• Journal of the Korean Society of Combustion
• /
• v.18 no.4
• /
• pp.29-36
• /
• 2013

Numerical study was conducted to clarify effects of added $CO_2$ for the downstream interaction between $H_2$-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced. The most discernible difference between the two with and without having $CO_2$ addition into $H_2$-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of $H_2$, in which $H_2$-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route $CO+O_2{\rightarrow}CO_2+O$ with a very long chemical time in CO-air flame to the (H, O, OH)-related reaction routes including $CO+OH{\rightarrow}CO_2+H$ with relatively short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added $CO_2$ suppressed flame stabilization. Particularly this phenomenon was appreciable at flame conditions which lean and rich extinction boundary was merged. The detailed discussion of chemical effects of added $CO_2$ was addressed to the present downstream interaction.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.217-220
• /
• 2009

Conductive adhesives have been investigated for use in microelectronics packaging as a lead-free solder substitute due to their advantages, such as low bonding temperature. However, high resistivity and poor mechanical behavior may be the limiting factors for the development of conductive adhesives. The metal fillers and the polymer resins provide electrical and mechanical interconnections between surface mount device components and a substrate. As metal fillers used in conductive adhesives, silver is the most commonly used due to its high conductivity and the stability. However the cost of conductive adhesives with silver fillers is much higher than usual lead-free solders and silver has poor electro-migration performance. So, copper can be a promising candidate for conductive filler metal due to its low resistivity and low cost, but oxidation causes this metal to lose its conductivity. In this study, electrically conductive adhesives (ECAs) using surface modified copper fillers were developed. Especially, in order to overcome the problem associated with the oxidation of copper, copper particles were coated with silver, and the silver-coated copper was tested as a filler metal. Especially the effect of silver coating on the electrical resistance just after curing and after aging was investigated. As a result, it was found that the electrical resistance of ECA with silver-coated copper filler was clearly lower and more stable than that of ECA with pure copper filler after curing process. And, during high temperature storage test, the degradation rate of electrical resistance for ECA with silver coated copper filler was quite slower than that for ECA with pure copper filler.

• Applied Chemistry for Engineering
• /
• v.30 no.1
• /
• pp.43-48
• /
• 2019

This study investigated the feasibility of $CaSnO_3$ particles as an oxygen carrier in chemical looping combustion (CLC). $CaSnO_3$ particles had a perovskite crystal structure and showed the structural stability after repeated reduction-oxidation reactions. The oxygen transfer capacity was 15.4 wt% almost the same as the calculated theoretical value from the crystal structure transformation during reduction. After $10^{th}$ cycles of reduction and oxidation, the oxygen transfer capacity and rate were still maintained constantly at an operating temperature. In conclusion, $CaSnO_3$ particles could be a good alternative material as an oxygen carrier in CLC.

• Food Science and Preservation
• /
• v.8 no.3
• /
• pp.338-344
• /
• 2001

The oxidative stability of cholesterol in tallow heated at different frying temperatures (130$\^{C}$, 150$\^{C}$, and 180$\^{C}$) was studied by identifying cholesterol oxides by thin layer chromatography(TLC). And fatty acid compositions in tallow heated were also measured and compared with cholesterol oxides. Unsaturated fatty acid contents slightly decreased as the heating time increased, whereas saturated fatty acid contents increased This phenomenon became excessive especially by heating to higher temperature. It was found that RF value and spot color of the nonsaponifiable lipids from tallow heated on TLC analysis accorded with the synthetic cholesterol oxides in this experiment. Four kinds of cholesterol oxides were detected in tallow heated for 24 hours at three different temperatures. The oxides were identified as 7-$\alpha$-hydroxycholesterol, 7-$\beta$-hydroxycholesterol, 7-ketocholesterol and cholesterol epoxide. It was found that there was a little difference in oxidative pattern of cholesterol between several heating temperatures.

