• The Journal of Korean Academy of Prosthodontics
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• v.28 no.2
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• pp.29-51
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• 1990

This study was designed to compre the tensile bond strength of 4-META containging denture base resin to Co-Cr alloys after various surface treatments. Especially the surface treatment of sandblasting the mental with aluminum oxide and treating in oxidizing solution composed of 3% aqueous sulfuric acid with 1% potassium manganate were compared. Effect of surface roughness on bonding was measured after sandblasting with 50um, 300um aluminun oxide and polishing with emery pater. Also the effects of wax and wax solvent on bonding were observed. According to the type of polymerization process, heat-cured Meta-Dent resin and autopolymerizing Meta-Fast resin were used. For some specimnens, the tensile bond strength were measured agter three pre-conditions : 1day after bonding, immersed in water at $75^{\circ}C{\pm}3^{\circ}C$ for 4weeks, under normal ambient condition for 4weeks. The following results were obtained from this study : 1. The bond strengths of resins containing 4-META were significantly higher than those of conventional denture base resins(p<0.05). 2. Autopolymerizing Meta-Fast resin had higher bond strength than heat-cured Meta-Dent, resin(p<0.05). 3. The bond strengths of Biosil and Nobilium to 4-META containging resins were not significally different(p>0.05). 4. Stable adhesion can be achieved when mechanically roughen the metal surface by snadblasting with $50{\mu}m$ aluminum oxide than treating in an oxidizing soluing with potassium manganate(p<0.05). 5. Once the metal surface is contaminated with wax, the bond srtength decreased greatly in spite of wax wash with boiling water. But the bond strength recovered significantly with the use of wax solvent 6. Meta-Dent resin had higher bond strength when roughen the metal surface with $50{\mu}m$ aluminum oxide than with $300{\mu}m$ aluminum oxide(p<0.05). In case of Meta-Fast, resin, the use of $300{\mu}m$aluminum oxide was a little advantageous of bonding, but was statistically insignificant(p>0.05).

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.877-883
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• 2003

Multi-degradable master hatch (M/B) was prepared and 0.05 mm polyethylene (PP) food packaging films containing 0, 10, and 20% M/B were manufactured by inflation film processing. The films were exposed to UV radiation, fungi, and heat in order to observe their photolysis, biodegradability, and thermal degradability, respectively. While pure PP film maintained more than 70% of its original elongation after 8 weeks of UV radiation, an almost perfect loss in the elongation of PP film containing 20% M/B was observed. Significant decreases in elongation of PP films by heat treatment $(68{\pm}2^{\circ}C)$ were also found in samples containing the multi-degradable M/B. By observing changes in film surface after the inoculation of fungi using scanning electron microscopy (SEM), the biodegradability of plastic film could be accelerated with the addition of multi-degradable M/B. The results of the mulching test in yard showed that adding multi-degradable M/B can effectively degrade plastic films in natural environmental conditions without interrupting the growth of plants.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1063-1069
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• 1997

For me1t-spun Fe-Nd-C alloys, variation of phase development and magnetic properties with the variety of alloy compositions and production conditions were investigated. To find out whether hard magnetic $Fe_{14}Nd_2C$ is crystallized direct1y from the melt by rapid quenching, the phase development of the as-spun ribbons spun at various speed was a1so studied. For the ribbons spun at 10m/s, ${\alpha}-Fe$ was the primary crystallization phase followed by the secondary $Fe_{17}Nd_2C$. At 20m/s ${\alpha}-Fe$ was suppressed so that the primary $Fe_{17}Nd_2C$ coexisted with the secondary ${\alpha}-Fe$ and the amorphous phase. Above 30m/s the ribbons were a1most amorphous, and the amorphization was complete at 40m/s. $Fe_{14}Nd_2C$ therefore was not found in as-spun state but obtained after heat treating the ribbons. The effective temperature range ($700{\sim}900^{\circ}C$) in which $Fe_{14}Nd_2C$ can be obtained was wider than that of a cast alloy. An alloy made with the wheel speed of 20 or 30m/s yielded higher coercivities after heat treatment. In iron-rich Fe-Nd-C, the composition range in which a high coercivity (more than 10kOe) is expected is narrow, i.e., 77~78 Fe and 7~8 C(at.%).

