is not clear whether there is any need for entraining air to make a high strength concrete using expansive admixture and mineral admixtures to insure enough freeze-thaw resistance. this paper presents the strength and durability properties of high strength concrete using expasive admixtures and industrial by-products. It was observed from the test results that very high strength concrete$(W/B=20\%)$ is not needed to be air entrained and high strength concrete$(W/B=30\%)$ using expansive admixture and mineral admixtures is needed to be entrained $2\~4\%$ air.