• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.16-23
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• 2022

In this study, characteristics of effect on hydrogen gas was investigated to hydrogen embrittlement by disk and tensile tests. The developed and commercial alloy was fabricated to a plate material made from an alloy ingot. The prepared materials were processed in the form of a disk to measure rupture pressure by hydrogen and helium gas at a rate of 0.1 to 1,000 bar/min. In the hydrogen pre-charged tensile test, a specimen was hydrogenated using an anode charging method, and the yield strength, ultimate tensile strength, elongation, and reduction in area rate were carried by a strain rate test. Also, the microstructure was observed to the fracture surface of the tensile test specimen. As a result, the developed materials satisfied endurable hydrogen embrittlement, and the fractured surface showed a brittleness fracture surface with a depth of several ㎛, but dimple due to ductile fracture could be observed.

• Journal of the Korean Society of School Health
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• v.8 no.2
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• pp.293-303
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• 1995

Health has occupied a position of importance in the human history, whether it be in the East or in the West, and it is a subject in which people have been constantly interested. The concept of health has changed continuously as the society has developed, industrialized and become more structured. The perception of health concept can be an esential factor which is to determine the health behaviors. This study is a descriptive inquiry done to identity high school students' perception of health and what they do as health behaviors. The subject consisted of 503 voctional high school seniors, 129 boys and 374 girls, from a school located in An-san Si, kyong-gi Do. The instruments used for this study were open-ended questionnaires and data were collected by having the students fill out the questionnaires which took 10 minutes, in their first class, April 6, 1995. The collected materials were classified and recorded on the cards according to each question using the terms which students had written. After putting statements which had common meanings together, the representative categories were labelled. The results obtained are as follows. 1. Categorizing and labelling of health concepts What high school students descripted as health concepts were classified as the absence of illness, physical comfort, strong physical strength and physique, not having a deformity, resisting power, self control mental-rest(or psychological comfort), wholesome ideas, self-control, harmony in body and in mind, maintenace of daily life, pleasant life, good friends, peaceful family life and realizing objectives. 2. Categorizing and labelling of health behaviors These were classified as preventive life, good dietary habits and regimen, maintenance of clean body, exercises, preventing obesity, rest, environmental balance or control of environment, limit one's tastes, making use of leisure, peaceful mind, sound thought and regular living habits. The result indicates that the health concepts were positive and included not only absence of illness but also harmony in body and in mind and pleasant life; health behaviors which had high frequency were good dietary habits and regimen, exercises and sound thought. It is hoped that these findings well serve as practical references for teachers when they counsel with, and provide the students with guidance programs which include health care.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1303-1305
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• 1998

In order to reduce or avoid oxidation problem at operation the interconnects in SOFCs have so far mostly been made of ceramic material. It has high chemical stability both under cathode and anode condition, relatively thermal expansion coefficient that matchs that of electrolyte material YSZ. But this material shown rather weak in the low oxygen atmosphere and thermal shock, and it has lower mechanical strength than alloys. To avoid these problems one may consider to use metals or alloys as materials for interconnects. Metallic interconnects are advantageous because of their high thermal and electronic conductivities. But it has some problems, Those are high thermal expansion and oxidation at high temperature in air. To solve these problems in the interconnection material in this study, $LaCrO_3$-dispersed Cr alloys for metallic interconnector of SOFC have been investigated as a fuction of $LaCrO_3$ content in the range of 5 to 25 vol.%. The Cr alloy were prepared by mixing Cr and $LaCrO_3$ powders in high-energy ball mill for 48h and by sintering under Ar atmosphere with 5vol.% $H_2$ for 10h at $1500^{\circ}C$. The alloys had a relative density of 95% and above. The Cr alloys in composed of two kind of small $LaCrO_3$ and large Cr particles. As the $LaCrO_3$ content increased, the Cr particle size decreased but the $LaCrO_3$ particle size remained contant. Also the oxidation tests show that the $LaCrO_3$-dispersed Cr is very resistant to oxidation in air. These results means that $LaCrO_3$-dispersed Cr is a useful material for metallic interconnect of planar SOFC.