• Membrane Journal
• /
• v.32 no.3
• /
• pp.181-190
• /
• 2022

Membrane separation provides various advantages including cost effectiveness and high efficiency over traditional wastewater treatment methods such as flocculation and adsorption. However, the effectiveness of membrane separation greatly declines due to membrane fouling, where pollutants are accumulated on the membrane surface. Among different groups of membranes, ceramic membranes can provide good antifouling properties due to its hydrophilicity and chemical stability. In addition, composite membranes such as graphene oxide modified membranes can help prevent membrane fouling. Recently, hybrid photocatalytic membranes have been proposed as a solution to prevent membrane fouling and provide synergetic effects. Membrane separation can solve the disadvantages of photocatalytic oxidation such as low reutilization rate, while photocatalytic oxidation can help reduce membrane fouling.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.19 no.5
• /
• pp.436-445
• /
• 1986

As the second part of the studies on the utilization of polyunsaturated lipids in sardine oil as nutritional or medical supplement, the conditions of lipid extration and concentration, refining, and storage stability of EPA-condensed sardine oil were investigated. In extraction of lipids, solvent ratios of chloroform-methanol mixture(2:1 v/v) affected the final content of unsaturated lipid in extracted oil and recovery. Stepwise solvent fractionation method at various low temperatures was effective to concentrate polyenoic acids like EPA and DHA when acetone or acetone-methanol mixture, added in the ratio of 1:5 (v/v) was applied step by step to different temperatures at 0 to $-35^{\circ}C$. Addition of 1 to $5\%$ (v/v) of water to acetone was also benefit to raise EPA content but that resulted in reducing the yield of condensed oil from $65\%\;to\;28\%$. Concentration rate of polyenoic acids by solvent fractionation in lipid-actone solution (1:5, v/v) at 0 to $-30^{\circ}C$ seemed limited to $5{\sim}8\%$ in fatty acid composition depending on the initial content of those polyenoic acids in the sardine oil. During the extraction, concentration, and alkaline treatment, oxidation was rapidly induced but oxidation products could be thoroughly removed on the process of deceleration and peroxide elimination. To stabilize the reactive polyenoic acid condensed oil during the storage, stuffing nitrogen gas was essential to expel dissolved oxygen in oil or to seal the oil from open air, and the addition of antioxidative agents as BHA and tocopherols were greatly helpful to extend the storage life.

• Journal of Life Science
• /
• v.20 no.12
• /
• pp.1777-1783
• /
• 2010

Plants generate reactive oxygen species (ROS) as a by-product of normal aerobic metabolism or when exposed to a variety of stress conditions, which can cause widespread damage to biological macromolecules. To protect themselves from oxidative stress, plant cells are equipped with a wide range of antioxidant proteins. However, the detailed reaction mechanisms of these are still unknown. Peroxiredoxins (Prxs) are ubiquitous thiol-containing antioxidants that reduce hydrogen peroxide with an N-terminal cysteine. The active-site cysteine of peroxiredoxins is selectively oxidized to cysteine sulfinic acid during catalysis, which leads to inactivation of peroxidase activity. This oxidation was thought to be irreversible. Recently identified small protein sulphiredoxin (Srx1), which is conserved in higher eukaryotes, reduces cysteine.sulphinic acid in yeast peroxiredoxin. Srx1 is highly induced by $H_2O_2$-treatment and the deletion of its gene causes decreased yeast tolerance to $H_2O_2$, which suggest its involvement in the metabolism of oxidants. Moreover, Srx1 is required for heat shock and oxidative stress induced functional, as well as conformational switch of yeast cytosolic peroxiredoxins. This change enhances protein stability and peroxidase activity, indicating that Srx1 plays a crucial role in peroxiredoxin stability and its regulation mechanism. Thus, the understanding of the molecular basis of Srx1 and its regulation is critical for revealing the mechanism of peroxiredoxin action. We postulate here that Srx1 is involved in dealing with oxidative stress via controlling peroxiredoxin recycling in Arabidopsis. This review article thus will be describing the functions of Prxs and Srx in Arabidopsis thaliana. There will be a special focus on the possible role of Srx1 in interacting with and reducing hyperoxidized Cys-sulphenic acid of Prxs.