• Korean Journal of Food Science and Technology
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• v.34 no.3
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• pp.498-504
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• 2002

Isoflavone (daidzein and genistein) contents, and antioxidative and fibrinolytic activities of seven commercial Korean cooking-with-rice soybeans, including Seonbikong, Chungtae, Gangnamkong, Whangtae, Geodoo, Seolitae, and Wooltalikong were investigated. Daidzein and genistein were not found in Selitae, nor was didzein in Gangnamkong and Geodoo. Total daidzein and genistein levels in Chungtae and Whangtae were 500 and 1550 mg per kg, respectively. Wooltalikong, Whangtae, and Gangnamkong had very high electron donation abilities, over 90%, but Seonbikong and Chungtae showed significantly lower activities. SOD-like activities were also the highest in Gangnamkong and Wooltalikong. Fibrinolytic activities in Seonbikong, Whangtae, and Gangnamkong were similarly strong. Fibrinolytic substances purified from protease inhibitors or activated under various pH or heat treatment conditions, were different among the soybean varieties. This study revealed that, although several cooking-with-rice soybeans were poor in isoflavones, Wooltalikong and Gangnamkong could be good sources for functional products due to their strong antioxidative activities, and heat- and acid-resistant proteolytic abilities.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.89-95
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• 2021

Research on the production of lithium hydroxide (LiOH) has been actively conducted in response to the increasing demand for high nickel-based positive electrode materials for lithium-ion batteries. Herein we studied the conversion of lithium oxide (Li2O) through thermal decomposition of lithium carbonate for the production of lithium hydroxide from lithium carbonate (Li2CO3). The reaction mechanism of lithium carbonate with alumina, quartz and graphite crucible during heat treatment was confirmed. When graphite crucible was used, complete lithium oxide powder was obtained. Based on the TG analysis results, reagent-grade lithium carbonate was heat-treated at 700℃, 900℃ and 1100℃ for various time and atmosphere conditions. XRD analysis showed the produced lithium oxide showed high crystallinity at 1100℃ for 1 hour in a nitrogen atmosphere. In addition, several reagent-grade lithium oxides were reacted at 100℃ to convert to lithium hydroxide. XRD analysis confirmed that lithium hydroxide (LiOH) and lithium hydroxide monohydrate (LiOH·H2O) were produced.

• Journal of Life Science
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• v.31 no.1
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• pp.47-51
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• 2021

In today's society, functional whitening cosmetics are important to beauty. Fungi are known to produce a variety of whitening-related metabolites. In this study, we searched for tyrosinase inhibitors with metabolic products derived from Trichoderma atroviride supernatant in order to apply a material for whitening functional cosmetics. In addition, the inhibitory effect was compared to arbutin, which has already been approved as a whitening raw material by the Korea Ministry of Food and Drug Safety (KMFDS). The metabolites from the T. atroviride supernatant showed higher tyrosinase inhibitory activity than that of arbutin. Some of the tyrosinase inhibitors were stable to heat, whereas some were unstable. The heat unstable material was exhibited in the case of samples treated with little amounts, such as 0.02~0.2%. They were very unstable in acidic and alkali pHs, especially under acidic conditions. However, it was found that a weakly-acidic to neutral pH range was the optimal working pH, especially neutral pH. Since the activity of the inhibitory substances in the T. atroviride supernatant was maintained regardless of proteinase K treatment, it was assumed that the metabolites, but not the bioactive peptides, were involved in the activity. In summary, we propose that the metabolites derived from T. atroviride supernatant have strong potential as whitening raw material.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.16-19
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• 2019

A thinner film has superior electrical properties and a better amorphous structure. Amorphous structures can be effective in improving conductivity through a depletion effect. Research is needed on the Schottky contact, where potential barriers are formed, as a way to identify these characteristics. $SiO_2/SnO_2$ thin films were prepared to examine the amorphous structure and Schottky contact, $SiO_2$ thin films were prepared using Ar = 20 sccm. $SnO_2$ thin films were deposited using mixed gas with a flow rate of argon and oxygen at 20 sccm, and $SnO_2$ thin films were added by magnetron sputtering and treated at $100^{\circ}C$ and $150^{\circ}C$. To identify the conditions under which the amorphous structure was constructed, the XRD patterns were investigated and C-V and I-V measurements were taken to make Al electrodes and perform electrical analysis. The depletion layer was formed by the recombination of electrons and holes through the heat treatment process. $SiO_2/SnO_2$ thin films confirmed that the pores were well formed when heat treated at $100^{\circ}C$ and an electric current was applied over the micro area. An amorphous $SiO_2/SnO_2$ thin film with heat treatment at $100^{\circ}C$ showed no reflection at $33^{\circ}\;2{\theta}$ in the XRD pattern, and a reflection at $44^{\circ}2\;{\theta}$. The macroscopic view (-30 V

• Journal of Life Science
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• v.19 no.7
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• pp.994-1002
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• 2009