• Journal of Korean Foot and Ankle Society
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• v.13 no.1
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• pp.80-84
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• 2009

Purpose: The purpose of this article is to assess the efficacy of a bioabsorbable polylactide (PLA) plate and screw for treating injuries of ankle fractures. Materials and Methods: 24 patients who underwent an open reduction and internal fixation operation for ankle fractures from July 2005 to March 2007 were enrolled into the study. There were 15 men and 9 women. The average age of the patients was 44 years and the average follow-up period was 16 years and two months (16.2 months). All cases were divided into low grade fracture patient (11) who belongs in type A and B of Danis-Weber classification and high grade fracture patient (13) who belongs in type C1, C2 of Danis-Weber classification, and each groups were analyzed by clinical (Meyer score) and radiological finding at the time of their last follow-up evaluation. Results: The clinical results according to Meyer scoring system, showed that all patient with low grade fracture had good to excellent result, but only 54% of patient with high grade fracture had good to excellent result. According to Cedell's radiologic finding, there were 91% cases above fair in low grade fracture. But there were 62% of patient above fair result in high grade fracture, the reduction losses were seen in 38% of patient with high grade fracture. Conclusion: Bioabsorbable PLA plate and screw is good internal fixation device which doesn't have additional operation for removal of implant because of slow absorption within the human body. It showed sufficient strength for acquisition and maintenance of reduction in low grade fracture, but need attention to use because of many cases of reduction loss in high grade fracture. So, it seems to be safe and effective when used in heeling of low grade fracture under considering about type of fracture sufficiently.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.29-35
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• 2013

A dense mixed ionic and electronic conducting ceramic membrane is one of the most promising materials because it can be used for separation of oxygen from the mixture gas. The $ABO_3$ perovskite structure shows high chemical stability at high temperatures under reduction and oxidation atmospheres. $BaCo_{1-x-y}Fe_xZr_yO_{3-{\delta}}$ (BCFZ) was well-known material as high mechanical strength, low thermal conductivity and stability in the high valence state. Glycine Nitrate Process (GNP) is rapid and effective method for powder synthesis using glycine as a fuel and show higher product crystallinity compared to solid state reaction and citrate-EDTA method. BCFZ was fabricated by modified glycine nitrate process. In order to control the burn-up reaction, $NH_4NO_3$ was used as extra nitrate. According to X-Ray Diffraction (XRD) results, BCFZ was single phase regardless of Zr dopants from y=0.1 to 0.3 on B sites. The green compacts were sintered at $1200^{\circ}C$ for 2 hours. Oxygen permeability, methane partial oxidation rate and hydrogen production ability of the membranes were characterized by using Micro Gas Chromatography (Micro GC) under various condition. The high oxygen permeation flux of BCFZ 1-451 was about $1ml{\cdot}cm^{-2}s^{-1}$. Using the humidified Argon gas, BCFZ 1-433 produced hydrogen about $1ml{\cdot}cm^{-2}s^{-1}$.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.559-567
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• 2005

The objective of this study is to optimize the use of mineral admixtures (silica fume, fly ash, and blast furnace slag) in high-performance concrete for bridge deck overlay. For this purpose, high-performance concrete, incorporating mineral admixtures, was tested for compressive strength and permeability. The Box Behnken design was used to determine the optimum mix proportions of the mineral admixtures. The optimized mix compositions were then technically evaluated. Test results are compare with the performance specification for high performance concrete overlay on bridge deck. The optimum mix proportions were shown to possess acceptable properties. Also, it is possible to save the construction and materials costs result from a reduction In actual material cost and from the use of widely avaliable truck mixers instead of mobile mixers.

• Korean Journal of Construction Engineering and Management
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• v.15 no.4
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• pp.49-57
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• 2014

Since the structure systems of construction projects have been forced to be large, high-rised, and complex, many researchers have been put their efforts to develop high strength concrete incorporating diverse advanced materials. In order to improve the performance of the concrete, the fibers leading high ductility to concrete have been used, consequently concrete columns adopting High-Performance Fiber Cement(HPFC) have been developed. This paper analyzed not only the construction work process of HPFC column installed to the real construction project, but also construction productivity of the columns by using discrete event simulation technique. As a result, several considerations on installing such a column have identified, compared with the works for typical concrete columns. In particular, there was specific characteristic to install the columns in terms of labor resource productivity, which is not shown with the work for the typical concrete columns.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.535-544
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• 2021

When baking, the proper blending or mixing of materials will affect the quality of the product. The mixing strength is important when establishing the optimal conditions for batter, and control of the mixing condition is accordingly an important factor. This study investigated the effects of the mixing speed and time on the quality characteristics of a gluten-free type of rice batter. The batter samples manufactured for this purpose are as follows: control (+) (wheat flour), control (-) (rice flour), T1 (1,800 rpm, 1 min), T2 (1,800 rpm, 2 min), T3 (1,800 rpm, 3 min), T4 (3,600 rpm, 1 min), T5 (3,600 rpm, 2 min), T6 (3,600 rpm, 3 min). In this study, rice flour was used in the T1 to T6 samples. The pH of the batter tended to be higher when the mixing speed was slower and the time was shorter depending on the ultra-high mixing conditions. The moisture content of T3 was highest, and there was no difference according to the ultra-high speed conditions. The specific volumes of the ultra-high mixing treatments were higher than those of the control samples. The relationship between the specific volume, hardness and springiness of rice bread according to the mixing speed and time was weak. Therefore, it is considered that the application of ultra-high speeds when manufacturing gluten-free batter can have a positive effect on improving the production efficiency by reducing the processing time.