• Korean Journal of Plant Resources
• /
• v.26 no.5
• /
• pp.628-635
• /
• 2013

In order to evaluate their potential as sources of biodiesel, oil content and fatty acid composition of seeds and fatty acid methyl ester (FAME) properties from seven woody oil plants in Korea were analysed. The oil content of seed of all woody plant species ranged from 15.1 (Ligustrum lucidum) to 70.3% (Camellia japonica) by dry weight. Fatty acid composition consisted mainly of oleic acid, linoleic acid, linolenic acid, palmitic acid and stearic acid, with oleic acid being the most abundant. The content of unsaturated fatty acids of all species was higher than saturated fatty acids. Oxidation stability of seed oils of all woody plants ranged from 2.25 to 8.62 hours/$110^{\circ}C$. Fatty acid methyl ester of Styrax japonica has been found to have the highest iodine value, indicating that unsaturated fatty acid content is higher than other seed oils. Cold filter plug point(CFPP) was varied over a wide range from $0^{\circ}C$ to $-13^{\circ}C$. The cold fluidity of FAME of Chionanthus retusa were excellent.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.4
• /
• pp.423-429
• /
• 2008

Application of manganese-impregnated activated carbon(Mn-AC) in the treatment of synthetic wastewater containing both organic and inorganic contaminants was investigated. Phenol and As(III) was used as representative organic and inorganic contaminants, respectively. When the stability of Mn-AC at acidic condition was evaluated with variation of solution pH ranging from 2 to 4, Mn-AC was unstable below pH 3, while negligible dissolution of Mn was observed above pH 4. This stability test suggests a plausible applicability of Mn-AC in the treatment of wastewater above pH 4. Compared to AC-alone, the adsorption rates of phenol as well as adsorbed amounts of phenol by Mn-AC were slightly decreased due to the decrease of the surface area by impregnation. The maximum adsorbed amount of phenol by Mn-AC was corresponds to 75% of that by AC-alone from the adsorption isotherm study. The oxidation efficiency of As(III) by Mn-AC was greater than that by AC-alone at lower pHs while reverse trend was observed as pH increased above 7. From this work, it was found that Mn-AC could be used in the simultaneous treatment of both phenol and As(III).

• Korean journal of food and cookery science
• /
• v.9 no.1
• /
• pp.33-36
• /
• 1993

This study was carried out to investigate the thermal stability of gingerol from Ginger and effect of its concentration on the oxidation of soybean oil. After Heating gingerol, the contents of remained gingerol was measured by HPLC. After heat treatment at $105^{\circ}C$ for 3 hours, 94.5% of gingerol was remained, whereas at $165^{\circ}C$ for 30 min., only 10% of gingerol was remained. Crude gingerol was also added to soybean oil at the concentration of 0.02%, 0.1% and 0.2% by weight of oil, respectively. The oils with crude gingerol were heat-treated at $105^{\circ}C$ for 5 hours and $165^{\circ}C$ for 30 minutes, respectively, and then the heat-treated oils were incubated at $45^{\circ}C$ for 25 days. The peroxide value of the oils was measured in order to estimate the antioxidant activity of crude gingerol compared with BHT. In the soybean oil heated at $105^{\circ}C$ for 5 hours, crude gingerol showed antioxidant activity at all concentration and the activity was more effective than 0.02% BHT. And during the storage of the heat-treated oils at $45^{\circ}C$, the antioxidant activity of crude gingerol increased in direct proportion to its concentration. In the soybean oil heated at $165^{\circ}C$ for 30 minutes and then stored at $45^{\circ}C$, the antioxidant activity of crude gingerol increased in direct proportion to its concentration.