A bacteriocin-producing bacterium identified as Bacillus licheniformis was isolated from soybean sauce. Antibacterial activity was confirmed by paper disc diffusion method, using Micrococcus luteus as a test organism. The bacteriocin also showed antibacterial activities against Bacillus sphaericus, Lactobacillus bulgaricus, Lactobacillus planiarum, Paenibacillus polymyxa, and Pediococcus dextrinicus. Optimal culture conditions for the production of bacteriocin was attained by growing the cells in an MRS medium at a pH of 6.5~ 7.0 and a temperature of 37$^\circ$C for 36$\sim$48 hr. Solvents such as chloroform, ethanol, acetone, and acetonitrile had little effect on bacteriocin activity. However, about 50% of bacteriocin activity diminished with treatment of methanol and isopropanol at the final concentration of 50% at 25$^\circ$C for 1 hr. It was stable against a pH variation range from 3.0 and 7.0, but the activity reduced to 50% at a pH range from 9.0 to 11.0. It's activity was not affected by heat treatment at 100$^\circ$C for 30 min and 50% of activity was retained after heat treatment at 100$^\circ$C for 60 min, showing high thermostability. The bacteriocin was purified to a homogeneity through ammonium sulfate precipitation, SP-Sepharose ion-exchange chromatography, and reverse-phase high-performance liquid chromatography (HPLC). The entire purification protocol led to a 75-fold increase in specific activity and a 13.5% yield of bacteriocin activity. The molecular weight of purified bacteriocin was estimated to be about 2.5 kDa by tricine-SDS-PAGE.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.407-417
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• 2020

The capacity of the designated landfill site for asbestos-containing waste is approaching its limit because the amount of asbestos-containing slate is increasing every year. There is a need for a method that can safely and inexpensively treat asbestos-containing slate in large capacity and at the same time recycle it. A cement kiln can be an alternative for heat treatment of asbestos-containing slate. We intend to develop a pilot scale device that can simulate the high temperature environment of a cement kiln using a high temperature plasma reactor in this study. In addition, this reactor can be used to inactivate asbestos in the slate and to synthesize one of the minerals of cement, to confirm the possibility of recycling as a cement raw material. The high-temperature plasma reactor as a pilot scale experimental apparatus was manufactured by downsizing to 1/50 the size of an actual cement kiln. The experimental conditions for the deactivation test of the asbestos-containing slate are the same as the firing time of the cement kiln, increasing the temperature to 200-2,000℃ at 100℃ intervals for 20 minutes. XRD, PLM, and TEM-EDS analyses were used to characterize mineralogical characteristics of the slate before and after treatment. It was confirmed that chrysotile [Mg3Si2O5(OH)4] and calcite (CaCO3) in the slate was transformed into forsterite (Mg2SiO4) and calcium silicate (Ca2SiO4), a cement constituent mineral, at 1,500℃ or higher. Therefore, this study may be suggested the economically and safely inactivating large capacity asbestos-containing slate using a cement kiln and the inactivated slate via heat treatment can be recycled as a cement raw material.

• Clean Technology
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• v.30 no.2
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• pp.134-144
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• 2024

In this study, the mechanical stability of red mud was improved for its commercial use as a catalyst to effectively decompose HFC-134a, one of the seven major greenhouse gases. Red mud is an industrial waste discharged from aluminum production, but it can be used for the decomposition of HFC-134a. Red mud can be manufactured into a catalyst via the crushing-preparative-compression molding-firing process, and it is possible to improve the catalyst performance and secure mechanical stability through calcination. In order to determine the optimal heat treatment conditions, pellet-shaped compressed red mud samples were calcined at 300, 600, 800 ℃ using a muffle furnace for 5 hours. The mechanical stability was confirmed by the weight loss rate before and after ultra-sonication after the catalyst was immersed in distilled water. The catalyst calcined at 800 ℃ (RM 800) was found to have the best mechanical stability as well as the most catalytic activity. The catalyst performance and durability tests that were performed for 100 hours using the RM 800 catalyst showed thatmore than 99% of 1 mol% HFC-134a was degraded at 650 ℃, and no degradation in catalytic activity was observed. XRD analysis showed tri-calcium aluminate and gehlenite crystalline phases, which enhance mechanical strength and catalytic activity due to the interaction of Ca, Si, and Al after heat treatment at 800 ℃. SEM/EDS analysis of the durability tested catalysts showed no losses in active substances or shape changes due to HFC-134a abasement. Through this research, it is expected that red mud can be commercialized as a catalyst for waste refrigerant treatment due to its high economic feasibility, high decomposition efficiency and mechanical stability.