• Journal of Surface Science and Engineering
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• v.57 no.5
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• pp.386-397
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• 2024

Chrome plating is a method used to protect the inside of a gun barrel from the severe environment (3,000 K and 4,000 MPa for 20 ms) created by the propellant gas when a cannon is fired. However, Cr-plated films have physical limitations, and the formation of hexavalent Cr compounds has a harmful effect on the environment. Ta-W alloy film has been explored as an alternative to Cr plating owing to the high melting point and corrosion resistance of Ta. However, obtaining pure α-phase Ta by sputtering is difficult, and the autofrettage effect in gun barrels limits the use of annealing. Therefore, a deposition method without the use of additional heat treatment is required to prepare Ta-W films with alpha-phase Ta. We explored the feasibility of depositing Ta-W alloy film inside a 2,800 mm-long stainless-steel tube using bipolar high-power impulse magnetron sputtering. A specially designed cylindrical magnetron sputtering equipment and a four-stage experimental process was employed to deposit a coating with uniform thickness (10.59%) throughout the tube, high adhesive strength (51.51 MPa), and pure alpha-phase Ta. The findings of this study are useful for deposition of Ta-W alloy films inside large-caliber canons.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.3
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• pp.249-257
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• 2007

State of problem : The use of zirconium oxide all-ceramic material provides several advantages, including a high flexural strength(>1000MPa) and desirable optical properties, such as shading adaptation to the basic shades and a reduction in the layer thickness. Along with the strength of the materials, the cementation technique is also important to the clinical success of a restoration. Nevertheless, little information is available on the effect of different surface treatments on the bonding of zirconium high-crystalline ceramics and resin luting agents. Purpose : The aim of this study was to test the effects of surface treatments of zirconium on shear bond strengths between bovine teeth and a zirconia ceramic and evaluate differences among cements Material and methods : 54 sound bovine teeth extracted within a 1 months, were used. They were frozen in distilled water. These were rinsed by tap water to confirm that no granulation tissues have left. These were kept refrigerated at $4^{\circ}C$ until tested. Each tooth was placed horizontally at a plastic cylinder (diameter 20mm), and embedded in epoxy resin. Teeth were sectioned with diamond burs to expose dentin and grinded with #600 silicon carbide paper. To make sure there was no enamel left, each was observed under an optical microscope. 54 prefabricated zirconium oxide ceramic copings(Lava, 3M ESPE, USA) were assigned into 3 groups ; control, airborne-abraded with $110{\mu}m$ $Al_2O_3$ and scratched with diamond burs at 4 directions. They were cemented with a seating force of 10 ㎏ per tooth, using resin luting cement(Panavia $F^{(R)}$), resin cement(Superbond $C&B^{(R)}$), and resin modified GI cement(Rely X $Luting^{(R)}$). Those were thermocycled at $5^{\circ}C$ and $55^{\circ}C$ for 5000 cycles with a 30 second dwell time, and then shear bond strength was determined in a universal test machine(Model 4200, Instron Co., Canton, USA). The crosshead speed was 1 mm/min. The result was analyzed with one-way analysis of variance(ANOVA) and the Tukey test at a significance level of P<0.05. Results : Superbond $C&B^{(R)}$ at scratching with diamond burs showed the highest shear bond strength than others (p<.05). For Panavia $F^{(R)}$, groups of scratching and sandblasting showed significantly higher shear bond strength than control group(p<.05). For Rely X $Luting^{(R)}$, only between scratching & control group, significantly different shear bond strength was observed(p<.05). Conclusion : Within the limitation of this study, Superbond $C&B^{(R)}$ showed clinically acceptable shear bond between bovine teeth & zirconia ceramics regardless of surface treatments. For the surface treatment, scratching increased shear bond strength. Increase of shear bond strength by sandblasting with $110{\mu}m$ $Al_2O_3$ was not statistically different.